Microplastics in the Environment: Fate, Impacts, Removal, and Management 9781394251070

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Microplastics in the Environment

Microplastics in the Environment Fate, Impacts, Removal, and Management

Edited by

Rao Y. Surampalli Tian C. Zhang Bashir M. Al-Hashimi Chih-Ming Kao Makarand M. Ghangrekar Puspendu Bhunia Sovik Das

This edition first published 2025 © 2025 John Wiley & Sons Ltd All rights reserved, including rights for text and data mining and training of artificial intelligence technologies or similar technologies. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. The right of Rao Y. Surampalli, Tian C. Zhang, Bashir M. Al-Hashimi, Chih-Ming Kao, Makarand M. Ghangrekar, Puspendu Bhunia, and Sovik Das to be identified as the authors of the editorial material in this work has been asserted in accordance with law. Registered Offices John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA John Wiley & Sons Ltd, New Era House, 8 Oldlands Way, Bognor Regis, West Sussex, PO22 9NQ, UK For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com. Wiley also publishes its books in a variety of electronic formats and by print-on-demand. Some content that appears in standard print versions of this book may not be available in other formats. Trademarks: Wiley and the Wiley logo are trademarks or registered trademarks of John Wiley & Sons, Inc. and/or its affiliates in the United States and other countries and may not be used without written permission. All other trademarks are the property of their respective owners. John Wiley & Sons, Inc. is not associated with any product or vendor mentioned in this book. Limit of Liability/Disclaimer of Warranty While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Library of Congress Cataloging-in-Publication Data Applied for: Hardback ISBN: 9781394251070 Cover Design: Wiley Cover Image: Courtesy of Dr Sovik Das Set in 9.5/12.5pt STIXTwoText by Straive, Pondicherry, India

v

Contents Preface xvii Notes on Editors

Section I 1

1.1 1.2 1.3 1.4 1.5 1.6

2

2.1 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.3 2.3.1 2.3.2 2.4 2.4.1 2.4.2 2.4.3

xix

The Existence and Characterization of Microplastics

1

Introduction and Book Overview 3 Yasser Bashir, Nehaun Zargar, Neha Sharma, Almeenu Rasheed, Sovik Das, Makarand M. Ghangrekar, Puspendu Bhunia, Bashir M. Al-Hashimi, Rao Y. Surampalli, Tian C. Zhang, and Chih-Ming Kao Background and Definition 3 Impacts of MPs on the Environment, Society, and Economics 7 Solutions, Knowledge Gaps, and Challenges 9 Policies and Practices to Regulate MPs 10 Book Structure and Overview of Chapters 11 Conclusion 12 References 13 Classifications and Physiochemical Properties of Microplastics 17 Sudeep Kumar Mishra, Sanket Dey Chowdhury, Puspendu Bhunia, Arindam Sarkar, Rao Y. Surampalli, and Tian C. Zhang Introduction 17 Structural Properties 21 Crystallinity 21 Particle Size 23 Surface Morphology 25 Intra- and Interparticular Interactions 27 Physical Properties 28 Density and Specific Gravity 28 Specific Surface Area 30 Chemical Properties 31 Hydrophobicity 31 Solubility 31 Chemical Composition 32

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33

2.5 2.6

Thermal Stability Conclusion 34 References 35

3

Degradation of Plastics and Formation of Primary and Secondary Microplastics 43 Sudeep Kumar Mishra, Sanket Dey Chowdhury, Puspendu Bhunia, Arindam Sarkar, Rao Y. Surampalli, and Tian C. Zhang Introduction 43 Physical and Mechanical Degradation 46 Photodegradation of Plastics 46 Thermal Degradation of Plastics 49 Mechanical Degradation of Plastics 49 Chemical Degradation 50 Biological Degradation 51 Degradation Pathway 54 Degradation Products and Byproducts 58 Toxicity of Products and Byproducts 59 Conclusion 61 References 61

3.1 3.2 3.2.1 3.2.2 3.2.3 3.3 3.4 3.5 3.6 3.7 3.8

4

4.1 4.2 4.2.1 4.2.2 4.2.3 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.4 4.5 4.6 4.7

5

5.1 5.1.1

Advanced Techniques for Sampling, Quantification, and Characterization of Microplastics 69 Chathura Dhanasinghe, Chih-Ming Kao, Pu-Fong Liu, Rao Y. Surampalli, Tian C. Zhang, and Bashir M. Al-Hashimi Screening 69 Sampling and Extraction 71 Surface 72 Aquatic Samples 78 Dust/Sediment/Tissues 81 Characterization for Size, Shape, and Chemical Composition 84 Filtration/Density Separation 85 Visual Inspection 85 Optical Analytical Methods 86 Thermal Analysis 87 Quantification 88 Harmonizing Approaches and Valuable Minimal Technical Criteria and Specification 90 Quality Assurance/Quality Control 95 Conclusion 97 References 98 Technologies for Polymer Identification and Monitoring of Microplastics Distribution 107 Akhil Gupta and Pratik Kumar Introduction 107 Fourier Transform Infrared Spectroscopy 108

Contents

5.1.2 5.1.3 5.1.4 5.1.5 5.1.6 5.1.7 5.2 5.2.1 5.2.2 5.2.3 5.3 5.3.1 5.3.1.1 5.3.1.2 5.3.2 5.4 5.5 5.5.1 5.5.1.1 5.5.1.2 5.5.2 5.5.3 5.5.3.1 5.5.3.2 5.5.4 5.5.4.1 5.6 5.6.1 5.6.2 5.6.3 5.6.4 5.7

6 6.1 6.2 6.2.1 6.2.2 6.3 6.4

Raman Spectroscopy 109 Scanning Electron Microscopy/Energy-Dispersive X-Ray Spectrometry 110 Pyrolysis Gas Chromatography/Mass Spectroscopy 110 Rapid Screening/Fluorescent Microscopy, High Throughput Analysis of Microplastics 111 Solid–Liquid–Liquid Microextraction Technique 111 Elemental Analyzer/Isotope Ratio Mass Spectrometry 111 Instrumentational Methods to Study Microplastics in Different Matrices 112 Water Samples 113 Sediment Samples 113 Biological Samples 115 Technologies for Measuring Nano-Microplastics and Determining the Relative Contributions of Particles of Varying Size, Shape and Chemical Composition 115 Quantifying the Micro Menace: Measuring Microplastics 115 Shape Matters: Unveiling Morphology 116 Demystifying the Material: Identifying Chemical Composition 116 Challenges and Emerging Solutions 117 Distribution and Monitoring of Microplastics 117 Review of Existing Monitoring Programs for Marine Microplastics 119 Aerial Monitoring of Plastic Pollution in the Marine Environment 121 The Role of Vertical Mixing on the Global Distribution of Microplastic 121 The Role of Bioturbation in Distributing Secondary Microplastics in Marine Sediments 122 Thermo Degradation Method to Assess the Distribution of Microplastics in Marine Sediments 123 Microplastic Dispersal from Point Sources in the Sea Region 125 Primary Sources 126 Secondary Sources 126 Spatio-Temporal Monitoring of Coastal Marine Plastics 126 Surveillance of Seafood for Microplastics 127 Other Techniques for Monitoring 127 Remote Sensing and GIS-Based Monitoring 127 SCADA-Based Monitoring 128 GIS Coupled with 3D Modeling 129 Future Applications of GIS 129 Conclusions 130 References 130 Characterizing Microplastics in the Context of Risk Assessment 135 Akash Tripathi, Makarand M. Ghangrekar, and Rao Y. Surampalli Introduction 135 The TK/TD of MPs in a Representative Organism 136 Particle Translocation Within Organisms 138 Exposure to and Bioaccumulation of Additive Chemicals 140 Determining the Particle Size Range Where Any Toxicity Resides 142 Identifying Potential Uncertainties and Concerns 144

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145

6.5 6.6

Determining Relative Levels of Confidence Regarding Toxicological Data Conclusion 148 References 148

7

Understanding Environmental and Socio-economic Risks Associated with Microplastics 153 Azhan Ahmad, Monali Priyadarshini, Makarand M. Ghangrekar, and Rao Y. Surampalli Background 153 Economic Impacts 154 Social Impacts 155 Environmental Sensitivity and Variability of Microplastic 157 Toxicological Impact of Microplastics on Aquatic Organisms 159 Strategies for Managing Microplastic in the Environment 161 Conclusion and Way-forward 162 References 163

7.1 7.2 7.3 7.4 7.5 7.6 7.7

Section II

8

8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.9.1 8.9.2 8.9.3 8.9.4 8.10

9

9.1 9.2 9.2.1 9.2.2

Microplastics in Different Compartments and their Effects on Environments and Humane Society 167

Microplastics in the Environment: Sources, Distribution, Fate, and Transport 169 Hua-Bin Zhong, Ying-Liang Yu, Chih-Ming Kao, Rao Y. Surampalli, Tian C. Zhang, and Bashir M. Al-Hashimi MPs in the Aquatic Environment (Surface/Ground Waters and Ocean) 169 MPs in the Terrestrial Environment (Soil and Sediment) 171 MPs in the Polar Region 173 MPs in the Atmospheric Environment and Transboundary Transport 175 MPs in Food and Agricultural Crops 179 MPs Associated with the Construction Industry 180 MPs in Urban Environmental Management Systems 183 Contaminants Released from Aged MPs 186 Fate/Transport and Behavior of MPs in Pollution Control Systems 188 In Water and WWTPs 188 In Combined Stormwater and Sewer Overflows 189 In Sewage Sludge and Landfill Leachate 191 In Systems for Recycling and Remediation of MPs 194 Conclusion 200 References 200 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments 207 Mahima John Horta, Yerramilli Sai Rama Krishna, N. Seetha, and Pritha Chatterjee Introduction 207 Transport Mechanisms of Microplastics in the Environment 210 Degradation 210 Beaching 212

Contents

9.2.3 9.2.4 9.2.5 9.2.6 9.2.7 9.3 9.4 9.5 9.6 9.7

Drifting 212 Dispersion 213 Flocculation 213 Sedimentation 214 Biofouling 214 Modeling the Fate and Transport of Microplastics in Riverine Environment 215 Modeling the Fate and Transport of Microplastics in Estuaries 226 Modeling the Fate and Transport of Microplastics in Marine Environment 231 Modeling the Fate and Transport of Microplastics in the Subsurface 236 Conclusions 243 Acknowledgments 243 Nomenclature 244 References 247

10

Ecological Impacts of Microplastics and Their Additives: Exposure Risk/Toxicity Assessment and Fate/Transport of Persistent, Bio-Accumulative and Toxic Substances 259 Qamaruz Zaman Khaki and Pratik Kumar Introduction 259 Creating Standardized Toxicity Tests for MPs 260 Particle Characterization 260 Experimental Design 261 Applicability for Risk Assessment 262 The Ecological Representative Organisms/Test Systems/MPs 262 What Do Microplastics Do in Different Cell Types? 263 Using Polydisperse, Environmentally Relevant Distributions of Microplastic Particles 264 Extrapolating In Vitro Results to In Vivo Effects 264 Dose–Response Analysis and Formulation of Standards 264 Acute and Chronic Toxicity of Microplastics 265 Carcinogenic 265 Noncarcinogenic 265 Chemical Risk Posed by Ingested Microplastics 265 Development of Health-Based Threshold 266 Effects of Exposure: Microplastics Transferred to the Consumers 266 Bioaccumulation/Biomagnification/Bioavailability 268 Are Microplastics Vectors (for Organisms or Chemical Pollutants in the Environment)? – Sorption of Potentially Toxic Pollutants on Microplastics 269 Connect Microplastics to Existing or Novel Adverse Outcome Pathways 269 The Relevant Receptors 271 Exposure Pathways 272 Exposure Pathway to MP Via Ingestion 273 Exposure Pathway to MP Via Inhalation 273 Exposure Pathway to MP Via Dermal Contact 273 Toxicokinetic/Dynamic Processes 274

10.1 10.2

10.2.1 10.2.2 10.2.3 10.2.4 10.3 10.4 10.4.1 10.4.2 10.5 10.6 10.7 10.7.1 10.8 10.9 10.10 10.11 10.12 10.13 10.14 10.15

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MPs Plus Chemicals/Nanomaterials/Pathogens Attached/Sorbed on them – Ecological Effects of Chemical Contaminants Adsorbed to Microplastics 274 10.17 Interrelationships Among Different Factors 276 10.18 Interaction of Microplastics with PBTs and Other Emerging Contaminants 276 10.18.1 Changes in Relative Risk of PBTs Sorbed to or Present in Microplastics 277 10.18.2 Changes in Relative Risk of ECs Sorbed to or Present in Microplastics 277 10.19 Conclusion 277 References 278 10.16

11

11.1 11.2 11.2.1 11.2.2 11.2.3 11.2.4 11.2.5 11.2.6 11.2.7 11.3 11.3.1 11.3.2 11.4 11.5 11.6 11.7 11.8 11.9 11.10 11.11

12

12.1 12.2 12.3 12.4 12.5 12.6 12.6.1

Interactions of Microplastics with Microbial Communities and the Food Web/Plants 283 Santosh Kumar, Akash Tripathi, Shraddha Yadhav, Srishti Mishra, and Makarand M. Ghangrekar Introduction 283 Interactions of MPs with Natural Organic Materials, Crops, and Plants 285 Transport and Accumulation of MPs in Different Parts of the Plant 285 Exposure of Soil and Food Crops to Diverse Agricultural Plastics 286 Impacts of MP on Crop or Plant Reproduction and Growth 287 MP Contamination from Soil Mulching 288 MPs from Drip Tape Irrigation 289 Seed Casings/Row Covers for Frost Protection/Plant Trays and Bags 290 Use of Polymeric Materials for Slow Release of Agrochemicals to Crops 290 Interaction Between Microbial Community and MPs 291 Changes in Microbial Dynamics and Biota due to MPs 291 Role of Microorganisms in Eco-Remediation 293 Effect of MPs on Metabolic Activities of the Organisms 295 Leaching of MPs from Dumpsites to Soil 295 MPs from Silage Film for Storage of Silage 296 Change in the Geo-chemical Properties of Soil due to MPs 296 Effect of MPs on the Food Web and Food Chain 297 Are Biodegradable Plastics Less Negative Than the Others? 298 Biostimulation by Nutrients 299 Conclusion 300 References 300 Environmental and Toxicological Effects of Microplastics on Aquatic Ecosystems 311 Jin-Min Li, Hua-Bin Zhong, Chih-Ming Kao, Rao Y. Surampalli, and Tian C. Zhang Background 311 Sources of MPs in Aquatic Environments 312 Consumption of MPs by Aquatic Organisms and Increase in Aquatic Leaching Rate 316 Transport of MPs in the Aquatic Trophic Level 317 Occurrence of MPs in Aquatic Ecosystems 318 Effects of MPs on Freshwater Ecosystems 321 Effects/Ecotoxicity of MPs in Freshwater Biota (Micro and Macro Organisms) 322

Contents

12.6.2 12.7 12.7.1 12.7.2 12.7.3 12.7.4 12.7.5 12.8 12.9

Effects on Different Developmental Stages of Invertebrates 324 Effects of MPs in Marine Ecosystems 325 Contamination of Seawater 325 Effects on Seabed Sediments 327 Implications of Plastic Adhesion to Corals Surface 329 Effects/Ecotoxicity of MPs in Marine Biota (Micro- and Macroorganisms) Effects on Different Developmental Stages of Invertebrates 333 Increase in Toxicity and Impacts on Biodiversity 334 Conclusions 336 References 336

13

Human Exposures to Microplastics: Impact of Different Routes 347 Sanket Dey Chowdhury, Sudeep Kumar Mishra, Puspendu Bhunia, Rao Y. Surampalli, and Tian C. Zhang Introduction 347 Pathways of Human Exposure to Microplastics 349 Ingestion 349 Inhalation 352 Dermal Contact 354 Toxic Effects of Microplastics on Human Beings 356 Oxidative Stress and Cytotoxicity 356 Disruption of Energy Homeostasis and Metabolic Disorder 357 Migration of Microplastics to the Circulatory System and Remote Tissues 358 Neurotoxicity 359 Destruction of Immune Function 360 Reproductive and Developmental Toxicity 361 Microplastics as Vectors of Microorganisms and Toxic Chemicals 361 Use of Biomarkers to Elucidate Microplastic Toxicity 362 Antioxidant Enzymes 362 Lipid Peroxidation 363 Deoxyribonucleic Acid Strand Breaks and Frequency of Micronuclei 364 Acetylcholinesterase Enzymes 364 IDH and Lactate Dehydrogenase Enzymes 365 Case Studies on Human Exposure 366 Conclusions 368 References 368

13.1 13.2 13.2.1 13.2.2 13.2.3 13.3 13.3.1 13.3.2 13.3.3 13.3.4 13.3.5 13.3.6 13.3.7 13.4 13.4.1 13.4.2 13.4.3 13.4.4 13.4.5 13.5 13.6

Section III 14 14.1 14.2 14.2.1 14.2.2

Removal, Control, and Management of Microplastics

330

383

Plastic Pollution Management—Innovative Solutions for Plastic Waste 385 Saikat Sinha Ray, Randeep Singh, Mahesh Ganesapillai, and Young-Ho Ahn Introduction 385 Design and Production 390 Using Different Synthetic Materials 391 Simplified Design of Products 392

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Contents

Using Biodegradable Plastic 393 Packaging and Distribution 394 Reduction of Single-Use Plastic Packaging 394 Bans of Some Plastic Items 395 Better Labeling of Cosmetic and Cleaning Products 397 Plastic Types and Their Recycling Codes 397 Advantages of Labeling Plastics 397 Disadvantages of Labeling Errors on Efficient Recycling 398 Optimal Approaches to Plastic Labeling 398 Accurate Identification of Plastic Types 398 Adoption of Standard Labeling Practices 398 Clarity and Uniformity in Plastic Item Labeling 398 More Reuse of Plastics 398 Increased Reparability/Longevity of Products 400 Use and Maintenance 401 Disposal 402 Recycling (Primary Quaternary) of Plastics and Developing More Recycling Systems 403 14.4.2 Recovery/Cleanup 404 14.4.2.1 Developing Advanced Tertiary Technologies 404 14.4.2.2 Capture of Microplastics from Sports Fields and Playgrounds 406 14.5 System-based Approaches 407 14.5.1 Extended Producer Responsibility 407 14.5.2 Economy Approaches from Design to End-of-Life 408 14.5.3 Adding “Plastic Tax” to Make Any Plastic Product More Expensive 409 14.5.4 Education and Better Consumer Decisions 409 14.6 Conclusion 410 References 411 14.2.3 14.3 14.3.1 14.3.2 14.3.3 14.3.3.1 14.3.3.2 14.3.3.3 14.3.3.4 14.3.3.5 14.3.3.6 14.3.3.7 14.3.3.8 14.3.3.9 14.3.4 14.4 14.4.1

15 15.1 15.2 15.2.1 15.3 15.3.1 15.3.2 15.3.3 15.3.4 15.3.4.1 15.3.4.2 15.3.4.3 15.3.4.4 15.3.4.5 15.3.5 15.4 15.4.1

Preventing Secondary Sources of Microplastics in the Environment 417 Zaid Mushtaq Bhat, Asif Farooq, Mavra Farooq, Mariha Feroz, and Khalid Muzamil Gani Introduction 417 Reducing Usage of Plastics 418 Global Awareness and Incentives to Prevent Disposal of Plastics 418 Recycle and Reuse of Microplastics 419 Incentives to Recycle and Reuse Microplastics 419 Change in Lifestyle 420 Production Processes and Recycling 420 Development of Techniques for Recovery of Microplastics 422 Density Separation 422 Pressurized Fluid Extraction 422 Electrostatic Separation 422 Magnetic Separation 422 Ferrofluid-based Separation 423 Recycling Plastic Wastes to Minimize Microplastic Pollution Load 423 Chemical Upcycling of Polymers 424 Polymer to Polymer Approach 424

Contents

Polymer to Molecule Approach 424 Polymer to Material Approach 425 Upcycling of Mixed Plastics 425 Thermal Upcycling of Mixed Plastics 426 Biological Upcycling of Mixed Plastics 426 Composite Approach of Mixed Plastics 426 Polymer Construction and Deconstruction 427 Sustainable Polymer Construction for Microplastic Mitigation 427 Strategies for Microplastic Remediation through Polymer Deconstruction Cleaning of Plastic Waste from Environment 428 Management Strategies 428 Protection of Aquifers from Micro and Nanoplastic Contamination 429 Proper Monitoring of Plastic Waste 430 Management of Microplastic Waste Inputs to Terrestrial and Aquatic Ecosystems 431 15.7.1.1 Management Strategies 431 15.7.1.2 Upstream Solutions 432 15.7.1.3 Downstream Solutions 433 15.8 Different Multiple Thresholds the Tiered Framework 434 15.8.1 Tiered Framework for Microplastics Concerns 434 15.8.2 Drinking Water Management Thresholds in California 435 15.9 Conclusion 435 15.10 Future Perspective 436 References 436 15.4.2 15.4.3 15.4.4 15.4.5 15.4.6 15.4.7 15.5 15.5.1 15.5.2 15.6 15.6.1 15.6.2 15.7 15.7.1

16

16.1 16.2 16.2.1 16.2.2 16.2.3 16.3 16.3.1 16.3.2 16.3.3 16.3.4 16.4 16.5

17

17.1 17.2

428

Reducing and Eliminating Plastic Waste via Societal Changes 447 Pu-Fong Liu, Chathura Dhanasinghe, Ying-Liang Yu, Chih-Ming Kao, Rao Y. Surampalli, and Tian C. Zhang Introduction 447 The Importance of Consumer Culture and Behavior 448 What Are the Critical Societal Challenges in Reducing the Plastic Usage? 449 What Are the Potential Solutions? 450 How Might the Solutions Vary Regionally and Globally? 451 Reduction, Substitution, and Control of Microplastics From Human Usage 453 Redevelopment of Some Products 454 Substitution Using Eco-friendly Materials 456 Education and Awareness 458 Change in Lifestyle 462 Future Directions 464 Conclusion 465 References 465 Technologies for Removal and Remediation of Microplastics 469 Sanket Dey Chowdhury, Sudeep Kumar Mishra, Puspendu Bhunia, Rao Y. Surampalli, and Tian C. Zhang Introduction 469 Microplastic Remediation Technologies 470

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17.2.1 17.2.1.1 17.2.1.2 17.2.1.3 17.2.1.4 17.2.2 17.2.2.1 17.2.2.2 17.2.3 17.2.3.1 17.2.3.2 17.2.3.3 17.2.4 17.2.4.1 17.2.4.2 17.2.4.3 17.2.4.4 17.2.4.5 17.2.4.6 17.2.4.7 17.3

Physical Technologies 471 Filtration and Membrane Separation 471 Adsorption 503 Density Separation 505 Magnetic Separation 507 Chemical Technologies 508 Coagulation and Agglomeration 508 Advanced Oxidation Processes 513 Biological Technologies 517 Biodegradation 517 Ingestion by Marine Organisms 520 Bioflocculation 521 Hybrid Technologies 521 Membrane Bioreactor 522 Electrocoagulation 523 Electro-Fenton Process 525 Microbially Driven Fenton Process 525 Constructed Wetlands 526 Vermifiltration 528 Other Hybrid Technologies 529 Conclusions 530 References 532

18

Catalysis for the Upcycling of Polymers 545 Debanjali Dey, Manisha Sain, Zahoor Manzoor, and Shamik Chowdhury Introduction 545 Considerations for Substrates and Characterization 547 Application of Bio-Based Catalysts 549 Application of Electrocatalysts 550 Application of Chemical Catalysts 553 Conclusion 555 References 555

18.1 18.2 18.3 18.4 18.5 18.6

19 19.1 19.2 19.2.1 19.2.2 19.2.3 19.2.4 19.2.5 19.2.6 19.3 19.4

Biodegradable Bioplastics 559 Neha Sharma, Koran Barman, Nehaun Zargar, Almeenu Rasheed, and Sovik Das Production of Bioplastics 559 Standards and Guidelines to Test the Biodegradability of Bioplastics 561 Biodegradation in Aerobic Soil Environment 561 Biodegradation in Freshwater Environment 561 Biodegradation in the Marine Environment 562 Biodegradation During Composting 562 Biodegradation in Anaerobic Digestion 562 Biodegradation in Aerobic Landfill 562 Application of Bioplastics 563 Limitations of Bioplastic 564

Contents

19.5 19.5.1 19.5.2 19.6 19.7 19.8

Environmental Sustainability of Bioplastics 566 Degradation Pathways of Bioplastic 566 LCA of Biodegradable Bioplastic 567 Economic Assessment of Bioplastics 569 Comparison of Bioplastic with Polymer-Based Plastic Conclusion and Future Perspectives 571 References 572

20

Global Strategies/Policies and Citizen Science for Microplastic Management 577 Jin-Min Li, Ming-Fang Yu, Chih-Ming Kao, Rao Y. Surampalli, and Tian C. Zhang Guidelines for Pollutant Control at Source 577 Enforcement of Legislative Measures 580 Existing Regulations and Acts in Global Scenarios 583 Microplastics and the UN Sustainable Development Goals 584 Public Perception and Participation 587 Education and Public Engagement 589 Community Analysis-Based Models 591 Conclusions 593 References 594

20.1 20.2 20.3 20.3.1 20.4 20.4.1 20.5 20.6

21

21.1 21.2 21.3 21.3.1 21.4 21.5

22

22.1 22.2 22.2.1 22.2.2 22.2.2.1 22.2.2.2 22.2.3 22.2.3.1 22.2.3.2 22.2.3.3

570

Life Cycle and Techno-Economic Assessment of Microplastics Remediation Technologies and Policies 599 Almeenu Rasheed, Divyanshu Sikarwar, and Sovik Das Introduction 599 Technological Efficiency and Social Impact 599 Economic Aspect and Cost–Benefit Analysis 601 SWOT Analysis 602 LCA of Treatment Techniques 604 Conclusion 608 References 608 Case Studies on Microplastic Contamination with a Focus on the Impact of the COVID-19 Pandemic 611 Lourembam Nongdren, Sai Lahar Reddy, Biswajit Samal, Kumar Raja Vanapalli, and Brajesh K. Dubey Introduction 611 Microplastic Contamination 612 Definition 612 Sources 612 Primary MPs 613 Secondary MPs 613 Route of Entry and Distribution of MPs into the Environment 613 Microplastics in Air 614 Microplastics in Water 614 Microplastics in Soil 614

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22.2.4 22.3 22.4 22.4.1 22.4.2 22.5 22.5.1 22.5.2 22.5.3 22.5.4 22.5.5 22.6 22.6.1 22.6.1.1 22.6.1.2 22.6.1.3 22.6.2 22.7 22.8 22.8.1 22.8.2 22.8.3 22.8.4 22.9

Persistence and Accumulation of Microplastics 615 COVID-19 Pandemic: Impact on Waste Management 615 Interactions Between Microplastics and COVID-19 616 Role of Microplastics as a Potential Vector 616 Impacts of COVID-19 Related Measures on Microplastic Pollution 617 Case Studies: COVID-19-Related Microplastic Pollution 617 Case Study: South Korea 617 Case Study: River Thames 617 Case Study: Microplastic Inhalation from the Facemask 618 Case Study: Freshwater Lake, Kerala 618 Case Study: Tamil Nadu 618 Environmental Consequences of Microplastics and COVID-19 618 Impact on the Aquatic Ecosystem 618 Positive Impacts 619 Negative Impacts 619 Impact on Aquatic Species 620 Impact on Terrestrial Ecosystem 621 Human Health Risks 621 Mitigation Strategies 622 Implementing Sustainable Waste Management Practices and Responsible Disposal of PPE 622 Improvement of Municipal Waste Management 623 Enacting Policy Interventions 623 Investing in Research and Development 624 Conclusion 624 References 625 Index

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Preface Wide-spread applications and easy availability have established plastic commodities as day-to-day essentials. However, due to the prevalent improper disposal practices, plastic products gradually degrade to form micro-sized plastics termed as “secondary microplastics (MPs),” which, together with the primary MPs (that are deliberately created in minuscule sizes for its use in cosmetics, personal care products, etc.), are persist in the environment, causing huge, long-term menaces to the environment and living organisms. The presence of MPs in water, soil, and air leads to a pathway for MPs entering into the food chain, affecting multiple organisms with chronic ailments through bioaccumulation and biomagnification. Thus, there exists a strong need to identify the potential sources, analyze the characteristics, and develop reliable, efficient, and cost-effective treatment methods to completely eliminate the toxic effects of MPs from the environment. This book focuses on providing the readers with insights on the fate, occurrence, impacts, removal methodologies, and management strategies of MPs in the environment. The primary topics of the book are categorized into three sections comprising a total of 22 chapters. The first section delves into the classification of MPs based on various physico-chemical properties and degradation pathways of MPs in Chapters 1–3, along with comprehending the different techniques for sampling and quantifying the MPs in Chapter 4. Further, Chapter 5 focuses on various monitoring methods for MPs such as aerial, spatiotemporal, remote sensing, GIS, etc. in addition to describing several polymer identification techniques such as Raman spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and so on. Moreover, the first section comprises the need to understand the environmental and socioeconomic risks and the toxicity levels associated with MP spread through Chapters 6 and 7. The second section particularly specifies MPs in different compartments and their effects on environments and humane society. Chapter 8 covers sources, distribution, fate/transport, and the behavior of MPs in the environment and different systems (e.g., agricultural crops, the food and construction industry, water and solid waste pollution control systems, recycling, and remediation systems). The fate and modeling of MPs through the above-depicted systems and environmental compartments are briefly comprehended through numerical, stochastic, computational, and various other modeling approaches in Chapter 9. Furthermore, Chapter 10 deals with toxicity assessment (for both carcinogenic and noncarcinogenic) of MPs along with focusing on the exposure pathways and interaction of MPs with various emerging contaminants and, persistent, bioaccumulative, and toxic substances

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Preface

(PBTs). Whereas the interaction of MPs with various microbial communities, crops, soil, and the subsequent impacts on microbial metabolism, plant growth, and geo-chemical properties of soil respectively are depicted in Chapter 11 along with specifying the effects of MPs in the food chain and food web. While Chapter 11 focused on the terrestrial environment, Chapter 12 highlights the impacts of MPs on aquatic ecosystems by describing the sources, occurrence, and transport of MPs in aquatic environments, consumption of MPs by aquatic life, consequent effects of MPs on the development of aquatic organisms, including corals, invertebrates, marine, and freshwater biota. Moreover, the second section concludes by explaining about the human exposure pathways of MPs and the subsequent toxic effects, reinforced with certain case studies in Chapter 13. The final section, i.e., Section 3, of the book furnishes the readers with potential solutions for MP pollution through certain measures and alterations taken in the life cycle of plastic production through Chapter 14 and possible prevention measures for hindering the formation of secondary MPs in the environment via Chapter 15. Furthermore, societal strategies to minimize and eradicate plastic waste are described in Chapter 16, and different MP removal technologies such as physical, chemical, biological, and hybrid treatments are elucidated in Chapter 17. Also, Chapters 18 and 19 inform the reader about the applicability of various catalysts for polymer upcycling and about the various potentials and possibilities of biodegradable bioplastics, respectively. Whereas Chapter 20 raises awareness among the readers on the global strategies, existing regulations, and policies based on MP management. In addition, the technological efficiencies, economic feasibility, and environmental and societal impacts of multiple MP treatment technologies are integrated in Chapter 21. The book concludes by illustrating certain case studies, which highlight the impact of COVID-19 on the elevated MP pollution through Chapter 22. This particular book on fate, impacts, removal, and management of MPs in the environment intends to aid students, scientists, researchers, engineers, government officers, process managers, and practicing professionals in addressing and fostering knowledge on MP pollution in different compartments of the environment. The book also will serve as a reference for undergraduate and graduate students, as well as for practicing professionals. The editors convey deep gratitude and sincere appreciation for the diligent efforts and patience of all authors for their valuable contributions to this book. The perspectives expressed in each chapter of this book are those of the authors and should not be construed as opinions of the organizations they work for. Rao Y. Surampalli, Tian C. Zhang, Bashir M. Al-Hashimi, Chih-Ming Kao, Makarand M. Ghangrekar, Puspendu Bhunia, Sovik Das

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Notes on Editors Dr. Rao Y. Surampalli, PhD, PE, BCEE, Hon BC.WRE, F.WEF, F.AAAS, Dist.F.IWA, M.EASA, Dist.M.ASCE, NAC, is President and Chief Executive Officer of the Global Institute for Energy, Environment and Sustainability (GIEES). He was with the U.S. Environmental Protection Agency (USEPA) for 30 years and retired as an engineer director. He received MS and PhD degrees in environmental engineering from Oklahoma State University and Iowa State University, respectively. He is a registered professional engineer in the branches of civil and environmental engineering, and also a Board Certified Environmental Engineer (BCEE) and Water Resources Engineer (BC.WRE) of the American Academy of Environmental Engineers (AAEE) and the American Academy of Water Resources Engineers (AAWRE). He is an adjunct professor in seven universities and Distinguished/Honorary Visiting Professor in six (6) well-known universities abroad. Currently, he serves, or has served on over 85 national and international committees, review panels, or advisory boards including the ASCE National Committee on Energy, Environment and Water Policy. He also served as President of Civil Engineering Certification (CEC), Inc., an entity of ASCE for board certification of various specialties within civil engineering. He is a Distinguished Engineering Alumnus of both the Oklahoma State and Iowa State universities, and an elected member of the European Academy of Sciences and Arts (EASA), an elected member of the U.S. National Academy of Construction (NAC), an elected fellow of the Water Environment Federation and Distinguished Fellow of International Water Association, an elected fellow of the American Association for the Advancement of Science (F.AAAS), and a Distinguished Member of the American Society of Civil Engineers. He also is Editor-in-Chief of the ASCE Journal of Hazardous, Toxic, and Radioactive Waste, past ViceChair of Editorial Board of Water Environment Research Journal and Editor-in-Chief of Nanotechnology for Environmental Engineering Journal (Springer Nature), and serves on the editorial boards of 8 other refereed environmental journals. He has authored over 400 articles in refereed journals, 22 approved patents, 27 refereed books and 183 refereed book chapters, 250 national and international conference presentations and proceedings, and presented over 160 plenary/keynote or invited presentations worldwide. He has received over 30 national awards/honors. Dr. Tian C. Zhang, PhD, PE, BCEE, BC.WRE, F.ASCE, F.AAAS, Dist.M.ASCE, is a professor in the Department of Civil Engineering at the University of Nebraska-Lincoln (UNL), USA. He received his BS degree in civil engineering from Wuhan University of

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Technology, China, in 1982, his MS degree in environmental engineering from Tsinghua University, China, in 1985, and his PhD in environmental engineering from the University of Cincinnati in 1994. He joined the UNL faculty in August 1994. Professor Zhang teaches courses related to water/wastewater treatment, remediation of hazardous wastes, and nonpoint pollution control. Professor Zhang’s research involves fundamentals and applications of nanotechnology and conventional technology for water, wastewater, and storm water treatment and management, remediation of contaminated environments, and detection/ control of emerging contaminants in the environment. Professor Zhang has published more than 250 peer-reviewed journal papers, 80 book chapters, and 16 books since 1994. Professor Zhang is a member of the Water Environmental Federation (WEF), and Association of Environmental Engineering and Science Professors (AEESP). Professor Zhang is a Diplomate of Water Resources Engineer (BC.WRE) of the American Academy of Water Resources Engineers, Board Certified Environmental Engineers (BCEE) of the American Academy of Environmental Engineers, Distinguished Member of American Society of Civil Engineers (Dist.M.ASCE), and Fellow of American Association for the Advancement of Science (F.AAAS), and Member of the European Academy of Sciences and Arts (EASA). Professor Zhang is the associate editor of Journal of Environmental Engineering (since 2007), Journal of Hazardous, Toxic, and Radioactive Waste (since 2006), and the managing editor of Water Environment Research (since 2008). He has been a registered professional engineer in Nebraska, USA, since 2000. Bashir M. Al-Hashimi, CBE, FREng, FRS, FIEEE, FIET, FBCS, is the Vice President (Research & Innovation) and ARM Professor of Computer Engineering at King’s College London in the United Kingdom. He is internationally recognized for his sustained and pioneering research contributions to advanced semiconductor chips test, energy-efficient embedded systems and the emerging research field of energy harvesting computing. His research has led to substantive innovations in enabling hardware and software technologies with application in mobile and digital electronic devices. A highly cited researcher, he has published more than 350 technical papers, with eight best paper awards at international conferences and has authored/coauthored and edited five books and eight book chapters, with his most recent as Many-core Computing: Hardware and Software, IET press (2019). He has overseen the successful supervision of 45 PhD students and has secured over £25m in external research funding from UK research funders and industry. The impact of his computer engineering research and technology transfer has been significant in both academia and industry across the world and it has led to numerous distinctions. He was cofounder (2008) and codirector of the ARM-Southampton Research Centre, which is an industryuniversity collaborative center involving the University of Southampton and ARM, recognized as an exemplar in the UK for industry-academia collaboration. Bashir has led successfully a number of large EPSRC-funded multidisciplinary and interdisciplinary research consortia, including the Holistic battery-free electronics project and the recently completed £5.6m EPSRC PRiME Programme Grant, which included four universities and five industrial partners. He was awarded in 2020 the UK Institution of Engineering and Technology’s Faraday Medal for contributions to manufacturing test of electronics systems (the Institution’s highest honor and one of the most world’s most prestigious international awards for engineers and scientists). In 2018, he received one of the highest national UK honors when

Notes on Editors

he was appointed Commander of the Order of the British Empire (CBE) by Her Majesty Queen Elizabeth II for sustained services to industry and engineering. He was appointed to the Research Excellence Framework (REF) for research impact evaluation of British Higher Education in both 2014 and 2021 and has contributed to numerous government research and education consultations through his active participation in the UK National Engineering Academy - the Royal Academy of Engineering (RAEng) since election to the fellowship in 2013, where he has also been an elected member of the trustee board since 2021. In 2014, he received the Royal Society Wolfson Fellowship for scientific contributions to energy-efficient and reliable computing systems, and in 2012, he received the Design and Test in European Conference Fellowship in recognition of contributions to electronic design and technical leadership. He was an elected fellow of the IEEE in 2009 for contributions to low-power integrated circuits and systems and was recently elected to the Fellowship of the Royal Society and the membership of the European Academy of Sciences and Arts in the same year, 2023. He has an undergraduate degree in electrical engineering and a PhD from University of York (1989). Dr. Chih-Ming Kao, PhD, PE, BCEE, BC.WRE, F.IWA, F.WEF, F.AAAS, Dist.M. ASCE is a Distinguished Chair Professor in the Institute of Environmental Engineering at National Sun Yat-Sen University, Taiwan. Professor Kao is also the coordinator of Environmental Engineering Program at Ministry of Science and Technology, past president of The Chinese Institute of Environmental Engineering, and former president of The Taiwan Association of Soil and Groundwater Environmental Protection. Professor Kao received his MS and PhD degrees in civil and environmental engineering from North Carolina State University in 1989 and 1993, respectively. He is a fellow member of International Water Association (IWA), Distinguished Member of American Society of Civil Engineers (ASCE), a member of the European Academy of Sciences and Arts (EASA), a fellow member of American Association for the Advancement of Science (AAAS), a fellow member of Environment and Water Resource Institute (EWRI), a registered professional engineer in the branch of civil engineering, a certified ground water professional, and a professional hydrologist in the United States. He is also a Diplomate of the American Academy of Environmental Engineers and Diplomate of American Academy of Water Resources Engineers. Professor Kao received the “Distinguished Researcher Award” from Taiwan Ministry of Science and Technology in 2011 and 2015. He is also the receiver of the “Distinguished Engineer Professor Award” from Chinese Institute of Engineers in 2012, and receiver of the “Distinguished Honor Award” from C.T. Ho Foundation in 2013. He also received several awards from ASCE including the State-of-the-Art of Civil Engineering Award in 2013, Hering Medal, Samuel Arnold Greeley Award in 2012, and distinguished theory-oriented paper award in 2008 and 2015. He has over 350 refereed publications. Prof. Makarand M. Ghangrekar, Fellow INAE, M.EASA,M.ASCE, is Institute Chair Professor in the Department of Civil Engineering at Indian Institute of Technology, Kharagpur, and heading two academic units, School of Environmental Science and Engineering and PK Sinha Centre for Bioenergy and renewables, and also Professor-in-Charge, Aditya Choubey Centre for Re-Water Research at Indian Institute of Technology, Kharagpur. He had been visiting scientist to Ben Gurion University, Israel, and University of Newcastle

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upon Tyne, UK, under Marie Curie Fellowship by European Union and had stint as faculty of various capacities in renowned engineering colleges and research institutes. He has been working in the areas of anaerobic wastewater treatment, bioenergy recovery during wastewater treatment using microbial fuel cell and bio-electrochemical systems. He is recognized worldwide in scientific community for his research contribution in the development of bioelectrochemical processes and his research group stands among the top five research laboratories in the world in terms of scientific publications. The first of its kind MFC-based onsite toilet waste treatment system “Bioelectric toilet” developed by him received wide publicity in electronic and print media. He has successfully completed multinational collaborative projects with European countries and few of the projects are ongoing. He has also provided design of industrial wastewater and sewage treatment plants in India and abroad. He has been working on setting up wastewater treatment plants to produce reusable quality treated water at affordable cost. He has guided 25 PhD research scholars and 50 master student’s projects. He has contributed 230 research papers in journals of international repute, out of these 138 papers are on microbial fuel cell and also contributed 50 book chapters. His research work has been presented in more than 250 conferences. He has delivered invited lectures in the many reputed universities in the world. Dr. Puspendu Bhunia, PhD, is presently holding the Associate Professor position at the School of Infrastructure, Indian Institute of Technology, Bhubaneswar, India. He received his BE degree in civil engineering from Indian Institute of Engineering Science and Technology, Shibpur, India, in 2002, his MTech and PhD degrees in environmental engineering from Indian Institute of Technology, Kharagpur, India, in 2004 and 2008, respectively. He joined the Indian Institute of Technology, Bhubaneswar, faculty in July 2009. Dr. Bhunia teaches courses related to water/wastewater treatment and remediation of hazardous wastes. His research interest includes sustainable natural treatment technologies of wastewater, nutrient removal, and green technologies for waste remediation. Dr. Bhunia has authored over 80 technical publications in refereed journals, book chapters, and conference proceedings. He has presented several expert talks at different technical conferences organized nationally and internationally. Dr. Bhunia’s research work has been recognized, including the Best Practice Oriented Paper Award from ASCE. He is a member of the European Academy of Sciences and Arts (EASA). Dr. Bhunia is a member of several professional organizations and also serves as an associate editor of ASCE Journal of Hazardous, Toxic, and Radioactive Waste and is reviewer for more than 30 international peer-reviewed journals. Dr. Sovik Das, PhD, is presently working as an Assistant Professor in environmental engineering of the Department of Civil Engineering, Indian Institute of Technology, Delhi, India. He completed doctoral research work in the field of environmental engineering from the Department of Civil Engineering, Indian Institute of Technology, Kharagpur, India. He is engaged in research work pertaining to bioelectrochemical systems such as microbial electrosynthesis cell, microbial fuel cell, and microbial electrolysis cell for the treatment of different waste streams with concomitant valuable recovery. Currently he is looking in the domain of green hydrogen production from waste and removal of emerging contaminants from water matrix through both electrochemical and bioelectrochemical

Notes on Editors

technologies. He has more than 60 international publications in reputed international journals and 11 book chapters to his credit. Also, he is currently editing two books for International Water Association and Springer Nature. Further, he is also the Associate Editor of Sustainable Chemistry for the Environment of Elsevier, Heliyon (Chemical Engineering Section) of Cell Press, Journal of Hazardous, Toxic, and Radioactive Waste of ASCE and Editorial Board Member of Scientific Reports published by Nature. Moreover, he has served as a reviewer for more than 60 international journals published by Elsevier, Springer, Wiley, etc., and has reviewed more than 500 manuscripts.

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1

Section I The Existence and Characterization of Microplastics

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1 Introduction and Book Overview Yasser Bashir1, Nehaun Zargar1, Neha Sharma1, Almeenu Rasheed1, Sovik Das1, Makarand M. Ghangrekar2, Puspendu Bhunia3, Bashir M. Al-Hashimi4, Rao Y. Surampalli5, Tian C. Zhang6, and Chih-Ming Kao7 1

Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, India Department of Civil Engineering, School of Environmental Science and Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India 3 Environmental Engineering, School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India 4 King’s College, Strand Campus, London, UK 5 Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 6 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 7 Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan 2

1.1

Background and Definition

Plastics are used in an increasing range of applications to ease the day-to-day life of individuals, ranging from food packaging to textiles, disposable medical equipment, and technological equipment and their machinery parts, owing to their exceptional properties. However, improper disposal techniques used for nonbiodegradable plastics have resulted in their persistent presence in the environment leading to an upsurge in plastic pollution. Moreover, the consequential exposure of the microparticles derived from plastics is toxic to human beings. The National Oceanic and Atmospheric Administration defines plastic debris as microplastic (MP) when the particle has a diameter of less than 5 mm (Pironti et al., 2021). These MPs can be mainly categorized into two types based on their origin: primary and secondary MPs (Figure 1.1). Primary MPs are defined as small-sized plastic particles manufactured intentionally in certain minuscule sizes for being used in personal care products and cleaning formulations as microbeads and abrasives, whereas secondary MPs are formed due to the degradation or fragmentation of larger plastic products, such as plastic films, domestic waste, atmospheric deposition, and automobile emissions, in the environment by various natural weathering processes (Ahmed et al., 2021; Pironti et al., 2021). These MPs are further categorized based on their ease of degradation as biodegradable and nonbiodegradable MPs. Biodegradable MPs can be degraded completely by microbes such as fungi, algae, and bacteria, while nonbiodegradable MPs persist in the environment for longer durations without getting degraded easily (Thakur et al., 2023). Materials such as polylactic acid, polyhydroxyalkanoates, polybutylene succinate, and polycaprolactone are

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1 Introduction and Book Overview

Figure 1.1

Types and Sources of Microplastics

some of the common types of biodegradable MPs usually found in plastic bottles, plastic films, medical instruments, tissues, diapers, disposal cups, and food packaging (González-Pleiter et al., 2019; Krueger et al., 2015; Lambert & Wagner, 2018). Furthermore, polyethylene (PE), polypropylene (PP), nylon, corflute, polyvinyl chloride (PVC), highimpact polystyrene (HIPS), polyethylene terephthalate (PET), and polyurethane are some of the types of nonbiodegradable MPs usually found in various types of cans, bottles, food packaging, tires, bumpers, clothes, gaskets and cushions of the furniture (Shah et al., 2008; Wagner & Lambert, 2018; Zhang & Chen, 2020). In addition to the hydrophobic nature of MPs, the high polymer content and surface area aid in resisting the natural degradation processes and thereby persisting in nature (Verschoor, 2015). However, photodegradation, mechanical breakdown, and biological degradation may contribute to their eventual fragmentation into smaller particles having different shapes such as fragments, fibers, spheres, beads, and different colors based on the original color of the parent plastic and additives present (Crawford & Quinn, 2016). These fragmented plastic particles can permeate and persist in the food chain, ultimately leading to bioaccumulation in larger consumer organisms, indicating the prolonged ecological consequences of MP pollution. In this regard, the ingestion pathway is considered as one of the major exposure routes of MPs in several secondary consumers of the ecosystem

1.1 Background and Definition

due to the consumption of MP-contaminated food. Furthermore, MPs can be absorbed through soil, water, atmosphere, and living organisms, which ultimately impacts the well-being of humans subsequently. Recently, researchers have indicated the presence of MPs in various compartments of the ecosystem, such as living organisms ranging from microscopic zooplankton to large mammals, surface water bodies, soil, air, marine environment, and different types of wastewater (Ahmed et al., 2021; Anderson et al., 2017; Carr et al., 2016; Eerkes-Medrano et al., 2015; Hidayaturrahman & Lee, 2019) The chronological demonstration of major milestones of MPs and the escalating trend of studies on MP pollution (Figure 1.2) demonstrates the requirement of MP eradication from the environment. The release of MPs is majorly attributed from manufacturing industries and road dust, encompassing components such as tires, bitumen, and road marking paints subsequently, facilitating the transportation of MPs to the freshwater systems and ultimately to the ocean (Ngo et al., 2019). However, the first research paper on MP pollution was published in 2004, which coined the term “microplastics” for the first time (Thompson et al., 2004). Furthermore, the studies on freshwater matrices based on MP pollution in 2012 indicate the fast spread of MPs to different matrices (Alencastro, 2012). Nevertheless, recent studies have reported the detection of 2.4 ± 1.3 × 105 of both MPs and nanoplastics (NPs) particles per liter of bottled water, with varying composition and morphology, unveiling the critical need to address this issue and eliminate the substantial consumption of MPs and NPs (Qian et al., 2024). Furthermore, the detection of MPs within the size range of 20–469 μm in the blood sample and the detection of 1.42 ± 1.50 MP/g of lung tissue in humans indicate the chances of MP intake through ingestion and inhalation, respectively (Jenner et al., 2022; Yang et al., 2023). In addition, MP was also detected in 76% of the breastmilk samples tested, majorly composed of PE, PVC, and PP particles, within the size range of 2–12 μm (Ragusa et al., 2022). Apart from these, the first-time detection of MPs in all portions of the human placenta, in 2021, within the size range of 5–10 μm, throws light on the huge concern of fetal health and the exposure route of these pollutants (Ragusa et al., 2021). In addition, the detection of MPs in products such as beer, milk, and honey, in poultries such as sheep, ducks, and other organisms such as mussels, crabs, and seabirds demonstrates the intensity of MP spread within the ecosystem (Amélineau et al., 2016; Beriot et al., 2021; Diaz-Basantes et al., 2020; e Silva et al., 2016; Susanti et al., 2021; Wójcik-Fudalewska et al., 2016). Besides humans, 6.7–13.9 MPs/L of cloud water with particles size ranging between 7.1 and 94.6 μm were detected at high-altitude clouds of Japanese mountains indicating the widespread presence of MPs in the environment (Wang et al., 2023). Furthermore, the MP contamination reveals new levels with the first MP detection at Mt. Everest, from a sample collected at an elevation of 8440 m above mean sea level, and the presence of plastic pollutants along with the detection of ingested MPs from the guts of deep aquatic amphipods from six deep ocean trenches including Mariana Trench and New Hebrides Trench (Jamieson et al., 2019; Napper et al., 2020). Notably, researchers found it astounding to detect the presence of MPs in human-untouched areas such as the Amazon Forest and the Polar Regions. The Antarctic and Arctic polar samples were identified with an average of 29 MP particles/L and 0.34 ± 0.31 particles/m3 of water, respectively (Aves et al., 2022; Lusher et al., 2015). Moreover, the Amazon River basin was detected to contain 417–8178 MP

5

Figure 1.2 (a) Chronological Milestones in the History of MP. (b) Number of Papers Published Till 2023 on MP Pollution as per SCOPUS Database Using Keywords “Microplastic” OR “Microplastics” OR “Micro-Sized Plastic” AND “Pollution,” Limiting to Research “Articles” Conveyed Through “English” Language

1.2 Impacts of MPs on the Environment, Society, and Economics

Figure 1.2

(Continued)

particles/kg of dried sediment. The fact that MPs are present at every crevice of the Earth is a direct consequence of the longtime irresponsible usage and disposal of plastic particles. Nevertheless, these detection studies will keep on escalating with time revealing the true nature of the threat created by humans themselves. To tackle this issue, researchers have come up with various household treatment methods to minimize the intake of MPs and NPs on a daily basis, such as boiling tap water (Yu et al., 2024). The study indicates the aggregation of MPs and NPs on the incrustations of calcium carbonate from the tap water, during high temperatures while boiling. Also, the study effectively removed about 80% of PS, PE, and PP particles within the size range of 0.1–150 μm, illustrating the significance of the conventional boiling method in separating out MPs and NPs from the water matrices (Yu et al., 2024). Nevertheless, further research is necessary to come up with alternatives, like bioplastics, which will replace the toxic MPs owing to the former’s easily degradable nature. Moreover, it can replace petrochemical-based plastic polymers, thereby reducing plastic pollution and ensuring a sustainable and plastic-free environment.

1.2 Impacts of MPs on the Environment, Society, and Economics Plastic has become an inalienable part of everyone’s lives; however, unethical and irresponsible disposal of plastic has emerged as a menace over time. These plastics break down into MPs by natural weathering and, hence, are becoming multifaceted threat to the

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1 Introduction and Book Overview

environment, society, and economics (Tran et al., 2023). Due to their fine particulate nature, MPs are ingested by aquatic organisms, leading to bioaccumulation, digestive blockage, and chronic toxicity. Furthermore, ingestion of MPs by the phytoplankton and zooplankton also lowers their carbon consumption, thus resulting in reduced carbon sequestration by marine organisms (Shen et al., 2020). The occurrence of MPs has also been found in soil as a result of plastic mulching, sludge utilization, effluent of wastewater treatment plants (WWTPs) used for irrigation, and atmospheric deposition (He et al., 2018). Consequently, the uptake of MPs by plants is also causing trophic transfer of it into food chains, posing a serious threat to living beings. At present, MPs are widely found in seafood, bottled water, and other food products, becoming the routes of MPs in humans. According to an investigation, it was noted that an individual’s annual consumption of MPs is estimated to be between 39,000 and 52,000, with tap water contributing between 3,000 and 4,000 MPs to this total (Emenike et al., 2023). Ingestion of MPs by humans is linked with various health consequences, including oxidative stress, tissue damage, and inflammation (Emenike et al., 2023). Moreover, MPs also amalgamate with other toxic chemicals and lead to a toxic synergistic effect on the environment. For instance, Verdú et al. (2023) concluded that MP adsorbed on the triclosan caused higher mortality than just triclosan itself on Daphnia magna. Furthermore, MPs are also present in indoor and outdoor air, which, on entering the human body through inhalation may cause irritation and inflammation of the respiratory tract, resulting in symptoms such as wheezing, coughing, dyspnea, and worsening of preexisting respiratory disorders like asthma. These airborne MPs also adsorb other pollutants, such as polycyclic aromatic hydrocarbons, which can be genotoxic once they enter the body through the respiratory system (Gasperi et al., 2018). The adverse impacts of the MPs are not only limited to the environment and living beings; but these also lead to significant economic consequences, affecting different sectors as well as the economy of the nation. Activities related to fishing and aquaculture are seriously jeopardized by MPs, leading to lower quality of farmed fish, thus rendering them unmarketable. Furthermore, a decrease in water quality caused by MP pollution in the ocean has an impact on the survival of fish larvae. This may result in a lower annual catch of fish, which affects fisheries and aquaculture profits and is becoming a serious threat to fisherman by declining their source of income. Furthermore, plastic-laden beaches discourage tourists due to unclean and unpleasant surroundings, which has a detrimental effect on the tourism sector by lowering visitor numbers and revenue for nearby businesses (Kumar et al., 2021). It was estimated that the decline in fishing, tourism, aquaculture, and other industries due to marine plastic pollution caused a gross domestic product (GDP) loss of US$7 billion in 2018. In addition, clean-up activities to eradicate plastic debris from different ecosystems incur great expense to the governments, nongovernmental organizations (NGOs), and concerned citizens, which amounts upto $15 billion annually, hence affecting public budgets (Dalberg, 2021). It is evident that the presence and accumulation of MP in the environment is a global concern, and collective efforts are required to safeguard the ecosystem and living beings from MP pollution (Figure 1.3). This can be achieved by eliminating plastics, switching to biodegradable plastics, or enforcing more stringent policies by the government for plastic usage so that harmony between the environment and human is maintained for a better future.

1.3 Solutions, Knowledge Gaps, and Challenges

Environment a. Bioaccumulation b. Reduced carbon sequestration

Society a. Health impact b. Loss of livelihood

Economics a. Tourism loss b. Loss in gross domestic product c. Financial burden

Figure 1.3

1.3

Impacts of microplastics

Impacts of Microplastics on Environment, Society, and Economics

Solutions, Knowledge Gaps, and Challenges

The occurrence of MPs is problematic for the treatment technologies employed for treating water and wastewater. To overcome this issue, the most prominent solution is to reduce the number of MPs reaching the treatment units thus reducing the adverse impact of MPs on treatment systems. For instance, density separation is one of the first techniques used for extracting MPs from contaminated water to limit the number of MPs entering WWTPs. As most of the MPs are made of PE, PP and polystyrene, they can be consecutively removed by altering the density of water, making the MPs float and easier to be removed through skimming. However, the density of most of the plastics is similar to that of water, and hence, the MPs remain suspended in water, which causes complexity in their removal. Thus, to increase the density of MPs, various salts such as NaCl or NaI are introduced, which make MPs float and then be removed effortlessly (Gent et al., 2009). Even though density separation is efficacious in extracting MPs from samples, it is not suitable for the WWTPs owing to the small size of MPs requiring static mode for separation in contrast to flowing water, which causes dispersion of the particles. Similarly, the coagulation process is also one of the solutions to limit the ingression of MPs into treatment units of WWTP by designing a coagulation step specifically for the flocculation of MPs. In spite of the fact that MPs are susceptible to agglomerate owing to their small size and surface chemistry, their agglomerates are not stable and can be dispersed in turbulent water. Thus, to make strong and stable flocs, coagulants can be used, which will make the MPs settle down or can be removed through skimming. Moreover, electrocoagulation has also been proven as a promising alternative for the removal of MPs by in situ generation of flocs, demonstrating promising removal efficacy of more than 99% at a pH of 7.5 (Perren et al.,

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2018). Still, the coagulation process needs substantial attention from the researchers in order to optimize this technology for the efficacious removal of MPs. Along with density separation and coagulation, biodegradation is also one of the wellestablished solutions, which is the final way to reduce the interaction of MPs with filtration membranes. In biodegradation, microbes depolymerize the MPs into monomers and can be mineralized into simpler compounds such as carbon dioxide, water, and methane in anaerobic conditions. Recently, Yang and coworkers explained that insects can accomplish biodegradation or digestion of plastic owing to the presence of carbon and energy sources in it (Yang et al., 2024). In addition, the synergistic interaction between gut microbes and the digestive system of the insects is accountable to accomplish the biodegradation of plastics via insects (Yang et al., 2024). However, plastic is deficient in other necessary minerals and nutrients, which limits the efficacy of the insects to biodegrade the plastics (Yang et al., 2024). Still, information pertaining to the effect of MPs on the microbial community is still missing and needs to be venerated in order to ensure that MPs are not harmful to the microorganisms utilized for MP degradation. The WWTPs can eliminate as much as 95% of MPs from wastewater; however, this efficiency is unacceptable given the substantial volume of treated wastewater (Auta et al., 2018). To overcome this issue, the simplest approach is to supplement additional treatment technologies to the existing WWTPs, which will enhance their overall efficiency. Through investigating various advanced wastewater treatment technologies, it was observed that the membrane bioreactor (MBR) exhibited the highest MP removal efficiency (99.9%) compared to rapid sand filters. Furthermore, dissolved air flotation demonstrated removal efficiencies of 97% and 95%, respectively, and it will eliminate almost 98% of MPs that are currently discharged into the receiving body (Talvitie et al., 2017). However, the implementation of MBR involves substantial initial investment costs, making this technology highly cost-intensive. Furthermore, MBR is associated with challenges such as the recurrent clogging of membrane pores, requires frequent backwashing, and relatively short lifespans. Despite these drawbacks, MBR has garnered considerable attention for its implementation, with ongoing efforts to modify this technology to be highly efficacious, fouling-resistant, and economically feasible (Judd, 2016). Meanwhile, MPs can also be removed from the ecosystem via chemical and biological means like bacterial degradation of MPs. Indeed, efforts have been made to degrade the MPs with the aid of bacteria; in this veneration, Ideonella sakaiensis 201–F6 has been investigated for degrading the PET at a lab scale (Yoshida et al., 2016). However, the aforementioned investigation has not been examined at a pragmatic scale. A similar scenario is also implicated in the chemical route for the degradation of MPs in the open ecosystem. Hence, from the above discussion, it can be concluded that both biological and chemical routes offer promising solutions at a smaller scale. Thus, more detailed pilot and field-scale investigations are required to understand the feasibility of these technologies for the elimination of MPs from terrestrial and aquatic bodies.

1.4

Policies and Practices to Regulate MPs

To regulate the entrance of MPs into different compartments of the environment, necessary policies and measures could prove to be key drivers in this paradigm shift. These policies will also limit the potentially toxic effects of the MPs downstream. In this context, the

1.5 Book Structure and Overview of Chapters

amalgamation of 5R (rethink, reduce, reuse, recycle, and recover) and circular economy tactics will help in alleviating the process of limiting the release, contamination, and spreading of MPs. The present policies are mainly focused on the disposal of waste on land, whereas policies specifically addressing MPs have often focused on preventing aquatic pollution (Harris et al., 2021). To control the adverse effects of MPs on the environment, various national and international bodies have directed efforts to formulate regulations and practices to protect the aquatic environment (Igalavithana et al., 2022). To elucidate, the United Nations (UN) Conference on Sustainable Development, which was held in Brazil in 2012, addressed MPs as a highly emerging environmental concern. Further, the United States, United Kingdom, South Korea, Sweden, France, Taiwan, and the Netherlands have banned MPs from wash-off beauty products (Munhoz et al., 2022). To add further, the International Coral Reef Initiative and the Secretariat of the Antarctic Treaty sanctioned the reduction of plastic microbeads. Nevertheless, the European Chemical Agency also implemented similar practices to control the microbeads, and Canada categorized MPs in personal care and beauty products as toxins (Munhoz et al., 2022). However, MPs other than personal care products have not drawn the major focus of the policymakers, and thus, abrasive MPs from plastic blasting and automotives are entering the ecosystem. In addition, the Helsinki Convention “HELCOM” suggested a plan to deal with MPs and recommended forming legal instrumentation to act on it and to formulate a formula that will replace the presence of MPs in personal care products. Furthermore, UN resolutions 1/6 and 2/11 on marine plastic litter and MPs have considered it one out of six emerging environmental concerns (Munhoz et al., 2022). Also, the UN decided to work on reducing MPs to achieve one of their Sustainable Development Goals (SDG), specifically number 14, which includes the reduction of contamination via MPs (Walker, 2021). However, there is no specific indication in the SDG goals regarding the MPs and pollution caused by MPs. Still, the regulations are not up to the mark to control the MPs presence in the terrestrial and aquatic ecosystem, which makes the proper management and disposal of MPs challenging, leaving a huge lacuna to be filled in order to assess and control the contamination caused by MPs on the environment. Thus, enforcement of top-down and bottom-up initiatives is the need of the hour to diminish the MPs pollution of the ecosystem.

1.5

Book Structure and Overview of Chapters

The MPs are considered as one among the hidden menaces that are thriving among a population that are completely relying on plastic-based products for easing their day-to-day life, being unaware of the fact that these tiny particles can derail the delicate natural balance. In this regard, this book explores the existence, characterization, impacts, removal, and management of MPs in the environment. The book starts with the formation, classification, and degradation of MPs in section one, along with elucidating the various physicochemical properties of these micro-sized pollutants. Moreover, various advanced techniques for sampling, quantifying, identifying, and monitoring the MP distribution within the environment are also discussed in the initial chapters. Also, recognizing and assessing the risks, both environmental and socio-economical, associated with MPs aid in understanding the strong need to address the persistent perils of these contaminants.

11

12

1 Introduction and Book Overview

Through the second section, the book delves into the sources, distribution, and transport of MPs within different compartments of the environment, such as aquatic, terrestrial, and atmospheric environments. Moreover, it emphasizes more on the toxic effects imparted on various aquatic organisms, including both micro- and macroorganisms, along with specifying the implications of plastic adhesion on coral surfaces and seabed sediments and the potential impacts it can have on biodiversity as a whole. Also, the significant effects of MP interactions with various microbial communities in altering their microbial dynamics are depicted in the second section of the book. In addition, the impacts of MP intrusion into the food web by the transport through plants are also well illustrated. Moreover, the human exposure pathways and the underlying toxic effects of MPs on humans are also elucidated pertaining to some case studies on human exposure to MPs. In addition, different modeling techniques and their applications to gauze MP pollution in terrestrial and aquatic ecosystems are illustrated, such as spatial analysis on MP accumulation regions, transport of marine debris, and prediction on the dispersal and weathering of MPs within the ecosystem. After guiding the reader through the sources, transportation routes, and impacts of MPs on living organisms, the book elucidates, in section three, the various ways of removing, controlling, and even managing the MPs from spreading through various sectors of the environment and subsequently reducing the harm caused to the life around. Here, potential solutions for MPs are also illustrated, such as elevating the use of bioplastics, enhancing the reusability and longevity of plastic products, incorporating a ban and plastic tax on certain products, etc. Moreover, certain approaches such as extended producer responsibility, incorporating changes in lifestyle for reducing plastic wastage, upcycling of polymers etc., can aid in preventing secondary sources of MPs into the environment. In addition, the various MP removal methods, such as physical, chemical, biological, and hybrid treatment techniques, along with their limitations, are also depicted in this book. Furthermore, the life cycle analysis, technoeconomic assessment, and strength-weakness-opportunity-threats (SWOT) analysis of MP removal techniques are elaborated to understand the various impacts caused and cost incurred in these methods, which can aid in perceiving the technological efficiency, social impacts, economic aspects, and cost–benefit ratio of MP remediation technologies. Last but not the least, the book comprehends various global strategies, guidelines, and regulations imparted to reduce and manage the MP pollutants, along with certain case studies on MP contamination and management, for obtaining a strong and deeper understanding of MPs as pollutants. In particular, this book aims to guide researchers and scientists to tackle MP pollution arising from different phases of MP contamination, starting from formation and various removal mechanisms applied in managing and monitoring MP pollution. Since this book, aids in perceiving the various existing guidelines and policies based on the release of MPs, the underlying limitations and challenges for resolving MP pollution are well elaborated for further and continued research.

1.6

Conclusion

This chapter thoroughly summarizes MPs, their definitions, background, and impacts on the environment, society, and economics, along with solutions and strategies for the regulation, control, and treatment of MPs. The presence of MPs has been reported in various

References

water, air, and soil systems, which indicates the uncertainty in the measurement as well as spatial variation. However, the comprehensive examination of the MPs in air and soil is still not significant compared to water and marine environments. Furthermore, MPs can easily transfer from one compartment of the environment to the others, making it more challenging and threatening to the life forms on land and marine bodies. To deal with this problem, proper plastic waste management, along with the development of advanced treatment technologies for the deterioration of the MPs, possess vital significance following the hierarchy of 5Rs (rethink, reduce, reuse, recycle, and recover) and circular economy. Furthermore, biodegradable plastics should be developed and industrialized, which will be an alternative to the conventionally used plastics. Currently, the solutions and regulations to control MP pollution are still lacking in proper integration and implementation globally. Thus, devoted efforts needed to be made to reduce MPs pollution from the environment for the preservation of various life forms in both terrestrial and aquatic ecosystems through the implementation of strict regulation and preservative measures. Moreover, the scientific community needs to prioritize the enhancement of advanced engineering strategies and explicit the proficient mechanism for the effective degradation of the MPs from all compartments of the ecosystem.

References Ahmed, M. B., Rahman, M. S., Alom, J., Hasan, M. S., Johir, M., Mondal, M. I. H., Lee, D.-Y., Park, J., Zhou, J. L., & Yoon, M.-H. (2021). Microplastic particles in the aquatic environment: A systematic review. Science of the Total Environment, 775, 145793. Alencastro, D. (2012). Pollution due to plastics and microplastics in Lake Geneva and in the Mediterranean Sea. Archival Science, 65, 157–164. Amélineau, F., Bonnet, D., Heitz, O., Mortreux, V., Harding, A. M., Karnovsky, N., Walkusz, W., Fort, J., & Grémillet, D. (2016). Microplastic pollution in the Greenland Sea: Background levels and selective contamination of planktivorous diving seabirds. Environmental Pollution, 219, 1131–1139. Anderson, P. J., Warrack, S., Langen, V., Challis, J. K., Hanson, M. L., & Rennie, M. D. (2017). Microplastic contamination in lake Winnipeg, Canada. Environmental Pollution, 225, 223–231. Auta, H. S., Emenike, C. U., Jayanthi, B., & Fauziah, S. H. (2018). Growth kinetics and biodeterioration of polypropylene microplastics by Bacillus sp. and Rhodococcus sp. isolated from mangrove sediment. Marine Pollution Bulletin, 127, 15–21. Aves, A. R., Revell, L. E., Gaw, S., Ruffell, H., Schuddeboom, A., Wotherspoon, N. E., LaRue, M., & McDonald, A. J. (2022). First evidence of microplastics in Antarctic snow. The Cryosphere, 16(6), 2127–2145. Beriot, N., Peek, J., Zornoza, R., Geissen, V., & Lwanga, E. H. (2021). Low density-microplastics detected in sheep faeces and soil: A case study from the intensive vegetable farming in Southeast Spain. Science of the Total Environment, 755, 142653. Carr, S. A., Liu, J., & Tesoro, A. G. (2016). Transport and fate of microplastic particles in wastewater treatment plants. Water Research, 91, 174–182. Crawford, C. B., & Quinn, B. (2016). Microplastic pollutants. Elsevier Limited. Dalberg. (2021). Plastics: The costs to society, the environment and the economy. WWF.

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Diaz-Basantes, M. F., Conesa, J. A., & Fullana, A. (2020). Microplastics in honey, beer, milk and refreshments in Ecuador as emerging contaminants. Sustainability, 12(14), 5514. e Silva, P. P. G., Nobre, C. R., Resaffe, P., Pereira, C. D. S., & Gusmão, F. (2016). Leachate from microplastics impairs larval development in brown mussels. Water Research, 106, 364–370. Eerkes-Medrano, D., Thompson, R. C., & Aldridge, D. C. (2015). Microplastics in freshwater systems: A review of the emerging threats, identification of knowledge gaps and prioritisation of research needs. Water Research, 75, 63–82. Emenike, E. C., Okorie, C. J., Ojeyemi, T., Egbemhenghe, A., Iwuozor, K. O., Saliu, O. D., Okoro, H. K., & Adeniyi, A. G. (2023). From oceans to dinner plates: The impact of microplastics on human health. Heliyon, 9(10), e20440. Gasperi, J., Wright, S. L., Dris, R., Collard, F., Mandin, C., Guerrouache, M., Langlois, V., Kelly, F. J., & Tassin, B. (2018). Microplastics in air: Are we breathing it in? Current Opinion in Environmental Science & Health, 1, 1–5. Gent, M. R., Menendez, M., Toraño, J., & Diego, I. (2009). Recycling of plastic waste by density separation: Prospects for optimization. Waste Management & Research, 27(2), 175–187. González-Pleiter, M., Tamayo-Belda, M., Pulido-Reyes, G., Amariei, G., Leganés, F., Rosal, R., & Fernández-Piñas, F. (2019). Secondary nanoplastics released from a biodegradable microplastic severely impact freshwater environments. Environmental Science: Nano, 6(5), 1382–1392. Harris, L. S., Fennell, J., Fales, R. J., & Carrington, E. (2021). Spatial–temporal growth, distribution, and diffusion of marine microplastic research and national plastic policies. Water, Air, & Soil Pollution, 232, 1–18. He, D., Luo, Y., Lu, S., Liu, M., Song, Y., & Lei, L. (2018). Microplastics in soils: Analytical methods, pollution characteristics and ecological risks. Trends in Analytical Chemistry, 109, 163–172. Hidayaturrahman, H., & Lee, T.-G. (2019). A study on characteristics of microplastic in wastewater of South Korea: Identification, quantification, and fate of microplastics during treatment process. Marine Pollution Bulletin, 146, 696–702. Igalavithana, A. D., Mahagamage, M. G. Y., Gajanayake, P., Abeynayaka, A., Gamaralalage, P. J. D., Ohgaki, M., Takenaka, M., Fukai, T., & Itsubo, N. (2022). Microplastics and potentially toxic elements: Potential human exposure pathways through agricultural lands and policy based countermeasures. Microplastics, 1(1), 102–120. Jamieson, A. J., Brooks, L., Reid, W. D., Piertney, S., Narayanaswamy, B. E., & Linley, T. (2019). Microplastics and synthetic particles ingested by deep-sea amphipods in six of the deepest marine ecosystems on Earth. Royal Society Open Science, 6(2), 180667. Jenner, L. C., Rotchell, J. M., Bennett, R. T., Cowen, M., Tentzeris, V., & Sadofsky, L. R. (2022). Detection of microplastics in human lung tissue using μFTIR spectroscopy. Science of the Total Environment, 831, 154907. Judd, S. J. (2016). The status of industrial and municipal effluent treatment with membrane bioreactor technology. Chemical Engineering Journal, 305, 37–45. Krueger, M. C., Harms, H., & Schlosser, D. (2015). Prospects for microbiological solutions to environmental pollution with plastics. Applied Microbiology and Biotechnology, 99, 8857–8874. Kumar, R., Verma, A., Shome, A., Sinha, R., Sinha, S., Jha, P. K., Kumar, R., Kumar, P., & Shubham, D. (2021). Impacts of plastic pollution on ecosystem services, sustainable

References

development goals, and need to focus on circular economy and policy interventions. Sustainability, 13(17), 9963. Lambert, S., & Wagner, M. (2018). Microplastics are contaminants of emerging concern in freshwater environments: An overview. Springer International Publishing. Lusher, A. L., Tirelli, V., O’Connor, I., & Officer, R. (2015). Microplastics in Arctic polar waters: The first reported values of particles in surface and sub-surface samples. Scientific Reports, 5(1), 14947. Munhoz, D. R., Harkes, P., Beriot, N., Larreta, J., & Basurko, O. C. (2022). Microplastics: A review of policies and responses. Microplastics, 2(1), 1–26. Napper, I. E., Davies, B. F., Clifford, H., Elvin, S., Koldewey, H. J., Mayewski, P. A., Miner, K. R., Potocki, M., Elmore, A. C., & Gajurel, A. P. (2020). Reaching new heights in plastic pollution—Preliminary findings of microplastics on Mount Everest. One Earth, 3(5), 621–630. Ngo, P. L., Pramanik, B. K., Shah, K., & Roychand, R. (2019). Pathway, classification and removal efficiency of microplastics in wastewater treatment plants. Environmental Pollution, 255, 113326. Perren, W., Wojtasik, A., & Cai, Q. (2018). Removal of microbeads from wastewater using electrocoagulation. ACS Omega, 3(3), 3357–3364. Pironti, C., Ricciardi, M., Motta, O., Miele, Y., Proto, A., & Montano, L. (2021). Microplastics in the environment: Intake through the food web, human exposure and toxicological effects. Toxics, 9(9), 224. Qian, N., Gao, X., Lang, X., Deng, H., Bratu, T. M., Chen, Q., Stapleton, P., Yan, B., & Min, W. (2024). Rapid single-particle chemical imaging of nanoplastics by SRS microscopy. Proceedings of the National Academy of Sciences, 121(3), e2300582121. Ragusa, A., Notarstefano, V., Svelato, A., Belloni, A., Gioacchini, G., Blondeel, C., Zucchelli, E., De Luca, C., D’Avino, S., & Gulotta, A. (2022). Raman microspectroscopy detection and characterisation of microplastics in human breastmilk. Polymers, 14(13), 2700. Ragusa, A., Svelato, A., Santacroce, C., Catalano, P., Notarstefano, V., Carnevali, O., Papa, F., Rongioletti, M. C. A., Baiocco, F., & Draghi, S. (2021). Plasticenta: First evidence of microplastics in human placenta. Environment International, 146, 106274. Shah, A. A., Hasan, F., Hameed, A., & Ahmed, S. (2008). Biological degradation of plastics: A comprehensive review. Biotechnology Advances, 26(3), 246–265. Shen, M., Ye, S., Zeng, G., Zhang, Y., Xing, L., Tang, W., Wen, X., & Liu, S. (2020). Can microplastics pose a threat to ocean carbon sequestration? Marine Pollution Bulletin, 150, 110712. Susanti, R., Yuniastuti, A., & Fibriana, F. (2021). The Evidence of microplastic contamination in Central Javanese local ducks from intensive animal husbandry. Water, Air, & Soil Pollution, 232(5), 178. Talvitie, J., Mikola, A., Koistinen, A., & Setälä, O. (2017). Solutions to microplastic pollution– Removal of microplastics from wastewater effluent with advanced wastewater treatment technologies. Water Research, 123, 401–407. Thakur, B., Singh, J., Singh, J., Angmo, D., & Vig, A. P. (2023). Biodegradation of different types of microplastics: Molecular mechanism and degradation efficiency. Science of the Total Environment, 877, 162912. Thompson, R. C., Olsen, Y., Mitchell, R. P., Davis, A., Rowland, S. J., John, A. W., McGonigle, D., & Russell, A. E. (2004). Lost at sea: Where is all the plastic? Science, 304(5672), 838–838.

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Tran, T. V., Jalil, A. A., Nguyen, T. M., Nguyen, T. T. T., Nabgan, W., & Nguyen, D. T. C. (2023). A review on the occurrence, analytical methods, and impact of microplastics in the environment. Environmental Toxicology and Pharmacology, 102, 104248. Verdú, I., Amariei, G., Rueda-Varela, C., González-Pleiter, M., Leganés, F., Rosal, R., & Fernández-Piñas, F. (2023). Biofilm formation strongly influences the vector transport of triclosan-loaded polyethylene microplastics. Science of the Total Environment, 859, 160231. Verschoor, A. (2015). Towards a definition of microplastics: Considerations for the specification of physico-chemical properties. RIVM Letter report 2015-0116. Wagner, M., & Lambert, S. (2018). Freshwater microplastics: Emerging environmental contaminants? Springer Nature. Walker, T. R. (2021). (Micro) plastics and the UN sustainable development goals. Current Opinion in Green and Sustainable Chemistry, 30, 100497. Wang, Y., Okochi, H., Tani, Y., Hayami, H., Minami, Y., Katsumi, N., Takeuchi, M., Sorimachi, A., Fujii, Y., & Kajino, M. (2023). Airborne hydrophilic microplastics in cloud water at high altitudes and their role in cloud formation. Environmental Chemistry Letters, 21(6), 3055–3062. Wójcik-Fudalewska, D., Normant-Saremba, M., & Anastácio, P. (2016). Occurrence of plastic debris in the stomach of the invasive crab Eriocheir sinensis. Marine Pollution Bulletin, 113(1–2), 306–311. Yang, S.-S., Wu, W.-M., Bertocchini, F., Benbow, M. E., Devipriya, S. P., Cha, H. J., Peng, B.-Y., Ding, M.-Q., He, L., & Li, M.-X. (2024). Radical innovation breakthroughs of biodegradation of plastics by insects: History, present and future perspectives. Frontiers of Environmental Science & Engineering, 18(6), 78. Yang, Y., Xie, E., Du, Z., Peng, Z., Han, Z., Li, L., Zhao, R., Qin, Y., Xue, M., & Li, F. (2023). Detection of various microplastics in patients undergoing cardiac surgery. Environmental Science & Technology, 57(30), 10911–10918. Yoshida, S., Hiraga, K., Takehana, T., Taniguchi, I., Yamaji, H., Maeda, Y., Toyohara, K., Miyamoto, K., Kimura, Y., & Oda, K. (2016). A bacterium that degrades and assimilates poly (ethylene terephthalate). Science, 351(6278), 1196–1199. Yu, Z., Wang, J.-J., Liu, L.-Y., Li, Z., & Zeng, E. Y. (2024). Drinking boiled tap water reduces human intake of nanoplastics and microplastics. Environmental Science & Technology Letters, 11, 273–279. Zhang, Z., & Chen, Y. (2020). Effects of microplastics on wastewater and sewage sludge treatment and their removal: A review. Chemical Engineering Journal, 382, 122955.

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2 Classifications and Physiochemical Properties of Microplastics Sudeep Kumar Mishra1, Sanket Dey Chowdhury1, Puspendu Bhunia1, Arindam Sarkar2, Rao Y. Surampalli3, and Tian C. Zhang4 1

Environmental Engineering, School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India Water Resources Engineering, School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India 3 Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 4 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 2

2.1

Introduction

Today, plastics have become an essential component of our modern society. It is incredibly challenging to live without plastics since their widespread production began in the 1950s (Barnes et al., 2009). The term “plastic” is derived from the Greek terms plastikos (meaning “capable of being shaped”) and plastos (meaning “molded”) (Liddell & Scott, 1996). Plastics are extensively utilized in many industries due to their exceptional properties, such as being lightweight, durable, and flexible. Plastics also offer advantages such as electrical and thermal insulation, resistance to corrosion, and affordability. The plastic materials encompass a range of approximately 20 organic polymers that are derived from petroleum sources. These polymers exhibit distinct characteristics and properties, including variations in density and chemical composition. Plastic products are typically categorized based on the chemical structure of the polymer backbone and its side chain. Polypropylene (PP), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polycarbonate (PC), polyamide (PA), polyurethane (PUR), polyethylene terephthalate (PET), and polystyrene (PS) (Figure 2.1) are the most widely used nonbiodegradable plastic polymers, accounting for nearly 90% of global output (Rodríguez-Seijo & Pereira, 2017). The manufacturing of plastic has had a significant surge over the past several decades, leading to the assertion that our current society is predominantly characterized by the prevalence of plastic materials (Campanale et al., 2020). The expansion of manufacturing activities is accompanied by a corresponding rise in the generation of plastic trash, hence exacerbating the pervasive issue of plastic accumulation in the natural environment (Lehner et al., 2019; Shi et al., 2022). Plastics pose a significant challenge in urban solid waste management due to their inert and nonbiodegradable nature (Nayak & Tiwari, 2011). Landfill leachate is also a significant contributor of microplastics (MPs) to the environment (Mishra et al., 2023). The impact of the widespread and unregulated use and

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2 Classifications and Physiochemical Properties of Microplastics

PET (Containers/bottles for beverages (juice, water, beer), detergents)

PC (Compact disks, eyeglasses, security windows, traffic lights, and lenses)

PA (Fibers, fishing line, toothbrush bristles, tubing)

Figure 2.1

HDPE (detergent and shampoo bottles, garbage bags)

LDPE (Bread and frozen food bags, most plastic wraps)

PP (Bottle caps, ketchup bottles, yogurt and, margarine containers

Polymer

PS (Egg cartons, disposable cups, plates cutlery, plastic tableware)

PVC (window cleanerbottles, shower curtains, medicaltubing)

Types and Sources of Nonbiodegradable Plastic Polymers

disposal of nonbiodegradable materials on the environment and its biodiversity is undeniable and concerning (Barnes et al., 2009). According to Ng et al. (2018), plastics can be categorized into four main groups based on their size: macroplastics, which are larger than 20 mm; mesoplastics, which range from 5 to 20 mm; MPs, which are less than 5 mm; and nanoplastics, which measure 1–1,000 nm in size. As previously mentioned, MPs refer to polymeric particles that possess at least one dimension of less than 5 mm. MPs have emerged as a subject of considerable interest among researchers in recent years because of their significant contribution to environmental pollution (Chowdhury et al., 2023; Dey Chowdhury et al., 2023; Ghosh et al., 2024). MPs possess intricate physicochemical characteristics that have implications for their transport, availability to living organisms, and potential toxicity. In addition, these characteristics influence the way MPs interact with pollutants present in the environment. The presence of MPs in the environment is attributed to a diverse range of particles that vary in terms of size, density, shape, and chemical composition (Duis & Coors, 2016).

2.1 Introduction

MPs can be categorized into two distinct groups based on their sources, namely, primary and secondary MPs. Primary MPs refer to plastics that are intentionally manufactured to be microscopic in size. These include virgin plastic production pellets, which typically have a diameter of approximately 2–5 mm. Primary MPs are mostly produced for specialized industrial or household purposes, such as facial cleansers, toothpaste, cosmetics, air-jet medium, and as carriers for pharmaceuticals. On the other hand, secondary MPs are generated in the environment through the degradation of larger plastic debris (Figure 2.2). Secondary MPs are derived from macroplastics that undergo fragmentation due to several environmental factors, including wave action, UV radiation, and physical abrasion. This process occurs both in marine and terrestrial environments (Cole et al., 2011; Pashaei et al., 2021). In the context of secondary MPs sources, textile clothing, vehicle transport, and artificial grass have been identified as significant contributors (Guo et al., 2020). MPs and macroplastics in marine and coastal environments degrade due to weathering and ageing processes such as solar exposure, thermal ageing, biofilm growth, and oxidation (Andrady, 2017). Given the intricate characteristics of plastic particles, MPs have the capacity to serve as absorbers and transporters of environmental contaminants, including heavy metals, pathogens, and organic compounds. MPs, being small in size, can easily become part of biogeochemical cycles and food webs, causing significant impacts on the environment. Furthermore, it is worth noting that MPs have the potential to undergo photochemical, mechanical, or biological breakdown processes, which can result in the generation of nanoplastics. These processes may also lead to the release of internal additives or byproducts, such as copolymers or monomers. It is worth mentioning that the physical and chemical behaviors of MPs in environments can be influenced by the modifications in their properties, including but not limited to color, surface morphology, size, crystallinity, and densities, brought about by additional degradation of primary and secondary MPs (Lambert and Wagner, 2016; Rincon-Rubio et al., 2001; Zhou et al., 2018).

Figure 2.2

Primary and Secondary MPs

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The transformation, interaction, fate, and bioavailability of MPs in aquatic life are influenced by several physicochemical parameters such as shape, size, concentrations, surface charge, and hydrophobicity (Wright et al., 2013). The precise determination of physical and chemical characteristics, such as shape, size, polymer compositions, and functional groups, is crucial in comprehending the behavior and bioavailability of MPs in environments, which ultimately delivers new insight into the development of innovative strategies and regulations that will improve the ability to control and remediate MPs pollution. Moreover, the identification of MPs in the environment poses an unresolved multidimensional challenge. The existing variations in the structural, physical, and chemical properties of plastics (and MPs as well) during use and subsequent disposal results in the comparable intricacy of these substances to that of organic matter that is present in nature (Hoellein et al., 2019). Factors affecting the interactions between MPs and organic compounds are depicted in Figure 2.3. The purpose of this chapter is to present a comprehensive overview of the classification and various properties of MPs derived from nonbiodegradable polymers. The structural properties of MPs, such as crystallinity, particle size, surface morphology, and intra- and interparticle interactions, has been thoroughly discussed. The importance of density, specific gravity, and specific surface area in relation to the fate, transport, and removal of MPs are also highlighted. The impact of chemical properties, such as hydrophobicity, solubility, and chemical composition, on MPs is emphasized. In addition to discussing the various properties, the role thermal stability of MPs has also been explored. In addition, in a subsequent chapter, the properties of MPs derived from biodegradable plastics will be discussed.

Figure 2.3

Factors Affecting the Interactions Between MPs and Organic Compounds

2.2 Structural Properties

2.2

Structural Properties

2.2.1

Crystallinity

Plastics include polymer chains that may exist in either amorphous or crystalline states. Amorphous polymer chains lack organization and exhibit random configurations, whereas crystalline polymer chains possess short-range order and align together to create structured formations. Crystallinity is the proportion of crystalline polymer chains in plastics and may range from 0% to over 90%. This proportion impacts the plastics’ stiffness and melting temperature (Tm) (Balani et al., 2014). Crystallinity is a significant characteristic of polymers as it refers to the presence of a highly organized and densely packed arrangement of polymer chains in the crystalline region. Crystallinity has an impact on physical characteristics like density and permeability. Consequently, this has an impact on their water content and ability to expand, which in turn impacts the availability of sites for microbes to absorb. The degree of crystallinity refers to the proportion of crystalline regions inside polymers where the polymer chains are aligned with one other. The mechanical properties of polymers are directly affected by the level of crystallinity. Semicrystalline polymers possess remarkable characteristics, including heightened strength and improved resistance to fatigue. Amorphous polymers often exhibit traits of being soft and flexible yet they have relatively low strength and fatigue resistance. The degree of crystallinity determines the vulnerability to oxidative degradation and fragmentation during weathering (Andrady, 2017). Furthermore, the amorphous regions of polymers encompass both glassy and rubbery domains. According to Guo and Wang (2019), the physical state of polymers undergoes a shift from a glassy to a rubbery state when the temperature exceeds the glass transition temperature (Tg). Plastics like PE, PP, and PET exhibit a partially crystalline morphology. In this structure, certain segments of the polymer chains in the bulk material are grouped together in oriented parallel bundles, forming crystal-like domains with short-range order. These domains can have dimensions of several hundred angstrom units. The “crystallites” undergo a process of melting, reformation, and growth that is similar to that observed in conventional crystals of organic compounds. The bulk of the polymer typically consists of randomly oriented or amorphous chains, which usually make up a larger fraction and are generally the dominant component. Semicrystalline plastics consist of small crystallites dispersed within a flexible amorphous matrix at a microscale level. The presence of partial crystallinity typically enhances the toughness of the plastic. However, when the degree of crystallinity becomes excessively high, it can cause the material to become brittle. The significance of this morphological model lies in its impact on the susceptibility of semicrystalline plastics, such as PE, PP, and PET, to crack formation and fragmentation under weathering conditions. The estimation of crystallinity in plastics can be conveniently performed using various techniques such as X-ray diffraction, Raman spectroscopy, or thermal analysis (Aggarwal et al., 2008; Kann et al., 2014). Among these techniques, differential scanning calorimetry (DSC), a technique used to measure the melting enthalpy (Hm) of a plastic material (J/g), is particularly useful. By comparing this value to the melting enthalpy of 100% crystalline plastic (Hm,o), an estimate of the percent crystallinity can be obtained (Eq. 2.1).

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2 Classifications and Physiochemical Properties of Microplastics

Percent crystallinity =

Hm × 100 H m,o

21

However, the fractional crystallinity in plastics is not an intrinsic property of the polymer. It is influenced by various factors including the polymer’s chemistry (including the tacticity of the polymer), Mn (g/mol) value, chain branching, thermal history, and processing. The crystalline content of a polymer can be readily altered through physical or thermal treatment, which can impact its inherent weatherability, strength, or density. The process of spinning textile fibers involves the uniaxial drawing of plastic to achieve high extensions. This encourages a significant level of crystallization, resulting in the production of a plastic fiber with exceptional uniaxial strength (Andrady, 2017). Amorphous or “glassy” polymers, such as PS and PVC, are intrinsically incapable of crystallization due to their molecular structure. The materials under consideration do not exhibit a crystalline melting point. However, when subjected to a gradual increase in temperature, they do acquire a certain level of softness or flexibility at a specific temperature known as the Tg. At the Tg, the heat energy applied to the plastic is precisely enough to enable restricted thermal movement in small segments of the polymer chains. At temperatures below a certain threshold, the plastic exhibits the properties of a brittle glassy material. However, when the temperature exceeds the glass transition temperature Tg, the plastic undergoes a transition and behaves like a rubber. The percent crystallinity and Tg of different MPs are illustrated in Table 2.1. The flexibility of a polymer during use is directly related to the temperature at which it is used in relation to its glass transition temperature (Tg). The higher the temperature of use compared to the Tg of the polymer, the more flexible it will be (Andrady, 2017). The importance of percent crystallinity in MPs characteristics is depicted in Figure 2.4. The degree of crystallinity of the oxidized plastic is increased during the early stages of weathering (Rouillon et al., 2016). There are two factors that contribute to this increase. The amorphous polymer undergoes preferential degradation during weathering, resulting in an increase in fractional crystallinity. In addition, the small sections of polymer that are produced through chain scission during degradation move toward each other and undergo crystallization through a process known as “chemi-crystallization.” The crystalline regions

Table 2.1 Properties of Different MPs Properties

LDPE

HDPE

PS

PP

PET

Glass transition ( C)

−100

−80

+100

−25

+69

Crystallinity (%)

30–50

80–90

0

30–50

10–30

Oxidation resistance

Low

Low

Mod

Low

Good

Reference

Andrady (2017)

Majewsky et al. (2016)

Zhang et al. (2020)

Zhang et al. (2020)

Wagner and Lambert (2018)

2.2 Structural Properties

Figure 2.4

Importance of Crysrallinity in MPs Characteristics

are composed of tightly structured polymer chains that impact the density and permeability of the polymer. This, in turn, controls the hydration and swelling behavior of the material. When the concentration of organic compounds is significantly high, the surface adsorption sites of the crystalline region of MPs rapidly become saturated, thereby restricting any further adsorption. Conversely, when the concentration is low, adsorption may prevail in the crystalline region. Furthermore, it should be noted that the concentration of organic compounds does not have an impact on the sorption behavior in the amorphous region of MPs. This is due to the dominance of partitioning, which occurs at all concentrations (Velez et al., 2018).

2.2.2

Particle Size

Plastic debris found in the environment is divided into four distinct size categories. MPs are particles that range in size from 1 μm to 5 mm. There are three additional categories: macroplastic (larger than 20 mm), mesoplastic (5–20 mm), and nanoplastic (smaller than 1 μm) (Figure 2.5) (Lastovina & Budnyk, 2021). The harmful impact of MPs on organisms is mostly influenced by the size of the particles at a physiological level (Chouchene et al., 2021). The bioavailability of MPs in lower trophic species is mostly influenced by their size. Ge et al. (2021) found that the consumption of MPs by organisms is mostly influenced by their size rather than other variables. Furthermore, several animals have a limited ability to differentiate between MPs and naturally occurring prey of similar size. In general, it can be observed that there is a rise in the harmful effects of MPs on organisms as the particle size decreases. With the continuous degradation of MPs in the environment, the abundance of smaller fragments progressively increases. Plastics exist in various forms, including fragments, pellets, films, and fibers. The size of the molecules in plastics has a significant impact on their mechanical, thermal, and biological degradation. MPs can be found in the environment in

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Figure 2.5

Distinct Size Categories of Plastics Found in the Environment

various forms, with each fragment’s shape being influenced by factors such as the original form of primary plastics, degradation, and erosion processes on the particle surface (such as biological breakdown, photodegradation, and physical forces), and the amount of time it has spent in the environment. Sharp edges may indicate a recent introduction, while smooth edges are often associated with a longer residence time (Hidalgo-Ruz et al., 2012). The degree of these degradations ideally increases as the molecular size decreases (Gowariker et al., 2000). Within controlled laboratory settings, MP particles that are smaller, exhibit a higher susceptibility to degradation. This is due to their larger specific surface area, which enables them to adsorb a greater amount of catalyst. The increased contact area with the catalyst facilitates the process of MP degradation (Jiang et al., 2020). MPs pose a more complex challenge in reality due to their small size and high specific surface area, which enables them to adsorb significant quantities of contaminants. This characteristic makes the degradation of MPs more difficult (Chen et al., 2019a). The presence of contaminants can impede the photodegradation process of MPs by obstructing the UV radiation. Furthermore, the presence of antibiotics and persistent organic pollutants (POPs) in these contaminants has the potential to exert toxicity on the biofilm that forms on the surface of MPs. This toxicity can impede the natural process of biodegradation of MPs (Zhang et al., 2020). According to Eo et al. (2018), there is a greater abundance of small MPs, ranging from 0.02 to 1 mm, compared to larger MPs, which range from 1 to 5 mm. The small dimensions of MPs render them highly bioavailable to aquatic organisms, particularly those belonging to low trophic levels. These many faunal species, which may consist of invertebrates, are susceptible to predation by organisms at higher trophic levels. The separation of MPs is commonly accomplished via the utilization of sieves, which possess mesh sizes that typically range from 0.038 to 4.75 mm. These sieves can be employed individually or in a sequential manner to facilitate the separation process. In addition, filters featuring narrow mesh sizes, such as those ranging from 0.02 to 5 μm, are employed for the purpose of segregating minute MPs or nanoplastics (Hollman et al., 2013; Li et al., 2018; Masura et al., 2015). Chromatographic techniques, including active and passive separation methods, are commonly employed for the isolation of plastic particles with sizes less than 1 μm. Active separations

2.2 Structural Properties

involve the application of external fields, as demonstrated by the field flow fractionation technique (Mintenig et al., 2016), within microfluidic environments to separate dispersed particles. On the other hand, passive separations, exemplified by hydrodynamic chromatography (Blom et al., 2003), rely on hydrodynamic and surface forces to achieve particle separation in a liquid medium.

2.2.3

Surface Morphology

In general, the various morphologies of MPs have the potential to affect their dispersion and transportation patterns, biological consequences, as well as the efficacy of collecting and detecting MPs. By examining the shapes, compositions, sizes, and colors of MPs, it is possible to deduce their origins. The extraction efficiency in the field of environmental MPs collection and detection has been found to be influenced by the morphological forms of MPs. The morphology of MPs displays a wide range of diversity, including fibers, microbeads, films, foams, pellets, and more (Hua et al., 2022). The populations of MPs exhibit substantial variation throughout the natural environment. In aquatic habitats, such as the water column and sediment, the predominant types of MPs that were often identified were fibers, accounting for 52% in the water column and 45% in the sediment. Following fibers, other types of MPs observed included fragments, beads/spherules, films, foam, and many other forms (Burns and Boxall, 2018). Moreover, according to Zhang et al. (2020), fibers constitute the predominant kind of MPs found in the atmosphere. However, the circumstances vary in marine environments. According to Cózar et al. (2017), the form most commonly observed in the Arctic Ocean is the fragment. In certain instances, it has been shown that samples collected from various locations within the same city might exhibit distinct variations in their shape and distribution (Wang et al., 2018). Meanwhile, the environmental conditions can influence the behaviors of MPs based on their respective shapes. Using the terrestrial compartment as a case study, it has been seen that spherical particles have the ability to migrate downwards and penetrate deep into the soil (Li et al., 2020). Conversely, the introduction of polyester microfibers has been found to cause entanglement of soil particles, resulting in the formation of clods and micropores inside the soil. This phenomenon leads to alterations in the physical characteristics of the soil (Zhang et al., 2019). The settling velocity of MPs in an aqueous environment can be significantly influenced by their form. Khatmullina and Isachenko (2017) found that the association between sizes and settling velocity is predetermined by its shape and cannot be adequately explained by a singular universal relationship. Fibrous MPs exhibit a prevalent morphology in the context of atmospheric particles. The study revealed that the dispersion of fibrous MPs can extend over an area ranging from 640 to 8700 km2, whereas the dispersion of nonfibrous MPs was projected to cover an area of 186–875 km2. According to Wright et al. (2020), the primary factor considered in determining the air settling velocity of MPs was the form of the particles. In the context of wastewater treatment plants, it has been observed that fibers are generally found to be more easily eliminated during the pretreatment phase compared to fragments. Conversely, the secondary treatment phase tends to remove a greater proportion of fragments as opposed to fibers. This difference can be attributed to the fact that fragments and granules have a higher likelihood of being entrapped by solid flocs or microorganisms, as highlighted in the studies conducted by Sun

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et al. (2019) and Ngo et al. (2019). Furthermore, it has been observed by Sun et al. (2019) that fibers have the capability to longitudinally permeate filters during tertiary treatment, hence leading to an increase in the relative quantities present in the final effluents. In the study conducted by Masiá et al. (2020), it was shown that the retention duration of MPs in biota can be influenced by their shape. This finding suggests that particular MPs may have long-term impacts. Based on the findings of Ngo et al. (2019), it can be inferred that certain shapes exhibit varying degrees of attraction toward microorganisms. Consequently, the adhesion of organic pollutants is likely to exhibit various characteristics across various shapes. Nevertheless, the predominant body of research investigating the impacts of MPs on organisms has mostly utilized MPs in round shapes, while investigations into the effects of other shapes are still in their nascent phase (Foley et al., 2018). Hence, it is imperative that future study places greater emphasis on investigating the impacts of various shapes. It is of significance to conduct a comparative analysis of the shape effects while maintaining consistent size and polymer type. This approach aids in discerning whether the adverse effects seen are attributed to the physical characteristics or chemical composition of MPs (Trestrail et al., 2020). Researchers have also utilized the shape of MPs in various studies to gain insights into their origin and pathways (Murray & Cowie, 2011). For instance, fibers were the most prevalent form of MPs discovered in harbors, as well as in sediment from beaches along the Belgian coast and in agricultural soils that received sewage sludge. Based on their similarities, the microbeads discovered in the coastal water of Hong Kong were linked to those used in personal care products. The authors suggest that these microbeads made their way into the sea either through discharges from local treatment plants or from untreated wastewaters that were directly washed into the waterways (Cheung & Fok, 2016). Also, plastics possess an inherent quality of color that aids in visually identifying and distinguishing them from other elements in environmental samples (Hidalgo-Ruz et al., 2012). Industry has incorporated various pigments into polymer blends to enhance the visual appeal of plastic materials. In addition, these pigments can be used as inorganic additives to bolster mechanical strength and protect against UV degradation or fire hazards. The significance of MPs colors lies in their ability to increase the chances of ingestion, as they can be easily confused with food by various organisms. Certain species of fish and their larvae are known to be visual predators, hunting down small zooplankton as their prey. Interestingly, they may also mistake MPs that resemble their usual food, such as white, tan, and yellow plastic, as a potential meal (Wright et al., 2013). Color has been used for an initial determination of the chemical composition, as clear and transparent objects have been attributed to PP, white plastic to polyethylene, and opaque hues to LDPE. In addition, the color of a substance has been observed to reflect its residence time at the sea surface or the level of weathering it has undergone (Turner & Holmes, 2011). This is evident in the degree of yellowing or darkening, which is directly related to the increase in the carbonyl index and therefore indicates the extent of photooxidation or ageing. When it comes to pigmented pellets, they typically experience a loss of color and become lighter (Stolte et al., 2015). Furthermore, the photodegradation of MPs may be influenced by their color. This is likely due to the fact that dark colors, particularly black, exhibit higher light absorption capabilities, resulting in more effective photodegradation compared to light-colored MPs

2.2 Structural Properties

(Jiang et al., 2020). Numerous studies have been conducted to document the morphological characteristics of MPs. These studies have evaluated the form and/or color of MPs, often utilizing optical microscopy techniques like stereomicroscopy. Visual examination was utilized to generate classes based on color and form. The methods employed for the characterization of surface morphology were scanning electron microscopy (SEM), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS), and environmental scanning microscopy–energy dispersive X-ray spectroscopy (ESEM–EDS). Both SEM–EDS and ESEM–EDS techniques were employed to analyze the surface morphology of MPs and ascertain the elemental makeup of polymers (Rocha-Santos & Duarte, 2015).

2.2.4

Intra- and Interparticular Interactions

The degradation of MPs can be significantly influenced by the presence of chemical bonds and functional groups that are resistant to attack, such as carbon–carbon and ester bonds (Chowdhury et al., 2022a, b). The degradation process can be influenced by various factors, including the minimally reactive functional groups present in the backbone, the chain mobility, and the crystallinity of the material (Tokiwa & Calabia, 2008; Webb et al., 2012). According to various studies, plastic polymers that have ester bonds, such as polyester and PUR, are found to be more biodegradable compared to those without ester bonds (Barlow et al., 2020; Liu et al., 2021). The degradation efficiency of MPs can be influenced by the specific structure and complexity of their composition due to their impact on enzyme accessibility and photosensitivity. Plastic polymers that have short and regular repeating units, high symmetry, and strong interchain hydrogen bonds, such as PE, PP, and PET, typically have limited enzyme accessibility and are not easily degraded (Artham & Doble, 2010; Kaczmarek et al., 2007; Kumar et al., 2006). Furthermore, the degradation process is influenced by the varying molecular composition of plastics. This is due to the fact that the surface hydrophobicity of polymers, which subsequently impacts the adsorption of plastics, is influenced by the varying molecular composition of plastics. The strength of adsorption dictates the ease with which the plastics adhere to microorganisms (Artham & Doble, 2010). Common plastics such as PE, PP, PVC, and PS exhibit very low biodegradability in natural environments. This is due to the presence of highly stable carbon–carbon bonds in their structure, as well as their high molecular weight and hydrophobic nature. These characteristics make them chemically and biologically inert, as no enzymes have been found to effectively break their carbon–carbon bonds. Furthermore, these plastics lack functional groups that can be eroded by biological enzymes, light, or water. Polymers with structures characterized by short and repeating units, high symmetry, and strong interchain hydrogen bonding exhibit a reduced sorption potential. An illustrative instance is the comparison between LDPE and HDPE. LDPE consists of significant amounts of branches that hinder the polymer chains from aligning closely next to one other. As a consequence, there is a reduced level of crystallinity and a density ranging from 0.90 to 0.94 g/cm3. HDPE is composed mostly of straight unbranched molecules and has a chemical structure that is quite similar to pure PE. The characteristic of being linear HDPE has a significant level of crystallinity and possesses a density ranging from 0.94 to 0.97 g/cm3 (Bajracharya et al., 2014). Batch sorption tests were conducted to assess the sorption of PAHs to LDPE and HDPE pellets. The results revealed that LDPE had greater diffusion coefficients compared to HDPE,

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indicating that LDPE reached equilibrium faster than HDPE for low-density polymers (Fries & Zarfl, 2012).

2.3

Physical Properties

The physical characteristics of MPs have long been recognized as a crucial aspect in the investigation of their contamination in the environment, as they offer valuable insights into the behavior and potential negative impacts of these submerged particles. MPs lacking nutritional value have the potential to give rise to many ecological issues and eventually lead to mortality of many aquatic animals, when ingested (Luís et al., 2015; Pauly et al., 1998; Wright et al., 2013). Hence, the subsequent sections will explore the physical characteristics of MPs, including their density, specific gravity, and specific surface area. These attributes are a result of prolonged exposure to weathering processes in the natural environment. The aforementioned characteristics render MPs very suitable for transporting pollutants and detrimental microbes across aquatic ecosystems.

2.3.1

Density and Specific Gravity

The distribution of MPs in the water column is influenced by the density of these particles. In a broad sense, both PE and PP exhibit characteristics of floating MPs due to their lower densities relative to water. PVC, PS, PET, and PA exhibit higher density compared to water, resulting in their tendency to submerge in the water column. Nevertheless, the features of MPs, such as crystallinity and density, are not intrinsic characteristics that remain constant since they may be easily altered during the process of weathering and aging. The modifications in the characteristics of MPs are discussed in the subsequent section (Guo & Wang, 2019). The distribution and bioavailability of MPs can be influenced by their density, resulting in varying ingestion patterns across creatures at different trophic levels. Deep-sea sediments have the potential to act as a receptacle for plastic debris. Plastics with a high density (ρ > 1 g/cm3) may settle to the bottom as a result of gravitational attraction, while those with a low density (ρ < 1 g/cm3) may settle via biofouling (Chen et al., 2019b; Kooi et al., 2017). According to Roch et al. (2020), the ingestion frequency of MPs with higher density was found to be higher compared to floating particles. This might be attributed to the wider distribution of MPs throughout the water column. MPs and high-density polymers, except PVC, which possess a specific density of 1.38 g/cm3, may, conversely, have a propensity to submerge. The densities of plastic particles can vary significantly based on the type of polymer and the manufacturing process. Typically, plastic particles exhibit a broad spectrum of density values, spanning from 1.05 g/cm3 for PS foam to 2.1–2.3 g/cm3 for polytetrafluoroethylene (Teflon). Plastic particles generally have a significantly lower specific density compared to sediments, which is usually around 2.65 g/cm3 (Chubarenko et al., 2016; Rocha-Santos & Duarte, 2015). The densities of different MPs are presented in Table 2.2. Plastic densities vary according to composition and surpass those of water. The majority of initial investigations into plastics are centered on macrodebris that was adrift at sea or stranded along

2.3 Physical Properties

Table 2.2 Density of Different MPs (Data taken from Rodríguez-Seijo & Pereira, 2017; Ullmann, 2016; Wagner & Lambert, 2018) Polymer

Density (g/cm3)

Low-density polyethylene (LDPE)

0.92

Polyethylene (PE)

0.92–0.96

High-density polyethylene (HDPE)

0.96

Polyurethane

1.2

Polystyrene (PS)

1.05–1.07

Polyvinyl chloride (PVC)

1.35–1.39

Polypropylene (PP)

0.905

Polyamides (PA) (nylons)

1.02–1.06

Polycarbonate (PC)

1.20–1.22

Polyester (PES)

1.40

Polyethylene terephthalate (PET)

1.38

Polytetrafluoroethylene (teflon) Polymethyl methacrylate (acrylic)

2.1–2.3 1.09–1.20

coastlines. These consist of single-use container components made of low-density polymers, such as PE and PP. Conversely, numerous other polymers (PC, PET, and PVC, for instance) have a greater density than water and will therefore sink. Even these rudimentary prognostications regarding fate may prove deceptive in aquatic environments, given that most surfaces ultimately accumulate biofilm or aggregations (Zettler et al., 2013), which can eventually cause buoyant plastics to sink (Hale et al., 2020). A considerable number of plastics float on the water’s surface because their density is lower than that of seawater. As a consequence, these plastics are exposed to greater oxygen and sunlight and can therefore degrade under aerobic conditions. Due to the predominantly anaerobic conditions at benthic locations, the residual plastics will be subjected to anaerobic biodegradation, which results in the formation of water and methane (Ryan et al., 2009; Stephanie et al., 2013). The fate of MPs during the remediation of wastewater is predominantly determined by the density of the particles. To eliminate macrodebris, the majority of treatment schemes begin by filtering the influent and then settle to remove dense sediment and grit. Lowdensity plastic, such as PE (with a density range of 0.92–0.96 g/cm3), will float and can be easily taken in by filter feeders or planktivorous organisms. On the other hand, highdensity plastics like PVC (with a density range of 1.35–1.39 g/cm3) tend to sink and accumulate in sediments (Wright et al., 2013). These plastics are more prone to being consumed by detritivores and benthic organisms. However, various environmental processes can alter this tendency by increasing the density of MPs, depending on their residence time (Browne et al., 2007).

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2.3.2

Specific Surface Area

Specific surface area is a property of solids defined as the total surface area of a material per unit mass. The specific surface area increases with decreasing particle size. The composition and structure of plastics play a crucial role in determining their degradability. Furthermore, the presence of various forms of plastics can impact their degradability. Plastics with a larger specific surface area tend to degrade at a faster rate, as the degradation process primarily affects the surface of the plastics (Gewert et al., 2015). On the other hand, a larger specific surface area leads to increased adsorption, which in turn impacts degradation by absorbing more substances. The higher sorption capacity of MPs to organic compounds can typically be attributed to their smaller particle sizes and higher specific surface areas. However, it is important to note that this explanation does not apply universally in all cases (Mei et al., 2020). In their study, Zhan et al. (2016) investigated the sorption behavior of MPs on PCB77 at a concentration of 0.2 mg/L. The researchers observed a negative relationship between the sorption capacity, which ranged from 70 to 210 μg/g, and the particle size of the MPs, which varied from 0.18 to 5.0 mm in diameter. Hüffer and Hofmann (2016) investigated four types of MPs, namely, PE, PS, PVC, and PA. These MPs varied in diameter, with PVC having a diameter of 57.64 ± 26.5 μm and PS having a diameter of 168.55 ± 57.55 μm. In addition, they had different specific surface areas, ranging from 0.156 m2/g for PA to 0.338 m2/g for PS. The study found that the sorption capacities of organic compounds by MPs did not depend on their particle size. However, there was a consistent trend observed in both sorption capacities and specific surface areas, with PS having the highest sorption capacity followed by PVC, PE, and PA. Therefore, both particle size and specific surface area (SSA) are factors that affect the sorption capacities of a given material. However, when comparing the sorption capacities between different materials, SSA is considered to be a more suitable parameter. Moreover, polymer biodegradation occurs at a faster rate with increasing surface area and decreasing particle size (Chinaglia et al., 2018); however, this relationship has not been thoroughly investigated in marine environments. This may significantly influence the MPs’ long-term fate (Figure 2.6).

Figure 2.6

Proposed Relationship Between Particle Size, Surface Area and Total Mass of MPs

2.4 Chemical Properties

2.4

Chemical Properties

2.4.1

Hydrophobicity

MPs possess hydrophobic properties and have extensive surface areas. Hydrophobicity is a property that indicates the ability of a plastic surface to resist water. This characteristic can be quantified by measuring the contact angle between water droplets and the surface, a process that requires the use of a goniometer. Plastics such as PE, PP, PS, PET, and PVC exhibit high hydrophobicity. However, degradation processes can decrease their hydrophobicity by incorporating hydrophilic functional groups into the polymer chain (Wilkes & Aristilde, 2017). Plastics have the ability to limit microbial activity by impeding water absorption in hydrophobic environments. Also, the extent of algal colonization on MPs development, and therefore the formation of biofilms is influenced by the hydrophobicity of the MPs (Miao et al., 2021; Wright et al., 2020). Once MPs are released into the environment without limitations, specific contaminants such as dichlorodiphenyltrichloroethane isomers, polychlorinated biphenyls, hexachlorocyclohexanes (HCHs), polycyclic aromatic hydrocarbons (PAHs), and pesticides can be adsorbed due to their hydrophobic nature and high surface area to volume ratio. Due to their relatively low solubility in water, hydrophobic organic contaminants (HOCs) tend to separate and adhere to hydrophobic phases, including plastic particulates, organic matter, and detritus. Therefore, MPs are regarded as HOC vectors. Furthermore, variations in the molecular composition of plastics can result in varying levels of hydrophobicity, ultimately impacting the adsorption of these materials (Artham & Doble, 2010). MPs possess a propensity to adsorb and accumulate contaminants from the adjacent water due to their diminutive dimensions and substantial surface-to-volume ratio (Li et al., 2018). The sorption characteristics of MPs are influenced by the inherent features of both the MPs themselves and the contaminants involved (Fu et al., 2021). The hydrophobic nature and substantial surface area of MPs facilitate their capacity to adsorb various contaminants through both chemical and physical interactions. The main component of plastics is resin, which possesses a nonwetting surface and exhibits strong hydrophobicity. Organic pollutants typically exhibit a high degree of fat solubility and a low degree of water solubility. As a result, these pollutants readily adhere to the surface of MPs (Li et al., 2019). The octanol/water partition coefficient (Kow/LogKow) is a measure of the hydrophobicity of a substance, as described by Zhang et al. (2012). The ease of absorption of organic compounds by MPs is likely to be higher for those with high LogKow values.

2.4.2

Solubility

The water solubility of MPs is inversely proportional to its hydrophobicity and directly proportional to its hydrophilicity (Chowdhury et al., 2022a; Dey Chowdhury et al., 2022). Compounds with low water solubility are prone to undergoing photocatalytic degradation. Plastics exhibit reduced susceptibility to microbial attack due to a decrease in their solubility (Siracusa et al., 2008). Not all polymers can be dissolved in water, but there are certain types of polymers that are water soluble. These water-soluble polymers have the ability to break

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down and transform into alcohols, ketones, and acids. The degradation ability of microorganisms is negatively impacted when the solubility of polymers is decreased.

2.4.3

Chemical Composition

The chemical properties of a MP can vary depending on the polymers and additives it contains, and these properties may also change over time as the MP ages. Furthermore, the surface chemistry of polymers can be altered by the formation of new functional groups through processes such as photo and oxidative degradation. Plastics are susceptible to varying degrees of weathering. The most detrimental effects of solar exposure on the polymer are frequently caused by chemical oxidation. Additives may, as stated previously, mitigate this degradation. Photooxidation occurs most rapidly at the water’s surface, on beaches, and in exposed terrestrial environments; protection from aquatic detritus, soil, or landfills makes it negligible. Weinstein et al. (2016) observed that the formation of biofilm on plastic surfaces could result in a 99% reduction in UV light penetration. The following section provides the chemical compositions of various polymers: PE: PE MPs may be classified into two primary classes depending on their density: HDPE and LDPE (Patel et al., 2020). PE is the most widely used plastic in many sectors because of its exceptional chemical and physical qualities. The low density of LDPE is mostly attributed to the presence of small branching molecules in the polymer backbone. PET: PET falls within the category of thermoplastics. This plastic polymer is used in several sectors, including the fiber, bottle, and film industries, and is connected by an ester bond. The PET structure is composed of both amorphous and semicrystalline regions. PET undergoes a phase change and becomes a liquid at elevated temperatures, specifically at 260 C. The half-life of PET is about 700 years under typical environmental conditions (Horvath et al. 2018). PS: PS is an aromatic polymer made from a liquid hydrocarbon called styrene, which is derived from petroleum. This plastic is widely utilized in the food and packaging sectors because to its distinct properties, including its hardness, rigidity, and solid state at room temperature. Its transparency further adds to its significance (Dağ et al., 2019). PP: PP may be produced by primary and secondary MP processes. Primary PP is a frequently encountered component in cosmetics and personal care products (Uheida et al., 2021). PP is classified as a low-density plastic, having an average density of 0.94 g/cm3. PP is composed of a linear hydrocarbon structure consisting only of carbon atoms in its primary ring structure. PP has a hydrophobic surface as a result of its hydrocarbon structure. PP exists in three stereoisomers: isotactic, syndiotactic, and atactic. Among these, isotactic PP is the most prevalent plastic, mostly used in the food and medical sectors. Due to its hydrophobic nature and rough surface, it exhibits resilience and resistance to degradation in the environment (Khoironi et al., 2020). PVC: Polyvinyl-based MP is composed of a polymer with a vinyl backbone. The polymer chains are formed by the repeating vinyl (ethenyl) monomers, with variations in their branches. These branches contribute to the distinctiveness of the polyvinyl-integrated β-diketone-based polymer. PVC is a widely manufactured material in the industry that is formed by incorporating chlorine into its structure. Modifying the molecular structure of a polymer by introducing various branches can result in distinct qualities. For instance, adding acetate would create a plastic substance known as polyvinyl acetate/polyvinyl

2.5 Thermal Stability

Table 2.3

Polymeric MPs and Their Monomers, Monomer Structure, and Chemical Formula

Polymer

Monomer

Chemical formula

Monomer structure

High-density polyethylene (HDPE)

Ethene

C 2H 4

H2C=CH2

Low-density polyethylene (HDPE)

Ethene

C 2H 4

H2C=CH2

Polyethylene terephthalate (PET)

Ethylene terephthalate

C10H8O4

Polypropylene (PP) Polyvinyl chloride Polystyrene

Propylene Vinyl chloride Styrene

O

O

HO C 3H 6 C2H3Cl C 8H 8

H2C H2C

O

OH

CH3 Cl CH2

alcohol. Polyvinyl butyral is formed when a butyral molecule is introduced to the branch (Akovali 2012). The polymeric MPs and their corresponding monomers, including their monomer structure and chemical formula, are presented in Table 2.3.

2.5

Thermal Stability

Thermal stability is a significant thermal characteristic that demonstrates a plastic material’s ability to withstand heat and preserve its chemical composition and mechanical qualities. Thermal stability may be assessed by thermogravimetric analysis (TGA), which measures the change in weight over time in response to temperature variations. The thermal stability of polymers is determined by their chemical structure, crystallinity, and molecular weight. It may be altered by introducing plastic additives. Plastics are categorized into two classes based on their thermal properties: thermoplastics and thermosetting polymers. Thermoplastic is a type of plastic that has the unique ability to be molded multiple times without undergoing any chemical changes in its composition when heated. Thermo-plastics include PP, PE, PVC, PS, and polytetrafluoroethylene (PTFE). Thermosetting plastic is melted and cast into a specific shape, but once it solidifies, it cannot be melted or modified again. According to Ghosh et al. (2013), it is important to note that not all chemical changes are considered examples of thermosetting polymers. Plastics have the ability to undergo thermo-oxidative reactions when exposed to high temperatures. When an adequate amount of heat is absorbed by the polymer, surpassing the energy barrier, it results in the breaking of long polymer chains and the generation of radicals (Peterson et al., 2001; Pirsaheb et al., 2020). The glass transition temperature (Tg) and melting point (Tm) are significant thermal characteristics of plastics. Tg is the temperature at which a polymer undergoes a transition from a rigid, glassy state to a more flexible, elastic

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state. Plastics exhibit flexibility when exposed to temperatures above Tg. However, plastics undergo a transition to a rigid state when subjected to temperatures below Tg. This change in mechanical properties is attributed to alterations in molecular mobility (Rudin & Choi, 2013). When exposed to oxygen, plastics that contain hydrogen as a component undergo exothermic oxidation at temperatures near 200 C. Plastics with a higher Tm typically require even higher temperatures for this oxidation process to occur (Kotoyori, 1972). The thermal parameters Tg and Tm show significant importance in the field of plastics. Tg and Tm of a polymer are influenced by the mobility and flexibility of its chains. These properties, in turn, are influenced by various factors such as intermolecular forces, pendant groups, stiffening groups, and cross-linking (Balani et al., 2014). The polymer molecules in the amorphous region exist in a frozen state at lower temperatures, which is commonly referred to as the glassy state. During heating, the polymer chains exhibit mobility, resulting in increased flexibility and softness, transitioning the polymer into a rubbery state. The glass transition is a phenomenon that specifically takes place in the amorphous region of polymers. It is important to note that the crystalline region of polymers remains unaffected during this transition. At the temperature Tm, the ordered polymer chains undergo a transition to a disordered phase, resulting in the transformation of the plastic from a solid state to a liquid state (Hale et al., 2020). Semicrystalline polymers are the only type of polymers that have a true Tm, while amorphous polymers only have a Tg. The measurement of the Tg and Tm of plastics can be conducted using DSC. This technique involves monitoring the heat flow associated with phase transitions as the temperature changes (Müller & Michell, 2016). The activation energy is a crucial factor in determining the temperature at which the thermal degradation of plastics is initiated. Thermal degradation can lead to both molecular reduction and enlargement due to chain scission and cross-linking (Crawford & Quinn 2017).

2.6

Conclusion

The degradation and fragmentation of MPs is influenced by various structural, physical, chemical, and thermal properties of MPs. The accurate assessment of MPs’ properties, including shape, size, polymer compositions, and functional groups, plays a critical role in understanding the behavior and bioavailability of MPs in various environments. This understanding provides valuable insights for the development of innovative strategies and regulations aimed at better controlling and remediating MP pollution. The presence of crystallinity affects physical properties such as the density and permeability of MPs. The vulnerability to oxidative degradation and fragmentation during weathering is determined by the degree of crystallinity. The size of molecules in plastics plays a crucial role in determining their mechanical, thermal, and biological degradation characteristics. Moreover, the decreasing size of MPs results in an increase in the harmful effect on organisms. Surface morphology can be helpful in deducing the origins of MPs by analyzing their shapes, compositions, sizes, and colors. The degradation of MPs is greatly influenced by the presence of chemical bonds and functional groups that exhibit resistance to degradation, such as carbon–carbon and ester bonds. The distribution and bioavailability of MPs are affected by their density, which leads to different ingestion patterns among organisms

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3 Degradation of Plastics and Formation of Primary and Secondary Microplastics Sudeep Kumar Mishra1, Sanket Dey Chowdhury1, Puspendu Bhunia1, Arindam Sarkar2, Rao Y. Surampalli3, and Tian C. Zhang4 1

Environmental Engineering, School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India Water Resources Engineering, School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India 3 Global Institute for Energy, Environment, and Sustainability, Lenexa, KS, USA 4 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 2

3.1

Introduction

Plastics are a type of synthetic polymers characterized by their long chains. They are extensively utilized in many industries due to their exceptional properties, such as being lightweight, durable, and flexible. Plastics also offer advantages such as electrical and thermal insulation, resistance to corrosion, and affordability (Zhang et al., 2020). Statistics indicate that the production of plastic products reached a staggering 360 million tonnes in 2018, with projections estimating a further increase to 500 million tonnes by 2025 (Bai et al., 2019; Huang et al., 2020). Once they reach the end of their useful life, the majority of plastics are carelessly dumped into the environment as plastic waste through various means, with only a minuscule portion of plastics being actually recycled. Due to inadequate management and disposal methods, a significant quantity of plastic trash infiltrates the environment via several channels, resulting in severe environmental pollution issues (Geyer et al., 2017). Plastics are commonly regarded as biologically and chemically inert substances that exhibit long-term stability in the environment. However, plastics are intentionally engineered to possess long-lasting durability; thus, conventional plastics have a high level of resistance to degradation in most cases. Unless they are made of special biodegradable raw materials, most plastics are classified as nonbiodegradable plastics. Thus, these plastics may have a projected lifespan of several hundred to several thousand years, depending on their specific qualities and the environmental circumstances in which they are found (Lambert & Wagner, 2018). Statistical research has shown that microplastics (MPs) account for 92.4% of plastic waste and are mostly composed of polyethylene (PE), polystyrene (PS), and polypropylene (PP) (Figure 3.1) (Santana et al., 2016). The breakdown of plastics can occur through various environmental weathering processes, including photo degradation, chemical degradation, thermal degradation, thermo-oxidative

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3 Degradation of Plastics and Formation of Primary and Secondary Microplastics

Figure 3.1

Major Types of Plastic Polymer

degradation, and biodegradation. The process of degradation involves a series of chemical reactions that lead to the disintegration of plastic polymers. It is an essential technique used to effectively eliminate plastic pollution. The main modes of polymer breakdown, caused by either chemical or biological factors, are hydrolysis and oxidation (Smith, 2005). Plastic degradation is categorized as processes involving both biotic and abiotic intervention (Lambert et al., 2013). The natural environment is hostile to the degradation of plastics because of their hydrophobicity, stable covalent bonds, and nonattackable functional groups (Smith, 2005). The degradation of plastic polymers in the environment is influenced by their physical and chemical properties. The properties of these substances encompass their dimensions, as well as their chemical composition and molecular arrangement (Goel, 2017). This deterioration results in the development of plastic pieces, which are classified as MPs when their size is less than 5 mm (Thompson et al., 2004). This suggests that the fundamental nature of MPs is plastic, and the primary origin of MP formation is the breakdown of plastic in the natural environment (Alimi et al., 2020). The breakdown of MPs and plastics is closely interconnected (Liu et al., 2022). During the degradation process, it is necessary to convert both substances into monomers prior to mineralization. It is essential to understand that the breakdown of plastics results in a significant quantity of MPs and nanoplastics. Furthermore, the primary objective of both plastic and MP degradation is to break them down into alternative degradation byproducts, such as water, carbon dioxide, and methane (Figure 3.2). However, a mere 21% of plastic has undergone recycling or incineration (Law, 2017), leaving the remaining portion to undergo weathering and fragmentation into MPs. There are two sources of MPs: primary and secondary. Primary MPs originate from raw polymer materials produced for industrial and specific domestic uses (Wang et al., 2021).

3.1 Introduction

Figure 3.2

General Process of Plastic Degradation

Primary MPs are commonly found in cosmetics, toothpaste, clothing, personal care products, textiles, cleaning products, and plastic industries. The degradation of larger plastic matters into small plastic debris through physical, chemical, and biological processes is a significant secondary source of MPs (Wang et al., 2021). Li et al. (2018) have conducted a review on the origins of secondary MPs, which include industrial resin pellets, trawl nets, and household supplies. Degradation results in the fragmentation of macroscopic size plastics waste leading to the release of secondary MPs into various environments. In general, secondary MPs are the most commonly found type of MPs in the ecosystem. The degradation of primary and secondary MPs primarily affects their physical and chemical properties, including surface morphology, color, particle size, crystallinity, and density (Figure 3.3) (Guo & Wang, 2019). The substantial specific surface area of MPs in nature enhances their propensity to attract other substances, thereby impeding further degradation (Liu et al., 2022). The pollution caused by MPs has become a worldwide topic of growing concern (Abel et al., 2018). MPs are considered detrimental to both animals and people because of their long-lasting presence and ability to accumulate in organisms. MPs may include other hazardous compounds that are either intentionally added during production, such as pigments, plasticizers, and flame retardants, or accumulated from the environment, such as pathogens, polycyclic aromatic hydrocarbons, and metals (Andrady, 2011). MPs are polymers and therefore follow similar degradation pathways as other polymers. The breakdown of plastic waste in the environment is a significant process that leads to the creation of MPs. A comprehensive understanding of the methods and mechanisms involved in plastic degradation is essential due to the synergistic effects of various degradation methods in both natural environments and potential engineering applications. Moreover, to ascertain the fate and consequences of plastics, it is vital to comprehend their degradation and persistence in the environment. Nevertheless, our understanding of this subject remains restricted and necessitates additional research. This chapter provides an analysis of the degradation processes by which different types of plastics transform into MPs. Furthermore, a sincere effort has been undertaken to compile and discuss the pathways traversed throughout the degradation of plastic in order to better understand the plastic degradation processes. Moreover, the toxicity of products and byproducts formed during the processes has been emphasized.

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3 Degradation of Plastics and Formation of Primary and Secondary Microplastics

Figure 3.3

3.2

Changes in the Properties of Plastics After Degradation

Physical and Mechanical Degradation

Plastics can undergo physical or chemical changes caused by factors like light, temperature, air, water, and mechanical forces. In most cases, physical degradation is likely to occur before biodegradation because of the limited bioavailability of plastics (Andrady, 2015). MPs undergoing physical degradation are illustrated in Table 3.1.

3.2.1

Photodegradation of Plastics

Photodegradation is widely acknowledged as the primary mechanism responsible for initiating plastic breakdown in the environment. The process of photodegradation of plastics typically occurs by solar irradiation, which triggers free radical-mediated processes. The primary causes of photodegradation are high-energy UV irradiation, e.g., UV-B (290–315 nm) and medium-energy UV-A (315–400 nm) (Liu et al., 2019a). Photodegradation of plastics in the air results in the generation of atmospheric MPs and nanoplastics, along with the emission of hazardous compounds like aldehydes (Paluselli et al., 2018). Polyethylene (PE): PE exhibits resistance to photodegradation as a result of the absence of chromophores. However, the occurrence of impurities or structural defects in the polymers during production or exposure to environmental conditions may serve as chromophores (Fairbrother et al., 2019). The carbonyl groups present in the PE backbone have the ability to function as chromophores. Moreover, the Norrish Types I and II reactions result in the formation of radicals, ketone groups, and end vinyl groups, which in turn lead to the cleavage of the main chain (Karlsson & Albertsson, 2002). Free radicals have the ability to combine with oxygen and form peroxy radicals. These peroxy radicals are

Table 3.1 Physical Degradation of Various Plastics

Polymera

Exposure conditions

Duration

Detection technique

Observations

Mechanism

References

LDPE, PP

Air and seawater

12 months

Instron universal materials testing machine

Decreases in ultimate elongation; Biofouling

Photodegradation

Pegram and Andrady (1989)

LDPE

Buried in river bank, suspended from a tree and, fastened to the bank

4 months

Universal materials testing machine

Decrease in elongation and tensile strength at break

Photodegradation

Williams and Simmons (1996)

PP

In sea water at 0.6 m depth

40 weeks

UV spectroradiometer,

Reduction in maximum extension and UV transmittance

Photodegradation

O’Brine and Thompson (2010)

PP, PE and PS

UV exposure in air, ultrapure water and seawater

3 months

FTIR, Raman, SEM

Alterations in functional groups; Detection of granular oxidation, flakes, and fractures on surfaces

Photodegradation

Cai et al. (2018)

Nylon, PE, PP, PET

UV exposure

6.5 months

TGA, SEM, AFM

Deterioration of the plastic material; Surface degradation characterized by the presence of granular oxidation, flakes, and fractures has been observed. Surface heterogeneity

Photodegradation

Iniguez et al. (2018)

PVC

thermal and UV exposure in seawater and air

210 days

SEM–EDX, surface area analyzer, FTIR

Alterations in pore size, volume, surface area, and morphologies; changes in functional groups and loss of weight

Photodegradation and thermal degradation

Tang et al. (2018)

PE

In soil, open air, and marine environment

3 years

Tensile testing machine, FTIR

Reduced tensile stress

Photodegradation and oxidation

Napper and Thompson (2019)

LDPE, PP, PS

Placed in rotating laboratory mixer with sediment added

24 hours

Visual inspection, fluorescence microscope, balance

The amount of MPs produced increases with the coarseness of the sediment.

Mechanical fragmentation

Chubarenko et al. (2020)

a PE: polyethylene; LLDPE: linear low density polyethylene; LDPE: low density polyethylene; HDPE: high density polyethylene; PS: polystyrene; PP: polypropylene; PVC: polyvinyl chloride; EPS: expanded PS; PC: polycarbonate; PA: polyamide; PET: polyethylene terephthalate; PUR: polyurethane.

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3 Degradation of Plastics and Formation of Primary and Secondary Microplastics

then transformed into a peroxide group by the process of hydrogen abstraction. The peroxide component breaks down into larger alkyl groups and hydroxyl radicals, which then accelerate the next series of reactions. The reaction sequence may result in the production of ketones, aldehydes, esters, carboxylic acids, and alcohols. In addition, polymers can undergo chain scission and cross-linking (Torikai et al., 1986). Polypropylene (PP): The lower stability of PP compared to PE can be attributed to the presence of tertiary carbon, which is more susceptible to oxidation (Weber et al., 2011). The photodegradation processes observed in PP are similar to those observed in PE. The presence of impurities in PP leads to the formation of chromophores, which facilitate the production of radicals upon exposure to UV light. After undergoing radical-mediated reactions, there is a propensity for the random fragmentation and recombination of chains, leading to the formation of degradation products characterized by a decreased molecular weight (He et al., 2019; Su et al., 2019). Polyvinyl chloride (PVC): PVC undergoes a rapid degradation process when exposed to UV light. This degradation involves the release of hydrogen chloride and the formation of short chains of conjugated unsaturation within the polymer. Unsaturated carbon–carbon (C=C) double bonds exhibit reduced stability and are prone to additional degradation when exposed to light. In a similar manner to PE and PP, the presence of chromophores in PVC resulting from impurities can lead to the absorption of UV light and the generation of free radicals. The formation of hydro-peroxides by free radicals can lead to the cleavage of double bonds in the backbone chain, ultimately resulting in the generation of smaller degradation products (Yang et al., 2018). A recent study has identified a new mechanism of degradation for PVC under environmentally relevant conditions. The process entails the creation of polyene structures, which are subsequently transformed into ketone and alcohol compounds through the action of O2 and OH radicals (Wang et al., 2020). Polystyrene (PS): PS is susceptible to photodegradation due to the presence of phenyl rings. When PS is exposed to UV light, the phenyl rings become excited and transition into a triple state. Excited benzene molecules may dissociate their phenyl group or transfer their triplet energy to the nearest carbon–carbon (C─C) or carbon–hydrogen (C─H) bonds. In the absence of oxygen, the breaking of a C─H bond leads to the formation of a polystyrene radical. The polystyrene radical undergoes conversion into a peroxy radical in the presence of oxygen. The peroxy radical subsequently undergoes a chemical reaction with the adjacent polystyrene molecule. The processes of chain scission and cross-linking lead to the synthesis of olefins, styrene monomer, and carbonyl compounds (Kumar et al., 2020). PE Terephthalate (PET): PET is composed of ethylene glycolate and terephthalate subunits that are connected by ester bonds in an alternating pattern. The photodegradation of PET results in the direct breaking of the ester link, producing CO2, CO, terephthalic acid, anhydrides, esters, and carboxylic acids (Fairbrother et al., 2019). PET may undergo photodegradation via radical reactions. Hydroperoxide is produced by oxidizing the CH2 groups that are next to the ester bond. Hydroxyl radicals, generated from the decomposition of hydroperoxide, may undergo chemical reactions with the aromatic rings present in the polymer backbone, resulting in the formation of hydroxyl terephthalate groups. Radical intermediates and other products have the ability to interact together to create chains that are connected together (Wong et al., 2020).

3.2 Physical and Mechanical Degradation

3.2.2

Thermal Degradation of Plastics

Thermal degradation is the process by which polymers break down as a result of increased temperature. Plastics may experience thermo-oxidative reactions when exposed to high temperatures. When an adequate amount of heat is absorbed by the polymer, surpassing the energy barrier, the long polymer chains may be fractured, resulting in the production of radicals (Pirsaheb et al., 2020). The radicals have the ability to undergo a reaction with oxygen, resulting in the production of hydroperoxide. This process is akin to the photodegradation of plastics, where they break down to create hydroxyl free radicals and alkoxy radicals. The reaction has the potential to self-propagate until the energy input ceases or inert products are created through the collision of two radicals. Thermal degradation can lead to changes in molecular size and structure through processes like chain scission and cross-linking (Crawford & Quinn, 2017). The temperature necessary for thermal degradation is determined by the thermal characteristics of plastics and the presence of oxygen (Crawford & Quinn, 2017). The melting point (Tm) and glass transition temperature (Tg) are significant thermal characteristics of polymers. Tg refers to the temperature at which the polymer undergoes a transition from a rigid, glassy state to a more flexible and elastic state. Plastics exhibit flexibility when exposed to temperatures above the Tg, but they lose their flexibility and become stiff when subjected to temperatures below Tg. This shift in behavior is attributed to alterations in molecular mobility (Rudin & Choi, 2012). The activation energy is the temperature at which the thermal deterioration of polymers begins. When exposed to oxygen, common plastics that contain hydrogen undergo exothermic oxidation at a temperature of around 200 C. Plastics having a higher Tm often need even higher temperatures for this process to occur (Kotoyori, 1972). The process of thermal deterioration of polymers has several applications: (a) Toapanta et al. (2021) used pyrolysis gas chromatography mass spectrometry (Pyr–GC/MS) to identify the different types of plastics found in environmental samples; (b) Arpia et al. (2021) found that when plastics are subjected to high temperatures, similar to pyrolysis, they can break down and produce syngas (carbon monoxide, hydrogen, and methane) or fuel oil; and (c) at low temperatures, thermal degradation may be used as a pretreatment method to enhance the subsequent biodegradation of plastics, comparable to oxidative degradation (Arpia et al., 2021; Zhang et al., 2020). Exothermic oxidation is improbable in the environment owing to its high-temperature requirement. However, the gradual thermal oxidation of plastics may occur in conjunction with photodegradation, particularly in areas such as pavements or beaches that are directly exposed to the Sun. Temperature and UV light may interact to accelerate the deterioration of plastics. In addition, higher temperatures can also enhance the pace of oxidative processes (Andrady et al., 2003). Furthermore, it was shown that elevated humidity levels decrease the amount of energy required to initiate the breakdown of plastics by heat (Kotoyori, 1972).

3.2.3

Mechanical Degradation of Plastics

Mechanical degradation is the process by which polymers deteriorate as a result of external forces. In the natural environment, external pressures might arise from the impact and erosion of plastics on rocks and sand due to the action of wind and waves. The process of

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freezing and thawing of plastics in aquatic settings may lead to the mechanical degradation of plastic polymers (Pal et al., 2018). The influence of external forces is contingent upon the mechanical characteristics of the polymers. Elongation at fracture, commonly referred to as fracture strain, indicates the capacity of a plastic product to withstand deformation without developing cracks. The elongation at break of various polymers ranges from 1% to around 900% (Crawford & Quinn, 2017). Plastics that have a lower elongation at break value are more prone to breaking into smaller pieces when subjected to external tensile pressures. Prolonged stress on plastics ultimately leads to the cleavage of polymer chains. Synthetic fibers, such as polyester, polyolefin, acrylic, and polyamide (PA), account for more than 60% of global fiber use. Mechanical degradation plays a crucial role in the deterioration of synthetic fibers. The act of washing clothes at home has been identified as an important contributor to the presence of MP fibers. This is likely because the synthetic fibers experience shear, abrasion, and impact stresses throughout the laundry process (Cesa et al., 2020). In addition, it was discovered that the deterioration of clothing might release MP fibers into the air, which is just as significant as the release of MP fibers during the laundry process (De Falco et al., 2020).

3.3

Chemical Degradation

Pollutants such as ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and volatile organic compounds (VOCs) in the atmosphere can either directly damage plastics or initiate the production of radicals through photochemical reactions, resulting in the degradation of plastics (Crawford & Quinn, 2017; Dey Chowdhury et al., 2023). O3 reacts with the unsaturated carbon–carbon (C=C) double bonds in the polymer, even at low levels of ozone concentration. The interaction between ozone (O3) and double bonds results in the cleavage of the polymer chain. O3 also undergoes reactions with saturated polymers, albeit at a slightly lower rate (Cheremisinoff, 2001). SO2 may undergo excitation when exposed to UV light, resulting in the formation of a highly reactive singlet or triplet state. This reactive state can then react directly with unsaturated carbon–carbon (C=C) double bonds or participate in a photochemical reaction with O2 to produce O3. NO2 is very reactive because it contains unpaired electrons that readily react with the unsaturated C=C double bonds in the polymer. NO2 reacts with O2 via a photochemical process, resulting in the production of ozone, much as SO2 (McKeen, 2021). The pH value and salinity of water are the two key chemical parameters that have a significant impact on the degradation process of plastic in aquatic environments. Significant amounts of H+ ions (acidic) or OH− ions (basic) present in a water-based environment have the potential to accelerate the breakdown of polymers that are prone to hydrolysis, such as PAs (Hocker et al., 2014). These two elements may also modify the surface of different kinds of plastics and MPs, so affecting their behavior in a water environment and their interaction with other components and contaminants in the water (Liu et al., 2019b). The degradation process initiated by ozone occurs when ozone is present in the air, resulting in the aging of polymers. Exposure of the polymer to ozone leads to the synthesis of several carbonyl compounds, including lactones, ketones, and aliphatic esters. Over time,

3.4 Biological Degradation

this process leads to the formation of vinyl, ether, and hydroxyl groups. Moreover, plastic waste can undergo degradation through chemical treatments using additives like nanomagnesium oxide (MgO), ethylene glycol (EG), calcium or zinc (Ca/Zn) stearate, and diethylene glycol (DEG) as a catalyst. These treatments rely on chemicals that have the potential to impact both human health and the ecosystem (Kasmuri et al., 2022).

3.4

Biological Degradation

The biological degradation of plastics is the process by which microorganisms induce the breakdown of plastic materials. Biodegradation is a fascinating field of study exploring the various ways in which nature breaks down substances. It involves bacterial degradation, fungal degradation, and combined biological degradation. There are various types of biodegradation, each with its own unique mechanism of action. Organisms have the ability to break down plastics by physical means such as biting, chewing, or breaking them down in the digestive system (Cau et al., 2020; Dawson et al., 2018; Mateos-Cardenas et al., 2020; Porter et al., 2019). Alternatively, plastics may be broken down by organisms through biochemical processes. Microorganisms, including bacteria, fungi, and insects, play a major role in the biological degradation of plastics (Table 3.2) (Crawford & Quinn, 2017). Various review publications (Pathak and Navneet, 2017; Sánchez, 2019; Wu et al., 2019) have discussed strains that possess the ability to biodegrade plastic, as well as the biodegradation routes. Table 3.2

Different Mode of Biodegradation of Plastics

Mode of biodegradation

Bacterial degradation

Fungal degradation

Combined biodegradation

Species

Polymer

References

Pseudomonas aeruginosa DSM 50071 Gut microbes of Yellow mealworm larvae

PS

Matjašicˇ et al. (2021)

PVC

Peng et al. (2020)

Gut microbes of Tenebrio molitor larvae

PS and LDPE

Li et al. (2024)

acinetobacter bacterium

PS

Wang et al. (2020)

Endosymbiotic bacteria in the citrus mealybug

PE

Ibrahim et al. (2021)

Zalerion maritimum

PE

Paco et al. (2017)

Fusarium oxysporum and Fusarium solani

polyester

Taniguchi et al. (2019)

Aspergillus flavus PEDX3

HDPE

Ibrahim et al. (2021)

Microbial Consortium No. 46; Ideonella sakaiensis 201-F6, and PETase and MHETase.

PET

Taniguchi et al. (2019)

Bacillus sp. and Paenibacillus sp.

PE

Park and Kim (2019)

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Conventional plastics often have limited bioavailability due to their solid structure, which restricts the polymer’s accessibility to potential degraders (Battin et al., 2016; Dey Chowdhury et al., 2022). Microorganisms are unable to directly use macromolecule polymers. At first, extracellular enzymes are required to decompose macromolecule polymers into smaller molecular compounds that may be absorbed by cells and then metabolized (Chen et al., 2019). The process of abiotic breakdown of plastics might enhance the biodegradation process by generating degradation products with a small molecular size and causing cracks and holes on the surface of the polymer (Wu et al., 2019). The biological degradation of MPs can occur in either an aerobic or an anaerobic environment (Miri et al., 2022). Plastics can undergo mineralization into CO2 and H2O in aerobic conditions and into CO2, CH4, organic acids, H2O, and NH4 in anaerobic conditions through extracellular and intracellular processes, promoting microbial biomass growth. However, the biodegradation of plastics in anaerobic conditions is less energetically favorable than that in aerobic conditions and may require a longer duration for complete mineralization (Gu, 2003). Using bacterial and fungal species in biodegradation treatment can help break down MPs without causing harm to the surrounding environment and organisms. Recent research has been conducted on the biodegradation of MPs in both aerobic and anaerobic environments. Therefore, biodegradation is regarded as the optimal choice for breaking down MPs as an ecofriendly and sustainable method. Plastics that can biodegrade have become widely accepted due to their eco-friendly nature and affordability in terms of the environment. Plastics and plastic-eating enzymes/microbes must be collected for full destruction under certain circumstances such as appropriate temperature, pH, optimal humidity, and enough nutrition. Plastics fragments and MPs should be extracted from soil, water, and sediment for biological depolymerization and fermentation to produce useful compounds (Delacuvellerie et al., 2019). Research found that sediment and soil microorganisms in marine and terrestrial environments had a limited ability to biodegrade waste, particularly plastics, owing to low levels of oxygen and light availability (Harrison et al., 2012). In addition, there are certain challenges related to biotechnological applications that still require a comprehensive understanding, such as the potential toxicity of byproducts on microorganisms. The identification of intermediate compounds that have the potential to inhibit further metabolism is still not fully understood (Wilkes & Aristilde, 2017). The degradation of plastics, encompassing chemical, physical, and biological processes, has been summarized in Figure 3.4. The process of microbial biodegradation of plastics involves multiple steps. First, there is the initial degradation of polymers, where large polymeric structures are broken down into smaller particles. Following that, the polymers are further degraded into oligomers, dimers, and monomers. Finally, the microbial biomass facilitates the mineralization of MPs (Blair Espinoza, 2019). The extracellular enzymes produced by microbes, including lipase, esterase, laccase, lignin peroxides, and manganese peroxides, play a crucial role in enhancing the hydrophilicity of plastic polymers. These enzymes convert the polymers into functional groups such as carbonyl or alcohol groups, which promote microbial attachment and facilitate biodegradation (Shahnawaz et al., 2019; Taniguchi et al., 2019). Hydrolases, including esterases, lipases, poly (3-hydroxybutyrate) depolymerases, and cutinases, are classified as extracellular enzymes. These enzymes function by breaking down plastic surfaces into smaller molecules (Sol et al., 2020). During the process of biodegradation, certain enzymes

3.4 Biological Degradation

Figure 3.4

A Schematic Diagram Showing the Processes Involved in the Degradation of Plastics

have the ability to selectively bind to particularly vulnerable bonds located in the side chain of polymers or chemical groups present on the polymer chain. This binding action leads to an increase in the breaking of the polymer chain. However, the diffusion of these particles into the polymer structure is improbable due to their size. Consequently, degradation is expected to primarily occur on the surface, leading to the formation of cracks. The process of assimilation occurs as a result of the integration action of monomers that are transported into the microbial cytoplasm and subsequently metabolized (Zettler et al., 2013). Mineralization is the complete degradation of molecules/compounds to form completely oxidized metabolites (CO2, H2O, N2, and CH4) (Dey Chowdhury et al., 2023; Zettler et al., 2013). When mineralization is not fully achieved, biotransformation takes place, resulting in the production of organic and an inorganic metabolites or transformation products (Singh & Sharma, 2008). As to the European Standard EN 17033 of 2018, established by the European Committee for Standardization, plastic is considered biodegradable if more than 90% of the material is converted into CO2 during a span of 2 years, at temperatures ranging from 20 to 28 C. Cpolymer + O2

CCO2 + Cbiomass + Cresidual polymer

In their study, Fleming et al. (2017) examined the intricate interactions among various surfaces that are conducive to the colonization of microorganisms and the subsequent formation of biofilm (Fleming et al., 2017). The attachment processes exerted on MP biofilm are associated with various phenomena, namely: (a) biofouling, (b) degradation of plasticizers, (c) attack on the polymer’s backbone, (d) hydration, and (e) penetration of organisms into the polymer structure. The high surface-to-volume ratio in small plastic particles allows these processes to impact the aging of MPs and enhance biodegradation (Sivan, 2011). The breakdown of plastics through the action of external enzymes, such as hydrolysis and oxidation, leads to the breaking of polymer chains. This process produces shorter polymer chains and small fragments, such as oligomers, dimers, and monomers. When the molecular weight of these degradation products is sufficiently low, microorganisms may consume them (Chen et al., 2019).

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A number of favorable conditions must exist for effective biodegradation, including the presence of suitable enzymes and metabolic pathways in prospective microbial degrading organisms. To enhance biodegradation, it is necessary for environmental parameters such as pH, salinity, temperature, and moisture content to be favorable (Gong et al., 2012). Regarding plastics, it is necessary for their physical characteristics to enable the adhesion of microorganisms to their surface, as well as the structure of the polymer, including its chemical bonds. Furthermore, it is important to note that the biological reaction should not be influenced by the degree of polymerization or the degree of branching. The enzymatic degradation rate of polymers is influenced by various factors including the amorphous and crystalline regions, crystal size, and lamellar thickness. One example is the polyhydroxyalkanoates depolymerase enzymes, which have been documented to primarily hydrolyze chains in the amorphous state on the surface of fragmentation films. This is then followed by the erosion of chains in the crystalline state (Shabbir et al., 2020). Typically, synthetic polymers such as PE, PP, and PS exhibit a slow degradation rate (Weinstein et al., 2016). An illustration of this can be seen in the case of Enterobacter and Pseudomonas consortia derived from cow dung. These consortia displayed improved biodegradation of PE and PP, resulting in a weight loss of up to 15% over a period of 120 days (Skariyachan et al., 2022). Ru et al. (2020) conducted a comparative analysis of microbial metabolic pathways associated with synthetic organic plastics of varying biodegradability, namely PE, PP, PS, and PVC.

3.5

Degradation Pathway

For plastics, the degradation pathways and resulting products vary based on the type of polymer, ultimately resulting in the formation of smaller polymer fragments. Certain types of MPs have the potential to degrade entirely under normal environmental conditions, although this process can take an extensive amount of time, spanning hundreds of years. Degradation of PE: PE is a kind of plastic that is made up of long chains of hydrocarbon molecules and can be melted and reshaped when heated. Significant variations in the physical characteristics of LLDPE, LDPE, and HDPE blown films have been noted. PE, although being the most inert of the polyolefins, undergoes gradual degradation in the natural environment (Gardette et al., 2013) via the following major routes. Photo- and Thermal Degradation of PE: The primary structure of PE consists only of C─C single bonds, which are resistant to hydrolysis and photooxidative destruction because they lack UV–visible chromophores. An increased rate of photooxidation was observed in LDPE compared to HDPE. This can be attributed to the higher occurrence of reactive branch points in the low-density polymer. In the absence of sunlight, the thermal oxidative degradation of PE does not occur at significant rates at temperatures below 100 C. The role of light in photooxidative degradation is limited to initiating chain reactions. As a result, similar product distributions are observed in both photochemical and thermal processes. The current understanding of the photodegradation mechanism responsible for the primary pathways of PE degradation is well-established and can be summarized, as

3.5 Degradation Pathway

─ CH2 ─ CH2 ─ CH ─ CH2 ─ CH2 ─

hv, O2

H

H

─ CH2 ─ CH2 ─ C ─ CH2 ─ CH2 ─

─ CH2 ─ CH2 ─ C ─ CH2 ─ CH2 ─

O ─ OH

O* OH

hv

─ CH2 ─ CH2 ─ C ─ CH2 ─ CH2 ─

Norrish II, hv

H ─ CH2 ═ CH ─ CH2 + ─ CH2 ─ CH2 ─ C ─ CH3

O

O CH2 ═ CH2 + Acetone and vinyls

H

─ CH2 ─ CH2 ─ C + ─ CH2 ─ CH2 O Norrish I

─ CH2 ─ CH2 ─ C ─ CH2 ─ CH2 ─ OH

Figure 3.5

Carboxylic acids, esters, lactones

Primary Pathway of PE Degradation

depicted in Figure 3.5. The process of light absorption by chromophoric defects leads to the creation of radicals. These radicals can undergo various reactions, such as the abstraction of a hydrogen atom from the macromolecular chain, addition to an unsaturated group (also known as a cross-linking reaction), or addition to oxygen (Carpentieri et al., 2011). Hydroperoxides are generated as the first photoproducts. Upon formation, these entities have the ability to undergo decomposition through the cleavage of the relatively weak O─O bond. This process results in the production of a macro-alkoxy compound and a hydroxyl radical, denoted as HO•. The alkoxy macroradical serves as the crucial intermediate in the reaction. The radical can undergo various reaction pathways, including β-scission where the main chain is cleaved to produce aldehydes, hydrogen abstraction without chain cleavage to form hydroxyls, and a cage reaction between the pair of radicals formed, specifically the macro-alkoxy radical and hydroxyl radical HO•. The second reaction yields chain ketones. It is important to note that a recent proposal suggests that ketones can be generated through a reaction that does not require the decomposition of hydroperoxides. The photochemical reactivity of ketones is manifested through Norrish Type I or Type II reactions (Edge et al., 1991). The introduction of carbonyl defects into PE through oxidative reactions can result in Norrish Type I reactions (Figure 3.5). These reactions involve photochemically induced homolytic cleavage, leading to the formation of free radical intermediates. In addition, Norrish Type II reactions can occur, where intramolecular γ-H abstraction produces ketones and vinylidenes (Figure 3.5) (Norrish & Bamford, 1937). HDPE, LDPE, and LLDPE, despite having similar chemical compositions, exhibit distinct variations in their crystallinity levels. The degradation rate is significantly affected by the amorphous fraction of the polymer. Therefore, the degradation rate is significantly reduced for crystalline HDPE due to its limited chain mobility, which enhances radical recombination while suppressing radical propagation reactions. Biodegradation of PE: PE is considered nonbiodegradable due to its high hydrophobic level and high molecular weight. The process of making PE biodegradable involves the

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modification of its molecular weight, crystalline level, and mechanical properties, which are responsible for the resistance of PE toward degradation (Krupp & Jewell, 1992). The hydrophilic level of PE can be enhanced, and its polymer chain length can be reduced through oxidation, making it more susceptible to microbial degradation. The biodegradation of PE is understood to take place through two distinct mechanisms: oxo-biodegradation and hydro biodegradation (Bonhomme et al., 2003). The strains possessing hydrophobic surfaces may have a significant impact on the initial colonization of the polymer. It has been suggested that the interaction between bacterial cells and PE is influenced by the hydrophobic nature of the PE surface. Specifically, it is believed that the higher the hydrophobicity of the bacterial cell surface, the greater the interaction with PE (Hadar & Sivan, 2004). Another metabolic adaptation that is significant in polymer colonization involves the synthesis of surfactants. Surfactants are molecules that facilitate the attachment of microorganisms to hydrophobic surfaces. According to Harshvardhan and Jha (2013), Bacillus pumilus M27, marine bacteria (Kocuria palustris M16, and Bacillus subtilis H1584) utilize the PE surface as a carbon source. These microorganisms are able to extract carbon from the PE surface. The initial stage of PE biodegradation involves a concurrent process of molecular weight reduction. Upon reducing the size of the molecule, it becomes necessary to undergo oxidation to convert the hydrocarbon into a carboxylic acid that can be metabolized through β-oxidation and the Krebs cycle (Albertsson et al., 1987). Degradation of PP: PP is a type of thermoplastic material that finds extensive use in various applications such as packaging, labeling, textiles, and more. PP is widely utilized in the automotive industry due to its excellent process ability and cost-effectiveness. It is one of the most extensively produced polymers. PP degradation via a few major routes is briefly discussed below. Photo- and Thermal-degradation of PP: The pristine PP material exhibits excellent resistance to photooxidation and thermal oxidation when exposed to moderate temperatures. However, PP is susceptible to the effects of different external aging environments, including heat, light, and radiation. As a result, it has a lower service temperature compared to other materials. When PP is subjected to elevated temperatures or exposed to an irradiation environment, the tertiary hydrogen atoms within the PP chains become vulnerable to oxidation by oxygen (Wanasekara et al., 2011). The oxidation of PP is widely recognized to be influenced by both light and temperatures when exposed to outdoor aging conditions. PP can undergo photodegradation due to the impact on multiple molecular chains within the wavelength range of 310–350 nm (Zhao & Li, 2006). The wavelengths of sunlight that exceed 290 nm and reach the Earth’s surface have the capability to initiate the degradation process, leading to discoloration, chalking, and embrittlement of PP. The process of photooxidation of PP is illustrated in Figure 3.6. The degradation of polyolefins through photochemical processes is attributed to a range of impurities. The susceptibility to photodegradation is contingent upon the characteristics of the absorbing impurities and, as a result, varies with the wavelength. The presence of impurities and extraneous groups in the PP material results in the absorption of UV light and the formation of alkyl radicals on the polymer chains through hydrogen abstraction.

3.5 Degradation Pathway

Figure 3.6 The Photodegradation Pathway for PP

H ─ CH2 ─ C ─ CH3 CH3

O ─ CH2 ─ C ─ CH2 ─ + H2O ·CH3

OO·

OOH

─C─

─C─

CH3

CH3

O· ─ CH2 ─ C ─ CH2 + HO′ CH3

Biodegradation of PP: The degradation of polyolefins in the natural environment is a slow process that begins with environmental factors and is subsequently facilitated by microorganisms (Sudhakar et al., 2008). PP exhibits high hydrophobicity due to its high molecular weight and lack of active functional groups. In addition, the continuous chain of repetitive methylene units in PP contributes to its resistance to biodegradation. This is because the formation of biofilm or attachment of microorganisms on PP is very limited. In order to render polyolefin biodegradable, it is necessary to enhance their hydrophilic properties or decrease their polymer chain length through oxidation, thereby making them more susceptible to microbial degradation. The application of various treatments, such as UV irradiation, thermal exposure, and chemical processes, results in the oxidation of the surface of the polymer, which leads to the formation of functional groups including carbonyl, carboxyl, and ester. The hydrophobicity of the surface is reduced, thereby promoting biodegradation (Singhania et al., 2012). There have been a limited number of studies conducted on the biodegradation of PP. Degradation of PET: The chemical structure of PET is composed of alternating ethylene glycolate and terephthalate subunits, which are connected through ester bonds. Aromatic polyesters, such as PET, are a significant group of polymers that have extensive usage in various industries. These polymers find applications in the production of fibers, films, and beverage containers, among others. PET is widely recognized as a highly suitable synthetic polymer for food packaging due to its exceptional compatibility with food products. The significance of PET residues in the waste stream lies in their exceptional resistance to both atmospheric and biological agents. Photo-Thermal Degradation of PET: The process of photodegradation of PET takes place when it is exposed to near-ultraviolet light. This exposure leads to chain scission through Norrish Types I and II reactions. The chemical structure of PET is composed of alternating ethylene glycolate and terephthalate subunits, which are connected through ester bonds. PET undergoes rapid degradation when exposed to UV light, resulting in a deterioration of its physical and mechanical properties. In addition, it develops a pronounced yellow coloration. The photooxidation of PET is believed to occur by forming hydroperoxide species via the oxidation of the CH2 groups adjacent to the ester linkages. The hydroperoxide species subsequently initiate the generation of photoproducts via various pathways. The ester groups present in the terephthalate moiety, along with the CH2 groups, have a notable impact on the photodegradation mechanism of PET.

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Figure 3.7

The Degradation Pathway for PET

The degradation of PET is initiated by the photolytic cleavage of an ester bond leading to the release of several compounds including CO2, CO, carboxylic acids, terephthalic acid, anhydrides, and esters (Figure 3.7). It is observed that higher yields of CO2 are typically found in aerobic environments. Both aerobic and anaerobic photodegradations adhere to a Norrish Type II mechanism. In this mechanism, an excited state carbonyl molecule extracts the α-H atom, resulting in the formation of carboxylic acid and vinyl chain ends. Hydroxy terephthalate groups can be formed when hydroxyl radicals, generated by the cleavage of the O─O bond in hydroperoxide, react with the aromatic rings in the polymer backbone in the presence of O2. The recombination of radical intermediates and products can result in the formation of cross-links and new chromophores. This process has the potential to cause polymer embrittlement and discoloration, although it does not necessarily lead to mineralization.

3.6

Degradation Products and Byproducts

The degradation of plastics occurs due to the contact and follow-up reactions, leading to changes in their surface characteristics and the formation of novel functional groups. The modified polymers nevertheless have an impact on the environment and living organisms. The scenario is characterized by dynamic and constantly shifting elements. PE, PP, and PET undergo deterioration at varying rates and via distinct mechanisms during the processes of photo, heat, and biodegradation. Typically, photo and thermal deterioration exhibit comparable characteristics. Photodegradation of PE leads to more distinct peaks in the infrared spectrum corresponding to ketones, esters, acids, and other compounds (Fotopoulou & Karapanagioti, 2019). Similarly, PP has the same characteristic, although it possesses a higher level of resistance against photodegradation. The process of photooxidation of PET includes the creation of hydroperoxide species by oxidizing the CH2 groups

3.7 Toxicity of Products and Byproducts

next to the ester bonds. These hydroperoxide species then generate photoproducts via several routes. The interaction between microorganisms and the production of biofilms varies among the three polymers. In general, the process of biodegradation leads to a reduction in carbonyl indices when the sample has previously undergone photodegradation due to UV exposure (Dey Chowdhury et al., 2022; Fotopoulou & Karapanagioti, 2019). The decomposition of MPs presents many distinct challenges when compared to the deterioration of regular plastics: (a) MPs, due to their small size, are not easily removed during wastewater treatment and subsequently introduced into the environment without an effective centralized collection method for degradation (Kundu et al., 2021; Rius-Ayra et al., 2021). Furthermore, their widespread distribution in the environment makes it challenging to collect them; and (b) MPs possess a large specific surface area and high adsorption capabilities (Chowdhury et al., 2022a, b). As they migrate in the environment, they tend to adsorb a significant amount of toxic substances, thereby increasing the difficulty of their degradation (Arpia et al., 2021; Chowdhury et al., 2023; Guo & Wang, 2019; Li et al., 2018). In general, the breakdown of MPs is not fundamentally different from the breakdown of regular plastics; however, the breakdown of MPs presents more additional difficulties compared to that of regular plastics. In general, superior degradation outcomes can be attained through the integration of abiotic and biodegradation methodologies (Ali et al., 2021). Abiotic processes in nature facilitate the degradation of plastics into small molecules, which are subsequently degraded into CO2, H2O, CH4, and other byproducts by natural organisms. It is imperative to acknowledge that the degradation of plastics generates substantial quantities of MPs and nanoplastics. Complete mineralization of plastics and MPs can be accomplished in the laboratory using advanced oxidation processes and pyrolysis techniques (Domínguez-Jaimes et al., 2021; Hu et al., 2021). However, the recovery and recycling of catalytic materials and the minimization of toxic and hazardous intermediates produced by these processes pose formidable obstacles.

3.7

Toxicity of Products and Byproducts

When assessing a degradation method, it is crucial to consider its impact on the environment. While our primary goal is to find more efficient ways to degrade MPs, we must also take into account the potential consequences of such degradation on the surrounding ecosystem and its inhabitants. MPs can serve as a carrier for harmful substances like dichlorodiphenyltrichloroethane and hexachlorobenzene, potentially entering the bodies of organisms that ingest it. Biotoxicity: The presence of nanotoxicity, carcinogenic toxicity, and endocrine disruption in MPs can be worsened by the production of photodegradation products. These hazards include nanoparticles, polymer fragments and chemical additives. Therefore, it is important to consider the ecological effects of MP degradation in the relevant environment. Research has shown that the process of photodegradation of PS MPs hinders the development and accumulation of the liver lipids in young grouper fish (Epinephelus moara). This is mostly caused by the build-up of MPs in their bodies and the release of

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endogenous pollutants (Wang et al., 2020). In contrast, an alternative investigation revealed that the detrimental impact on musculoskeletal development of Zebrafish Larvae caused by photooxidative degradation of PA MPs was mitigated. This was attributed to the fact that MP degradation regulates proinflammatory responses induced by macrophages and reduces harm to antioxidant systems and apoptosis (Zou et al., 2020). Production of Volatile Organic Compounds: Yamashita et al. (2009) investigated the emission of organic compounds resulting from the degradation of plastics. Specifically, they have established that VOCs are released during the degradation of plastics in particular environments (Royer et al., 2018; Yamashita et al., 2009). Furthermore, previous research has found a positive correlation between the rate of VOCs production and the specific surface area. This indicates that as plastics degrade, organic compounds are continuously released into the environment. The amount of VOCs produced is influenced by the degree of aging of the plastic debris, as oxidative photodegradation plays a role in this process (Lomonaco et al., 2020). These include noxious and deleterious substances such as acrolein, benzene, propanal, methyl vinyl ketone, and methyl propenyl ketone. The impact of these poisonous and destructive substances on the environment warrants more scrutiny (Lomonaco et al., 2020). For example, the degradation of polyolefins leads to the production of VOCs belonging to various chemical groups, such as lactones, esters, ketones, and carboxylic acids. This process reduces the molecular weight of the polymers and increases their likelihood of floating in the air. Many of the volatile compounds that are released take part in intricate photochemical reactions, which have diverse impacts on atmospheric photochemical processes (Williams & Koppmann, 2007). Aldehydes can undergo photodegradation in the atmosphere, resulting in the creation of MP particles in the air (Atkinson, 2000). Interaction of Biodegradation Products with Soil: The presence of MPs in soil has significant consequences for soil microbial structure and activity, as well as nutrient uptake by plants. In addition, MPs lead to alterations in soil physicochemical properties, as highlighted by recent studies (Hou et al., 2021; Sintim et al., 2021). The use of PE film, a commonly used agricultural material, will contribute to the accumulation of MPs in the soil. This can have varying degrees of impact on the soil and the organisms there, adding to the challenge of plastic degradation. Continued deterioration of MPs will introduce a higher concentration of nanoplastics into the soil, potentially causing a more significant effect on the soil’s organisms. Given the smaller size of nanoplastics compared to MPs, as well as their larger specific surface area, they have a greater ability to infiltrate organisms and crops, including the human body. Due to its increased specific surface area, nanoplastic has a higher likelihood of absorbing additional substances from the environment. These substances can then enter the food chain cycle alongside the nanoplastic, ultimately impacting the entire ecosystem. The use of seed film coating to protect seeds from disease and pests through the encapsulation of fungicides and/or insecticides has been extensively employed. This treatment technique results in an increased amount of plastic debris in the soil. Hence, it is crucial to examine the extent of degradation of these plastic fragments in the soil and their potential implications on the soil environment (Di Cesare et al., 2021). Research has indicated that the breakdown of plastic coatings in soil can differ and is influenced by several factors,

References

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3.8

Conclusion

This chapter explores the various processes involved in the degradation of plastics into primary and secondary MPs. Among different processes, UV radiation is mostly responsible for the onset of plastic degradation in the environment. Plastic polymer oxidation and chain scission occur during the breakdown, resulting in low molecular weight byproducts and physicochemical and mechanical characteristics alterations. In addition, a brief discussion about the degradation products/byproducts and their toxicity is included.

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Pathak, V. M., & Navneet (2017). Review on the current status of polymer degradation: A microbial approach. Bioresources and Bioprocessing, 4(1), 15. Pegram, J. E., & Andrady, A. L. (1989). Outdoor weathering of selected polymeric materials under marine exposure conditions. Polymer Degradation and Stability, 26(4), 333–345. Peng, B. Y., Chen, Z., Chen, J., Yu, H., Zhou, X., Criddle, C. S., … Zhang, Y. (2020). Biodegradation of polyvinyl chloride (PVC) in Tenebrio molitor (Coleoptera: Tenebrionidae) larvae. Environment International, 145, 106106. Pirsaheb, M., Hossini, H., & Makhdoumi, P. (2020). Review of microplastic occurrence and toxicological effects in marine environment: Experimental evidence of inflammation. Process Safety and Environment Protection, 142, 1–14. Paluselli, A., Fauvelle, V., Galgani, F., & Sempéré, R. (2018). Phthalate release from plastic fragments and degradation in seawater. Environmental Science & Technology, 53(1), 166–175. Porter, A., Smith, K. E., & Lewis, C. (2019). The sea urchin Paracentrotus lividus as a bioeroder of plastic. Science of the Total Environment, 693. Rius-Ayra, O., Biserova-Tahchieva, A., & LLorca-Isern, N. (2021). Surface-functionalised materials for microplastic removal. Marine Pollution Bulletin, 167, 112335. Royer, S. J., Ferrón, S., Wilson, S. T., & Karl, D. M. (2018). Production of methane and ethylene from plastic in the environment. PloS one, 13(8), e0200574. Ru, J., Huo, Y., & Yang, Y. (2020). Microbial degradation and valorization of plastic wastes. Frontiers in Microbiology, 11, 442. Rudin, A., & Choi, P. (2012). The elements of polymer science and engineering. Academic Press. Sanchez, C. (2019). Fungal potential for the degradation of petroleum-based polymers: An overview of macro- and microplastics biodegradation. Biotechnology Advances, 107501. Santana, M. F., Ascer, L. G., Custodio, M. R., Moreira, F. T., & Turra, A. (2016). Microplastic contamination in natural mussel beds from a Brazilian urbanized coastal region: Rapid evaluation through bioassessment. Marine Pollution Bulletin, 106, 183–189. Shabbir, S., Faheem, M., Ali, N., Kerr, P. G., Wang, L. F., Kuppusamy, S., & Li, Y. (2020). Periphytic biofilm: An innovative approach for biodegradation of microplastics. Science of the Total Environment, 717, 137064. Shahnawaz, M., Sangale, M. K., & Ade, A. B. (2019). Bioremediation technology for plastic waste. Springer. Singh, B., & Sharma, N. (2008). Mechanistic implications of plastic degradation. Polymer Degradation and Stability, 93(3), 561–584. Singhania, R. R., Christophe, G., Perchet, G., Troquet, J., & Larroche, C. (2012). Immersed membrane bioreactors: An overview with special emphasis on anaerobic bioprocesses. Bioresource Technology, 122, 171–180. Sintim, H. Y., Bandopadhyay, S., English, M. E., Bary, A., & y González, J. E. L., DeBruyn, J. M., ... & Flury, M. (2021). Four years of continuous use of soil-biodegradable plastic mulch: impact on soil and groundwater quality. Geoderma, 381, 114665. Sivan, A. (2011). New perspectives in plastic biodegradation. Current Opinion in Biotechnology, 22 (3), 422–426. Skariyachan, S., Taskeen, N., Kishore, A. P., & Krishna, B. V. (2022). Recent advances in plastic degradation–From microbial consortia-based methods to data sciences and computational biology driven approaches. Journal of Hazardous Materials, 426, 128086. Smith, R. (2005). Biodegradable polymers for industrial applications. CRC Press.

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Sol, D., Laca, A., Laca, A., & Díaz, M. (2020). Approaching the environmental problem of microplastics: Importance of WWTP treatments. Science of the Total Environment, 740, 140016. Su, Y., Zhang, Z., Wu, D., Zhan, L., Shi, H., & Xie, B. (2019). Occurrence of microplastics in landfill systems and their fate with landfill age. Water Research, 164, 114968. Sudhakar, M., Doble, M., Murthy, P. S., & Venkatesan, R. (2008). Marine microbe-mediated biodegradation of low-and high-density polyethylenes. International Biodeterioration & Biodegradation, 61(3), 203–213. Tang, C. C., Chen, H. I., Brimblecombe, P., & Lee, C. L. (2018). Textural, surface and chemical properties of polyvinyl chloride particles degraded in a simulated environment. Marine Pollution Bulletin, 133, 392–401. Taniguchi, I., Yoshida, S., Hiraga, K., Miyamoto, K., Kimura, Y., & Oda, K. (2019). Biodegradation of PET: Current status and application aspects. ACS Catalysis, 9(5), 4089–4105. Thompson, R. C., Olsen, Y., Mitchell, R. P., Davis, A., Rowland, S. J., John, A. W. G., McGonigle, D., & Russell, A. E. (2004). Lost at sea: Where is all the plastic? Science, 304, 838. Toapanta, T., Okoffo, E. D., Ede, S., O’Brien, S., Burrows, S. D., Ribeiro, F., Gallen, M., Colwell, J., Whittaker, A. K., Kaserzon, S., & Thomas, K. V. (2021). Influence of surface oxidation on the quantificationof polypropylene microplastics by pyrolysis gas chromatography mass spectrometry. Science of the Total Environment, 796(1), 148835. Torikai, A., Takeuchi, A., Nagaya, S., & Fueki, K. (1986). Photodegradation of polyethylene: Effect of crosslinking on the oxygenated products and mechanical properties. Polymer Photochemistry, 7(3), 199–211. Wanasekara, N., Chalivendra, V., & Calvert, P. (2011). Sub-micron scale mechanical properties of polypropylene fibers exposed to ultraviolet and thermal degradation. In MEMS and Nanotechnology, Volume 2: Proceedings of the 2010 Annual Conference on Experimental and Applied Mechanics (pp. 275–281). Springer, . Wang, C., Zhao, J., & Xing, B. (2021). Environmental source, fate, and toxicity of microplastics. Journal of Hazardous Materials, 407, 124357. Wang, X., Zheng, H., Zhao, J., Luo, X., Wang, Z., & Xing, B. (2020). Photodegradation elevated the toxicity of polystyrene microplastics to grouper (Epinephelus moara) through disrupting hepatic lipid homeostasis. Environmental Science & Technology, 54(10), 6202–6212. Weber, R., Watson, A., Forter, M., & Oliaei, F. (2011). Persistent organic pollutants and landfills – A review of past experiences and future challenges. Waste Management & Research, 29(1), 107–121. Weinstein, J. E., Crocker, B. K., & Gray, A. D. (2016). From macroplastic to microplastic: Degradation of high-density polyethylene, polypropylene, and polystyrene in a salt marsh habitat. Environmental Toxicology and Chemistry, 35(7), 1632–1640. https://doi.org/10.1002/ etc.3432 Wilkes, R. A., & Aristilde, L. (2017). Degradation and metabolism of synthetic plastics and associated products by Pseudomonas sp.: Capabilities and challenges. Journal of Applied Microbiology, 123(3), 582–593. Williams, A. T., & Simmons, S. L. (1996). The degradation of plastic litter in rivers: Implications for beaches. Journal of Coastal Conservation, 2(1), 63–72. Williams, J., & Koppmann, R. (2007). Volatile organic compounds in the atmosphere: an overview. In R. Koppmann (Ed.), Volatile organic compounds in the atmosphere (pp. 1–32). Blackwell Publishing Ltd.

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Wong, J. K. H., Lee, K. K., Tang, K. H. D., & Yap, P. S. (2020). Microplastics in the freshwater and terrestrial environments: Prevalence, fates, impacts and sustainable solutions. Science of the Total Environment, 719, 137512. Wu, X., Pan, J., Li, M., Li, Y., Bartlam, M., & Wang, Y. (2019). Selective enrichment of bacterial pathogens by microplastic biofilm. Water Research, 165, 114979. Yang, H., Ma, M. G., Thompson, J. R., & Flower, R. J. (2018). Waste management, informal recycling, environmental pollution and public health. Journal of Epidemiology and Community Health, 72(3), 237–243. Yamashita, K., Yamamoto, N., Mizukoshi, A., Noguchi, M., Ni, Y., & Yanagisawa, Y. (2009). Compositions of volatile organic compounds emitted from melted virgin and waste plastic pellets. Journal of the Air & Waste Management Association, 59(3), 273–278. Zettler, E. R., Mincer, T. J., & Amaral-Zettler, L. A. (2013). Life in the "plastisphere": Microbial communities on plastic marine debris. Environmental Science & Technology, 47(13), 7137– 7146. https://doi.org/10.1021/es401288x Zhang, F., Zhao, Y., Wang, D., Yan, M., Zhang, J., Zhang, P., Ding, T., Chen, L., & Chen, C. (2020). Current technologies for plastic waste treatment: A review. Journal of Cleaner Production, 282, 124523. Zhao, H., & Li, R. K. (2006). A study on the photo-degradation of zinc oxide (ZnO) filled polypropylene nanocomposites. Polymer, 47(9), 3207–3217. Zou, W., Xia, M., Jiang, K., Cao, Z., Zhang, X., & Hu, X. (2020). Photo-oxidative degradation mitigated the developmental toxicity of polyamide microplastics to zebrafish larvae by modulating macrophage-triggered proinflammatory responses and apoptosis. Environmental Science & Technology, 54(21), 13888–13898.

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4 Advanced Techniques for Sampling, Quantification, and Characterization of Microplastics Chathura Dhanasinghe1, Chih-Ming Kao1, Pu-Fong Liu2, Rao Y. Surampalli3, Tian C. Zhang4, and Bashir M. Al-Hashimi5 1

Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan CPC Corporation, Kaohsiung, Taiwan 3 Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 4 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 5 King’s College, Strand Campus, London, UK 2

For decades, the use of plastic has grown exponentially. Being persistent (rarely degraded) and present in an array of shapes and densities, plastics become fragmented over time and have diffused/accumulated in various ecosystems (GESAMP, 2015; Rocha-Santos & Duarte, 2017). Plastic waste can be classified at the micro (less than 5 mm) or nano (less than 100 nm) levels and are referred to as microplastics and nanoplastics, respectively (Silva et al., 2022). Microplastics have been contributing to environmental pollution that negatively affects both abiotic and biotic communities, leading to many serious, short- and long-term ecological consequences (Alimi et al., 2018; Chen et al., 2020a; Fischer et al., 2016; Lee & Chae, 2021; Zhang et al., 2022). Therefore, it is imperative to monitor, detect, and remove microplastics from different environments, which, as the first step, requests a standardization of methodologies used for sampling, quantification, and characterization of microplastics in different environments/biota. While many works have been published regarding this topic (Lusher et al., 2017; Rani et al., 2023; Rodríguez-Seijo & Pereira, 2017; Silva et al., 2022; Stock et al., 2019; Xiang et al., 2022; Yang et al., 2021), new information has been accumulated recently and warrants an overview. Therefore, this chapter provides a non-exhausted review on sampling, detecting, identifying, and characterizing microplastic samples collected from soil, water, air, and biota, highlights the advantages and limitations of some relevant technologies, and identifies various areas that need more research in the future.

4.1

Screening

Microplastic accumulation in the environment is mainly caused by human activities and plastic waste that breaks down and fragments into tiny microplastic particles. The consumption and manufacturing of synthetic organic polymers falling within the specified size

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Primary Microplastic

Secondary Microplastic

Dust from vehicle tyres Personal care products that used microbeads

Dumped plastic carrier bags Fibers from clothing materials Dumped plastic bottles/food packaging

Figure 4.1 Primary and Secondary Microplastic with Their Common Source of Generation ((a, b, d, e and f ) TBD; (c) Brian Yurasits/Unsplash.com)

range is the primary cause of pollution. Microplastics are classified into two categories (Figure 4.1): primary microplastic, which is engineered plastic made for commercial and industrial use; and secondary microplastic, which is physically, chemically, and biologically processed plastic debris or shards of plastic produced from discarded plastic. Polyethylene, polypropylene, and polystyrene plastic from different industrial and cosmetic products are known examples. Primary microplastics enter the environment through sewage and household discharge due to their high context of synthetic textiles usage in cosmetics and industrial processes, plastic resin powder, and pellets used for air blasting (Akdogan & Basak, 2019). Secondary microplastics occur due to the discharge of municipal solid waste and its process, discarded plastic material, and other anthropogenic activities, which cause the most significant contribution when considering microplastic pollution; these dumped waste results in the spread of pollutants due to soil erosion, surface runoff, and wind dispersal (Horton et al., 2017). This is a primary classification based on the origin or source of the microplastics. It is necessary to identify the various locations where these microplastics are dispersed. Plastic discovered in the environment can be a direct indicator of microplastic. Apart from the fundamental classification, microplastics can also be classified based on their size, shape, color, and kind of polymer, which could provide useful information about microplastics. These are emerging fields that have most recently engaged to come up with precise quantification and identification. Due to its characteristics and widespread in the environment, it has been challenging for scientists to screen microplastics via a certain process. The subsequent environmental sample is screened for microplastics to see whether any are present. Because of its toxicity and ecological impact, screening is required. Identification

4.2 Sampling and Extraction

Sample collection Figure 4.2

Sample preparation

Analysis

Data interpretation

Step-by-Step Strategy for Well-Prepared Study

and analysis of plastic particles less than 5 mm are part of the screening process. The size of microplastics makes it challenging to tell whether they are present in an environment by visual inspection alone. If a surface inspection yields no positive results, the environment cannot be reported or recorded as microplastic free. Screening will assist in determining whether microplastics are present. Critical procedures that begin with sample collection and conclude with data interpretation are followed during the screening process (Figure 4.2). Samples can be obtained from aquatic, soil, and air samples. Sample preparation usually follows sample characterization, including drying, homogenization, sorting, aggregate dispersion, density separation, and digestion. To determine the microplastic, analysis is a crucial step. Various analytical methods are employed to examine microplastics in environmental samples. Listed below are a few well-known analytical methods for screening for microplastics. These analytical techniques are applicable alone or in combination to measure the quantity of microplastic. The aforementioned analytical techniques offer details on several microplastic-related areas. In addition, new treatments can be developed due to the expanding body of research on microplastics. To obtain more precise chemical and physical data, analytical techniques were used to characterize the microplastic. Filtration, density separation, and the microscopic method are helpful screening techniques if basic parameters such as size, shape, and density need to be determined. More chemical information, like composition, can be obtained through spectroscopic and thermal investigation methods. A more in-depth investigation is required for ecological and toxicological analyses, such as the composition of the type of treatment linked to the determined microplastic. Synthetic microplastics are derived from synthetic polymers and are recognized as a major source of environmental contaminants. These materials can be poisonous and dangerous for the biota and abiotic. Therefore, collecting as much information as possible about microplastic coexistence in the collected environmental sample is crucial.

4.2

Sampling and Extraction

Microplastics have spread throughout the aquatic, surface, subterranean, and atmospheric environments. In the environment, the density of the dispersed pollutant concentration varies. The aquatic environment contains a significant amount of microplastic due to poorly managed plastic entering water bodies; estimates of the amount of plastic that enters the ocean annually range from 4.8 to 12.7 metric tons (Jambeck et al., 2015). Sediment and soil samples also include high concentrations of microplastics. How microplastics are transported determines where they end up above and below ground, where the wind carries lighter particles and denser particles are buried deeper in the soil layer. As a result, sampling is crucial in determining the amount of microplastic.

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The particular environment may affect the sampling technique. A set of recognized standard procedures must be followed while gathering samples for analysis, which improves the sample’s quality and validity (Zhang, 2007). The extraction method is crucial to the study since it is challenging to identify microplastic in samples due to impurities. Water, sediment, biota, suspended matter, and organic material are the constituents of the sampled material. Microplastic fragments are extracted from the sample medium and purified in this process. In contrast, plastic is sorted or divided into several types according to its shape, size, and color in separation. Sample preparation and extraction methods for soil, sediment, and biota differ from those for aquatic samples owing to the complexity of the former; however, most extraction methods can be summarized. These matrices have established detailed approaches. The main discussion topics are samples from surfaces, aquatic, dust, sediment, and tissues.

4.2.1

Surface

Surface water, soil, and airborne particles are all considered the environment’s outermost layers among the samples collected from the surface. Microplastic particles that have formed on the surface due to long-term biological, chemical, and physical processes could result from anthropogenic activity or occur naturally. Less research has been done on terrestrial ecosystems, where most plastic trash is generated and collected due to a long-term buildup of microplastics that can accumulate in soil layers. Most studies have been conducted utilizing aquatic sources. Certain regions, like cities and farms, may see higher exposure concentrations. Because microplastics are highly exposed to humans and alter soil ecology, it is critical to identify and characterize them when they are present on surfaces (Kumar et al., 2020; Rillig and Lehmann, 2020). Although some research has found that the amount of microplastics in the terrestrial environment is higher than that in the aquatic environment, the true magnitude of this difference is unknown because there are not enough studies and analytical methods available (Zhou et al., 2020). Due to the complexity of soil, which includes organic matter, minerals, and varying soil grain sizes, detecting methods still need to be improved; thus, further development is required (Yang et al., 2021). The sample must be homogenous and representative for an environment to be more accurately represented. Some background information on the sampling area, such as its intended use, geology, wind patterns, and velocity, is necessary for designing the sampling location and procedures. A few sampling designs (Table 4.1) have been established during the past few years based on the study objectives (Zhang, 2007). Improved representation is possible with composite samples from specific subunits within the sample site. The microplastic technique analysis and spatial distribution determine sample size and number. The soil layer is separated into three layers: top, middle, and bottom. Sampling must be covered vertically in these cases to enable the determination of deposition and vertical dispersion. Current research has identified the top layer, which has been analyzed for 10 cm (Piehl et al., 2018; Scheurer & Bigalke, 2018), and the downward moment of microplastic in the undisturbed soil, which still needs to be analyzed (Rillig et al., 2017). The standard sample size ranges from 50 g to 4 kg, with water content taking into account the request to mean dry weight applicable. The standard allocation of sample weight exceeds 1 kg because of the preceding justification (Moeller et al., 2020).

4.2 Sampling and Extraction

Table 4.1

An Overview of Potential Sampling Procedures Based on the Research Aim

Approach

Judgmental sampling

Simple random sampling

Systematic grid sampling

Graphical presentation Sampling Area

Sampling Area

Sampling Area

Sampling Area

Transect sampling

Unaligned grid sampling

Stratified sampling

Sampling Area

Sampling Area

Sampling Area

Objective Sampling Point

Sampling Point

Sampling Point

Validation of an area that is known or suspected.

Impartial, homogeneous sampling with a randomly selected sampling site.

Sampling is carried out at a predetermined distance, and the sampling locations’ spatial distribution may be symmetrical, allowing one to determine the contamination gradient and, eventually, the source of the contamination.

Sampling Point

Sampling Point

Sampling Point

Sampling Point

Determine the degree of contamination in an area, construct concentration gradients, and measure the amount of contamination along linear features.

Enable adequate representation in the sampling area while identifying pollutants.

It is identifying the regions inside the sampling area that are contaminated.

According to the circumstances, there is an extensive range of possibilities for sampling tools, including shovels, scoops, stainless steel spoons, and core samplers for deeper horizon examination. Every piece of sample equipment is contaminant-free and spotless. Airborne particles pose a risk due to rapid transit far from the source and significant levels of human exposure. The dispersion of microplastics at varying elevations presents a range of

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microplastic properties. The sampling frequency, volume, position, and height will determine microplastic influences (Wright et al. 2021). Passive samplers, dry and wet decomposition filters, and filters with different porosities are used in sample collecting. Quartz fiber filters and high-efficiency particulate air filters are popular sampling filters (Bank, 2022; Sommer et al., 2018; Zhang et al., 2020). Before being analyzed in a lab, collected samples are kept free from microbial growth and contamination from external sources. Scholars worldwide have used various sample processing and analytical methods to compare data from various geographical areas and develop a comprehensive understanding of microplastics in soils and sediments. The dispersion, quantity, and ecological impacts of microplastics in aquatic, atmosphere, and terrestrial habitats must be understood to determine the appropriate extraction method. Microplastics are long-term sinks in sediments and soils (Willis et al., 2017). The first research study on microplastics in beach sediments was conducted in 1977 after a survey of 300 beaches in New Zealand and revealed the existence of virgin polyolefins in the form of plastic pellets (Gregory, 1978). Several techniques have been devised, from straightforward single-step extractions to intricate procedures based on magnetic, oleophilic, or electrophilic properties (Table 4.2). Because of the irregular state of the soil and the need for procedures for organic material digestion, extracting soil samples is more complicated than extracting them from sediments and sand (Rani et al., 2023). Table 4.2 Method of Extraction and Summarized Vital Characteristics Essential to the Process Method

Description

01. Pretreatment (sieving/ filtration)

For microplastics larger than 5 mm visible to the human eye, sieving is a recommended pretreatment process that extracts microplastics from soil, sand, and sediments. A stainless steel sieve (1–2 mm) extracts microplastics from air–dry soil samples (Yang et al., 2021). The amount of microplastics in samples, whether dry or wet, should be expressed as mass/volume. Filtration is an alternative to sieves for treating soil to retain particle size and shape. Filter arrangement can also control how easy it is to recover trapped polymers. In laboratories, conventional filtration techniques like vacuum or membrane filtration are used. Alumina, glass fiber, polycarbonate, cellulose acetate, cellulose nitrate, and nylon are examples of common filter membrane materials (Li et al., 2019; Lusher et al., 2020). The ideal filter material has pores that range in size from hundreds to tens of micrometers, which is determined according to the study.

02. Density separation

Density separation is required to determine the presence of microplastics in sediments. The sampled matrix’s separation is determined by the kind of sample and the available resources. The microplastics are extracted from their matrix using the varying densities of the microplastic polymers and the extraction solution. Because of the oxidation of organic materials during the second step, microplastic extraction and detection are usually troublesome. This methodology has been utilized in most research studies for the last 20 years. To differentiate between denser sand or sediments and lightweight microplastics, a density difference is typically utilized. Sediments and soils generally have a mean density ranging from 1.70 to 2.65 g/cm3. Microplastics are frequently extracted from intertidal sediments using NaCl since it is an economical and environmentally

4.2 Sampling and Extraction

Table 4.2

(Continued)

Method

Description

benign method. Denser polymers, however, cannot be separated because NaCl yields a solution with a density of just 1.2 g/cm3. The first stage of soil microplastic isolation is density separation, followed by organic matter digestion. Scientists have experimented with various salts to determine the appropriate density for microplastic extraction and flotation in cases where microplastic density is unknown. Adequate technique for type of microplastic Salt

Density g/cm3

NaCl

1.2

ZnCl2

1.5–1.8

NaI Sodium polytungstate

PET HDPE LDPE PVC PP PS PA ∗

☑

☑

☑

☑

☑

☑

☑

☑

☑

1.55–1.8 ☑

☑

☑

∗

☑

☑

☑

1.4–1.65 ☑

☑

☑

☑

☑

☑

Sodium dihydrogen 1.4–1.45 ☑ phosphate monohydrate

☑

☑

☑

☑

☑

CaCl2

1.3–1.35 ☑

☑

☑

☑

☑

☑

☑ ☑

☑

☑

☑

ZnBr2 dihydrate

1.7

☑

☑

☑

☑

☑

☑

☑

NaBr

1.37

☑

☑

☑

☑

☑

☑

☑

Lithium tungstate

1.62

☑

☑

☑

☑

☑

☑

☑

KI

1.7

☑

☑

☑

K(HCOO)

1.5

☑

☑

☑

☑

☑

☑

☑

NaCl/NaI

1.2/1.8

☑

☑

☑

☑

☑

☑

☑

Milli-Q water

1

☑

☑

☑

∗

03. Elutriation

Adequate/inadequate PET, polyethylene terephthalate; HDPE, high-density polyethylene; PVC, polyvinyl chloride; LDPE, low-density polyethylene; PP, polypropylene; PS, polystyrene; PA, polyamide; PU, polyurethane (Bank, 2022; Rani et al., 2023) A process called elutriation uses a stream of gas or liquid that flows in a direction that is typically opposite to sedimentation to separate particles according to their size, structure, and density. The main concept comes from the biological field (meiofauna extraction from sediments). Preparing the sample (splitting it into the appropriate size ranges) and calculating fluid velocity are required. This method was modified by Claessens et al. (2013) to extract microplastics using NaI from beach sands, resulting in a 97% reduction in the amount of NaI required. With a few tweaks, Zhu (2015) created an elutriation system that was straightforward to assemble. Owing to several inadequacies (water flow rate optimization and high sand recovery yield), (Continued)

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4 Advanced Techniques for Sampling, Quantification, and Characterization of Microplastics

Table 4.2 (Continued) Method

Description

modifications must be made to the process. Granulometric techniques, which have the advantages of handling high volumes of samples in a single run, significant recovery and viability, speed of operation, and replication, were used by Kedzierski et al. (2016) to optimize the elutriation process (Claessens et al., 2013; Kedzierski et al., 2016; Zhu, 2015). The setup and numerical model must be completed first, which determines the elutriation velocity of the fluid, determining that particle velocity must be customized according to particle size to restrict sand suspension during elutriation. The efficiency of this technique is expected to be lower in fine and/or organic-matter-rich sediments that can agglomerate or react with plastics, as it was developed and explicitly improved for sand. (Claessens et al., 2013)

(Zhu, 2015)

(Kedzierski et al., 2016)

Height

1.47 m

0.50 m

1.86 m

Width

0.15 m

5.06–10.16 cm

1.06 m

Sieve size

Top: 1 mm Bottom: 35 μm with support from a 1 mm mesh, the bottom mesh serves as a sample holder. 300 L/hr of water for 15 min.

Top: 3 mm

Top: 63 and 32 μm

385 L/hr and 5.06 cm in column width for 10 min

1.2 × 10−2 m/s and 1.9 × 10−2 m/s, for 5 min

Optimal condition

04. Pressurized fluid extraction (PFE)

Sample amount

0.5 L

0.5 L

50.5 g

Saline solution

NaI

—

—

Removal efficiency

93–98%

50%

92%

According to studies, microplastic extraction from waste materials, sediments, and soils can be done using PFE. Submicron particles can be analyzed theoretically, and the particle size of microplastics has minimal impact on this separation method (Fuller & Gautam, 2016). High pressures (3.5–20 MPa) and high temperatures (313–473 K) (Andreu & Picó, 2019) are used for the extraction of solid or semisolid materials using an organic solvent-based solvent extraction technique that was developed by Dionex Corporation in 1995. Matrix removal and microplastic enhancement can be completed in just one totally automated step due to this method. PFE combined with gravimetric quantification has been used to extract microplastics from industrial soil and municipal waste material. This process is completed in two stages: static extraction, which uses methanol at 100 C (eliminate all semivolatile organic substances); and dynamic extraction. At 180 C, dichloromethane (DCM) is used to recover the microplastic fraction

4.2 Sampling and Extraction

Table 4.2

(Continued)

Method

Description

from the residual matrix during the second extraction. DCM extracts are gathered, dried by evaporation, and then measured gravimetrically. This method yielded estimated mean recoveries ranging from 84% to 94% for several plastic types, including PE, PVC, and PP (Fuller & Gautam, 2016). Nevertheless, it also has drawbacks: it uses a highly toxic chlorinated solvent, has limited size information, is disruptive, does not provide information on microplastics larger than 30 μm, and residues from materials containing different microplastics must obtain appropriate FTIR spectra. Recently, this method was refined to analyze microplastics in biosolids utilizing double-shot Py-GC-MS without needing sample pretreatment or a preextraction cleanup phase. Overall plastic concentration was between 2.8 and 6.6 mg/g dry weight, with mass concentrations of polyethylene (PE), PVC, PP, PS, and polymethyl methacrylate (PMMA) ranging from 0.1 to 4.1 mg/g dry weight across all samples (Okoffo et al., 2020). 05. Magnetic separation

An external magnetic field, acid, and magnetic seeds have been used to create a new technique for extracting microplastics from water samples. By functionalizing iron nanoparticles with hydrophobic hydrocarbon tails (using hexadecyltrimethoxysilane (HDTMS)), the technique enables them to attach to microplastic surfaces and be extracted using a magnet. Sieved (mesh size 45 μm) benthic sediment loaded with microplastics (200 μm–1 mm; PP, PVC, PU, PS, PE) was used to test the technique (Grbic et al., 2019; Ouda et al. 2023). It was discovered that magnetic extraction worked better at getting rid of small microplastics. Nevertheless, soil particles may have prevented Fe–NPs from interacting with microplastics, which would have led to low sediment recovery rates. The nonspecific binding of nanomaterials may reduce their impact and the microplastics’ surfacearea-to-volume ratio, which makes them appropriate for drinking water treatment and post-density separation or digesting phases.

06. Electrostatic separation

Electrostatic separation can reduce sample bulk and eliminate biological components without changing particle properties. Korona–Walzen–Scheider (KWS) is a recycling industrial equipment that uses the electrostatic properties of plastics. Sand and soil have more conductive mineral particles than polymers, which is why the approach relies upon the different electrical conductivity of the studied material. The particles are charged by a high-voltage electrical field, which speeds up their discharge and causes them to land in a sediment collector. Less conductive polymers dissipate at a slower rate, stay attached to the drum, and eventually separate and fall into a different collection container. The separator cannot separate components unless well-dried and unconsolidated samples are used. Electrostatic separation is environmentally friendly and enables the creation of element-enriched fractions from biomass particles (10–500 μm). Recent validation research did point out some of the disadvantages of KWS, including the laborious sample-drying procedure, the challenge of controlling humidity conditions, and the occurrence of small particles and agglomerates in soil observation data. Electrostatic separation of microplastics requires further treatment procedures, such as digestion and density separation. Sediment loss is a disadvantage of electrostatic separation, which works best with large samples but does not require any chemical treatment. (Continued)

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Table 4.2 (Continued) Method

Description

07. Oil-extraction protocol

Oil-extraction approach extracts plastics from environmental samples using plastic polymers’ oleophilic characteristics. This technique helps remove microplastics from soil because it is nontoxic and does not rely on their specific density. To get the sediment and plastic to adhere to the oil, the procedure entails stirring dry sediment with water, adding oil, and then shaking again for 30 seconds. After that, the water is decanted in preparation for a vacuum filtration stage, in which the oil layer filters and treats the filters with reagent alcohol to get rid of oil residues. Digesting samples high in biomass is advised before beginning the oil-extraction technique (Crichton et al., 2017; Rani et al., 2023). However, there are several reasons why this could reduce recovery rates, including that reagent alcohol can cause high static electricity during examinations; some microplastics remain in the oil after rinsing; microplastics remain intact on filters and glass surfaces; recovery rates decrease with actual samples; and the formation of an emulsion when samples contain natural surfactants, which can result in low extraction yields. Several studies have explored other oils (canola oil, castor oil, olive oil, mineral oil, and NaCl + olive oil) to reduce the drawbacks of the first suggested technique (Kim et al., 2022; Lechthaler et al., 2020). Several soil types can be extracted using the oil separation process, which does not involve oxidation. On average, more than 90% of microplastics can be recovered. The recovery rate increases from low-density polymers to high-density polymers.

Improvements in results can be achievable by coupling multiple techniques for extraction with additional methods that are required depending on the chemical composition of the sample beside the ones discussed above.

4.2.2

Aquatic Samples

Due to the negligent discharge of industrial effluent and domestic sewage, most aquatic sources are known to be contaminated by microplastics, including seawater, precipitation, wastewater, and drinking water (Xiang et al., 2022). The distribution of microplastics in this environment is determined by the form, density, size, and shape of the particles, as well as site variables like weather, flow pattern, season, and basin morphology. Since the environment comprises sediment, water, and the surface layer, selecting the best representative sampling location is crucial (Stock et al., 2019). Sampling from the water column is more accessible, which explains why more research has been conducted; however, further sampling has since been considered. The environment’s microplastic dispersion can be understood by studying sediment and biotic sample data. Depending on the area of interest in the research, different aquatic samples are collected from various aquatic environments (Tables 4.3 and 4.4). Furthermore, due to the complexity of the environment’s distribution, the method that chooses the locations for collecting marine and beach samples is more straightforward to use than that for river sampling. A river’s width, depth, transect shape,

4.2 Sampling and Extraction

Table 4.3 Overview of Possible Sampling Approaches Dependent on the Research Objective in Aquatic Systems Aquatic environment

Sampling description

Marine/beach

Places with higher watermarks. Sample perpendicular to the shore, different distance to the sea and the high tide line.

River

Water surface and column: in the river channel, close to shore, from the cut bank or point bar, and the mouth

Lakes

Water surface, water column, and ground or the littoral

Table 4.4

The Profile of Aquatic Sampling, Along with the Appropriate Tools for Each Sample Type

Type of sample

Water samples

Sampling tools/types

Water surface

• •• • •• • ∗

Water column

Nets (larger/smaller mesh size which ranges 50–3,000 μm; 300 μm) – Surface to depth of 0.5 m: manta trawls, plankton, or neuston nets Rotate drum sampler—help of surface tension Continuous flow centrifuge (CFC)∗ Filter cascades with a fractionated pressure filtration

The water being pumped into system Riverbed/seabed—eel, drift or benthic nets Mid water levels—bongo nets, cascaded sieves, or steel sieves (centrifugal pumps, teflon pumps, or eccentric screw pumps tend to be used in particular water depths to deliver water to the system.). Sampling in the distinct depths consecutively—bed-load catcher; in a vertical profile, five samples can be obtained simultaneously.

Water volume—flow meter or acoustic Doppler current profilers or 3D hydrodynamic-numerical modeling used to measure water volume Sediment samples

Biota sample

On surface (0–30 cm)

trowels, spoons/tablespoons, shovels, or spatula

Sublittoral zone

grabber or a box corer

Undisturbed sediments

drill core or a Pürckhauer ground auger

• •• ••

by manta or bongo nets (planktonic and nektonic invertebrates), by trawls in different water levels (fish), by hand (e.g., bivalves or crustaceans), by electrofishing, by gill nets (freshwater environments)

Note: Can be stranded individuals or their feces may be collected.

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Atmosphere

Research vessel/Sampling boat

Water surface

Water body

Water column Sediment Biota

Figure 4.3

Different Sampling Locations Are Represented in the Aquatic Environment

bottom gradient, degree of anastomosis, braiding, and vegetation on the riverbanks are some characteristics that river sampling may consider when determining whether or not the river flow is naturally occurring. If the flow is affected by human activity, this may also need to be considered (Holzhauer et al., 2016). In general, sampling was conducted at various sites with predetermined depths near the bottom, center of the water column, and close to the water’s surface (Figure 4.3). The sampling location was decided upon following the research interest. Employing various technical procedures, samples from various states of aquatic systems are collected (Table 4.4). Depending on the research objective, biological samples may be gathered via grasps, traps, creels, or bottom crawling (benthic invertebrates). Sediment samples can be taken from the seafloor, rivers, beaches, or riverbanks, depending on the topic of the study. Different types of water, including freshwater, ocean, and wastewater, are present in recognized environments. Environmental variables and physical properties impact the dispersion of microplastics in the water column. Because freshwater and saltwater have differing densities, their distributions in the water column differ. Sample procedures vary across freshwater and marine environments (Masura et al., 2015), but there are notable differences in the amounts of organic and inorganic substances found in each. Depending on the kind of water, microplastics should be extracted using methods including filtering or sieving for drinking water and bottled water and digestion for samples containing organic matter (Yusuf et al., 2022). Clean Water Sample: Drinking water to seawater—various techniques, including adsorption, coagulation, membrane filtration, oxidation, and microbial degradation, can extract

4.2 Sampling and Extraction

microplastics from samples. Low organic matter samples can be extracted and removed using density separation; if more organic matter is present, organic matter digestion is used (Cerasa et al., 2021; Lastovina and Budnyk, 2021). The use of density separation using nonhazardous chemicals to identify microplastic polymer types has gotten the attention of researchers and has been studied lately (Barnett et al., 2021). This process creates solutions with different specific densities and polymer concentrations using nonhazardous chemicals such as ethanol, distilled water, and sugar. For instance, by assessing their capacity to float in a particular solution, LDPE and HDPE can be distinguished using the 7:11 blend of EtOH/H2O. Wastewater—Regarding the broad matrix of inorganic particles, bacteria, and organic components bound together by biopolymers, wastewater and sludge are complicated samples. Most research uses diverse sampling techniques and sample quantities, and they concentrate on distinct kinds of polymers. The source of microplastics in wastewater and surface waters is identified as personal care and cosmetic products (PCCPs), with sizes ranging from >0.1 μm to 500 μm) (Li et al. 2018). By combining vibrational spectroscopy and microscopy, micro-FTIR (μFTIR) enhances spatial resolution and makes it feasible to identify smaller plastic fragments. Detectors with FPA–μFTIR technology provide simultaneous high-resolution investigation for numerous particles. However, this process takes a long time and is susceptible to material aging and plastic inhomogeneity. FTIR may help detect irregular forms, track the extent of polymer deterioration, and recognize colored microplastics. Colored microplastics whose pigments may glow and obstruct Raman spectra may readily be identified using FTIR. One of the disadvantages of FTIR spectroscopy is that it takes much time and is prone to material aging and plastic inhomogeneity (Käppler et al., 2018; Zhao et al., 2015). Raman Spectroscopy: An analytical approach known as Raman spectroscopy, a vibrational spectroscopy method, provides a nondestructive way to identify microplastics. The method identifies a sample’s molecular vibrations based on its molecular structure and the associated atoms generating unique spectra for each polymer (Chen et al., 2020b). Similar to FTIR, Raman analysis can detect plastics, provide spectra of the composition of polymers, and allow the observation of local microscopic features as well (Xiang et al., 2022). Identifying microplastics as small as a few μm is possible with μFTIR, while μRaman (the spectrometer may be interfaced with a microscope) usually has higher spatial resolution potential (Cabernard et al., 2018; Fortin et al., 2019). Compared to FTIR, Raman spectroscopy has a significant potential for spatial resolution down to approximately 1 μm. Raman is better at recognizing nonpolar functional groups than FTIR (Käppler et al., 2016). Raman and infrared spectroscopy are complementing methods, where samples of microplastics can be preserved for subsequent examination due to the noncontact analysis. Collard et al. (2015) have proposed a new extraction technique for extracting microplastics from membranes based on hypochlorite digestion and ultrasonic treatment. This technique can prevent fluorescence and improve the identification of artificial particles in fish stomachs. Raman is capable of identifying plastics in various environmental matrices, although most of the research that currently has data on plastics focuses on water and sediments. Furthermore, Raman spectroscopy is sensitive to compounds in microplastics that are additive and pigment-based and may interfere with identifying polymer types (Xiang et al., 2022).

4.3.4

Thermal Analysis

The thermoanalytical method, which is applicable to identify microplastics, quantifies changes in the chemical and physical characteristics of polymers based on their thermal stability. Utilizing differential scanning calorimetry (DSC), one can effectively investigate the thermal characteristics of polymeric materials, leading to distinct features for the DSC of the material under consideration. Standard material must be used as reference

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material to cross-check the specifications to identify the polymer types based on the DSC characteristics obtained for the unknown polymer in the sample. While the polymers are being heated, thermogravimetry (TGA) measures the weight loss of the materials, while DSC measures the melting points of the materials (Fu et al., 2020). Combining DSC with TGA allows for the detection of polypropylene and polyethylene. However, PET, polyester, PVC, PA, and PU could not be identified using TGA and DSC together because of their overlapping phase transition signals (Shim et al., 2017). The combined application of TGA with solid-phase extraction (SPE) and thermal desorption gas chromatography–mass spectrometry (TDS–GC/MS) allowed for larger sample volumes and better resolution. PE was quantitatively identified using the TGA–SPE/TDS–GC/MS method after soil and mussel sample exposure (Dümichen et al., 2015; Moeller et al., 2020). PS and PMMA micro(nano)plastics showed notable recovery rates in quality control specimens at spiking levels ranging from 34.5 to 61.5 μg/g. Pyrolysis gas chromatography– mass spectrometry (Py–GC/MS) has been used to identify and measure micro(nano)plastics in plants (Li et al., 2021). Polyvinyl acetate, PS, poly(acrylonitrile butadiene styrene) (ABS), styrene-butadiene rubber (SBR), and PVC were detected in the bulk analysis of suspended solid particles and sediment. Plastics such as PE, PP, PVC, PS, PA, PET, and chlorinated or chlorosulfonated PE were identified as probable plastic particles by Py–GC/MS analysis from sediment samples (Cabernard et al., 2018; Hermabessiere et al., 2018). The most commonly used methods for identifying inorganic and organic compounds in microplastics are GC–MS and ICP–MS (inductively coupled plasma mass spectrometry). It may be concluded that thermoanalytical methods such as Py–GC/MS and TED–GC/MS have great potential for characterizing plastic fragments and increasing sample productivity. Up to three polymers’ relative % contributions can be estimated using advanced statistics, but weight-based estimates are not feasible (Shim et al., 2017).

4.4

Quantification

For research to get an understanding of numerous fields, including toxicology and distribution, identification and quantification are essential. A few identification techniques that can find microplastics in samples are covered in Section 4.3. Since microplastic is a synthetic polymer compound with a range of >1 μm and 1 μm due to its poor resolution and diffraction. Analysis of polydisperse particle samples is limited and necessitates sample preparation when using fluorescent dyes.

Larger fragments conceal smaller ones. Don’t differentiate materials. It is not advised for particles that settle gravitationally. Problems with some polymers, including PE, were superposed on the matrix breakdown, and no quantitative particle counting or size determination was done. Microplastic identification in environmental samples faces limitations due to potential overlap between fusion peaks, inability to count particles, and size determination. The elemental sensitivity is limited, and there are specific requirements for sample preparation, such as fluorescent dyes or labels.

Attenuated total reflectance

•• •• ••

Surface morphology Stiffness Adhesiveness Hydrophobicity Conductivity Work function

100 nm

• •

SEM

Morphology/physicochemical analysis

1–100 nm

Py-GC-MS

Quantification and identification of polymers

1 μg polymer dependent/ 34.5 μg NP/g

FTIR spectroscopy

Chemical analysis

> 300 μm

μFTIR spectroscopy Raman spectroscopy

GC–MS

• •

Amount of the quantity of particles Chemical classification

10–25 μm

Chemical analysis

> 300 μm

Identification and assessment of plasticizers and byproducts of the breakdown of microplastics such as PS, PP, and PE.

ng

•• •• • • • •• • ••

Assessing the morphology, nanostructure, and adhesion behavior of microscopic particles is accomplished through the use of high-resolution imaging.

High-quality imaging makes Particle surface characterization possible, and elemental composition is obtained by coupling it with EDS. No preprocess Polymer and associated organic additives simultaneously identified and quantified.

Minimal sample preparation Nondestructive

Chemical characterization of smaller particles is more efficient Allows particle counting. Offers superior response to non-polar plastic functional groups. Higher spatial resolution, Less sensitivity to sample thickness than FTIR. Separating various volatile compounds requires only a small sample amount for injection. High sensitivity High resolution

•• • • • •• •• • •• • • • •• •

Slow scan rates Limited probe movement flexibility Smaller scan areas in microscopic methodologies can reduce imaging resolution due to artifacts or fragments introduced during tip-sample interactions or imageprocessing processes. Sample preparation and coating/fixation require highly expensive equipment.

The instrument is not recommended for complex environmental samples, uses hazardous organic solvents, High cost gives neither size nor quantity of particles, Destructive technique. Contaminations and additives may disrupt identifications by overlapping polymer bands, resulting in disturbed results. Susceptible to disruption from water. Insufficient precise measurement Quite time-consuming

Samples of fluorescence excited by a laser cannot be quantified.

Extracting contents from samples using organic solutions Substantial purification sequence Potential column exchange, Sample destruction (Continued)

Table 4.8

(Continued)

Analysis

ICP-MS

Fluorescence lifetime imaging microscopy (FLIM)

Resonance microwave spectroscopy

Application

•• •• • • • •

Adsorbents analysis Chemical elements quantification Quantification of microplastics Identification of microplastics Distribution of microplastics

Detection of microplastics in complex matrixes Quantification of microplastics in complex matrixes Determination of microplastics in complex matrixes

Detection limit

ng/L

100 μm

50–500 μm (concentrations 35 MPs were detected, averaging 1.4 MPs/g of tissue, with polypropylene (PP), polyethylene terephthalate (PET), and resin being the most prevalent types. Shumin Huang et al. (2022) employed a laser infrared imaging spectrometer and FTIR microscope to examine sputum samples and assess MPs within the tracheobronchial

5.1 Introduction

tree using a detection method spanning 20–500 μm. The median size of the detected MPs was 75 μm, with an interquartile range of 44–210 μm, with polyurethane (PU) and polyester (PES) being the predominant types, accounting for 33% and 21% of the total MPs, respectively. In addition, Martin Günter Joachim Löder et al. (2015) used the FPA-based microFTIR imaging method to provide a reliable and automated approach for the analysis of MPs concentrated on filters, reducing potential error rates associated with visual inspection alone. The method facilitated the detection of small MPs with high spatial resolution, enabling the identification of particles as small as 20 mm. The most prevalent polymers identified using FPA-based micro-FTIR imaging in the study were PE, PP, Polymethylmethacrylate (PMMA), polystyrene (PS), and polyvinyl chloride (PVC), ranking among the 10 most significant polymers.

5.1.2

Raman Spectroscopy

For the sensitive analysis of MPs in diverse environmental matrices, Raman spectroscopy reigns supreme. This technique leverages the power of inelastic light scattering, where incident light interacts with the sample’s molecules, inducing characteristic vibrational modes. These vibrations translate into a unique “fingerprint”—the Raman spectrum—offering detailed information regarding the sample’s chemical composition. This fingerprint analysis enables precise identification of the specific polymer type present in each MP particle. However, when dealing with minute plastic fragments and low concentrations, even Raman’s prowess can be challenged. Here’s where Surface-Enhanced Raman Spectroscopy (SERS) steps in as a powerful amplification technique. This SERS utilizes specially designed nanostructured surfaces that dramatically enhance the Raman signal intensity. This magnification effect arises from an increased electromagnetic field near the nanostructures, leading to a boosted “scattering cross-section” of the molecules. Consequently, even weak Raman signals from miniscule MPs become readily detectable, offering unparalleled sensitivity for environmental analysis. In essence, Raman spectroscopy serves as a crucial tool for unveiling the hidden world of MPs, while SERS acts as its magnifying glass, allowing scientists to peer deeper and gain valuable insights into the composition and distribution of these pervasive environmental contaminants. In a recent study conducted by Mikulec et al. (2023), the feasibility of detecting polystyrene in pure water using surface-enhanced Raman spectroscopy was investigated. The study involved the synthesis of four different types of gold nanoparticles, which served as active substrates for detecting MPs. It was found that using smaller gold nanoparticles (approximately 35 nm) in high concentrations yielded the most robust SERS signal for polystyrene microparticles. The experimental setup included preparing a mixture of 500 μL of Au NPs, 25 μL of the MP solution, and 25 μL of either KCl or NaNO3 as an aggregating agent in a glass tube to enhance the SERS signal. This mixture was then deposited onto a glass wafer and after evaporation of the droplet, Raman spectra were recorded. Optimal results were achieved when the volume ratio of colloid to polystyrene microparticles fell within the range of 20:1 to 60:1, allowing for the detection of polystyrene at concentrations as low as 6.5 mg/L. However, adapting the method for other types of MPs, such as PE, proved challenging, as noted by the author.

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In a separate study, Xu et al. (2020) developed an analytical approach for detecting micro and nanoplastics using a combination of SERS and Klarite substrates. These substrates, characterized by a dense grid of inverted pyramidal cavities, concentrate incident light into intense hotspots, thereby enhancing the Raman signal of the analytes. The research demonstrated that Klarite substrates could detect and identify synthetic MP particles as small as 360 nm, with a significant enhancement factor of up to two orders of magnitude for polystyrene analytes. The method was successfully applied to analyze atmospheric aerosol particles collected on the roof of Fudan University, Shanghai, focusing on particles smaller than 2.5 μm.

5.1.3

Scanning Electron Microscopy/Energy-Dispersive X-Ray Spectrometry

SEM is a technique that uses a focused beam of electrons to scan the surface of the samples and create high-resolution imaging of the surface topography of the particles, providing information about their shape, size, and surface features. The EDX component of the technique allowed for the detection and quantification of the elemental composition of the particles, which can be used to distinguish MPs from other types of plastic particles. Moreover, Ibrahim et al. (2020) used SEM/EDX analysis to detect MPs in human colectomy specimens. The samples were chemically digested with 10% KOH at 60 C for 8 hr, filtered and dried before being analyzed under a scanning electron microscope with energy-dispersive X-ray analysis. The surface morphology and elemental composition of the samples were studied and the composition of three common polymers (PP, polyamide, and polycarbonate) in MPs was identified for each specimen. The study found evidence of MPs in all samples, with filament form accounting for 96.1%.

5.1.4

Pyrolysis Gas Chromatography/Mass Spectroscopy

Pyr-GC–MS is a powerful analytical technique for characterizing various intractable polymers and composite materials, particularly those resistant to traditional GC–MS analysis. Its operation is deceptively simple yet remarkably effective. Sample Decomposition: The sample is subjected to controlled, rapid heating in an inert atmosphere, typically within a preheated furnace. This thermal degradation breaks down the material into smaller, stable fragments called pyrolyzates. Chromatographic Separation: The pyrolyzates are then separated based on their individual chemical properties using gas chromatography (GC). This acts like a sorting mechanism, lining up the fragments for individual analysis. Mass Spectrometry Identification: Finally, each separated fragment is analyzed by mass spectrometry (MS), which identifies its unique mass signature. This allows for precise identification and quantification of the original material composition. Okoffo et al. (2021) developed a novel analytical method for quantifying MPs in treated sewage sludge. Their approach combined pressurized liquid extraction (PLE) for efficient isolation of MPs from the complex matrix with a double-shot pyrolysis GC–MS (Pyr-GC/ MS) system for sensitive and specific identification and quantification of five common plastic types: PE, PS, PP, PMMA, and PVC. The double-shot pyrolysis technique involved two injections of the sample into the pyrolyzer, enhancing the sensitivity and accuracy of the

5.1 Introduction

analysis compared to single-shot methods. Ribeiro et al. (2020) conducted a similar study but with a focus on MPs in seafood samples. Their methodology involved a single-shot PyrGC/MS approach after accelerated solvent extraction (ASE), prioritizing rapid analysis over the heightened sensitivity achieved through the previously explored double-shot technique.

5.1.5 Rapid Screening/Fluorescent Microscopy, High Throughput Analysis of Microplastics Fluorescence microscopy is a technique that uses a fluorescent dye or probe to label specific structures or molecules within a sample. When the sample is illuminated with a specific wavelength of light, the labeled structures or molecules emit light at a different wavelength, which can be detected and visualized using a fluorescence microscope. Yoo et al. (2023) made a feasible study using fluorescence microscopy for the detection of MPs in ambient PM10 aerosols. Specifically, the technique involved staining the particles with Nile Red, a fluorescent dye that selectively binds to certain types of plastics. When illuminated with a specific wavelength of light (in this case, an excitation laser wavelength of 490–500 nm), the stained MP particles emit green fluorescence, allowing for their visualization and identification under the fluorescence microscope.

5.1.6

Solid–Liquid–Liquid Microextraction Technique

The microextraction technique known as μSLLE is a compact analytical method designed to extract and analyze persistent organic pollutants (POPs) in tiny marine plastic particles. Abaroa-Pérez et al. (2021) conducted a study and validated the technique and it was applied to MP samples collected from the Canary Islands, Spain. In this study, the μSLLE method was validated using spiked MP samples, and its application to authentic marine MP samples demonstrated its efficacy in quantifying concentrations of diverse persistent pollutants within marine MPs. The procedure involves solid–liquid extraction using methanol as the extractant, followed by liquid–liquid microextraction, achieved by introducing nhexane with internal standards to the methanol extract. This method facilitates the rapid determination of up to 27 analytes per sample, encompassing 8 polychlorinated biphenyls, 15 organochlorine pesticides and 4 polyaromatic hydrocarbons. GC with mass spectrometry is employed for the subsequent analysis. The study demonstrated that the μSLLE method is effective for determining the concentrations of various persistent pollutants in marine MPs, providing a quick, cost-effective and efficient technique for assessing pollution in marine environments.

5.1.7

Elemental Analyzer/Isotope Ratio Mass Spectrometry

The EA/IRMS is a widely used technique to analyze plastic polymers based on their carbon stable isotopes. The elemental analyzer operates using a dynamic flash combustion technique, where samples are combusted in a reactor with a pulse of oxygen to facilitate the process. The resulting gases are then carried by inert gas across a catalyst and a GC column for separation. Further, the isotopic composition is determined by the mass spectrometer. A study conducted by Berto et al. (2019) explored the characterization of plastic polymers using EA/IRMS. The study disclosed that carbon stable isotopes prove effective in

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discriminating among various plastic types, encompassing polyester PU, PE with starch blend, and other biodegradable plastics. In addition, the method demonstrated utility in assessing degradation in marine environments by revealing an elevation in isotopic values. The technique offers notable advantages, including heightened sensitivity, a minimal sample requirement, expeditious analysis, cost-effectiveness and the absence of limitations in analyzing black/dark samples.

5.2 Instrumentational Methods to Study Microplastics in Different Matrices Instrumentational methods play a crucial role in addressing the challenges associated with studying MPs across different environmental matrices, including water, sediments, soils and biota. In this section (Tables 5.1–5.3) explore state-of-the-art instrumentational methods employed in the study of MPs in diverse matrices.

Table 5.1 Identification of MP Abundance in Water Samples Using Various State-of-the-Art Methods State-of-the-art technique for the identification

Abundance

References

Stereomicroscope and μ-FTIR

2.1–71 items/L

Deng et al. (2020)

20 L of water samples were collected with a sampler and filtered through a 48 μm steel sieve

μ-Raman spectroscopy and SEM

1733 items/m3

Nie et al. (2019)

Lebanese coast (Eastern Mediterranean Basin)

Collected by a manta trawl net (52 μm mesh size)

Stereomicroscope and micro-Raman spectroscopy

6.7 MPs/m3

Kazour et al. (2019)

Yangtze River, China

(30 × 15 cm): collected by a manta trawl net-300 μm mesh size

ATR-FTIR, stereoscopic microscope, and Pyr-GC–MS

1.62 × 105 to 4.25 × 106 items/ km2(trawling water)—800 to 3088 items/ m3(filtering water)

He et al., (2021)

Location

Sampling technique

Shaoxing City, China

0–5 cm below the surface: collected by using a metal pail shovel.

Nansha Islands, South China Sea

μ-Raman, Raman microspectroscopy; ATR-FTIR, attenuated total reflectance-Fourier transform infrared spectroscopy; Pyr-GC–MS, pyrolysis-gas chromatography–mass spectrometry.

5.2 Instrumentational Methods to Study Microplastics in Different Matrices

Table 5.2 Methods

Identification of MP Abundance in Sediment Samples Using Various State-of-the-Art

Location

Sampling technique

State-of-the-art technique for the identification

Vistula River (Poland)

4–5 cm depth: collected by using a stainless-steel water probe and plankton nylon net (55 μm mesh size)

Lebanese coast (Eastern Mediterranean Basin)

Abundance

References

Raman spectroscopy, SEM, and energydispersive X-ray spectroscopy.

90–580 items/kg

Sekudewicz et al. (2021)

2 cm depth: Sublittoral sediment samples were collected employing a modified Petersen grab, a cylindrical steel corer equipped with two opposing stainless-steel jaws that enclose the sediment upon closure.

Stereomicroscope and micro-Raman spectroscopy

4.68 MPs/g

Kazour et al. (2019)

Shaoxing City, China

Top 5 cm (2 kg) of wet sediments from 21 different sites (July– October 2018): collected by using a metal pail shovel

Stereomicroscope and μ-FTIR

16.7–1323 items/ kilogram (dw)

Deng et al. (2020)

Thames River, UK

Subtidal (10 cm depth): Collected by using a Stainless-steel scoop.

Raman spectroscopy

66 particles 100/g

Horton et al. (2017)

μ-FTIR, micro Fourier Transform Infrared Spectroscopy; micro-Raman, Raman Microspectroscopy; SEM-EDS, Scanning electron microscopy–energy dispersive X–ray spectroscopy.

5.2.1

Water Samples

In water samples, instrumental methods such as manta trawls, neuston nets, plankton nets, and water intake pumps are commonly used for collection and identification. These methods enable researchers to capture MPs present in the water matrix and are directly influenced by the mesh size of the sampling tools. These techniques have been reported to yield considerable amounts of data and are useful for comparing the abundances of MPs from different sampling locations.

5.2.2

Sediment Samples

In sediment samples, instrumental methods such as metal grabs, box corers, and bottom trawls are employed to collect and identify MPs. However, the highly heterogeneous nature of subtidal sediment MP distribution necessitates multiple replicates for a representative sample. This diversity of sampling methods, unfortunately, leads to inconsistencies in

113

Table 5.3 Identification of MP Abundance in Aquatic Biological Samples Using Various State-of-the-Art Methods

Biota

Location

Sampling technique

state-of-the-art technique for the identification

Fish

Nansha Islands, South China Sea

35 fish samples were collected by artisanal fishing

Seafood species: Engraulis encrasicolus and Spondylus spinosus

Lebanese coast (Eastern Mediterranean Basin)

Fishes (foreochromis niloticus and Barbonymus gonionotus) and bivalves (Elongaria orientalis) Polychaete: blue mussel Mytilus edulis and the lugworm Arenicola marina

Abundance

References

μ-Raman spectroscopy and SEM

3.1 items per individual

Nie et al. (2019)

E. encrasicolus were collected by using purse seine nets, and Spondylus spinosus was collected by fishermen.

Stereomicroscope and μ-Raman spectroscopy

2.9 ± 1.9 and 8.3 ± 4.4 ingested MPs/individual

Kazour et al. (2019)

Indonesia

Collected by a manta trawl net (333 μm mesh size)

Dissecting microscope

105.25 ± 45.07 – 155.50 ± 61.96; 62.13 ± 20.33 – 155.00 ± 81.71 MPs/ individual in Fishes and 36.00 ± 13.67 – 76.17 ± 29.46 particles/individual in the bivalves

Lestari et al. (2021)

French– Belgian–Dutch coastline

Collected by a shovel

μ-Raman spectrometer

1.2 ± 2.8 particles/g

Van Cauwenberghe et al. (2015)

μ-Raman, Raman microspectroscopy; SEM-EDS, scanning electron microscopy–energy dispersive X–ray spectroscopy, Dissecting microscope.

5.3 Technologies for Measuring Nano-Microplastics

quantification units (e.g., MP per gram, area, or volume), hindering direct comparisons of existing monitoring data.

5.2.3

Biological Samples

In biological samples, a range of techniques is employed to sample biologically ingested MPs found in various organisms such as zooplankton, fish species, crustaceans, and bivalves. These methods encompass the collection of zooplankton through bongo nets, fish species captured using pelagic nets and trawls, and crustaceans gathered through bottom trawls or traps. Commonly used metrics for quantifying MPs in aquatic organisms include the weight-based measurement of MPs per organism, the count of MPs per individual, or the percentage of individuals containing ingested MPs.

5.3 Technologies for Measuring Nano-Microplastics and Determining the Relative Contributions of Particles of Varying Size, Shape and Chemical Composition This section discusses various technologies currently employed to measure MPs and identify their key attributes: size, shape, and chemical composition. In addition, it explores the challenges and limitations of the techniques and examines state-of-the-art technologies (Table 5.4) that hold promise for a more comprehensive and nuanced understanding of the MP landscape. Figure 5.1, illustrates a comprehensive MP Classification Matrix, providing insights into the size, type, and origin of MPs. It presents a spectrum of descriptors, such as fragment, fiber, sphere, film, and sheet, alongside a range of sizes from 1 μm to 1 m, spanning the nano, micro, meso, macro, and mega scales. In addition, the matrix distinguishes between primary and secondary MPs, indicating their manufacturing origins or fragmented states. Furthermore, it outlines the distinction between natural and synthetic polymers, encompassing both organic and inorganic sources. This matrix serves as a valuable tool for understanding the complexity of MPs and their diverse characteristics within environmental ecosystems.

5.3.1

Quantifying the Micro Menace: Measuring Microplastics

The first step in addressing MP pollution is accurately measuring their presence. Traditionally, researchers relied on filtration techniques, collecting MPs on filters of varying pore sizes. While simple and cost-effective, this method struggles with smaller particles and underestimates total abundance (Dris et al., 2018). Advanced methods like flow cytometry utilize lasers to identify and count individual MPs, offering greater sensitivity and size discrimination (Morgana et al., 2024). Imaging techniques such as FTIR microscopy and Raman spectroscopy provide further characterization by identifying the chemical composition of individual particles (Xu et al., 2019).

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Table 5.4 Technologies Used for Measuring and Characterizing Nano-Microplastics Based on Their Shape, Size, and Chemical Composition in Diverse Matrices Category

Findings

Matrix

Technology

Reference

Shape

Rod, ellipse and oval were the most abundant

Wastewater, pondwater and marine water.

FPA-μFTIR imaging spectroscope (Focal Plane Array-based Fourier Transform Infrared Spectroscope)

Liu et al. (2023)

Fragment, fiber, sphere, film, sheet.

Soil

Fourier transform infrared spectroscopy

Zhang et al. (2022)

90–1500 μm

Fish and mysids

Stereomicroscope, inverted epifluorescence microscope.

Lehtiniemi et al. (2018)

2 μm–250 nm

Wastewater

FT-IR microscopy, Raman, and optical microscopy (OM)

Caputo et al. (2021)

Distinguish synthetic polymer particles from inorganic particles.

Wastewater

Infrared spectroscopy, pyrolysis GC–MS.

Caputo et al. (2021)

PE, PP, PS, PET, PVC, PA etc.

Wastewater, sludge, seafood. Marine sediments.

Pyrolysis GC–MS, Thermal desorption −proton transfer reactionmass-spectrometry, ICP-MS and ICP-OES.

Ivleva, (2021)

Size

Chemical Composition

Inductively coupled plasma optical emission spectrometry (ICP- OES), inductively coupled plasma mass spectrometry (ICP-MS), micro-Fourier transform infrared spectroscopy (μ-FTIR), Polyethylene, Polypropylene, Polystyrene, Polyethylene Terephthalate, Polyvinyl Chloride and Polyamide.

5.3.1.1 Shape Matters: Unveiling Morphology

MPs come in a bewildering array of shapes, each influenced by their source and degradation processes. Fibers, fragments, films, and spheres are just a few examples. Distinguishing these shapes is crucial for pinpointing sources and predicting environmental behavior (Cózar et al., 2014). Image analysis, often coupled with machine learning algorithms, is proving invaluable in classifying MP shapes with increasing accuracy and automation (Gasperi et al., 2018). Laser diffraction techniques can also provide information on particle size and shape simultaneously.

5.3.1.2 Demystifying the Material: Identifying Chemical Composition

Knowing the chemical composition of MPs is essential for tracing their origins and assessing potential human and environmental health risks. Spectroscopic techniques like FTIR and Raman microscopy analyze the molecular structure of the particles, providing molecular fingerprints that identify specific polymer types (Koelmans et al., 2016). Pyr-GC/MS further refines the analysis by breaking down the polymers into characteristic fragments, enabling

5.4 Distribution and Monitoring of Microplastics

Plastics

Size

Nano plastics 1 nm–1 μm

Microplastics 1 μm–5 mm

Mesoplastics 5 mm–2.5 cm

Shape

Type Primary Plastic production

Macroplastic 2.5 cm–1 m

Fragments

Secondary Fragmentation

Cloth fibres, Skincare products, Nurdels Organic

Pellets

Inorganic Synthetic

Natural

Thin Film Fibers

Polymers

Figure 5.1 Schematic of MP Definitions and Classifications based on Size, Shape, Origin, and Polymer Type

detailed compositional analysis (Seeley and Lynch, 2023). These techniques help pinpoint sources such as textiles, bottles, or tire wear, paving the way for targeted mitigation strategies.

5.3.2

Challenges and Emerging Solutions

Despite the advances, accurately measuring and characterizing MPs remains a complex challenge. Contamination, particularly from airborne fibers, can significantly skew results (Dris et al., 2018). In addition, distinguishing MPs from natural particles like cellulose can be challenging. Researchers are actively developing new technologies to address these limitations. For instance, Biosensors are being explored for their ability to specifically detect and identify MPs based on their unique biological interactions. Miniaturized, fielddeployable instruments hold promises for real-time monitoring of MPs in the environment, revolutionizing data collection and response strategies.

5.4

Distribution and Monitoring of Microplastics

The distribution of MPs exhibits both spatial and temporal, such as wind, currents, and human activities. These aspects are discussed below.

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Spatial Distribution 1) River and Estuaries: Rivers and estuaries are major pathways through which MPs can enter marine environments from terrestrial sources. Intense river flow following heavy precipitation during the wet season has the potential to trigger the runoff of MPs into coastal regions. Therefore, there are often high abundances of MPs in coastal areas immediately after heavy rain events (Shim et al., 2018). 2) Ocean and Gyres: MPs tend to accumulate in convergence zones of Ocean gyres, where circular currents concentrate marine debris. These accumulation zones have been observed in the North and South Pacific Ocean and Indian Oceans (Shim et al., 2018). 3) Coastal Areas: From city streets to factory floors, a steady stream of MPs finds its way to coastlines. Carried by rivers, dumped directly, or swept by currents, they accumulate in alarming numbers, especially near urban and industrial hubs. 4) Proximity to Pollution Sources: MPs are discharged into water bodies through wastewater effluents. Harbors and areas near sewage treatment plants, which are sources of MPs, may have higher concentrations. Temporal Distribution 1) Seasonal Fluctuations: Seasonal variations can influence the prevalence of MPs in marine ecosystems. Increased human activities such as tourism and agricultural practices can significantly impact the dispersal of microplastics within marine environments. 2) Storm Event: Storm events act as potent forces, mobilizing and redistributing MPs within the water column. This phenomenon is exemplified by the study of Lattin et al. (2004) conducted in southern California’s offshore waters. Interestingly, their findings revealed a significantly higher abundance of MPs at a depth of 30 m, exceeding both surface and mid column water levels, both before and after storm events. This observation suggests that storm-induced mixing and turbulence not only transport MPs from diverse sources but also redistribute them toward deeper water layers. This finding highlights the need for a comprehensive understanding of MP dynamics beyond surface waters, considering the significant potential for deep-sea accumulation and associated ecological consequences. 3) Tidal Cycles: Tidal cycles and currents influence the distribution of MPs along coastlines and within water bodies. This leads to patchy distribution and steep gradients of MP abundance in coastal zones. 4) Anthropogenic Activities: The production, utilization, and disposal of plastic by human activities play a role in disseminating MPs within marine ecosystems. Inadequate waste handling and littering practices can lead to the discharge of MPs into the environment. Monitoring Techniques 1) Water Sampling: Surface and subsurface water samples are collected and analyzed for MP presence and type. 2) Sediment Sampling: Cores are taken from the seabed to analyze MP accumulation in sediments.

5.5 Review of Existing Monitoring Programs for Marine Microplastics

3) Biomonitoring: Organisms such as polychaete and zooplankton are used as indicators of MP contamination in the food chain. 4) Remote Sensing: Satellites and drones can be used to identify large-scale patterns of plastic pollution in oceans and along coastlines.

5.5 Review of Existing Monitoring Programs for Marine Microplastics The plastic we use and see in our daily lives ends up in the marine ecosystem through air, water, and sewage treatment plants, which poses major health concerns on human health along with the environment that can, in turn, cause huge concerns for our future too. MP, minute plastic particle fragments 25 mm in size) from beaches around the world. Beach litter monitoring program, like the ICC, provides data on shoreline accumulation of plastics but may not reflect the true scale of marine plastic pollution, especially in offshore areas where currents and winds can displace plastics away from the coastline. Efforts are underway to address this limitation and capture the complete extent of plastic pollution in the marine environment. Researchers are increasingly exploring methods to study offshore trends in plastic pollution. This involves using technologies such as high-resolution aerial monitoring, hyperspectral scanning techniques, and autonomous vehicles to track and understand the distribution of plastics in open water. 3) Mussel Watch Program: The Biota monitoring program focuses on assessing and monitoring the health of the coastal ecosystem by examining mussels and other bivalve mollusks. Programs like the Mussel Watch program analyze mussels and other filter feeders for MP ingestion. Biota monitoring programs play a crucial role in supplying valuable data regarding the transfer of MPs through various levels of food webs.

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4) EU Marine Strategy Framework Directive (MSFD): MSFD was put in order as an initiative to protect the marine environment and biodiversity upon which our health depends. The MSFD demands effective implementation for achieving Good Environmental Status (GES) of European marine waters. This necessitates enhanced monitoring and optimized network design. The key lies in embracing innovative and cost-effective monitoring systems that surpass traditional methods in terms of accuracy, efficiency, and affordability. Molecular approaches, in situ analysis systems, and remote sensing technologies offer immense potential in this regard. Molecular techniques provide highly specific and sensitive detection of pollutants and biological indicators, leading to more accurate assessments. In-situ analysis systems enable real-time data collection directly within the marine environment, enhancing data quality and reducing reliance on costly ship-based surveys. Remote sensing offers large-scale spatial coverage and costeffective monitoring of vast areas, particularly for parameters like temperature, chlorophyll, and surface pollutants. 5) Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP): Established in 1969, GESAMP functions as an advisory body offering specialized insights into the scientific dimensions of marine environmental protection. This body has played a pivotal role in disseminating knowledge through the publication of comprehensive reports and studies specifically addressing the intricate issue of MPs. The information derived from these publications serves as a crucial foundation for governments and international organizations, aiding in the formulation of new policies aimed at mitigating the impact of MPs on marine ecosystems. 6) Marine Conservation Society: The Marine Conservation Society plays a vital role in the United Kindom’s efforts to protect and conserve its marine environment, primarily aimed at achieving objectives such as sustainable fisheries, reducing marine litter and safeguarding marine habitats. This seafloor monitoring program provides valuable insights into MP sinks by collecting sediment samples to assess MP abundance on the seabed. In recent reports, a 55% drop in plastic bags was found on United Kingdom beaches since 5p was introduced. Figure 5.2 shows the Marine Conservation Society in the UK outlines six objectives in 2024 to mitigate plastic pollution along the shores of the United Kingdom. 7) The 5 Gyres Institute: The 5 Gyres Institute focuses on understanding and combating plastic pollution, including microplastics, in the world’s oceans. They conduct research expeditions to study the distribution and impact of plastic debris, contributing valuable data to the scientific community

Goal 1

Recycle effectively

Figure 5.2 Pollution

Goal 2

Reduce singleuse plastic usage

Goal 3

Goal 4

Goal 5

Goal 6

Be aware of products that include microplastics

Volunteer to reduce plastic pollution

Sign petitions and join campaigns that reduce ocean pollution

Support charities that are challenging plastic pollution

The Marine Conservation Society in the UK Outlines Six Goals to Alleviate Plastic

5.5 Review of Existing Monitoring Programs for Marine Microplastics

5.5.1

Aerial Monitoring of Plastic Pollution in the Marine Environment

Recognizing the growing threat of plastic pollution to our oceans, aerial monitoring emerges as a powerful tool. Aircraft and drones, equipped with specialized sensors and cameras, soar above vast stretches of water, collecting crucial data on the presence and distribution of plastic debris. For instance, Hyperspectral imaging, a remote sensing technique employed by unmanned aerial vehicles (UAVs), plays a key role in this mission. This technology utilizes a wide range of electromagnetic wavelengths, enabling the detection and differentiation of various plastic types, including PE and PET. This innovative approach offers a sustainable and cost-effective solution for monitoring the ever-present problem of plastic pollution, contributing to a cleaner and healthier marine environment. A study was conducted (Balsi et al., 2021) in Sardinia, Italy, to identify MP debris loads in the sea and on the coast by using a high-resolution aerial monitoring and hyperspectral scanning technique. Hyperspectral imaging or imaging spectroscopy captures the spectral properties of different plastic polymers. Each polymer has specific absorption bands in the Short-Wave InfraRed spectrum, which can be detected and analyzed using hyperspectral data. In this investigation, a drone-mounted spectral device employing a low-cost, lightweight, and power-efficient push-broom sensor was utilized for data acquisition. Hyperspectral images obtained were subjected to processing through algorithms encompassing mosaicking, georeferencing and orthorectification. Detection of plastic litter was executed through statistically significant feature selection and linear discriminant analysis. The research highlights the capability of hyperspectral sensing for the real-time identification and detection of plastic litter during aerial surveys.

5.5.1.1

The Role of Vertical Mixing on the Global Distribution of Microplastic

Vertical mixing plays a vital role in determining the global distribution of tiny MP fragments. These tiny MP fragments, ranging from millimeters to just micrometers in size, are ubiquitous in the environment, affecting their transport, dispersal and fate in marine environments. This contamination extends to oceans, freshwater systems, and extends to the atmospheric domain, permeating the air we breathe. An imperative understanding of their distribution is crucial for assessing their environmental and ecological impacts. The following are essential considerations in this context. 1) Size-Dependent distribution a) Larger particles: Due to their buoyancy, larger particles tend to stay near the surface, impacted more by surface current driven by wind and waves. However, they can still be mixed down to some extent during strong storms or in areas with intense mixing. b) Smaller particles: Their minimal buoyancy makes them more susceptible to turbulent flow and can be carried deeper into the water column, even reaching the seafloor. 2) Surface transport and submersion Surface currents driven by wind and other factors stir the ocean surface and create turbulence, which can cause MPs to fall from surface waters into the deeper water column. Furthermore, seasonal mixing, such as variation in temperature and salinity throughout the year, can lead to changes in ocean density, triggering mixed water at different depths

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and further distributing MPs at different depths. This submersion can lead to the vertical distribution of MPs. 3) Aggregation and sedimentation Vertical mixing within the water column facilitates the aggregation of MPs with other suspended particles, including organic matter and minerals. This aggregation can manifest in two forms: homogeneous aggregation, where MPs adhere to other MPs of the same type, and heterogeneous aggregation, where MPs bind to dissimilar particles like organic matter or minerals (Li et al., 2023). This aggregation can lead to MP buoyancy and settling rates, resulting in them being transported to the seafloor through sedimentation, where they can accumulate in sediments. 4) Biological interaction Vertical mixing also influences the interactions between MPs and marine organisms. Marine and aquatic organisms, specifically filter feeders, can ingest MPs, concentrating them in their tissues and further affecting their distribution across different depths, where they can interact with phytoplankton, zooplankton, and other marine life, potentially leading to ecological consequences and influencing the movement of MPs within marine food webs.

5.5.1.2 The Role of Bioturbation in Distributing Secondary Microplastics in Marine Sediments

Bioturbation refers to the mixing and disturbance of sediments by burrowing, digging, and feeding activities of benthic organisms such as crabs, sea urchins, worms, and many more. The ubiquitous presence of MPs, especially secondary MPs (fragments from larger plastic items), in marine environments is a growing concern. These tiny contaminants pose potential threats to marine organisms and human health. Understanding their fate and transport in sediments is crucial for assessing their impact (Kristensen et al., 2012). Figure 5.3 shows Figure 5.3 Illustrates Various Bioturbation Types, Depicting Diverse Ways Organisms Interact with Sediment Particles, Contributing to Particle Mixing

BIOTURBATION Particles

Solutes

Reworking of particles

Biodiffusor /disperser

Oxygenation

Rejuvenator Conveyor belt feeder

5.5 Review of Existing Monitoring Programs for Marine Microplastics

the bioturbation types refer to different ways in which organisms interact with sediment particles and contribute to particle mixing, and are discussed as follows: There are four major functional bioturbation categories: 1) Biodiffusors/dispersers: These organisms mainly accomplish particle redistribution through local transport. They create diffusion-analogous mixture patterns within the upper sediment layers by movement, burrow construction and maintenance. 2) Conveyor belt feeders: These organisms rely on nonlocal mechanisms for particle transport. They move particles along vertical burrow sections through gravity-driven transport. This can lead to the formation of particle accumulation zones in deeper sediment layers. 3) Rejuvenators: These organisms also rely on nonlocal mechanisms for particle transport. They actively or passively drag food particles into their burrows, contributing to particle mixing and incorporation into burrow walls. 4) Oxygenation: These organisms stimulate solute transport and exchange processes with adjacent pore waters. They can enhance oxygen penetration into anoxic sediment zones, stimulating organic matter degradation and particle transport. An activity such as Bioturbation has a significant impact on the distribution of secondary MPs in marine sediments in several ways. 1) Vertical Mixing Bioturbation involves the movement of organisms within the sediments, such as burrowing, feeding, or reworking of particles. This can lead to the burial of MPs deeper into the sediment, potentially reducing their bioavailability and immediate harm to benthic organisms. 2) Horizontal transport Burrowing organisms can create a patchy distribution of MPs within the sediment, with a higher impact in the vicinity of burrows and biogenic structures (Hobbs, 2022). This can lead to the horizontal transport of MPs along with other particles, influencing their spatial distribution across the seabed and remaining in the ecosystem for an extended time. 3) Size-selective Transport This size-selective transport is influenced by factors such as feeding mode, mucus secretion, and burrow morphology and can vary spatially and temporally within a polychaete community. Smaller particles tend to undergo passive transport with sediment grains, influenced by differential gravitational forced migration patterns, while larger or irregularly shaped particles may be subject to selective ingestion or avoidance by organisms, resulting in disparate distribution (Hernández Guevara, 2004). 4) Interaction with microbial processes Bioturbation activities create microenvironments within sediments, influencing microbial communities (Wyness et al., 2021). Microbes play a key role in the degradation of organic matter, including plastics. Bioturbation can affect the distribution of microbial activity, potentially impacting the degradation rates of secondary MPs.

5.5.2 Thermo Degradation Method to Assess the Distribution of Microplastics in Marine Sediments The thermodegradation method is a promising technique for assessing the distribution of MPs in various environmental samples including marine sediments. This technique involves subjecting the sediment samples to high temperatures to selectively break down

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organic matter and the left residue represents as most resistant plastic particles. It offers several advantages such as visual identification and density separation, but also has some limitations to consider such as most of the thermodegradation methods degrade the natural organic matter in the sediment at high temperatures, potentially interfering with the signal from MPs. Various types of thermodegradation methods are used for assessing the distribution of MPs which are discussed below. 1) Thermogravimetric Analysis (TGA) coupled with Gas chromatographic-mass spectrometer: TGA quantifies changes in sample mass with high sensitivity as a function of temperature in a controlled environment. As the temperature increases during the TGA process, polymers undergo degradation, emitting detectable decomposition gases that are analyzed by the TGA Analyzer coupled with GC–MS. This analytical technique allows for the identification of the specific polymers present in the samples based on the characteristic decomposition products of each polymer. In addition, the method allows for the quantification of different MP particles in the environmental samples by analyzing the composition of decomposition gases and determining the concentration of each polymer. Dümichen et al. (2015) investigated TGA-MS method which involves the preparation of samples by placing them in aluminum oxide crucibles for thermogravimetric analysis (TGA) under a nitrogen atmosphere. The samples are heated from 25 to 650 C at a rate of 10 C/min and the weight loss is measured as a function of temperature. Subsequently, the gas evolved during the TGA is analyzed using thermal desorption gas chromatography–mass spectrometry (TDS-GC–MS). This involves trapping the representative part of the decomposition gases from TGA directly on solid-phase extraction agents (twisters) and then analyzing them by TDS-GC–MS. 2) Thermal Desorption Gas Chromatographic-Mass Spectrometer (TD-GC–MS) coupled with pyrolysis: Pyrolysis involves heating the sample in the absence of oxygen, leading to the breakdown of organic materials into volatile decomposition gases. This method allows for qualitative and quantitative analyses of polymers in the samples. Gomiero et al. (2019) proposed a method specifically tailored for characterizing and quantifying the dominant size range of MPs in marine sediments: the micrometric range. This method leverages commercially available, certified stainless-steel sieves to capture and categorize MPs based on the most frequently encountered size classes in such environments. To assess their distribution within sediments, the study analyzed 8 kg wet sediment samples per site. This involved extracting, purifying, and size-fractionating the MPs using a specific set of certified sieves ranging from 10 to 250 μm mesh size. Preconcentrated on fiberglass filters, the entire filter contents were subsequently analyzed via thermal desorption pyrolysis gas chromatography/mass spectrometry (TD-Py-GC/MS) for definitive identification and quantification. 3) Thermal Fenton Reaction: MPs are broken down in a two-step process using a hot, pressurized water bath (hydrothermal conditions) and a chemical reaction (Fenton oxidation). Both methods work together to loosen and lengthen the long molecules (carbon chains) of MPs, making them easier to break apart further. This process creates smaller molecules with oxygen groups attached (carbonyl groups) and makes the plastic less organized (decreased crystallinity). The combination of hot water, lots of hydrogen ions, and powerful oxygen-based molecules (hydroxyl radicals) makes this method very effective at destroying MPs. Hu et al. (2021) made a feasible study using the hydrothermal coupled Fenton system, and it proved highly effective for the degradation of MPs in

5.5 Review of Existing Monitoring Programs for Marine Microplastics

water. It achieves 95% weight loss in 16–18 hr and a 75% mineralization efficiency in 12–14 hr, indicating its capability to break down MPs efficiently. Further, various analytical techniques used for the distribution and assessment of MPs including Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), size distribution analysis using Mastersizer 2000 and thermogravimetric analysis-differential scanning calorimeter (TGA-DSC).

5.5.3

Microplastic Dispersal from Point Sources in the Sea Region

MPs originate from diverse sources, including personal care products, synthetic textiles, and industrial effluents. These sources can be categorized into two sources, primary and secondary sources. Primary macroplastic emissions predominantly result from suboptimal municipal waste management, particularly open dumping and inadequate landfills, constituting 50% of environmental macroplastic pollution. Secondary sources include improper consumer waste disposal and loss of maritime equipment during oceanic activities (Ryberg et al., 2018). The ubiquitous presence of MPs in aquatic ecosystems poses significant threats to both aquatic biota and human health due to their small size, facilitating ingestion by a wide range of marine organisms. This ingestion can lead to toxic effects, disrupting biological functions and potentially bioaccumulating through trophic transfer, ultimately exposing humans to these harmful particles via contaminated seafood consumption (ElizaldeVelázquez & Gómez-Oliván, 2021). The fate, dispersal and accumulation of microplastics and their potential implications on human health and the environment are illustrated in Figure 5.4.

Primary MPs source

Personal care products Nurdles Drinking water

Industrial airborne dust

Storm

Secondary MPs Source Agriculture soil

Fragments

Fibers

Plastic Industry

Microbeads WWTP

Seafood

drain Effluen

t

Leachate Landfill Groundwater

e rin tem Ma osys ec

Sediment ingestion Biota

Deep sea

Figure 5.4 Fate, Dispersal, and Accumulation of MPs and Their Potential Implications on Human Health and the Environment

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5.5.3.1 Primary Sources

Plastic manufacturing industries: The excessive production of plastic material due to our daily lifestyle may generate tiny MPs as byproducts, which can find their way into nearby waterbodies. Wastewater treatment plants: Treated water from wastewater treatment plants can contain MPs derived from various sources, such as Personal care products (PCPs), microbeads and fibers (Hamidian et al., 2021). The existing treatment plant may not be capable of effectively filtering out during the treatment process, leading to their release into nearby rivers. Stormwater Runoff: Urban areas are a major source of MP pollution due to their abundance of impermeable surfaces. Rainwater can carry and transport these tiny plastic particles from streets into rivers and ultimately the ocean. Open dumping and casual littering of plastic refuse: Improper disposal of plastic waste through illegal dumping or littering contributes significantly to MP pollution in the sea. Wind and water transport can disperse these tiny particles into deep marine sediments (Ryberg et al., 2018).

5.5.3.2 Secondary Sources

Contaminated sediments: MPs can settle and accumulate on the seabed. These sediments can then act as a secondary source, releasing pollutants back into the water column over time (Zhang, 2017). Mechanical breakdown: Larger plastic debris breaks down into smaller and smaller fragments over time, eventually forming MPs (14,000 MP particles were observed in 30 individuals, with an average of 21 per gram w.w. The thorough surveillance of seafood for MPs demands continuous monitoring and examining marine-based food items to determine the minuscule plastic particles present. This crucial procedure utilizes sophisticated analytical methods like spectroscopy, chromatography, and microscopy to accurately identify and describe MP pollutants in different seafood samples (Mikulec et al., 2023). However, the current focus of many methods is on larger MP fractions (>100 μm), necessitating further development to accurately detect smaller microplastics ( 0.05), suggesting that stress responses are not influenced by time (Nyaga et al., 2024). A similar investigation of meta-analysis, covering different aspects of the toxicity related to MPs has been presented in the chapter; however, there are certain constraints that must be acknowledged, such as disparities between controlled laboratory settings and real-world environmental conditions, variances in the types and levels of coexisting pollutants, inconsistencies in environmental factors, and variations in the fish species used

6.5 Determining Relative Levels of Confidence Regarding Toxicological Data

in experimental studies. It is essential to address these differences in order to have a complete understanding and precise evaluation of health risks in both controlled laboratory settings and natural situations. Zazouli and coresearcher analyzed the occurrence of MPs in the gt of fish, and findings revealed that the pooled occurrence of MPs in the gt of fishes was 2.76 particles per gt (P/gt), with a 95% confidence interval ranging from 2.65 to 2.86 P/gt (Zazouli et al., 2022). Notably, the occurrence of MPs in the gt of fishes from closed water sources (5.86 P/gt) was higher compared to those from free water sources (2.46 P/gt). Furthermore, the rank order of water sources based on the occurrence of MPs in the gt of fish was as follows: Lake (5.50 P/gt) > estuary (5.46 P/gt) > river (2.91 P/gt) > bay (2.85 P/gt) > sea (2.58 P/gt) > ocean (1.29 P/gt). Interestingly, the lowest and highest occurrences of MPs in the gt of fishes were observed in high-income economies (1.45 P/gt) and low-income economies (8.08 P/gt), respectively. A systematic meta-analysis was undertaken to investigate the occurrence of MPs in different seafood species to affect humans (Danopoulos et al., 2020a). The analysis showed that a considerable fraction of investigations indicated contamination of MPs in seafood. The investigation examined four key organisms, namely, mollusks, crustaceans, fish, and echinodermata. It revealed that mollusks supplied from Asian coastlines are most vulnerable to heavy contamination, which is consistent with the overall pattern of MP pollution in marine ecosystems. The quantitative examination revealed the range of MP content in different seafood groups. Mollusks had levels ranging from 0 to 10.5 MPs/g, crustaceans from 0.8 to 8.6 MPs/g, fish from 0 to 2.9 MPs/g, and echinodermata at 1 MPs/g. Significantly, the highest estimated yearly number of MPs particles that humans can consume through seafood was found to be around 55,000 particles. This highlights the need to consider this pathway as a potential source of exposure for humans. Further, Danopoulos and coresearcher performed a systematic review and metaregression analysis of 17th research to examine the effects of MPs on human cells (Danopoulos et al., 2022). The focus was on understanding the potential negative health effects that may arise from everyday exposure to MPs through ingestion and inhalation. The investigation emphasized the importance of doing in vitro toxicological studies when there is a lack of epidemiological data in order to determine the link between dosage and reaction. The findings indicate that MPs had an impact on four out of five biological indicators examined, including cytotoxicity, immunological response, oxidative stress, and barrier characteristics. Further, it was observed that the irregular shape of MP was a major factor in predicting cell death, with environmentally relevant doses of 10 μg/mL and 20 μg/mL negatively impacting cell viability and cytokine release, respectively (Danopoulos et al., 2022). In addition to food sources, other consumables such as salt, spices, and other ingredients can also become the source of MPs in the human body. In this regard, a systematic review and meta-analysis were performed to examine the occurrence of MPs in salt that is meant for human consumption (Danopoulos et al., 2020a). The investigation uncovered substantial variations in the amounts of MPs contamination among different sources of salt. Sea salt showed a wide range of 0–1,674 MPs/kg, lake salt ranged from 8 to 462 MPs/kg, and rock and well salt ranged from 0 to 204 MPs/kg. Estimates of potential human exposure to MPs by salt consumption varied from 0 to 6,110 MPs/year from all sources (Danopoulos et al., 2020a). Further, the investigation emphasizes that during the process of gathering evidence,

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significant variation was observed in the statistical results, sample characteristics, and methodological approaches used in different investigations (Danopoulos et al., 2020b). Therefore, conducting more rigorous research using standardized methods is imperative to enhance our knowledge of MPs contamination in seafood, salt, and other sources and its impact on human health.

6.6

Conclusion

The escalating presence of MPs in the global environment has prompted significant concern, particularly regarding the intricate threat posed to ecosystems and human health by the combined exposure of MPs and typical pollutants. The chapter offers a systematic overview of the interaction between MPs and associated pollutants from the perspective of TK and TD. These MPs can act as vectors or sinks for pollutants, potentially increasing or decreasing their bioaccumulation or exerting no effect. Moreover, MPs can directly or indirectly modulate the toxicity of pollutants in human body. The characteristics of MPs and exposure scenarios significantly impact the bioavailability of pollutants, thereby influencing toxicity. Further, the size of the MPs has not been found in correlation with the toxicity and needs extensive investigation to fulfil the lacuna of the toxicity mechanism. In this regard, the meta-analysis-based investigation using a large and diverse data set can improve the understanding of MP’s toxicity. Future research endeavors should target the identified research gaps, such as the interaction of biota and MPs, environmental consequences of MP uptake, and biological pathways for microbial degradation to facilitate the development of a comprehensive risk assessment framework for MPs and typical pollutants.

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7 Understanding Environmental and Socio-economic Risks Associated with Microplastics Azhan Ahmad1, Monali Priyadarshini2, Makarand M. Ghangrekar1,2, and Rao Y. Surampalli3 1

Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal, India 3 Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 2

7.1

Background

The widespread use of plastic has aided the convenience of modern-day life owing to its application in different consumer products, which have been used every day by humans. The first synthetic plastic was identified in 1907 and was known as Bakelite (Alvarez-m et al., 2024). The research field of polymer and environmental science has been revolutionized by introducing numerous novel polymers and plastic formulations into our daily lives. In 2020, global plastic production reached more than 350 million tons (Mt), out of which between 1 and 2 Mt. of plastics reaches into the ocean annually (Güllü et al., 2024). Owing to their low density, low electrical and thermal conductivity, and corrosion resistance, plastic materials are incredibly flexible and can act as an oxygen and water barrier in different applications. Moreover, their affordability and low cost also make them simple to manufacture and widely used in a variety of applications, from food packaging to technological and medical usage (Swetha et al., 2023). However, due to their wide-scale applications and unregulated disposal laws, plastics are generally detected in freshwater and marine ecosystems, making them an environmental hazard. For example, underwater mammals, fish, birds, and reptiles can suffer harm or even die as a result of plastic aggregation and digestion. Also, due to their small size, plastics may cause bioaccumulation and biomagnification issues for various marine species (Bilal et al., 2023). On the other hand, under naturally occurring environmental circumstances in aquatic ecosystems, such as ocean current dynamics, sun radiation, abrasion, and interactions with aquatic organisms, plastic objects disintegrate and break into tiny particles known as microplastics (Bellasi et al., 2020). The existence of microplastics in the aquatic ecosystem can cause an appalling problem that might economically influence industries like agriculture, aquaculture, tourism, and others. For instance, using plastic mulches to cover the topsoil and decomposing plastic trash in nearby agricultural fields can contaminate the soil (Huang et al., 2020). As a result, crop growth and soil health might deteriorate, which could

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lower agricultural yields and raise production costs. Apart from this, the presence of microplastics can also impact the social life of humans. The social harm associated with microplastics includes hazards to human health and a deterioration in a particular location’s architectural, recreational, or educational standards (Mofijur et al., 2021). In this regard, this chapter discusses the interaction between microplastics and their farreaching environmental and socio-economic risks. Moreover, their widespread presence in the environment and their pathway to aquatic ecosystems, agricultural lands, and food chains, which cause multifaceted challenges for industries, economies, and societies, have also been elucidated. In addition, a way forward and potential mitigation strategies for minimizing the impact of microplastics on human life and for the economic well-being of societies have been highlighted. This chapter assists readers in enhancing their understanding of the environmental and socio-economic impacts of microplastics, paving the way for a more sustainable future where the adverse effects of microplastics are reduced.

7.2

Economic Impacts

Microplastics are used in various industrial applications; as a result, every day about 1.5 million plastic particles reach the oceans (Swetha et al., 2023). Apart from environmental consequences, microplastics can adversely affect the economics of the industrial sector. According to a report, only 5% of the cost of plastic packaging material is held in the economy; the remaining is lost after a very short first use (Hahladakis & Iacovidou, 2018). In Europe, littering, leaks from landfills, and losses of pellets during logistics, such as shipping, are major concerns. These issues are estimated to cost the economy between €70 and €105 billion. Microplastics can also influence small-scale businesses. For example, more than 45% of commercial fishers in the east US had entangled propellers, 30% had fouled gear, and more than 35% had plastic trash clogging their engine’s cooling system (Nguyen et al., 2022). In this case, repair expenses and lost fishing days could be significant for uninsured small-scale fishing. A report by Kommunernes International Miljo-organization (KIMO) International revealed that in the worst scenario, the Shetland Islands (population of 22,000) might pay up to €7.0 million/year resulting from marine debris annually (Hall, 2000). Hence, these instances proved that the presence of microplastics in the environment can economically affect different sectors. The occurrence of microplastics in aquatic ecosystems has substantial economic repercussions on sectors such as fishing, agriculture, healthcare, food production, and tourism. Microplastics tend to bioaccumulate in fish tissues, limiting their quality and market value. Also, concerns about food safety were raised by the presence of microplastics in seafood, which might also adversely affect the economic viability of the food industry. Therefore, this section deals with the economic impacts of microplastics on different industries. i) Fish Industry: The fishing sector is one of the largest industries supporting the global economy. About 12% of the world’s population is supported by global yearly fisheries earnings, which is around US $100 billion, and nearly 2.9 billion people receive 20% of their animal protein from fishing (Steer & Thompson, 2020). Fish and other aquatic creatures may be harmed by microplastic contamination of maritime habitats. These

7.3 Social Impacts

ii)

iii)

iv)

v)

7.3

habitats are used for fishing and may become contaminated by microplastics. Fish and other marine species may consume these microscopic plastic particles, which could cause bioaccumulation and biomagnification in the food chain (Cole et al., 2013). This disturbance of ecosystems and fisheries may impact fishing communities’ livelihoods and the economics of the seafood sector. Shipping and Transportation Industry: The buildup of microplastics in water bodies can cause biofouling of ships and other marine infrastructure. This might also elevate the shipping industry’s maintenance expenditure and fuel consumption. In addition, the presence of microplastics in marine environments can risk the lives of ship workers. For instance, in 1993, a passenger ferry off the west coast of Korea was entangled in a 10 mm nylon rope wrapped around the propeller shafts on both sides of the ship, including the right propeller. This caused the ship to abruptly turn, capsize, and sink, killing 292 of the 362 people on board (Steer & Thompson, 2020). Hence, these pollutants can give rise to navigational hazards for marine traffic, from shipping to recreational users. Food Industry: A number of food items, such as seafood, salt, and bottled water, have been linked to microplastic contamination. Contamination of food items can lead to additional testing and quality control measures, product recalls, and consumer complaints, all of which can adversely affect the financial health of the food sector. Tourism Industry: Beaches and shorelines along the coast are particularly vulnerable to deprivation due to microplastic contamination, which lowers their recreational and aesthetic value. Microplastic buildup on beaches can discourage visitors, which has a detrimental effect on coastal communities’ tourism income. Tourists frequently participate in marine biodiversity activities like scuba diving, snorkeling, and wildlife viewing. However, microplastic pollution can damage marine environments and marine life, making these activities less appealing, thereby affecting the tourist experience. In addition to tourism loss, beach cleaning also impacts the economy of the tourism sector. According to a 2009 UK report, the annual cost of marine litter clearance for all United Kingdom local authorities is estimated to be around £14 million (Mouat et al., 2010). However, this amount has probably risen significantly in recent years due to the increase in plastics manufactured. Healthcare and Waste Management Industry: Microplastics have been found in drinking water, raising concerns about the potential health risk. Thus, high water treatment expenditure and healthcare costs related to the potential health effects of microplastic exposure might influence the healthcare industry (Rahman et al., 2021). On the other hand, for waste management facilities, handling microplastics in waste streams might provide difficulties in separation and recycling, leading to amplified waste management costs and possibly reduced recycling rates.

Social Impacts

Microplastics are ubiquitous in the environment across the globe, even in some pristine polar environments. This is primarily because human civilization heavily relies on plastics for daily tasks and has unscientific disposal procedures to manage plastic. Moreover,

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microplastics might possess substantial effects on human societies. The researchers have mostly investigated the ecological impacts of microplastics, such as their consumption by marine organisms and their influence on ecosystem contamination. However, limited discussion has been highlighted on their social impacts. Thus, in this section, a few of the significant social impacts of microplastics have been elucidated. i) Concerns for Human Health: Microplastics can enter the human body through a number of different channels, including skin contact, inhaling airborne particles, and consuming contaminated food or water. Microplastics may have negative health impacts, such as oxidative stress, inflammation, and possibly even cancer. These medical issues may result in higher medical expenses and a worse standard of living for impacted families. The early effects of microplastics upon entering the human body have not been well studied (Revel et al., 2018). Certain researchers have postulated that microplastics may be incorporated into cells by either macrophages or blood vessel endothelial cells. Even though microplastics can penetrate the bloodstream, little information is available about how they are distributed and metabolized throughout the body. A demonstration presented at a conference in Vienna (2018) confirmed the presence of microplastics in the human gut despite the gaps in their uptake and transport (Katyal et al., 2020; Quenqua, 2018). The presentation reported that stool samples of eight individuals from different countries contained up to nine different types of microplastics (Katyal et al., 2020; Quenqua, 2018). However, the sample size of this pilot investigation was modest. Nonetheless, the presence of microplastics near the end of the human digestive tract indicates that these pollutants are present in the environment and are returning to humans, thereby affecting their lifestyle. ii) Economics and its Related Impacts: The fishing and tourist industries may be negatively impacted by microplastic pollution. Fishing communities and the seafood industry may suffer financial losses as a result of pollution of maritime ecosystems, which can also negatively impact fish stocks and seafood quality. Whereas, due to unfavorable opinions of the environmental quality caused by the occurrence of microplastics, coastal communities impacted by these contaminations may also see a decline in tourism-related income. Therefore, the loss in business can bring a decline in the social status of humans. For example, financial difficulties might harm mental and physical health. Financial hardships can make it difficult for some people to receive healthcare services, which might result in untreated illnesses and worse health consequences. Aside from stress-related illnesses and mental health disorders, economic downturns can also increase the prevalence of these conditions, placing additional burdens on social networks and healthcare systems. iii) Social Equity and Cultural Effects: The effects of microplastic contamination are not uniformly distributed, and underprivileged groups may be unreasonably affected. For instance, populations close to trash disposal or plastic production operations may be more susceptible to the health concerns associated with microplastic exposure. Furthermore, the economic effects of microplastic contamination may be dangerous for low-income populations that depend on agriculture or fishing for subsistence. On the other hand, the land, water, and other natural resources that indigenous peoples and other cultural and traditional societies depend on for survival are threatened by

7.4 Environmental Sensitivity and Variability of Microplastic

microplastic pollution. The resilience and well-being of these communities can be undermined by cultural identity erosion, the escalation of social injustices, the pollution of religious or culturally significant locations, contamination of traditional food sources, and cultural practices relating to environmental stewardship. Therefore, proactive steps must be taken to address the impact of plastic pollution on social equity and preserve cultural traditions. iv) Public Concern and Engagement: Apart from the adverse social effects of microplastic, a few positives have also arisen due to this environmental hazard. Growing public knowledge of microplastic pollution has raised public awareness of environmental issues and encouraged public participation. Action is being demanded by the public, advocacy organizations, and legislators to lessen plastic waste and lessen the negative effects of microplastics on ecosystems and public health. Having more people aware of the issue can help build community resilience and give them the confidence to participate in local, national, and international initiatives to combat plastic pollution.

7.4

Environmental Sensitivity and Variability of Microplastic

The environmental sensitivity of microplastics relates to their propensity to cause havoc to ecosystems and public health. Multiple factors influence the sensitivity of microplastics to the environment as discussed in details further. i) Toxicity: The toxicity of microplastics is mainly determined by their size and structure (Figure 7.1). Microplastics, especially those smaller than 1 μm, possess a greater surface area-to-volume ratio, which enhances their ability to interact with biological cells and tissues (Thacharodi et al., 2024). In addition, specific microplastic forms, such as fragments with sharp edges or fibers, can physically harm living organisms when they ingest or come in contact. Microplastics comprise different polymers and contain colorants, adsorbed chemicals, and additives. The chemical content of microplastic determines their toxicity. For example, a few polymers can produce harmful monomers or intermediates byproducts and additives, which might leak out and cause negative consequences. Furthermore, these microplastics can readily be adsorbed by heavy metals and other chemical pollutants that are found in the surrounding environment. Upon ingestion, these adsorbed pollutants can enter the digestive tracts of organisms and may cause toxic effects. The surface characteristics, such as hydrophobicity and roughness of these microplastics, affect the attachment of microbes on their surface (Ma et al., 2020). Microbes typically grow on the surface of microplastics, where they release toxins, enzymes, or other compounds that change the toxicity of the material. Microplastics are continuously exposed to organisms because of their long half-lives and ability to persist in the environment for years. The accumulation of microplastics in sediments might cause chronic exposure to organisms that live in or ingest the sediments. Many stressors, including chemical contaminants, temperature variations, and changes in pH, can cause microplastics to interact with the environment (Sun et al., 2020). For instance, a pH of 9.0 or higher was shown to be desirable for the effective sorption of polyvinyl chloride (PVC); however, pH 8.0 or 5.0 was found to be adequate

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Primary microplastic

Waste and domestic runoff containing microplastic reaches waterbodies

Microplastic containing effluent

Personal care products containing microplatics Secondary microplastic

Environmental toxicity

Improper disposal causes plastic fregmentation

Toxicity determinants

Persistance and accumulation: Chronic exposure

Chemical contaminants: additives, pollutants

Microplastic exposure on biota

Microplastics

Aquatic plants

Corals

Seabirds

Crustaceans

Larger mamals

Fishes

Seaanimals

Planktons

Microplastic exposure on biota

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Surface properties: charge, roughness

Physical characteristics: type, size, color, shape

Interaction with other stressors like pH and temperature

Species specific factors: Feeding behaviour

Physical damage Nutrient blockage Reduced feeding efficiency Internal injuries Increased mortality Altered foraging behavior

Figure 7.1 Overview of Occurrence, Toxicity, and Various Factors of Microplastic Toxicity on Aquatic Ecosystem (Source: Thacharodi et al. (2024) / Elsevier)

for persulphate (PS) sorption (Fred-ahmadu et al., 2020). Moreover, the physical and chemical properties of microplastics are important in determining their toxicity and bioavailability. Furthermore, the sensitivity of organisms to microplastic toxicity might be influenced by dietary practices, digestive physiology, and tolerance mechanisms. ii) Bioavailability: Microplastics ranging from micrometers to millimeters can be consumed by many species, from plankton to larger marine animals. Due to their tiny size and similarity to food particles, these substances are readily assimilated by organisms and can undergo bioaccumulation and biomagnification within food webs. For instance, investigations have demonstrated that microplastics have been discovered in fish, marine

7.5 Toxicological Impact of Microplastics on Aquatic Organisms

animals, birds, and even tiny plankton digestive systems (Cole et al., 2013). Ingestion is one of the key ways that microplastics enter living things and become bioavailable. These microplastics are generally absorbed and consumed by organisms via different routes. The microplastic particles can be consumed by fish and other aquatic species and could enter their bloodstream (Koelmans & Ruijter, 2022). In addition, organisms can absorb microplastics directly via their body surfaces or by means of the epithelial tissues of their digestive tracts (Wright et al., 2013). Once ingested, they can circulate across the tissues of organisms. Investigations have demonstrated that microplastics can find their way into various tissues and organs, such as the kidneys, liver, stomach, and circulatory system of the organisms (Wang et al., 2020). For instance, it was observed that high-density polyethylene (HDPE) accumulated in the lysosomes of mussels after being exposed to 3 h (Burkhardt-holm, 2012). Since microplastics cannot be digested, they can penetrate easily through cell membranes and enter the innermost layer of the intestinal epithelium to the blood vessel (Galloway et al., 2010). The bioavailability of microplastics is illustrated by the tendency to interact with and affect species across different ecosystems. Identifying the processes of intake, accumulation, and possible effects of microplastics is vital in evaluating the threats they represent to organisms and habitats (Thacharodi et al., 2024). It also highlights the significance of implementing measures to minimize microplastic pollution and safeguard the health of both terrestrial and aquatic environments. This highlights the need to implement strategies to lessen microplastic contamination and safeguard the health of both terrestrial and aquatic ecosystems. iii) Bioaccumulation and Biomagnification: Microplastics have the tendency to both bioaccumulate and biomagnify within the food chains (Kim et al., 2023). Microplastics can eventually build up in an organism’s tissues after ingestion, and this accumulation can intensify as it moves up the food chain. However, when predators eat smaller animals that already have microplastics, it results in biomagnification (Farrell & Nelson, 2013). This mechanism can result in elevated concentrations of microplastics in the species occupying higher trophic levels. It is crucial to note that the impacts of microplastics can differ based on several factors, including the form, type, concentration, and size, along with the characteristics of the species and ecosystem involved. Nevertheless, the overall influence of microplastics on terrestrial and aquatic creatures emphasizes the pressing necessity to combat microplastic contamination and adopt mitigation actions to protect the organisms that are reliant on them. Furthermore, evaluating and forecasting the ecological effects of microplastics requires an understanding of the mechanisms determining microplastic toxicity. This understanding allows policymakers and researchers to locate the key reasons driving toxicity and devise ideal methods to eliminate the damaging impact of microplastics on organisms.

7.5 Toxicological Impact of Microplastics on Aquatic Organisms Microplastics can potentially cause an extensive array of adverse effects on aquatic organisms. The main effects include ingestion and physical implications, growth and replication inhibition, accumulation and magnification, chemical toxicity, alterations in physiology

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and behavior, and ecological repercussions (Palmer & Herat, 2021). Aquatic creatures, including fish, filter-feeding invertebrates, and zooplankton, typically swallow microplastics, often misidentifying them for food. This might result in physical injury, gastrointestinal obstructions, decreased nutrient absorption, and lowered feeding capacity (Cole et al., 2013). The consequences of microplastic toxicity on aquatic biota are shown in Figure 7.2. Microplastics seriously threaten fish, and several investigations have documented their toxicity. Lu and coworkers discovered that microplastics can interrupt fish growth rates, reproduction efficiency, and immune system function (Lu et al., 2021). The research conducted by Koelmans and his team shows that microplastics can bioaccumulate in fish, leading to a gradual increase in concentration over time (Koelmans & Ruijter, 2022). Microplastics can biomagnify within the food chain, potentially resulting in elevated exposure concentrations for predatory fish (Setälä et al., 2014). In addition, microplastics can adsorb contaminants, including polycyclic aromatic hydrocarbons and polychlorinated biphenyls (Rochman et al., 2013). When fish consume these microplastics, the absorbed toxins that have been released into their gastrointestinal tracts, which can result in chemical toxicity and adverse health effects. The fish that are exposed to microplastics can develop behavioral shifts, altered swimming habits, and lessened predator–prey relationships. Moreover, microplastic contamination can also lead to stress, which affects the physiology and overall health of fish (Wright et al., 2013). Research findings have demonstrated that sharks can encounter microplastics through ingestion or gills absorption. The existence of microplastics in the gastrointestinal system

Biomagnification to higher tropic level Accumulations of microplastic Phytoplankton

Zooplankton

Altered nutrient recycling

Food web disruption

Genetic and epigenetic effects

Habital alteration

Disruption of species interaction and community dynamics Figure 7.2 Ecotoxic Effect of Microplastic on Aquatic Ecosystem (Source: Thacharodi et al. (2024) / Elsevier)

7.6 Strategies for Managing Microplastic in the Environment

of marine mammals can cause physical injury, impede the absorption of nutrients, and reduce feeding efficacy. For instance, in vivo testing of microplastics on mice revealed that consuming 0.01 mg of 5 μm polystyrene microparticles per day can lead to a reduction in its spermatogenic cells and a lower sperm count after 42 days of exposure (Xie et al., 2020). Also, Zhao and coauthors revealed that microplastic exposure (100 μg/L) disturbs hepatic metabolisms in adult Danio rerio (54 samples) after 21 days of exposure (Zhao et al., 2020). The disturbance in hepatic metabolism was evaluated by the alteration in body weight of D. rerio after microplastic exposure, which was decreased to 0.32 ± 0.01 g from 0.40 ± 0.01 g (Zhao et al., 2020). Thus, revealing toxicity towards the D. rerio. Besides, whales can consume microplastics through contaminated prey, potentially leading to digestive issues and a decrease in appetite (Besseling et al., 2017). Microplastics have been detected in the stomachs of seals and sea turtles, posing substantial risks like intestinal obstructions and lacerations. Likewise, chemical contaminants like polybrominated diphenyl ethers and polychlorinated accumulate or are absorbed through microplastics. When the seabirds intake microplastics with these adsorbed chemicals, it can lead to chemical toxicity, impacting their reproductive outcomes, immune response, and health. A case study discovered that 64.54% of the 110 sea birds of ten distinct types contained plastic substances in their gastrointestinal tracts. There were 890 plastic fragments found in the digestive tract, most of which were in the shape of pellets (35.95%) and plastic users (62.92%) (Barbieri, 2009). Coral reefs are rich and diversified ecosystems that offer habitat for many marine species. Unfortunately, they face multiple challenges due to various factors, such as predation, sponge overgrowth, coral bleaching, and the rising presence of microplastics in the environment due to inadequate waste disposal practices (Thinesh et al., 2017; Reichert et al., 2019). Microplastic contamination poses an imminent danger to coral reefs, potentially causing toxicity that affects the health and functionality of the corals. Therefore, it is essential to understand the toxicity of microplastics in corals to develop preservation strategies and lessen the detrimental impact on coral reef ecosystems. Microplastics can affect corals in various ways, including (a) physical effects, such as tissue damage and abrasion from sharp particles, and (b) chemical toxicity, which can cause oxidative stress and impair coral immune responses (Meenatchi et al., 2020). A case study indicates that A. muricata exhibited reduced growth, displaying a surface area 33% less than the control when exposed to microplastics (Reichert et al., 2019). Similarly, microplastics can alter the microbial populations associated with corals, interrupting symbiotic relationships and decreasing the resilience of coral reefs against additional pressures such as temperature changes and ocean acidification (Kumar & Sachdeva, 2021).

7.6

Strategies for Managing Microplastic in the Environment

A multifaceted strategy comprising an involvement of a range of stakeholders, including governments, businesses, communities, and individuals, is required to mitigate the consequences of microplastics on the environment. A wide range of national and international governmental organizations, ecological protection organizations, and management groups have put strategies and guidelines into place to protect the environment from the damaging

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effects of microplastic contamination on aquatic flora and wildlife. Besides, different ecosystems can be effectively prevented from becoming contaminated by implementing microplastic cleanup at the right sources. Also, globally, implementing waste management policies under environmental laws can be beneficial in restricting or minimizing the use of microplastics in day-to-day life. For instance, single-use plastic bags are banned in California, while plastic-based packaging is restricted in Massachusetts (Thacharodi et al., 2024). Similarly, the use of plastic bags is restricted at the institute level in India. For example, IIT Kharagpur, India has restricted the use of plastic bags to carry consumer products. Thus, these actions support sensible waste management techniques. On the other hand, setting up and enforcing regulatory laws for using microplastics in products can help restrict the production of these pollutants. For example, the Canadian government completely outlawed the use of microbeads in cosmetics within the nation by passing the “Environmental Protection Act” (Pettipas et al., 2016). Furthermore, controlling the pollution caused by microplastics in harbors, marinas, and industrial areas is a crucial environmental issue that calls for a multifaceted strategy. Preventive and remedial measures should be included in effective management strategies. To stop microplastics from entering these delicate ecosystems, stricter rules for disposing of plastic trash must be put in place, and the usage of biodegradable materials must be encouraged. Moreover, frequent monitoring of sediment, water quality, and aquatic life is necessary for tracking the intensities of microplastics in the environment and evaluating their influence on plants, animals, and humans. Furthermore, installing efficient filtration systems at industrial sites can considerably decrease the release of microplastics into water bodies. At last, advanced technology-driven clean-up programs, such as dredging sediment and using specialized skimmers, can be used in conjunction with community-led clean-up operations to address the existing contamination problem of microplastic in the environment. Thus, imposing all these actions together might be beneficial to lessen the adverse environmental effects of microplastics and save ecosystems for future generations.

7.7

Conclusion and Way-forward

Microplastic has a huge influence on our daily lives and it is widely used in different applications, making it one of the most influential materials of the twenty-first century. Although plastics have many positive economic effects, they are also one of the primary environmental pollutants, endangering human health, ecosystems, and other forms of life. These pollutants could have a significant effect on both human health and marine bacteria. Microplastics are light and tiny, making it easy for marine life to consume them quickly, which leads to waste accumulation in tissues, the brain, and circulatory systems. Besides, microplastic pollution also exacerbates socioeconomic gaps and weakens community resilience due to its financial consequences, which include pollution cleanup costs, healthcare costs, and effects on livelihoods. Tourism is significantly impacted financially by microplastics, as it is difficult to completely eradicate the presence of microplastics from the environment. These contaminants are certain to continue growing in number and diminishing the

References

aesthetic, recreational, and historical value of an environment. Therefore, integrated approaches must be adopted that bridge disciplinary boundaries and include stakeholders from several sectors to tackle the complicated problems that microplastics present. Reducing plastic usage, enhancing waste management procedures, and promoting sustainable alternatives are all necessary to build resilience against microplastic pollution. Further investigation must be carried out on the effects of microplastics at environmentally relevant concentrations. In addition, research on the interactions between microplastics and other pollutants is still in the embryonic state. Hence, to fully comprehend the environmental implications of microplastics and their possible effects on human health, future research must assess a wider range of chemical contaminants, microplastics, and aquatic animals. Finally, with far less knowledge, future research should concentrate on the impact of terrestrial climate on the microplastic. Thus, using interdisciplinary expertise, community participation, policy interventions, and future scientific research on microplastic and their interaction with the environment. Societies can strive toward a more unrestricted and sustainable future, where the hazards posed by microplastics to ecosystems, economy, and human societies are reduced.

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Wang, T., Wang, L., Chen, Q., Kalogerakis, N., Ji, R., & Ma, Y. (2020). Interactions between microplastics and organic pollutants: Effects on toxicity, bioaccumulation, degradation, and transport. Science of the Total Environment, 748, 142427. https://doi.org/10.1016/ j.scitotenv.2020.142427 Wright, S. L., Rowe, D., & Thompson, R. C. (2013). Correspondences Microplastic ingestion decreases energy reserves in marine worms. CURBIO, 23, R1031–R1033. https://doi.org/ 10.1016/j.cub.2013.10.068 Xie, X., Deng, T., Duan, J., Xie, J., Yuan, J., & Chen, M. (2020). Exposure to polystyrene microplastics causes reproductive toxicity through oxidative stress and activation of the p38 MAPK signaling pathway. Ecotoxicology and Environmental Safety, 190, 110133. https://doi. org/10.1016/j.ecoenv.2019.110133 Zhao, Y., Bao, Z., Wan, Z., Fu, Z., & Jin, Y. (2020). Polystyrene microplastic exposure disturbs hepatic glycolipid metabolism at the physiological, biochemical, and transcriptomic levels in adult zebrafish. Science of the Total Environment, 710, 136279. https://doi.org/10.1016/ j.scitotenv.2019.136279

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Section II Microplastics in Different Compartments and their Effects on Environments and Humane Society

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8 Microplastics in the Environment Sources, Distribution, Fate, and Transport Hua-Bin Zhong1, Ying-Liang Yu1, Chih-Ming Kao1, Rao Y. Surampalli2, Tian C. Zhang3, and Bashir M. Al-Hashimi4 1

Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 3 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 4 King’s College, Strand Campus, London, UK 2

Microplastics (MPs), defined as plastic particles smaller than 5 mm, are mostly made up of polyvinyl chloride (PVC), nylons, and polyethylene terephthalate (PET), which sink, and polyethylene (PE), polypropylene (PP), and polystyrene (PS), which float. Polyvinyl alcohol (PVA) and polyamide (PA) are two more polymers. This chapter delves into the pervasive issue of MPs in the environment. These particles, originating from various consumer products and industrial sources, have become a significant concern due to their durability and widespread presence in marine, terrestrial, and freshwater systems. The chapter aims to address the substantial gaps in our understanding of MPs’ sources, how they distribute across different environments, their fate, and their transport mechanisms. By providing a comprehensive review, this text will explore the potential long-term effects of MPs, their bioaccumulation, and their overall impact on ecosystems. The structure of the chapter includes an introduction to MPs, an exploration of their environmental entry points, an analysis of their global distribution patterns, and a discussion on their environmental behavior and transport pathways. It concludes by highlighting the current research deficits and suggesting future research directions to help policymakers and environmental organizations develop effective mitigation and management strategies.

8.1 MPs in the Aquatic Environment (Surface/Ground Waters and Ocean) MPs have recently gained a lot of attention as an emerging pollutant of concern around the world. As shown in Figure 8.1, MPs are widely detected in aquatic systems from two sources: primary and secondary MPs. Primary MPs are those created for usage in a wide range of consumer and industrial applications (e.g., abrasives in cosmetic scrubs). For example, toothpaste and other personal care items, such face cleanser, contain a lot of

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8 Microplastics in the Environment

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Figure 8.1 Possible Sources and Pathways of MPs in the Environment and Related Research on Microplastics

primary MPs (Guo et al., 2020). Secondary MPs are formed when bigger plastic and synthetic materials degrade due to weathering processes including ultraviolet (UV) degradation or machine washing. Secondary MPs constitute the vast majority of MP particles in marine systems, particularly in locations with dense populations. Recent research has shown that wastewater treatment plants (WWTPs) are substantial sources of MP particles, especially fibers. In the Great Lakes, primary plastics (“pellets” or microbeads) dominated the smallest size category (≤1 mm), whilst secondary plastics (fragments) dominated larger size classes. Many popular types of MPs found in consumer products (e.g., PP, high-/lowdensity PE) have densities lower than water, and PP and PE are especially sensitive to microparticle formation through breakdown. As a result, due to their densities, these MPs have the potential to be created by larger plastic debris and dispersed over vast distances across watersheds (Anderson et al., 2017). MPs are found all across the world’s oceans. Some float on surface waters and are commonly found in shorelines, seabed sediments, beaches, wastewater effluents, and even frozen ice. Some are found in the Arctic and Antarctic, where they are transported by ocean currents and wind. Because of their small size, MPs are easily ingested by a wide variety of creatures in the marine environment. MPs have been found in bivalves, zooplankton, mussels, fish, shrimp, oysters, copepods, lugworms, and whales. Ingestion of these MPs has been linked to pathological stress, false satiation, reproductive difficulties, restricted enzyme production, decreased growth rate, and oxidative stress in organisms. MPs can also absorb hazardous substances from the surrounding seawater, allowing them to enter the food chain.

8.2 MPs in the Terrestrial Environment (Soil and Sediment)

MPs have been found in increasing numbers and at very high levels in rivers and lakes around the world, according to studies. Because of their resistance to destruction by microbes, MP polymers persist in the environment. These MPs have been found near the surface of seas, in water columns, and in deep marine sediments all around the world. MPs have lately been discovered as a significant rising global problem that impacts marine species as well as humans. MP particle concentrations in surface waters have increased significantly over the previous four decades, and worry about the possible impact on the marine environment has grown in recent years (Auta et al., 2017).

8.2

MPs in the Terrestrial Environment (Soil and Sediment)

Quantification of the many sources of soil MPs is necessary. The movement and retention of MPs in soil are governed by their interactions with various characteristics and environmental elements (Figure 8.2). The function and health of the soil microbial–plant–animal ecosystem are threatened by the presence of MPs, which can also enter the human body through the food chain. However, the exact extent of these risks is still up for debate. The potential transport and ecotoxicological mechanisms of pollutants generated from and adsorbed by MPs as well as that of pathogens and other hazardous microorganisms attached to MPs as biofilms should receive special attention. MPs from different sources seep into the soil (Figure 8.3). Compost and mulch films used in agriculture could be the primary sources. Because mulching and greenhouses effectively improve crop quality and output, they are frequently utilized in agricultural production. The removal of plastic mulch film from the soil is a challenging task, particularly for thin films (8–50 μm), which can result in a significant build-up of plastic residues in agricultural areas. With the help of farming, UV light, and biodegradation, these wastes gradually transform into a blend of MPs and nanoplastics, which ultimately leads to significant issues with soil contamination. In extremely intensive agriculture, biosolids are reused to supply organic matter(OM) and a closed fertilizer loop. On the other hand, a significant amount of MPs as well as persistent organic pollutants (POPs) and heavy metals (HMs) are present in biosolids. Microplastics in soils: A review r so De

Effects and interactions on soil ecosystem

Human health

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PAEs

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Soil

Microbes

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Microplastics as a contaminant suites

Figure 8.2

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Environmental cycle

Occurrence

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Trophic-level transfer

Migration of Microplastics in Soil and Impact on Humans

Exposure risks Control

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Large plastics (Agricultural mulching film Garbage disposal, Landfill)

Raw materials from industry, cosmetics and medicine

Source

Biological processes

Primary MPs

Physical biodegradation

Secondary MPs

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Textiles and Tyre wear

Land application (Sludge utilization, Sewage irrigation, Compost)

Non-point pollution

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Non-point pollution

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Bioturbation

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Soil cracks pore

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Root Elongation decompose

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Horizontal distribution

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Groundwater Figure 8.3

Source and Transport of Microplastics in Soil

MPs were discovered in 70–99% of the obtained sewage effluent during the water disinfection procedure (from residential, healthcare facility, and manufacturing discharge), with a concentration of 103–105 items/kg. Massive MP accumulation occurs in the soil as a result of sewage sludge being applied to farmland repeatedly. Consequently, while the use of sludge-based fertilizers aids in the recycling of nutrients and OM on land, it is also important to take into account the possible effects on sustainability and food security that may arise from the large-scale movement of MPs and other hazardous materials from WWTPs to agricultural land (Zhou et al., 2020).

8.3 MPs in the Polar Region

Landfills also is a significant MP source for groundwater and soil pollution. With an average concentration of 13 items/L, MPs in landfill leachate are uncommon, but they also make up a tiny portion of the world’s soil MP contamination. Increased MP levels in terrestrial soils may result directly from other sources, such as road littering, illegal dumping, surface detachment of plastic covering, blasting of plastics during industrial processes (e.g., thermal cutting), illegal dumping, and tire wear (e.g., vehicles, planes). Various interior environments had varying degrees of microfiber (MF) deposition, and the discharge and spread of MF were typically related to the thickness of materials and the instability of the air requiring circulation. The material properties such as material structure, yarn type, and twist were also significant factors influencing MF release from textile sources and edge-cutting mode. Therefore, modifications to textile design may result in more successful interventions that lower environmental emissions. Given multiple contributors and remarkable quantities of MPs in the soil system, conceivable routes of MP pollution with the global situations should be quantified for the purpose to properly comprehend the ecological consequences of MPs and more accurately estimate both the present and the potential contributions of artificial waste made of plastics to terrestrial and marine MPs (van den Berg et al., 2020).

8.3

MPs in the Polar Region

Recently, it is thought that human-generated litter sinks to the Arctic. The question of how these pollutants get to those isolated areas is raised due to the distance between the Arctic and populated areas. According to some research, bio vectors like seabirds, which feed in the oceans and then expel what they have eaten into the environment when they defecate, may contain a potential transport trajectory. Several seabirds that live in the Arctic, like little auks (Alle alle), have large amounts of plastic debris in their stomachs. As little auks typically consume small prey (like copepods), they are able to mistake MPs for prey and mistakenly consume them during foraging. Then, after having assimilated MP items while preying in the oceans, these seabirds may defecate near a freshwater Arctic lake, completing the transport. Nonetheless, the findings of certain research on marine Arctic ecosystems discovered a concentration of MPs, in both subsurface and the water, comparable to that of other places. In the end, this was thought to be the outcome of a different possible transport mode, namely, long-distance transport (Figure 8.4). The fact that the types and shapes of the MPs in the sample were identical to those of other MPs found in some southern hemisphere seas supports the idea that they were transported to different locations. Furthermore, looking into the possible transport trajectory of MPs in snow from the Alps to the Arctic, a study discovered that while the materials’ chemical composition varied depending on the location, only a few materials—varnish, rubber, PE, and polyamide—dominated the areas under investigation. Moreover, the majority of the particles found in the snow in the Arctic were noticeably tiny. Therefore, it was concluded that MPs might have been transported from Europe to the Arctic by atmospheric transport and deposition. As a matter of fact, the phenomenon of dust transport by air is well-established and noteworthy. It is known

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O2

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Relative Reporting Frequencies of MPs’ Polymer Types

to deposit litter caused by humans in remote areas, like mountain lakes, and to transport particles over great distances, like from the Sahara to the North Atlantic. Therefore, it can be inferred that the most plausible route for the accumulation of MPs in the remote Arctic lake may have involved atmospheric transport and deposition (González et al., 2020). MPs have recently been found in samples from Finland’s Pikku Vesijärvi Pond and Vesijärvi Lake with the mean MP concentrations of 395.5 ± 90.7 MPs/kg (sediment sample), 117.1 ± 18.4 MPs/L (snow), and 7.8 ± 1.2 MPs/L (ice), respectively. The proximity of human settlements and the relatively high level of tourism that characterizes Vesijärvi Lake and Pikku Vesijärvi Pond justify the presence of MPs in sediments and ice, but it is difficult to determine the origins and sources of the MPs in the snow. It is true that contamination of snow can occur before and after deposition. The most common material in the snow samples was cellulose, which was followed in abundance by polyamides, PE, PP, polyacrylates, polyurethane, and polyacrylate–PET. An order of magnitude higher concentration of MPs was found in the snow samples than in the ice, suggesting that the samples were contaminated both before and after they were deposited. Snow particles stick to airborne pollutants like MPs as they descend through the atmosphere and land on Earth’s surface. It was shown, for example, that this process, known as “scavenging,” takes place in other parts of the world as well. Scavenging could play a role in the MP contamination of the Arctic snow near Pikku Vesijärvi Pond and Vesijärvi Lake, which occurs after the snow is deposited. It is likely that synthetic clothing worn by tourists participating in sports or other activities near the sites under investigation is the source of polymers like polyamides. It is shown that washing 6 kg of synthetic material can release up to 700,000 MP particles, and that wastewaters from clothing washing activities contribute significantly to the release of MP pollutants in the environment (Obbard et al., 2014).

8.4 MPs in the Atmospheric Environment and Transboundary Transport

The concentration of Antarctic MPs has been reported to be 0.01–0.08 items/m3, with “hotspots” primarily located in the Ross Sea and the waters surrounding the Antarctic Peninsula. The abundance of MPs in the surface seawater of the sea areas around Antarctica was 0.05–0.10 items/m3, and the main types of MPs were PE and PP. It was reported that the abundance of plastics in the surface seawater around the Antarctic Peninsula was 0.01 items/m3 and that 54% of the plastic items were MPs, with the main shape being fragment and the main type being polyurethane. Jones-Williams and colleagues studied the surface seawater from the Scotia Sea to the west Antarctic Peninsula. The researchers discovered that the concentration of MPs was 0.01 items/m3; the main shape of MPs was fragments; and the main types were PE and phenoxy/epoxy resins. The abundance of MPs in the Weddell Sea’s surface seawater is 0.01 items/m3; the main shape of MPs is fragmented; and the main type is polyester (Bergmann et al., 2022; Scopetani et al., 2019). In comparison to Arctic sea areas, Antarctic subsurface waters have a lower concentration of MPs. The abundance of MPs in the subsurface seawater of the Weddell Sea has been documented to be 0.04 items/m3 and 0.17 items/m3 in the Ross Sea. Unlike Arctic seawaters, which are dominated by MP fibers, Antarctic waters are dominated by debris, with PE, PP, and synthetic resin being the most common types. Subsurface MPs were collected in the Antarctic, Central Atlantic, North Atlantic, Barents Sea, and Siberian Arctic, and differences in size, shape, polymer composition, and weight concentration were discovered (Huang et al., 2023).

8.4 MPs in the Atmospheric Environment and Transboundary Transport Knowledge of the breakdown and disintegration properties of different plastics in the air is critical in comprehending MPs’ outside fallout. Because the molecular chains of polymers are easily broken by solar UV rays, PS, for example, generates secondary MPs very quickly in the air. Long-lasting plastics disintegrate more gradually in nature; however, they still produce MPs. It has been verified that wastewater mud, tires, and paint are all MP sources in the environment. The discharge of MPs into the atmosphere around them varies with geography (transit of water and soil, the surroundings, breeze) along with growth pattern (cultivation, organizations), just as plastic particulate matter aerial fallout rates vary with the spot (local emission) and PE type. Wind and the distance to source areas have an impact on the number as well as the features of airborne MPs. Wind speed, border layer mixing, temperature, and various other meteorological factors all have an effect on the flow of airborne PM–MPs. Because there are more manufactured MPs in aquatic as well as terrestrial ecosystems during winter months, rainfall and precipitation could affect atmosphere MPs. Rainfall causes a buildup of tiny outside small particles on the surface of the ground, which then escape back into the atmosphere. This happens via post-monsoon flows (flow from elevated to low-pressure zones), and thus pollutants in the air hotspots such as the Indo-Gangetic Plains regularly experience increased levels of fine PM (PM2.5) in the cold months. Storm winds play an important role in the cross-continental carry of hovering MPs. East Asian summertime precipitation, for example, could transport atmosphere MPs from

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Vietnam to southeast China via the Philippine peninsulas and Malaysia. Light-density MPs were found to be high in wind-eroded natural and farming implying that the breeze plays a major part in floating MPs (Brahney et al., 2020). MPs are reported to be receptive to wind attraction caused by wet and dry depositions. Studies on MP deposition rates in 11 sheltered national parks across the United States for two years discovered that 98% of raindrop samples contained MPs. The study established long-distance MP carry and precipitation into faraway protected forests. All air spaces (outside of debris and the encompassing air) may develop into a possible sink and contribute to MPs pollution in aquatic and terrestrial environments (Mbachu et al., 2020). Given that airborne MPs have less density than minerals found in the soil, they linger in the air for a period longer than natural sand aggregates of the same size, allowing them to travel to distant locations. As a result, MPs have the potential to be transported by the atmosphere to other biomes, including terrestrial, aquatic, and upward biomes. The quantity of clouds and the weather impact air–sea connections, which impacts global particulate shipping. In the global transportation of MPs, atmospheric currents are just as important as oceanic currents (gyres). Wind stress and wave action make sea salt-MP and disperse sources of energy released in aerosol form sea-surface atoms to cities within the coasts, which might additionally carry unidentified MPs, showing a field-based proof of the atmospheric movement of MPs that migrate to the underwater setting. A separate investigation discovered discrepancies in the sizes and compositions of legislators between airborne particles and precipitation in the atmosphere, implying that their transportation to the ocean has become significantly lower than riverine inputs as well (Zhou et al., 2021). Brush (especially at 0 C) and frost (especially in temperatures below around 10 C) can remove organic steam and nanoparticles from the atmosphere, thereby transporting airborne MPs and their compounds as well as formed copollutants to distant locations. MPs in polar sleet implying significant pollutants in Arctic air. The scavenging influence was mentioned by the researchers as a crucial route by which MPs may be shipped through the environment, travel via clouds, tie on snow, and end up in the Arctic tundra. MPs are extracted (wet/dry deposits) by clouds as they travel with atmosphere currents, leading species to receive precipitation in arid and aquatic niches. Remote Antarctica lakes get a potential sink for MPs, particularly MFs transported via call air transmission. The growing collection of MP parts in rural, fir trees, and urban regions has been blamed upon atmosphere public transportation (Selvam et al., 2020). They may represent pollutants sent by atmospheric absorption when combined with pavement rainfall and discharge in wastewater. Numerous studies around the world have documented MPs from different environments and commercial food samples, but most of them have been unable to estimate the contribution of upwards transportation in MP depositing. Hovering MPs are primarily caused by synthetic textile clothing, furnishings, construction debris, tire abrasion, and city dust. In addition, suspended MPs which are floating through the surrounding air as a result of released dirt from automobiles travel away and impacts aquatic or terrestrial ecosystems (Dris et al., 2017). An investigation on the presence of MPs related to street dusts revealed a previously unrecognized source of MPs in the air. Micro-rubber (MR) atoms and MPs (circles, motion pictures, and filaments) predominated street dust specimens (5 mm) taken at fifteen distinct points in Asaluyeh, southern Iran had a typical concentration of 900 MPs and 250 MRs per 15 g of sample.

8.4 MPs in the Atmospheric Environment and Transboundary Transport

The research team removed OM from 15 g aliquots with 35 mL of 30% H2O2, implying that all the recognized parts were synthetic. Based to the previous study’s findings, boosted automobile travel and urban roadways can generate synthetic MR particles through tire damage, resulting in floated PM. The tire along with paint aggregates are major sources for urban dust, contributing to MP input into the atmosphere. Latex paints, which normally combine water and materials for plastics, have become increasingly popular in recent years. According to several workspace studies, vehicular tire scratches are an important driver of MP particles in urban air. Researchers detected and measured synthetic tread aggregates in soil samples taken from highway drains in Plymouth, United Kingdom, and found that road tire wear aggregates contributed significantly to drainage MR pollution. Future research should focus on the ecological estimation related to urban in the outdoor pollutants caused by tire abrasion, in line with the findings gathered in the preceding studies. Tire abrasion MPs are typically fine particulate pollutants. Turning automobile tires (wheels) emitted and sent PM into the air via airflow along with powerful air currents. To comprehend MP abrasion and input from a tire or anything else, mathematical methods can be used (Järlskog et al., 2020). MPs may also be discharged by brake wear atoms, which are mainly made up of chemicals and metals (fibers, binders, padding, and so on that comprise the brake lining). Similarly, in latex paints, which normally combine water along with plastics, have gained popularity. MPs discharged from paint have become overlooked sources of either indoor or outdoor air pollution. MPs can be released into an indoor or outdoor setting by even disposable plastic bags. Plastic mulching films used on agricultural land may discharge high levels of MPs into the environment. Incineration is a possible, but insufficiently utilized, source of MPs in the atmosphere (Huang et al., 2020). Scholars discovered 360–102,000 parts/kg in MPs (especially PP and PS) in the bottom ashes of Chinese cities, implying that combustion could be a source of MPs expelled into the environment; however, the study did not report whether MPs were present in the fly ash of trash dumps, which may be a marker of airborne MPs. The collection of waste and landfill consequences have been identified as potential sources of MPs in the atmosphere. The soil near an e-waste dump in Guiyu, China, for instance, has been discovered to be heavily contaminated with MPs (up to 34,100 particles/kg), meaning that MPs could be transported through the surroundings. MPs were deployed in the air. The hovering MPs have been gathered with planes. It was discovered that fragments polluted urban air, whereas fibers polluted rural/suburban air. The scientists speculated the atmospheric transfer from MPs for more than 1,000 km beforehand deposition using mass balance trajectory analyses. Synthetic textile fibers were identified as a significant source of MPs in outdoor fallout. The examination of airborne fallout in Dongguan, China, revealed that the five prevalent types of city-waste-based wind-carried MPs are PE, PP, and PS. MP levels are said to be 20 times greater in the money’s outdoor air than in any far farms location, meaning that local variables such as humans and transit have an effects (Miller et al., 2021). Regardless of the small number of studies, tracing any potential sources and types of MPs in the natural environment is critical for comprehension of their migration mechanisms; this is due to the fact that the types, shapes, and sources of airborne MPs vary across the globe, due to regional environmental variables (Allen et al., 2019). The erosion caused

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by wind spreads released into the air MPs in natural settings, posing a risk to individuals from dust inhalation. A noteworthy route in exposure to aerial MP is inhalation, and sand is a significant short for human inhalation. Aerial MPs tend to cause a variety of diseases in the circulatory and respiratory systems, as well as malignancy. Inhalable material (small micro and tiny fibers) dispersed in the air could potentially emit chemicals that are absorbed by the lungs. MP was found to be higher in households than in consumption of tainted mussels, Mytilus edulis. PET exposure for Chinese kids living in urban areas has been projected to be 17,300 ng/kg body weight, which is not insignificant. An interior inhalation thermal manikin test in three Danish residential apartments, however, revealed that human inhalation resulting from natural MFs (91%) exceeds that of fake (plastic) fibers (4%). The study did discover, however, that tough MPs are typically fewer than fibers made from plants, which renders them easier to inhale (Smith et al., 2018). MPs, particularly MF levels, are more prevalent indoors than in nature, based on available research. However, disparities in respiratory exposure along with parameters (e.g., vital capacity, end rate, maximal inhalation pressure) arise as a result of data inadequacy and incertitude. As a result, it is generally assumed that ingestion exposure has a higher value than breathing exposure to sunlight. Airborne MPs, in contrast, are able to be ingested through chewing in an infected setting (ambient or outdoor) while engaging in normal activities such as chatting, eating, and so on. Furthermore, no data on individual exposure to hovering plastic additives, including phthalates and other copollutants are available. Humans can be contacted by exposing to the air BPA (Bisphenol A) through breathing or inhaling particles of air/dust via an MP or non-MP sources. However, inhaling, skin contact, and ingesting airborne MPs are not the only ways of getting exposed to them. Due to the ability of airborne MPs to adhere to hair, contact with them through the scalp remains insufficient but a potential source for being exposed (Abbasi & Turner, 2021). An Iranian study found PE, PET, and PP fibers (from indoors as well as outdoors sources) in the saliva, tresses, and skin of local residents, illustrating a major source of exposure. Human hair on the scalp has a large surface area along with tortuosity, allowing it to acquire an electrical charge that assists in bringing in, trapping, and harboring the air MPs, specifically fibers generated from garment wear, smooth furniture, and so on. Although this has yet to be proven, these MPs may enter the human system through skin contact and absorption (scalp). The MF composition in the air changes seasonally in response to distinct apparel demands. To properly describe the effects of MPs upon the health of people in terms of exposure, it is necessary to first comprehend their airborne processes and sustainable practices associated with realistic exposed levels. Local to regional, inter-regional, and local sources all play a role when it comes to human interaction with outdoor airborne MPs. The location and origin of tropospheric MPs must be located in order to estimate breath exposure. Because individuals are more vulnerable to aerial MP exposure in towns and cities, it is necessary to determine how aerial MPs contribute to PM concentrations found in urban air (Kelly & Fussell, 2020). Airborne logistics MPs that consist of nylon, PE, PP, PS, and PET are inhaled by workers in the synthetic textile industry. In vitro, inhalable MFs (PE and nylon textile fibers) slowed proliferation along with inhibited cell regeneration of pulmonary airway organoids in human beings. PS is used in a variety of industries, including electronic devices, packaging, autos, chemical additives, pigments, toys, along with other areas (Abbasi & Turner, 2021).

8.5 MPs in Food and Agricultural Crops

Within 24 hr of exposure, the most recent research on PS MPs realized significant toxicological impacts, such as morphological alterations and diminished lung’s proliferation (Prata, 2018).

8.5

MPs in Food and Agricultural Crops

As contemporary farming techniques evolved, plastic goods have become prevalent to agricultural practices, including cultivating, the fertilization process, and plastic mulching. As these plastics were degraded in fields, a large amount of plastic particles went out into the environment and were even consumed by crops (Geyer et al., 2017). Polymer mulch films have the greatest amount among these types of materials and are frequently employed in freezing and dry regions in the world to maintain appropriate temperatures and improve crop yield. After being subjected to sunlight and physical stresses such as cultivating practices, they dispersed into plastic particles and walked into soils used for farming, particularly in areas via a low healing rate of mulch flicks. The ingestion of mowing films is related to the amount of plastic particles in the environment. Along with mulch films, compost is frequently employed to enhance soil fertility. The significant amount of materials found throughout the compost (1.20 g/kg) indicates that plastic particles had entered soils used for farming via a crucial path. Extreme temperatures along with microbial-activity decomposing interpret boost the breaking down of big plastics into plastic particles and enhance the quantity of MPs that were used for soils used in agriculture. The normal development rate of MPs that were in soil used for agriculture may reach 1.71–3.50 million particles/ha/ year with permanent recurred utilization of MPs developed. Plastic particles have also been found in a variety of economic biowaste derived from garbage from homes, biomass, mature composting, and unmatured fertilizer (Mendoza et al., 2018). A significant quantity of MPs persists in sewage effluent and water due to the fact that disinfection plants are insufficient at taking off small bits of plastics. A significant quantity of small particles flows out from sewage and enters crops via cultivation. Aside via crops, plastic particles were more abundant in plants soil than in buffer ground due to irrigation with wastewater. MPs in waste and waterways, in comparison with the materials used via plastic consumption in agriculture, mostly come from native laundry machine effluent along with releases associated with personal hygiene products, fake fabrics, and microbeads. Because these small plastic particles differ in substance, properties, and particularly additives, they can cause a number of potential hazards to soils used in agriculture and human life (Huang et al., 2020). The properties of MPs differed significantly between sources, alongside elastic MPs that constitute nearly all of them in soil from agriculture. Other than carbohydrates that can be degraded in the atmosphere, yarn in household waste, particularly washing machines’ wastewater, cannot be ignored. All of the widespread plastic types, including PE, PP polyester, and PVC, among others, have been discovered at varying levels in soils from agriculture at various testing sites. Plasticizing agents have been utilized in order to soften materials for plastics, mainly in the manufacture of PVC. Flame retardants are frequently found in consumer goods (e.g., kitchenware, PP protection foams). Nutrients were used in several polymer chains, such

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as PE and PP, in order to avoid the aging process in outdoor scenarios. Plastic particles originating from different places have an immediate effect on their deterioration, transport, and afterward dangers to the environment in soils used for agriculture due to their size, shape, category, and additive structure (Zhang & Liu, 2018). The properties of MPs differed significantly due to different sources of MPs, with spongy plastic particles representing the majority of them in soils used in agriculture. In addition to fiber decay in the atmosphere, the presence of fibers at human waste, specifically washing clothes wastewater, cannot be ignored. All of the typical plastic types, like PE, PP, PS, and PVC, have been noticed at varying concentrations in soils from agriculture across various testing sites. Plastic materials undergo physical, psychological, and biological transformations in their surroundings, which include separation and destruction. Chemical breakdown promoted by UV light is critical in these different kinds of changes that usually dominates the initial break down of plastic debris. As a result of exposure to UV radiation at the correct temperature alongside the use of oxygen, MPs in the soil are photo-transformed via several chemical processes such as chain split, cross-linkage, the emergence of functional groups with oxygen in them, and even extraction into CO2. During these processes, smaller-sized MPs including nano plastics can be produced. In addition, the combined impacts of UV irradiation and mechanical scratching that result from farming procedures and soil microbe interaction hasten plastic particles dispersion. Although MPs have been transformed into tiny fragments, the electrostatic charges induced by transpiration of roots in the root zone or soil livestock consumption and excretion cause MPs to clump together with soil particles, which would avoid UV radiation and other mechanically scrapes. Incomplete degradation of MPs in soil could result in a submicron garbage with unknown hazards to the environment (Allen et al., 2019). Apart from degradation, MP transport in the fluid matrix about soils from agriculture alters tiny plastic particles shipment. MPs with lesser dimensions and greater surface functional regions transport better in porous media including soils. In addition, soil characteristics like ion concentration and cations form, as well as diversity, OM, and coatings on surfaces all influence tiny particle movement in soils. Soil creatures, especially worms, facilitate the movement of MPs in soil via borrowing, swallowing, egesting and skin adhesion, resulting in plastic particles being carried from the topsoil to lower soil and then to groundwater. Though there has been little research on the influence of MPs on groundwater throughout the world, damage to the groundwater poses substantial hazards due to the immediate repercussions for the health of humans and animals. Plant root development and breakdown, in addition to earth animals, can generate macropores in soils, facilitating tiny plastic particles transport. Plowing along with harvesting are the two examples of agricultural activities that may result in MPs transport in the subsurface environment (Li et al., 2020).

8.6

MPs Associated with the Construction Industry

Fabric or clothing in places of construction, reinforcement with fibers in mortar, paint, flexible beads, and insulating material sheets are among the primary sources of plastic particles used in both the construction and architectural industry sectors. The materials and textilerelated have long had a place in the development and the building process industries.

8.6 MPs Associated with the Construction Industry

Bedding and mattress covers, flooring, curtains, and furniture are all common applications for construction. To minimize plastic particles release, different scrubbing techniques in the polyester fabric construction are used. It was found that both time and temperature influenced plastic particles release. Lowering the environmental conditions and duration of the experiment may decrease the mechanical force, leading to less MP released while using filtration devices in the washing practice could collect MPs effectively. Polyester fabrics can be washed in a variety of ways. After laundering, plastic particles can be distributed in quantities ranging from one hundred to four hundred times. The fabric’s structure (woven, knit, and nonwoven), the yarn sort (twist, evenness, coarse hair, and the number of fibers), absorbing heritage (scouring, bleaching, dying, finishing, and drying processes), and dietary fiber chemical characteristics can all influence the percentage of MP fiber generated throughout fabric washing. Brushing operations, in simple terms, are the main source of MPs that have been generated by yarn development (Choi et al., 2021). The shedding of MPs to textiles is an additional source of MPs as MPs can leave polyester textiles from either the outer layer of the fabric or the fabric’s cut edge and enter the surroundings. Prior measurements for assessing the shedding of plastic particles from fabrics demonstrated a wide range of release (between 120 and 728,289 particles per wash). Synthetic fibers (e.g., acrylic, nylon, and polyester) all shed fibers from textile flooring in a similar capacity. Meaningful amounts of fibers escape as a result of the textiles’ loose production process. The release of plastic particles can vary based on the fabric’s trends along with manufacturing processes used (Hernandez et al., 2017). Construction materials such as marquees, membranes, and awnings, double wall spacers, and pneumatic device structures are currently attracting a lot of attention. Currently in China, mulching building sites with dust-proof nets are legally required to prevent and regulate contaminants caused by fine particulate matter. The synthetic fabrics utilized for these applications should be portable, robust, rot-resistant, moisture-proof, and UV-resistant. The types with the greatest prevalence were PE (> half of all MP polymers) along with PP (41%). MPs also accumulate nearly six times more in soil planted by resistant to dust netting in a construction site compared with the non-mulched soil (Jönsson et al., 2018). Particulate matter with fine particles might harm the ecosystem through contamination of MPs. The sheer quantity of MPs has the potential to cause a chain reaction of adverse environmental impacts. The suggestions were made to policymakers to revise suitable legislation and policies with the aim to preserve the health of humans and the natural world. In the year comparison to nontextile constructions, appropriate geometric textile constructions will be regulated through the implementation of only temporary construction, limiting the total amount of reuses, while ensuring functionality in a shorter amount of time (Carney Almroth et al., 2018). Scaffold netting on building locations along with a synthetic greenery sheet is another probable source of MPs with PE being a frequently utilized plastic. Because these PE merchandise can frequently be of lower caliber and made from recycled materials, they are particularly susceptible to extinction. In addition, because of being continually exposed to UV and natural environments, they are at a high risk of rupturing and polluting the environment, making the use of these substances without adequate guidance very risky. Finally, MPs were emitted from plastic tents in rural hillside tourist areas, including the Tibetan Plateau. In addition, the dispersed and frequent mobility of herders who utilized

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fiberglass tents made prevention and regulation of MPs’ contamination impossible. As a result, the problem’s severity has gotten worse as a significant amount of the collected wastewater and solid waste was not properly treated before being discharged into the river. The vastness of the Tibetan Plateau, the long distances traveled by many of the region’s inhabitants, and generally difficult transportation have proven to be impediments to avoiding and controlling the accumulation of MPs in this region. Other than water, none of the other materials is used in bigger amounts than concrete in the construction industry. The substance version of concrete has gone through extensive development and is still being refined in the hopes of reducing practical issues and increasing capabilities. Fiber-reinforced cementitious materials made of composites, for example, have been widely used to boost the mechanical properties and durability of cementitious materials. To improve damping, tensile strength, flexural strength, toughness, and dimensional stability, various fibers such as PVA, polyunsaturated, and PAN have been investigated. PVA fibers had a homogeneous dispersion in the cementitious matrix, along with an important proportion of these cables were successfully attached to the matrices. The hydrophilic nature of the PVA cellulose and its rough surface structure might explain that it is possible to manipulate composites with the microscale improvement. As a result, a strong bond with a matrix of cement was formed, which improved the interfacial transition zone region. Despite being true that barely any quantities of polymers are needed to improve the quality of products on both the smaller and macroscales, the use of synthetic polymers will ultimately result in the release of MPs in these composites because of the nature of the polymers used in the composites (Mehmood & Peng, 2022). Interspersed concrete panels comprised of plastics provide a compact and efficient construction material that is both load-bearing and insulating. Natural or manufactured polymers (e.g., expanded PS (EPS) or PU sheet) can be used to make these walls and paper connectors. Sandwiched concrete panels have several advantages, including shorter construction times, durability under seismic forces, and cost savings. Many nations, including China, the United States of America, Japan, and Europe, are using these sandwiched concrete sheets for the purpose of developing a sustainable society. Plastic is increasingly being used in modern constructions and buildings. The substance beads are an essential component in cementitious substances that replace aggregates to reduce unchanging weight and enhance thermal/acoustic resistance. To replace tiny stones, EPS and expanded PP beads are commonly used. In 2023, recycled EPS beads were dissolved in a mixed solvent and added to plasters. Despite the fact that the items resulted in improved performance, this new approach increased MP emissions (Zhu et al., 2020). Several construction industry research projects are focusing on changing either virgin beads made of EPS or recycled EPS necklaces to reduce waste along with promote sustainability. Nevertheless, not much research on MPs has been done, which warrants future research. In addition, the EPS bead itself is well known to be a major source of combustion for residential and business buildings. As a result, much research has concentrated on the use of firefighting agents, which could also escape concurrently alongside MPs (Kujawa et al., 2021). The accidental discharge of EPS bead fracturing greatly increases the extent of injury. Hexabromocyclododecane (HBCD) was also found with substantial quantities in EPS debris taken from Asian and Pacific coasts, implying that HBCD pollution generated by EPS debris is a worldwide issue. Some people utilized methylene chloride diphenyl diisocyanate, the

8.7 MPs in Urban Environmental Management Systems

compound melamine cyanurate, along with aluminum hydroxide, among others, as firefighters in concrete constructed with EPS systems. Paintings have been prevalent in the building sectors. In their manufacturing processes, PU, PS, polyesters, polyacrylates, alkyls, and epoxies are used. A different supplier of MPs originates from building coatings, a type of paint used in construction. Plastic particles are used in watercolors to create a surface influence (such as a matte finish), enhance a color’s physical appearance, to minimize the density of the watercolors (making them simpler to apply), to make the watercolors harder and more tolerant to scratching, or to give the paint a glitter/decorative operation. Paints contribute greater amounts of MPs to the atmosphere than textiles. Washing methods, building styles (if MPs emerge from painted buildings and structures), the old age of items (such as tires), surroundings, and the outside environment are all factors that can affect the rate at which MPs become airborne. With one exception of glittering particles, these may differ in size from just a few millimeters to a few centimeters, microspheres used in watercolor formulations typically vary in size from a few to many microns (Jiang et al., 2019). The aforementioned formulations are ideal for anti-slip programs, road markings, outdoor and interior structural pigments, spas, and the heavy-duty flooring and tiles. Given that these applications are subject to significant wear, the systems may generate MPs and release them into the air around them. The fragment loss is also possible after the paint and the substrate layer have aged (mostly due to UV irradiation or after the emergence of rust on metal surfaces) or during maintenance (e.g., sanding the repainted surface). Establishing paint for decoration accounts for an estimated 4.2 million metric tons per year, with the space inside segment accounting for 73% and the exterior of a building segment accounting for 27%. UV irradiation-induced breakdown is mainly to blame for the escape of MPs that have from building paints. The conversation appears to be centered on the exterior category. The United Nations Organization to Feed Economic Cooperation and Development, better known as the OECD, estimates that 6% of paint vanishes over its lifetime: 1.8% during creating artwork, 1% due to weathering, and 3.2% when removed. For the European Union, this loss could amount to 21,100–34,900 tons per year, the vast majority of it is absorbed by soil; nevertheless, some (2,000–8,000 tons/year) is released into physiques of water. Nonfibrous MPs that have derived from polymerized petroleum resin accounted for 9% of the total. This polymer is frequently combined with other types of resin in the manufacturing process of varnish, constructing paints, rubber tires, alongside road coating (Lee et al., 2022). In general, the urban environment is a diverse and plentiful source of paint dust. In the past few decades, building cities have been common on continuing construction sites that call for deconstruction. These areas have also seen a lot of new building construction. This enables the tearing down of many painted interior and exterior segments, which causes the disintegration of a significant amount of MP parts (Galafassi et al., 2019). As a consequence, every country or region should have an arrangement in place to deal with construction and demolition materials.

8.7

MPs in Urban Environmental Management Systems

MPs are emerging contaminants that pose significant challenges to urban environmental management systems. These tiny plastic particles, typically less than 5 mm in size, originate from a variety of sources including the breakdown of larger plastic debris, synthetic textiles,

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personal care products, and industrial processes. Due to their small size and pervasive presence, MPs are now ubiquitous in urban environments, affecting water, air, and soil quality, and posing potential risks to human health and ecosystems. Centrally managed drinking water treatment plants (DWTPs) are used in every modern city. However, it was recently confirmed that MPs were driven directly to customers after being treated in DWTPs. As a result, changes in DWTP treatment methods will raise the ambiguity of their risk to water supply safety. The conventional drinking water treatment methods include coagulation, sedimentation, filtration, and disinfection processes. The first three processes contribute to 60–99% removal of MPs in source water. They are all fueled by mechanical processes that are detrimental to MPs (Hidayaturrahman & Lee, 2019). Chlorination, UV, and ozonation are common DWTP disinfectants. To chlorinate water, either chlorine gas (Cl2) or the salt sodium hypochlorite (NaClO) is added, and both processes create hypochlorous acid (HClO) and hypochlorite ion (ClO−) that disinfect viruses, bacteria, and other pathogens (microbes). UV disinfection is performed using mercury lamps that emit 254 nm irradiation. This high-energy UV light penetrates the walls of cells and membranes, destroying DNA and RNA and causing pathogenic organisms to apoptosis along with die. Ozonation causes germs to oxidize, providing even water worms inactive, in addition to the rapid degradation of organic pollutants (Xia et al., 2020). The effects of disinfection on MPs are largely dependent on the dose. In contrast, high-dose exposure results in significant surface chemical degradation of PP, high-density PE (HDPE), and polystyrene (PS). Similarly, high-dose 254 nm UV treatment induces hydroxylated modifications on MPs (Lin et al., 2020). Ozonation, due to its strong oxidative properties, leads to the decomposition of MPs. Most studies have focused on the changes in morphology and chemical structures of MPs. However, the potential formation of disinfection byproducts from MPs as a result of these disinfection methods remains unclear. In addition, the modifications of MPs in water supply networks under prolonged exposure to residual chlorine are still unknown. WWTPs handle nearly all municipal wastewater and a portion of industrial wastewater from modern cities. They employ a series of primary, secondary, and tertiary treatments. However, most WWTPs only incorporate primary and secondary treatments, which do not specifically target MPs. Despite this, the overall removal efficiency of MPs in these plants ranges from approximately 70–99% (Shen et al., 2020). Primary treatments primarily involve mechanical interception and physical precipitation methods such as bar screening, air flotation, and primary sedimentation to remove large, suspended particles from wastewater. Due to their small size, MPs are difficult to capture with bar screening. Furthermore, the low density of most MPs allows them to float on the water surface, resulting in low removal efficiency during sedimentation. Conversely, air flotation could be an effective method, though its use in WWTPs is less common compared to sedimentation. The second phase of wastewater treatment involves biological techniques (e.g., biofilm or activated sludge processes) followed by supplementary (secondary) sedimentation. Traditionally, the second treatment has little effect on MP’s loss and aging other than only sending MPs from sewage to sewage sludge. Because the raw wastewater (sewage waste) contains an overwhelming number of MPs, the effluent of WWTPs even after secondary treatment still contains extra MP residuals that are eventually released to receiving water bodies. Some WWTPs also use tertiary treatment techniques (e.g., particle separation with

8.7 MPs in Urban Environmental Management Systems

filtration or membrane, removal of nutrients (N & P)). Surprisingly, despite using membrane filtration, a tertiary WWTP still can only achieve MPs’ elimination efficiencies from 70% to 90%, with the remaining MPs being released to the wastewater (Hidayaturrahman & Lee, 2019). In contrast to the treatment of wastewater, sludge treatment processes can alter MPs significantly as different destructions arise on the MP surfaces following sludge medications, including harsh, stripping, bubbling away, and so on. Mechanical methods are used in both concentration or preparing processes to decrease the moisture level of the sludge, and these have minor impacts on MPs. Stabilization, on the other hand, can be highly damaging to MPs, which usually includes either anaerobic or aerobic digestion in order to convert the sludge into stabilized products. The sludge digestion treatment reduced the quantity and size of legislators in the sludge. Aerobic breakdown of food waste caused lactic acid MPs to deteriorate and fragment, resulting in irregular splitting and tiny daughters’ particles. In a WWTP’s effluent, MFs predominated, whereas atoms and fragments predominated in digested sludge as most MFs are biologically degraded into smaller pieces during digestion. In addition, after aerobic digestion, the amount of MPs decreased, leading to MP destruction while flakes (Li et al., 2018). The surface morphology and environmental behaviors of MPs can undergo further changes as sludge enters solid waste treatment processes. Composting, a common solid waste treatment technique, is effective in reducing or eliminating pathogens and organic pollutants in sludge (Chen et al., 2020). In WWTPs, MPs tend to accumulate in excess sludge, which is then transported to sludge treatment facilities. Some of this excess sludge is used for composting and eventually becomes agricultural fertilizer. Thus, MPs present in the sludge are transferred to the composting process, potentially altering their characteristics and even changing their abundance. Research indicates that composting significantly impacts the size distribution of MPs, converting larger particles into smaller ones (Chen et al., 2020; El Hayany et al., 2020). This breakdown of MPs may be caused by the mechanical forces during the compost turning operation and chemical oxidation (Gui et al., 2021). However, EI Hayany et al. (2020) observed that while composting affected the size distribution and micromorphology of MPs, it did not alter their overall abundance. This could be due to the lack of capacity for MPs degradation by microorganisms under the applied conditions. The extent to which conventional composting can change the abundance of MPs depends greatly on the composting temperature and the specific microbial community involved. A comprehensive global evaluation of various cases and samples is necessary to fully understand the modifications of MPs during composting. Since composting does not completely eliminate MPs, the resulting fertilizer could act as a pathway for MPs to enter the environment. It has been confirmed that the landfill holds 21–42% of the world’s plastic waste production. The environment in landfills is typically anaerobic, and abundant MPs are allowed to break down into MPs. Over time, MPs were produced, accumulated, and then released from landfills. One study found MPs leaking in landfills in Norway with various MPs in abundance, size, or polymers. Another study found MPs escaping from trash dumps in Norway with changes in MP prosperity, magnitude, and polymer makeup during an extended stay in landfill. MPs were found in higher abundance in newly constructed and medium landfills

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but decreased within older landfills. MPs were found in landfill leachate even though the landfill leachate was treated with a prior treatment followed by biotreatment and advanced treatment.

8.8

Contaminants Released from Aged MPs

The vast majority of the scholarship on garbage made of plastic centers around the classification and inventory of the different kinds of plastic encountered on beaches and in water from the sea samples. Polychlorinated biphenyls (PCBs) and dichloro-diphenyltrichloroethane (DDTs) have been detected in PP and PE pellets, according to some studies. Many studies have been focused on assessing the amounts of these pollutants and other POPs sorbed by various plastic samples, including PCBs, polycyclic aromatic hydrocarbons (PAHs), and organochlorine insecticides like DDTs and aliphatic hydrocarbons, by comparing the concentrations of these compounds in initial production pellets that are used and postconsumer plastic parts found in debris from the ocean. POPs are synthetic organic compounds that are found in both terrestrial and aquatic environments. They are among the most persistent organic compounds introduced into the environment by humans, and some of them are extremely toxic and have a variety of long-term health effects, including endocrine disruption, mutagenicity, and carcinogenicity. Furthermore, because they are chemically stable and lipophilic, POPs do not degrade easily in the environment or in organisms but accumulate in the food chain. PCBs are mixtures of up to 209 individual chlorinated compounds (known as congeners), 113 of which are known to be present in the environment. At least half of the PCBs manufactured are still in use, particularly in older electrical equipment or in storage. As a result, there is still a large reservoir of PCBs that could be released into the environment through spills or leakage from transformers and other devices. Furthermore, the migration of these chemicals from sediments known to contain high concentrations of PCBs to water provides a continuous supply of the materials to the water phase. Organo-chlorine pesticides are chemically stable and hydrophobic synthetic compounds. DDT is a pesticide and insecticide used in agriculture. This pesticide was used in the late 1940s, heavily restricted in the 1970s, and is now banned in the United States and Canada. Other chlorinated pesticides used in agriculture include hexachlorocyclohexane (BHC), chlordane, and dieldrin. PAHs are a class of chemicals formed during the incomplete combustion of coal, oil, and gas, garbage, or other organic substances such as tobacco or charbroiled meat. PAHs are typically found in mixtures of two or more of these compounds (e.g., in soot). Coal tar, crude oil, creosote, and roofing tar all contain PAHs. Pure PAHs are typically colorless, white, or pale yellow-green solids. A few PAHs are used in medicines, while others are used to make dyes, plastics, and pesticides. Many of these compounds are produced by anthropogenic activities. Based on their source, PAHs are classified into three nonexclusive categories: biogenic (PAHs formed by natural processes such as diagenesis), petrogenic (PAHs derived from petroleum), and pyrogenic (PAHs formed as a result of incomplete combustion of fuel). Many PAHs are carcinogenic and bioaccumulate in aquatic organisms. The United States Environment Protection Agency (USEPA) classifies 16 of these PAH compounds as priority pollutants due to their toxicity to humans.

8.8 Contaminants Released from Aged MPs

n-Alkanes, aliphatic hydrocarbons, have not been found to affect the biota; however, they can aid in distinguishing between biogenic (marine or terrestrial) and petrogenic sources of OM. In comparison to PAHs and organochlorine pesticides, these compounds are degraded relatively quickly by microbes. However, biodegradation is more difficult in some nalkanes, specifically those in the C28−C40 group (Rios et al., 2007). The USEPA recently looked into the potential existence of the plastics that contribute to the putting of PCBs along with additional (heterocyclic compounds) HOCs found in fragile ecosystems and aquatic life on Tern Island, a coral island in the Hawaiian Islands National Wildlife Refuge. Despite the PCB levels in Tern Island plastic particles samples were not determined, a significant contamination load in local waters was found coming from the plastic particles pathway as evidenced by the fact that concentrated HOCs could be originated from MPs, the place was used as a depositing area for marine litter, and the plastics were ingested by the island seabirds. The possibility of PCB transfers through a MP vector process on Tern Island needs to be balanced against the possibility of transfer via other means, especially food-chain transfer. The environmental significance of MPs as HOC vectors is determined by whether or not aquatic life consumes MPs, how HOCs desorb from plastic and enter their body tissues, and how this route is significant compared to other paths such as foods and water. Numerous studies have revealed that organisms in water, such as zooplankton, marine and freshwater invertebrates, corals, echinoderms, barnacles, bivalves, crustaceans, fish, seabirds, and marine mammals can consume MPs. Move of 10-mm PS small particles from microzooplankton to microzooplankton at a higher trophic level was additionally demonstrated, as encounters plastic particles transmit from oysters to crabs. The likelihood for HOCs to split from plastic particles to beings in water bodies is challenging to quantify; however, research conducted in laboratories shows that HOCs are capable of being moved from plastics to organs of various creatures. When lugworms (Arenicola marina) were exposed for a six-week period to MPs made from PS mixed with PCB-containing sediment, the amount of PCB in tissue shot up by a factor of 1.1–1.5 when compared to the sediments without MPs. Similarly, the discovery of PS in PCB-contaminated sand slightly boosted the amount of PCB in lugworms more than simply the presence of contaminated sediment alone. In contrast, adding PE to the sand reduced PCB metabolism by 80–98%, contingent upon the quantity of PE. A study was conducted using Japanese medaka (Oryzias latipes) to assess the risks of dietary exposure to PE with chemicals sorbed from the marine environment. Chemical concentrations sorbed to MPs fed to the fish were 55 ng/g total PAHs, 5.3 ng/g total PCBs, and 3.1 ng/g total (polybrominated diphenyl ethers) PBDEs. MPs made up 10% of the fish diet, and exposure lasted two months. Fish were fed three different diets: a negative control diet (no PE), a diet containing virgin plastic (preproduction, uncontaminated PE), and a diet containing marine-contaminated plastic (PE deployed in an urban bay had HOC concentrations 2.3–6 times higher than the negative control diet). The amounts of HOC in fish lipids in the aquatic plastic treatment population were 1.2–2 times greater than that in the adverse group serving as the control. The amounts of total PAHs and total PCBs in the fish lipid did not differ significantly distinct between the treatment groups, but the amount of chromium and one specific PCB (PCB 28) were significantly greater in fish subjected to the marine–plastic implementation. These investigations

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demonstrate that plastic particles may both improve and decrease PCB bioaccumulation based on the circumstances of the study. Lugworms were subjected to sand that was recently pre-sorbed with substantial quantities of the endocrine (up to 700 mg/L) and the compound (up to 120 mg/L), as well as the synthetic additives and PBDE. The compounds have been taken in from the PVC and shipped into the tissues of the lugworm. The biocide triclosan is along with the additive PBDE transferred in MPs that have transported into worm’s organs in similar biological concentration patterns. Worms displayed to low levels of the substance and nonylphenol in in MP-free sand developed greater quantities of compounds in their tissues compared to creatures exposed to greater quantities of the MP-sorbed electorate (Ziccardi et al., 2016).

8.9 Fate/Transport and Behavior of MPs in Pollution Control Systems This section focuses on the fate and transport (F/T) as well as the behavior of MPs in pollution control systems, such as those in DWTPs and WWTPs, combined or separated sewers, and facilities used for sludge treatment and landfill disposal of, as well as recycling and remediation of MPs.

8.9.1

In Water and WWTPs

In DWTPs and WWTPs, fibers are the one with the most widespread and least size fractions, along with PE and PP being the most widespread polymers. A few investigations, however, indicate the occurrence of a high rate of beads or pictures. One study demonstrated that calculating MPs pollution involves substantial variables. The primary factors influencing pollution from lawmakers are listed in the same directory of 2020 studies. The particular aspect and settings are emphasized, and there’s a quick overview of the inferences. Among both of these are the hydrological or structural features of the basin, the climate and climate-related things, as well as social and economic variables. The large number of MPs, in particularly, has a direct connection to the GDP, as well as its size and numbers of business sectors in the country of interest. In this regard, a connection between MP quantity and the sector type (primary, secondarily, tertiary) should be noted. These parameters are strictly followed by the density of population and land use. The line between suburban and rural regions, however, is not clear-cut. Their relative impact on MPs is also dependent on the environment in terms of pollutants and catchment traits, form, and flow rule (Mintenig et al., 2019). Although cities sometimes experience higher levels of air pollution rather than surrounding regions, the variation is not always noteworthy or confirmed. The hydraulic features that define the water body and human-caused environmental changes have also been highlighted. When juxtaposed with inner and outer bends, river mouths seem to be an ordinary concentration location for MPs, whereas directly tracts seem to ease MP movement along the river (Shen et al., 2020). Atmosphere depositing also needs to be considered as different MPs are potentially essential in these depositions. However, this effect was deemed tiny, and the low values collected were blamed on factors such as collecting height along with other present and atmospheric

8.9 Fate/Transport and Behavior of MPs in Pollution Control Systems

variables. In terms of weather-related things, an upsurge in pollutants caused by the rain could be explained as city drainage’s contribution to obtaining MPs that might otherwise be laid down on the outside of the city; intensive storm events may readily clean surfaces in cities by transporting MPs into the first flush followed by the dilution of MPs in the receiving water bodies. The summer months are expected to contain higher concentrations of MPs than the other seasons. The verification and critical proof are required for all of these claims. In WWTPs, the most frequently encountered pollutants are solids, organisms, vitamins, and pathogens (Zhang et al., 2020). In consequence, treatment facilities in WWTPs aren’t purpose-built to remove MPs. MPs enter WWTPs from several sources, involving separated or combined sewers, domestic or business wastewater, and leachate from dumps/landfills. MPs in waste disposal leachate are connected to the decomposition processes endured by plastic items in the distinct surroundings of the landfill. Water from urban runoff additionally flows to the WWTPs links MPs with the fragility of larger pieces of plastic found on city ground, tire fragments caused by the friction with the road’s surface, and atmospheric depositions. Contaminations in the rainwater retention reservoirs have been deemed to be associated with tourist attractions, with those located near business and industrial zones being contaminated more as compared with those located near road networks and residential neighborhoods.

8.9.2

In Combined Stormwater and Sewer Overflows

The process of the transfer of particles, sprays, and pollutants from above to the surface of the planet is known as atmospheric deposition. It is recognized as an important driver of chemicals, particularly MPs, in urban water from precipitations. MPs may take part in small air-ground exchanges or travel long distances via air transport. Wet, dry, or bulk deposition from the atmosphere is reported, with the latter combining the first two. Raindrops and snowflakes scavenge suspended particles, compounds, and aerosols as they fall, resulting in wet air deposition. Snowflakes are more in effect scavengers than raindrops owing to their bigger particular area of surface. Drying precipitation in the atmosphere, referred to as atmospheric fallout, is a deposit triggered by the obtaining of particles, compounds, and aerosols inside of an airborne collector. Finally, in bulk deposition, hydrated and dry atmospheric emissions have mixed (Khatmullina & Chubarenko, 2019). Due to the large number of MP contributors and ambiguities within the movement of drydeposited MPs with water from storms, measuring the part of pollutants’ shipping from the atmosphere to stormwater runoff is difficult. Monitoring wet deposition is easy; however, observing dry deposition and distinguishing vehicle-related deposition nearby pavements via ambient urban deposition in the atmosphere is difficult, making comparing data between studies difficult. A further hurdle is that figures of atmospheric deposits are published in particles/m2-day, whereas figures of particulates in suspension in the air are collected using active samplers and reported at particulates per milliliter of air. According to a recent analysis using atmospheric accumulation sampling, while the presence of MPs has been created in urban area airsheds. The speed about deposit (particles/m2-day), tangible particle features such as dimension and form (shape), air obtaining velocity, color, and chemistry have all been investigated (Shamskhany et al., 2021).

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Contemporary stormwater administration has made a concerted effort to mitigate the detrimental impacts of increasing urbanization by building green drainage systems in order to help rebuild the pristine hydrology in city basins and avoid drainage and contaminants export. The insensitive and green regions of urban areas respond in different ways to rainfall instances: in the impermeable basins, the release of runoff leads to the participation and export of contaminants (including MPs) with water from storms, whereas in the permeable basins, regardless of whether storms are frequent, there is little or no runoff, leading to the confinement of pollution and MPs by vegetation, soils, along with sediments. As a result of these differences, some authors suspect that the effects of green/pervious urban areas to MP export have been so minor that they may be ignored for exporting MPs. The makeup of the MP fragments, the water drainage system of the area in question, along with the local environment each impact stormwater-mediated MP export from a catchment. The underlying processes are summarized below. Total particle volume (TPV) is essential in deep water due to the fact that it determines how long the particulate spends in the fluid column or its susceptibility to processes like contaminants and de-fouling, among others. It is also crucial for the design of stormwater ponds and the settling of stormwater sediment. The particle’s TPV was discovered to be an effect of its dimensions (or diameter in the context of oval particles), shape influence (drag on the particulate), and its mass density relative to the ambient fluids. Despite the fact that much of the prior study on TPVs focused on spheres of different elements or particulates of sediment settling in water, the widely used TPV equation is straightforward to apply to MP settling. Further consideration, as previously defined, may be required to account for spatial fluctuations in MP assets such as dimension, form, and density as well (Smyth et al., 2021). Weathering, encrustation with tiny clay particles, and coating with biofilms are all known processes that affect the content, shape, and dimensions of MPs. Polymer form influences an MP weight and shape to a lesser extent. MPs’ TPVs (and thus the buoyancy of them in the encompassing fluid) may vary substantially; MPs can be buoyant in either a positive, neutral, or negative direction. The MP mass density is not frequently included in stormwater study reports, but the polymer types detected are. Based on the sedimentation theory, the shape of MPs influences MPs move in water by impacting the drag force performing on the microscopic particles. The law of Stokes applies to bodies that are spherical but is also applicable to irregular in shape objects. Data on MP atom shapes was given, implying the fact that plastic fibers could be mobilized with greater efficiency than MP fragments. In addition to atom settling, MP features influence particle engagement by rainfall moves that have adequate transport acts in rainy conditions. MP particles remain trapped in the catchment where such flows are not achievable, such as in permeable green areas. To detect earlier MP motion, a Shields graph could be used. The result was tentatively demonstrated in experiments on MP loss in an indoor cyclical flume, on the water’s floor, and in a lab flume sleeping of MPs along with sandy beaches. The highest TPVs were found in larger, heavier MP particles, which were less likely to be diminished by ambient flows. Researchers confirmed the preferential migration of smaller bits of MP in the city environment by studying the concentrations among various MP dimension fractions in urban water from storms during wet climates and discovering that smaller MP were more common than the bigger ones (Lange et al., 2022).

8.9 Fate/Transport and Behavior of MPs in Pollution Control Systems

More studies on how to dispose of MPs and nanoplastic parts in the soil is desperately needed, particularly to support modern urban drainage design techniques for blue drainage infrastructure. Such strategies provide numerous opportunities for MPs to be transported onto green spaces through processes such as precipitation into the atmosphere, wind shipping, and hydrophilic transport using runoff from surfaces discharged from impervious sectors (Ballent et al., 2016; Kole et al., 2017). Rainfall can transport MPs into soils and particles, where they can be preserved. The movement onto deeper layers of soil may occur in warmer climates via soil holes, micro- and macro-pores created through wet–dry moves and plant roots, as well as pores formed by cycles of freezing and thawing. As showed in bioretention studies, filtering MP-laden rainwater runoff through dirt particles and plant–root mass may successfully eliminate MPs from rainwater (Yin et al., 2021).

8.9.3

In Sewage Sludge and Landfill Leachate

Water is regarded as the primary mode of MP transport in the environment. MPs are removed at a high rate during wastewater treatment from domestic and industrial wastewaters, storm water, and landfill leachate. This is primarily due to MPs’ high hydrophobicity, which facilitates their adsorption onto organic sewage sludge surfaces. MPs removed from wastewater are transferred to sludge and accumulate there using this core mechanism. According to studies, sewage sludge retains more than 90% of MPs. WWTPs perform a vital part in the accidental release of MPs into the surroundings, with each plant emitting between 106 and 1,014 MPs/year, depending on country or region, with concentrations ranging from 510 to 495,000 particle/kg dry mass (dw) of sludge (Zhang et al., 2020). The yearly total of MPs getting into the earth’s surface with sludge land utilization is much greater than the total quantity of MPs getting into the seas and freshwater sand from various sources. An array of variables, such as gentrification diversity, the amount of population, usage of plastics, volatility, and therapeutic processes within the studied WWTP, as well as contradictions in the collection and evaluation methods, can explain the substantial variation in results. As such, it is critical to evaluate the yearly MP concentrations found in sludge and wastewater while accounting for seasonal variations, and to correlate the results with the WWTP processes. It can be challenging to identify systematically the polymer form, shape, and shade of MPs in sludge from different investigations due to obstacles in exact quantification. The first limitation is that most studies only examine a selected group of MPs in examples, raising questions about impartiality. A further limitation is the variation in size fluctuates among studies, which hinders comparable results (Nizzetto et al., 2016). Keeping these constraints in mind, this review examined 26 studies that noted on the material type, influence, and color about MPs in sludge from toilets and found that the MP composition of waste reflects our daily plastic use and is primarily composed of PE, PP, polyethylene (PA), polyester (PES), PET, and PS (Figure 8.4). PE is used in personal care items such as wash bottles, pipes, etc.; PP is used in food the packaging, snack wrappers of auto parts, etc.; PA is used in manufactured clothes, etc.; PES is used in fake clothes, etc.; PET, which is used in manufactured clothes and to make water and different drinks bottles, for instance; and PS is used in foam packaging for food, sunglasses, and for construction insulating properties. The average number of plastic types in a specimen in any one study, on the other hand,

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reflects the original source of wastewater. The presence of various types of MFs (rayon and PET), as well as the levels of PP/PE, acrylonitrile–butadiene sty (ABS), and the chemical acrylic material elastomer (Vamac), for example, suggested that personal use and vehicle services were the serious sources of MPs in sludge (Li et al., 2018). A large number of investigations (23 out of 26) grouped MPs as soluble fiber, divide, film, globe, micro beads, flake, Pellets, foam, shine, line, shaft, also referred ellipse, tubular, and the sheet. Fibers are one of the most frequently cited MPs due to their high manufacture, and they typically begin from cleansing artificial clothing and clothing performing activities. The second-ranked parts are mostly secondary MPs, and they’re the result of factory manufacturing and diminished everyday products. The degrading of plastic containers and materials for packaging (such as wrappers) could be the cause for these third-ranked films. The others are much less common. Research suggests that the lifestyles of people in the nation or geography may play a significant role in deciding how MPs shape. Fibers rule in sludge in the Islamic Republic, for example, due to high production of textiles such as flooring and curtains. A further instance is that beads are filled in dewatered wastewater but not in mud, indicating that society consumes regular grooming products. According to the majority of studies, the amount of MPs maintained in sludge is usually larger compared to the number of MPs preserved in the wastewater. This is because larger MPs have an opportunity to sink down to the bottom of the tank, but smaller MPs continue their journey along the WWTP. According to one study, 54% of the MPs in sludge was in 100 and 500 m, 24% were between 10 and 100 m, 12% were between 500 and 1,000 m, and the remaining percentages were between 1 and 5 mm. When contrasted with liquid waste samples, MPs grouped commonly as follows: > 1 mm (9.04%), 1–2 mm (9.04%), 250 μm to 1 mm (12.65%), 125–250 μm (39.76%), 38–125 μm (21.08%), and 1.5–38 μm (9.68%). Additional research, however, has discovered a greater number of smaller MPs in sludge than larger MPs. Because of adsorption on biosolides, smaller MPs are believed to be removed more quickly in biological treatment processes. Many factors have an impact on MP features (e.g., size, shape, color, and type) in waste to an extent, such as the area’s growth level, garbage disposal actions, citizens’ daily habits, number of people, the processing units in the particular WWTP, and the techniques used for analysis; however, the physical features of sludge-based MPs vary without much association with the entire nation or location (Gong & Xie, 2020). Waste disposal facilities are an important retailer of plastic waste, accounting for 21–42% of all plastics produced globally. In landfill, plastic materials are broken down into secondary MPs via complex chemical reactions and physical modifications. Furthermore, landfills receive the main source of MPs in a variety of forms (for example, discarded sludge) with 20,000–91,000 MP items/ kg in landfill refuse, a figure that is much higher than amounts of MPs in sediments, sewage effluent, and soil from agriculture. Although leachate can remove some MPs from refuse, the level of MPs in refuse is significantly greater than that in the leachate (Su et al., 2019). Furthermore, MPs were discovered in water bodies, particles and aquatic organisms (e.g., mussels) near garbage dumps, implying that trash dumps are a contributor of MPs in their surrounding environment. WWTPs are the primary contributors to the contamination of MPs because wastewater contains an extensive mixture of polymers derived from personal care products, facial cleansers, and textiles. These materials are poorly transformed in WWTPs. The removal of MPs is determined by the efficiency of different treatment units

8.9 Fate/Transport and Behavior of MPs in Pollution Control Systems

in WWTPs, which varies significantly depending on the physicochemical and biological processes used. Preliminary treatment techniques such as screening and skimming were found to remove 35–58% of MPs in settled solids. Primary and secondary treatment have been shown to remove up to 97.8% of MPs, with efficiency increasing to >99% when combined with secondary and tertiary processes. This removal efficiency represents the retention efficiency of MPs; thus, the retained MPs remain in the sludge/biosolids generated and, depending on sludge/biosolids handling, may eventually reach the environment (Puthcharoen & Leungprasert, 2019).The concentrations of MPs in sludge vary by location, possibly due to differences in population density and waste management practices. In Finland, for example, 301.4 items/kg of sludge were reported, whereas in China 271,700 items/kg were reported. The concentration of MPs in primary sludge was found to be higher than in secondary sludge, indicating that MPs were removed more effectively during primary sedimentation. The higher concentration of MPs in the influent wastewater compared to the primary effluent was attributed to this. Greater population density leads to higher consumption of personal care products, more laundry wastewater, and a higher flow of wastewater to WWTPs when compared to sparsely populated countries, resulting in higher concentrations of associated MPs in wastewater sludge. Variable regulations regarding the use of microbeads in personal care products may also influence the abundance of MPs in wastewater and sludge. MPs pollution in food and food waste can result from the widespread use of plastics in food production, processing, and packaging. MPs enter the human food chain through seafood and terrestrial foods, and then to food waste via wasted food. According to research, there can be up to 15 MPs per fish, 3.7 MPs per mussel, and 7 MPs per oyster. Fresh fruits contain more MPs than vegetables. MPs can also move up the food chain via trophic transfer and end up in food/food waste. MPs were found in approximately 300,000 pieces/kg of food waste collected from grocery stores. MPs are separated from food waste using the saturated NaCl density separation technique (Youcai & Ziyang, 2017). A microscope (Nikon Eclipse LV100ND) and a micro-Fourier Transform Infrared Spectroscopy system (PerkinElmer, USA) were used to characterize separated MPs on cellulose nitrate grid membrane filters (Whatman, 47 mm 0.45 mm). Because there has been little research on the occurrence of MPs and their fate in food waste, more research on food waste as a potential contributor to MPs pollution is required. The shape and size of MPs are important because these morphological characteristics influence their fate and degradation. Diversely shaped MPs, such as fragments, granules, fibers, films, and rods, were more common in refuse samples than in leachate samples, which were much less diverse morphologically. In refuse samples, fragments predominated (59.8%), whereas fibers (38.5%) and granules (35.8%) predominated in leachate. Granular MPs from personal care products accounted for 18.6% of MPs in refuse; fibers from synthetic clothing accounted for 13.4%; and films from household plastic packaging accounted for 7.9%. Synthetic fibers were found to be the most prevalent type of sludge MPs, followed by fragments. Due to detachment from textiles during washing, fibers end up in WWTPs. Microbeads, which are frequently found in fragmented forms in personal care products, rinse-off cosmetics, toiletries, and hand cleaners, end up in WWTP sludge. Fibers are the most common type of MP found in various food sources, such as fish. The average size of refuse MPs was 1.03 mm, which was larger than the average size of leachate MPs

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(0.83 mm). Smaller particles may easily move to leachate, whereas larger MPs may be retained in refuse due to the filtration effect of refuse. MPs in landfills can also degrade over time. MPs found in young, medium, and old landfill refuse, for example, were 83,000, 68,000, and 36,000 items/kg, with average sizes of 1.23, 0.91, and 0.71 mm, respectively. MPs in sludge and various food products ranged in size from 0.02 to 5 mm. The size distribution of sludge MPs differs by country, as does the size distribution of food MPs (Li et al., 2016).

8.9.4

In Systems for Recycling and Remediation of MPs

Microorganisms play an important role in the alteration of MPs interred in the earth’s crust, and environmental conditions such as temperature, sunlight, and humidity have a significant impact on this transformation. MP decomposition is currently studied in bugs such as the bacteria Bacillus sp., The bacterium P sp., P. aeruginosa, Aspergillus clavatus, Fusarium, Penicillium vulgar Phanerochaete, and Acremonium, which use MPs as their sole source of food from dirt, garbage dumps particles that look and fertilizer. The microorganisms join to the outermost layer of plastics and form biofilms to begin biodegradation. Regardless of the fact that the hydrophobic makeup of MPs inhibits microbe settlement and development of biofilm, microbial enzymes can increase the hydrophilicity of the plastic surface, promoting microorganism adhesion. The bacteria then act on the plastics by releasing extracellular chemicals that promote the oxidation process and the process of hydrolysis. The decomposition is usually a surface-erosion process with a few days to several weeks for microbial adaptation, followed by extracellular enzymes released by the microbes working on the surface of the plastics to reduce polymer weights while also causing physical, chemical, alterations to the arrangement of polymers (Paço et al., 2017). High-density PE (HDPE) MPs are hydrolyzed by enzymes such as laccases, manganese peroxides, or lignin peroxidases, whereas hydrolases such as esterases, lipases, and cutinases have the ability to induce PET degradation. However, using enzymes for catalysis during biodegradation is a time-consuming and costly process because microbe cells contain a diverse set of enzymes that may interfere with the desired reaction (Zhang et al., 2020) (Figure 8.5). Cutting ─C─C connections appears to speed up the breakdown of plastic in hyperthermal environments. By introducing the ─OH group and C=O groups, UV pretreatment of MPs may help minimize hydrophobic characteristics, thereby expanding MP connection with microbes. Thermal and physical oxidations would also aid in biological breakdown, as would ultimately the existence of metal ions in MPs, and these generate radicals that are free on the outer layer of the polymer, react alongside oxygen (O2) to form carbonyl bonds, and eventually reduce MP hydrophobicity. After decline, FTIR (Fourier Transform Infrared Spectroscopy) can be used to detect functional groups on the outermost layer of MPs, whereas scanning electron microscopy (SEM) may be used to evaluate changes to the surface such as cracks, holes, and soil erosion. The technique of adsorption is currently being investigated for wastewater treatment, but MPs-specific adsorbents are scarce. At pH 6–8, a strong compressible sponge composed of chitin and graphene oxide was effectively adsorbed onto multiple kinds of MPs. High capacities for adsorption were observed even after three sorption cycles (PS 89.8%;

8.9 Fate/Transport and Behavior of MPs in Pollution Control Systems

Figure 8.5

Various Techniques Used for the Mitigation of MPs

carboxylate-modified PS 72.4%; amine-modified PP 88.9%). Because OH might conflict with the positively charged polyester at the exchange sites, the efficiency was low (43.7%) at pH 10. Electrostatic interactions between chitin amino groups and groups of carbohydrates in polyester carboxylate-modified, as well as interactions between graphene oxide carboxyl groups and amine-modified PS, are responsible (Rummel et al., 2017). H-bonding would occur among the functional groups that contain oxygen onto the adsorbent molecules and amino/carboxyl communities of the polymers in general, in alongside the interactions between the oxides of graphene and aromatic rings of the polymer chains in the MPs. Because chitin, a form of polysaccharide with a bond made up of glycosidic molecules, becomes completely environmentally friendly in soil via an enzyme and chitinase, sponge might additionally be biodegraded by soil microorganisms as well. Graphene oxide, on the other hand, is an excellent adsorption material due to its substantial amount of oxygen atomic particles on its outermost layer (epoxy and hydroxyl) in alongside the carboxyl groups (Shabbir et al., 2020). Adsorption of pollutants using biochar to serve as an adsorption material derived from many different sources has gotten a lot of consideration. MPs adsorbed or immobilized by biochar for different purposes was studied. The material known as biochar was created by pyrolyzing the barks of Pinus sylvestrus as well as Picea spp. for 3 hr at 475 C. Biochar was steam activated under various conditions, including both small and large (1.1 and 5 L/min) nitrogen dioxide flows, as well as various water circulation rates. By employing spherical PE’s formation small beads (10 μm), cylinder-shaped, eliminate PE pieces (2–3 mm), and a fleece fiber, attachment of PE materials MPs of various sizes (10 μm, 2–3 mm), shapes, and fleece material were tested. In accordance with the particle size, MPs have been immobilized or maintained in the spaces between biochar particles, along with mobilized biochar demonstrated a massive potential for MP rehabilitation. The bigger fragments were wholeheartedly preserved (a complete ensemble retention has been

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observed for PE’s formation MPs, whereas almost 100% accumulation was reported for fleece fibers), whereas MPs in the μm size (10-μm spherical microbead) did not show efficient adsorption because the larger meso- and macro-pore subject matter were advantageous in the exclusion of the smallest MPs. Adhesion polyoxometalate ionization liquid (PIL) onto superparamagnetic and microporous core-shell particles of Fe2O3/SiO2 resulted in the formation of a magnetic nanoparticle composite. The previously viscous coating of PIL on superparamagnetic fine particles aided in the binding of MPs and other harmful substances from waterways (microbial, organic, or inorganic). Poly necklaces (size = 1 μm; concentration = 1 g/L) were removed completely with a substance called adsorbent at a rate of 10 g/L and rallied with a magnet that is permanent. Although the incorporation of green technologies alongside attracting adsorbents was persuasive, more research is required to understand the problems posed by the MP absorbing route. In organic material degradation, the sophisticated oxidation of contaminants using a highly effective catalyst functioning by radical providing species has attracted a lot of attention. Nano-springs made of magnetic nitrogen-doped carbon fiber were developed for hydrothermal processes of the sulfate oxidation process of cosmetic MPs. To begin, manganese was overloaded to carbide nanoparticles that were encapsulated in helically N-doped nanotubes made from carbon and were subsequently enriched with unsymmetrical peroxymonosulfate (POMS) via one-pot pyrolysis. After 8 hr pyrolysis and at hydrothermal temperatures of 800 and 160 C, MPs lost about 54% of their weight. The hydrothermal condition provided both high pressure and physical ripping of the polymer, thereby initiating its degradation. In the drugs given MPs, FTIR, and SEM approval revealed practical chains with ketonic or hydroxy organizations, as well as a wealth of cavities. Introducing N into that POMS, which are (HO-SO4) capable of offering reactive oxygen compounds that include SO4• and a compound called with E0 = 3.1 and 2.7 V vs. the standard hydrogen electrode for sophisticated oxidation to proceed, the honeycomblike arrangement of sp2 carbon dioxide created more active sites and enabled POMS activation. Furthermore, manganese is permitted, and other transitioning metals including manganese have been identified to be POMS, which are activators for the generation of SO4•, which was successfully converted into elements MPs with no harmful effects on microorganisms in water. When a semiconductor photographic catalyst draws in photons of an appropriate length (visible/UV), electrons (e) in the band known as the valence band get excited and migrate to the conduction band, which results in leaving positively charged holes (h+) behind. Free radicals such as superoxide radicals (O2•) and hydroxyl radicals (•OH) are formed when e and h+ react with adsorbed water and oxygen. These substances then react with polymers made of OM, causing polymer chains to fracture and occasionally complete the formation of minerals. For photocatalytic treatment of wastewater, materials such as Titanium dioxide (TiO2), Zinc oxide (ZnO), Zinc sulfide (ZnS), Tungsten trioxide (WO3), Zirconium dioxide (ZrO2), and Graphitic carbon nitride (g-C3N4) are currently applied. TiO2 has received the most attention due to its ease of availability, lack of toxicity, and low cost. The general mechanism of photocatalytic degradation for organic pollutant removal is depicted in Figure 8.6 (Sheng et al., 2018). The approach known as sol–gel serves as an appealing chemical-based attitudes technique to MPs. The use of innovative inorganic–organic combination of silica gels and

8.9 Fate/Transport and Behavior of MPs in Pollution Control Systems

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Figure 8.6 General Mechanism of Photocatalytic Degradation of Organic Pollutants Using Photocatalysts Under the Suitable Light Source

the idea of a host–guest relationship were proposed for the treatment of MPs. The incorporation of a capture group, a bioinspired component of the entire molecule, was built first, followed by its creation of a draw in unit capable of interacting with the compound to be contained via the functional groups that are present. Each of these elements eventually combines to form a component known as the chemical. The inclusion or lack of alkoxy silyl

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supported in the formation of the desired 3-D network, along with structured silica gels were created using a structured system of networks via the sol–gel procedure. Following that, the interaction within the collection unit and the inclusiveness of the substance’s bioinspiration happened, allowing for the addition of inert molecules, while keeps the collected hydrophobic, which in nature obstacles were easily detached using an extraction technique such as a sand trap (Zhou et al., 2018). The gel form of silicone dioxide was found to be significantly more successful as opposed to activated carbon for MP separation. High or low levels of pH, in particular, are likely to promote faster condensation due to quicker hydration and moisture rates. At neutral pH, alkoxysilanes, such as the ingredient, react carefully, and n-alkyl-substituted chlorosilanes give birth to sialons, which quickly release hydrochloric acid due to their high water activity. Monochlorosilanes are therefore likely to evolve into monomers, and Di chlorosilanes shape long-chain oligomers in; however, in the case of n-alkyltrichlorosilanes, three reactants may be helpful in the formation of 3-D connections, which are suitable for relating to wastewater from factories due to the pH-induced the interaction that takes place. Functionalized molecules precursors were used underneath an inert nitrogen milieu to form bio-inspired alkoxy-silyl hybrid organisms with hybrid molecules functioning as linkage substances between the MPs. As a result, MP aggregates using the method of sol–gels produces 3D agglomerates that can be eliminated with an air filtration technique. A separate study investigated pH-induced accumulation followed by a two-step removal of both PP and PE MPs (250–350 μm) due to physical and chemical treatment technique of water and found that MPs particle size may increase independent of pH due to the water-based environment by adding trichlorosilane-substituted Si derivatives of oil. To remove the formed Si-based MPs aggregates (size 2–3 cm), purification (sand traps) can be implemented. Because they are capable of influencing the hydrolysis as well as the condensation kinetics in water and, thus, their binding capacity to MPs, different alkyl groups have an important effect on the aptness of alkyltrichlorosilanes in the clumping the process (Ariza-Tarazona et al., 2019). Coagulation promotes the separation by forming enlarged particulates and allowing the coagulant substances to bind small fragments via interaction in the ligand substitution process (Al-Oweini & El-Rassy, 2009). The tiny spheres and the amount of MFs experienced degradation using an alum (5–10 mg-Al/L) in the coagulation process, with the microspheres being reduced from 16 NTU (Nephelometric Turbidity Units) at the beginning to 1.0 NTU after coagulation. During coagulation, alum generated H2SO4 along with cationic charge Al-containing different species, which affect the pH level and zeta potential. Sweep flocculation has been suggested as the governing mechanism for removing the microspheres. However, it was found that the presence of 20 mg/L surfactants in the solution had minimal impact on the coagulation accomplishment of the microspheres. Surfactants also had an important effect on the stability of MFs originated from PE, but the fibers have been eliminated successfully through the coagulation process (Herbort et al., 2018). The conventional filtration method is challenging and difficult to use to remove MPs due to the enormous quantities of water with low solid quantities and exceptionally tiny size of particles. Ultrafiltration (UF) requires a smaller amount of energy, has a high the separation efficiency, and, most significantly, a small plant size. Coagulation and UF have been an

8.9 Fate/Transport and Behavior of MPs in Pollution Control Systems

excellent choice due to the excellent quality of the effluent of the discharge produced by the combination. The amount of fouling caused by MPs and nano plastics, respectively is associated with MPs’ sizes between 13 and 690 nm on an industry-standard UF poly(sulfone) membrane. More than 25% of the MPs had been absorbed onto the outer layer of the membrane after 48 hr, and interactions with hydrophobic agents, as well as surface repellent forces that could have reduced the rate of absorption. When utilized alongside the coagulation process, UF serves as one of the kindergarten treatment techniques currently used in treatment facilities (Zhou et al., 2012). The precipitation of MPs by Fe- and/or Al-based coagulants has been extensively studied to remove PE MPs of varying sizes. Coagulation with Al- and Fe-based salts may eliminate MPs that are expected to float. In all tests, sodium chloride based alum outperformed Febased salts. The smaller the PP particle size, the greater the removal effectiveness; MPs of 0.5 mm demonstrated maximum removal efficiency (40%) at an important amount of alkaline chloride (270–405 mg/L). Furthermore, even when employing a high Al-based salt dosage of 15 mM (below 40%), pH 6 was shown to have the best effectiveness in removing MPs. Furthermore, turbidity and ion concentration had very little impact on the effectiveness of MP elimination. Additionally, removal efficiencies alongside FeCl3 were quite low (15%) across the entire spectrum. In the end, the benefits of coagulation include the ability to easily disregard small MPs and to manage situations for operation and less complicated mechanical components. Nevertheless, coagulation has the negative effects of adding chemicals externally, and excessive application of Al-based coagulation could raise Al-salt residue in water for consumption, which may be harmful to living creatures (Zhang et al., 2020). Electrocoagulation, a combination of coagulation floating and electrochemical process, has long been utilized to treat different contaminants in water, such as dyes, toxic metals, dairy processing effluents, phosphate, calcium Cr (VI), and herbicides. The electrostatic reactions on the electrolyte surface, the creation of mixing agents in the substrate followed by the binding of colloidal/soluble materials through the coagulant, and particulate separation from the dissolution caused by the cathode’s expansion of bubbles made up of hydrogen are the three major occurrences in electric coagulation (Perren et al., 2018). Although electrocoagulation has been employed for decades in water treatment, little is known of their function for MPs removal. In one study on removal of microbeads of PE’s formation in artificial wastewater in a 1-L stirred-tank batch reactor for 60 min, initial pH (pH 3, 5, 7.5, and 10), conductivity, and current density were found influencing the results. At pH 7.5, 99% removal was seen, suggesting that the coagulating agent forms more easily in neutral pH (Perren et al., 2018). Varying the amount of sodium chloride (NaCl) (2–8 g/L, equivalent to 7.44–13.75 mS/cm) in the sample demonstrated that enhancing the concentration of Cl ions had no effect on efficacy of removing MPs, contrary to the reports claiming the reliance of dye-removal efficacy on Cl ions. In addition, current density had no effect on electrocoagulation cell removal efficacy. However, using an electrical density of 11 A/m2 increased the energy utilization of the semiconductor cell. As a result of the increased water conductivity, the heating element required fewer resources to operate, making the process of operation simpler given that the coagulant was produced by the metal electrodes (Lares et al., 2018).

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8.10

Conclusion

MPs, tiny plastic particles less than five millimeters in size, pose a growing environmental threat affecting ecosystems and human health. These fragments originate from a variety of products, including cosmetics, synthetic garments, and the breakdown of larger plastic items. Primary pathways into the environment include wastewater treatment facilities, urban and industrial discharges, and agricultural practices, such as the use of plasticcontaining sludge as fertilizer. The global distribution of MPs is highly uneven, ranging from remote areas far from human activities to densely populated urban waterways. Marine environments are particularly notable for MPs, which are carried to different parts of the world by ocean currents, even reaching the polar ice caps and deep-sea floors. Freshwater systems also commonly exhibit MP contamination, with rivers and lakes serving as collection points for urban MP pollution. The F/T of MPs are influenced by various environmental factors such as water currents, wind, and microbial activity. These factors not only affect the geographical distribution of MPs but also their accumulation in ecosystems. For instance, lighter MPs may drift to distant oceanic or lacustrine regions, whereas heavier particles may settle in riverbeds or lakebeds. The behavior of MPs in the environment is also closely linked to their chemical composition and physical properties. Different types of plastics, such as PE and PP, degrade at different rates and through various mechanisms, influencing their environmental fate. Moreover, MPs can carry toxic chemicals, including HMs and persistent organic pollutants, which may be transferred through the food chain, impacting more species, including humans. In summary, the issue of MPs presents multifaceted complexity involving both their physical and chemical characteristics as well as global environmental dynamics. Understanding the sources, distribution, fate, and transport mechanisms of MPs is crucial for developing effective management strategies and mitigating their impact on the environment and public health. Future research needs to delve deeper into the environmental behaviors of MPs and develop more effective detection and remediation technologies to address this escalating environmental challenge.

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9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments Mahima John Horta, Yerramilli Sai Rama Krishna, N. Seetha, and Pritha Chatterjee Department of Civil Engineering, Indian Institute of Technology Hyderabad, Sangareddy, Telangana, India

9.1

Introduction

Microplastics are plastic particles having the longest dimension of less than 5 mm (Cole et al., 2011; Hale et al., 2020). Microplastics in the environment can be classified into primary and secondary microplastics based on their source of origin (Malankowska et al., 2021). Primary microplastics are the ones that are produced deliberately; e.g., microbeads in cosmetic products, and microplastic pellets in the textile industry (Gan et al., 2023; Laskar & Kumar, 2019; Wang et al., 2019). Secondary microplastics are formed due to the fragmentation of larger plastics such as textile fibers, fishing nets, plastic bottles, and tires (El Hadri et al., 2020; Huber et al., 2022). Microplastics get discharged into the environment through point and diffuse sources (Siegfried et al., 2017; Whitehead et al., 2021). The various point sources are industrial wastewater treatment plants, sewers, and landfills. The diffuse sources of microplastics include urban runoff, and agricultural and marine activities. Microplastics have been detected in various environmental compartments including marine ecosystems (Akdogan & Guven, 2019; Cole et al., 2011), freshwater bodies (Horton et al., 2017a; Kallenbach et al., 2022), estuaries (Defontaine & Jalón-Rojas, 2023; Wang et al., 2022; Xu et al., 2020), and soil ecosystem (Guo et al., 2020; Yang et al., 2021). The effluent from marine industries and shipping activities are major sources of microplastics in marine waters upon degradation (Higgins & Turner, 2023; Peng et al., 2021). Microplastics can enter the river system through industrial effluents (Alam et al., 2019), stormwater runoff (Kabir et al., 2023), and discharge from wastewater treatment plants (Kay et al., 2018). The estuaries act as temporary sinks that transport the microplastics from the rivers to the marine system (Malli et al., 2022). Microplastics that originate from land can also enter the marine ecosystem through river discharge (van Wijnen et al., 2019), stormwater runoff (Werbowski et al., 2021), and beach litter (Paler et al., 2019). The various pathways through which microplastics enter soil include plastic mulching (Huang et al., 2020), landfills (Upadhyay & Bajpai, 2021), tire and road wear (Jarlskog et al., 2020), and sewerage systems (Rathore et al., 2024).

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Microplastics are known to cause adverse impacts on plant and human health (Khalid et al., 2020; de Souza Machado et al., 2020), marine life (Andrady, 2011; Gola et al., 2021), and ecosystem (Prata et al., 2020; Smith et al., 2018). Moreover, they act as vectors for the adsorption and facilitated transport of various contaminants (Amelia et al., 2021; Tumwesigye et al., 2023). Microplastic transport through each of the environmental compartments is governed by various physicochemical processes, and it is influenced by the physical properties of microplastics (type, size, density, and shape) (Chubarenko et al., 2016), environmental factors (wind speed, temperature, and water currents) (Feng et al., 2022), human activities (urban runoff, wastewater treatment plant discharge, plastic mulching in agriculture) (Sun et al., 2022), biological factors (presence of microorganisms) (Kooi et al., 2017), and chemical factors (pH, organic matter, and presence of contaminants) (Tumwesigye et al., 2023; Zhao et al., 2022). Understanding the transport processes and the associated factors is essential for estimating the extent of microplastic contamination and thereby protecting the environment and human health. Microplastic transport processes are greatly influenced by their density, size, and shape. The most commonly detected microplastic polymers are polypropylene (PP), polyethylene (PE), PE terephthalate (PET), polyvinyl chloride (PVC), polystyrene (PS), and expanded polystyrene (EPS) (Malankowska et al., 2021; Lv et al., 2019). PP (density: 0.85–0.92 g/cm3), PE (density: 0.92–0.96 g/cm3), and EPS (density: 0.02–0.06 g/cm3) are low-density polymers, whereas PVC (density: 1.30–1.45 g/cm3) and PE terephthalate (density: 1.38–1.67 g/cm3) are high-density polymers (Li et al., 2018; Weinstein et al., 2016). Moreover, depending on the source of origin, microplastics are found to have many shapes, including fragments, fibers, beads, and pellets (Klein et al., 2015; Lehtiniemi et al., 2018). Many studies have investigated the occurrence and distribution of microplastics in various environmental compartments through field sampling and analysis (Prata et al., 2020). However, challenges in sample analysis due to the wide distribution in size, shape, and type of microplastics and the necessity for high spatial and temporal resolution samples limit the amount of data available for quantitative analysis. On the other hand, mathematical modeling provides a comprehensive tool to simulate microplastic transport through various environmental compartments. The various modeling techniques used to study the fate and transport of microplastics are hydrodynamic modeling, statistical modeling, mass balance modeling, and process-based modeling. The hydrodynamic models are used to simulate the water movement by using various input parameters such as wind and current data, tidal fluctuations, river discharge, temperature, salinity, bathymetry, and depth of water (Besseling et al., 2017; Critchell et al., 2015; Ding et al., 2019; Enders et al., 2015). The statistical models are based on probabilities of the particle location and are solved using Monte Carlo or Markov analysis (Maximenko et al., 2012; Sherman & van Sebille, 2016). Mass balance models are based on the inflow and outflow concentrations of the microplastics in their governing equations and are mainly dependent on the field observation data such as microplastic number concentration from the sampling location and plastic loads into the water bodies (Koelmans et al., 2017; Siegfried et al., 2017). Process-based models simulate the transport of microplastics by accounting for various mechanistic processes such as aggregation, biofouling, degradation, sedimentation, etc. (Kooi et al., 2017; Shiravani et al., 2023). The hydrodynamic model needs to be coupled with process-based and statistical models as the transport of microplastics depends on water flow. These types of models are mainly

9.1 Introduction

called hybrid models. The main drawback of mass-balance models is that they do not account for the hydrodynamic data. Yu et al. (2018) coupled the Regional Ocean Modeling System (ROMS) with the Larval TRANSport (LTRANS) Lagrangian particle tracking transport model to study the distribution of microplastics in the coastal sites of the southeastern United States. Besseling et al. (2017) adopted the NanoDUFLOW model, a submodel of the DUFLOW hydrological model, which accounts for various microplastic transport processes in the river ecosystems such as homoaggregation, heteroaggregation, sedimentation, dissolution, degradation, resuspension, and burial. Liubartseva et al. (2016) used a Lagrangian particle tracking model by applying the Monte Carlo technique for the beaching and sedimentation of microplastics. Table 9.1 provides the various types of models and the factors accounted for to study the fate and transport of microplastics. The hydrodynamic-process-based models are highly versatile and can represent the realistic microplastic transport processes in the environment reasonably well. Hence, this chapter deals with hydrodynamic-process-based hybrid models to simulate the fate and transport of microplastics in various environmental aquatic compartments. This chapter discusses the various processes associated with microplastic transport in various environmental aquatic compartments such as marine ecosystems, riverine ecosystems, estuarine ecosystems, and soil ecosystems and the available hydrodynamic-process-based hybrid models to simulate microplastic transport in each compartment.

Table 9.1 List of Various Models in Different Environmental Compartments and Their Influencing Factors Environment simulated

Reference

Type of model

Model name

Influencing factors

Critchell et al. (2015)

Hydrodynamic

Secondgeneration Louvain-laNeuve Ice-ocean Model (SLIM 2D)

Marine

Current and wind velocity, sea level data, wind drift coefficient

Ballent et al. (2013)

Hydrodynamic

Modelo Hidrodinâmico (MOHID)

Marine

Wind velocity and direction

Liu et al. (2021)

Hydrodynamic

Regional Ocean Modeling System (ROMS)

Marine

Sea bed topography data, monthly surface heat, freshwater fluxes, salinity, temperature, and seawater velocities

Handyman et al. (2019)

Hydrodynamic

Mike 21 flow model

Marine

Bathymetry, tidal elevation, wind fields

Kooi et al. (2017)

Process-based

Numerical model

Marine

Biofilm growth, settling velocity

Shiravani et al. (2023)

Process-based

Numerical model

Estuaries

Sedimentation, flocculation, resuspension (Continued)

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Table 9.1 (Continued) Environment simulated

Reference

Type of model

Model name

Siegfried et al. (2017)

Mass balance

Global Nutrient Export from Water Sheds (NEWS)

Rivers

Density population connected to sewage systems, per capita input of microplastics, and sewage treatment efficiency

Koelmans et al. (2017)

Mass balance

Mass balance equations

Marine

Annual plastic input into the oceans

van Wijnen et al. (2019)

Mass balance

Global Riverine Export of Microplastics into Seas model (GREMiS)

River

Microplastic input into rivers from point and diffuse sources

Van Sebille et al. (2015)

Statistical

General Additive Model (GAM)

Ocean

Wind speed, sampling time and trawl length

Besseling et al. (2017)

Hybrid (Hydrodynamicprocess based)

NanoDUFLOW

River

River water levels, river discharge, and mean velocity in the river

Critchell and Lambrechts (2016)

Hybrid (Hydrodynamicprocess based)

SLIM model

Marine

Hydrodynamic data like current and wind velocities, and beaching, settling

Jalon-Rojas et al. (2019)

Hybrid (Hydrodynamicprocess based)

TrackMPD

Marine

Current velocity, dispersion, sedimentation, degradation, biofouling, and beaching

9.2

Influencing factors

Transport Mechanisms of Microplastics in the Environment

The distribution, fate, and transport of microplastics in the environment depend on various physicochemical and biological processes such as degradation, beaching, drifting, dispersion, flocculation, sedimentation, and biofouling. Figure 9.1 shows the schematic representation of the transport processes occurring in various environmental compartments. Each of these processes is explained in detail in the below paragraphs.

9.2.1

Degradation

Degradation is the fragmentation of larger plastics/mesoplastics (size >5 mm) into microplastics. The degradation of plastics is affected by factors such as ultraviolet radiation (Klein et al., 2015; Xu et al., 2020), wave and tide action (Malli et al., 2022), distance of the plastic source from the water body (Isobe et al., 2014), and microbial activity (Othman et al., 2021). The various mechanical and chemical processes involved in degradation can be identified

SEWAGE TREATMENT OCEAN

BEACHING

INDUSTRY EFFLUENT

DRIFTING

AGRICULTURAL RUNOFF

ESTUARY

TURBULENT MIXING

INGESTION

RIVER RESUSPENSION

SEDIMENT FLOCCULATION

AGGREGATION BIOFOULING

SINKING

RESUSPENSION

SINKING

BIOFOULING

SINKING

OCEAN BED

SINKING

RESUSPENSION RIVER BED

SUBSURFACE MICROPLASTIC

DEPOSITION ON SOIL

Figure 9.1

Schematic Representation of Microplastic Transport Processes in the Aquatic Environment

SINKING

SINKING

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9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

by the surface textures of sampled microplastics (Corcoran et al., 2009). For example, the presence of pits on microplastics indicates dissolution due to chemical weathering. The subangular to rounded microplastic pellets having linear and conchoidal fractures form as a result of particle–particle impact and saltation. The presence of cyanobacteria, proteobacteria, and firmicutes can also degrade microplastics through the release of enzymes during microbial activity (Yang et al., 2021). Degradation of marine plastics is more prominent on shores than in seawater due to greater mechanical erosion at the shores (Isobe et al., 2014). Isobe et al. (2014) observed that the drift density of the microplastics decreased as their sizes approached the lower sampling limit of 0.3 mm. This means smaller microplastics are less in number, and microplastics having a size less than a few hundred micrometers may be resistant to degradation. Furthermore, it was observed that the degradation of larger-sized microplastics can also occur at shorter distances from river mouths (Isobe et al., 2014). The deeper sediment conditions in the river ecosystem provide favorable conditions for the biodegradation of microplastics (Niu et al., 2021). The degradation of microplastics in the soil ecosystem depends on the microbial activity, pH, and organic matter of the soil (Zhao et al., 2022). The time scale for the degradation of microplastics can vary from years to decades depending on the type of microplastics (Liao & Chen, 2021) and the biodegradation rate (Lott et al., 2021; Xiang et al., 2023). Jalon-Rojas et al. (2019) reported the degradation rates for microplastics in Jervis Bay, Australia varied from 0.1% per day to 3% per day for microplastic sizes ranging from 1 to 5 mm. The time required for the degradation is often measured in terms of half-life, and it is expressed as a function of the removal rate constant of microplastics due to degradation (Noro & Yabuki, 2021; Xiang et al., 2023).

9.2.2

Beaching

The movement of microplastics toward the coastline and its accumulation is termed as beaching. The accumulation of microplastics is influenced by human activities, the source of microplastics (Browne et al., 2011; Van Der Mheen et al., 2020), wind drift velocity (Andrady, 2011; Critchell & Lambrechts, 2016), and river mouth proximity (Constant et al., 2019). Wind direction and source location are the most important factors influencing the beaching of microplastics, with a greater rate of beaching when the source is close to the coast and in the windward direction (Critchell & Lambrechts, 2016; Critchell et al., 2015). The beached microplastics can get resuspended based on their size, e.g. large-sized plastics (mesoplastics) may move toward the shoreline and on abrasion may move offshore (Isobe et al., 2014; Tziourrou et al., 2021). The river mouth acts as the hot spot for the accumulation of microplastics due to greater microplastic concentration as compared to coastal waters (Constant et al., 2019; Isobe et al., 2014). This, in turn, indicates a greater probability of the accumulated microplastics entering the marine food chain. The beached microplastic pellets can act as adsorbents for various heavy metals including Fe, Al, Zn, and Cu, thereby facilitating their transport (Ashton et al., 2010; Frias et al., 2010; Vedolin et al., 2018).

9.2.3

Drifting

The movement of microplastics in terrestrial and aquatic environments due to ocean currents, wind, and wave action is termed drifting. Drifting of microplastics is more prominent in oceans due to the presence of strong tidal motion and wave currents (Lee & Choi, 2023;

9.2 Transport Mechanisms of Microplastics in the Environment

Sterl et al., 2020). On land, drifting is influenced by sediment transport and anthropogenic activities (Abolfathi et al., 2020). Buoyancy, wave currents, and Stokes drift velocity are the major processes involved in the drifting of microplastics (Iwasaki et al., 2017; Onink et al., 2019). Ocean currents have high-temporal variability of velocities due to seasonal changes, thus affecting the drifting of microplastics. In addition to the horizontal movement, microplastics can also move in the vertical direction due to vertical turbulent mixing and are dependent on the breaking waves and Langmurian currents (Lee & Choi, 2023). The vertical mixing increases with particle density and decreases with particle size, thus leading to the selective transport of heavier microplastics to the ocean surface. Large microplastics less dense than sea water travel at a larger velocity than denser microplastics due to surface drifting. However, large nonbuoyant microplastics get rather deposited on shore sediments (Onink et al., 2019). This is mainly due to the friction and Stokes drift velocity and hence, causes selective transport of microplastics (Isobe et al., 2014). Wind drift velocity plays a crucial role in floating the plastic debris with the wind drift coefficient ranging between 1 and 6% (Isobe et al., 2014). Wind drift velocity is often neglected for submerged plastic debris (Reisser et al., 2013). The type of plastics drifting into the oceans, such as nanoplastics, microplastics, or mesoplastics can be inferred based on drift density; i.e. the number of microplastic pieces/m3 of water (Isobe et al., 2014). The drifting of microplastics from the ocean surface to the accumulation regions can be described using the Lagrangian transport model by incorporating Ekman currents, geostrophic currents, and Stokes drift velocity in the advective phase (Bigdeli et al., 2022; Onink et al., 2019). It is to be noted that in the water bodies, the tidal, wind, and wave action lead to the transport of microplastics due to advection (Bigdeli et al., 2022).

9.2.4

Dispersion

Dispersion of microplastics indicates its spreading due to turbulence. Horizontal dispersion is mainly driven by water movements and vertical dispersion is by vertical mixing (Bigdeli et al., 2022). Horizontal dispersion is prominent at the reefs and coastal waters due to shear flows (Critchell et al., 2015). Vertical dispersion depends on the turbulence caused by wind currents and the depth measured downward from the water surface (Song et al., 2018). Dispersion for oceans ranges between 10 m2/s and 10−2 m2/s (Critchell et al., 2015; Isobe et al., 2014) and for river systems it ranges between 0.002 and 0.02 m2/s (Stride et al., 2024). Typically, dispersion is greater for marine systems due to greater turbulence, ocean currents, and tidal fluctuations.

9.2.5

Flocculation

Flocculation is the aggregation of microplastics due to their interaction with suspended sediments, organic matter, and biofilms to form floc-like structures (Andersen et al., 2020; Cole et al., 2016; Kaiser et al., 2017). Flocculation affects the buoyancy and settling rates of microplastics (Laursen et al., 2022). The large concentration of organic matter leads to the formation of denser flocs having large settling velocities (Larsen et al., 2023). Coagulation-flocculation process is more prominently used in aquatic environments for the removal of microplastics. There, chemical substances such as magnesium hydroxide (Li et al., 2022), aluminum sulfate (Li et al., 2021), and iron and polyamine-based chemicals

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9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

(Rajala et al., 2020) are added as coagulants. The affinity of microplastics to various coagulants to form flocs depends on pH, type of microplastics, and concentration of coagulant (Li et al., 2021). Flocculation of microplastics is mainly dominant in freshwater bodies such as lakes, rivers, and estuaries due to the presence of large sediment concentrations (Shiravani et al., 2023).

9.2.6

Sedimentation

Depending on their density, microplastics can either settle at the bottom of the water bodies or float on the water surface. In freshwater bodies such as lakes and rivers, settling sediments act as a sink for microplastics. However, the settled microplastics on sediments can be resuspended, thereby recontaminating the water body. The settling of microplastics in the sediment region can be due to (a) formation of biofilms around the microplastics leading to their increased density (Chen et al., 2019; Kaiser et al., 2017; Kooi et al., 2017); (b) ingestion of microplastics by zooplanktons and disposal through their feces (Wang et al., 2019); (c) fragmentation of large pieces of microplastics (Zhang et al., 2021a); (d) calcite precipitation facilitated by cyanobacteria leading to loss of buoyancy (Leiser et al., 2021); or (e) aggregation of microplastics with natural sediments and phytoplankton present in the water bodies (Li et al., 2019; Lagarde et al., 2016). The settled microplastics may get resuspended in the overlying water bodies or get transported to deeper sediments due to weather disturbances such as eddy current formation (Li et al., 2022; Xia et al., 2021), tidal fluctuations (Feng et al., 2023; Wu et al., 2022), or mixing of sediments (Serra & Colomer, 2023). The deposition rate of microplastics in sediments can be calculated using the inflow and outflow rates of microplastics in the rivers (Zhang et al., 2021b). Sensitivity analysis conducted by Critchell and Lambretchs (2016) for marine ecosystems and Shiravani et al. (2023) for estuarine ecosystems showed that sedimentation is the most dominant process for microplastics as compared to other processes. However, it is difficult to conclude the dominance of sedimentation across various ecosystems as the sedimentation process is dependent on the density of microplastics, size of microplastics, and thickness of biofilm.

9.2.7

Biofouling

Biofouling is the process of formation of biofilms on the surface of microplastics. The formation of biofilm on microplastics depends on the type of polymer, the specific surface area of microplastics, availability of light for the growth of bacteria, and temperature (Kaiser et al., 2017; Kooi et al., 2017). Biofouling increases the size, surface area, density, and surface roughness of microplastics, and affects its hydrophobicity (Wang et al., 2021). Biofilm on microplastics releases enzymes due to biogeochemical reactions leading to microplastics’ degradation, thereby decreasing the size of microplastics (Debroy et al., 2022). Hence, biofilm affects the settling rate of microplastics. If the density of biofouled microplastics is greater than that of seawater, microplastics will undergo settling (Kooi et al., 2017). Kaiser et al. (2017) observed that the sinking velocities of microplastics due to biofilm formation were greater in marine waters than in estuarine waters due to greater salinity in marine waters which promoted biofilm growth.

9.3 Modeling the Fate and Transport of Microplastics in Riverine Environment

The rate of settling of biofouled microplastics depends on the shape and distribution of biofilms. Jalan-Rojas et al. (2019) reported a greater settling velocity of microplastic fibers than sheets due to the nonuniform distribution of biofilm on the sheets. The sinking dynamics of biofouled microplastics depend on their size and density (Kooi et al., 2017; Ryan, 2015), surface area-to-volume ratio (Chen et al., 2019), the type of microplastics (Liu et al., 2022; Miao et al., 2021), and the growth and mortality rates of algae (Kreczak et al., 2021; Liu et al., 2022). Defouling of submerged microplastics can subsequently happen due to the limitation of light and dissolution (Cozar et al., 2014), restricted microplastic submersion at thermocline depth due to an increase in seawater density (Ye & Anrady, 1991), and resurfacing of microplastics (Kooi et al., 2017). Biofilm-coated microplastics have a greater affinity to metal ions and organic pollutants due to electrostatic interaction, surface complexation, and precipitation, thus acting as carriers for contaminants (Guan et al., 2020; Wang et al., 2021).

9.3 Modeling the Fate and Transport of Microplastics in Riverine Environment Rivers receive microplastics from various sources including degraded plastic waste from land (Barnes et al., 2009; Thompson, 2006; Zbyszewski et al., 2014), discharge from plastic manufacturing industries (Lechner & Ramler, 2015), cosmetic products and toiletries (Arthur et al., 2009; Browne et al., 2011; Horton et al., 2017b), degraded plastic mulch films from agricultural lands (Nizzetto et al., 2016), and sewage treatment plants (Ferronato & Torretta, 2019; Jambeck et al., 2015; Kay et al., 2018; Mintenig et al., 2017). Microplastics in rivers are transported through a complex interplay of hydrodynamic, biological, and environmental mechanisms (Besseling et al., 2017). Hydrodynamic transport involves surface flow where lighter microplastics float downstream, and suspended load where smaller and lighter particles remain in the water column influenced by flow velocity, turbulence, and water density (Besseling et al., 2017; Nizzetto et al., 2016). Heavier microplastic particles, or those attached to sediments, move along the riverbed as a bed load particularly during high-flow events like floods (Castaneda et al., 2014; Klein et al., 2015; Peng et al., 2018). Turbulence caused by river flow, obstacles, and riverbed topography enhances mixing and dispersion, and distributing microplastics vertically from the surface to the bottom layers of the river. Microplastics interact with sediments through adsorption and desorption and are affected by pH, salinity, and temperature. Sedimentation causes microplastics to settle and accumulate in riverbeds during low-flow conditions. Biological interactions further influence their transport, e.g., aquatic organisms ingest microplastics, thereby leading to bioaccumulation and movement through feeding and migration (Bellas et al., 2016; Lestari et al., 2020). The models in the literature that can be used to understand the fate and transport of microplastics in riverine environments are discussed below. Table 9.2 provides the summary of the models developed in the literature to investigate the transport of microplastics in riverine environments. The general form of the governing equation for the transport of microplastics in rivers can be written as Eq. (9.1)

215

Table 9.2

List of Studies on Modeling Microplastic Transport in Riverine Environment

Reference

Modeled processes

Model

Site location

Values of parameters

Major findings

De Arbeloa and Marzadri (2024)

Advection, dispersion

1D Advection dispersion equation integrated with river hydraulics and microplastic input

Mignone river, Italy; DuPage river, United States; Elbe river, Germany

NA

Higher microplastic concentrations were observed in the headwaters stream and the concentrations got diluted during downstream.

He et al. (2021)

Hydrodynamics, particle erosion, resuspension, settling,

3D hydrodynamic and particle transport model, TUFLOW FV

Brisbane River, Australia

NA

Sediment microplastics with lower densities were highly mobile. High flow transported more microplastics from the source, and higher velocity in the bottom layer increased sediment transport

Whitehead et al. (2021)

Settling, deposition, mixing, and resuspension

INCA-Contaminants 1D particle transport model embedded with sediment transport

Thames River, United Kingdom

NA

Microplastics were observed along the entire riverbed, and dominant deposition was observed at the riverbed

Besseling et al. (2017)

Sedimentation, Homoaggregation, heteroaggregation, degradation, burial and resuspension

DUFLOW-1D unsteady flow in open channels and NanoDUFLOWparticle transport model

Dommel river, The Netherlands

ws = 8.47E-40 to 5.18E-03 mg/kg dcni = 4.48 × 10−19 to 0.31 dt no. m−3s−1; dcnj = 9.38 × 10−6 to 1.9 × dt 103 no.m−3s−1; kdeg = 6.81 × 10−9 s−1; kbur = 3.17 × 10−9 s−1; Rjmax = 100 g m−2day−1

Particle size significantly influenced the fate and retention of microplastics and the sediment accumulation hotspots. Submicron particles and larger micro- and millimetersized plastics are more likely to be retained

Nizzetto et al. (2016)

Settling, deposition, and entrainment

INCA-Contaminants 1D particle transport model embedded with sediment transport

Thames River, London

NA

Larger microplastic particles with densities slightly higher than water are prone to be retained in sediment but may be remobilized during high-flow periods. Sediments in river sections with low stream power are likely hotspots for MP deposition

Siegfried et al. (2017)

Point source microplastic fluxes

Global NEWS-data driven model

European seas

NA

Synthetic polymers (42%), plastic-based textiles from laundry (29%), household dust (19%), and microbeads in personal care products (10%) are major microplastics exported to sea.

9.3 Modeling the Fate and Transport of Microplastics in Riverine Environment

∂c ∂2 c ∂c = DL 2 − v sedimentation rate + resuspension rate ∂t ∂x ∂x + burial rate homoaggregation rate + heteroaggregation rate + degradation rate 91 Here, c [ML−3] is the concentration of microplastics along the river reach, DL[L2T−1] is the longitudinal dispersion coefficient along the river reach, v[LT−1] is the mean stream velocity, x [L] is the spatial coordinate, and t [T] is the time. Mechanisms such as sedimentation, resuspension, degradation, dissolution and burial, homo and heteroaggregation, influence the fate and transport of microplastics in riverine environments. The hydraulic properties of a river stretch can be calculated using Eqs. (9.2a through c) (De Arbeloa & Marzadri, 2024). w = a Qb

9 2a

h = i Qd

9 2b

v = e Qf

9 2c

Here, w[L] is the channel width, h[L] is the mean flow depth, v[LT−1] is the average velocity in the river, a, b, i, d, e, f are the hydraulic geometry coefficients, and Q[ML−3] represents the river discharge. The dispersion coefficient can be calculated in terms of the river slope Si and the kinematic wave celerity, vw[LT−1] as per Eq. (9.3) (De Arbeloa & Marzadri, 2024) DL =

vw h 3Si

93

3 v . The vertical velocity profile, ux(z) in rivers can be calculated as per 2 Eq. (9.4) (Geng et al., 2023).

Here, vw =

ux z 1 z = ln u∗ κ ks

+w+χ

94

Here, z is the water elevation above the streambed, κ = 0.41 is the Von Karman constant, ks[L] is the riverbed roughness height, χ is an empirical constant, u∗[LT−1] is the friction velocity, and w is the wake function which can be expressed as Eq. (9.5). u∗ =

gSRh ; w z =

2π πz sin2 κ 2h

95

Here, S is the slope of the river, Rh[L] is the hydraulic radius, h[L] is the water depth, and π is the wake strength parameter. Roughness at the river boundary can be accounted for by deriving the eddy viscosity profile as indicated in Eq. (9.6). vt z z = κ z + zb 1 − u∗ h

1−

z z + zs 2 h h

96

217

218

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

Here, zb[L] and zs[L] represent the roughness heights at the river bottom and the surface, respectively. The parameter, ks[L] represents the bottom roughness height which can be calculated from the Eq. (9.7). n 1 6 Rh

1

=

21 9 log 12 2

Rh ks

97

Here, n denotes the Manning roughness coefficient. The horizontal and vertical random walk velocity component is scaled by the horizontal and vertical diffusivity (nu) given by Eq. (9.8) (He et al., 2021): u ,v = R

2nu∗dt dnu 2nu ∗dt dnu ;w = ; z = z0 + 0 5 +R ∗dt dt dt dz dz

98

Here, nu[L2T−1] is the horizontal diffusivity, dt[T] is the Lagrangian timestep, R is the randnu dom number from a standard Gaussian distribution, is the vertical diffusivity gradient, dz and nu is the vertical diffusivity evaluated at z . Sedimentation is another mechanism responsible for the transport of microplastics in rivers. Besseling et al. (2017) calculated separate sedimentation rates for each of the plastic particle sizes, homoaggregate class, suspended solid class, and heteroaggregate class during the transport of microplastics in the Dommel River stretch using the formulation given in Eq. (9.9). dcnj ws cnj = − dt d

99

Here, cnj [no. L−3] represents the particle number concentration of a particular heteroaggregate microplastic particle of size class j, d [L] is the sedimentation length and the settling velocity, ws[LT−1] represents the settling velocity, which can be calculated using Stokes law. The sedimentation rate of free microplastics and the suspended heteroaggregates was calculated based on the size (aj [L]) and density of the suspended solids and plastic particles present in heteroaggregates. Disturbances in the sediment bed can lead to the re-entrainment of microplastics to the overlying water layers. The rate of re-entrainment of microplastics from the sediment into the overlying waters can be calculated as per Eq. (9.10) (Nizzetto et al., 2016). dcnj = a8 cnj ωf r MP dt

9 10

Here, ω [MT−3] is the stream power unit of the bed surface, f [−] is the dimensionless friction factor, a8 [M−1T2] is a tunable scaling factor, and rMP[−] is the entrainable fraction of microplastics of a given class size. However, Besseling et al. (2017) assumed that the top 10 cm of sediment layer to be available for resuspension and the mechanism of resuspension was expressed using a critical shear stress level below which resuspension will not happen. When critical shear stress is exceeded, the rate of resuspension can be calculated as follows (Eq. 9.11): dcnj τ −1 = Rj max dt τcr

9 11

9.3 Modeling the Fate and Transport of Microplastics in Riverine Environment 2

g0 5 vw

where τ M L − 1 T − 2 = ρw

Chezy

is the shear stress, τcr [M L−1T−2] is the critical

shear stress, Rjmax [no. L−2T−1] is the maximum resuspension rate constant for suspended solids or plastic-suspended solid heteroaggregates, vw[L]T−1 is the water flow rate, and Chezy is the chezy coefficient. Some portion of the sediment can also get buried into the deeper layers of the sediment during the river bed disturbances and during such cases, the dissolution or burial of microplastics into the deeper layers can be estimated as per Eq. (9.12) (Besseling et al., 2017). dcnj = − k bur cnj dt

9 12

Here, kbur [T−1] is the sediment burial rate for microplastic particles of a specific size class. Homoaggregation and heteroaggregation are two other mechanisms responsible for the fate and transport of microplastics in riverine environments. Homoaggregation is the process where plastic particles interact with each other to form aggregates in the water phase. Von Smoluchowski equation can be used to simulate the homoaggregation of microplastics, and it is given below (Eq. 9.13) (Besseling et al., 2017; Geng et al., 2023). dcnj 1 = dt 2

i = j−1

αi,j − 1 K i,j − 1 cni cnj − 1 − cj i=1

i= ∞

αi,j K i,j cni

9 13

i=1

Here, αi, j[−] indicates the attachment efficiency of microplastic particle i with j, and Ki,j [no.−1L3T−1] represents the collision frequency of particle i with j and cni [no. L−3] represents the particle number concentration of a particular homoaggreagte microplastic particle of size class i. The collision frequency can be calculated using Eq. (9.14) (Besseling et al., 2017). K i,j =

2k b T ai + aj ai a j 3μ

2

+

4 G ai + aj 3

3

+

2πg ρ − ρw 9μ p

ai + aj ai − aj

109

9 14

Here, kb[ML2T−2K−1] is the Boltzmann constant, T [K] is the temperature, μ [ML−1T−1] represents the viscosity, a is the particle radius, G [T−1] is the shear rate, and g [MT−2] is the acceleration due to gravity. Heteroaggregation represents the interaction of plastic particles with suspended solids to form aggregates. The rate of change in heteroaggregate concentration can be calculated using attachment efficiency and collision frequency as given in Eq. (9.15) (Besseling et al., 2017). dcnj = − αhet cnj dt

i

9 15

K j,SSi nSSi 1

Here, nSSi is the number of size classes of suspended solids, αhet is the attachment efficiency of heteroaggregation and K j,SSi is the collision frequency of particle j with the suspended solids, which can be given as Eq. (9.16): K j,SSi =

2k b T aj + aSSi aj aSSi 3μ

2

+

4 G aj + aSSi 3

3

+ π aj + aSSi

2

vs,j − vs,SSi

109

9 16

219

220

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

where the term G [T−1] represents shear rate. These expressions provide a direct link between river morphometry, hydrology, and aggregation behavior. Physical weathering can also lead to the degradation of microplastics, and it can be simulated using a first-order model as given in Eq. (9.17). dcnj = − k deg cnj dt

9 17

where, kdeg[T−1] is the degradation rate constant. All the microplastic transformation processes take place mostly in the water phase. However, the mechanisms such as heteroaggregation and degradation can also happen in the sediment phase due to the abundance of suspended solids. The formation of biofilm on plastic particles affects its size, density, and, hence, the settling rates. It involves adjustment of the total radius and overall density of the plastic particle as a result of biofilm. Attachment efficiencies for plastic particles in the presence of biofilm can be simultaneously changed by including a factor accounting for the increased size of the microplastic particles. Besseling et al. (2017) simulated the transport of nano-, micro-, and millimeter-sized spherical or near-spherical plastic particles in freshwater using a one-dimensional NanoDUFLOW hydrodynamic model. The transport of PS particles with sizes ranging from 100 nm to 10 mm aggregating with kaolinite or bentonite clays was simulated and also the effect of biofilm was incorporated into the model. Their model captured spatially and temporally explicit hydrodynamic particle behavior considering advective transport, particle aggregation (homoaggregation and heteroaggregation), sedimentation, resuspension, polymer degradation, dissolution, and burial. Figure 9.2 presents the results of the simulated spatial distribution of plastic particles in the water column and also in the sediment phase over the Dommel River stretch, Netherlands (Besseling et al., 2017). Figure 9.2 clearly shows that the concentration profiles of microplastics present in the river reach can be correlated to the size of the particles. Larger-sized heteroaggregates in the range of 100 nm–5 μm deposit as sediments as compared to individual plastic particles. Moreover, the settling rates of large microplastic particles are independent of their heteroaggregation rate. The concentrations of singular microplastic particles of size 100 nm in the water phase decreased with distance, which can be due to the increase in heteroaggregate concentrations. Nizzetto et al. (2016) integrated the INCA-Contaminants model for catchment hydrology with soil erosion and sediment budgets to simulate the fate and transport of microplastics. The sediment transport model used direct runoff fluxes and predicted stream flow regimes to calculate entrainment and depositions of particles from/to riverbed sediments. The numerical model was used to simulate microplastic transport in Thames River reach and it was observed that heavier and larger microplastic particles get mobilized during high flow periods. However, the smaller microplastic particles get transported efficiently independent of their densities. These results suggest that a strong correlation exists between the size of microplastics and the flow regime during their transport. In another study, Whitehead et al. (2021) also used similar model formulations to investigate the microplastic transport in the Thames River. Predicted concentrations and microplastic loads moving along the river system showed increased microplastic deposition on the riverbed. De Arbeloa and Marzadri (2024) developed an integrated modeling framework to simulate microplastic transport in rivers by combining the data for microplastic transport from the advection–dispersion equation, point source inputs, and the data on river network and catchment characteristics. Figure 9.3 presents the breakthrough curves from the model simulations

9.3 Modeling the Fate and Transport of Microplastics in Riverine Environment

Figure 9.2 Spatial Distribution of Plastic Concentrations along the Dommel River, in the Water Column (Left-Sided Panels) and in the Sediment (Right-Sided Panels) for Different Size Classes of Plastic Particles After 9 days of Plastic Input into the River (Source: Reprinted from Besseling et al. (2017), copyright 2017, permission obtained from Elsevier)

for the Mignone River in Italy. The breakthrough curves appear to be evolving like a rectangular pulse, which shows the dominance of advection over the upstream river reach due to shorter river lengths. However, as the microplastics move downstream, the shape of breakthrough curves shows variability due to the spatial variation of river characteristics and the input sources of microplastics along the river network. The mean concentration of microplastics varied from 117.19 μg/L in the downstream reach of Mignone River to that of 3,912.33 μg/L in the DuPage River. The maximum concentration of microplastics varied from 370.91 μg/L in the downstream reach of Mignone River to that of 19,343.75 μg/L in the Elbe River.

221

222

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

Figure 9.3 Breakthrough Curves (Left) and Map of Basins and River Network (Right), Indicating the Locations of Measurement Points in the Mignone River, Italy (Source: Reprinted from De Arbeloa and Marzadri (2024), copyright 2024, permission obtained from Elsevier)

He et al. (2021) investigated the transport of microplastics in the Brisbane River, Australia, by integrating a three-dimensional hydrodynamic model (TUFLOW FV) with a Lagrangian particle tracking model (TUFLOW FV PTM). Monitoring points were selected with an interval distance of 15 km from the upstream to the downstream section of the river. Three-dimensional map outputs and particle tracking data from the model results were compared with field data published in the literature. Figure 9.4 shows the transport distance of different microplastic particles at various monitoring points. The results showed that the lighter microplastic particles PE and PP were transported for a relatively longer distance, while polyamide and PE terephthalate got accumulated close to source points. These results also confirm that the river sediments act as a sink for heavier microplastic pollutants instead of enhancing their transport in rivers. Apart from the existing process-based models, some studies also used data-driven models. Siegfried et al. (2017) used a data-based model to analyze the concentration and composition of microplastics during their transport from European rivers to the sea. The microplastics exported by the rivers to sea are composed of 42% of synthetic polymers, 29% of laundry plastic-based textiles, and 29% of plastics from households, which include plastic fibers, synthetic polymers, and microbeads from personal care products. The modeling approach was adopted from the Global NEWS (Nutrient Export from Watersheds) model, which determines the point source input of nutrients to rivers from sewage. Figure 9.5 presents the schematic representation of point source inputs of microplastics into the river and their export to the river mouth. The quantity of microplastics from point sources entering the river and being exported to the river mouth can be termed as microplastic yield and can be calculated using the formulation given in Eq. (9.18) (Siegfried et al., 2017).

4 PE

PP

PA

PET

PE

PP

PA

PET

0

0

PE

PP

PA

PET

0

–2

–2

–2

–4 –4 –6 –6

M1

–4

M2

–8 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Mar Apr May Jun Month

M3

Jul Aug Sep Oct Nov Dec Jan Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Month

Month

6

4 PE 2 Distance (km)

2

2

2 Distance (km)

4

PP

PA

PET

4

PE

PP

PA

PET

2 0 –2

0 –2

–4

–4

–6 –8

–6

–10

–12 –14 M5 –10 –16 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Mar Apr May Jun Month –8

M4

Jul Aug Sep Oct Nov Dec Jan Month

Figure 9.4 Transport Distances of Microplastic Particles at Monitoring Points. The “0” Value Represents the Monitoring Point, Positive Values Represent that the Transport Direction of Microplastics is Toward the Downstream Sections from the Monitoring Point and Negative Values Represent that the Direction of Microplastics Transport Is from Monitoring Point Toward the Upstream Sections (Source: Reprinted from He et al. (2021), copright 2021, permission obtained from Elsevier)

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

Density of population Per capita input of connected to sewage systems microplastics

Sewage treatment efficiency

Point-source microplastics input

Ri ve r

224

Sewage treatment

Consumptive water removal

Model inputs River inputs of microplastics from pointsources Microplastic fraction removed due to consumptive water removal and river retention Microplastic exported at the river mouth

River export (Yield) River retention

Figure 9.5 Schematic Overview of Microplastic Point-Source Inputs to Rivers and Export to the River Mouth (Source: Reprinted from Siegfried et al. (2017), copyright 2017, permission obtained from Elsevier) n

YldMP =

FE riv,i × RSpnt,i

9 18

i=1

Here, FEriv,i [−] represents the fraction of microplastics entering the rivers from point sources RSpnt,i. [ML−2T−1]. Microplastic loads were calculated from yields and the area of the river basin as per Eq. (9.19). LMP = YieldMP × A

9 19

where, LMP[MT−1] is the microplastic load, YieldMP [ML−2T−1] is the microplastic yield, and A [L2] is the basin area calculated from the Global NEWS model. Point source inputs of microplastics to the rivers can be calculated as Eq. (9.20). RSpnt,i = 1 − hwfrem,i × PConDen × WShw cap,i

9 20

Here, hwfrem,i [−] is the fraction of microplastics of type i being removed from sewage treatment and getting into the river stream as sewage influent. PConDen [inhabitant L−2] is the population density connected to the sewage system and WShwcap,i [capita−1MT−1] is the per capita input od microplastics of type i into the river basin. Figure 9.6 presents the river export of microplastics to the European seas in the year 2000, which was calculated using the Global NEWS model formulation. The results from the study showed that about two-thirds of the microplastics flow into the Mediterranean and Black Sea because of the relatively low microplastic removal efficiency of sewage treatment plants in the river basins draining into these two seas. Sewage treatment is generally more efficient in river basins draining into the North Sea, the Baltic Sea, and the Atlantic Ocean. Siegfried et al. (2017) also predicted the

9.3 Modeling the Fate and Transport of Microplastics in Riverine Environment

N W

E S

Legend Microplastic yield (kg km–2 year–1) in the year 2000 0 0.1–0.5 0.5–1 1–5 5–10 10–20 20–30 30–50 50–75 >75 Figure 9.6 River Export of Microplastics into the European Seas as Calculated for the Year 2000 (Source: Reprinted from Siegfried et al. (2017), copyright 2017, permission obtained from Elsevier)

225

226

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

future trends of river export of microplastics up to the year 2050 and observed an increase in microplastic yield in some river basins, but a decrease in yield in some other basins, which can be attributed to the improved efficiency of sewage treatment plants in such basins.

9.4 Modeling the Fate and Transport of Microplastics in Estuaries Estuaries are the major pathways of microplastics into the marine environment. They receive microplastic loading from rivers. Hence, it is essential to understand the loading rate and the transport pathways of microplastics in estuarine beds. The main factors that affect the microplastic circulation in the estuaries are density variation due to the mixing of river and sea, thus leading to a salinity gradient, river discharge on the upper part of the estuary, and tidal fluctuations at the lower part of the estuary (Malli et al., 2022; Diez-Minguito et al., 2020). The various processes involved in the transport of microplastics in estuaries are advection, dispersion, sedimentation, resuspension, and biofouling. The governing equation for the transport of microplastics in estuarine bodies using the Eulerian approach is described using the following Eq. 9.21: ∂c ∂2 c ∂2 c ∂2 c ∂c ∂c ∂c = K x 2 + K y 2 + K z 2 − u − v − w + ws − wres ±R ∂t ∂x ∂y ∂z ∂x ∂y ∂z

9 21

Here, Kx [L2T−1], Ky [L2T−1], and Kz [L2T−1] are diffusion coefficients of microplastics in x,y, and z directions due to turbulent mixing, respectively, u [LT−1], v [LT−1], and w [LT−1] are the advective velocities of microplastics in x,y, and z directions, respectively, wres [LT−1] is the resuspension velocity of the microplastics and R is the source or sink term. The random walk particle tracking equation for the movement of microplastics in estuaries is given by Eqs. (9.22) through (9.24). x t + Δt = x t + uΔt + R t

2K x Δt

9 22

y t + Δt = y t + vΔt + R t

2K y Δt

9 23

z t + Δt = z t + wΔt − ws Δt + wres Δt + R t

2K z Δt

9 24

where, x(t), y(t), and z(t) are the microplastic position in time t in x, y, and z directions, respectively, x(t + Δt), y(t + Δt), and z(t + Δt) are the microplastic position in time (t + Δt) in x, y, and z directions, respectively, Δt is the time step of the random walk, and R(t) is a uniformly distributed random number in a given interval. The horizontal diffusion coefficient of microplastics, Kx and Ky can be calculated using the following formulations (Eq. 9.25) (Yoshitake et al., 2023): 4

K x = K y = 0 01L3

9 25

where L [L] is the characteristic dimension of the domain. The vertical turbulent diffusion coefficient, Kz can be calculated as per Eq. (9.26) (Fischer et al., 2021; Iwasaki et al., 2017; Song et al.; 2018). K z = 1 5u∗ kHz

9 26

9.4 Modeling the Fate and Transport of Microplastics in Estuaries

Here, u∗ [LT−1] = 0.00012W10 is the frictional velocity of water, W10 [LT−1] is the wind speed at 10 m above the water surface, k is von Karman constant and is assumed to be 0.4, and Hz [L] is the significant wave height. The region where fresh water and seawater meet, known as a salt wedge or salt front in estuaries plays an important role in microplastic transport. The longitudinal current velo∂s cities in estuaries can be expressed in terms of salinity gradient, , river water discharge, ∂x and the wind-induced shear stress, τw as given in Eq. (9.27) (Diez-Minguito et al., 2020; Talke et al., 2009): u x, z =

gH 3 β ∂s 3QR τw H p p + p + 48ρAv ∂x D 2 Hb R 4ρAv w

9 27

where H [L] and b [L] are the depth and width of the estuary, respectively, Av is the vertical eddy viscosity coefficient, ρwater[ML−3] is the density of freshwater, β [−] is the haline contraction coefficient, and pD, pR, and pw are the polynomial functions given by z pD = 1 − 9ξ2 − 8ξ3, pR = 1 − ξ2, and pw = 1 + 4ξ + 3ξ2, ξ = accounts for the vertical H structure of density-driven, river, and wind-induced flow, τw [ML−1 T−2] is shear induced by the wind given by τw = ρaCDauau10, CDa is the air–water drag coefficient, u10 [LT−1] is the wind velocity vector, and ua [LT−1] is an along-channel velocity component. Figure 9.8 shows the effect of along-channel wind velocities, ua and the salinity gradient, ∂S −L on the transport of microplastics, as observed by Diez-Minguito et al. (2020). ∂x ∂S vary between 0.2 and 3 Diez-Minguito et al. (2020) reported that salinity gradient − L ∂x Practical Salinity Units (PSU) and wind velocities ua ranged from 5 to 15 m/s. Though microplastics get trapped at the estuary head at high wind velocities and low-density gradients, they get flushed out to the sea at low velocities and high-density gradients (Figure 9.7). However, microplastics may get trapped in the middle region at the bottom of estuaries for intermediate values of velocity and density gradient (Figure 9.7). The presence of fine sediments in estuarine turbidity zones affects the sedimentation and flocculation of high-density microplastics such as PVC (Shiravani et al., 2023) and it is dependent on sediment concentration. The effect of fine sediments on microplastic settling depends on sediment concentration. There are five zones of microplastic-sediment interaction based on sediment concentration as shown in Figure 9.8. The inert zone is defined as the zone of low sediment concentration where the effect of sediment on microplastics can be ignored. The sediment affects the settling velocity of microplastics in the transition zone. In the flocculation zone, microplastics with settling velocity lower than that of fine sediments get captured due to sediment flocculation, followed by settling with the fine sediment. All the available microplastics are captured by fine sediments and settle in the hindered settling zone due to the large sediment concentration. The settled microplastics along with the sediments get deposited on the sediment bed in the consolidated zone. Shiravani et al. (2023) adopted a hydro-morphodynamic estuarine model coupled with a microplastic transport model to understand the microplastic and fine sediment interaction and the microplastic transport in estuaries. The settling velocity, wS [LT−1] can be expressed as a function of the flocculation factor as presented by Eq. (9.28) (Shen et al., 2022) wfs = ws F s

9 28

227

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

Figure 9.7 Concentration of Microplastics at the Surface (a–c) and Bottom (d–f ) of Ria de Vigo Estuary as a Function of Along-Channel Wind Velocities, u_a and the Salinity Gradient, −L ∂S/∂x for different shapes of microplastics (Source: Reprinted from Diez-Minguito et al. (2020), copyright 2020, permission obtained from Elsevier)

Ws (m/d) of MP-Sediment

104 INERT ZONE

TRANSITION ZONE

FLOCCULATION ZONE

103

HINDERED CONSOLIDSETTLING ATING ZONE ZONE

102 MP-Ws (m/d)

228

101 100

10–1 10–2 10–3 10–3

10–2

C1 = 10–1

C2 = 100

C3101

C4 102

Sediment-Con.(kg/m3)

Figure 9.8 Zones of Microplastic–Sediment Interaction Based on Sediment Concentration. The Solid Black Line Represents the Settling Velocity of the Fine Sediment. The Upper Solid and Dashed Lines Represent the Settling Velocity of the Microplastics with Lower Settling Velocities than the Flocculated Sediment. The Lower Dashed-Dotted and Dotted Lines Represent the Settling Velocity of Microplastics with Greater Settling Velocities than the Flocculated Sediment (Shiravani et al., 2023)

9.4 Modeling the Fate and Transport of Microplastics in Estuaries

Here, wfs [LT−1] is the settling velocity due to flocculation, and Fs is the flocculation factor and depends on the critical sediment concentration for flocculation cf [ML−3], hindering critical sediment concentration, ch[ML−3], and total sediment concentration, ctotal [ML−3]. The flocculation factor can be calculated as per Eq. (9.29) (Shen et al., 2022; Shiravani et al., 2023)

Fs =

1; ctotal ≤ cf ctotal 1+ −1 ; cf cf < ctotal < ch ch − 1 ; ctotal ≥ ch 1+ cf

9 29

Here, is the gradient coefficient. Shiravani et al. (2023) reported that the settling velocity for microplastics with densities 1.04–1.18 g/cm3 ranged from 0.0027 to 0.0104 mm/s. The settled microplastics can get resuspended due to high current velocities and are influenced by the critical bed shear stress. The resuspension flux of microplastics in the estuarine waters, Fres [ML−2 T−1] can be expressed as a function of critical bed shear stress, τcr [ML−1 T−2] and it is given as per Eq. (9.30) (Shiravani et al., 2023; Wu et al., 2018)

F res =

ws cα τ α= − 1 if τ > τcr τcr α = 0 if τ ≤ τcr

9 30

Here, α [−] is the microplastic sedimentation probability function. The resuspension velocity of the microplastics is wres = wsα. The particle tracking simulation results of Shen et al. (2022) showed that the suspended microplastics in the Yangtze Estuary, China are likely to disperse in the flood and may travel to the adjacent sea areas due to warm currents. They also found that the hot spots of microplastic accumulation were mainly located at estuarine turbidity maximum and salt wedge due to energy dissipation of ebb and flow and the confluence of fresh water and salt water that acts as a barrier for the movement of microplastics (Defontaine et al., 2020; Shen et al., 2022). Moreover, microplastics were found to follow a straight-line path in the estuary region and a spiraled clockwise path in the adjacent sea region due to water movement in the clockwise direction in the sea. Shiravani et al. (2023) found from the hydrodynamic modeling of the Wesser River, Germany, which discharges into the southern North Sea, that the denser polycarbonate microplastics settle faster than the PP microplastics in the estuarine sediments. However, the negatively buoyant PP microplastics easily moved into the open sea from the estuary. The 2D modeling observations of Diez-Minguito et al. (2020) on the Ria de Vigo estuary, Spain, showed that microplastic transport is mainly governed by the changes in density and wind velocities for shallow water depths, and the effect of river flow effect is negligible. The effects of windinduced currents are greater at a layer thickness of 3–5 m below the water surface. Further, biofilm growth is greater in marine environments than in estuarine environments due to lower water temperature and light availability in the estuaries (Kaiser et al., 2017). In conclusion, the transport of microplastics in estuaries is dominated by salinity gradient, sediment concentration in the estuarine turbidity zone, and the wind velocity direction. The Table 9.3 lists the various modeling studies on the transport of microplastics in estuarine environments.

229

Table 9.3 Modeling Studies on the Transport of Microplastics in Estuarine Environment Parameters

Site location

Diffusion coefficient (m2/s)

Wind velocity, u (m/s)

Settling velocity, ws (mm/s)

Reference

Processes model

Model name

DiezMinguito et al. (2020)

Sinking and vertical circulation

particle tracking model, twodimensional hydrodynamic model

Ria de Vigo, Brazil

NA

5 to 15

0.2 to 1.3 × 10−6

Modeling results from a prototype coastal upwelling environment revealed that wind and gravitational circulation dominate the microplastic movement in the outer part and near the head of the estuary, respectively

Defontaine et al. (2020)

Advection, diffusion, aggregation

TELEMAC-3D

Adour estuary, France

NA

NA

4 to 127

Vertical distribution of microplastics was highly dependent on particle characteristics and hydrodynamics. Lighter particles were easily flushed out, while heavier microplastics got entrapped in the estuary during low discharge conditions

Shen et al. (2022)

Biofouling and flocculation due to sediment

Lagrangian tracking model

Yangtze Estuary, China

NA

NA

1

The transport of polyethylene was more susceptible to surface currents, poly vinyl chloride was transported with sediment flocculation, and polypropylene settled continuously. Moreover, about 57–90% of microplastics are either settled or beached in the estuary

Shiravani et al. (2023)

Settling, resuspension, and flocculation due to sediment

Delft3D-FLOW, FSK-MPTM

Weser Estuary, Germany

NA

NA

10−4 to 10−6

The model results from the estuary discharging into the North Sea showed that higher microplastic concentrations were present in estuarine turbidity zones, but the lighter microplastics can easily migrate to the sea

Major findings

9.5 Modeling the Fate and Transport of Microplastics in Marine Environment

9.5 Modeling the Fate and Transport of Microplastics in Marine Environment The major sources of microplastics in the marine environment are river mouths, coastal landfills, and tourist, fishing and shipping activities (Cunningham et al., 2022; Dowarah & Devipriya, 2019; Isobe et al., 2014; Montarsolo et al., 2018; Osorio et al., 2021; Peng et al., 2021; Ronda et al., 2023; Tamburri et al., 2022; Upadhayay & Bajpai, 2021). The various processes involved in the transport of microplastics in marine environments are advection, dispersion, biofouling, settling, resuspension, and degradation. Table 9.4 lists the modeling studies on the transport of microplastics in marine environments. Most of the studies have adopted the Lagrangian approach to simulate the movement of microplastics in marine ecosystems (Critchell et al., 2015; Critchell and Lambrechts, 2016; Isobe et al., 2014). The general equation for the transport of microplastics using the random walk particle tracking model is given by Eqs. (9.31) through (9.33). x t + Δt = x t + uΔt + R t

2K x Δt

9 31

y t + Δt = y t + vΔt + R t

2K y Δt

9 32

z t + Δt = z t + wΔt − ws Δt + R t

2K z Δt

9 33

The velocity of the particles can be calculated as per Eqs. (9.34) through (9.36) (Critchell et al., 2015) u = uwater + ψuwind

9 34

v = vwater + ψvwind

9 35

w = wwater + ψwwind

9 36

where, uwater [LT−1], vwater [LT−1], and wwater [LT−1] are the flow velocities of water in x an y directions, respectively, ψ [−] is the wind drift coefficient, and uwind [LT−1] and vwind [LT−1] are wind velocities in x and y directions, respectively, for the particular time step obtained from the field data. The wind drift coefficient represents the percentage of wind that influences particle movement and usually varies between 1 and 5% (Critchell & Lambrechts, 2016; Critchell et al., 2015). Microplastics spreading is known to increase with increasing wind drift coefficient (Critchell et al., 2015). As the effect of wind is negligible for submerged microplastics, the effect of wind velocity on particle velocity in z direction can be neglected; i.e., w = wc (Zhang, 2017). Jalan-Rojas et al. (2019) proposed another formulation to calculate the particle velocity field in terms of current velocities (uc, vc, and wc) and wind velocities (uwater, vwater) as given in Eq. 9.37 and 9.38. uc + uwater u= 1+

ρair Sabove × ρwater Sbelow

ρair Sabove × ρwater Sbelow

9 37

231

Table 9.4

Modeling Studies on the Transport of Microplastics in the Marine Environment Parameters

Reference

Isobe et al. (2014)

Critchell et al. (2015)

Modeled processes

Degradation, beaching, and drifting Wind velocities, diffusion, and sinking

Site location

Diffusion coefficient (m2/s)

Wind drift coefficient [−]

Settling velocity (mm/s)

Degradation rate (%)

Lagrangian particle-tracking model

Seto Inland Sea, Japan

Kx = Ky = 4000, Kz = 0.01

NA

NA

1–5

Near-shore trapping of plastics and the plastic particles free from near-shore trapping spread offshore in coastal waters

SLIM hydrodynamic model

Great Barrier Reef, Australia

Kz = 10

0.01–0.05

NA

NA

Beach orientation toward the prevailing winds affected the accumulation rate of debris. Wind drift coefficient and the release time of debris affected the debris originating from ships

Type of model

Major findings

Iwasaki et al. (2017)

Drifting, diffusion, and sinking

Lagrangian particle-tracking model

Tsushima Strait, Japan

NA

NA

5–70

NA

Stokes drift influenced the movement of micro and mesoplastics out to the sea area by reducing the transit times of the modeled particles

Kooi et al. (2017)

Settling due to biofilm growth

Process-based model

North Atlantic Ocean, Iceland

NA

NA

10−3 to 1.04

NA

Vertical transport of microplastics (float, sink, or vertical oscillation) depends on the size and density of the particle, and maximum microplastic concentrations were present at intermediate depths and minimum at the ocean surface

Jalan-Rojas et al. (2019)

Beaching, mixing, biofouling, degradation, and sinking

TrackMPD

Jervis Bay, Australia

K x = Ky = 1 to 10 Kz = 10−4 to 10−5

NA

NA

0.1–30

The movement of microplastic debris is mainly affected by the plastic density, biofilm density and thickness, turbulent dispersion, and washing off

Van Melkebeke et al. (2020)

Biofouling, settling

2D coupled benthic-pelagic vertical transport model (2DBP)

NA

NA

NA

18–152

NA

Particle shape was found to strongly impact the sinking behavior of microplastics. Biofouling altered the polarity of microplastics, making them more favourable to get trapped in the sediment.

Kreczak et al. (2021)

Biofouling, settling

3D general ocean circulation models (OGCMs)

NA

NA

NA

NA

NA

Algal biofouling led to the entrapment of microplastics in the subsurface layer and determine the depth to which microplastics reach. The smallest particles are found to be sensitive to algal attachment and get trapped in the algal colonies of the euphotic zone

9.5 Modeling the Fate and Transport of Microplastics in Marine Environment

vc + vwater v= 1+

ρair Sabove × ρwater Sbelow

9 38

ρair Sabove × ρwater Sbelow

Sabove Sbelow is the ratio of dry and wet cross-sectional areas of microplastics. The current and wind velocities data can be obtained from ocean general circulation models (Mountford & Morales Maqueda, 2019; Nooteboom et al., 2020). The effect of wind on the particle velocity field needs to be accounted only for low-density microplastics that have large buoyancy; e.g., PP, foamed PS, and PE particles (Critchell & Lambretchs, 2016; Khatmullina & Chubarenko, 2019). The diffusivity coefficients Kx [L2T−1], Ky [L2T−1], and Kz [L2T−1] can be calculated as explained in Section 9.4. The diffusion coefficient (both horizontal and vertical) of microplastics in marine environments is in the range of 1–20 m2/s (Critchell & Lambrechts, 2016; Fischer et al., 2021; Pilechi et al., 2022). The settling velocity of microplastics can be calculated using Stokes law as per Eq. (9.39) (Kooi et al., 2017; Murawski et al., 2022). Here, ρair [ML−3] and ρwater [ML−3] are the air and water densities, respectively, and

ws =

2 ρparticle − ρwater 2 gR η 9

9 39

where, ρparticle [ML−3] is the density of microplastics, η [ML−1 T−1] is the viscosity of seawater, g [M−1L3T−2] is the acceleration due to gravity, and R [L] is the radius of microplastics. Further, Kooi et al. (2017), Isobe et al. (2014), Zhiyao et al. (2008), and Katmullina & Isachinko (2017) have given modified expressions for the settling velocity of particles based on various shapes of microplastics. The average settling velocity of microplastics in marine systems ranges between 1 and 130 mm/s (Khatmullina & Isachenko, 2017; Zhiyao et al., 2008). The density of microplastics in seawater can be different from that of pristine microplastics due to biofouling, degradation, and aggregation. The settling velocities of microplastics due to biofilm formation were reported to be in the range of 10−3 to 1.04 mm/s (Kooi et al., 2017; Kreczack et al., 2021). The change in the settling velocity of microplastics due to the formation of biofilm on its surface was studied by Kooi et al. (2017), Van Melkebeke et al. (2020), and Kreczak et al. (2021). The modified settling velocity of microplastics due to biofilm growth on its surface can be calculated using Eq. (9.40). ws =

2 ρparticle − ρwater 2 gR η 9

9 40

where, ρparticle [ML−3] is the density of microplastics with biofilm. The density of microplastics depends on the thickness of the biofilm and can be calculated as per Eq. (9.41). ρparticle =

R3 ρparticle +

R + t bf R + t bf

3

3

− R3 ρbf

9 41

Here, tbf [L] is the biofilm thickness, and ρbf [ML−3] is the biofilm density. The thickness of the biofilm can be calculated as the difference between the radii of biofouled microplastics and pristine microplastics without biofilm, and it is given by Eq. (9.42).

233

234

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

t bf =

V total

3 4π

1 3

−R

9 42

Here, Vtotal[L3] = Vbf + Vparticle is the total volume of microplastics with biofilm, Vbf = (Vbcb)θp [L3] is the volume of the biofilm, Vb [L3] is the volume of algae/bacteria, cb is the number of attached algae/bacteria per unit area, θp [L2] is the surface area of micro4 plastics given by θp = 4πrp2, and V particle L3 = πR3 is the volume of microplastics. The 3 governing equation describing the attached algal/bacterial growth on microplastics is given by Eq. (9.43). ∂cb βcb + μ T, I cb − mcb − Q10 = ∂t θp

T − 20 10

R20 cb

9 43

Here, cb [ML−3] is the attached algal/bacterial concentration obtained by measuring the chlorophyll content, β [L3T−1] is the encounter kernel rate, θp [L2] is the surface area of microplastics, μ(T, I) is the algal/bacterial growth function which depends on temperature, T [K] and light intensity, I [EL−2 T−1], m [−] is the mortality rate constant, Q10 [−] is the coefficient that indicates the respiration rate when the temperature increases by 10 C, and R20 [T−1] is the respiration rate of algae/bacteria at 20 C. The first term on the right-hand side of Eq. (9.43) represents the collision rate of algae/bacteria with microplastics. The second term gives the biofilm growth as a function of temperature and light intensity, and the third and fourth terms account for the mortality and respiration of the algae, respectively. The thickness of the biofilm can also be obtained by solving the following differential equation (Eq. 9.44) (Van Melkebeke et al., 2020): ∂t bf t max − t bf = ∂t Tb

9 44

Here, tmax [L] is the maximum thickness of the biofilm, and Tb [T] is the time required for biofilm growth. The settling velocity due to the degradation of microplastics is given by Eq. (9.45). ws =

2 ρparticle − ρwater gR 2 η 9

9 45

where, R is the change in the radius of microplastics due to degradation, and it is given by Eq. (9.46). R = R 1−

k deg × T 100

9 46

Here, kdeg[T−1] is the percentage of size decrease per day, and T [T] time from the start of degradation to the current time. The modeling simulations of Kooi et al. (2017) showed that the settling onset time and the settling velocity of microplastics increased with an increase in particle size and particle density due to biofouling. For e.g., for the same particle size, high-density PP has a greater settling velocity as compared to low-density PP (Kooi et al., 2017).

9.5 Modeling the Fate and Transport of Microplastics in Marine Environment

Moreover, larger particles of size 10 mm settle faster in a time scale of a few minutes, however, microplastics of size 1 μm will take years to settle (Kooi et al., 2017). Kooi et al. (2017) found from the model simulations that after the initial settling of the biofouled microplastics, the microplastics exhibited oscillatory movements due to the differences in the density of seawater and the plastic particles and variation of light intensity. Kreczak et al. (2021) simulated the vertical profiles of microplastics in oceans and observed algal growth on microplastics in the euphotic zone. However, no growth was observed beyond this zone, resulting in algal death. Hence, microplastic particles resurfaced into the euphotic zone where algae can grow again on plastic particles, thereby exhibiting an oscillatory motion. It is further observed from the simulations that for a euphotic depth of 20 m, the maximum depth traveled by microplastics was 60 m (Kreczak et al., 2021). Van Melkebeke et al. (2020) studied the effect of particle shape due to biofouling on the sinking behavior of microplastics. They observed that a minimum of 18 μm biofilm thickness was required to induce the settling of spherical microplastics of diameter of 20 μm. However, a biofilm thickness of 35 μm was required for film microplastic particles of thickness 40 μm. Hence, the most commonly used assumption of spherically shaped microplastics in models may lead to discrepancies between simulated and experimental results. Particle tracking model simulations performed by Isobe et al. (2014) found that microplastics spread rapidly offshore up to 10 km in one hour after their release from the coast, as shown in Figure 9.9a. Moreover, Stokes drift velocity causes these particles to return to the coast, resulting in a higher drift density of particles at the coast within 24 hr (Figure 9.9b). Figure 9.9 further shows that particles larger than 1 mm were absent in layers deeper than 1 m. Particles larger (showed as bigger dots) than a few millimeters were trapped near the coast and particle size became smaller (showed as smaller dots) in the offshore direction (Figure 9.9). Critchell and Lambretchs (2016) observed from simulations that the spreading of microplastics occurred in the direction of wind currents with a larger concentration at the ocean floor close to the seeding location. Also, the majority of microplastics get beached with the remaining getting advected rapidly away from the coast when the seeding location was at the coast and downwind. However, when the seeding location was at the coast and windward, the buoyant microplastics get beached quickly and the rest were largely suspended in the coastal water near to the source. Jalan-Rojas et al. (2019) integrated the TrackMPD model with an ocean general circulation model to account for the hydrodynamic processes and to obtain the velocity data. The application of this model at Jervis Bay, Australia, for a total period of one month indicated that the sinking process due to changes in size, density, and shape of microplastics has a greater role than the other processes in the overall fate of microplastics in oceans. It can be concluded from the above discussion on microplastic transport modeling that the fate of microplastics in marine environments is greatly influenced by the source location (Critchell & Lambretchs, 2016), physical processes such as beaching and degradation (Isobe et al., 2014; Iwasaki et al., 2017; Song et al., 2018), and biological processes such as biofouling (Kooi et al., 2017; Kaiser et al., 2017).

235

236

9 Modeling the Fate and Transport of Microplastics in Various Aquatic Environmental Compartments

0

(a)

2

4

6

8

10

12

14

0.0 0.3

0.1

16

18

km 20

0 m/s

0.5

1.0 5 mm (Huerta Lwanga et al., 2017). However, caution must be exercised in interpreting such findings, as localized contamination may skew results. As research delves deeper into the extent of MPs contamination, attention is shifting towards previously overlooked commodities like seaweed, rice, and even condiments like vinegar. Soil contamination, driven by various anthropogenic activities, presents another avenue for MPs entry into the food chain, with agricultural practices contributing significantly to the problem. The implications of MPs on human health are profound, with studies estimating significant annual MP intake per person. From seafood to honey, sugar, salt, alcoholic beverages, and even the air that we breathe, MPs pervade our daily lives, raising urgent questions about their long-term impact on human health and ecological integrity (Alberghini et al., 2023). In the face of this multifaceted challenge, concerted efforts are required to mitigate MP pollution at its source. From stricter regulations on plastic production and disposal to innovative waste management strategies, addressing this issue requires a multifaceted approach. Only through collective action there is a hope to safeguard both human health and the environment from the pervasive threat of MPs.

11.9 Are Biodegradable Plastics Less Negative Than the Others? Biodegradable plastics (BPs) are intended to decompose more easily in specific situations; however, their effect on the environment is influenced by factors such as the conditions in which they break down, the degree of decomposition, and the availability of suitable waste management systems (Mahmoud et al., 2023). Nevertheless, the process of breaking down these materials may still result in the release of MPs or chemical byproducts into the environment. In this regard, investigation has indicated that BPs can produce a higher quantity

11.10 Biostimulation by Nutrients

of biodegradable MPs compared to conventional plastics. For instance, Wei and coresearcher demonstrated that BPs generates higher MP (up to 11%), surpassing the 3.4% of MPs produced by non-BPs (Wei et al., 2021). Furthermore, the manufacturing of BPs sometimes necessitates energy-intensive procedures and may incorporate the use of additives or chemicals that might likewise have environmental repercussions. The toxic effect of the additives has been well established and had been reviewed extensively (Wang et al., 2022). Apart from the toxicity from additives, the degradation of BP is an intricate biological process that requires specific bacteria and environmental conditions. The absence of these particular variables or niches can hinder the degradation process, resulting in the accumulation of MPs in aquatic or terrestrial ecosystems. For example, a biodegradability test on eight types of BPs polymers was investigated, and the results indicate that none of the BPs were totally biodegradable in real environmental conditions (Nabeoka et al., 2021). Thus, the potential advantages of BPs in reducing plastic waste are contingent upon elements such as the kind of BPs, the degradation process, and the surrounding environmental conditions, which collectively determine their impact on MPs pollution. In order to effectively reduce MPs pollution, it is crucial to consider the complete life cycle of plastics and execute comprehensive waste management methods that encompass both conventional and BPs.

11.10

Biostimulation by Nutrients

Microorganisms are essential in the process of biodegrading plastics, as they use enzymes to break down polymers into smaller molecules. Nevertheless, MPs present in natural habitats frequently do not possess an adequate amount of nutrients to successfully sustain the growth of microorganisms and facilitate the decomposition of plastic (Jain et al., 2023; Tania & Anand, 2023). Biostimulation overcomes this constraint by supplementing extra nutrients to boost microbial activity, hence expediting the breakdown of MPs. Biostimulation, when used on MPs, seeks to enhance the breakdown of these pollutants by stimulating microbial communities that have the ability to metabolize plastic polymers (Wang et al., 2023). Typical nutrients employed for biostimulation encompass carbon sources (such as sugars and organic acids), nitrogen sources (such as ammonium and nitrate), and phosphorus sources (such as phosphate). These nutrients act as a source of energy and materials for microbial metabolism, which helps in the enzymatic decomposition of plastic polymers. For instance, Jang and coresearcher sought to optimize degradation conditions for P. jejuensis by assessing growth rates with different nitrogen sources and carbon substrates (Jang et al., 2023). Notably, ammonium nitrate emerged as the preferred nitrogen source, while 1,4-butanediol exhibited the highest growth rate among carbon sources. Furthermore, similar investigation found that the use of soytone as a nitrogen source enhances plastic biodegradation and suggests that manipulating the nitrogen source could offer a novel approach to augmenting biodegradation (Yu et al., 2022). Research on biostimulation for MP breakdown is now in its nascent phase; however, investigations have demonstrated encouraging outcomes in both controlled laboratory

299

300

11 Interactions of Microplastics with Microbial Communities and the Food Web/Plants

settings and real-world field experiments. Nevertheless, there are still obstacles to overcome, such as the requirement to enhance fertilizer formulations and application techniques in order to achieve the highest possible degrading efficiency while minimizing any potential ecological consequences (Mat Yasin et al., 2022). Furthermore, extensive investigation and progress in this field are crucial for enhancing our comprehension of microbial plastic breakdown mechanisms and enhancing the efficiency of biostimulation as a method for addressing MP pollution.

11.11

Conclusion

The pervasive presence of MPs in environmental ecosystems poses significant threats to microbial communities, food webs, and plant ecosystems. Through intricate pathways, MPs disrupt biogeochemical dynamics, nutrient cycles, and microbial diversity, ultimately impacting the health and vitality of plants and animals. Moreover, MPs contribute to the transmission of toxic additives and hinder photosynthesis, exacerbating environmental stressors. Addressing these challenges requires a comprehensive reassessment of MPs sources and implementation of preventive measures. Strategies to enhance food quality and quantity must consider the combined effects of MPs with other pollutants. Additionally, understanding the risks posed by MPs, exclusively to the human health within these ecosystems, is crucial. This chapter underscores the urgent need for further research to fill knowledge gaps and develop effective prevention and control strategies, thus safeguarding ecological and environmental integrity.

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12 Environmental and Toxicological Effects of Microplastics on Aquatic Ecosystems Jin-Min Li1, Hua-Bin Zhong1, Chih-Ming Kao1, Rao Y. Surampalli2, and Tian C. Zhang3 1

Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 3 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 2

12.1 Background Plastics are made from a variety of polymers, which are derived from the decomposition of carbon-based materials such as petroleum, natural gas, or coal. Due to the advantages of being inexpensive, lightweight, versatile, durable, and resistant to corrosion, plastics have gained wide applications in industrial and daily life, covering areas such as packaging, clothing, transportation, construction, agriculture, and medicine. Since 1950, the plastic industry has experienced rapid development. According to research, global plastic production reached 3.67 billion tons in 2020, and it is projected to soar to 33 billion tons by 2050. The widespread use, improper disposal, and persistence of plastic products pose a global threat to aquatic ecosystems. It is estimated that an average of 1.15–12.7 million tons of plastic waste enters the world’s oceans each year, and by 2050, the weight of ocean plastic will exceed the weight of fish (Elizalde-Velázquez & Gómez-Oliván, 2021; Xia et al., 2024). The widespread use, large-scale production, rapid disposal, and slow degradation of plastics have led to their massive release into aquatic and terrestrial environments, where they can persist for hundreds of years. Rivers serve as the primary conveyance of plastic, transporting 70–80% of plastic waste to oceans worldwide, eventually settling on the seabed (Xu et al., 2020). As persistent materials, plastic particles degrade at a very slow rate once they enter the environment. Furthermore, due to their small size, they are easily ingested by fish or birds and can propagate along the food chain, ultimately posing risks to human health. The majority of plastic waste entering aquatic environments originates from land. These plastic wastes enter water bodies through the following pathways: 1) Street garbage enters waterways through rainwater or wind: Due to improper waste management or inadequate oversight, plastic waste on the streets can easily be carried into waterways by rainwater or wind, eventually reaching the ocean.

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2) Improper or illegal dumping of waste: People casually dispose of household or industrial waste in rivers, lakes, or coastal areas, and the plastic within these wastes also enters water bodies. 3) Improper waste container or vehicle coverage: Improperly covered garbage bins or trucks result in plastic waste scattering, being washed into water bodies by rainwater, or being blown in by the wind. 4) Poor landfill management: If landfills are not effectively managed, the accumulated plastic waste is susceptible to being washed into nearby rivers or lakes by rainwater or wind. 5) Wastewater discharge from plastic manufacturing and processing facilities: Large amounts of plastic wastewater are generated during plastic manufacturing and processing. If this wastewater is not properly treated, it is directly discharged into water bodies, causing plastic pollution. 6) Sewage treatment plant and sewer overflow: Inadequate capacity or malfunctions in sewage treatment plants, or sewer overflows, can result in plastic wastewater entering water bodies. 7) Garbage from recreational and fishing activities: Plastic waste generated during water recreational activities or fishing, if not properly managed, can easily enter water bodies. 8) Improper operation of coastal solid waste treatment facilities: If plastic waste on beaches is not promptly cleared or if treatment facilities are inadequate, it may also enter the ocean. Studies have shown that approximately 80% of the plastic entering the marine environment originates from wastewater discharged into wastewater treatment plants (WWTPs) in terrestrial water bodies. Extensive research has confirmed that plastic fragments dominate marine litter, and the situation of plastic pollution in freshwater environments is becoming increasingly severe. The accumulation of these plastic fragments has exacerbated the issue of MP pollution in the environment. Another significant source of microplastics (MPs) is personal care products, such as toothpaste, shower gel, and soap. These products often contain tiny plastic particles used for exfoliation. In addition, industrial processes, such as sandblasting, also generate MPs. In sandblasting, small plastic particles are used to abrade surfaces. Plastic fragments are one of the fastest-growing sources of pollution in the world today and have become a prominent environmental concern. However, despite the range of sizes of plastic fragments, from tiny particles to the size of rice grains, the focus of public attention is currently on MPs.

12.2

Sources of MPs in Aquatic Environments

MPs, including primary and secondary MPs, ultimately enter aquatic environments through nonpoint source or point source pathways. Wastewater treatment plants (WWTPs) are the most significant point source for the release of MPs into aquatic

12.2 Sources of MPs in Aquatic Environments

environments, as they discharge wastewater containing polymer mixtures from cosmetics, facial scrubs, and textiles. According to Zhou et al. (2023), microbeads in personal care and cosmetic products (PCCPs) are primarily composed of polyethylene (PE), accounting for over 90%, with the remaining including polypropylene (PP), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), and nylon, among other plastic polymers. In a study by Sun et al. (2020), the estimated MPs content in facial cleansers was 0.05 g/g or 2,450 particles/g (geometric mean), while in body wash, it was estimated to be 0.02 g/g or 2.15 particles/g (geometric mean). The global emission of MPs from cosmetic products is estimated to be 1.2 × 104 tons/year. In addition, it is believed that approximately 3.0 × 105 tons of MPs derived from PCCPs have accumulated in the environment over the past 50 years (Sun et al., 2020). In addition, clothing is composed of polyester fibers, nylon, and microfibers, which release MPs during washing. According to Kurniawan et al. (2021), washing separates approximately 124–308 mg/kg of microfibers from clothing during the washing process, with an average length and diameter of 360–660 μm and 12–16 μm, respectively. Up to 1,900 fibers can be released in a single wash (Junaid et al., 2022), mainly due to the agitation of washing water and synthetic textile clothing. Synthetic fibers have also been found in sludge during wastewater treatment processes. Although WWTPs can remove approximately 98% of MPs (Liu et al., 2021b), nonpoint source pollution management faces significant challenges compared to point source pollution, as it is difficult to control noncontinuous pollution inputs and identify specific sources. Management and monitoring of these nonpoint source pathways are crucial to reducing the potential impact of MPs on water environments. Nonpoint source MPs can enter aquatic environments through various pathways, including urban stormwater runoff, agricultural drainage systems, highway runoff, and atmospheric deposition. These nonpoint source pathways carry MPs pollutants to varying degrees and can potentially become major sources of water environment pollution. Urban stormwater runoff may carry MPs from sources such as dust, construction activities, artificial turf, leachate from landfills, and degraded litter. According to Chen et al. (2020a), the annual total discharge of MPs in wet weather (from surface runoff, domestic sewage, and sewer sediments) is nearly six times that of WWTP effluent. Surface runoff in urban and agricultural areas, as well as tire and road debris in highway runoff, are major sources of MPs. Bigalke et al. (2022) reported that Swiss agricultural drainage systems release approximately 9.3 × 1012 MPs particles annually, possibly due to the re-accumulation of MPs in soil from sewage irrigation of surface water and domestic water, or the weathering and breakdown of protective plastic films on farmland that enter water bodies. Sandblasting and industrial abrasion technology are specialized procedures that typically utilize compressed air to generate pneumatic velocity and treat surfaces with abrasive materials through a nozzle. These technologies are commonly used to remove rust, color, and other contaminants on steel surfaces, such as on ships, machinery, engines, and walls. MPs are widely used as a grinding medium and for mold cleaning, including materials such as acrylic acid and polyester. These technologies are widely used in industries such as automotive, aviation, shipping, telecommunications, and manufacturing.

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However, MPs particles typically range in size from 0.2 to 2 mm, making them a major source of MPs pollution (Waldschläger et al., 2020). This problem is particularly acute in ports and docks, where the hulls of large oil tankers can shed paint and untreated wastewater is discharged directly into the marine, exacerbating the problem. Freshwater ecosystems heavily rely on rivers, as they are the main pathway for MPs to flow from land to the marine. Most MPs in the marine come from land, and the transfer between land and sea usually occurs at river estuaries. Marine MPs pollution is also influenced by boating and fishing activities. Plastic polymers are frequently used to make fishing nets, fishing gear, fish cages, and aquaculture containers. These products usually aren’t made with MPs particles in mind, but over time, weathering can cause them to leak into aquatic habitats. The aforementioned items, including discarded or misplaced items in recreational areas, often float as marine debris on the water surface, with fragments of these items generating MPs particles. In addition, the two most prevalent waste materials connected to fishing activities are nylon nets and fiber ropes. Marine MPs also originate from atmospheric deposition, with recent studies indicating significant transport of fibers through atmospheric deposition, particularly in highly urbanized areas. Possible sources of MPs in the air include synthetic fibers from clothing and households, artificial turf, landfills, and waste incineration. These particles in the atmosphere can be transported by wind to aquatic environments or deposited in terrestrial environments. It is noteworthy that since 2018, there has been a significant increase in the number of peer-reviewed studies on MPs in freshwater. The quantity of papers on MPs is rapidly increasing (Figure 12.1a). Figure 12.1b depicts a co-authorship network using the keywords “MPs” and “aquatic ecosystems”. Figure 12.1b presents an overlay visualization map that depicts the research progress in a particular field from 2013 to 2022. The thickness of the lines connecting the keywords represents the strength of their association, while the size of the circles corresponds to the frequency of occurrence of each keyword. The spacing between items also conveys their relative importance within the research landscape. Cluster A1 (Green Zone) primarily focuses on the pollutant characteristics of MPs, including aspects such as transport, degradation, impact, identification, and quantification. Cluster A2 (yellow zone) focuses on the sources of MPs (plastic debris and treatment plants) and their distribution (marine-environment, sediments, surface waters, fresh water). Cluster A3 (Red Zone) examines the interactions between MPs and persistent organic pollutants (such as adsorption) and places emphasis on analyzing the toxicological characteristics of MPs (bioaccumulation, toxicity, and oxidative stress). In summary, the pathways for MPs entering aquatic environments are diverse, requiring comprehensive management and control strategies to minimize damage to aquatic ecosystems. This includes monitoring and tracking the release of MPs, implementing measures to reduce plastic usage and improve waste disposal efficiency, as well as enhancing wastewater treatment and pollution prevention technologies. These measures will help reduce the distribution of MPs in aquatic environments and protect the health of ecosystems.

Figure 12.1 The Analysis Results of Conducting a Bibliometric Analysis Using the Keywords “Microplastics” and “Aquatic Ecosystems” Through the Web of Science Website (from 2013 to 2022). (a) The Number of Published Articles Related to “Microplastics” and “Aquatic Ecosystems.” (b) The Co-occurrence Network of “Microplastics” and “Aquatic Ecosystems”

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12.3 Consumption of MPs by Aquatic Organisms and Increase in Aquatic Leaching Rate Marine particles have a lower amount than freshwater, with seawater containing 0.4–250 μm/L, compared to 30–1,790 micrograms in freshwater (Pratiwi et al., 2023). Aquatic organisms can ingest MPs through active and passive ingestion: Active ingestion occurs due to visual misidentification, chemical similarity, and behavioral habits. Some organisms, like sea turtles, mistake MPs for natural food sources, while others, like small fish or crustaceans, may ingest MPs due to behavioral habits. This can lead to MPs entering the food chain. Similar instances of visual misidentification have been observed in small fish or crustaceans. The study reveals that various fish species, including juvenile fish Girella laevifrons and copepods, prefer ingesting red plastic fibers due to their diet primarily based on grazing red algae (Mizraji et al., 2017). Seriolella violacea, a fish species that feeds on zooplankton, prefers black MPs, which appear more similar to food particles (Ory et al., 2018). Copepods, on the other hand, rely on mechanical contact sensing to locate their prey. They select a specific size range (100–200 μm) of fragments, while other sizes (< 90 and > 500 μm) are not chosen; the color of the particles does not affect their selection (Franzellitti et al., 2019). Protozoa have a unique ability to selectively choose their food by recognizing surface features, which influence food selection and prey size. Microcystis aeruginosa, a predator of 3 μm MPs, can effectively recognize and ingest similar sizes of MPs, reducing grazing efficiency and interfering with the normal grazing of harmful algae (Kong et al., 2021). Passive ingestion: MPs can be passively ingested by aquatic organisms while feeding on other food sources, such as filter-feeding and deposit-feeding fish. These organisms connect trophic levels and ecosystems, potentially serving as a key pathway for MPs transfer. Indirect ingestion occurs when predators eat tainted prey, exposing marine mammals to MPs. A study by Compa et al. (2018) found that at least one MP particle or individual was consumed by every fish sample taken from Spain’s coastal Mediterranean Sea. Fish in Taiwan, for example, contained at least 14 MPs particles (Tien et al., 2020). Fish samples from India’s traditional marketplaces include PP and PE (James et al., 2020), and Malaysia (Karbalaei et al., 2020), also showed exposure to MPs. Omnivorous fish consume more MPs than herbivorous or carnivorous fish due to their wider food sources. Herbivorous and omnivorous fish often mistake drifting MPs for food. Large marine animals like baleen whales ingest MPs while filtering water. Filter-feeding animals and marine mammals also consume MPs due to their feeding behavior. MPs can be expelled through various pathways, but their prolonged residence, especially in larger organisms, is notable. Zebrafish larvae excrete MPs in feces just 5 hr after feeding in high-concentration environments (Cousin et al., 2020). When freshwater snails (Radix balthica) ingested biofilms containing MPs fibers, most of the MPs fibers were excreted through feces within a few days after ingestion. However, further analysis revealed that some ingested fibers remained in the snails’ bodies, particularly after 6 days of exposure (Ehlers et al., 2020). Microspheres ingested by copepod Eurytemora affinis were rapidly excreted within 6 hr of exposure. In shore crabs (Carcinus maenas), the concentration of fluorescent polystyrene (PS) microspheres in hemolymph decreased from 24 hr to 21 days

12.4 Transport of MPs in the Aquatic Trophic Level

after exposure, but a small amount of microspheres remained on the 21st day. In mussels (Mytilus edulis), although MPs were excreted with feces, microbeads could still be detected in the hemolymph 48 days after exposure (Duis & Coors, 2016). The rate of MP leaching depends on the material, shape, and size of the microspheres. PE, PP, and other plastics have a faster leaching rate, while PS, polyester, and other plastics have a slower rate. Smaller MP particles have a faster leaching rate. MPs can reenter water bodies or soil, causing secondary environmental pollution.

12.4 Transport of MPs in the Aquatic Trophic Level The aquatic food web, an intricate network of interdependent species in an aquatic ecosystem, comprises linked food chains elucidating nutrient and energy transfer. Trophic levels include: (a) producers, like algae and phytoplankton, using photosynthesis; (b) primary consumers, e.g., zooplankton, small fish, and crustaceans; (c) secondary consumers, like otters; (d) tertiary consumers; and (e) apex predators, such as large sharks and whales, atop the food chain in the aquatic ecosystem. Decomposers, like fungi and bacteria, comprise the final trophic level, breaking down organic waste to return nutrients to the environment. MPs in the marine ecosystem pose a substantial threat to various organisms, including zooplankton, benthic organisms, fish, and marine mammals. These tiny plastic fragments, easily ingested, accumulate in their digestive systems, tissues, and cells, potentially impeding growth and overall well-being. MPs have been found in different levels of marine animals in the marine food chain. Once MPs are ingested by marine animals, they can cause various toxic effects, including behavioral, reproductive, stress, genetic and hereditary effects, and complex effects. MPs can transfer between trophic levels from herbivores to carnivores in the food chain, which means that MPs can accumulate and magnify along the food chain (Wu et al., 2023a). Considering the crucial role of phytoplankton in the aquatic food web, the toxicity of MPs to phytoplankton is influenced by various factors, including particle size, polymer type, MPs concentration, exposure time, and target species (Mao et al., 2018; Wang et al., 2019). Research efforts have primarily concentrated on elucidating the growth dynamics of phytoplankton subsequent to exposure to MPs. MPs exposure can significantly inhibit the growth of phytoplankton, and the inhibitory effect tends to increase with increasing exposure dose. However, the adverse effects on algal growth seem to diminish with increasing MPs particle size. PS nanoparticles have been shown to transfer from algae (Scenedesmus sp.) to zooplankton (Daphnia magna) and then to fish (Carassius carassius) in an artificial aquatic food chain. Similarly, the phenomenon of trophic transfer of MPs has been observed between mussels and crabs (C. maenas), resulting in the translocation of these micro-sized particles in the crab’s hemolymph and tissues (Wang et al., 2019). The fate of MPs in aquatic animals after ingestion is influenced by their size and shape. They may remain in the animal’s gut or even transfer to other tissues. For instance, MPs measuring 5 μm in diameter exhibit the ability to translocate to the liver of zebrafish and the hepatopancreas of the Chinese mitten crab (Eriocheir sinensis), while those with a diameter of 20 μm do not demonstrate such transfer to the zebrafish liver. Furthermore,

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in mussels (M. edulis) exposed to MPs with diameters of 3 or 9 μm, MPs were detected in the hemolymph. Notably, a notable efficiency of 100% has been observed in the capacity of most bivalves to capture and retain MPs particles ranging from 3 to 4 μm in diameter, extending to the interception of particles as diminutive as 1 μm in diameter. MPs were also detected in the hemolymph of crabs (C. maenas) fed with MPs. MPs between 124 and 438 μm in diameter have also been discovered in the liver of wild anchovy, and comparable findings have also been reported in the muscles of wild fish and shrimp (Lyu et al., 2020). In a healthy food web, biomass and energy production gradually decrease with each trophic level. On the other hand, the levels of persistent organic pollutants and toxic chemicals like MPs increase with each trophic level. This is because organic chemicals can accumulate in the fatty tissues of animals, while MPs have been found to accumulate in the intestines, gills, liver, and brain of fish (Kibria et al., 2022). After ingestion, toxic chemicals and MPs can transfer from one trophic level to another, leading to bioaccumulation in the food web. Observations on MPs ingestion trends indicate that omnivorous fish (such as Girella laevifrons) have higher levels of MPs fiber ingestion compared to herbivores and carnivores. The average MPs unit (MPU) is 61 in omnivorous fish, 14 in herbivores and 10 in carnivores (Mizraji et al., 2017). The higher abundance of MPs fibers observed in omnivorous fish may be attributed to their (a) feeding habits, as omnivorous animals may ingest MPs from sediments and surfaces of plants, including red algae and invertebrate species (Rasta et al., 2020), and (b) relatively longer intestines compared to carnivores, allowing MPs to reside in the stomach for a longer period (Kibria et al., 2022). Studies show a clear trend of MP accumulation through food webs. Ribeiro et al. (2020) observed decreasing MP concentrations from sardines to crabs and prawns to oysters and squid, implying potential biomagnification. Similarly, Goswami et al. (2020) documented MP numbers increasing as finfish consumed zooplankton. MPs are found throughout marine environments. Md Amin et al. (2020) detected them in surface seawater and zooplankton across Malaysia’s East Coast, averaging 3.3 particles/L. Saley et al. (2019) even found biomagnification of MPs in algae and a target species, with concentrations rising over four-fold. Determining MP ingestion pathways in nature is challenging, involving both direct and indirect ingestion through trophic transfer. Laboratory experiments are crucial to understand these dynamics. Setälä et al. (2014) demonstrated MP transfer from mesozooplankton to amphipods using fluorescent particles. Farrell and Nelson (2013) observed substantial MP uptake in crabs fed MP-laden mussels, highlighting indirect trophic transfer. Lyu et al. (2020) found MPs in mackerel and the feces of captive grey seals fed on them, confirming MP transfer through seafood consumption. Considering seafood as a major protein source, humans are likely exposed to MPs through this pathway, with the extent depending on individual seafood consumption.

12.5

Occurrence of MPs in Aquatic Ecosystems

Nearly, all aquatic environments are subject to contamination by MPs, including rivers, lakes, and oceans (Figure 12.2). The marine ocean is considered the ultimate sink for global plastics. Plastic waste can be transported from land to marine aquatic environments through wind, runoff, or during rainfall, especially during monsoon seasons. About 80%

12.5 Occurrence of MPs in Aquatic Ecosystems

Figure 12.2

Sources of Microplastics in Aquatic Environments

of plastic and MPs in the global marine environment originate from land (Mohan & Lakshmanan, 2023). Fisheries are among the largest contributors, using various fishing and storage equipment. The loss of fishing nets is particularly concerning as they often entangle with organisms and accumulate on the seabed. In addition, the marine environment is also contaminated with MPs from various sources, including fishing gear and plastic litter discarded near coastlines. Plastic items may unintentionally leak during port, harbor, and maritime transport processes. Furthermore, paint on ships and coastal structures undergoes weathering and gradual degradation, directly impacting the marine environment. Plastic waste can remain buoyant on the water surface, sink below the water surface, or deposit in deep-sea sediments. Common types of plastic particles found in aquatic environments include PS foam, films, fibers, fragments, and pellets, with PE, PP, and PS being the most common plastic polymers in water. After MPs enter the marine ecosystem, considering their structure and composition, they have been found in various invertebrate and vertebrate species, leading to multiple toxic effects, which have raised significant global concerns. It is estimated that the marine environment has accumulated over 1.5 billion metric tons of plastic waste. Even in sparsely populated marine protected areas (MPAs), such as the Spitsbergen Wildlife Sanctuary in Australia, the Chinhoyi Islands in Spain, and the Pinnacles Sanctuary in the United States (Bai et al., 2022; Nunes et al., 2023), the prevention of MP pollution remains challenging. Since Thompson’s discovery of MPs in 2004, the marine

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has been the focus of MPs research (Thompson et al., 2004). Some scholars argue that rainfall and storm events are the primary causes of MPs in the ocean (Ben-David et al., 2021; Hitchcock, 2020). MPs in the ocean are influenced by seasonal variations, with winter land runoff affecting particle and fiber abundance. Upstream areas show higher MP abundance during storms, while downstream areas show higher abundance after a few days. Recently, there has been a shift in focus towards freshwater systems, specifically river systems, to trace the origins of marine MPs. River systems play a crucial role in the land-marine transfer of MPs as an important component of the global water cycle (Bai et al., 2022). Lebreton et al. (2017) estimated that 1.15–2.41 million tons of plastic waste enter the marine from rivers each year. In China, 16–20 trillion MPs particles (equivalent to 537.60–905.90 tons) entered the East China Sea via the surface water of the Yangtze River in 2017 (Zhao et al., 2019). In Korea, 5.40–11.00 trillion MPs particles (equivalent to 53.30–118.00 tons) were discharged into the marine from the Nakdong River in 2017 (Eo et al., 2019). The contamination of river sediments with MPs poses a significant threat to the stability of the aquatic ecosystem, resulting in a decrease in environmental carrying capacity, loss of biodiversity, and degradation of ecological function. MPs, which can be categorized into regular and irregular forms, are widely found in river sediments worldwide. Their shape, influenced by factors like initial shape, aging, and weathering, affects the fluid dynamics of MPs in water, affecting their distribution and degradation in biological systems. The settling velocity of MPs is indirectly affected by variations in shape and density. For example, fibers and films have higher buoyancy and lower settling velocities than spherical particles. As the predation process of aquatic organisms is typically dynamic, changes in the settling behavior and ultimate fate of MPs can affect the opportunities for biological uptake and utilization (Elizalde-Velázquez & Gómez-Oliván, 2021). After entering the water body, the fate and transport of MPs in rivers are driven by several fundamental processes. These processes include advection, dispersion, suspension, and settling. Advection refers to the downstream transport of MPs with the flow velocity of the river. Dispersion refers to the spreading of MPs in the water column, i.e., the diffusion from high-concentration areas to low-concentration areas. The density of MPs affects their settling and suspension in water. MPs with higher density tend to settle and deposit at the riverbed, while those with lower density remain suspended in the water. Riverbed erosion can resuspend the MPs deposited at the riverbed back into the water (Atugoda et al., 2022). Spherical MPs are more prone to migration within sediment matrices than irregularly shaped MPs. Smaller-sized MPs tend to exhibit a more spherical shape, and hydrodynamic conditions in rivers during the rainy season are stronger than those during the dry season, contributing to their vertical transport. The size and shape of MPs play a crucial role in this process, with smaller and more spherical particles exhibiting greater susceptibility to vertical transport. MPs can aggregate or form fragments in riverine systems, with their buoyancy, neutrality, or sinking behavior depending on their composition, density, and shape. Turbulence and storm events can lead to the resuspension of high-density MPs and their redistribution within the water column. Adsorption of biological fouling and clay minerals can increase the density and weight of MPs particles, causing them to sink into the open ocean or seabed. River sediments are often considered the primary sink for MPs within river systems. The abundance of MPs in the marine is lower than in surface water, with MPs suspended in

12.6 Effects of MPs on Freshwater Ecosystems

water slowly settling daily. The distribution of MPs in the marine involves both horizontal and vertical distribution. Tidal and wind-driven currents are the main causes of horizontal migration, while marine currents play a crucial role in horizontal transport. In the vertical aspect, the density of MPs is the main factor affecting water distribution. The tourism industry has led to a rise in plastic waste in aquatic environments, including rivers, lakes, coastlines, beaches, and marine areas. Tourists’ plastic products, such as bags, water bottles, and food packaging, are often abandoned and broken down into MPs by sunlight, temperature changes, and freshwater/saltwater erosion.

12.6 Effects of MPs on Freshwater Ecosystems Distribution of MPs in aquatic environments is influenced by a variety of factors, including improper disposal of plastic fragments and their transport via the atmosphere or runoff. Currently, research on MPs pollution in freshwater systems is primarily focused on rivers and lakes, with a focus on the status of MPs in surface water, sediments, and organisms. Specifically, MPs from residential areas and industrial zones are transported to aquatic systems through runoff, and they may also enter rivers and lakes via surface runoff and atmospheric deposition. It is worth noting that freshwater environments near tourist destinations are particularly affected by MPs pollution. Compared to rivers, stagnant water bodies such as lakes may accumulate more MPs. Although WWTPs can remove most MPs, a small fraction of MPs can still enter rivers with treated water, meaning that MPs are still released into the natural environment in the discharged water. In remote areas, another important source of MPs in freshwater is atmospheric transport and deposition (wet deposition) (Yang et al., 2021). Rainfall not only transports MPs from the atmosphere to rivers and lakes (especially during heavy rains) but also leads to the formation of surface runoff, which carries MPs into the soil or urban wetlands, thereby enriching MPs in the soil. These processes jointly introduce MPs into freshwater environments, further emphasizing the multisource nature of MPs pollution. Unmanaged plastic waste, including municipal waste and agricultural plastic (such as mulch and woven bags), is often found scattered on roads, riverbanks, fields, or other uncontrolled landfills. Heavy rains help to transport plastic waste through stormwater runoff into freshwater systems. In addition, the main polymer components of MPs in freshwater have been identified as PE, PP, PS, and PET, which are widely used in agricultural films, packaging films, injection molded consumer products, and high-performance products. Since MPs in freshwater eventually enter the marine environment, they are worth further research and monitoring. Previous studies have shown that MPs have negative effects on aquatic organisms, such as feeding disruption, energy expenditure, increased immune response, endocrine disruption, reduced reproductive capacity, sex development, gastrointestinal obstruction, food intake insufficiency, respiratory distress, and tissue damage. MPs in freshwater eventually enter the marine environment, making them a subject worthy of further research and monitoring. MPs may have negative impacts on aquatic organisms, including disruption of feeding behavior, increased energy expenditure, heightened immune response, interference with endocrine systems, reduced reproductive capacity, effects on gender development, gastrointestinal blockage, inadequate food intake, respiratory difficulties, and tissue damage.

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12.6.1 Effects/Ecotoxicity of MPs in Freshwater Biota (Micro and Macro Organisms) Chaudhary et al. (2022) revealed several important findings. First, the alpha diversity of fungal communities significantly changed over time on various substrate types, particularly between day 3 and day 10. This change contrasted sharply with the lack of change in bacterial and algal communities during the same period. The decrease in alpha diversity in the fungal community on day 10 was accompanied by a decrease in the proportion of various fungal genera, including Aureobasidium, Taphrina, and uncategorized Pseudeurotiaceae and Basidiomycota. These results suggest more turnover of fungal settlers between the early and late stages. Secondly, Actinobacteria were widely present in freshwater microbial communities, both in the planktonic and sedimentary zones. However, Actinobacteria in these two environments had different genomes and metabolic characteristics. Planktonic Actinobacteria with high relative abundance typically had a smaller size, simplified genomes, and slower growth rates. In contrast, sediment-dwelling Actinobacteria had larger genomes and diverse metabolic capabilities. Interestingly, in freshwater, the relative abundance of Actinobacteria in PE films and biofilms associated with MPs was higher than in PP films. Therefore, the researchers speculated that Actinobacteria enriched on PE substrates may be diverse metabolizers capable of utilizing complex organic matter, similar to Actinobacteria in sediment and soil ecosystems. This suggests that plastic substrates may have selective effects on specific microbial communities. Algae play a crucial role in global biogeochemical cycles and in maintaining ecological stability. As the most significant primary producers in aquatic ecosystems, algae sit at the base of the aquatic food chain, and their alterations eventually impact the composition and functionality of aquatic ecosystems. Moreover, algae have a short growth cycle, are easy to manipulate and observe, are sensitive to toxic substances, and do not require ingestion processes, making them the best choice for detecting threats posed by MPs pollution to freshwater environments. Therefore, algae are used as one of the biological indicators and play a crucial role in monitoring and assessing water quality in aquatic ecosystems. MPs, particularly nanoplastics, can have toxic effects on microalgae, with size and dosedependent impacts. Exposure to PS MPs with sizes of 0.1 and 0.55 μm has been found to have dose-dependent toxic effects on Chlorella pyrenoidosa and Microcystis aeruginosa, causing severe algal blooms in freshwater ecosystems (Li et al., 2022b; Mao et al., 2018). Studies have shown that 1 μm PS MPs have more adverse effects on M. aeruginosa than 100 nm MPs, but within 96 hr, 1 μm MPs could promote algal growth. MPs can alter multiple cellular metabolic processes in M. aeruginosa at the molecular level, such as reducing carbohydrate metabolism, downregulating gene expression, and upregulating gene expression (Wu et al., 2021; Zheng et al., 2021; Zhou et al., 2021). M. aeruginosa, a cyanobacterium, is an important primary producer in aquatic environments, and its growth and metabolism significantly impact aquatic ecosystem structure and function. MPs pollution may exert toxic effects on M. aeruginosa, inhibiting its growth, metabolism, and reproduction (Ye et al., 2022). High concentrations of MPs can cause oxidative stress in M. aeruginosa, leading to increased superoxide dismutase (SOD) activity. This damage is caused by an imbalance between reactive oxygen species (ROS) and the antioxidant system (Cunha et al., 2019; Wu et al., 2019).

12.6 Effects of MPs on Freshwater Ecosystems

MPs pollution can also inhibit the secretion of extracellular polymeric substances (EPS), an essential component of the cell wall that protects cells from environmental stress and regulates metabolism. MPs pollution may interfere with the synthesis of EPS, which has strong antioxidant capabilities and can scavenge ROS, weakening its stress resistance and growth capacity (Song et al., 2023). The bioaccumulation of MPs in aquatic food chains is inevitable, affecting algae, zooplankton, and fish. Proteobacteria and Bacteroidota may improve the metabolic potential of nitrogen-containing substances (Rong et al., 2021), while Chloroflexi can break down organic contaminants, reducing dissolved organic matter in sediments (Huang et al., 2019). PS and PET can affect microbial communities, with an increase in Proteobacteria and Nitrospirae and a decrease in Chloroflexi. PS and PET may impact nitrogen removal, as Chloroflexi only participates in the denitrification and decomposition of sugars. However, their effect on nitrifying microorganisms is relatively small Wu et al. (2023b). Snails, filter-feeding animals, can accumulate particles with high contaminant tendencies and can become carriers of environmental pollutants. A study on Pomacea paludosa (snails) in freshwater environments assessed the toxicity of MPs. The study found that MPs cause oxidative stress, damage to the digestive system, and severe damage to the liver and pancreas tissues. Exposure to MPs reduces the activity of digestive enzymes, affecting the snail’s ability to digest and absorb carbohydrates, proteins, and lipids. Histological changes, such as cell destruction and vascular dislodgement, indicate that the toxic effects of MPs on snails are irreversible (Jeyavani et al., 2022). Studies have shown that PS microspheres do not significantly impact the mortality rate, hatching success rate, or deformities of zebrafish (Pitt et al., 2018). However, zebrafish embryos exposed to PS nanoplastics only exhibited bradycardia and reduced activity. Current research suggests that MPs localize inside cells and do not bind to membranes, which may interact with the cardiac myocyte and lead to abnormal heart rates. Future studies are needed to determine the mechanism by which MPs decrease heart rate. Similar results have been found in marine Oryzias melastigma, where MPs significantly reduced embryo heart rate at 10 days postfertilization (Li et al., 2020a). However, MPs also reduced hatching rates and delayed embryo hatching time. Fish exhibit anorexia and lethargy when ingesting MPs (De Sales-Ribeiro et al., 2020), and MPs can adsorb fish pathogens in untreated urban wastewater (Lai et al., 2022). These findings confirm that MPs carried by fish pose a threat to human health and other aquatic organisms (Li et al., 2022b). MPs can significantly impact organisms’ behavior, including locomotion, anti-predator behavior, and burrowing behavior, potentially impacting their survival and reproduction. Studies have shown that zebrafish, Physalaemus cuvieri, and bivalves have exhibited changes in behavior after exposure to MPs (Chen et al., 2020b; Urban-Malinga et al., 2021). These changes can be attributed to particle stimulation, upregulation of estrogen levels, and oxidative damage to the body. The antioxidant defense system of organisms can help resist the damage caused by MPs, reducing their impact on behavior. Large invertebrates are crucial components of aquatic ecosystems, playing a role in water purification, food chain transfer, and material cycling (Fu et al., 2022). Assessing the impact of MPs on organisms, especially freshwater large invertebrates, is of great significance for both organisms and ecosystems. Therefore, sufficient attention should be given to the antioxidant defense system of organisms to reduce their impact on behavior.

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12.6.2

Effects on Different Developmental Stages of Invertebrates

This chapter examines the impact of MPs on invertebrates, specifically eggs and larvae, and their growth, survival, and development. MPs play a crucial role in freshwater ecosystems, and Daphnia magna, a common water flea, is a key consumer in the food web. Larvae are more sensitive to ROS generated by MPs, while adults are more resistant. Larger-sized MPs cause greater oxidative stress in adults, leading to increased intracellular ROS in larvae but no increase in antioxidant enzyme activity. This suggests that larvae may use nonenzymatic mechanisms to counteract the effects of ROS. In contrast, adults can counteract ROS effects by increasing antioxidant enzyme activity. These findings suggest that MPs may have negative impacts on aquatic organisms’ health. Larvae are more susceptible to damage due to their increased sensitivity to ROS, while larger-sized MPs cause greater oxidative stress in adults, leading to more severe damage (Esterhuizen et al., 2023). MPs also have complex effects on the reproduction and feeding behavior of D. magna. Short-term high concentrations can cause delays in neonate production but later increase in abundance. Long-term exposure leads to a decrease in reproductive capacity, reduced neonatal abundance and size, and increased deformity rates. MPs also affect the feeding behavior of D. magna, making it unable to distinguish between MP and food, leading to increased intake and malnutrition. MP accumulates in the gut, causing blockage of the digestive system and impairing normal food digestion. MP releases toxic substances that damage cells and tissues, leading to D. magna mortality. These studies indicate that MPs have negative effects on D. magna and may have broader implications for ecosystems. Overall, MPs have significant impacts on the health of aquatic organisms and their ability to survive in freshwater ecosystems (Eltemsah & Bøhn, 2019). Researchers (Prata et al., 2023) conducted a 48-hr MPs exposure test on fourth instar Chironomus riparius larvae to evaluate the toxic effects of MPs. The results showed that the presence of MPs triggers the larvae’s immune response, activating the phenoloxidase system (POS). POS is an enzyme system involved in immune defense that can convert phenols to quinones. Quinones can polymerize to form melanin, which is involved in encapsulation, tissue repair, and immune defense. MPs may cause mechanical damage to the intestinal epithelium, protein hydrolysis, and changes in the microbial community, all of which may lead to immune system activation. In addition, MPs also induce the production of antimicrobial peptides and ROS in larvae. ROS are oxidants within cells that can kill bacteria and other microorganisms, but at high concentrations, they can also damage cell tissues. Researchers also found that MPs reduce lipid reserves in larvae. Lipid reserves are an important energy source for larval growth and development. The reduction in lipid reserves may lead to impaired growth and development in larvae. In summary, the toxic mechanisms of MPs on C. riparius mainly include: (a) activation of the immune system; (b) production of ROS; and (c) reduction in lipid reserves. These toxic effects can impair larval growth and development and even lead to death. In addition, MPs can cause various toxic effects on the Chinese mitten crab, including male reproductive dysfunction and transgenerational toxicity (Sun et al., 2022). Specifically, MPs can lead to the following effects: reduced survival rate and heart rate of larvae; impaired quality of male crab testicular germ cells, resulting in hormonal imbalance and subsequently reduced hatching success and survival rate of larvae; altered gene expression

12.7 Effects of MPs in Marine Ecosystems

of steroidogenesis, leading to increased expression of apoptosis-related genes in the gonads. Reduced activity of immune-related enzymes; increased concentration-dependent bioaccumulation of MPs in different tissues of the crab’s offspring. The toxicity of MPs on cells may be caused by excessive production of ROS generated by MPs in aquatic animals (Kang et al., 2021). ROS is an oxidant within cells that can damage cells. When ROS levels are too high, oxidative stress can occur, damaging DNA, proteins, and lipids in cells and causing toxic effects such as cell apoptosis. The antioxidant defense system within aquatic organisms can help counteract the damage caused by ROS, including enzymes such as glutathione peroxidase (GSH-Px), glutathione-S-transferase (GSH-ST), catalase (CAT), and SOD (Sun et al., 2022). However, MPs can inhibit the antioxidant defense system of aquatic organisms, thereby exacerbating the toxic effects of ROS. Researchers have found that MPs PET do not have a significant negative impact on the survival, development, metabolism, and feeding activity of freshwater invertebrates (Gammarus pulex) (Weber et al., 2018). However, this toxicity varies within the same species and may depend on several factors, such as exposure time and concentration, the characteristics of MPs (such as type, size, and shape), and the traits of the organism itself (including ecological characteristics, behavior, and morphology). Therefore, the possibility of MPs causing toxicity to G. pulex in other exposure scenarios cannot be completely ruled out. Considering that these effects are mainly tested in a single species, it may be difficult to extrapolate these results to the actual environment, as stressors and interactions among organisms in ecosystems are complex, interdependent, and involve multiple non-biological and biological factors. Therefore, assessing the risk of MPs to aquatic ecosystems remains a challenging task, especially since our understanding of the impact of MPs is still relatively limited.

12.7 Effects of MPs in Marine Ecosystems This section will explore the impact of MPs on the marine environment, including their effects on water bodies, sediments, and organisms: the impact of MPs on marine water bodies, including their sources, distribution, concentration, and their chemical, physical, and biological effects on water bodies; the impact of MPs on marine sediments, including their deposition, distribution, concentration, and their effects on sediment composition, functionality, and biodiversity; the impact of MPs on marine organisms, including their ingestion, metabolism, and their effects on the physiology, biochemistry, and behavior of organisms.

12.7.1

Contamination of Seawater

Marine currents are an important factor influencing the distribution of MPs and are affected by various factors, including the movement of the currents themselves and wind. Marine currents and wind transport MPs, leading to their widespread distribution in aquatic ecosystems. This distribution is continuous and is also influenced by various economic activities, such as the movement of commercial ships, cargo, oil tankers, fishing, and small to

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large industrial facilities along the entire coast. Plastic degradation in seawater is extremely slow. Even biodegradable plastics take at least 5 years to completely degrade in the marine environment (Yuan et al., 2022). The degradation time for common polymers is between 10 and 20 years or 500–1,000 years, with the lifespan of most plastics ranging from 70 to 450 years (Yuan et al., 2022). However, these data are uncertain and based on estimates with no evidence to support them. In addition, physical and photolytic forces in the marine significantly inhibit the oxidative decomposition of plastics, especially in deep water, where plastics accumulate negative buoyancy. Therefore, most conventional plastics are not easily biodegradable in marine or terrestrial environments. Plastic polymers can only undergo physical degradation to some extent, i.e., being broken into smaller fragments by physical forces such as waves or sediment particles, but they do not change the total mass of plastic waste. Therefore, plastic polymers usually only change in size and distribution. In addition, when plastic is exposed to oxygen and sunlight’s ultraviolet radiation, it is oxidized to form hydrogen peroxide, leading to polymer chain breakage (Yuan et al., 2022). Furthermore, ship coatings also contribute to an increase in MPs in water. Ship coatings are applied to various components of ships to provide protection, including hulls, superstructures, and deck equipment. These coatings include solid coatings, anticorrosion coatings, or antifouling coatings. Various types of plastics are used in ship coatings, including polyurethane, epoxy coatings, vinyl, and varnish. Anti-fouling coatings are also considered a major source of heavy metal pollution. Heavy metals enter the marine system through the degradation and diffusion of coatings. Copper (Cu) is one of the typical and common metal pollutants in coastal areas. Cu(II) can accumulate and enrich continuously in marine bivalves, and its toxicity causes biochemical changes such as oxidative stress, posing a serious threat to the growth, reproduction, and overall survival of marine organisms (Wang et al., 2022). The oxygen-containing functional groups on the surface of MPs can provide adsorption sites for heavy metal ions, while electrostatic interactions, hydrogen bonding, and the formation of surface complexes also play important roles in the adsorption process. Fishing gear is a significant source of marine MPs and is frequently mentioned in related studies. It is abandoned, lost, or otherwise discarded for various reasons, such as adverse weather, gear conflicts, operational fishing factors including the cost of gear recovery, illegal, unreported, and unregulated fishing activities, intentional destruction/theft, and may stimulate the acquisition, cost, and availability of shore-based collection facilities for intentional offshore disposal. The photodegradation of MPs is closely related to their microscale interfaces, which are influenced by environmental factors such as salinity, ion species, pH, and temperature. Humic acid (HA) is a typical dissolved organic matter present in seawater and acts as a photosensitizer, playing a crucial role in the photodegradation of MPs (Qiu et al., 2022). Some studies suggest that HA inhibits the photodegradation of MPs through competition with light, transformation of ROS, and quenching of excited states (He et al., 2023a). In contrast, other research reports suggest that HA may promote the photodegradation of MPs by generating ROS (Chen et al., 2022b). Wen et al. (2023) found that salinity significantly affects the oxygen-containing functional groups of PS MPs during photodegradation in the presence of HA. PS MPs are more prone to forming double-bonded oxygen (C=O) under high salinity conditions, while they are more likely to form single-bonded hydroxyl (C─OH) in artificial seawater. This may be due to the complex composition of natural seawater, where interactions between constituents of PS MPs can lead to the formation

12.7 Effects of MPs in Marine Ecosystems

of unstable functional groups that have the potential to undergo transformations, resulting in diverse aging pathways for PS MPs. In addition, the presence of HA was found to promote the photodegradation of PS MPs. PS MPs at high salinity adsorb more HA, leading to the generation of more hydroxyl radicals (OH ) on the surface of PS MPs, thereby promoting their photodegradation. In conclusion, the impact of HA on the photodegradation of MPs is complex and influenced by multiple factors. Further research is needed to explore the mechanisms by which HA affects the photodegradation of MPs and the differences in its impact on MP photodegradation in different aquatic environments. Seafood and sea salt are two major sources of MPs ingestion for humans. The content of MPs in seafood and sea salt may vary depending on geographical location. Studies have shown that sea salt from East and South Asian coasts contains more MPs than sea salt from Australian, North American, and European coasts (Harris et al., 2021). According to one study, the MPs content in each fish species ranges from 26 to 34% (Cabanilles et al., 2022). Multiple bacteria found in marine aquatic systems possess the ability to degrade MPs, such as Alcanivorax sp., Azotobacter sp., Cycloclasticus sp., Hyphomonas sp., Methanosarcina barkei, Rhodococcus ruber. These bacteria secrete extracellular hydrolytic enzymes, such as chitinase, keratinase, lipase, protease, and xylanase, to degrade MPs into smaller molecules. Among them, the Methanosarcina barkei strain can degrade polyvinyl chloride (PVC). The strain can attach to the surface of PVC to form a biofilm and then release the above-mentioned enzyme mixture to hydrolyze the polymer bonds in PVC (Narayanan, 2023). R. ruber can secrete laccase to degrade PE into smaller molecules (Yao et al., 2022). Azotobacter sp. can produce catechol peroxidase to degrade PS into smaller molecules (Othman et al., 2021). Alcanivorax sp., Cycloclasticus sp., and Hyphomonas sp. species can degrade PET by hydrolyzing the ester bonds in PET, thereby changing its physical and chemical properties (Benavides Fernández et al., 2022).

12.7.2

Effects on Seabed Sediments

MPs enter marine sediments in various forms, including suspended in water, transported by rivers, and originating from various pollution sources. They ultimately deposit on the marine floor or in sediment, affecting sediment composition. Sediment is an important sink for MPs, which are frequently detected in sediments worldwide, even in remote areas such as the Pacific, Atlantic, and Antarctica. Plastics are heterogeneous, composed of various polymers, sizes, and shapes. These factors affect the buoyancy characteristics of plastics, thereby influencing their vertical distribution among different habitats (Fazey & Ryan, 2016) and their bioavailability to marine organisms at different depths (Erni-Cassola et al., 2019). Fragments have higher buoyancy and persist longer on the sea surface than other types of plastics (Chubarenko et al., 2018). Films have a higher surface area-to-volume ratio, facilitating biofouling processes and increasing their sinking rate, thus removing them more quickly from the water surface to the seafloor. Fibers have a faster density increase rate due to gradual fouling (Chubarenko et al., 2018) and are typically reported to be more abundant in sediments than surface waters and closer to land sources (Jorquera et al., 2022). Isobathic drift, deep-sea, and thermohaline currents also play a critical role in the horizontal transport of fine MP particles to deeper depths. Some authors have reported a positive correlation between MP abundance in marine sediments and chlorophyll content and

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concluded that marine algal aggregates play a critical role in the downward transport of MPs into the marine. Deeper depths have shown potential for absorption and alteration of MP buoyancy by various algae in laboratory experiments. Furthermore, MPs may have different negative impacts on marine ecosystems depending on their morphology and polymer composition. Compared to other types of plastics, such as foam, fragments are believed to have higher floating potential and play a role in the diffusion of marine biota between basins, potentially altering local food web structures. Benthic invertebrates ingested 83.53% of plastic products as fibers, accounting for 64.41% of plastic encountered in fish gastrointestinal tracts (Chen et al., 2023; Kane et al., 2020). According to the International Union for Conservation of Nature (IUCN) management, MPAs are classified into three main categories: Category Ia (Strict Nature Reserve), Category Ib/II (Wilderness Area), and Category III (National Park) (Nunes et al., 2023). Category Ia, also known as Ecological Stations (ES), aims to ensure minimal disturbance, restrict access, and prohibit human settlement. In fact, the lowest concentrations of MPs in sediments are found in this type of protected area (2 to 6 ± 1.5 particles/kg) (Nunes et al., 2023). Category Ib MPAs are unmodified or slightly modified areas, also known as Community-Based Reserves, which allow for local community use. Tourism activities are still permitted in buffer zones. In the wilderness area of Manan Bay, India, 33–133 MPs particles/kg were found in sediments. IUCN Category III, also referred to as Natural Monuments (NM), aims to protect specific natural features. In this category, the NM of Posidonia Reef Barrier in Spain (NM Arrecife Barrera de Posidonia) exhibited the highest concentration of MPs in sediment samples among nonfishing categories (2173 particles/kg) (Dahl et al., 2021). Posidonia is a highly complex marine ecosystem that shelters unique species in the Mediterranean. Due to the establishment of this MPA to ensure the safety of one of the Posidonia reefs, the high levels of MPs in sediments can cause physiological disturbances and damage the conservation objectives of this important heritage coral reef. The impact of MPs on microbial diversity in marine sediments is complex and varies depending on several factors, such as the type, size, shape, and concentration of MPs, as well as sediment properties and environmental conditions. Some studies report that MPs can reduce microbial diversity and richness in marine sediments and alter the abundance and composition of specific taxonomic groups, such as the phyla Proteobacteria, Bacteroidetes, and Cyanobacteria (Chen et al., 2023; Li et al., 2022a). Other studies have found no significant impact or even an increase in microbial diversity and richness in marine sediments due to MPs, depending on season, location, and MPs characteristics (Chen et al., 2023). Therefore, more research is needed to understand the mechanisms and consequences of MPs on microbial diversity in marine sediments. Seeley et al. (2020) revealed the impacts of different types of MPs on nitrogen cycling processes in coastal sediments. They found that PVC at a concentration of 0.5%wt significantly inhibited bacterial nitrification and denitrification processes in sediments. However, the same concentration of PE, PUF, and PLA simultaneously promoted nitrification and denitrification processes and significantly altered the microbial community structure. Weathered plastics have higher crystallinity than virgin plastics, indicating chain scission. The shorter the chains, the higher the crystallinity and brittleness. This is because degradation leads to structural and functional group damage, which increases polymer crystallinity. The increase in crystallinity is an indicator of oxidative scission and subsequent recombination

12.7 Effects of MPs in Marine Ecosystems

of smaller molecules, resulting in a more ordered structure through recrystallization. Bayo et al. (2022) reported that the crystallinity of plastic fragments in marine sediments was higher than that of the original packaging material. This may be due to the presence of more salt, sunlight, and microorganisms in the marine environment, which accelerate plastic weathering and result in chain scission. Fibers have the highest average crystallinity index in marine sediments, followed by films, fragments, and beads. Weathered MPs in marine sediments are more prone to adsorb other pollutants, such as hydrophobic organic compounds (HOCs).

12.7.3

Implications of Plastic Adhesion to Corals Surface

Despite coral reef ecosystems occupying less than 1% of the marine, they harbor the highest biodiversity among marine ecosystems. Unfortunately, climate change poses a severe threat to coral reefs, and even with reduced greenhouse gas emissions, the majority of global tropical coral reefs are at risk of extinction by 2050 (Vered & Shenkar, 2023). Pinheiro et al. (2023) conducted a survey of 25 locations in the Pacific, Atlantic, and Indian Marine basins, covering a total of 84 shallow and deep-sea coral ecosystems. This survey included 1,231 transects aimed at identifying anthropogenic macro debris, specifically objects larger than 5 cm created by humans, including plastics. The results showed that out of the 84 coral reefs surveyed, 77 had issues with anthropogenic debris, including some of the most remote and pristine reefs on Earth, such as uninhabited atolls in the central Pacific. MPs acroplastics accounted for 88% of the anthropogenic debris, reaching peak levels in deeper coral reefs (30–50 m in the mesophotic zone). Fishing activities were identified as the primary source of plastic pollution in most areas. These survey results indicate that plastic pollution poses a threat to many ecosystems, including coral reefs. It is estimated that the accumulation of plastic on shallow water coral reefs in the Asia-Pacific region alone exceeds 110 million items, with a projected increase of 40% by 2025 (Lamb et al., 2018). These figures serve as a reminder of the urgent need to take action to reduce plastic pollution and protect coral reefs and their ecosystems. Corals secrete mucus on their surfaces as a protective measure against harmful impacts from various environmental stressors. This mucus has strong adhesive properties, facilitating the attachment of MPs to the outer surface of corals. Plastics attached to the surface of coral can cause multiple stresses, including physical damage, light deprivation, inhibition of nutrient absorption, toxin release, and hypoxia. When coral communities come into contact with large amounts of marine plastic debris, the risk of disease infection increases significantly. According to a study by Lamb et al. (2018), when coral comes into contact with plastic, the infection rate increases from 4 to 89%. MPs interact with corals through active ingestion and passive surface adhesion. These plastic particles pose a serious threat to the health and survival of corals. Therefore, reducing plastic pollution and taking measures to prevent plastic from coming into contact with corals are important steps in protecting coral reef ecosystems. In the interaction between benthic plastic debris (BPD) and branching corals, 74% involve entanglement, 13% involve BPD covering corals, and another 13% involve corals settling on BPD. For massive corals, 35% of the interactions involve items covering corals, 33% involve entanglement, and another 33% represent large corals settling on BPD. As for soft corals, they mainly grow on plastic products, with 75% being settled, 20%

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being entangled, and 5% being covered. These data show the various ways in which different types of corals interact with human-made items (Vered & Shenkar, 2023). In hard corals of the Acroporidae, Pocilloporidae, and Merulinidae families, high-density MPs particles cover the coral surface more than low-density MPs (Rocha et al., 2020). Plastic products may introduce foreign microbial communities, such as opportunistic pathogens, to coral ecosystems, thereby disrupting normal host–symbiont relationships. For instance, floating plastic debris can serve as carriers for Rhodobacterales and Halofolliculina spp., which are opportunistic pathogens associated with coral disease outbreaks, such as white syndromes and skeletal eroding band (Huang et al., 2021). Similarly, MPs in coral reef areas may be enriched with disease-associated microbial communities, such as Vibrionaceae, Rhodobacteraceae, and Flavobacteriaceae, which are pathogens causing tissue damage and bleaching in corals (Huang et al., 2021). Researchers Rocha et al. (2020) found that PVC MPs exposed at a concentration of 10 mg/L significantly increased the adhesion of plastic to the coral surface. This may be due to the surface properties of PVC MPs, such as charge or surface roughness. Increased adhesion of plastic enhances the chances of coral coming into contact with and ingesting or adhering to plastic. Furthermore, PVC MPs induce oxidative stress in corals. Oxidative stress refers to an imbalance between oxidants and antioxidants within cells, leading to cellular damage. In the study, manifestations of oxidative stress included lipid peroxidation (LPO) and increased antioxidant defenses. LPO refers to the oxidation of cell membrane lipids, resulting in membrane damage. Antioxidant defenses are a way for cells to counteract oxidative stress. The adhesion of plastic may contribute to corals transmitting more light to their symbionts, thereby enhancing symbiont photosynthetic efficiency. Effects of MPs on coral–algae symbiosis and photosynthetic performance have also been observed. Studies have found that ingestion of MPs severely inhibits algae infection in corals or anemones, disrupting the establishment of symbiotic relationships. In addition, MPs can accumulate in coral tissues, occupying positions where algae would normally grow and impeding the normal coral–algal relationship. MPs also negatively impact algae growth, detoxification capacity, photosynthesis, and cell apoptosis, increasing oxidative stress and the risk of cell apoptosis (Huang et al., 2021).

12.7.4

Effects/Ecotoxicity of MPs in Marine Biota (Micro- and Macroorganisms)

Biofilms on the surface of plastics increase the likelihood of bioaccumulation of MPs by organisms with chemoreceptor-mediated feeding selection (Carbery et al., 2018). Once ingested, MPs enter the organism through the digestive tract and cause mechanical damage to the digestive system, such as intestinal blockage and perforation of the intestinal wall (Wang et al., 2020). Polymers are not digested by the enzymes in the organism, leading to digestive system blockage and reduced feeding activity (De-la-Torre, 2020). These issues result in weight loss, depletion of energy reserves, reproductive interference, changes in cholesterol ratios and distribution, malnutrition, and growth retardation (Wang et al., 2020). Fish exposed to MPs consumed approximately twice the amount of zooplankton compared to the unexposed control group (Carbery et al., 2018). The presence of MPs in the gastrointestinal tract causes inflammation, increased immune activity, and changes in metabolic profiles (Wang et al., 2020). In the acidic environment of the intestinal tract, plastics release toxic chemicals into the organism, resulting in long-term or acute effects (Carbery et al., 2018). Toxic chemicals or monomers released by MPs can transfer to visceral organs, tissues, and living

12.7 Effects of MPs in Marine Ecosystems

cells, as well as circulatory and lymphatic systems, leading to systemic dispersion (Wang et al., 2020). In summary, MPs pose serious risks to aquatic organisms, including damage to the digestive system, reproductive interference, malnutrition, growth retardation, inflammation, immune system impairment, and reproductive system damage. In addition, MPs may also carry organic chemicals (such as plasticizers), heavy metals (such as lead, mercury, and cadmium), and pathogens; these chemicals may adsorb onto the surface of MPs and be released within tissues, causing damage to the endocrine, immune, and reproductive systems (Sfriso et al., 2020). MPs in marine environments create a new ecological niche called the plastisphere, which is influenced by environmental and geographical factors such as plastic particle size, substrate type, surface characteristics, sampling location, and nutrient concentration and salinity. These microbial biofilms can alter the physical properties of MPs, such as size and buoyancy, and can degrade petroleum-derived and complex biopolymers, using MPs as an energy source. MPs are commonly associated with pathogenic bacterial genera, such as Vibrio, Leptolyngbya, and Pseudomonas, which can have significant impacts on the marine food web (Jiang et al., 2018). MPs also promote the colonization of harmful algal species, such as Alexandrium taylori, Ostreopsis spp., and Coolia spp., which attach to floating plastic debris. Proteobacteria and Bacteroidetes are dominant bacterial phyla in the plastisphere, which may have important implications for the biogeochemical functions of MPs (Khalid et al., 2021). Studies have found that low concentrations of PE MPs (10 and 50 mg/L) decrease the abundance of Proteobacteria but increase the abundance of Planctomycetes and Bacteroidetes. Under high concentrations (300 mg/L), Proteobacteria (80%) may play a key role in the biogeochemical functions of EPS and inhibit the growth of Bacteroidetes, Planctomycetes, and Actinobacteria, resulting in significant changes in microbial community composition and abundance (Hung et al., 2022). MPs buried in sediments encounter different biogeochemical zones and corresponding microbial communities, which can influence the degradation process of MPs. Sulfate reduction is a major microbial respiration pathway in marine sediments, and the selective attachment of sulfate-reducing bacteria to plastics suggests potential affinity and utilization of carbon in plastics as an electron donor (Rogers et al., 2020). MPs can be ingested by larger organisms (sea turtles), leading to health issues such as intestinal blockage, malnutrition, and compromised immune function. Sea turtles, important predators in the marine environment, are prone to plastic ingestion, which can be mistaken for food or enter their digestive tract during feeding. Plastic fragments can block the intestinal tract, leading to digestive issues, malnutrition, and death. In addition, plastic fragments may release toxic compounds, such as bisphenols, phthalates, and heavy metals, which can harm the immune system, reproductive system, and other organs of sea turtles. Due to their long lifespan, feeding ecology, habitat utilization, and tendency to ingest plastic, debris has been observed in their gastrointestinal contents and feces (Omeyer et al., 2023; Solomando et al., 2022). A study analyzed 67 rescued Caretta caretta from Spain between 2019 and 2021, focusing on plastic ingestion. The turtles were rescued due to various reasons, including entanglement, positive buoyancy, pneumonia, trauma, bycatch, and intestinal obstruction. The majority were juveniles, with 23 ingesting more plastic than adults. The study found that early-stage juvenile turtles ingested more plastic than late-stage juveniles and adults (Solomando et al., 2022). In addition, the presence of MPs in sea turtle embryos suggests maternal transfer as a primary pathway for MPs to enter the liver and yolk sac (Chemello et al., 2023). The study also found organophosphate esters (OPEs) in C. caretta muscle tissue, indicating contamination through

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prey consumption and plastic fragments. These OPEs have toxic properties, including developmental toxicity, neurotoxicity, and endocrine disruption, posing a significant threat to their health and reproduction (Sala et al., 2021). MPs play a crucial role in the bioaccumulation of pollutants and can act as carriers for these pollutants in the environment. Their small size, large surface area, and hydrophobicity contribute to their ability to adsorb substances on their surface. Studies have shown that exposure to copper, MPs, and organic matter significantly increases copper bioaccumulation in zebrafish compared to exposure to copper alone (Qiao et al., 2019). However, some studies suggest that plastics have little effect on the accumulation of pollutants. Exposure to MPs does not increase the bioaccumulation of co-pollutants in the absence of food (Sıkdokur et al., 2020). MPs can also enhance the toxicity of other coexisting chemicals to aquatic organisms. The specific effects depend on factors such as the type, size, concentration, and type and concentration of MPs and other pollutants (Table 12.1). Further research is needed to fully understand MPs’ impact on aquatic organisms and develop effective management strategies. Table 12.1 Interactions Between Microplastics and Other Pollutants: Biological Effects Pollutants

Research objective

Biological impacts

Reference

PAHs

Copepods: Acartia MPs can mitigate the toxicity of PAHs Amelia et al. (2021) tonsa and Calanus finmarchicus

PCBs

Norway lobster: Nephrops norvegicus

the pollutants show no apparent bioaccumulation effects

Arp et al. (2021)

PBDEs

Rainbow Fish: Melanotaenia fluviatilis

inducing the Bioaccumulation of PBDEs

Giraudo et al. (2017)

Hg

Dicentrarchus labrax

elevated oxidative stress

Anderson et al. (2016)

Cu

Zebrafish: Danio rerio

increased AChE activity

Santos et al. (2021)

Cd

Early discus fish juveniles: Symphysodon aequifasciatus

early adolescents experience severe Menéndez-Pedriza oxidative damage and immune system and Jaumot (2020) stimulation, leading to an impact on their innate immune response

Ag

Fungal community

biomass of fungi, enzyme activity, and Conesa (2022) the rate of litter decomposition all exhibit a declining trend

Li

Daphnia magna

deceleration in growth rate

Pharmaceutical (venlafaxine)

Weather Loach: Misgurnus anguillicaudatus

accumulation of the drug increases in Klavins et al. (2022) the organism

Pesticides

Copepod: A. tonsa gradual deterioration of appearance and structure

Martins et al. (2022)

Menéndez-Pedriza and Jaumot (2020)

AChE: acetylcholinesterase; MPs: microplastics; PAHs: polycyclic aromatic hydrocarbons; PBDEs: polybrominated diphenyl ethers; PCBs: polychlorinated biphenyls.

12.7 Effects of MPs in Marine Ecosystems

12.7.5

Effects on Different Developmental Stages of Invertebrates

Invertebrates are crucial in MPs research due to their diverse characteristics, such as tolerance to environmental stress and life strategy. They serve as indicators in the accumulation process, with pollutants affecting their functional traits. High concentrations of MPs can decrease the activity of lipase enzymes in organisms such as oysters, crayfish, and sea cucumbers, which are essential digestive enzymes in animal bodies (Liu et al., 2022). Sussarellu et al. (2016) found that particulate PS MPs have adverse effects on oyster reproduction and feeding due to changes in food intake and energy distribution. Oysters exposed to particulate PS decrease their number of spawned eggs, oocyte quality, and sperm vitality. Ingestion of micro PS results in decreased sperm velocity and quantity. A substantial amount of 6 μm micro-PS particles were detected in the excreta of oysters, indicating a significant ingestion level. A substantial amount of 6 μm micro-PS particles were detected in the excreta of oysters, indicating a significant ingestion level. The yield of oysters exposed to MPs and the growth of their offspring decreased by 41% and 18%, respectively. This study highlights the antagonistic effects of micro PS on oyster development and reproduction, with significant implications for offspring (Galloway & Lewis, 2016). The energy balance of gonads in Pacific oysters (Crassostrea gigas) is significantly affected by exposure to PS particles (Brandts et al., 2018). These particles impact fertilization, embryonic development, and metamorphosis, leading to deformities and developmental arrest. Studies have shown that PS particles reduce fertilization success rates and normal larvae development, causing severe developmental defects. In sea urchin embryos, toxicity reactions were observed within 48 hr after fertilization. PS accumulates in the embryonic digestive tract and induces developmental defects through upregulation of the Abcb1 and cas8 genes (Della Torre et al., 2014). Researchers have also investigated the effects of PS MPs concentrations on sea urchins and ascidian, finding that both species exhibited efficient feeding strategies for MPs ingestion. In the presence of microbeads, the meta-morphosis rate of sea squirt larvae slowed down, and their development was altered (Messinetti et al., 2018). Another study on sea cucumber, starfish, and sea urchin larvae feeding on 6 μm beads and larger inedible beads showed changes in ingestion rates (Lizárraga et al., 2017). Although different species have varying sensitivities to MPs, clearance rates decrease with an increase in particle number. This study suggests that MPs may be considered inedible particles that could disrupt normal larval feeding and potentially lower their quality and performance in natural environments. In the mussel Mytilus galloprovincialis, exposure to 3 μm PS MP had sublethal effects on embryonic larval development. However, despite being ingested and retained in the digestive tract for over 192 hr, MPs did not impair clearance rates or edible food intake (Capolupo et al., 2018). Researchers studied the effects of MPs on the early developmental stages of sea urchins (Paracentrotus lividus) and sea squirts (Ciona robusta) in Mediterranean shallow waters. Both species exhibited ingestion of MPs during their development, with filterfeeding organisms being more susceptible. Although MPs exposure did not affect survival rates, it significantly impacted their development. Ingestion of plastic beads slowed metamorphosis in Ciona robusta and altered embryonic postdevelopment and growth in P. lividus. The diminished ability to clear intestinal plastics with increasing MPs concentrations was also observed. Prolonged exposure to MPs can lead to accumulation in the digestive tract, damage to nutrient absorption, and animal mortality, raising concerns about the ongoing impact of MPs on marine ecosystems and potential ecological risks (Messinetti

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et al., 2018). MPs’ impact on organisms increases with decreasing size, particularly during early life stages like gametes, embryos, larvae, and juveniles. The sea urchin (Lytechinus variegatus) larvae have shown the most significant negative impact, with abnormal development rates increasing by 58.1–66.5% after exposure to MPs. Smaller invertebrates, which dominate the abundance and play a crucial role in natural ecosystems, are essential for studying their impact on ecosystem functioning and predicting plastic pollution’s effects (Nobre et al., 2015). Cole et al. (2015) found that MPs ingestion significantly impacts the feeding behavior, reproductive capacity, and function of zooplankton, such as copepods. Studies on Atlantic species, such as Calanus helgolandicus copepodus, showed that exposure to 20 μm PS microbeads led to a 40% reduction in carbon biomass, energy deficiency, and rapid depletion of fat stores in copepods, resulting in impaired growth and mortality. Prolonged exposure also reduced hatching success. PE exposure decreased the activity of isocitrate dehydrogenase in larval fish’s gallbladder. In addition, mortality was found in brine shrimp following exposure to PS MPs (Suman et al., 2020).

12.8

Increase in Toxicity and Impacts on Biodiversity

Plastics accumulate in the aquatic food chain and are ingested by humans, affecting aquatic biota. This pollution has a significant impact on marine organisms’ biodiversity, including ingestion, toxicity, and habitat destruction. It can lead to reproductive disorders, immune system suppression, and mortality. Therefore, studying the effects of MPs on aquatic biota is crucial. The sources of MPs affecting aquatic organisms can be categorized into direct and indirect sources, including plastic tools, fishing nets, ropes, foam buoys, sun exposure, crustacean crawling, burrowing crustaceans, and foam-made oyster rafts. Direct sources include plastic tools, which break down into MPs when exposed to sunlight, wind, waves, and sand mechanical action. Indirect sources include fishing nets, ropes, and foam buoys (Chen et al., 2022a). In the aquaculture industry, high-protein feed ingredients like fishmeal and shrimp meal are primarily derived from wild-caught fish and shrimp. MPs consumption by these animals introduces them into aquaculture habitats during farming due to marine MP pollution (Zhou et al., 2021). Aquaculture feed contains MPs, with studies showing that fishmeal from Italy contains 50–100 mg/kg of MPs, while shrimp meal and fishmeal from five countries contain 10.7 n/100 g and 5.4 n/100 g of MPs, respectively (Castelvetro et al., 2021). In coastal oyster farming areas like Dafeng River in China, the MPs load is estimated to be 8.3 × 108 particles/year (Liu et al., 2021a). Packaging materials like expanded PS boxes, corrugated plastic boxes, and plastic trays can also release MPs, with PS plastic being the primary contributor (Skirtun et al., 2022). When aquatic organisms ingest MPs, they can accumulate in their bodies, leading to false satiety, affecting their feeding capacity, and potentially causing gastrointestinal blockage and malnutrition. MPs can negatively affect the feeding and swimming abilities of different aquatic organisms, such as Sebastes schlegelii and Pomatoschistus microps (Oliveira et al., 2013; Yin et al., 2018). MPs can also disrupt olfactorymediated behavioral responses in goldfish by hindering mechanisms like odor recognition (Shi et al., 2021). Exposure to PS MPs can impede the growth rate of Japanese medaka (Pannetier et al., 2020), increase the absorption efficiency of Nile tilapia for chemical pollutants (Zhang et al., 2019), stimulate immune responses, trigger antioxidant defenses, and shorten the intestinal villi of hybrid black rockfish (Zhang et al., 2022a).

12.8 Increase in Toxicity and Impacts on Biodiversity

It is worth note that MPs and their associated additives can adversely affect the immune system and nervous system of aquaculture products, potentially compromising their overall quality, leading to decreased survival rates and economic losses in aquaculture. Bisphenol A (BPA), used as a monomer for epoxy resins and polycarbonates, can exert cytotoxic effects in living tissues and may be associated with reproductive abnormalities (Chen et al., 2021). MPs particles with added PVC and polyvinyl alcohol significantly increased the content of antibiotic resistance genes (ARGs) in estuarine sediments, suggesting that MPs may exacerbate the diversity of ARGs in river water (Dong et al., 2021). A study found that PS MPs and 16 representative polycyclic aromatic hydrocarbons (PAHs) had significant toxic effects on blood parameters of Tegillarca granosa. MPs and PAHs mixtures decreased total hemocyte count (THC), altered blood composition, and inhibited phagocytic activity. They also increased intracellular ROS levels, leading to LPO, DNA damage, and reduced blood cell viability. This suggests that simultaneous exposure to MPs and PAHs mixtures may be more severe than exposure to single pollutants (Sun et al., 2021). Aquaculture production is expected to decline due to the negative effects of MPs on aquaculture goods. Research shows that almost one-third of deceased fish contain PE MPs and other inorganic chemicals (Wu et al., 2023a). Juvenile Eastern tuna and adult dagger blade shrimp have mortality rates ranging from 5 to 40% when exposed to MPs particles and fragments greater than 50 μm. African catfish exposed to 2 g/L PE MPs have a mortality rate of 10%. This increased mortality rate and decreased reproductive efficiency of aquaculture products will lead to a decline in the economic benefits of aquaculture. The reproductive effects of MPs on aquaculture products could also decrease the amount and quality of resources like fish fries. Table 12.2 provides a comprehensive overview of the Table 12.2

Impacts of Microplastics on Various Aquatic Food Products

Food

MPs concentrations

Natural salt

7–681 pieces/kg

Composition of MPs

Size range of MPs

Shapes of MPs

Reference

PET, PES, PE, PP, 0.03–4.3 mm Fibers, fragments, Iñiguez CP, PB particles et al. (2017)

Commercial 1–10 pieces/kg salt

PE, PET, PS, 0.16–0.98 Polyacrylonitrile mm

Fragments, filaments, films

Oysters

Polyester, PP, PE 0.02–5 mm

Fibers, fragments, Li et al. particles, sheets (2018)

1.4–7 pieces per oyster”

Asian sea bass: Lateolabrax maculatus

Karami et al., (2017)

Digestive Tract: PES, PP, PE 0.3–5.3 items per individual; Gills: 0.3–2.6 items per individual Giant yellow 0.008 ± 0.006 items/ PET croaker: kg dry weight Larimichthys crocea

Less than 1 mm to greater than 1 mm

Fibers, fragments Su et al. (2019)

74–1,500 μm

Fibers

Wu et al. (2020)

Carp: Cyprinus carpio

0.3–0.6 mm

Fragments

Park et al. (2020)

Digestive Tract: 22.0 PTFE ± 16.0 particles/fish; Gills: 8.3 ± 6.0 particles/fish

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impact of MPs and other pollutants on aquatic food products. MPs negatively impact human health by decreasing digestive enzyme activity and affecting digestion absorption. They may also contribute to the build-up of organic contaminants in aquaculture products, increasing potential health risks. These additives are mutagenic, teratogenic, and reproductively toxic, making it crucial to address MPs pollution in aquaculture.

12.9

Conclusions

MPs are tiny plastic particles made from various sources, including industrial waste, household waste, and detergents. They enter aquatic environments through various pathways, including rivers, lakes, and marines. Aquatic organisms ingest MPs and transfer them to other organisms through the food chain. MPs accumulate in the bodies of aquatic organisms and may affect their health. The impacts of MPs on aquatic environments include water pollution, affecting water quality, and affecting the health of aquatic organisms, including growth, development, reproduction, and behavior. MPs also disrupt aquatic food chains, affecting biodiversity. The impacts of MPs on fisheries and aquaculture include reducing catch yields, affecting the nutritional value and safety of aquaculture products, and increasing the cost of aquaculture. Therefore, measures need to be taken to reduce MPs pollution and protect aquatic environments and biodiversity. The following policy recommendations can help address MPs pollution: 1) Ban or restrict the use of disposable plastics, such as plastic bags, straws, and utensils, to reduce plastic waste. 2) Promote extended producer responsibility policies that require producers to take responsibility for the entire life cycle of their products, encourage sustainable practices, and reduce MPs pollution in product design. 3) Strengthen waste management infrastructure to ensure proper collection, recycling, and disposal of plastic waste. 4) Encourage research and innovation to find solutions to reduce MPs pollution, including supporting research on alternative materials and sustainable product design. 5) Strengthen wastewater treatment regulations to effectively remove MPs from wastewater. 6) Promote international cooperation and standards to jointly develop international standards for monitoring, research, and reduction strategies for MPs. 7) Conduct public education activities to raise awareness of the impacts of MPs and promote individual actions to reduce plastic waste. Policy recommendations need to be adjusted according to the specific situations and challenges in different regions or countries. A comprehensive approach and stakeholder engagement can make significant contributions to reducing MPs pollution.

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13 Human Exposures to Microplastics Impact of Different Routes Sanket Dey Chowdhury1, Sudeep Kumar Mishra1, Puspendu Bhunia1∗, Rao Y. Surampalli2, and Tian C. Zhang3 1

Environmental Engineering, School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 3 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 2

13.1 Introduction Plastics significantly impact the overall enhancement of human health by enabling the manufacturing of disposable medical equipment and contributing to improving food safety. The global output of plastic has increased by a factor of 20 over the past 50 years because of the high demand for plastic items, leading to unrestrained expansion in plastic production (Geyer et al., 2017). According to estimates, approximately 9,200 million metric tonnes of plastics have been produced since the start of plastic manufacture in 1950 (Walker & Fequet, 2023), which is expected to increase to 12,000 million metric tonnes by 2050 (Ding et al., 2019). In 2019, worldwide plastic production reached 368 million metric tonnes (Walker & Fequet, 2023), and it is projected to double in the following 20 years (Lebreton & Andrady, 2019). Nevertheless, the improper handling of plastic wastes that enter the environment may have unintended consequences, such as creating a favorable environment for diseasecarrying mosquitoes or obstructing water drainage, leading to flooding and the transmission of diseases (Pullin & Knight, 2005). The majority of manufactured plastics are intended for disposable usage, which leads to an increase in the production of plastic waste and the potential for plastic pollution (Borrelle et al., 2020). Of the entire plastic waste produced worldwide, a mere 9% is recycled, 12% is incinerated, and the remaining 79% lingers inside natural ecosystems (Geyer et al., 2017). The inadequate handling of plastic waste has resulted in the accumulation of more than 250,000 tonnes of plastic fragments suspended in the oceans (Eriksen et al., 2014). In 2010, coastal countries discharged an estimated 4.8–12.7 million metric tonnes of plastic into the oceans (Jambeck et al., 2015).

∗

Equal contributor.

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Plastics in the environment, coming from improperly disposed consumer products, break down slowly due to exposure to light and heat and by biodegradation to a small extent. This degradation weakens the plastic and causes it to break into smaller pieces, less than 5 mm in size, known as secondary microplastics (MPs) (Andrady, 2011). Plastic particles of this size that are deliberately made for use in products like cosmetics or by industries, such as air blasting, are referred to as primary MPs (Browne et al., 2011). The presence of MPs is already detected in seawater at concentrations of up to 102,000 particles/m3 (Prata et al., 2020). Of late, MPs are also found to contaminate freshwater (Eriksen et al., 2013; Estahbanati & Fahrenfeld, 2016; Rodrigues et al., 2018), soil (Watteau et al., 2018; Zhang et al., 2018), sediment (Abidli et al., 2018; Reed et al., 2018), air (Abbasi et al., 2019; Dris et al., 2016), and even drinks and food items like beer, sea salt, tap water, bottle water, etc. (Kosuth et al., 2018; Qian et al., 2024). Owing to the ubiquities of MPs in the environment and consumer products, human beings are inevitably exposed to the MP particles. This chapter comprehensively overviews the potential routes through which human beings are exposed to MPs (Figure 13.1) and the existing information on the impact of environmental exposure to MPs on human health. The understanding of the effects of MPs on human beings is restricted due to ethical

Figure 13.1 Schematic Representation of the Exposure Pathways of Human Beings to Microplastics and the Possible Health Effects

13.2 Pathways of Human Exposure to Microplastics

limitations, limited detection methods, and stringent biosecurity protocols for handling human samples. Therefore, the investigation of MP exposure and toxicity encompasses data obtained from the organism tests as well. Moreover, to gain a better understanding of the interactions between the MPs and the organisms, as well as the toxic effects of MPs at the tissue, cellular, and molecular levels, the studies conducted on the usage of various biomarkers (i.e., biological indicators of normal/abnormal biological responses), e.g., antioxidant enzymes, acetylcholinesterase (AChE), etc., to elucidate the mechanisms of the interactions as well as the biological responses, including oxidative stress, genotoxicity, neurotoxicity, metabolic disorder, etc., due to the exposure of the representative organisms to MPs are briefly overviewed. The present chapter also deals with a few recent case studies on human exposure to MPs.

13.2 Pathways of Human Exposure to Microplastics From the exhaustive literature, it has been observed that the major routes through which human beings are exposed to MP contamination can be predominantly classified into three types, such as ingestion (Cox et al., 2019; Li et al., 2020a, b; Oßmann et al., 2018), inhalation (Prata, 2018; Vianello et al., 2019; Zhang et al., 2020), and dermal contact (Hernandez et al., 2017; Li et al., 2023a, b; Revel et al., 2018). Each of these pathways is briefly discussed below.

13.2.1

Ingestion

The primary route through which human beings are exposed to MPs is ingestion (Galloway, 2015). According to Cox et al. (2019), the estimated annual intake of MPs per person varies between 39,000 and 52,000 particles depending on the foodstuff consumption. MP particles can enter the gastrointestinal system either by the consumption of contaminated food items or by mucociliary clearance after inhalation, causing an increased permeability, inflammatory response, and alterations in the composition and metabolism of gut microbes (Salim et al., 2014). The existence of MPs has been identified in many food items, including mussels (Li et al., 2016), fruits and vegetables (Conti et al., 2020), table salt (Karami et al., 2017), commercial fish (Neves et al., 2015), sugar (Liebezeit & Liebezeit, 2013), and bottled water (Oßmann et al., 2018; Qian et al., 2024), indicating that they are likely to be consumed. Conti et al. (2020) recently assessed the quantity of particles ingested through the consumption of fruits and vegetables. An average of 132,740 MP particles/g were found in five frequently consumed vegetables and fruits (i.e., apples, broccoli, pears, carrots, and lettuce). Using these statistics as a representative sample for this group of foods, and adhering to the guidelines of the World Health Organization (WHO) to consume a minimum of 400 g of fruits and vegetables daily, individuals would be intaking 53.096 million MPs per day. When considering the uptake of MPs through drinking water, it is important to consider the recommended daily water intake by the European Food Safety Authority (EFSA), which is 2.5 L for males and 2 L for females (Domenech & Marcos, 2021). Also, the existence of MPs in both bottled and tap water has been reported by various researchers, revealing significant fluctuations in the observed data. For instance, Cox et al. (2019) investigated that the average MP concentrations in bottled water and tap water were 94 and 4.2 particles/L,

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respectively. Based on the average daily consumption patterns of water by human beings, the daily intake of MPs via drinking water was estimated to be 47, 48, 51, and 55 MPs for female children, male children, female adults, and male adults, respectively. Compared to tap water, the projected dose of exposure to MPs was almost 22 times more from bottled water. An individual who consumes just bottled water is expected to ingest 90,000 MP particles/year, while someone who consumes only tap water ingests only 4,000 MP particles/ year. Again, the presence of polyethylene (PE), polypropylene (PP), polyamide (PA), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) MPs (≥ 50 μm) in packaged water bottles at a concentration of 140 particles/L was reported by Kankanige and Babel (2020). Mason et al. (2018) identified the existence of PP and nylon MPs at an average concentration of 325 MPs/L in packaged water bottles bought worldwide, whereas Oßmann et al. (2018) detected 2649 MPs/L, and Kosuth et al. (2018) found 3.57 MPs/L of bottled drinking water. The aforementioned researchers classified MPs as anthropogenic debris, although the identification methods utilized do not fully establish the origin of MP particles. In contrast, Zuccarello et al. (2019) found that the water in plastic bottles had an average PET concentration of 54,200,000 particles/L. Based on the given statistics, humans would ingest an average of 13,552,978 MP particles/L of water from single-use plastic bottles, causing a daily consumption of 27,105,956 MP particles, assuming a total intake of 2 L of bottled water per day. In a recent study by Li et al. (2020b), it was demonstrated that approximately 16 million MP particles/L were released from PP feeding bottles during the sterilization process, indicating that newborns, fed milk in PP bottles, could be exposed to around 3 million MPs every day. Qian et al. (2024) reported that 1 L of bottled water embraced 2.4 ± 1.3 × 105 micro (10%) and nanoplastic (90%) particles of which PA, PP, PET, PE, PVC, polystyrene (PS), and polymethyl methacrylate (PMMA) were predominant. Similarly, immersing plastic tea bags in hot water at a temperature of 95 C releases 2.3 million MP particles and 14.7 billion nanoplastic particles into a cup of tea (Kannan & Vimalkumar, 2021). MPs can also enter human bodies through the consumption of sea salt. The studies showed a wide range of MP concentrations in sea salts, varying from 9.77 particles/kg (Lee et al., 2019) to 506 particles/kg (Kim et al., 2018). The average concentration of MPs in the table salt was estimated to be 142.8 particles/kg. According to the recommendations of WHO, healthy adults should restrict their daily salt intake to 5 g. Therefore, by ingesting table salt, humans would be consuming approximately 0.714 g of MPs/d. Kim et al. (2018) examined sea salt samples from different countries for MP contamination and concluded that the levels of MPs in table salt from Asian countries were greater compared to table salt from other continents. The predominant types of MP particles found in sea salt samples were PE, PP, and PS. However, the data obtained from the analysis of MPs in sea salt are susceptible to inconsistencies in the methods used. Yang et al. (2015) and Karami et al. (2017) reported that the average consumption of MPs in table salt was 100 and 37 MPs person−1 year−1 in China and Europe, respectively. The presence of MPs in seafood has also been reported in several studies (Fang et al., 2019; Rochman et al., 2015). Fang et al. (2019) reported that bivalves obtained from Xiamen in China embraced MP particles (100–4,000 μm) at a concentration of 0.11–0.12 particles/g. Van Cauwenberghe and Janssen (2014) concluded that the ingestion of bivalves by Europeans resulted in an exposure of 11,000 MPs person−1 year−1. On the other hand, the level of MP contamination in a pacific oyster, Crassostrea gigas, was examined by

13.2 Pathways of Human Exposure to Microplastics

Rochman et al. (2015). It was revealed that the concentration of MPs (> 500 μm) in C. gigas was 0.6 particles/g. In a report published by EFSA in 2016, the presence of MPs in seafood was emphasized, and it was highlighted that the concentrations of MP particles in seafood were 0.2–4 particles/g of bivalves, 0.75 particles/g of shrimp or crab, and 1–7 particles/g of fish (Kannan & Vimalkumar, 2021). The consumption of sugar and honey may also lead to the exposure of human beings to MP contamination. For instance, Liebezeit and Liebezeit (2013) identified 217 MP fibers/kg and 32 MP fragments/kg in sugar samples. According to WHO, for adults, sugar consumption should not exceed 27 g person−1 d−1 (Kannan & Vimalkumar, 2021). Hence, individuals consuming sugar could be exposed to 2,139 MP fibers/year and 316 MP fragments/ year. On the other hand, Cox et al. (2019) investigated the presence of MPs in sugar and honey, and it was reported that, on average, the concentration of MPs in sugar and honey was 0.44 MPs/g and 0.10 MPs/g, respectively. Again, the ingestion of chicken as a protein diet can be a potential route for MPs to enter human bodies. Huerta Lwanga et al. (2017) reported that the average number of MP particles found in the crops and gizzards of chickens grown in home gardens was 11 and 63, respectively. It was also noticed that there was an increase in the levels of MPs from soil (0.89 particles/g) to earthworms (15 particles/g) to chicken (130 particles/g). According to Catarino et al. (2018), the deposition of dust on plates during meals might have a greater impact compared to the MPs that are present in food. In a recent study by Kosuth et al. (2018), the presence of MPs in beer (alcohol) samples was detected. It was reported that the mean concentration of MPs in beer was 4.05 particles/L. On the other hand, Rist et al. (2018) emphasized concerns regarding the contamination of consumed organisms compared to the probable contamination caused by packing and plastic containers. Kedzierski et al. (2020) examined the surface of the packaged meat products, specifically white chicken breast and turkey, and discovered the presence of PS MPs at a concentration of 4.0–18.7 particles/kg of packaged meat. These MPs adhered to the surface of the meat even after the washing. The authors proposed that the presence of PS MPs could be attributed to the dispersed PS dust present in the air of the production farm. Similarly, Guerreiro et al. (2018) reported the migration of phthalic anhydride, stearamide, diisooctyl phthalate, and polyethylene glycol particles from plastic packaging to beef pieces. Furthermore, there have been reports indicating that ruminant animals tend to store nondigestible plastic compounds in their rumen. Consequently, MP particles potentially reach the human food chain via milk and meat products that have been contaminated (Priyanka & Dey, 2018). Kutralam-Muniasamy et al. (2020) examined 23 samples of dairy milk from Mexico and discovered that the concentration of MP particles varied in the range of 3–11 particles/L of milk. The predominant MPs detected in the milk samples included PE, PP, PS, PET, polyurethane (PU), PA, PVC, PMMA, and styrene acrylate. Processed milk had higher concentrations of MP particles compared to raw milk. The primary cause of MP contamination in milk could be the utilization of sulfone polymers in the filtration process in dairy industries (KutralamMuniasamy et al., 2020). The ingested MP particles display the potential to be adsorbed by specialized M-cells in the intestine, covering an intestinal lymphoid tissue, known as Peyer’s patches. The extent of adsorption of MPs also depends on the adherence of MP particles to the gastrointestinal mucus, with higher adherence resulting in a faster clearance rate of the particles

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(Ensign et al., 2012). On the other hand, insoluble particles percolate through the intestinal mucus by becoming more soluble through the adsorption of intestinal contents or because of their small sizes (Powell et al., 2007). A similar observation has already been reported for PS latex particles of sizes 14 and 415 nm in rat intestinal sections but not for the PS particles of size larger than 1.09 μm (Szentkuti, 1997). The MP particles can also be internalized via paracellular transport through the single layer of the intestinal epithelium, referred to as perception (Volkheimer, 1977). MPs may undergo similar mechanisms as their transportation to the circulatory system following oral intake has been observed in living organisms. In rats, 6% of PS (0.87 μm) entered the circulation within 15 min following the oral administration (Eyles et al., 1995). On the other hand, when rats were exposed to 1.25 mg/kg of PS of 50 nm diameter, 34% of it was absorbed. It is possible that this absorption occurred through the mesentery lymph, resulting in the accumulation of PS particles in the liver (Jani et al., 1990). In addition, human colon fibroblasts were able to internalize and release 44 nm PS nanospheres by passively translocating them across the cell membrane, as demonstrated by Fiorentino et al. (2015). When taken up by human gastric adenocarcinoma cells, 44 nm PS particles had an impact on gene expression, suppressing cell viability and triggering proinflammatory reactions and alterations in cell morphology (Forte et al., 2016). Hence, there is a high probability of human exposure to MPs by ingestion due to the contamination of the food and environment with MPs. Nevertheless, the potential danger of consuming MPs remains uncertain owing to the limited research conducted on assessing the comprehensive human exposure to MPs and its impacts.

13.2.2

Inhalation

Even though it was previously believed that diet was the primary way humans could be exposed to MPs, recent research on airborne MPs suggests that inhaling indoor air may actually be the main source of exposure to MPs (Cox et al., 2019; Wang et al., 2021). Owing to low density and small size, MPs display the ability to be suspended in the air and the potential to travel through the air. As a result, the airborne MPs can be directly inhaled by human beings. In the very first assessment of MPs in the air by Dris et al. (2017), it was found that the outdoor concentrations of MPs ranged from 0.3 to 1.5 particles/m3, while the indoor MP concentrations ranged from 0.4 to 56.5 particles/m3. It was also noticed that almost one-third of the identified MPs were polymers possessing inhalable sizes. The estimated daily inhalation of airborne MPs for an individual varies between 26 and 130 (Prata, 2018). Cox et al. (2019) reported that the mean concentration of MPs in the atmosphere was 9.8 MPs/m3. An inhaling rate of 15 m3/d could result in a yearly inhalation of 53,700 MP particles per person. MPs are emitted into the atmosphere by several sources, such as roads, the abrasion of materials (such as automobile tires and construction materials), synthetic textiles, incineration of plastic wastes, landfills, and the resuspension of MPs on surfaces (Dris et al., 2015; Prata et al., 2020). The largest contributor of MPs (84%) to air is roads (Brahney et al., 2021). Cai et al. (2017) revealed that in Dongguan (China), the overall concentration of MP particles, including PE, PP, and PS (< 200–4,200 μm), in road dust was 175–313 particles m−2 d−1. According to the air sampling conducted employing a mannequin, it is anticipated

13.2 Pathways of Human Exposure to Microplastics

that a male adult engaged in light exercise will inhale 272 MPs every day (Vianello et al., 2019). Vianello et al. (2019) conducted a study to investigate the indoor air quality in Aarhus (Denmark) and reported the presence of polyester (PEST) (59–92%), nylon (0–13%), PP (0.4–10%), and PE (5–28%) MPs (4–398 μm) at a concentration of 1.7–16.2 particles/m3. Dris et al. (2017) found that the indoor air concentration of MP particles in Paris (France) was up to 11,130 particles m−2 d−1. It was also reported that the concentration of MPs in indoor air was around 5–10 times greater than that in outdoor air. In addition, the concentration of MPs in urban air was almost twice as high as in suburban air in France. Qian et al. (2017) made an effort to determine the MP concentration in the outdoor air in Yantai (China). The results indicated the dominance of PS, PP, PE, PET, and PVC MPs in the outdoor air, which were present at an overall concentration of 0–602 particles m−2 d−1. In a study conducted by Zhang et al. (2020) on indoor dust samples from 12 countries, the prevalence of PET-based MPs at concentrations ranging from 38 to 120,000 mg/g and PC-based MPs at concentrations ranging from less than 0.11 to 1,700 mg/g was observed in all samples. It was also mentioned that PET was the most prevalent MP detected in indoor dust. A newborn baby exposed to PET MPs through the inhalation of indoor dust could intake up to 150,000 ng of PET/kg of body weight, equivalent to 10 mg of PET/d for an individual with a body weight of 70 kg (Kannan & Vimalkumar, 2021). Overall, it is reported that the human inhalation dosage of MPs for an adult varies in the range of 6.5–8.97 μg of MPs/kg of body weight-d. For infants and toddlers, the inhalation MP dosage is 3–50 times higher compared to adults (Wang et al., 2021). The estimated annual consumption of MPs ranges from 74,000 to 121,000 particles per person when both inhalation and oral intake of MPs are considered (Cox et al., 2019). Nevertheless, the dosage of MPs inhaled can differ based on the ventilation facility and the type of textiles used (Prata et al., 2020). Various estimates rely on sampling techniques and space utilization factors, including activities, cleaning schedules, season, and furniture materials. The properties of MP particles, such as size and density, affect the extent of MP deposition in the respiratory system. Smaller and less dense particles can reach deeper into the lungs. Following the deposition in the respiratory system, MP particles may be cleared by macrophages or transported to the circulation or lymphatic system, resulting in particle translocation. Nevertheless, the enhanced surface area of small particles triggers an intense discharge of chemotactic factors that hinder the migration of macrophages and enhance permeability, resulting in chronic inflammation, referred to as dust overload (Donaldson et al., 2000). In a study by Brown et al. (2001), it was observed that PS nanospheres with a diameter of 64 nm induced an expression of proinflammatory genes in epithelial cells as well as instigated neutrophil influx and inflammation in the lungs of rats. This could be attributed to the high oxidant activity due to the increased surface area of PS particles. Xu et al. (2002) reported that the in vitro production of PVC (2 μm) due to the emulsion polymerization exhibited considerable cytotoxicity in rat and human lung cells and caused hemolysis. The occupational exposure of the workers in the flock, synthetic textile, and vinyl chloride or PVC industries to airborne MPs can lead to the development of interstitial lung disease and airway, resulting in respiratory symptoms (Atis et al., 2005; Pimentel et al., 1975, Porter et al., 1999; Xu et al., 2004). In synthetic textile industries, MP fibers are released during the washing of textiles. It was reported that more than 700,000 MP fibers were released during the washing of 6 kg acrylic fabric (Xu et al., 2020), whereas the first wash cycle of PEST

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fabric resulted in the release of approximately 13 million MP fibers (Sillanpaa & Sainio, 2017). Prata (2018) observed that the workers in synthetic textile mills were more susceptible to developing respiratory diseases due to their exposure to airborne MPs. Turcotte et al. (2013) examined that the long-term exposure of flock workers to airborne MPs resulted in the development of various lung diseases, such as asthma and pneumoconiosis. Interestingly, the face mask, made of synthetic fibers, used during the COVID-19 pandemic might also lead to the inhalation of MPs originating from textiles. In a study by Pauly et al. (1998), the presence of MP fibers of 250 μm diameter was identified in human lung biopsies, including those taken from cancer patients. Similarly, Amato-Lourenco et al. (2021) reported the existence of PE and PP MP particles (< 5.5 μm) and fibers (8.12–16.8 μm) in human lungs. Hence, there is a possibility that under the circumstances of elevated MP concentration or enhanced individual vulnerability, airborne MPs may induce damage to the respiratory system. Finally, it can be stated that even though a few studies discussed the importance of indoor air and dust as the primary sources of human exposure to MPs through inhalation, the individual contribution of each source to the cumulative MP exposure is still unexplored. Additional investigation is required to accurately measure the amount of MP particles to which human beings are exposed through air inhalation and dust ingestion, as well as the corresponding health effects. Also, there is no comprehensive study undertaken to investigate the extent of human exposure to MPs from the use of synthetic textiles, which needs further attention from researchers to gain a better understanding.

13.2.3

Dermal Contact

Direct skin contact with MPs is regarded as a less significant route of human exposure to MPs owing to the inability of MP particles to percolate through the skin barrier (Schneider et al., 2009). However, speculations are there regarding the penetration of nanoplastics (< 100 nm) through the protective skin barrier (Revel et al., 2018). Plastic microbeads of size smaller than 1 mm have been extensively utilized as abrasive components in various cosmetic products such as exfoliating soaps, scrubs, sunscreens, skin creams, shower gels, shampoos, shaving foams, and liquid cosmetics (Cheung & Fok, 2016; Chowdhury et al., 2023; Dey Chowdhury et al., 2023). MPs are also present in hair dyes, hair bleaches, lip care products, deodorants, body lotions, and nail care products. Even the existence of MPs has been detected in toothpaste and composite dental fillings (Borrero-Lopez et al., 2019). MPs are incorporated into cosmetics to enhance skin exfoliation and cleansing, as well as to provide a smooth and silky texture, illumination, and control over viscosity (Kannan and Vimalkumar, 2021). The exposure to MP particles through dermal contact is commonly linked to the potential for individuals to come into contact with monomers and additives found in plastics, including endocrine-disrupting chemicals like bisphenol A and phthalates, through the regular usage of common household appliances (Chowdhury et al., 2022a, b; Dey Chowdhury et al., 2022; Prata et al., 2020). It is reported that in EU countries, a total of 4130 tonnes of microbeads are utilized annually in soap (Gouin et al., 2015). Around 93% of microbeads utilized in cosmetics are PE. Apart from that, PP, PET, PMMA, and nylon are also added to cosmetic products (Gouin et al., 2015). The proportion of microbeads in cosmetics varies from 0.05 to 12% (Gouin et al., 2015; Habib et al., 2020). Based on the concentration of PE MPs in liquid soaps, it is estimated that people in the

13.2 Pathways of Human Exposure to Microplastics

US are exposed to the contamination of PE MPs at a rate of 2.4 mg of PE particles capita−1 d−1 through dermal contact (Gouin et al., 2011). On the other hand, Napper et al. (2015) reported that the facial scrubs obtained from the UK embraced 1–10 g of PE microbeads/100 mL. Thus, the estimated per capita consumption of PE MPs through facial scrubs was 0.5–215 mg/d. Napper et al. (2015) also mentioned that approximately 4,594–94,500 microbeads were discharged into the aquatic environment when a facial scrub was used once. Considering the extensive prevalence of MPs in cosmetics, it is impossible to dismiss the possibility of dermal exposure to MPs (Anagnosti et al., 2021). Various cosmetics are directly applied to the skin, and the MP particles smaller than 100 nm can penetrate the epithelial barrier. The Federal Institute for Risk Assessment of Germany evaluated the MPs used in cosmetics for the possible health impacts. It was appraised that the MPs present in cosmetics could potentially damage the skin owing to inflammation and cytotoxicity. MPs also triggered oxidative stress in human dermal epithelial cells (Rahman et al., 2021). Protective mobile phone cases (PMPCs), after a long period of usage, can also be a potential source of MP contamination through dermal exposure (Li et al., 2023a, b). In a study by Li et al. (2023b), the potential of the PMPCs as a source of MPs was evaluated. It was observed that with the ageing and wear of the plastic cases, MPs were released from the PMPCs, and subsequently, transferred to the palm. The average concentrations of MPs on the PMPCs and the palm were 1,122 and 314 particles/cm2, respectively, and the corresponding mean diameters of the MP particles were 28 and 32 μm, respectively. The study was conducted for 3 months, and it was noticed that the generation of MPs from the PMPCs sharply increased after 33 days. The predominant types of MPs were PP, PS, PU, PET, and acrylonitrile butadiene styrene (ABS). Also, children may get exposed to the contamination of MP particles through dermal contact when they crawl or play in the ground or come in contact with indoor or outdoor dust particles containing MP particles in abundance (Li et al., 2023a). Plastics in the field of medicine are recognized for their ability to cause foreign body reactions and mild inflammatory reactions, resulting in fibrous encapsulation. For example, the use of braided monofilament PP and PEST for surgical sutures led to a reduced inflammatory reaction compared to silk and fibrous encapsulation at the end of 21 days (Salthouse & Matlaga, 1975). In a study conducted on mice by Van Tienhoven et al. (2006), PE and PVC plastic discs of size 3.5, 2.1, 2.02, and 0.33 MP particles/individual-d, respectively, by Abbasi and Turner (2021). Horvatits et al. (2022) collected liver tissue samples from 11 individuals, out of which 6 persons (4 males and 2 females) had liver cirrhosis disease, and the remaining 5 persons (4 males and 1 female) had a healthy liver. An average MP concentration of 4.6–11.9 particles/g of liver tissue was observed for the patients with liver cirrhosis disease, whereas the same for the persons with a healthy liver was 0.3–1.9 particles/g of liver tissue. The predominant types of MPs were PET, PS, PVC, PMMA, POM, and PP. The average concentration of the aforementioned MPs in the spleen tissues was 1.1 particles/g of spleen tissue; however, no trace of MPs was found in kidney tissues (Horvatits et al., 2022). In a recent study by Ragusa et al. (2021), human placentas obtained from six lady volunteers from Rome (Italy) were examined because MPs could adversely impact the growth of the fetus. The presence of 12 MPs (5 on the fetal side, 4 on the maternal side, and 3 in the chorioamniotic membranes) (5–10 μm) in four placentas was reported. This was the first study conducted on the detection of MPs in the human placenta. Later, Ragusa et al. (2022) first detected the existence of 12 MPs (2–12 μm), including PE, PVC, PP, ABS, PA, PC, PS, chlorinated PE, polyvinyl alcohol (PVOH), polyethylene-co-vinyl acetate (PEVA), polyethyl methacrylate (PEMA), and nitrocellulose (NC), in 26 out of 34 human breastmilk samples. The mean concentration of MPs in the breast milk was 0–2.72 MPs/g of milk. Similarly, in a study conducted by Zhu et al. (2023), the presence of MPs (20.34–307.29 μm) in 17 placental samples was detected. Moreover, 11 different types of MPs at an average concentration of 2.70 ± 2.65 particles/g were identified. The major types of MPs were PVC, PP, and polybutylene succinate. Liu et al. (2023) conducted a study in which 18 pairs of mothers and infants were enlisted. It was observed that 16 different types of MPs were present in the placenta, breast milk, meconium, infant feces, and infant formula, among which PA and PU MPs (20–50 μm) were predominant (> 74%). Generally, pregnant women and infants are vulnerable to MP toxicity (Sripada et al., 2022). The presence of MPs in the human placenta signifies their nondegradable nature and potential to impact future generations by affecting the development of the fetus. Therefore, it is crucial to give more attention to the possible consequences of the early development of embryos and exposing infants to MPs. Moreover, substantial evidence is available on the exposure and accumulation of MPs in human tissues. MP particles with a size smaller than 100 μm possess the ability to pass through the cell membranes of exposed cells, tissues, and organisms. In addition, particles smaller than 20 μm can be effectively migrated to different organs. Despite being in the early stages, current research indicates an urgent requirement for a detailed investigation of the consumption and accumulation of MPs and the corresponding health consequences in human beings.

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13.6

Conclusions

This chapter explores the potential pathways of human exposure to MPs and the possible toxic effects of MPs on human health. In addition, a brief discussion on the use of biomarkers to have a clear understanding of the underlying mechanisms of the toxic effects of MPs on different organisms has also been included. Furthermore, a few recent case studies on human exposure to MPs are also presented. The three major pathways through which MPs enter human bodies are ingestion, inhalation, and dermal contact. The consumption of seafood, vegetables, fruits, packaged drinking water, table salt, sugar, honey, alcohol, and packaged meat items increases the risk of MP contamination in human bodies. Human beings also get exposed to MP particles through the inhalation of indoor and outdoor dust particles. Even the use of cosmetics and plastic mobile covers causes the entrance of MPs to human bodies via dermal contact. People working in the textile, flock, and PVC industries also get exposed to airborne MPs. Exposure to MPs engenders inflammatory lesions, oxidative stress, cytotoxicity, disruption of energy homeostasis, metabolic disorders, genotoxicity, neurotoxicity, destruction of immune function, as well as reproductive and developmental toxicity in various organisms, including human beings. However, owing to the ethical limitations and strict biosecurity protocols for handling human samples, instances of toxic effects on human beings due to exposure to MPs are scarce. Most of the toxicity studies of MPs have been performed on marine and freshwater organisms and mice. Among various biomarkers explored to elucidate the MP toxicity on organisms, antioxidant enzymes, LPO, DNA strand breaks and FMN, AChE enzymes, and IDH and LDH enzymes are most frequently used to express oxidative stress, oxidative damage to lipids, genotoxicity, neurotoxicity, and metabolic disorders, respectively. Mostly, exposure to MPs suppresses the activities of AChE and IDH enzymes but stimulates the activities of antioxidant enzymes and LDH enzymes. A few studies on the inhibition of the activities of antioxidant enzymes due to exposure to MPs are also available. Furthermore, MPs enhance the level of LPO, DNA strand breaks, and FMN. Recent studies revealed the presence of MPs in blood, lung tissues, liver, spleen, colon tissues, placenta, hair, hand, face skin, saliva, breast milk, meconium, and feces of human beings. Pregnant women and infants are more susceptible to MP toxicity. Hence, extensive research on the toxic effects of MPs on human beings, including infants, should be carried out to clearly understand the risk of human exposure to MPs.

References Abbasi, S., Keshavarzi, B., Moore, F., Turner, A., Kelly, F. J., Dominguez, A. O., & Jaafarzadeh, N. (2019). Distribution and potential health impacts of microplastics and microrubbers in air and street dusts from Asaluyeh County, Iran. Environmental Pollution, 244, 153–164. Abbasi, S., & Turner, A. (2021). Human exposure to microplastics: A study in Iran. Journal of Hazardous Materials, 403, 123799. Abidli, S., Antunes, J. C., Ferreira, J. L., Lahbib, Y., Sobral, P., & El Menif, N. T. (2018). Microplastics in sediments from the littoral zone of the north Tunisian coast (Mediterranean Sea). Estuarine, Coastal and Shelf Science, 205, 1–9.

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14 Plastic Pollution Management—Innovative Solutions for Plastic Waste Saikat Sinha Ray1∗, Randeep Singh2∗, Mahesh Ganesapillai3,4, and Young-Ho Ahn2 1

Department of Environmental Science and Engineering, School of Engineering and Sciences, SRM University-AP, Amaravati, Andhra Pradesh, India 2 Department of Civil Engineering, Yeungnam University, Gyeongsan, Republic of Korea 3 Mass Transfer Group, School of Chemical Engineering, Vellore Institute of Technology, Vellore, Tamil Nadu, India 4 Department of Technologies and Installations for Waste Management, Faculty of Energy and Environmental Engineering, Silesian University of Technology, Gliwice, Poland

14.1 Introduction There are huge amounts of solid wastes in this world, which include plastic, food, tires, woody biomass, biomedical, and animal manure. Among these wastes, particularly plastic receives high criticism due to its environmental impact. Due to their lightweight, low cost, and high performance, plastic materials are usually utilized for packaging. Polypropylene and polyethylene are some of the most used plastic materials for packaging and other applications. Nevertheless, the high longevity of the used plastics leads to a huge amount of waste accumulation in oceans and landfills. In general, the synthetic polymers are designed for durability rather than degradability and recyclability. As far as global waste is concerned, single-use plastics play a significant role in the contribution to worldwide waste. Recent data suggest that, approximately 280 million tons of plastics have been produced worldwide and only less than 20% is recycled, which leads to environmental pollution and global waste. Typically, recycling is tedious and difficult due to the presence of different contaminants, including liquid, food (organic), and inks (inorganic) (Hahladakis et al., 2018; Rigamonti et al., 2014; Welden, 2020). For instance, liquids may cause cardboard and paper to become soggy, which makes them tough to recycle and recover. Liquids can also contaminate other recyclable products such as metals and plastics. Even food residues can attract insects and pests and result in odor issues. Additionally, inks can interfere with the recycling process and can degrade the quality of the recycled products. Nearly half of all plastic produced since 1950 ( 9.2 billion tons) is single use, meaning it is thrown away after one use (Geyer et al., 2017). When plastic waste is not disposed of properly, it can end up in the ocean, where it can harm marine life and humans. Plastic additives ∗

Both authors have contributed equally.

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Table 14.1 Point of Origin of Various Plastic Wastes Type of plastic waste

Point of origin

LDPE: Low-density polyethylene

Carry bags, shopping bags, milk pouches, cosmetics, and detergent powder

HDPE: High-density polyethylene

Carry bags, household articles, and bottle caps

Polyethylene terephthalate (PET)

Drinking bottles and soft-drink bottles

Polypropylene (PP)

Bottle caps, wrappers of biscuits, cakes, cookies, wafers, and detergents

Polystyrene (PS)

Bottle caps and egg packs

Foamed polystyrene (F-PS)

Disposable cups, food trays, and protective packaging materials

Polyvinyl chloride (PVC)

Mineral water bottles, pipes, credit cards, electrical fittings, furniture, and medical disposables

in marine debris can be toxic and can even accumulate in our bodies (Ding & Zhu, 2023). Table 14.1 demonstrates the plastic waste and its point of source. Out of the estimated 9.2 billion tons of plastic waste since 1950, only 9% of it is recycled. The rest ended up in landfills or the ocean. Plastic consumption has increased dramatically in recent years, from about 2 million tons in 2011 to 320 million tons in 2015. Global plastic production has also doubled over the past 20 years, to about 335 million tons. And it’s expected to reach at least 600 million tons by 2030. Plastic waste accumulation is increased to very high levels in the environment, showcasing harmful impacts on both the environment and human health. Plastic takes centuries to degrade, but due to its versatility, it has become an essential part of our modern lifestyle. The disposal and production of plastic is harming the environment. Figure 14.1 shows the life cycle of plastic, from manufacturer to consumer to disposal or recycling. The figure shows that plastic and plastic products now make up a significant portion of municipal solid waste (MSW), and they persist as hazardous materials. The high percentage of plastic waste in MSW also indicates poor waste management and a lack of effective rules and regulations. Plastics cannot be easily broken down by nature and do not return to the carbon cycle. This is why they end up on land or in the ocean at the end of their life cycle (Nielsen et al., 2020). There are several methods for disposing of plastic waste, including conventional methods, such as incineration, landfilling, and chemical recovery, and more advanced methods such as microwave- or plasma-assisted conversion, hydrocracking, gasification, chemolysis, and polymer design and modifications as shown in Figure 14.2. Proper plastic waste management is a key challenge in waste management, and it has both environmental and economic impacts. In the early 2000s, most plastic waste was disposed of in landfills (65–70%) or incinerated (20–25%), with only about 10% being recycled. However, this situation varies from country to country, depending on the standard of living and population (Masud et al., 2019; Mourshed et al., 2017). A survey of peer-reviewed articles related to plastic pollution over the last 20 years has been executed, which is indicated in Figure 14.3. In addition to that, the contribution of

14.1 Introduction

Raw material

Disposal

Manufacturing

Use

Packaging

Distribution

Figure 14.1

The Life Cycle of Plastic Which Initiates from Raw Materials and Terminates at Disposal

research work based on microplastic and plastic pollution from different countries, in terms of publications, is demonstrated in Figure 14.3b. Interestingly, it was observed that China is leading the table as per the database acquired from Scopus Advanced Search System. The data clearly demonstrates that microplastic and plastic pollution have attracted attention from the research fraternity. Figure 14.3c shows that the research article is leading the table followed by review articles and book chapters. Therefore, it is crucial to discuss solid waste management scientifically and critically as far as plastic pollution is concerned. There is a need to design new products for recycling by using fewer materials and making them easier to recycle. Also, it is needed to anticipate new technologies for identifying and sorting plastic waste, as well as chemical recycling. Further, biodegradation of the small fraction of plastic products that will still end up in the environment. Waste sorting will improve with new technologies, such as watermarks and AI (Bharti et al., 2022; Ray et al., 2023a, 2024; Reza et al., 2024). However, one should not forget about cleaning and conditioning technologies. Mechanical recycling has been limited to downcycling a small

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14 Plastic Pollution Management—Innovative Solutions for Plastic Waste

Methods

Mechanical

Chemical

Thermal

Biocatalytic

Available treatment processes

• Segregation • Grinding • Crushing • Reprocessing

• High temperature • Incineration

• Acid • Alkali • Aminolytic treatment of wastes

• Use of plastic hydrolases at high temperature

Outcomes

Recycled plastic of poor quality

Figure 14.2

Generation of toxic gases

Use of harmful chemicals make it unsustainable process

Eco-friendly plastic products

Schematic Representation of Methods for Recycling Various Plastic Products

fraction of plastic waste and producing resins with low recycled content. Chemical recycling is likely to take over where mechanical recycling struggles, such as in delivering top-grade products and recycling mixed, contaminated, or degraded reject streams. Many chemical recycling technologies are now close to deployment, and they can recycle plastic waste into monomers or feedstock. The plastic waste that chemical recycling cannot recycle will eventually need to be disposed of responsibly. Landfilling could be considered a responsible carbon sequestration in areas with plenty of land, as long as it is done in a way that prevents toxic leachate from contaminating the soil and aquifers and prevents biomethane from leaking into the atmosphere. In all other cases, the most responsible option is likely to be incineration, such as direct incineration, indirect incineration that also helps in energy recovery via biogas or syngas, or conversion to fuels (Zhang et al., 2022). However, it will be important to compensate for the carbon that is refused and disposed of by introducing fresh carbon into the cycle. This carbon may come from fossil resources for a while, but eventually, it needs to come from renewable carbon, such as atmospheric CO2. This can be achieved through carbon capture and utilization, but in the short to medium term, it is likely to come from biomass.

Number of publications

(a) 30,000 25,000 20,000 15,000 10,000 5,000 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003

0

Year

(b)

China Italy

United States Germany

Australia

South Korea

India Spain

United Kingdom Canada

(c)

Article

Review

Book chapter

Conference paper

Book

Note

Editorial

Short survey

Letter

Data paper Figure 14.3 (a) Survey of Peer-Reviewed Articles Since 2003. (b) Contribution of Different Countries to Plastic Pollution Research and Development. (c) Comparative Analysis of Types of Articles Published Since 2003. (Note: Data analysis of publications is done using Scopus Advanced Search System with the terms “Plastic” and “Pollution” as of November 2023)

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14 Plastic Pollution Management—Innovative Solutions for Plastic Waste

This book chapter will discuss the recent progress in minimizing plastic pollution. The future directions for the conversion of plastic waste to high-value products will also be addressed. The book chapter specifically deals with the concept of conventional and advanced recycling methods. More emphasis has been given to the design and production of polymers for the subsequent conversion of plastic waste. A comparative study is presented based on reuse and recycling methods concerning economic viability. The importance of awareness and education is also presented in this book chapter. This book chapter can be considered as a fundamental attempt to establish a concept of reducing, reusing, and recycling plastic that is required for safeguarding the environment. Moreover, suggestions for future research and development are also emphasized.

14.2

Design and Production

This section deals with the design and production formulation of sustainable plastics from a chemical perspective and demonstrates an overview of the simplified design and biodegradable plastics. Typically, the production of plastic products does not take sustainability into account. Sustainable plastics are those plastic products that offer societal benefits while improving human and environmental safety and health across the product life cycle. Sustainable plastic should have minimized negative impact on climate and should meet the aim of sustainable development goals given by the United Nations (Küttner et al., 2007). The main challenge in the production of sustainable plastic products depends upon the production of sustainable materials. Figure 14.4 demonstrates that the production of sustainable plastic revolved around the system, material, product, and chemical aspects. All these factors are interrelated for the successful design and production of sustainable plastic products. The production of sustainable plastic products depends on complex relations between four aspects such as system, material, product, and chemicals. Herein, the system refers to the whole life cycle of the plastic product, considering everything from extraction of raw materials to production, use, disposal, and recycling. Whereas material refers to the selection of plastic type, for example sustainable plastic includes bioplastics which are derived from renewable sources. As far as the third aspect is concerned, the product represents the design and engineering of plastic which significantly influences sustainability. Lastly, chemicals demonstrate the use of chemicals during plastic production that significantly influences

System

Plastic products

Materials

Chemical perspectives

Figure 14.4 Interrelationship of System, Material, Product, and Chemical Aspects while Production of Sustainable Plastic Products

14.2 Design and Production

sustainability. Therefore, by considering all four aspects, manufacturers can create sustainable plastic products and reduce the environmental impact throughout their life cycle.

14.2.1

Using Different Synthetic Materials

Chemical recycling of plastics, such as mechanical recycling, solvent separations, and deconstruction or depolymerization, offers advantages but faces challenges, such as catalyst tolerance to impurities (Fagnani et al., 2020). Plastic recycling is a step in the right direction, but we need to do more to reduce our reliance on plastic and develop more sustainable alternatives. Enhancing the resilience and extending the service life of existing plastics can significantly reduce our reliance on new resources. One example is the development of compatibilizers that improve the tolerance of polyolefins to impurities in recycled plastics, preserving their properties, and preventing phase separation (Eagan et al., 2017). Additionally, researchers are pursuing self-healing materials that can be repaired in operation to extend their overall lifespan. However, these dynamic polymer systems often face challenges with creep resistance and fracture toughness at lower temperatures, prompting ongoing research to address these limitations (Guerre et al., 2020). To minimize fossil fuel dependence and address plastic waste concerns, there has been a notable transition toward plastics derived from renewable resources (Korley et al., 2021). From a recycling/upcycling perspective, bio-based materials can be classified into two main categories. The first category consists of bio-based polymers with monomers that are chemically indistinguishable from their petroleum-based counterparts, examples being (bio)polyisoprene (Abdelrahman et al., 2017) and (bio)polyethylene (Mendieta et al., 2020). The second category encompasses bio-based polymers with unique monomeric and macromolecular structures compared to their petroleum-derived alternatives. The widespread adoption of bioplastics is hindered by several challenges. One challenge lies in synthesizing and manufacturing bioplastics that match the properties of conventional plastics while maintaining biodegradability. Furthermore, the cost of biomanufacturing processes often exceeds that of petroleum-based plastic production, making bioplastics less competitive in the market (Lamberti et al., 2020). To overcome these challenges, it is crucial to deepen our understanding of the relationship between feedstock selection, performance characteristics, component toxicity, and environmental impact. This knowledge will aid in developing truly sustainable bioplastics that can compete effectively with petroleum-based plastics. Lignocellulosic waste, a nonfood biomass source, holds promise for bio-based plastic production. While lignin extraction variations may necessitate specialized separation techniques, recent catalytic deconstruction advancements have yielded cost-competitive aromatic building blocks. These blocks can replace bisphenols in thermoplastics, offering comparable or superior performance, and reduce potential toxicity. The inherent hydroxyl functionality further enhances materials’ development options. However, inherent biodegradability or recyclability in lignin-derived materials remains a challenge. Nevertheless, bio-based plastics’ ability to sequester carbon dioxide or carbon necessitates end-of-life greenhouse gas release assessments.

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14.2.2

Simplified Design of Products

Addressing the issue of plastic waste stands as a paramount and urgent global challenge. To mitigate the environmental impact of plastic, the initial stride involves minimizing its usage in our everyday lives. Manufacturers play a pivotal role in this endeavor by devising strategies to curtail plastic usage throughout the entire life cycle of products, from creation to disposal. Typically, changing the design of plastic products can benefit plastic management issues in several ways. Various plastic products are made up of a combination of different types of materials and plastic which make them tough to recycle. In other words, designing plastic products utilizing a single type of plastic or fewer materials can make it easier to recycle. However, certain types of plastics are difficult to disassemble, making it difficult to separate various materials for recycling purposes. Thus, designing plastic products in such a way that it can facilitate the separation and recycling of different materials. This is very crucial for complex items such as electronic appliances. Figure 14.5 shows different aspects of product design for plastic reuse and reduction. In recent times, there has been a shift toward employing biodegradable granules instead of microplastics in the manufacturing of cosmetic packaging materials, alongside the adoption of recycled plastic for the same purpose. Innovative designs include refillable containers, where only the inner container needs replacement post-use, while the outer container can be reused. The inner container comprises 97% recycled plastic, and the outer container is crafted from 60% recycled glass, contributing to an overall reduction in plastic consumption. Initiatives like these, promoting the increased use of recycled plastic and the implementation of lightweight packaging, are crucial for a substantial decrease in plastic usage. Importantly, recycled plastic should undergo aesthetically pleasing regeneration to enhance its utilization. Moreover, the development of sustainable products in collaboration with consumers is essential to enhance the eco-friendly attributes of items. This involves incorporating

Designing the products: • Durable • Repairable • Reusable

Make products: • Recyclable • Simplify material Formulation

Introduction of products: • Ensure traceability • Second life for recycled products

Focus chemical aspects: • Strictness in chemical usage • Reduce exposure

Figure 14.5 Schematic Representation of Different Aspects of Product Design for Plastic Reuse and Reduction

14.2 Design and Production

sustainable elements such as recycled plastic and paper into products through customer engagement programs. Such initiatives serve to educate customers, fostering active participation in reducing both plastic usage and waste. The incorporation of recycled content necessitates a policy framework stipulating a minimum percentage of recycled material in a product or substance. Industry-led initiatives involve collaboration among producers, such as manufacturers, brand owners, and initial importers, to establish collection and recycling programs for specific products at the end of their life cycle. These programs, although not mandated or regulated by governments, operate independently without governmental involvement (Giroux, 2014). Designing eco-friendly products: Crafting environment-friendly products involves minimizing the use of plastic in the item and enhancing its reusability, repairability, composability, or recyclability. Bulk or refill commercialization: A business model that promotes the use of durable alternatives by employing refillable containers for products typically sold in disposable packaging. Distinctive business approach: Substituting single-use and disposable items with more durable options to enhance reuse, repairability, compostability, or recycling. Cataloging: Labels can serve to distinguish products in a category with exemplary environmental performance or provide guidance to the public regarding safe practices and suitable end-of-life management. Advertisement and edification: Initiatives for promotion and education aim to raise awareness about waste prevention, reduction, and recycling efforts. Event and public retrieval system: Infrastructure or systems for collection accessible in public spaces or during public events. Government and industry agreements: Collaborative arrangements between the government and industry involve voluntary agreements, codes, or memoranda of understanding aimed at promoting products, materials, or practices that are environmentally less harmful or more easily recyclable. These agreements generally establish overarching goals while granting the private sector the flexibility to determine the means of achieving them.

14.2.3

Using Biodegradable Plastic

The excessive use of plastic material is of great concern, if not handled appropriately in our society. Although plastic has emerged as a highly valued material for long-lasting functional use, however, it has been criticized due to plastic related environmental hazards and the energy crisis. Nowadays, customers and consumers are well aware of the harmful negative impacts of plastics. Therefore, bio-based and biodegradable polymeric materials are one of the solutions to the present plastic related environmental impacts. The term “bio-based” indicates a polymer that is made partially or fully from biomass that includes organic materials of biological origin. Whereas the term “biodegradable” indicates the ability of a material to degrade into natural components due to the action of microorganisms. In the present scenario, biodegradable or bio-based plastic can be considered as one of the alternatives to achieve sustainable growth of the plastic industry in the near future. This will minimize the waste volume of single-use plastic in the environment. Furthermore, bio-based or

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biodegradable plastic could serve as a feasible solution to overwhelmed landfills. Typically, bio-based and biodegradable plastic could decompose into carbon dioxide and water in 20–25 days under favorable conditions (such as humidity, oxygen, and appropriate numbers of microorganisms that are generally available in landfills), whereas single-use plastic materials decompose in 100 to 1,000 years which indirectly has a negative impact on the environment. Thus, bio-based and biodegradable plastics can be used instead of traditional plastics. The biodegradable plastic shows limited mechanical strength that restricts its application and usage. Synthetic fibers such as carbon fibers and glass components are used to provide high mechanical strength to bioplastics. Nevertheless, these components are not biodegradable. In recent research, it has been revealed that more eco-friendly and low-cost materials such as lignin and lignocellulosic fibers may replace the nonbiodegradable components (Aminabhavi et al., 1990; Flury & Narayan, 2021). In addition to that, ultrasound application, dehydrothermal treatment, and mold temperature rise may strengthen the physical aspect of the plastic material. Apparently, in recent years there has been a growth in interest in synthesis and usage of bioplastics which turned out to be an alternative to conventional packaging materials. Typically, bioplastic or biodegradable plastics are made up of plants such as sugarcane and converted into various polymeric materials such as polyhydroxyalkanoates (PHAs) and polylactic acids (PLAs) (Dilkes-Hoffman et al., 2019; Shen et al., 2020).

14.3

Packaging and Distribution

Before interpreting the details of packaging and distribution of plastic materials, we need to understand the versatility of plastic as a packaging material. Typically, plastic materials are utilized due to a unique combination of advantages including durability, safety, hygiene, security, lightweight, and design freedom. Thus, there is an increased usage of plastic materials in packaging industries. However, plastic packaging has been criticized for its negative environmental impact. Interestingly, plastic material was originally discovered as a breakthrough material when it was first produced. Nevertheless, due to the negative impact on the environment and plastic pollution, plastic material for packaging and distribution has been demonized. The issue with plastic material for packaging and distribution is that it takes more than 1,000 years to degrade naturally. Therefore, the same plastic materials end up in various water bodies such as lakes, rivers, and oceans leading to plastic and microplastic pollution. Plastic and microplastic pollution results in the loss of wildlife (Ray et al., 2022). With the increasing world’s population, there is an increase in plastic waste as well which is growing exponentially. In simple words, recycling single-use plastic or plastic barrels is the key solution (Groh et al., 2019; Van et al., 2018). This section will discuss the minimization of single-use plastic packaging materials and how banning certain plastic products may help in achieving sustainable development.

14.3.1

Reduction of Single-Use Plastic Packaging

It should be accepted that plastics became a serious issue for planet Earth. Thus, governments are coming forward and proposing various measures to minimize the impact of plastic pollution on the environment. The consumption of plastic has increased dramatically in

14.3 Packaging and Distribution

the last seven decades and is expected to increase further. The disposal of plastics emerges as a significant issue. Unfortunately, a limited amount of plastic waste is recycled because of recycling contamination, and consequently, the majority of the plastic waste is diverted to landfills or littered in the open natural environment which has a negative impact on human health as well as the environment (Rabiu & Jaeger-Erben, 2024). Therefore, there is a need for urgent intervention to minimize the consumption of single-use plastic. However, recycling can be one of the fundamental solutions which can ultimately reduce the footprint (Dey et al., 2021). For instance, PET plastic material is one of the most recycled materials. Usually, PET plastic materials are used to produce water and soda bottles which can be converted into everything from polyester fabric to automotive parts (Chen et al., 2021). Hence, policies, laws, and acts must be made to ensure sustainable management of plastic waste. This will ensure the collection, segregation, storage, transportation, disposal, and recycling. Typically, systematic strategies are required at various levels of plastic management which are as follows (Evode et al., 2021; Rigamonti et al., 2014; Siddiqui & Pandey, 2013; Singh & Sharma, 2016): a) Prevention of plastic consumption by putting restrictions and banning of certain singleuse plastics; b) Improvement in collection infrastructure; c) Improvement of resource productivity by minimizing the plastic waste; d) Control strategies by defining proper protocols, standards, and guidelines; e) Setting up of mentality of reusing plastic products; f) Non-plastic alternatives must be used and encouraged for a sustainable environment; and g) Education and awareness regarding plastic consumption and waste management.

14.3.2

Bans of Some Plastic Items

A study reveals that over 57 million pounds of personal protective equipment (PPE) and other plastic waste linked to COVID have contaminated the oceans since the onset of the pandemic (Peng et al., 2021; Ray et al., 2023b). The COVID-19 pandemic’s relentless tide of single-use plastic has exacerbated the plastic pollution crisis, reaching catastrophic levels (Ganesapillai et al., 2022). The study exposes the shocking reality that over 8 million tons of pandemic-related plastic waste was generated globally, with more than 25,000 tons clogging the oceans. Shockingly, medical waste from overwhelmed hospitals dominates this plastic surge, dwarfing the contribution of PPE, and online shopping packaging. This poses a dire and enduring threat to marine ecosystems, with most of this plastic accumulating on vulnerable beaches and coastal sediments (Hiemstra et al., 2021). In a bold move to combat plastic pollution, governments across the globe are announcing that they will eliminate the sale of single-use plastic products (Herberz et al., 2020; Macintosh et al., 2020; Nøklebye et al., 2023). This decisive action addresses a significant source of plastic waste as the nation’s recycling rate stagnates. Aiming to alleviate the staggering 14 million tons of plastic entering the ocean annually, this directive defines and phases out single-use plastic within national parks and public lands. This initiative represents a significant step toward curbing plastic pollution and protecting the environment.

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In addressing the plastic pollution crisis, it is imperative to prohibit the sale of plastic packaging that cannot be efficiently recycled. Given the challenges faced by current recycling methods in handling complex materials, this encompassing measure would compel a shift toward compostable or genuinely reusable alternatives, thereby paving the way for a cleaner future. Following are a few key points showcasing the overall picture of the plastic ban. Current recycling challenges

•• •

Recycling facilities often lack the technology to handle complex plastic types. Contamination during sorting and collection further reduces the amount of plastic that can be recycled. The global recycling rate for plastic remains alarmingly low, hovering around 9%.

Benefits of banning nonrecyclable plastic packaging

•• ••

Drastically reduce plastic pollution in our environment. Encourage innovation in sustainable packaging solutions. Promote a circular economy where materials are reused and repurposed. Protect wildlife and ecosystems from the harmful effects of plastic pollution.

Transitioning to eco-friendly alternatives

• • •

Compostable packaging: Made from natural materials such as plant fibers, these decompose quickly and safely in compost piles. Reusable packaging: Bottles, bags, and containers designed for multiple uses significantly reduce waste generation. Innovative packaging materials: New technologies are constantly emerging, paving the way for more sustainable packaging options. Importantly, the following points are required to impose a plastic ban effectively.

Make it easy to use alternatives

•• ••

Promote readily available and affordable compostable and reusable alternatives. Provide clear labeling and educational materials to guide consumers. Invest in infrastructure for collecting and processing compostable materials. Offer incentives to businesses and consumers to switch to eco-friendly options.

Phase in the ban

•• ••

Start with a limited list of easily replaced items. Expand the ban gradually over time to allow for adaptation and innovation. Provide ample time for businesses and consumers to adjust to the new regulations. Offer technical assistance and resources to support the transition.

Involve the public

••

Raise awareness about the plastic pollution crisis and the need for change. Engage stakeholders through public hearings and community forums.

14.3 Packaging and Distribution

••

Partner with environmental groups and businesses to develop and implement the ban. Empower consumers to make informed choices and hold businesses accountable.

By considering these three principles, we can ensure a successful and sustainable transition away from nonrecyclable plastic packaging.

14.3.3

Better Labeling of Cosmetic and Cleaning Products

Plastic’s adaptability and affordability have made it a ubiquitous material across countless industries. However, the very strengths of plastics can turn into weaknesses if not managed properly. Improper disposal can lead to significant environmental and waste concerns. Recycling is key to mitigating these impacts, and clear labeling is essential for guiding efficient recycling practices (Laubinger & Börkey, 2021). 14.3.3.1

Plastic Types and Their Recycling Codes

Hidden in plain sight, on countless plastic products, lies a secret language waiting to be deciphered. Nestled within the familiar recycling triangle symbol, a number whispers the identity of the plastic you hold. This “recycling code,” ranging from 1 to 7, unlocks the secrets of its recyclability and paves the way for responsible disposal. Recycling code 1: This code pertains to PET, also known as polyethylene terephthalate plastics, commonly employed in the production of water bottles. It represents the most readily recyclable form of plastic. Recycling code 2: The provided numerical code corresponds to HDPE, which stands for high-density polyethylene plastic. Frequently utilized for cosmetics containers, this type of plastic shares a high recyclability characteristic with PET. Recycling code 3: The specified code pertains to PVC, or polyvinyl chloride, commonly employed in plastic pipes and panels. To facilitate recycling, it is essential to segregate PVC from other plastics, as it requires individual processing. Recycling code 4: This code pertains to LDPE, standing for low-density polyethylene, a pliable plastic frequently found in plastic shopping bags. To undergo recycling, it is necessary to first remove a layer of film from the material. Recycling code 5: The provided code corresponds to PP, or polypropylene, a type of plastic utilized in medication bottles and specific packaging. Its recycling is relatively limited as the process involves extensive labor and multiple stages. Recycling code 6: The assigned code pertains to PS, known as polystyrene, commonly employed as a packaging material for food and beverages, such as coffee cups. It typically does not undergo regular recycling processes. Recycling code 7: Lastly, there are other types of plastics used for diverse packaging applications, such as polycarbonates. These plastics are considered among the most challenging to recycle and are labeled with the recycling code 7. 14.3.3.2

•

Advantages of Labeling Plastics

Time efficiency—Clear and easily understandable plastic labels and recycling bin labels can save consumers time when sorting and disposing of products into the appropriate bins and containers.

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• • • •

Eliminate confusion—Consumers often face confusion regarding recyclable and nonrecyclable plastics. Clear labels on each product help eliminate any uncertainties or misunderstandings. Environmental consciousness—Many consumers aspire to live greener and more ecofriendly lives, but inadequate labeling hinders their efforts. Improved labeling standards can facilitate easier recycling for everyone, contributing to waste reduction and environmental awareness. Waste reduction—In the absence of proper labels on plastic products, they frequently end up in landfills, exacerbating global waste issues that pose threats to ecosystems. Enhanced environmental hygiene—Improved labeling ensures that less plastic waste contaminates the world’s waters and green spaces. This results in safer environments for local flora and fauna, fostering the prosperity of the natural world.

14.3.3.3 Disadvantages of Labeling Errors on Efficient Recycling

• •

Improper disposal—Labeling mistakes often lead to incorrect disposal practices, with recyclable plastics such as PET and HDPE ending up in regular trash or challengingto-recycle plastics getting mixed with others. Resource wastage—When challenging-to-recycle plastics (e.g., those labeled with codes 4–7) are intermingled with others, significant time and effort is squandered in the separation process before they can undergo proper recycling.

14.3.3.4 Optimal Approaches to Plastic Labeling

To address the aforementioned mistakes and challenges, it is essential to consistently adhere to the highest standards of plastic labeling. The following are key strategies for enforcing proper plastic labeling. 14.3.3.5 Accurate Identification of Plastic Types

The plastic code system proves invaluable to consumers and recycling organizations. Ensuring that every plastic product carries a label specifying its plastic type and recyclability is crucial. 14.3.3.6 Adoption of Standard Labeling Practices

Businesses should adhere to standardized labeling practices for all plastic products. Establishing a universal standard simplifies understanding and compliance with plastic labels, minimizing confusion, and reducing waste. 14.3.3.7 Clarity and Uniformity in Plastic Item Labeling

All plastic labels should be clear and easily legible. The information conveyed should be readily accessible to anyone, free from distracting graphics, confusing fonts, or awkward placements. This ensures that individuals can quickly locate and comprehend the label, facilitating proper recycling practices. 14.3.3.8 More Reuse of Plastics

In the United Nations report titled, “Turning off the Tap,” the key to ending plastic pollution lies in transitioning from a linear to a circular economy (Fletcher et al., 2023). Research indicates that implementing reuse systems presents the greatest potential for reducing plastic

14.3 Packaging and Distribution

pollution, with a projected 30% reduction by 2040. This involves replacing some of the most problematic and unnecessary products. Approximately 70% of the reduction in plastic usage can be achieved through the adoption of reuse, refill, and innovative delivery models. By reusing products, we prolong their lifespan and diminish the necessity for producing new plastic. This practice offers several advantages, including diminishing the volume of plastic waste entering the environment, conserving energy and resources, lowering greenhouse gas emissions, and safeguarding wildlife and ecosystems. Table 14.2 showcases the application of design to enhance the recycling of plastic packaging that helps to curb plastic waste. Table 14.2

Application Cases of Design for Recycling of Plastic Packaging

Original design Improved design

Barrier layer

Aluminized PET multilayer composites

Soft tube, Monopolyolefin HDPEa, PET, and blister pack, PP skin packaging, and packaging film

Toothpaste, cosmetics, cheese, fruit paste, vegetable paste, and milk powder

Nestle, Colgate, Essel, and Gerber

Adhesive

Solvent based/ pressure sensitive/melt adhesive

Washable adhesive, selfadhesive, nonglue structure

Daily chemical/ beauty products, drinks/milk, machine oil, and commodity

UPM, Raflatac, Avery, Dennison, China Post, and Amazon

Label

PVC shrink label, paper label, and multilayer label

PET shrink label, Bottle, container, and PETGa shrink label, wood-based flexible pack PE, Peelable label, no label, label reduction, laser printing and embossing, and electronic tag

Mouthwash, coffee/tea/juice, carbonated/ isotonic drinks, and gum

ORION, Darlie, Master Kong, Eastroc Beverage, Coca-Cola, Pepsi, Pulpy Orange, and Evian

Pump

Metal spring, All-plastic pump, Bottle and metal/glass 100% PP, 100% container bead, and PP/ PE, and PP/r-PP PE

Daily chemical/ cleaning products, medicine, and skincare

Tianzhou, Aptar Group, Berry Global, and Rieke Packaging

Color

Green/blue, white/black, and opaque

Bottle

Coffee/juice, carbonated drinks, milk/tea, daily chemical, and skin care

Spite, Fido, Amcor, Unilever, and Cnnice

Bottle and soft bag

Drinks and sauce

Alpla, Sidel, Coca Cola

Transparent and unpigmented

Attachment Separated cap Attached cap, and EVAa, and TPEa aluminum foil a

Packaging form

Applicable products

Component

Bottle, bucket, can, flexible package, express package

Brand name

HDPE, PETG, EVA, and TPE are the abbreviations for high-density polyethylene, polyethylene terephthalate G copolyester, ethylene vinyl acetate copolymers, and thermoplastic elastomers, respectively.

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14 Plastic Pollution Management—Innovative Solutions for Plastic Waste

Various policies can expedite the promotion of reuse as discussed below: Deposit return schemes: These initiatives necessitate consumers to pay a deposit when purchasing certain single-use containers, such as beverage bottles and cans. Upon returning the containers, the deposit is refunded. Packaging takeback programs (PTP): Businesses are obligated to collect and recycle packaging waste under PTP. This approach has demonstrated effectiveness in curbing plastic pollution. Government procurement policies: Governments can incentivize businesses to adopt reusable products through procurement policies. Taxes and subsidies: Levying taxes on disposable products and providing subsidies for reusable alternatives can alter the affordability dynamics. Public education campaigns: Raising awareness about the benefits of reuse and the issues associated with plastic pollution through public education campaigns is crucial. Reducing dependence on single-use plastics and promoting reuse is imperative for combatting plastic pollution. Accelerating reuse through these measures contributes to building a more sustainable future for our planet. 14.3.3.9 Increased Reparability/Longevity of Products

Utilizing life-cycle thinking and leveraging insights from the expanding body of literature on plastics, the framework assesses plastic items based on their “use phase.” This refers to the duration for which a specific plastic item serves its intended purpose. This approach is significant as it acknowledges that the lifespan of an item is closely linked to two key factors: the typical disposal method of the product and the potential measures one can undertake to mitigate adverse impacts throughout its entire life cycle. Following are five categories in which the plastic items are grouped. Category I: This category encompasses small-format items with an extremely brief use phase, typically lasting less than a day, sometimes mere hours, minutes, or even seconds. Examples include cotton buds, coffee stirrers, straws, and sanitary towels, which are notable contributors to plastic waste. Their environmental impact is substantial, particularly given their brief lifespan. Due to the settings in which they are utilized, these items are not conducive to separate collection for recycling. Sanitary items and cotton buds, in particular, often end up being flushed away, contributing to marine plastic debris. Effective interventions for addressing these items include: Elimination where feasible—questioning the necessity of disposable coffee stirrers. Substitution with reusable alternatives—pondering the disappearance of the reliable metal teaspoon. Exploring the potential for replacement with biodegradable materials—materials designed to break down in the natural environment. Category II: This category includes larger items with a short lifespan, such as disposable cutlery, cups, “serve ware” (dishware), takeaway packaging, and carrier bags. While these items could be recycled, they often end up as litter or are improperly disposed of in public bins, posing a challenge for reentering the recycling process.

14.3 Packaging and Distribution

Efforts are being made to replace these items with reusable alternatives, such as the growing use of reusable coffee cups. For serve ware, there’s potential for substitution with compostable alternatives. However, for this to be successful, it is essential to ensure sufficient, commercially viable treatment outlets and effective collection systems that keep these items separate from other materials, reducing the risk of cross-contamination between compostable and dry recycling streams. Category III: This category is the main source of plastic waste, comprising items with a lifespan of 1 day to 2 years, such as food and drink containers, agricultural films, and cosmetics. While these items serve crucial functions, banning them could result in negative outcomes, such as increased food waste due to insufficient protection. Interventions in this category focus on enhancing functionality during the use phase and, to a lesser extent, exploring end-of-life options. This involves refining product design, investing in expanding collection and sorting infrastructure, ensuring easy recyclability of products, and promoting the use of recycled plastics in new products. The Plastics Pact outlines commendable goals for the latter two objectives. Category IV: This category encompasses products used over an extended period with a lifespan ranging from 2 to 12 years, items such as car parts, electrical goods, and toys, diverging from those typically discarded as litter and disposed of in distinct ways. Category V: This category represents a variety of construction products and includes building materials with over 12 years of lifespan, such as pipes, insulation boards, roof tiles, and furnishings such as carpets that utilize plastics. Considering the essential purposes of these products, the most suitable strategies revolve around enhancing durability and repairability, as well as promoting increased recycling post use. Achieving this goal necessitates advancements in sorting and separation equipment, especially for electronic waste and vehicle components. In the case of building materials, given their extended usage, improving labeling and tracking systems is crucial for identifying and separating materials, ensuring recovery in the potentially distant future. Hence, it is not a one-size-fits-all approach. However, by examining how products are used and discarded, the complexity of the matter becomes more manageable.

14.3.4

Use and Maintenance

Plastic wastes are rapidly produced at a very high rate because of population growth and industrial development. As mentioned earlier, the government, social communities, and local municipalities have established various protocols, rules, and regulations that can guide the population for proper disposal of plastic waste after utilization. Among these management protocols, some of them are scientifically based such as landfills, bioremediation, and recycling (Kent, 2018; Pérez & Rodríguez, 2018). Typically, plastic wastes are recovered which are diverted from landfills or littering. The volume of plastic materials that go into the waste management system can be minimized by strict actions that decrease the utilization of materials. Designing products for further reuse, repair, and remanufacturing will lead to limited products entering the waste streams. This approach is the basis of the 4Rs strategy in waste management systems to reduce environmental impact by incorporating reduce, reuse, recycle (plastic materials), and recover (energy), where landfill can be considered as the least preferable waste management approach (Ruslinda et al., 2019).

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Plastic waste management

Recycling

Mechanical

Figure 14.6

Biological

Landfilling

Thermochemical conversion

Typical Representation of Recent Trends for Plastic Waste Management

Figure 14.6 demonstrates the schematic diagram of plastic waste management which has been broadly categorized into recycling and landfilling. In this section, the reusability of plastic products and the longevity of finished plastic materials are further discussed to regulate plastic waste in the current scenario. Undoubtedly, it is feasible to convert plastic waste into a base material, thus there is no longer a need for a third party to maintain and manage the waste. Furthermore, the amount of base material required for production also decreases. Interestingly, if waste can be collected and segregated at the source, it is feasible to minimize the energy needed for reuse. This is where waste management of plastic comes in. In other words, during the process of plastic waste management, plastic waste is converted into useful products that are eco-friendly and cost-effective and indirectly reduces the production of base material. There are certain pros to the implementation of plastic waste management which is as follows (de Sousa, 2020; Mazhandu et al., 2021; Pani & Pathak, 2021): a) b) c) d) e) f)

Reduction of consumption of single-use plastic material Minimization of virgin plastic production Minimization of plastic and microplastic pollution Reduction of toxic waste/gas during incineration Balanced ecosystem in an aquatic environment Saving of energy and environment

14.4

Disposal

Plastic disposal is considered to be one of the trickiest things. Irresponsible and improper plastic disposal results in harming wildlife and fouling the environment. This section critically reviews the recycling and cleanup technologies in converting plastic waste into base material for the industry (Browning et al., 2021). The concerned authorities and industries have been struggling for many years to collect, sort, and recycle plastic waste. The mismanagement of plastic waste may pose a serious threat to the environment and human health as well. However, it also poses serious concerns such as clogging drains, air pollution

14.4 Disposal

(when burned), water pollution, and microplastic pollution, and it destroys the beauty of the city. Typically, recycling, landfilling, and incineration are considered the most commonly conventional methods for managing plastic disposal (Lange, 2021; Moharir & Kumar, 2019).

14.4.1 Recycling (Primary Quaternary) of Plastics and Developing More Recycling Systems The intricate terminology surrounding plastics recycling reflects the diverse nature of available recovery and recycling processes. These processes fall under four distinct categories: primary (Mechanical reprocessing into comparable products: The material is capable of primary recycling, where it’s converted into new products with the same properties as the original. This closed-loop process applies to both pre- and postconsumer monostream plastics.); secondary (Mechanical reprocessing into lower-grade products: The recyclate generated from this material exhibits decreased quality compared to the virgin material, leading to its utilization in lower-value applications and an open-loop recycling process. This currently represents the dominant pathway for consumer plastic recycling.); tertiary (Chemical constituent recovery: The polymer itself is not preserved, valuable chemical constituents such as feedstock and monomers are extracted and repurposed.); and quaternary (Energy recovery: The material is subjected to incineration, leading to complete destruction. Nonetheless, the substantial calorific value of plastic allows for the recuperation of energy in the form of heat and electricity) (Schwarz et al., 2021). Primary recycling is commonly referred to as a closed loop, while secondary is often termed downgrading. Furthermore, tertiary recycling encompasses both chemical and biological methods, including depolymerization (Fisher, 2004) and composting (Andrady & Neal, 2009), the latter offering an additional dimension to plastics recycling. Recovered plastic, unfit for its original purpose, is sometimes repurposed in the creation of alternative plastic products, displacing virgin resin classified as primary recycling. Examples include plastic crates from HDPE recovered from milk bottles and PET fiber from reclaimed PET packaging. Secondary recycling, or downgrading, involves using recovered plastic in applications not typically utilizing virgin polymer, such as “plastic lumber” as an economical substitute for timber (Standard, 2000). Chemical or feedstock recycling recovers petrochemical constituents for remanufacturing plastic or producing synthetic chemicals. Despite technical feasibility, economic viability often requires subsidies due to the low cost of petrochemical feedstock compared to converting waste plastic into monomers, reversing energy-intensive polymerization (Patel et al., 2000). While the UK (BP) uses thermal cracking for polyolefin feedstock recycling, a German facility (BASF) ceased operations in 1999 (Standard, 2000). PET chemical recycling, particularly depolymerization, has been successful, with glycolysis, methanolysis, or hydrolysis producing materials such as unsaturated polyester resins (Aguado et al., 2007). The recycling of plastic materials is subject to variation based on polymer type, package design, and product type. Rigid containers composed of a single polymer are more straightforward and cost-effective to recycle compared to multilayer and multicomponent packages. While thermoplastics such as PET, PE, and PP show high potential for mechanical recycling, thermosetting polymers such as unsaturated polyester or epoxy resin cannot

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be mechanically recycled and can only be potentially reused as filler materials after size reduction (Rebeiz & Craft, 1995). Cross-linked rubber from car tires, however, undergoes recycling into rubber crumb for remanufacture, particularly due to the EU Directive on Landfill of Waste. One major challenge in producing recycled resins from plastic wastes is the inherent immiscibility at the molecular level and differences in processing requirements among various plastic types. The addition of recovered plastic to virgin polymer often results in a decrease in some quality attributes, leading to practices such as blending recycled and virgin resin for specific applications. The substitution of recycled plastic for virgin polymer depends on the purity of the recovered plastic feed and the property requirements of the intended plastic product. Current post-consumer recycling schemes focus on easily separated packages, such as PET soft-drink and water bottles, and HDPE milk bottles, due to their positive identification and sorting feasibility, while multilayer/multicomponent articles face limited recycling due to contamination between polymer types. Post-consumer recycling involves key steps: collection, sorting, cleaning, size reduction, separation, and/or compatibilization to mitigate contamination by incompatible polymers.

14.4.2

Recovery/Cleanup

Despite the intense efforts to eradicate the issue of plastic pollution, it is still not economically viable to sort and segregate various plastics found in the environment. The easiest way to segregate the plastic waste is at the original source, i.e., household and public places sorting plastic after prewashing and drying. The recovery process can be further categorized into two steps, namely, (Al-Salem et al., 2009; Khoo, 2019; Zhang et al., 2021): a) Sorting of plastics separately into recyclable and nonrecyclable bins and removal of unwanted materials such as wood and metals. To reduce the volume of plastic waste, this plastic waste can be crushed and grinded. b) In the next step, refined segregation aimed at the removal of alkaline or acidic materials, followed by washing and fine grinding results in complete recovery of recyclable plastic waste. Nowadays, plastic remediation processes are used globally, namely: (a) prevention technologies and (b) cleanup technologies. Plastic prevention technologies play a key role in removing anthropogenic and plastic waste before entering the environment, whereas cleanup technologies are designed to remove the plastic waste that is already present in the environment (Khoaele et al., 2023; Silva, 2021). The present section will review the advanced technologies in various recovery approaches of waste to health. Mechanical recycling, chemical recovery, and energy recovery are some of the commonly used approaches. 14.4.2.1 Developing Advanced Tertiary Technologies

Researchers are exploring unconventional approaches for polymer recycling, employing alternative energy sources such as mechanochemistry, photo-reforming, microwave, and plasma reactors for depolymerization. Bio-inspired pathways involving enzymatic polymer digestion are also explored. Furthermore, research efforts are directed toward alternative solvents such as supercritical fluids, ionic liquids (ILs), and deep eutectic solvents. These approaches aim to address limitations observed in traditional pyrolysis and solvolysis, such as low plastic heat

14.4 Disposal

Microwave heating

Plasma reactor

More even heat distribution in liquids

Chemical upcycling

High monomer recovery due to efficient heating and ionization of polymer chains

Chemical solvolysis

Supercritical fluid

Uses chemical reagents to depolymerize the resin into its monomers

Improved depolymerization due to catalytic effect of supercritical fluid

Figure 14.7 Schematic Diagram Demonstrating Chemical Upcycling: (i) Chemical Solvolysis; (ii) Microwave Heating; (iii) Plasma Reactors; and (iv) Supercritical Fluids

conductivity, heat distribution challenges in industrial reactors, and the limited contact area between solid plastic and the reaction medium or catalyst. The methods outlined in Figure 14.7 hold the potential for improved heating efficiency, conversion rates, and selectivity. Microwave and supercritical fluids (Figure 14.7) offer a quicker, more controlled path to depolymerization. Their uniform heating speeds up reactions and allows for selective targeting of specific bonds. Microwave solvolysis, for instance, boasts significantly reduced reaction times. However, achieving high monomer yields often requires catalysts (Achilias et al., 2010). Supercritical fluids such as water (H2O), unlike conventional methods, can depolymerize even chemically inert polyolefins. By tweaking temperature and pressure, these fluids become catalytically active, even tackling composites such as fiber-reinforced plastic (Akizuki & Oshima, 2018). However, unlike traditional pyrolysis, supercritical water or alcohol yields hydrogenated or oxygenated products (Goto, 2009). Plasma-assisted pyrolysis promises higher monomer yields. ILs address the limited contact issue in traditional methods but suffer from high toxicity, poor biodegradability, and cost. Eutectic solvents, a proposed alternative, are less toxic, biodegradable, and offer high selectivity, as demonstrated in PET glycolysis (Choi & Choi, 2019). Mechanochemistry, mirroring polymer synthesis, utilizes mechanical stress to induce homolytic cleavage in polymers, generating radicals. This process can potentially facilitate cross-linking, cross-polymerization for property restoration, or depolymerization (Caruso et al., 2009). Notably, it does not require additional heating, as the impact zone during ball collisions generates the necessary heat. Mechanochemical pretreatment can enhance waste plastic pyrolysis by facilitating the removal of halogen impurities, such as chlorine from PVC and bromine from PS, which generate corrosive and toxic gases during conventional pyrolysis (Grause et al., 2015). Ball milling has proven effective for the dechlorination of PVC via CaO capture and subsequent removal, adaptable to both wet and basic conditions.

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Additionally, steam-explosion pretreatment significantly reduces liquefaction temperature for PS and HDPE, by 50 and 100 C, respectively (Sugano et al., 2009). The natural occurrence of targeted chemical bonds, such as glycosidic, amide, and ester bonds, guides enzymatic action, highlighting the relevance of “Design for Recycling” principles. However, additional polymers such as polyolefins pose a greater challenge due to their unique chemical makeup. 14.4.2.2 Capture of Microplastics from Sports Fields and Playgrounds

Microplastics (from a broader perspective) are defined as plastic fragments less than 5 mm to 1 μm in size, microplastics are ubiquitous, with prevalent materials such as PE, PP, PVC, PET, PS, and PA (Gan & Zhang, 2019). Categorized by origin, primary microplastics are intentionally manufactured for applications such as cosmetic abrasives, directly entering aquatic environments. Secondary microplastics arise unintentionally from the breakdown of larger plastic debris through UV light, mechanical forces such as waves, and activities such as washing synthetic clothes. In recent times, microplastics have been captured from playgrounds and sports fields. Typically, it is quite a feasible and crucial strategy to minimize environmental pollution. Artificial turf and rubber surfaces are the prominent sources of microplastics. There are a few viable approaches to capture microplastics in these areas which are as follows: (a) installation of filtration drainage systems around the playgrounds and sports fields can accumulate microplastics before entering the water sources. (b) Sweeping and regularly vacuuming the surface of artificial turf and rubber surfaces can capture the loose microplastic particles. Artificial turfs are constructed from synthetic fibers designed to mimic the characteristics of natural grass fields, and their technology has evolved through four generations (Figure 14.8). Artificial turf technology has progressed significantly, transitioning from early nylon surfaces to today’s polyethylene-based systems incorporating various fillings and advanced materials

GEN 1: 1960s

GEN 4: Present

Polypropylene fibers with sand mat

Nylon fibers

GEN 3: 2000s

Polyethylene fibers with different fillings

Figure 14.8

GEN 2: 1970s

Polyethylene fibers with sand and pad

GEN 3.5: 2010s

Polyethylene fibers with sand

The Evolution of Synthetic Turf Starting from the 1960s Till Present

14.5 System-based Approaches

such as sand and pads. This evolution has led to enhanced stability, safety, and weather resistance, enabling wider adoption in sports arenas, playgrounds, and other outdoor spaces. Microplastic loss from artificial turfs occurs through multiple pathways, including footwear adherence, snowmelt dispersal, drainage, and runoff. Footwear-transported microplastics can reach water treatment plants after laundry, while rain, runoff, and snowmelt can facilitate wider dispersal beyond the turf’s boundaries. Ultimately, these microplastics contribute to stormwater and potentially reach marine environments. However, the extent of this transportation is unclear due to limited data on microplastic content in stormwater. To mitigate this concern, filtration methods such as filter bags with 0.4 mm pores are being implemented in stormwater wells to capture granulates larger than 0.4 mm, potentially minimizing the dispersion of most microplastics. However, smaller microplastics may still evade capture and enter the stormwater system. Microplastic loss from diverse sources, including artificial turf fields, contributes to their potential accumulation in stormwater. This load is influenced by turf design and filtration system presence. Despite the implementation of filtration systems, their effectiveness remains unknown due to limited data on microplastics in stormwater. Therefore, extensive research on microplastic fate in stormwater is crucial to assess their dispersion from artificial turfs and design effective mitigation strategies.

14.5 System-based Approaches To date, a lot of efforts have been made to quantify plastic pollution and interpret the negative impact on the environment. In this section, the usefulness of integrated systems approaches for these complex problems, brings policymakers, industries, academia, and society together, and offers a framework of international policies to deal with plastic waste and plastic pollution and meet the goals of the UN Plastic Treaty. Thus, there is a need for education and awareness among consumers (Guron & Slentz, 2021). Additionally, a plastic tax can be implemented. Plastic tax is not a novel concept, it is becoming a hot topic in several countries and regions. Plastic tax can be beneficial for the government to combat plastic waste and pollution and tackle climate change. The objective of the plastic tax is to promote sustainability and a circular economy. Presently more discussions are concerned with a system-based approach to tackling plastic waste which can identify and promote a circular economy. Additionally, this section demonstrates the role of society in curbing plastic waste and how education and awareness can enhance plastic waste management (Blumhardt, 2023).

14.5.1

Extended Producer Responsibility

Extended producer responsibility (EPR) mandates that producers assume responsibility for gathering and recycling specific quantities of the plastic they manufacture and introduce into the market. EPR represents a policy paradigm that shifts the onus of managing products’ postconsumer stage onto their initial creators (https://www.unep.org/reducingplastic-pollution-through-extended-producer-responsibility). This policy mechanism is driven by two key objectives: Municipal burden mitigation: By imposing shared waste management responsibility (financial and/or operational) on producers, EPR alleviates the pressure on municipal

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budgets associated with waste collection, sorting, and recycling. Notably, established systems generate substantial revenue. Design-for-environment promotion: EPR incentivizes manufacturers to prioritize resource efficiency and minimize environmental impact through product design. This incentivizes cradle-to-cradle product life cycles, minimizing waste generation and maximizing resource recovery. EPR adoption has rapidly expanded since its emergence in the 1970s. Its fiscal resilience makes it particularly advantageous in developing regions where limited public funds constrain solid waste management infrastructure. EPR empowers private industry to share investment and operational costs, notably for complex material streams such as plastic packaging. Several consumer-packaged goods companies have pledged to sustainable packaging design, recycling, and waste collection support. However, successfully operationalizing these commitments necessitates developing regional/national collection, sorting, and treatment infrastructure. Inclusive EPR governance models that engage all stakeholders (industry, government, and NGOs) are crucial in facilitating this infrastructure development.

14.5.2

Economy Approaches from Design to End-of-Life

Two economic approaches, linear and circular, offer more effective solutions to address the challenge of plastic recycling in the most efficient manner possible. Linear economy: In a linear economy, resources are extracted to produce synthetic products, which, after their useful life, typically end up in landfills or the natural environment. Notably, in the current linear plastic economy, approximately 95% of all plastic packaging material, equivalent to around $80–$120 billion, is annually lost after a short first-use cycle, with conventional collection systems failing to capture 32% of all plastic packaging (Agenda, 2016). This linear approach significantly contributes to the plastic waste crisis, resulting in environmental and economic consequences, with an annual cost of $13 billion in damages to marine ecosystems alone (Raynaud, 2014). The anticipated doubling of plastic use in the next 20 years, following a 20-fold increase in the past 50 years, underscores the urgency for the polymer industry to evolve. Shifting focus from single-use and disposable plastics to embracing a circular economy model is imperative to address environmental concerns, increase plastic demand, and recapture product value while reducing waste (Hopewell et al., 2009). Circular economy: The alternative to linear economy, the circular economy operates on three fundamental principles (Payne et al., 2019): I) Minimize plastic waste and pollution through thoughtful product design. II) Keep resources and products in use for as long as possible. III) Regenerate and preserve natural systems. Presently, the costs associated with postuse plastic externalities and associated greenhouse gas emissions amount to a conservative estimate of $40 billion, surpassing the entire profit pool of the plastic packaging industry. This underscores a significant opportunity for the industry to transition toward a new plastics economy grounded in the core principles of the circular economy, enhancing socioeconomic performance throughout the supply chain.

14.5 System-based Approaches

This shift not only promises a substantial reduction in plastic waste but also addresses its adverse environmental impact (Facts, 2019). Additional benefits include detaching plastics from fossil fuels in favor of renewable feedstocks, thereby reducing society’s reliance on depleting reserves and recovering material value from waste to prevent dematerialization and minimize cycle losses. Despite these advantages, the prevailing trend involves designing the majority of plastics, particularly in packaging, with an anticipated lifespan of less than a year, contributing significantly to plastic waste and ocean pollution (Rabnawaz et al., 2017). While the plastics industry has historically been reactive rather than proactive, future growth must prioritize addressing current challenges and foreseeing future needs. The emergence of the biopolymer industry signifies a commitment to sustainability, playing a crucial role in tackling current industry challenges.

14.5.3

Adding “Plastic Tax” to Make Any Plastic Product More Expensive

To dissuade individuals from engaging in undesirable behavior, the imposition of high taxes has proven effective, as seen with cigarettes, where a 4% decrease in demand occurs for every 10% increase in price in high-income countries. Similarly, to combat climate change, countries such as Sweden have implemented carbon taxes, linking payment to pollution. Now, another targeted initiative involves a potential tax on single-use plastics (https:// www.wired.com/story/should-governments-slap-a-tax-on-plastic/). Advocates of the California Recycling and Plastic Pollution Reduction Act are advocating for a 1-cent tax on nonrecyclable or noncompostable single-use plastic packaging, such as plastic bottles and potato chip bags. Recology, a waste management company, has spearheaded the initiative, contributing $3.7 million to the campaign alongside environmental groups such as the Nature Conservancy. The proposed tax aims to increase costs for the food and personal care industries that heavily rely on single-use plastics. If enacted, the resulting revenue, estimated to be in the billions annually, would support litter mitigation and offer subsidies to the recycling industry. Half of the revenue would bolster recycling and composting infrastructure, and subsidies would aid various recycling players, addressing the challenge of competing with inexpensive produced virgin plastic. The tax intends to make recycled materials more economically competitive and holds the plastics industry responsible for environmental impacts (Treasury, 2018; Walker et al., 2020). Additionally, this will help to make all single-use plastic packaging and food ware recyclable, refillable, reusable, or compostable by 2030, with a 25% reduction in overall plastic sales by that same year. The concept parallels the carbon tax model, aiming to incentivize behavior change and direct revenue toward environmental initiatives (Saxena et al., 2018).

14.5.4

Education and Better Consumer Decisions

There is an urgent need to tackle plastic pollution at the societal level. As mentioned earlier, novel solutions are implemented to curb our dependency on plastic products. Thus, the usage of eco-friendly alternative products and an increase in the recycling of plastic waste must be executed. Recently, in many countries, education and awareness among common people via NGOs, policymakers, and local authorities can contribute to reducing plastic waste and plastic pollution (Cavaliere et al., 2020; Demichelis et al., 2019; Sandu et al., 2020). Typically, it is believed that education plays a critical role in transforming consumer

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Figure 14.9 Word Cloud Indicating the Importance of Education and Awareness in Society for Reducing Plastic Waste and Plastic Pollution

behavior toward plastic waste management. Proper education to society about the negative impacts of plastic waste and plastic pollution can motivate people to maintain balance in the environment. Additionally, people can motivate themselves to take appropriate actions. This will directly enhance the decision-making toward green solutions. Even, the media can play a crucial role in spreading awareness and education among common people and policymakers on the current environmental issues. This can have a positive impact on people making minor adjustments in day-to-day life. Very interestingly, social media can come into the picture in creating awareness among users. Social media provides a huge platform to create communities for a cause and encourage supporters to act (De Fano et al., 2022; Rapada et al., 2021). This can be well executed by sharing blogs, vlogs, images, and stories to facilitate discussion. Figure 14.9 demonstrates the word cloud representing how education and awareness can help in curbing plastic waste and plastic pollution.

14.6

Conclusion

Mismanagement and misuse of different categories of plastics have resulted in huge accumulations in the surroundings (plastic and microplastic pollution), posing a threat to human health, wildlife, and ecosystems. This book chapter emphasizes current perceptions

References

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Mendieta, C. M., Vallejos, M. E., Felissia, F. E., Chinga-Carrasco, G., & Area, M. C. (2020). Bio-polyethylene from wood wastes. Journal of Polymers and the Environment, 28(1), 1–16. Moharir, R. V., & Kumar, S. (2019). Challenges associated with plastic waste disposal and allied microbial routes for its effective degradation: A comprehensive review. Journal of Cleaner Production, 208, 65–76. Mourshed, M., Masud, M. H., Rashid, F., & Joardder, M. U. H. (2017). Towards the effective plastic waste management in Bangladesh: A review. Environmental Science and Pollution Research, 24, 27021–27046. Nielsen, T. D., Hasselbalch, J., Holmberg, K., & Stripple, J. (2020). Politics and the plastic crisis: A review throughout the plastic life cycle. Wiley Interdisciplinary Reviews: Energy and Environment, 9(1), e360. Nøklebye, E., Adam, H. N., Roy-Basu, A., Bharat, G. K., & Steindal, E. H. (2023). Plastic bans in India–Addressing the socio-economic and environmental complexities. Environmental Science & Policy, 139, 219–227. Pani, S. K., & Pathak, A. A. (2021). Managing plastic packaging waste in emerging economies: The case of EPR in India. Journal of Environmental Management, 288, 112405. Patel, M., von Thienen, N., Jochem, E., & Worrell, E. (2000). Recycling of plastics in Germany. Resources, Conservation and Recycling, 29(1–2), 65–90. Payne, J., McKeown, P., & Jones, M. D. (2019). A circular economy approach to plastic waste. Polymer Degradation and Stability, 165, 170–181. Peng, Y., Wu, P., Schartup, A. T., & Zhang, Y. (2021). Plastic waste release caused by COVID-19 and its fate in the global ocean. Proceedings of the National Academy of Sciences, 118(47), e2111530118. Pérez, M.P. & Rodríguez Á.T.P.2018) Proposal of procedure for maintenance management in plastics processing factories of Cuba. In Proceedings of the International conference on Industrial Engineering and Operations Management. Paris, France. Rabiu, M. K., & Jaeger-Erben, M. (2024). Reducing single-use plastic in everyday social practices: Insights from a living lab experiment. Resources, Conservation and Recycling, 200, 107303. Rabnawaz, M., Wyman, I., Auras, R., & Cheng, S. (2017). A roadmap towards green packaging: The current status and future outlook for polyesters in the packaging industry. Green Chemistry, 19(20), 4737–4753. Rapada, M. Z., Yu, D. E., & Yu, K. D. (2021). Do social media posts influence consumption behavior towards plastic pollution? Sustainability, 13(22), 12334. Ray, S. S., Lee, H. K., Huyen, D. T. T., Chen, S. S., & Kwon, Y. N. (2022). Microplastics waste in environment: A perspective on recycling issues from PPE kits and face masks during the COVID-19 pandemic. Environmental Technology & Innovation, 26, 102290. Ray, S. S., Verma, R. K., Singh, A., Ganesapillai, M., & Kwon, Y. N. (2023a). A holistic review on how artificial intelligence has redefined water treatment and seawater desalination processes. Desalination, 546, 116221. Ray, S. S., Soni, R., Huyen, D. T. T., Ravi, S., Myung, S., Lee, C. Y., & Kwon, Y. N. (2023b). Chemical engineering of electrospun nanofibrous-based three-layered nonwoven polymeric protective mask for enhanced performance. Journal of Applied Polymer Science, 140(10), e53584. Ray, S. S., Peddinti, P. R., Verma, R. K., Puppala, H., Kim, B., Singh, A., & Kwon, Y. N. (2024). Leveraging ChatGPT and Bard: What does it convey for water treatment/desalination and harvesting sectors? Desalination, 570, 117085.

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15 Preventing Secondary Sources of Microplastics in the Environment Zaid Mushtaq Bhat1, Asif Farooq1, Mavra Farooq1, Mariha Feroz1, and Khalid Muzamil Gani1,2 1 2

Department of Civil Engineering, National Institute of Technology, Srinagar, Jammu and Kashmir, India Institute for Water and Wastewater Technology, Durban University of Technology, Durban, South Africa

15.1 Introduction Plastic pollution has emerged as a formidable challenge, casting extensive and profound threats upon our environment, intricate ecosystems, and the welfare of human populations across the globe. Plastics are valued for their versatility, durability, and affordability, making them integral to modern society. Plastic utilization encompasses a wide range of applications, including packaging, construction materials, consumer goods, automotive components, and medical devices. However, the widespread reliance on plastics has led to environmental, social, and economic challenges. These include plastic pollution, resource depletion, waste management issues, and health risks associated with exposure to plastic-related chemicals. The exponential rise in both the manufacturing and usage of plastics has led to a crisis that transcends localized issues, necessitating urgent attention and concerted action to address its multifaceted impacts. While much attention has rightly been directed toward the visible and immediate effects of plastic waste, such as large debris clogging waterways and endangering marine life, it is essential to delve deeper into the less conspicuous yet equally significant realm of secondary microplastics (MPs) (Geyer et al., 2017; Godfrey, 2019; UNEP, 2018). Secondary MPs, resulting from the fragmentation and breakdown of larger plastic items or originating from deliberate manufacturing processes, represent an increasingly recognized facet of the plastic pollution challenge. These minute particles, measuring less than 5 mm in size, pervade terrestrial, aquatic, and marine environments, posing complex ecological and human health risks. Sources of secondary MPs are diverse, encompassing the fragmentation of plastic items such as bottles, bags, and packaging into smaller fragments under environmental stressors such as sunlight (UV radiation) and temperature changes. Mechanical abrasion induces the release of microfibers from synthetic textiles and the wear and tear of tire treads on road surfaces, thereby contributing to the formation of secondary MPs. Despite their diminutive size, secondary MPs exhibit remarkable persistence in the

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environment and have been detected in various ecosystems worldwide, from remote polar regions to densely populated urban centers. The ramifications of secondary MPs extend far beyond their physical presence, as they can serve as vectors for harmful pollutants and disrupt ecological processes at multiple levels. Through adsorption and concentration, MPs have the potential to accumulate toxic chemicals, such as polychlorinated biphenyls and heavy metals, posing risks to organisms upon ingestion or absorption. Furthermore, their ingestion by marine organisms can lead to bioaccumulation within the food web, with implications for human health and ecosystem integrity (Bradney et al., 2019; Kumar et al., 2021; Wright et al., 2013). Moreover, the proliferation of plastic pollution presents immediate threats to human health, given that toxic chemicals within plastics can leach into the environment, pollute water sources, and accumulate within the food chain, potentially yielding long-term health risks for human populations. From airborne MPs pervading our atmosphere to large plastic debris obstructing water bodies and endangering marine organisms, the pervasive presence of plastic pollution accentuates the imperative for swift and concerted action (Kögel et al., 2020; Krause et al., 2020; Prata, 2018; van Raamsdonk et al., 2020). Against this backdrop, this chapter aims to provide a comprehensive exploration of the multifaceted impacts of plastic pollution, with a specific emphasis on secondary MPs. By synthesizing current research findings and insights from scholars in the field, we seek to elucidate the sources, distribution patterns, ecological consequences, and potential mitigation strategies associated with secondary MPs. Through a nuanced understanding of these dynamics, we hope to contribute to the development of evidence-based policies and interventions aimed at addressing this pressing environmental issue.

15.2

Reducing Usage of Plastics

15.2.1

Global Awareness and Incentives to Prevent Disposal of Plastics

Reducing the usage of plastics begins with a fundamental shift in societal awareness. A global understanding of the environmental consequences of unrestrained plastic consumption is pivotal. Encouraging the use of reusable alternatives is a practical approach to reducing single-use plastic items. Governments and regulatory bodies play a crucial role in combating plastic pollution. Enforcing strict regulations on the production, use, and disposal of plastics can create a legal framework that encourages businesses to adopt sustainable practices. Upcycling and recycling of plastic waste are essential to ensure a circular economy for plastic materials. Biodegradable materials, compostable plastics, and alternative packaging solutions can offer viable alternatives without compromising product safety and quality. Educational initiatives, media campaigns, and community involvement play crucial roles in disseminating knowledge about the far-reaching impacts of plastics on ecosystems. Collaborative efforts between governments, nongovernmental organizations, and the private sector are instrumental in instigating a paradigm shift toward responsible plastic use. By arming individuals with the requisite knowledge, the aim is to empower communities to make informed choices that reshape consumption behaviors.

15.3 Recycle and Reuse of Microplastics

Complementing awareness campaigns, the deployment of incentive structures proves to be an effective strategy in dissuading irresponsible plastic disposal and promoting a culture of responsible usage. Operating at the intersection of economic, environmental, and social dimensions, these incentives offer tangible rewards for adopting ecologically conscious behaviors. Various incentive schemes, as outlined below, have been worldwide used to promote the reduction of plastic waste: In Spain, the RECICLOS pilot project introduces a unique concept, utilizing blockchain technology to create virtual reward tokens (Gibovic & Bikfalvi, 2021). This innovative approach encourages active participation in recycling activities by providing households with a digital incentive. Studies, such as the one conducted by Abila and Kantola (2019) in Finland, highlight the significant impact of monetary incentives on waste management objectives. Initiatives such as the GREEN$ program in Hong Kong offer financial rewards for environmentally responsible waste disposal practices. Programs such as Recyclebank in Australia and terracycle.com in the United States leverage the engaging nature of lotteries and virtual currencies to gamify recycling practices. Virtual currencies enhance the appeal of sustainable waste disposal and contribute to a sense of accomplishment. Collaborations between industries and governmental bodies, exemplified by wasteconnectionswichita.com in Germany, showcase the potential of incentivizing sustainable practices. These initiatives not only provide individual rewards but also contribute to broader economic objectives, fostering job creation and innovation within the recycling sector.

15.3 Recycle and Reuse of Microplastics 15.3.1

Incentives to Recycle and Reuse Microplastics

Incentive schemes play an important role in initiating behavioral change toward sustainability, offering financial rewards that motivate individuals and businesses to embrace practices such as reusing and recycling plastics and its byproducts. Various methods across economic, environmental, and social dimensions are explored in the thorough examination of incentives for recycling and reusing MPs which stimulate economic activity in the recycling sector, fostering job creation and innovation for a sustainable economy. Gibovic and Bikfalvi (2021) in their study initiated a pilot project in Spain, introducing a virtual reward token named RECICLOS to incentivize recycling within families. This blockchain innovative approach aimed to encourage and motivate households to actively participate in recycling activities, showcasing a creative integration of technology and incentives to promote sustainable behavior. Abila and Kantola (2019) offer empirical evidence supporting the pivotal role of monetary incentives in achieving waste management objectives in Finland. In Hong Kong, the Environmental Protection Department in 2020 introduced the GREEN$ (Greeny Coins) to foster public involvement with community recycling facilities by providing incentives for environmentally responsible behavior. By motivating individuals to actively engage in recycling activities, the initiative allows participants to accrue GREEN$ through their smart cards. These accumulated credits can then be redeemed for a variety of gift items, enhancing the appeal of sustainable practices among the public. Various initiatives around the world, such as Recyclebank in Australia, terracycle.com and

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wasteconnectionswichita.com in the United States, “e-colones” in Costa Rica, and wasted. com machines in Germany are meant for incentive purposes (Biddle, 2020). Lotteries are a powerful incentive mechanism that is commonly used in many B2C (Business to Consumer) sectors. The incorporation of virtual currencies has increased their ability to serve as effective gamification elements within reward systems. Intrinsic power of lotteries in generating engagement makes them an appealing opportunity to pioneer a separate industry centered on recycling incentives (De la Rosa, 2020). Such initiatives contribute to waste reduction by encouraging proper disposal of plastics and its byproducts, mitigate environmental impact, enhance public engagement, ensure compliance with recycling regulations, and promote resource conservation by reducing the demand for virgin materials through effective plastic recycling initiatives.

15.3.2

Change in Lifestyle

The need of addressing the crisis of MPs necessitates a multifaceted approach, encompassing legislative measures, corporate responsibility, and a fundamental shift in human behavior and lifestyle choices (Li et al., 2020; Xu et al., 2020; Zhang et al., 2020a). Individuals, as primary contributors to MP pollution, hold an important role while addressing MP pollution and, therefore, should be at the forefront of this complex challenge and take right decisions toward environmental sustainability (Hale et al., 2020). Educational initiatives and awareness campaigns play an important role in enlightening consumers about the pervasive presence of MPs and their consequential impacts on the environment and human health (SAPEA, 2019). Community initiatives and awareness campaigns play a crucial role in fostering this change in lifestyle and make awareness among people about what they buy and choose products that do not spread MP pollution (Deng et al., 2020; Misund et al., 2020). Policymakers, as indirect actors, must design and implement stringent regulations that incentivize sustainable practices, aligning with concepts such as the circular economy and restrictions on single-use plastics and integrate approaches that offer a pathway toward a sustainable and resilient future (Da Costa et al., 2020; European Union, 2019).

15.3.3

Production Processes and Recycling

The production of MPs involves distinct processes that contribute to their ubiquity in the environment. Primary MPs are intentionally manufactured for specific applications, such as the production of microbeads used in personal care products, agricultural films, or as raw materials for various industrial processes (Andrady, 2011). These processes often employ mechanical, thermal, or chemical methods to reduce plastics into smaller particles, necessitating careful consideration of their environmental implications and sustainability. Secondary MPs, on the other hand, result from the fragmentation of larger plastic items due to environmental factors such as UV radiation, mechanical abrasion, and microbial activity (Gigault et al., 2018).The presence of both intentional and unintentional origins highlights the complex nature of MP pollution, indicating the necessity for comprehensive strategies that tackle both types of sources. Recycling of MPs encompasses a range of processes designed for sustainable plastic waste management and repurposing (Butkutė & Miknius, 2015). Primary recycling, often referred to as closed-loop recycling, focused on the conversion of clean, uncontaminated, and single-type plastic waste into its original pellet or resin form, enabling reuse in similar

15.3 Recycle and Reuse of Microplastics

applications. However, the feasibility of closed-loop recycling hinges on effective polymer separation and stability against degradation during reprocessing (Hopewell et al., 2009). Secondary recycling, or mechanical recycling, involves downgrading by reprocessing polymeric waste into granules through conventional extrusion, though it comes with the drawback of diminishing product properties due to molecular weight reduction after each cycle (Mandar et al., 2015). While certain plastics, such as PET and polyethylene, can undergo mechanical recycling, others, such as fluoropolymers, are not amenable to this process. Tertiary recycling, or chemical recycling, involves decomposing waste plastics into their building blocks for use as feedstock in plastic production or as fuels for automotive, gasoline, jet fuel, and diesel products. Despite successful depolymerization in processes such as glycolysis for PET, the economic sustainability of chemical recycling remains a challenge primarily due to energy costs (Garcia & Robertson, 2017). Quaternary recycling focuses on energy recovery through incineration, but its ecological acceptability is constrained by the release of toxic substances (Al-Salem et al., 2009; Rochman et al., 2013) (Table 15.1). In addressing these challenges, ongoing efforts concentrate on the development of new recycling technologies, including biological approaches such as microbial or enzymatic degradation. These efforts aim to reduce energy consumption, enhance product value, and minimize toxic waste in a socially responsible manner (Schulte et al., 2013). Biological recycling, particularly through enzymatic technology, emerges as a promising solution for large-scale plastic waste management and detoxification. Biological recycling leverages the activity of Table 15.1

Various Recycling Processes with Their Respective Advantages and Disadvantages

Recycling process Advantages

Disadvantages

Primary recycling (closed-loop recycling)

Maintains product quality

Requires clean and uncontaminated waste

Reduces the need for virgin materials

Limited to specific types of plastics

Secondary recycling (mechanical recycling)

Cost-effective

Diminished product properties with each cycle

Reduces energy consumption

Limited to certain types of plastics

Can process certain types of plastics such as PET and polyethylene

Contamination issues and quality degradation

Tertiary recycling (chemical recycling)

Can handle mixed or contaminated plastics

High initial investment required

Produces high-quality recycled materials

Environmental concerns about chemical usage

Lower energy consumption compared to other processes

Challenges in effective polymer separation and stability against degradation

Energy-intensive process

Can process a wider range of plastics Quaternary recycling (energy recovery)

Provides energy recovery Reduces landfill waste

Ecological concerns due to release of toxic substances Limited applicability to certain types of waste Challenges in managing emissions and pollutants

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microorganisms to degrade MPs into harmless byproducts. Specific bacteria and fungi have exhibited the capability of decomposing different kinds of plastics (Yang et al., 2015) Research by Hasan et al. (2007) and Sahebnazar et al. (2010) demonstrated that Aspergillus and Fusarium can depolymerize polyethylene (PE) following certain pretreatments, such as exposure to ultraviolet (UV) and/or thermal treatments. Leveraging these natural biological processes provides a sustainable and environment-friendly method for recycling MPs.

15.3.4

Development of Techniques for Recovery of Microplastics

There are wide range of techniques for the recovery of MPs from diverse matrices; each technique is adapted to the specific characteristics of the sample. The outlined techniques are: 15.3.4.1 Density Separation

Density separation is a method used in environmental science and waste management to isolate MPs from sediment or other matrices. The technique relies on the principle that materials with different densities will separate when placed in a fluid with a specific density. In this case, a concentrated saline solution, or hypersaline brine, is used as the fluid medium. When the saline solution is added to the sample containing MPs and sediment, the MPs will float or sink depending on their density relative to the density of the saline solution (Thompson et al., 2004). Those MPs with a density lower than that of the saline solution will float to the surface, while heavier materials, such as sediment particles, will sink to the bottom. Related techniques, such as the MPSS (Munich plastic sediment separator), elutriation, and frothflotation methods, are grounded in the principle of density separation (Rani et al., 2023). 15.3.4.2 Pressurized Fluid Extraction

Pressurized fluid extraction is a method used to extract MPs from soils and waste samples. This technique employs solvents at subcritical temperature and pressure conditions, which allows for efficient extraction of MPs while minimizing degradation or alteration of the sample. Semivolatile organic compounds are first removed using methanol, and then MPs are recovered from the remaining matrix using dichloromethane (DCM), a solvent that is effective at dissolving a wide range of plastics. Pressurized fluid extraction offers advantages such as high extraction efficiency and reduced solvent consumption compared to traditional extraction methods (Fuller & Gautam, 2016). 15.3.4.3 Electrostatic Separation

Electrostatic separation is a method used to extract based on their electrical properties. Initially utilized in 2011 for spiked sediment samples, electrostatic separation gained success in 2018 when a Korona-Walzen-Scheider (KWS) electrostatic separator was employed to extract from quartz and beach sands (Felsing et al., 2018). The principle behind electrostatic separation is to apply an electric field to the sample, causing MPs to be attracted or repelled based on their electrical charge. This technique offers the advantage of being nondestructive and environment-friendly, making it suitable for various sample types. 15.3.4.4 Magnetic Separation

Magnetic separation exploits the hydrophobic surface properties of plastics to facilitate the isolation of MPs from soil samples and wastewater. Introduced in 2019, this method

15.3 Recycle and Reuse of Microplastics

involves magnetizing MPs, allowing them to be separated from the sample matrix using magnetic fields. By selectively magnetizing MPs, this technique enables efficient extraction while minimizing interference from other materials in the sample. Magnetic separation offers the advantage of being relatively simple and cost-effective, making it a promising method for large-scale MP extraction projects (Grbic et al., 2019).

15.3.4.5

Ferrofluid-based Separation

Ferrofluid-based separation is an innovative method for isolating MPs from environmental samples. In this technique, magnetic nanoparticles are integrated into a liquid medium to create a ferrofluid. MPs are rendered magnetically responsive by incorporating magnetic nanoparticles, allowing for their efficient extraction under a magnetic field. By applying a magnetic field, MPs are attracted to the magnetized ferrofluid, facilitating their separation from the sample matrix. Modified ferrofluids, particularly those incorporating lubricating oil, have shown efficacy in removing specific types of MPs such as PET (polyethylene terephthalate). Ferrofluid-based separation holds promise for mitigating the impact of MPs in environmental systems, offering a versatile and effective method for their extraction and removal (Hamzah et al., 2021; Hatamie et al., 2016; Zhao et al., 2022).

15.3.5

Recycling Plastic Wastes to Minimize Microplastic Pollution Load

Recycling plastic waste emerges as an important component in minimizing the pollution load of MPs, diverting plastic materials away from landfills, and mitigating the need for new plastic production. Proper recycling processes, encompassing sorting, cleaning, and transforming plastic waste into new products, play an important role in preventing the breakdown of plastics into MPs and subsequent environmental release (Dilkes et al., 2018). In the broader context of waste management, the hierarchy of four Rs—reduce, reuse, recycle, and recover—constitutes an effective strategy (Solis & Silveira, 2020). Efforts to reduce MP generation require a coordinated approach, emphasizing a reduction in plastic production, advocacy for alternative materials (such as glass or cardboard), and the promotion of recycled or biodegradable products. Successful strategies include innovative solutions such as container return systems, bolstered by economic incentives, which have demonstrated efficacy in the reutilization of discarded plastics (Wagner & Lambert, 2018). Recycling offers substantial benefits by conserving resources, minimizing energy consumption, and mitigating polluting emissions, thereby contributing positively to both society and the environment (Prata et al., 2019). In situations where reuse or traditional recycling is impractical, the recovery process takes precedence. This process involves harnessing plastics for energy production or the generation of new raw materials (Quesada et al., 2019). The plastics industry, operating within the circular economy framework, undergoes continual reinvention to align production with waste reduction imperatives (Jia et al., 2019). Strategies at the industrial level include redesigning plastics for circularity, minimizing preproduction plastic pellet losses, extending producer responsibility, banning specific single-use plastics, and supporting the market for recycled plastics (Chen et al., 2021; Civancik et al., 2019).

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15.4

Chemical Upcycling of Polymers

The process of transforming polymers into higher-value materials which may result in the creation of novel substances or materials with poor technological readiness is known as chemical upcycling. This method endeavors to craft new materials from current polymers, enhancing their value and expanding their uses, even though high-tech materials often have a smaller market volume (Stadler & de Vries, 2021). It involves efficiently removing additives from plastics, recovering and refining the raw components, allowing their reuse in making new, higher-quality materials. Compared to traditional mechanical and chemical recycling techniques, polymer upcycling tactics may provide more environment-friendly and energy-efficient paths (Korley et al., 2021). Upcycling methods strive to elevate the worth of discarded polymers by considering a broader concept of “value,” encompassing societal and personal aspects beyond pure economic measurements. This perspective prioritizes the notion of sustainable substitution, steering away from a concise and aligned framework for addressing plastic waste challenges (Jehanno et al., 2022).

15.4.1

Polymer to Polymer Approach

Polymer-to-polymer upcycling converts discarded plastics into a distinct polymer of higher economic value. It primarily employs two methods: 1) Crafting a new polymer from plastic waste using innovative building blocks 2) Enhancing material properties by post-functionalizing the discarded plastic to create innovative materials. For example, polybutylene terephthalate (PBT), a common engineering plastic in household items, was transformed into biodegradable poly(butylene-1,4-cyclohexanedicarboxylate) (PBC) via a hydrogenation process. This polymer-to-polymer upcycling created PBC, useful in tissue engineering or for making shape-memory polyurethanes (Stadler & de Vries, 2021). Another example is utilizing gallium bromide to efficiently reduce polyesters into polyethers. This process unlocks the potential for creating alternative polyether structures, opening avenues for innovative applications (Dannecker et al., 2018). One initial strategy to enhance the value of discarded plastics involves depolymerizing them into distinct building blocks, which are subsequently repolymerized to create a different and more valuable material. The extensively researched depolymerization method involves utilizing the ester groups within PET as an inherent means for transesterification into oligomeric fragments, allowing subsequent repolymerization into diverse polymers such as block copolyesters, polyurethane coatings, or polyisocyanurate foams (Stadler & de Vries, 2021). Another example is the depolymerization followed by polymerization using bio-derived esters and acids has enabled the repurposing of PET into fiberglass-reinforced plastic (Rorrer et al., 2019).

15.4.2

Polymer to Molecule Approach

Upcycling discarded plastics into smaller molecules offers an economically feasible and sustainable alternative to the labor-intensive or costly production of synthetic chemicals. By

15.4 Chemical Upcycling of Polymers

utilizing abundant plastic waste as a resource, selective depolymerization-based transformations represent a pathway for high-volume production of targeted synthetic chemicals. In recent years, the realm of photocatalysis has blossomed into a robust tool, facilitating the direct conversion of plastics into organic molecules of significant value. Through innovative research, scientists have engineered distinct light-driven depolymerization methods tailored to a spectrum of polymers. These techniques span from hydroxylated (bio)polymers to commonplace polystyrene, operating effectively under mild conditions. This breakthrough approach showcases remarkable efficiency, heralding a promising departure from conventional recycling methods by enabling the transformation of polymers into individual, high-value molecules (Eisenreich, 2023). Various methodologies have been reported to dismantle polyolefins into different additives, showcasing the principle of upcycling. Notably, the depolymerization process involved microwave-assisted oxidative degradation of LDPE (Low-Density Polyethylene) sourced from used waste bags and HDPE (HighDensity Polyethylene) obtained from discarded containers. This innovative approach yielded a range of carboxylic acids, including succinic, glutaric, and adipic acids, highlighting the potential for transforming plastic waste into valuable chemical compounds through controlled degradation methods (Bäckström et al., 2017).

15.4.3

Polymer to Material Approach

Processing commodity polymers or their mixtures, which are often inseparable, serves as a promising initial step toward creating next-generation materials for applications in nanomaterials, energy storage, and composites. This delves into two strategies for transforming polymers into materials: thermal treatment for carbon-based materials and compatibilization for achieving polymeric blends. The goal is to produce materials with comparable or improved properties compared to those synthesized from scratch, aiming to reduce petrochemical resource consumption and reintroduce waste into the market. As over 64% of nonfiber commodity plastics consist of hydrocarbons, converting them into carbon-based nanomaterials for energy-related purposes emerges as an attractive avenue for advanced materials with heightened economic value. Notably, the conversion of polyolefin waste into carbon-based nanomaterials predates the formal definition of upcycling (Jehanno et al., 2022).

15.4.4

Upcycling of Mixed Plastics

Real plastic waste is often a mixture of various plastic components such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) (Jisong et al., 2023). The broader adoption and commercialization of effective recycling or upcycling technology for plastic waste have been impeded by the substantial financial investments required for sorting and cleaning procedures. Of particular, complexity is the handling of mixed plastic waste, characterized by its diverse chemical compositions, variable capacities for recycling, and distinct behavioral changes when subjected to different chemical treatments. Managing such composite waste becomes an exceedingly intricate and resource-demanding task due to these inherent complexities, creating significant obstacles in achieving efficient processing methods for effective waste management and utilization strategies (Roy et al., 2021). Embracing upcycling as a method to augment the value of plastics recycling brings forth its

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appeal and resurgence, even amid the expectation of higher energy costs. The chemical transformations involved in upcycling offer a heightened level of versatility in the utilization of recycled plastics, allowing for their integration into novel applications. This approach overcomes the qualitative challenges commonly associated with mechanical recycling methods. Beyond these advantages, upcycling holds the potential to create transformative opportunities for existing plastic waste residing in landfills and the marine ecosystem. By converting such waste into valuable chemical feedstocks, upcycling contributes additional benefits that extend beyond the conventional aspects of a circular economy. In this way, upcycling emerges not only as a method to add value to plastics but also as a multifaceted solution addressing environmental concerns and resource utilization in a more comprehensive manner (Zhao et al., 2021).

15.4.5

Thermal Upcycling of Mixed Plastics

Thermal upcycling of mixed plastics involves subjecting a combination of plastic materials to heat-based processes aimed at transforming them into higher-value products or materials. This approach is particularly important when dealing with materials like PVC, which can release chlorine-based compounds during thermal treatment. To recycle PVCcontaining waste chemically, meticulous processing is essential. Conventional thermal decomposition methods for dechlorination often rely on supplemental adsorbents, such as SiO2 or carbon-supported transition metals such as Fe, Zn, and Mg (Zhang et al., 2020b). Notably, iron (Fe) exhibits remarkable efficiency, removing over 80% of chlorine even at lower temperatures of 300–350 C, fostering the adoption of unconventional adsorbents such as red mud. The dechlorination process typically starts with pretreating PVC waste using NaOH, followed by hydrothermal treatment, resulting in chlorine removal efficiencies exceeding 75%. Furthermore, some methodologies explore the efficacy of supercritical methanol for both plastic decomposition and chlorine removal. However, refining these techniques for precise product outcomes might demand supplementary processing steps or specialized catalysts (Jisong et al., 2023).

15.4.6

Biological Upcycling of Mixed Plastics

The biological upcycling of mixed plastics is a groundbreaking initiative harnessing microbial and enzymatic processes. This approach targets a spectrum of fossil-based and emerging bioplastics, striving to optimize plastic-degrading enzymes and engineer custom enzyme blends. By cultivating self-sustaining microbiomes, it will transform plastic monomers into valuable products and biomass. Through interdisciplinary collaboration and industry engagement, this biological upcycling initiative aims to pave new sustainable pathways within a circular (bio)plastic economy, transcending the limitations of conventional plastic recycling methods (Ballerstedt et al., 2021).

15.4.7

Composite Approach of Mixed Plastics

The sustainable mechanical upcycling of low-value and highly diverse industrial mixed plastic involves employing a composite strategy that integrates carbon fibers, glass fibers, and wood flour. Although the resultant material demonstrates noticeably reduced

15.5 Polymer Construction and Deconstruction

mechanical properties compared to its original state, successful reprocessing of industrial mixed plastic is achieved. Notably, the mechanical strength of these reinforced industrial mixed plastics predominantly hinges upon the reinforcing fibers or fillers incorporated, superseding the inherent fragility of the original industrial mixed plastic matrix. This composite approach signifies a transformation wherein the added elements play a pivotal role in fortifying the previously weaker and more brittle industrial mixed plastic matrix, underscoring the significance of reinforcement in augmenting the properties of the recycled material (Singkronart et al., 2023). The surge in waste plastics poses grave environmental risks, given their extensive degradation timeline of hundreds of years in natural conditions, urging the exploration of innovative upcycling methods alongside traditional recycling approaches. Research by Pol (2010) shows that environment-friendly, solvent-free autogenic processes could be used to convert various waste plastics (LDPE, HDPE, PET, PS, or their blends) into industrially prized carbon microspheres (CMSs). Operating within a closed reactor under autogenic pressure ( 1000 psi), the thermal dissociation of individual or mixed waste plastics yields dry, high-purity CMS powder. Advanced analytical techniques scrutinize the atomic structure, composition, and morphology of resulting CMSs Concurrently, electron paramagnetic resonance (EPR) investigates room-temperature paramagnetism in carbon materials derived from discarded LDPE, HDPE, and PS. These CMSs exhibit conductivity and paramagnetic properties, holding substantial potential for applications spanning toners, printers, paints, batteries, lubricants, and tires—a testament to the transformative power of upcycling plastic waste into industrially valuable CMSs (Vilasganpatpol, 2010).

15.5 Polymer Construction and Deconstruction Polymer construction and deconstruction represent integral components of a holistic approach to plastic management. By focusing on the prevention of MPs through innovative polymer design and the strategic remediation of existing plastics, these strategies align with the principles of sustainability and circular economy. The integration of these practices into the entire lifecycle of plastics, from production to end-of-life treatment, is crucial for a comprehensive and effective response to the challenges posed by secondary MPs. Embracing these technologies fosters a more sustainable and responsible plastic future, contributing to the protection of ecosystems and human health.

15.5.1

Sustainable Polymer Construction for Microplastic Mitigation

In the pursuit of sustainable plastic management, the construction of polymers takes center stage. The development of biodegradable polymers emerges as a key strategy to limit the persistence of plastic in the environment, thereby curbing the formation of long-lasting MPs. Incorporating eco-friendly additives such as prooxidants (metal stearates or carboxylates), natural polymers(cellulose and starch), non–ionic surfactants (Tween), and mineral oil that enhances biodegradation accelerates the breakdown process, minimizing the potential for MP accumulation in various ecosystems (Thew et al., 2023). Exploring renewable

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feedstocks for polymer synthesis contributes to environmental sustainability, producing plastics with reduced ecological impact (Singh et al., 2022; Thew et al., 2023).

15.5.2 Strategies for Microplastic Remediation through Polymer Deconstruction The remediation of MPs involves strategic deconstruction of polymers. Chemical upcycling, a process of breaking down plastics into valuable building blocks or smaller molecules, emerges as a promising strategy to prevent the persistence of intact plastics and reduce the likelihood of MP formation. Selective depolymerization, targeting specific plastics for controlled breakdown, minimizes the diversity of MPs, facilitating their subsequent removal from the environment (Das, 2023). Biological upcycling harnesses microbial and enzymatic processes for plastic breakdown, contributing to the degradation of plastics into biodegradable components, thereby reducing the potential for MP pollution (Cai et al., 2023). Closed-loop systems, established for continuous recycling through depolymerization and repolymerization, ensure that plastics are part of a circular system, preventing MP accumulation (Qin et al., 2022). Thermal upcycling, involving the transformation of plastics into higher-value products through heat-based processes, not only avoids fragmentation into MPs but also repurposes plastic waste into useful materials (Choi et al., 2021). Composite approaches, reinforcing recycled plastics with additional materials, serve to reduce fragmentation, improve strength and durability, and minimize MP generation (Fakirov, 2021).

15.6

Cleaning of Plastic Waste from Environment

Due to the nondegradable nature of plastics, they get accumulate in the environment. Nearly 80% of the waste generated gets accumulated in the landfills (Gourmelon, 2015). Millions of tons of plastic waste enter the ocean annually. It is estimated that 4.8–12.7 million metric tons of plastic waste entered oceans in 2010 alone (Jambeck et al., 2015). This in turn affects the marine life and ecosystem. To reduce the plastic pollution, plastic waste management techniques are required which include some scientific methods such as 3Rs reduce, reuse, recycle, landfilling, incineration, and bioremediation.

15.6.1

Management Strategies

Reducing and reusing are essential components of sustainable plastic waste management. Reduction involves minimizing plastic usage by designing products with less packaging or opting for alternative materials (Asgher et al., 2020). By choosing durable items over disposable ones, less waste is generated. To promote the reduction of waste, encourage the repeated utilization of plastic items instead of discarding them after one use. This may involve donating functional items no longer in use and embracing reusable bags, bottles, and other durable products. Recycling plays a crucial role in plastic waste management by collecting, processing, and transforming waste into new products, thus preventing harmful effects on the environment and society (Evode et al., 2021). The recycling process includes collecting waste plastics,

15.6 Cleaning of Plastic Waste from Environment

sorting, washing to remove impurities, shredding, resizing, identifying, and separating plastics, and compounding (Szostak et al., 2020). Recycling not only diverts plastic waste from landfills but also conserves resources and reduces carbon dioxide emissions associated with virgin plastic production. Landfilling, a common plastic waste disposal method, poses dual risks: groundwater contamination and soil pollution. Waste decomposition releases harmful chemicals, polluting groundwater and degrading soil quality, impacting plant growth and ecosystem health (Nanda & Berruti, 2021; Zheng et al., 2005). Well-managed landfills can mitigate these issues, potentially generating energy through the biodegradation process (Evode et al., 2021). However, despite its cost-effectiveness, landfilling is not a sustainable long-term solution due to its environmental drawbacks, including climate change, greenhouse gas emissions, and wildlife impact (Kedzierski et al., 2020). Incineration, another waste management method, involves burning waste to reduce debris and potentially generate electricity (Yogalakshmi & Singh, 2020; Hopewell et al., 2009). However, it releases toxic gases into the environment and is less commonly used due to pollution concerns. Bioremediation offers a biological approach to waste degradation, utilizing microorganisms such as bacteria, fungi, and plants to break down polymers and detoxify contaminants (Yogalakshmi & Singh, 2020; Jaiswal et al., 2020). Enzymes play a crucial role in this process by reducing activation energy and facilitating the breakdown of substrates into products.

15.6.2

Protection of Aquifers from Micro and Nanoplastic Contamination

About 2 billion people worldwide rely on groundwater from aquifers for their daily water needs (Viaroli et al., 2022). This reliance on groundwater poses risks, particularly when aquifers are overextracted, depleted, or contaminated. Human activities such as unsustainable groundwater pumping for agriculture, industry, and urbanization as well as pollution from various sources are compromising the quality and availability of groundwater (Khatri & Tyagi, 2015) because of which many new emerging contaminants can be introduced (Lapworth et al., 2012). MP is one such emerging contaminant that has been found in groundwater aquifers (Samandra et al., 2022) including nanoplastics (NPs) (Xu et al., 2023). Micro-NPs (MNPs) find their way into the groundwater through soil which potentially contaminates drinking water supplies (Alimi et al., 2021; In-kim et al., 2023) and thus posing a serious threat to human health, crop health, and subsurface ecology (Singh et al., 2022). New research suggests that even though it’s hard to detect NPs (Enfrin et al., 2019), they might be a bigger threat than MPs (Sana et al., 2020) Thus, protecting aquifers from such contamination needs to be addressed. Among these protective measures, constructed wetlands and permeable reactive barriers are natural and engineered barriers that can trap or degrade MNPs before they infiltrate into aquifers. A constructed wetland primarily consists of substrate, plants (such as garden cress, mung bean, great duckweed, and garden onion), and living organisms such as microbes and invertebrates. One potential solution involves pumping out MP-contaminated groundwater and purifying it as surface wastewater treated by proposed wetlands. These plant species assist in reducing MPs and controlling their migration, while macroinvertebrates, utilized as tertiary treatment, impact the distribution and potential removal of MPs (Hassan et al., 2021; Liu & Yang, 2023).

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Another alternative option for the protection of aquifers from MP pollution is remediation of soil. MPs in soil can be transported by natural or human activities such as wind, erosion, and surface runoff to other environmental mediums such as air, water, and subsurface receptors such as aquifers. Invertebrates and microorganisms in the soil contribute to the migration of MPs from the soil surface to deeper layers and groundwater (Shengyan et al., 2020). Therefore, soil remediation aims at protecting aquifers from MNP contamination by certain strategies such as bioremediation (Chia et al., 2023), soil cover, and capping which means applying clean soil to contaminated areas to prevent the spread of MNPs and reducing the risk of leaching into groundwater. Comprehensive monitoring programs should be developed to assess the presence and concentration of emerging organic contaminants including MNPs in aquifers on a regular basis. This monitoring will provide data to understand contamination levels and track trends over time (Lapworth et al., 2012).

15.7

Proper Monitoring of Plastic Waste

The global surge in plastic pollution has ignited broad concerns, underscoring the necessity for a proactive and attentive stance in monitoring and handling plastic wastes. Plastic pollution affects all ecosystem services and has implications on human health, marine life, and other rare species (Beaumont et al., 2019). Effective monitoring is essential to grasp the scale of the problem, pinpoint its sources, and deploy successful strategies for waste reduction and environmental protection. This entails tracing the journey of plastic waste from production to disposal (Life Cycle Assessment), measuring the outcomes of its management such as recycling rates, incineration, landfilling, and environmental leakage (Boucher & Billard, 2019; Jambeck et al., 2015). Monitoring should include the tracking of industrial discharges, urban runoff, and improper waste disposal containing MPs (Horton et al., 2017; Magnusson et al., 2016). Monitoring can be carried out in three ways (Figure 15.1). Tracking the distribution of plastic wastes in different environmental compartments can be facilitated by advanced technologies such as satellite imagery and remote sensing. These tools assist in mapping the spatial distribution of plastic pollution, providing valuable insights into hotspots and vulnerable areas. The strengths of remote sensing lie in its ability to offer spatially coherent coverage across different scales, from local to global, and its effectiveness in accessing challenging or remote areas (Candela et al., 2021; Martínez-Vicente et al., 2019). A range of remote sensing techniques, including Synthetic Aperture Radar, LIDAR systems, polarimeters, thermal infrared sensors, and passive optical remote sensing Figure 15.1 Methods

Monitoring

Satellite

Numerical

In-situ

Different Types of Monitoring

15.7 Proper Monitoring of Plastic Waste

methods such as RGB cameras, multispectral imagers, and hyperspectral imagers are mounted on UAVs, aircraft, and satellites to achieve the desired objective (Garaba et al., 2020; Ge et al., 2016; Kikaki et al., 2020; Matthews et al., 2017; Topouzelis et al., 2020). Monitoring can also be achieved by utilizing computational techniques. Numerical modeling for plastic tracking entails simulating and examining the dynamics, dispersion, and conduct of plastics in diverse environments. Numerical modeling includes techniques such as Lagrangian models, ocean current models, hydrodynamics, and particle dispersion modeling (Alosairi et al., 2020; Hardesty et al., 2017). However, challenges arise when attempting to detect MPs, particularly at depth. In such cases, in situ methods, involving water sampling and subsequent identification techniques including Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and pyrolysis-gas chromatography–mass spectrometry (py-GC-MS), are utilized (Araujo et al., 2018, Elert et al., 2017, Primpke et al., 2020).

15.7.1 Management of Microplastic Waste Inputs to Terrestrial and Aquatic Ecosystems The widespread presence of MPs, tiny plastic particles measuring less than 5 mm, has become a significant environmental concern with far-reaching impacts on both land and water ecosystems. This issue arises from the intricate pathways through which these pollutants enter and spread within these vital ecological systems. Terrestrial ecosystems act as dynamic reservoirs for MPs, with their introduction often beginning at wastewater treatment plants. These plants accumulate a substantial amount of MPs. For example, Magni et al. (2019) showed that an Italian WWTP facility produced an estimated 113 million MPs per ton of sludge on daily basis. Moreover, the use of sludgederived biosolids as fertilizer introduces MPs into agricultural soils, where they can be further dispersed by soil organisms and farming practices. MP degradation is slow, lasting for decades, and activities such as tilling and crop rotation can accelerate their fragmentation. Airborne MPs, originating from sources such as textile washing, plastic waste incinerators, tires, and landfills can also enter terrestrial ecosystems. They are dispersed through windblown littering and improper waste management practices, contributing to their presence in the terrestrial ecosystems (Corradini et al., 2019; Fahrenkamp-Uppenbrink, 2016; Jachman, 2017; Raddadi & Fava, 2019; Wong et al., 2020). Aquatic ecosystems, too, face an onslaught of MPs from diverse sources. Wastewater treatment plants, while effective in removing a substantial percentage of MPs, fall short of absolute efficiency, leading to the discharge of these pollutants into aquatic environments. Furthermore, leaching emerges as a dominant pathway, allowing MPs to infiltrate groundwater systems, as exemplified by detections in karst aquifers in Illinois, United States (Yoksoulian, 2019). Current literature focuses on grounded MPs, but airborne MPs can be deposited in aquatic ecosystems through atmospheric fallout (Bejgarn et al., 2015; Teuten et al., 2009; Dris et al., 2016; Wong et al., 2020). 15.7.1.1

Management Strategies

MP pollution poses a pervasive threat to aquatic and terrestrial ecosystems, demanding a multifaceted strategy rooted in the principles of a circular economy that integrates both

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upstream and downstream solutions. Upstream solutions involve early-stage interventions to prevent pollution, such as using alternative materials such as bioplastics, promotion of upcycling and recycling, enhancing waste management, and imposing restrictions on specific plastic production. Conversely, downstream solutions address the management and mitigation of pollutants already in the environment. For MPs, this includes filtration systems (meshes, trap nets, and other capture devices) to capture plastics, bioremediation techniques, stormwater management, and developing technologies to filter MPs from water bodies (Wong et al., 2020). Figure 15.2 shows different management strategies to tackle plastic pollution. This comprehensive approach addresses the entire lifecycle of plastics, from production to disposal, aiming to minimize the generation, release, and impact of MPs on the environment. 15.7.1.2 Upstream Solutions

Upstream solutions to combat plastic pollution encompass various strategies aimed at mitigating its environmental impact. Biodegradable alternatives derived from renewable sources, such as bioplastics, offer accelerated biodegradability, particularly in terrestrial

Management strategies

Upstream solutions

Downstream solutions

Biodegradable alternatives

Effective filtration systems

Enhanced waste management

Stormwater management

Regulation and legislation

Bioremediation techniques

Promotion of recycling and upcycling

Restoration of riparian zones

Conversion of plastic to fuel

Innovative cleanup technologies Bio-based alternatives in agriculture Erosion control measures Monitoring and early warning systems

Figure 15.2 Different Management Strategies that Can Be Adopted to Reduce MP Input into the Terrestrial and Aquatic Ecosystem

15.7 Proper Monitoring of Plastic Waste

environments (Geyer et al., 2017; Thakur et al., 2018). Despite challenges such as elevated manufacturing costs, recent advancements in crops and microalgae-based bioplastics production show promise, especially within the packaging industry. Adherence to standards such as EN 13432 for compostable packaging ensures that bioplastics meet predetermined criteria, facilitating efficient waste management through composting (Peelman et al., 2013). Enhancing waste management quality is vital to reduce the influx of MPs. Shifting focus from unsustainable practices such as landfilling and incineration to robust recycling infrastructure is crucial. Circular economy principles advocate for developing integrated waste management systems prioritizing recycling, upcycling, and responsible waste disposal to minimize waste generation and prevent MP accumulation (Emadian et al., 2017; Eriksen et al., 2018). Regulation and legislation play a crucial role in addressing plastic pollution by enforcing penalties for improper disposal and restricting single-use plastics. Strategies such as extended producer responsibility (EPR) encourage manufacturers to design products with consideration for their entire lifecycle, promoting proper disposal and recycling (Kosior & Crescenzi, 2020). Promoting recycling and upcycling is fundamental for sustainable waste management. Mechanical recycling of packaging waste and advancements in recycling processes, along with chemical recycling methods such as depolymerization and thermochemical recycling, offer avenues for transforming plastic waste into valuable components (Feil & Pretz, 2020; Pohjakallio et al., 2020). Upcycling creatively transforms discarded plastic items into higher-value products, diverting them from traditional disposal pathways. Conversion of plastic waste into fuel contributes to the evolving landscape of energy recovery. Understanding polymer cracking mechanisms and various techniques such as hydrocracking and catalytic pyrolysis sheds light on utilizing waste plastic oil in diesel engines (Chandran et al., 2020). 15.7.1.3

Downstream Solutions

Downstream solutions focus on effective filtration systems, stormwater management, bioremediation techniques, restoration of riparian zones, innovative cleanup technologies, biobased alternatives in agriculture, erosion control measures, and monitoring systems. These strategies aim to trap, remove, or prevent the spread of MPs in water bodies, soil, and air, thereby mitigating their adverse environmental impacts (Cesarini & Scalici, 2022; Khalid et al., 2023; Liu et al., 2021; Pudasaini et al., 2004; Rehm et al., 2021; Stang et al., 2022; Schmaltz et al., 2020; Talvitie et al., 2017; Wong et al., 2020). Effective filtration systems are designed to remove MPs from water bodies through various filtration mechanisms. They can include both physical filtration methods, such as mesh screens or filters, and chemical filtration methods, such as activated carbon filters, to effectively trap and remove MP particles from water. Proper management of stormwater runoff is essential for preventing the transport of MPs from urban areas into water bodies. Stormwater management strategies may involve the construction of detention ponds, green infrastructure, and sedimentation basins to capture and treat stormwater before it reaches natural waterways. Bioremediation involves using biological agents, such as microorganisms or plants, to degrade or remove pollutants from the environment. In the context of MP pollution,

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bioremediation techniques may harness the natural abilities of certain microorganisms to break down or metabolize MP particles, thereby reducing their presence in the environment. Riparian zones are the areas along the banks of rivers, streams, and other water bodies. Restoring these zones through reforestation, erosion control measures, and habitat restoration projects can help mitigate the impacts of MP pollution by stabilizing soil, reducing erosion, and providing natural filtration of pollutants before they enter waterways. Innovative cleanup technologies encompass a wide range of approaches, including robotic devices, floating barriers, and specialized vessels designed to collect and remove plastic debris from water bodies. These technologies may be deployed in rivers, oceans, and other aquatic environments to target areas with high concentrations of MPs. Introducing bio-based alternatives in agriculture, such as biodegradable mulches and compostable plant pots, can help reduce the input of MPs into soil and water systems. These alternatives break down more readily in the environment, reducing the accumulation of persistent plastic residues. Implementing erosion control measures, such as vegetative buffers, retaining walls, and terracing, helps prevent soil erosion and the subsequent transport of MPs into water bodies. By stabilizing soil and reducing runoff, erosion control measures can minimize the introduction of MPs into aquatic ecosystems. Monitoring systems are essential for tracking the distribution and concentration of MPs in the environment over time. These systems may involve the use of sensors, sampling techniques, and data analysis to assess the effectiveness of mitigation efforts and inform future management strategies.

15.8

Different Multiple Thresholds the Tiered Framework

The presence of MPs in drinking water necessitates a systematic approach for risk assessment and management. A tiered framework for managing MPs involves the establishment of multiple thresholds to assess and address concerns at different levels of severity. California employs a tiered framework, comprising four thresholds (1–4) based on the level of concern: low, moderate, elevated, and high. This aligns with the state’s main thresholds for drinking water management, which include a nonregulatory Screening Level, a quasi-regulatory Notification Level, and a Public Health Goal guiding regulatory actions (California Code of Regulations, 2018; Coffin et al., 2022; Mehinto et al., 2022)

15.8.1

Tiered Framework for Microplastics Concerns

Threshold 1—Low Concern: At this level, MPs exhibit minimal impact or presence in the environment. Strategies primarily focus on prevention and educational initiatives. Monitoring is crucial to detect any potential escalation in MP presence. Threshold 2—Moderate Concern: An increased level of MPs prompts a more active response. Intensified monitoring efforts are coupled with the implementation of initial mitigation measures to prevent further escalation. This stage aims to address emerging issues and mitigate potential impacts. Threshold 3—Elevated Concern: The presence and impacts of MPs become a growing concern. Comprehensive monitoring and research are essential to understand sources,

15.9 Conclusion

pathways, and potential ecological and health impacts. This stage requires strategic interventions to manage and curtail the increasing challenges posed by MPs. Threshold 4—High Concern: This is the highest level of concern, indicating a critical situation demanding immediate and robust action. Intensive monitoring, stringent regulations, and targeted cleanup efforts may be implemented to address the significant presence of MPs. This stage is characterized by urgent measures to mitigate adverse impacts on ecosystems and human health.

15.8.2

Drinking Water Management Thresholds in California

Screening Level (Nonregulatory): This threshold represents the detection of MPs without triggering immediate regulatory action. It serves as a screening tool for initial assessment and acknowledgment of MP presence. Notification Level (Quasi-regulatory): At this level, a concentration of MPs prompts notification to relevant authorities and consumers. While not a strict regulatory limit, it signals increased attention, communication, and consideration of potential impacts. Public Health Goal (Basis for Regulatory Actions): The Public Health Goal represents the threshold at which regulatory actions are informed. It results from a comprehensive assessment of health risks and establishes a target concentration to protect public health. Regulatory agencies may use this level as a foundation for establishing enforceable standards, ensuring the safety of drinking water.

15.9 Conclusion The global challenge of plastic pollution, particularly the proliferation of MPs, underscores the urgent need for meticulous monitoring and comprehensive management strategies. Secondary MPs, often overlooked but ubiquitous, compound this issue with their persistent presence in both terrestrial and aquatic environments, impacting human health, marine life, and biodiversity. Effective monitoring through advanced technologies, such as satellite imagery and remote sensing, and in situ detection methods, such as FTIR and Raman spectroscopy, is crucial for understanding the extent and impact of plastic pollution. The management of plastic waste requires a multifaceted approach, integrating both upstream and downstream solutions. Advancements in recycling technologies, including biological methods such as enzymatic degradation, offer promising solutions for managing plastic waste sustainably. Techniques for the recovery and upcycling of MPs are crucial for minimizing environmental impact. Methods such as density separation, pressurized fluid extraction, and magnetic separation enable the efficient isolation of MPs from diverse matrices, facilitating their removal from the environment. Chemical upcycling of polymers presents innovative approaches to transform discarded plastics into valuable materials, contributing to resource conservation and a circular economy. A tiered framework for assessing and managing MPs in drinking water, as implemented in California, provides a structured approach to addressing different levels of contamination and safeguarding public health.

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15.10

Future Perspective

Moving forward, the fight against plastic pollution will rely on advancements in technology, policy development, and global collaboration. Technological innovations will play a crucial role in enhancing monitoring tools, such as remote sensing and computational modeling techniques, to provide more precise and comprehensive data on plastic waste distribution and hotspots. Additionally, there is a need for improvement in in situ detection methods to enhance the accuracy and sensitivity of MP identification, particularly in challenging environments. In terms of policy and regulation, there is a growing need for stricter regulations at both national and international levels to limit the production and use of single-use plastics and promote sustainable alternatives. Extended Producer Responsibility (EPR) can incentivize manufacturers to take greater responsibility for the lifecycle of their products, including postconsumer waste management. Integration of circular economy practices is essential, emphasizing recycling, upcycling, and responsible waste disposal to minimize plastic waste generation and its environmental impact. Incentives for biodegradable alternatives should be promoted through financial incentives and research funding.

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Wright, S. L., Thompson, R. C., & Galloway, T. S. (2013). The physical impacts of microplastics on marine organisms: A review. Environmental Pollution, 178, 483–492. Xu, B., Liu, F., Cryder, Z., Huang, D., Lu, Z., He, Y., Wang, H., Lu, Z., Brookes, P. C., Tang, C., Gan, J., & Xu, J. (2020). Microplastics in the soil environment: Occurrence, risks, interactions and fate—A review. Critical Reviews in Environmental Science and Technology, 50(21), 2175– 2222. https://doi.org/10.1080/10643389.2019.1694822 Xu, J., Zuo, R., Shang, J., Wu, G., Dong, Y., Zheng, S., Xu, Z., Liu, J., Xu, Y., Wu, Z., & Huang, C. (2023). Nano-and micro-plastic transport in soil and groundwater environments: Sources, behaviors, theories, and models. Science of the Total Environment, 166641. Yang, Y., Yang, J., Wu, W. M., Zhao, J., Song, Y., Gao, L., Yang, R., & Jiang, L. (2015). Biodegradation and mineralization of polystyrene by plastic-eating mealworms: Part 1. Chemical and physical characterization and isotopic tests. Environmental Science and Technology, 49(20), 12080–12086. https://doi.org/10.1021/acs.est.5b02661 Yogalakshmi, K. N., & Singh, S. (2020). Plastic waste: Environmental hazards, its biodegradation, and challenges. In G. Saxena & R. N. Bharagava (Eds.), Bioremediation of industrial waste for environmental safety: Volume I: Industrial waste and its management (pp. 99–133). Springer. Yoksoulian, L. (2019). Microplastic contamination found in common source of groundwater, Researchers Report. Phys Org. Zhang, N., Li, R., Zhang, G., Dong, L., Zhang, D., Wang, G., & Li, T. (2020a). Zn-modified Hβ zeolites used in the adsorptive removal of organic chloride from model Naphtha. ACS Omega, 5(21), 11987–11997. https://doi.org/10.1021/acsomega.9b04417 Zhang, Y., Kang, S., Allen, S., Allen, D., Gao, T., & Sillanpää, M. (2020b). Atmospheric microplastics: A review on current status and perspectives. Earth-Science Reviews, 203, 103118. https://doi.org/10.1016/j.earscirev.2020.103118 Zhao, H., Huang, X., Wang, L., Zhao, X., Yan, F., Yang, Y., Li, G., Gao, P., & Ji, P. (2022). Removal of polystyrene nanoplastics from aqueous solutions using a novel magnetic material: Adsorbability, mechanism, and reusability. Chemical Engineering Journal, 430. https://doi. org/10.1016/j.cej.2021.133122 Zhao, X., Boruah, B., Chin, K. F., Đokić, M., Modak, J. M., & Soo, H. S. (2021). Upcycling to sustainably reuse plastics. Advanced Materials, 2100843. https://doi.org/10.1002/ adma.202100843 Zheng, Y., Yanful, E. K., & Bassi, A. S. (2005). A review of plastic waste biodegradation. Critical Reviews in Biotechnology, 25(4), 243–250.

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16 Reducing and Eliminating Plastic Waste via Societal Changes Pu-Fong Liu1, Chathura Dhanasinghe2, Ying-Liang Yu2, Chih-Ming Kao2, Rao Y. Surampalli3, and Tian C. Zhang4 1

CPC Corporation, Kaohsiung, Taiwan Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan 3 Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 4 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 2

16.1 Introduction Microplastics are typically characterized as solid polymer particles with dimensions ≤5 mm that are insoluble in water. Although microplastics are often found in the environment, the risks they pose are still controversial and largely unknown to the public. In recent years, there has been scrutiny regarding the impact of microplastics on human health. However, the effects of microplastics on human health remain unclear. According to a 2017 report by the International Union for Conservation of Nature, the sources of plastic particles are mainly related to everyday items such as leaks during manufacturing processes, fiber abrasion, tire wear, road marking wear, weathering of ship coatings, microbeads in personal care products, urban dust, etc. (NOAA, 2018). A 2019 report from the World Health Organization indicates that surface runoff and wastewater discharge are the two main pathways for microplastics to enter water sources (WHO, 2019). The article by Koelmans et al. (2019) points out that the most commonly detected shapes of microplastics in various water samples are fragments, fibers, films, foam, and particles. The most common plastic polymers found are Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Polyvinylchloride (PVC), and Polyethylene terephthalate (PET). This is due to their widespread use, density differences, and the processes of fragmentation and wear leading to microplastic formation. Additionally, different shapes of microplastics have different movement and settling patterns in water, affecting detection rates. Overall, the detected shapes and materials of microplastics reflect the results of complex interacting factors (Koelmans et al., 2019). The generation of microplastics is attributed to the excessive use and improper disposal of plastic products by consumers, especially single-use packaging and personal care products. Changing consumer culture and behavior is crucial for reducing microplastic pollution, requiring an increase in environmental awareness and responsibility among consumers,

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and promoting more sustainable production and consumption patterns. However, consumer behavior is influenced by various factors, including social, cultural, psychological, economic, and policy factors. Different consumer groups may have different values and preferences, so tailored policies, education, and communication strategies need to be designed for different markets and cultural backgrounds to facilitate a gradual reduction in the continuous increase of plastic materials in the environment.

16.2

The Importance of Consumer Culture and Behavior

The influence of consumer cultures in different countries on plastic waste is multifaceted, including factors such as consumer habits, recycling and waste management systems, policies and regulations. The formation and release of plastic waste is also affected by various factors, such as the types of plastic products, usage time, usage ways, and waste treatment methods. The following are some key concepts describing how consumer cultures in different countries impact plastic waste: Environmental awareness and consciousness: Different countries have varying degrees of concern about plastic pollution, with some starting to impose restrictions on plastic use and leaning toward choosing alternatives that reduce the use of plastic products, which may lower the demand for plastics. For example, consumers in some European countries and Canada are leading the way in reducing the use of single-use plastics. Regulations: Government regulations can also impact the use of plastic waste. Some countries have already implemented bans or restrictions on certain plastic waste, encouraging manufacturers and consumers to look for more eco-friendly options. Social Norms: Compared to mandatory regulations, norms of social habits may have an even more significant impact on public plastic reduction (e.g., most people may claim that littering is wrong or even illegal, but when they see an already littered environment, they will be more likely to litter). Purposefully leveraging the power of social norms to influence plastic reduction is especially important for less regulated areas. The more people who conform to a pattern of behavior, the stronger the power of social norms (Voronkova et al., 2023). Religious Cultural Norms: In many countries, religious forces have played a major role in recycling and waste reduction, with religions encouraging followers through doctrines and moral teachings to safeguard the world created by God, not taking material enjoyment as the only purpose of life, avoiding overconsumption and extensive use of plastic products. Religions often organize and support local community initiatives on plastic reduction and recycling, exerting their cohesive power to get more people involved in plastic reduction campaigns. Meanwhile, preaching and teaching in religious circles also increases publicity on the severe environmental and health hazards of plastic pollution (Akuoko et al., 2023; Fikri & Colombijn, 2021). Consumer Habits: Consumers’ purchasing habits also impact the use of plastic waste. People in some countries are more likely to buy products with attractive packaging, which may mean using plastic waste as additives to improve the appearance and texture of products.

16.2 The Importance of Consumer Culture and Behavior

Education and Media: Education and media play a critical role in the plastic waste issue. Media and educational institutions in some countries may be more proactive in publicizing the hazards of plastic pollution, thereby raising public awareness of this issue and motivating consumers to opt for more eco-friendly products. Sustainability Initiatives: Many countries and regions see active advocacy for sustainability by nongovernmental organizations (NGOs), citizen scientists, environmental groups, and businesses that encourage consumer participation in activities to reduce the use of plastic waste. These initiatives can have a positive influence on consumer culture. Figure 16.1 presents a word cloud that visualizes the key concepts that influence plastic waste, showing at a glance how consumer culture and behavior, regulations, education and media, religious and cultural norms, etc. interact and affect plastic use and reduction. The word cloud also reflects that solving the problem of plastic pollution requires not only policy and technical support, but also raising public environmental awareness and responsibility, and promoting a transition to more sustainable production and consumption patterns.

16.2.1

What Are the Critical Societal Challenges in Reducing the Plastic Usage?

Recent research (Rabiu & Jaeger-Erben, 2024) delves into the difficulties and challenges of reducing single-use plastic in daily life, focusing on social practices. In this endeavor to minimize plastic consumption, a range of societal issues emerges as formidable obstacles, hindering spontaneous action and lifestyle changes among the public. To begin with, altering consumer habits and lifestyles is recognized as an effective avenue for decreasing plastic usage. However, societal challenges arise as consumers grapple with the inevitability of single-use plastics in their daily lives. Constraints such as the limited

Figure 16.1 Word Cloud of Social and Environmental Awareness on Plastic Pollution: A Global Modeling Analysis

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availability, convenience, and product diversity of zero-waste stores impede widespread adoption. Societal support is needed to increase the number of package-free stores and enhance their product offerings to attract a broader consumer base. The role of education and advocacy cannot be overstated in raising consumer awareness and concern about plastic pollution, thereby instigating a sense of environmental responsibility. Activities such as Plastic-Free Tuesdays (Kemper et al., 2024) and plastic reduction challenges can foster societal support and engagement, influencing individual agency. Nevertheless, challenges extend beyond individual behaviors, as global plastic production and consumption continue to surge. This trend exacerbates the inefficiencies of global waste management systems, intensifying plastic pollution and greenhouse gas emissions. Addressing this requires global collaboration, encompassing aspects from plastic design and reuse to recycling, ensuring a comprehensive circular economy. The profound impact of plastic on the environment and businesses underscores the urgency of reducing plastic usage. It not only harms natural ecosystems but also poses reputational and operational risks to industries such as tourism and seafood. These effects emphasize the imperative of reducing plastic usage through interdisciplinary collaboration. Yet, solving the plastic problem is no easy feat, given the anticipated growth in plastic production and consumption. Current policies and regulations are insufficiently robust and enforced, lacking effective economic incentives and regulatory mechanisms. Overcoming the challenges of plastic demands collaborative efforts from governments, businesses, consumers, research institutions, and NGOs alike (Kibria et al., 2023). On the path to addressing these challenges, a collective effort is required to inspire spontaneous action and practices within society, catalyzing a transformative shift toward reducing plastic usage.

16.2.2

What Are the Potential Solutions?

Plastic, when not properly managed and recycled in the environment, eventually finds its way into the oceans, turning them into receptors of plastic pollution. Existing conventions for ocean management, such as the United Nations Convention on the Law of the Sea (UNCLOS) and the Basel Convention, often fall short of achieving significant reductions in plastic pollution due to the influence of national sovereignty (Guggisberg, 2024). Nevertheless, solutions to plastic pollution can be attained through source reduction, control in the middle stages, and end-of-recycling management, contingent upon the effective implementation of these ideas at the societal level. Reduce the Use of Single-Use Plastics: Single-use plastics, including items such as plastic bags, straws, cups, and utensils, constitute a major portion of plastic waste and are challenging to recycle or decompose. Therefore, reducing the use of single-use plastics is a crucial pathway to addressing plastic pollution. Several countries and regions have implemented policies to ban or restrict single-use plastics, such as the European Union, India, and Haiti. For instance, Bali, Indonesia, enacted regulations in 2018 prohibiting the use of plastic bags, foam, and plastic straws to protect its vital marine conservation areas (Hendrawan et al., 2023). Consumers can contribute by opting for reusable or biodegradable alternatives, such as cloth bags, bamboo or metal straws, and utensils, to minimize single-use plastic consumption.

16.2 The Importance of Consumer Culture and Behavior

Enhance Plastic Recycling and Processing Capacity: Effectively managing plastic waste through recycling and processing is an efficient method to reduce its environmental impact. Plastic recycling reduces the consumption of raw materials, minimizes greenhouse gas emissions, and creates economic value. However, global plastic recycling and processing capacity remains insufficient, particularly in some developing countries. Indonesia, for example, ranks as the world’s second-largest source of marine plastic pollution, with 0.48–1.29 million tons of plastic waste entering the oceans annually. This is attributed to inadequate waste management practices, with approximately 52% of waste in Indonesia going untreated each day (Brown et al., 2023). Therefore, increasing plastic recycling and processing capacity is crucial and necessitates collaborative efforts from governments, businesses, and society to establish effective waste collection, sorting, transportation, and disposal systems, while also raising public awareness and participation. Develop and Utilize Biodegradable or Bio-based Plastics: Biodegradable or bio-based plastics, derived from biomass or capable of microbial degradation in natural environments, offer advantages such as reducing dependence on petroleum resources and lowering environmental harm. However, the development and application of these plastics face challenges, including high costs, performance issues, lack of standardized regulations, and difficulties in recycling (Mong et al., 2024). Strengthening scientific research to improve plastic design and manufacturing, enhancing competitiveness and sustainability, and reinforcing oversight and education are essential to ensuring the proper use and disposal of biodegradable or bio-based plastics, preventing potential negative environmental impacts (Zhao et al., 2022). In conclusion, addressing plastic pollution requires reducing plastic use at the source, improving plastic recycling and processing in the middle stages, and developing and applying biodegradable or bio-based plastics at the end of the life cycle. These strategies necessitate multifaceted cooperation and innovation for effective implementation and impact. As consumers, we can contribute by altering our consumption habits and behaviors to reduce reliance on and emissions of plastic, thereby making a meaningful contribution to protecting our oceans and the environment.

16.2.3

How Might the Solutions Vary Regionally and Globally?

Consumer cultures vary across different countries, influencing the management of plastic waste. Factors such as cultural norms, laws, and habits contribute to the disparities in resource usage, global environmental responsibility, and consumer capabilities among developed, developing, and undeveloped nations. Despite these differences, global attention is increasingly focused on reducing the use of plastic and microplastics to address plastic pollution and sustainability challenges. European Union (EU): In 2019, the EU enacted a series of directives and regulations aimed at reducing plastic pollution, enhancing plastic recycling, promoting a circular economy, and safeguarding the environment and human health. Initiatives such as the SingleUse Plastics Directive, Packaging and Packaging Waste Directive, Industrial Emissions Directive, and rules for food-contact plastic materials were introduced. The EU has adopted the European Climate Law, setting legally binding goals to achieve net-zero greenhouse gas emissions by 2050, accompanied by the Resource Efficiency European Roadmap and

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Circular Economy Action Plan. Measures to regulate cross-border plastic waste transfer and trade have been implemented, including restrictions on exporting plastic waste to nonOECD (Organisation for Economic Co-operation and Development) countries unless it is clean, recyclable plastic waste. While these policies have positively impacted plastic and waste management in the EU, challenges remain, such as enforcement difficulties, balancing costs and benefits, coordinating stakeholders, addressing social and economic impacts, overcoming technological and infrastructure limitations, and addressing legal and standard inconsistencies (Beghetto et al., 2023). United States (US): The US Environmental Protection Agency (EPA) acknowledges the severe environmental and health impacts of plastic production and consumption, particularly in overburdened communities. Post-2023, the US aims to reduce plastic waste through a circular economy model, emphasizing reduced plastic use, design for recyclability, increased recycling rates, and prevention of plastic leakage into the environment. The national strategy aims to eliminate land-based plastic waste entering the environment by 2040, focusing on reducing pollution during plastic production, improving postuse material management, and preventing garbage and microplastics from entering water bodies. Voluntary actions involve collaboration among federal, state, local, and tribal governments, environmental organizations, industries, academia, and the public (EPA, 2023). China: As the world’s largest producer and consumer of plastic, China implemented its strictest plastic ban in 2020, limiting the use of single-use plastic products and promoting alternatives. Waste management practices vary regionally, with coastal areas favoring incineration, while western regions rely on landfilling. China’s plastic recycling rate is low at 9%, with a significant portion being incinerated or landfilled, leading to resource waste and environmental pollution. The lack of standards for biodegradable plastic (BP) products complicates their proper categorization and treatment within the waste management system. China faces challenges in addressing its plastic waste issue, necessitating improved policies, investments, innovation, and collaboration for sustainable solutions (Tan et al., 2023). Indonesia: Ranked as the second-largest global contributor to plastic pollution, Indonesia generates approximately 6.4 million tons of plastic waste annually, with 15% entering the oceans. Challenges in waste management include insufficient infrastructure, funding, technology, and awareness. Indonesia aims to reduce marine plastic waste by 70% by 2025, focusing on enhancing waste collection and processing systems, increasing plastic recycling rates, promoting reduced plastic consumption, and strengthening educational campaigns. Collaboration with international organizations and private sectors is sought to garner additional resources and support. Despite progress, Indonesia faces ongoing difficulties in achieving effective plastic waste management (Chowdhury et al., 2023; Voronkova et al., 2023). Nigeria: With weak waste infrastructure and rapid growth in plastic production and consumption, Nigeria has become a major global contributor to plastic pollution. Microplastic contamination has been observed in several major rivers. However, Nigeria lacks effective policies or regulations to control plastic pollution (Voronkova et al., 2023). South Africa: South Africa generates around 2 million tons of plastic waste annually, constituting 10% of solid waste. Approximately 10% of this is single-use plastics. Limited solid waste disposal capacity results in only about 60% of waste being collected, with the remainder discarded in informal landfills or the environment. South Africa’s plastic recycling rate

16.3 Reduction, Substitution, and Control of Microplastics From Human Usage

is around 43%, higher than the global average. The country’s success is attributed to an informal recycling network that provides employment opportunities for around 60,000 individuals. However, this network faces challenges such as low income, lack of protection, health risks, and social discrimination. Government measures include increasing the thickness of plastic bags and raising levies to reduce their usage, encouraging consumers to opt for reusable or biodegradable alternatives. A national waste management plan aims to enhance waste reduction, recycling, and treatment, fostering a circular economy. The plan also involves supporting and integrating informal recyclers to improve their welfare and efficiency (Voronkova et al., 2023). Recent studies (Neo et al., 2021) indicate that China is the world’s largest producer of plastic waste, accounting for 28% globally, while Indonesia ranks second with 10%. Vietnam is the fourth-largest contributor (6%), and the Philippines is the fifth-largest (5.9%). India currently holds the twelfth position, contributing 0.6% globally but is expected to rise to the fifth position by 2025 due to rapid economic growth. India’s plastic waste generation is projected to increase from 15.9 million tons in 2016 to 26.8 million tons in 2030. However, without proper adjustments to waste management strategies, India’s recycling rate may decrease from 60% in 2016 to an estimated 44% in 2030. Effective solutions require continuous adjustments to plastic waste management strategies, considering the varying economic development stages within a country (Neo et al., 2021). Plastic waste management policies vary widely across different countries, reflecting cultural, economic, and environmental nuances. While efforts are being made globally to reduce plastic pollution, each nation faces unique challenges and must tailor its strategies to its specific circumstances. Ongoing collaboration, innovation, and adaptation of policies are crucial to achieving sustainable solutions and mitigating the escalating global issue of plastic waste.

16.3 Reduction, Substitution, and Control of Microplastics From Human Usage Microplastics refer to tiny plastic particles less than 5 mm in size. They originate from various sources, including plastic products, cosmetics, and clothing. Human usage habits and behaviors regarding plastics impact the level of pollution in the environment. The most effective way to reduce the presence of microplastics is to minimize the use of single-use plastics, including items such as plastic bags, straws, bottles, and packaging materials. The use of reusable alternatives should be encouraged, such as cloth bags, stainless steel or glass bottles, and biodegradable packaging. When selecting clothing and textiles, natural fibers such as cotton, wool, and silk should be chosen over synthetics such as polyester and nylon that shed microplastics when washed. Using a microfiber filter in washing machines can help capture some of the microplastics released during laundry to prevent them from entering the environment. The tiny plastic microbeads used in some personal care products such as exfoliating scrubs and toothpaste are also often overlooked sources of plastic particles released into the environment during personal hygiene routines. Seek out products labeled as “microbead-free” or use natural exfoliants such as apricot shells or sugar instead.

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Additionally, effective filtration systems should be installed at wastewater treatment plants to capture and remove microplastics from effluent before it is released into water bodies. This can significantly reduce the accumulation of microplastics in the environment. The 5R policy, a fundamental strategy for waste management, aims to minimize plastic waste and is the optimal strategy to prevent the generation of microplastics (Thacharodi et al., 2024). The policy includes: Refusing unnecessary plastic products such as disposable plastic bags, straws, bottles, and packaging materials; reducing the use of harmful, wasteful, and nonrecyclable products; reusing items instead of buying new ones to reduce waste, for example, using reusable cloth bags, stainless steel or glass bottles, and biodegradable packaging; recycling not just reusable items, but also focusing more on design thinking for recycling, for instance, choosing clothes with fewer accessories to facilitate the subsequent fabric recycling process; and redesigning through the research and development of innovative materials that can replace the use of plastics in various applications, such as BPs, which offer a more eco-friendly option as they can be decomposed by microorganisms in the natural environment without leaving behind microplastics. Ongoing research and monitoring is also needed to better understand the sources, distribution, and impacts of microplastics. This information can inform effective policies and mitigation measures, as well as guide future research directions and lifestyle changes to curb the persistent issue of plastic microparticle pollution.

16.3.1

Redevelopment of Some Products

In daily life, many products contain microplastics, which enter the environment and have long-term impacts on ecosystems. However, by rethinking the use of these products, it is possible to reduce the impact of these microplastics on the environment. Here are some specific suggestions, including the redevelopment of cosmetics, plastic bottles, cigarette butts, and the plastic coating of slow-release fertilizers: Cosmetics

• • • • •

Bead-free formula: Cosmetics should not contain microplastics, such as beads. Manufacturers can use natural exfoliants (e.g., crushed nutshells, sugar, and salt) in exfoliating products (Singh & Mishra, 2023). Refillable packaging: Cosmetics provide refill options for cosmetics to reduce packaging waste. Customers can buy refills instead of new containers. Eco-friendly packaging: Use sustainable and biodegradable packaging materials. Bamboo, glass, and recycled paper are examples of eco-friendly alternatives. Cleaner ingredients: Make products with clean and nontoxic ingredients that are safe for humans and the environment. Minimize packaging: Design products with minimal or recyclable packaging to reduce waste.

Plastic bottles

• •

Recycle plastic: Increase the proportion of recycled plastic used in the production of new bottles. Biodegradable bottles: Develop biodegradable or compostable plastic bottles as alternatives to traditional plastics.

16.3 Reduction, Substitution, and Control of Microplastics From Human Usage

•

Reuse: Set up refill stations in stores where customers can bring their reusable bottles and refill them with various liquids (such as shampoo, detergent, or drinks), or promote naked shopping or plastic-free stores consumption (Kemper et al., 2024). “Naked shopping” is an environment-friendly shopping method that emphasizes reducing excessive packaging and the use of plastic containers. In “naked shopping” stores, most goods do not provide packaging, and consumers need to bring their own containers to buy goods. This method allows consumers to buy the quantity they need according to their own needs, thereby reducing waste. This shopping method can not only reduce the generation of plastic waste, but also reuse existing containers, achieving the effect of reducing plastic and recycling.

Cigarette butts

• • • •

Biodegradable filters: Cigarette butts are a major source of plastic (cellulose acetate) pollution. Develop biodegradable or compostable cigarette filters to reduce the environmental impact of discarded cigarette butts. Smoking cessation programs: Promote smoking cessation programs to reduce the number of cigarettes consumed and thus the number of cigarette butts produced. Educational activities: Implement activities to raise people’s awareness of the harm that cigarette butt waste causes to the environment. Tobacco substitutes: Encourage the development and use of nontobacco substitutes that do not produce cigarette butts. Also, through producer responsibility, cigarette manufacturers, and sellers can be held responsible for the recycling and disposal of cigarette filters, or pay-related fees. This can increase the cost of cigarette manufacturers and encourage them to reduce or cancel the use of filters (Green et al., 2023).

Plastic coating of slow-release fertilizers

• •

Biodegradable coating: Develop biodegradable or environment-friendly coatings for slowrelease fertilizers to minimize soil pollution caused by plastics (Zhou et al., 2024). Studies show that the composition and additives of the plastic coating of slow-release fertilizers may have toxic or inhibitory effects on soil microorganisms and plants (Fertahi et al., 2021). These problems can be solved by using biopolymers to replace plastic coatings because biopolymers have the advantages of being biodegradable, renewable, low-cost, nontoxic, and enhancing soil quality. Commercial organic fertilizers are important fertilizers for the development of organic agriculture in China, but they are also a potential important source of microplastics in farmland. These microplastics may come from livestock farming, industrial processes, packaging materials, etc. To reduce the impact of microplastics on agriculture and the environment, it is necessary to strictly regulate the production and use of commercial organic fertilizers, raise consumers’ environmental awareness, control the production and consumption of plastics, and strengthen the recycling and disposal of microplastics (Zhao et al., 2023).

In summary, although current technology can achieve the reduction of plastic use in materials and materials as alternatives, this does not mean that consumption can be transitioned. The key to actually solving the plastic problem is still to reduce consumption, avoid

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the use of plastic products, and when unavoidable, choose environment-friendly products that are more friendly to the environment. This series of raising consumer awareness to promote behavioral changes (Kemper et al., 2024) is what can help minimize the negative impact of these products on the earth.

16.3.2

Substitution Using Eco-friendly Materials

The adoption of eco-friendly materials as alternatives to traditional ones, such as BPs, is a key strategy in mitigating environmental impact. This approach can be implemented across a wide range of products and applications. Table 16.1 provides a comprehensive comparison Table 16.1 Sustainable Substitutes for Conventional Products Product category

Current material

Alternative product and material

Single-use plastics

Plastic bags, plastic utensils, plastic straws

Biodegradable or compostable bags (e.g., made from cornstarch, potato starch, or sugarcane), PLA (polylactic acid) utensils, biodegradable, or paper straws

Food packaging

Biodegradable containers and packaging (e.g., made from bagasse or compostable plastics), edible packaging materials (e.g., edible films made from ingredients such as seaweed)

Biodegradable containers and packaging (e.g., made from bagasse or compostable plastics), edible packaging materials (e.g., edible films made from ingredients such as seaweed)

Cosmetics and personal care

Microplastics

Biodegradable alternatives (e.g., jojoba beads, apricot shells, or bamboo)

Agriculture

Plastic mulch films

Biodegradable mulch films (e.g., made from PLA or starch-based polymers)

Clothing

Traditional textiles

Biodegradable textiles (e.g., hemp, organic cotton, or lyocell)

Fishing industry

Fishing nets and gear

Biodegradable fishing nets and gear

Electronics

Electronic product casings

Biodegradable materials

Medical field

Single-use medical devices

Biodegradable plastics

Construction

Plastic foam insulation materials

Biodegradable or eco-friendly insulation materials

Packaging materials

Polystyrene packaging peanuts

Biodegradable alternatives (e.g., made from cornstarch or other biodegradable materials)

3D printing

3D printing filaments

Biodegradable filaments (e.g., PLA)

Consumer products

Children’s toys

Toys made from biodegradable materials

Scientific research

Plastic labware

Biodegradable options

Promotional materials

Promotional products, such as pens and keychains

Biodegradable materials

16.3 Reduction, Substitution, and Control of Microplastics From Human Usage

of the materials currently used in various product categories and their potential eco-friendly substitutes. These alternatives are often biodegradable or sourced sustainably, thereby reducing environmental impact. It underscores the importance of considering the intended use of the product, its life cycle, and waste disposal when substituting traditional materials with biodegradable ones. These alternatives should comply with relevant standards and certifications, and the environmental benefits of these alternative products should be validated through a life cycle assessment (LCA). Biodegradable Materials as a Solution for Environmental Problems: The use of biodegradable materials as substitutes for traditional ones is a viable way to address the environmental problems caused by the accumulation of nonbiodegradable waste, such as plastic pollution. By using materials that can decompose naturally or be composted, we can reduce the amount of waste that ends up in landfills, oceans, and other ecosystems. Moreover, by sourcing these materials from renewable resources, such as plants or agricultural waste, we can also reduce the dependence on fossil fuels and lower the greenhouse gas emissions associated with the production of conventional materials. Therefore, biodegradable materials offer a more sustainable and environment-friendly option for various products and applications. Factors to Consider When Choosing Biodegradable Materials: However, not all biodegradable materials are equally suitable for every product or application. There are several factors that need to be considered when choosing the best biodegradable material for a specific purpose. One of these factors is the intended use of the product, which determines the required properties and performance of the material. For example, some biodegradable materials may not be able to withstand high temperatures, moisture, or mechanical stress, which may limit their applicability in certain situations. Another factor is the life cycle of the product, which refers to the stages of production, distribution, consumption, and disposal of the product. The life cycle of the product affects the environmental impact of the material, as different stages may involve different amounts of energy, water, and emissions. A third factor is the end-of-life disposal of the product, which involves the methods and conditions of waste management. The end-of-life disposal of the product influences the biodegradability of the material, as different environments may have different levels of oxygen, moisture, microorganisms, and other factors that affect the decomposition process. Therefore, when selecting biodegradable materials, it is essential to consider how the product will be used, how long it will last, and how it will be disposed of. Standards and Certifications for Biodegradable Materials: In addition to these factors, it is also important to ensure that the biodegradable materials meet the appropriate standards and certifications that verify their environmental claims. There are various standards and certifications that define the criteria and methods for testing the biodegradability, compostability, and recyclability of materials. These standards and certifications provide a reliable and consistent way to measure and compare the environmental performance of different materials. They also help consumers and businesses to identify and choose the most eco-friendly products and materials. Some examples of standards and certifications for biodegradable materials are ASTM D6400, EN 13432, ISO 17088, and BPI. These standards and certifications specify the requirements and procedures for determining the biodegradability and compostability of plastics and other materials in industrial or home composting conditions.

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Life Cycle Assessment of Biodegradable Materials: Finally, to evaluate the environmental benefits of biodegradable materials, it is necessary to conduct an LCA of the products and materials. An LCA is a systematic and comprehensive analysis of the environmental impacts of a product or material throughout its life cycle, from cradle to grave. An LCA considers the inputs and outputs of materials, energy, water, and emissions at each stage of the life cycle and assesses the potential environmental effects of these inputs and outputs on various categories, such as climate change, human health, and biodiversity. An LCA provides a holistic and objective way to compare the environmental impacts of different products and materials, and to identify the areas where improvements can be made. By conducting an LCA of biodegradable materials, we can quantify and validate the environmental benefits of these materials and ensure that they are truly eco-friendly. When substituting traditional materials with biodegradable alternatives, it’s essential to consider factors such as the product’s intended use, its life cycle, and its end-of-life disposal. Additionally, ensuring that biodegradable materials meet appropriate standards and certifications is crucial to verify their environmental benefits. Sustainable sourcing, manufacturing, and disposal practices play a significant role in maximizing the environmental benefits of eco-friendly materials. However, it’s important to note that some materials, even though they are biodegradable or natural, can pose challenges in the material cycle. For instance, adding Polylactic Acid (PLA)—typically made from cornstarch—to plastic materials to reduce plastic use can cause issues in the plastic recycling cycle. Therefore, when considering how to use appropriate materials to minimize the impact of microplastics, it’s crucial to examine the entire life cycle of the material. This includes sourcing, manufacturing, usage, and disposal, as well as the potential impact on recycling processes. By doing so, we can ensure that our efforts are more environment friendly and do not inadvertently create new problems. A recent article by Zhu and Wang (2020) discusses whether BPs are a green hope or a greenwashing trap. The article points out that BPs can theoretically shorten the life cycle of plastics and reduce environmental stress, but their biodegradability and ecological impact in natural environments still need further verification. The article raises the following three questions (Zhu & Wang, 2020): (a) Biodegradability in the environment: The current standards and testing methods are insufficient to predict the biodegradability of BPs in natural environments and do not consider the toxicity and ecological effects that BPs or microplastics may generate. (b) Impact on existing waste management: BPs may interfere with existing recycling and treatment systems, causing confusion and contamination, and may also reduce the quality and value of recycled plastics. (c) Impact on resources and global carbon sinks: The production and consumption of BPs may increase the demand for biological resources, leading to land use changes and biodiversity loss, and may also affect the balance and stability of global carbon sinks. The article finally suggests that successfully addressing these knowledge gaps is a key requirement for developing new standards for producing BPs.

16.3.3

Education and Awareness

When addressing the issue of plastic pollution in different countries and regions, the first step is to educate the public about their understanding of plastic pollution. In this regard, a

16.3 Reduction, Substitution, and Control of Microplastics From Human Usage

questionnaire survey could be the first step to gauge public awareness. This can be done by setting objectives, designing the questionnaire, distributing the survey, and analyzing the results. The goal is to understand the current knowledge and attitudes of the target audience toward plastic pollution and identify any gaps or misconceptions, thereby improving the public’s correct understanding of plastic pollution. Next is the education and awareness-raising campaign. Based on the survey results, these activities aim to enhance public understanding and education about environmental issues. This includes identifying key messages, creating educational materials, organizing workshops and seminars, participating in community events, integrating environmental education into school and university curricula, utilizing online and social media, collaborating with local media, interacting with local businesses, establishing feedback loops, and measuring impact. Education and awareness-raising is a continuous process that needs to be tailored to the specific needs and knowledge gaps of the target audience. Through a continuous education process, it is possible to change the behavior of the public in their use of plastic materials in daily life, thereby influencing the manufacturing of plastic by producers and reducing the persistent behavior of plastic pollution. On the other hand, by combining a thorough survey with effective education and outreach, individuals and communities can make more informed and sustainable choices, which can implement the concept of reducing plastic continuously in the community and individual influence. Figure 16.2 illustrates the evolution of green consumer awareness. When people realize the importance of environmental protection and their own powerlessness, they will reduce consumption and waste to ease their guilt and passively participate in various environmental activities or recycling work. Over time, they will actively and positively want to do more for environmental protection, pay attention to green products and consumption

Understanding the global environmental issues and one’s own helplessness

Consumption is one of the culprits, causing guilt

Green products and consumption information

What else (Cognition/Feeling) (Action) Passive behavior • Resource recycling • Participating in environmental activities Figure 16.2

Changing lifestyle • Willing to pay effort • Spontaneous “Voluntary simplicity” • Reinforcement of cognition (Small and beautiful, small and expensive, small and eco-friendly

The Evolution of Green Consumer Awareness

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information, be willing to change their lifestyle, and reduce the burden on the environment. Eventually, they will further change their mindset, willing to make more effort, spontaneously simplify their lives (voluntary simplicity), and strengthen the concept of small and beautiful, small and expensive, and small and environment friendly. This kind of thinking helps to reduce unnecessary waste and also to improve the quality of life and happiness. This kind of awareness evolution needs to be promoted and disseminated through education or mass power, so that more people can join this green consumption line, and these methods also help to further reduce the global plastic problem. Given that plastic particulate pollution is a global challenge, it requires not only education and awareness-raising for individuals and communities, but also international cooperation to reduce its persistent harm. The collaboration of NGOs and research institutions, and the promotion of cross-national cooperative projects are beneficial for enhancing global awareness of plastic particulate pollution. Through social media and internet platforms for promotion, attracting global attention, and collaborating with international enterprises and brands to promote sustainable products and practices, it is possible to further enhance awareness and educate the public, fostering a more sustainable and environment-friendly society. In addition to the aforementioned education and awareness-raising activities, there is another way to raise public awareness and participation in plastic pollution, which is the approach of citizen scientists. Citizen scientists are people without a professional scientific background, but who contribute their knowledge, skills, and time to promote the development of science and social progress by participating in scientific research or activities. Citizen scientists can participate in scientific research or activities by collecting and analyzing data, observing and recording phenomena, testing and improving methods, or sharing and disseminating results (Kawabe et al., 2022). In the field of plastic pollution, citizen scientists can help fill the data gap in the distribution of coastal and marine plastic pollution and can effectively raise public awareness of plastic pollution (Catarino et al., 2023). Schofield et al. (2023) pointed out in their research that countries in South America have used the approach of citizen scientists to narrate environmental actions in the form of stories, filming or writing them to social media, effectively promoting other citizens’ participation, which may lead to behavior change. This change can also extend to other sectors of society. The interaction and influence of citizen scientists with researchers, media, communities, and decision-makers, assisting in the collection and analysis of marine plastic pollution data, and sharing data and information with media and communities to raise public awareness, make decision-makers under the pressure of the masses, must take actions based on scientific evidence, reduce the source and impact of plastic pollution, and promote decision-makers to take actions (as shown in Figure 16.3). The approach of citizen scientists is an effective method of educating and promoting plastic pollution, which can make the public more proactive and active in participating in scientific research and environmental actions, thereby enhancing their environmental awareness and sense of responsibility, and promoting social transformation and innovation (Schofield et al., 2023). Dowarah et al. (2022) conducted a case study by using a questionnaire survey to investigate the impact of education and cognition on plastic issues. The research background is the preliminary survey of Indian students’ cognition, attitude/behavior, and opinion

16.3 Reduction, Substitution, and Control of Microplastics From Human Usage Raising environmental awareness & willingness to engage on

Environmental problem

Marine litter Collecting data

Motivate

Formulating hypothesis

Assistance Data

Actors Citizen scientists Social media

Communication tools

Professional scientists Traditional media

Scientific information

Raising awareness Sharing

Informing

Pressure to act

General public

Decision makers

Figure 16.3 Citizen Scientists Raise Public Awareness and Influence Policy Makers on the Issue of Marine Pollution, with the Aim of Protecting the Oceans (Source: Schofield et al., (2023) / with permission of ELSEVIER.)

on plastic and microplastic pollution. India is a country with serious plastic pollution. The survey shows that women have higher plastic pollution cognition than men, and education level and learning field also affect the cognition level, among which science students have the highest cognition. Dowarah et al. (2022) point out that India needs to strengthen environmental education, especially on microplastics and raise public awareness through media and community activities. In addition, more stringent policies and regulations must be formulated and implemented to control plastic waste from entering the marine environment and promote biodegradable alternatives (Dowarah et al., 2022). Another research case that uses a questionnaire survey is Miguel et al. (2024). The research background is the empirical study of the Portuguese public’s knowledge, concern, and attitude toward plastic pollution. It is found that the Portuguese public has a certain knowledge of plastic pollution, and they think plastic pollution is a serious problem. They feel worried personally, but they think that people around them do not have enough concern. Education level and age are important factors affecting public knowledge, concern, and behavior on plastic pollution. The higher the education level and the younger the age, the more likely they have positive views and behaviors (Miguel et al., 2024). Both studies point out that the key to formulating effective education and publicity activities is to increase the public’s environmental knowledge and encourage environmental protection behavior. It is suggested that environmental education should be integrated into

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school plans, especially in the first nine years of education (approximately students aged 6–14) (Soares et al., 2021). These studies also provide useful information that can help government and social organizations formulate more suitable policies and measures to reduce the impact of plastic pollution on humans and the natural environment.

16.3.4

Change in Lifestyle

To effectively reduce the issue of plastic pollution, changes in lifestyle habits can significantly decrease the use of plastic. For consumers, it is crucial to avoid using disposable plastic products as much as possible, as this can substantially reduce the manufacturing and consumption of plastic products. Disposable plastic products are often used only once and then thrown away, creating a large amount of waste that is difficult to degrade and recycle. Table 16.2 provides some methods to reduce the use of disposable items, such as using personal water bottles, utensils, and shopping bags, and refusing to use plastic straws and containers. These methods can help consumers save money and resources, as well as protect their health from the potential hazards of plastic chemicals. When choosing products, it’s recommended to opt for biodegradable materials or recyclable products and packaging, such as paper, glass, metal, or bamboo, to reduce the use of plastic. Biodegradable materials can decompose naturally and return to the environment, while recyclable products and packaging can be reused or transformed into new products, reducing the need for new materials. Additionally, it’s important to increase waste recycling rates. Individuals can participate in community recycling programs and learn how to correctly sort and handle various types of waste, promoting resource circulation. Recycling can also create economic benefits, such as generating income, creating jobs, and saving energy. When the use of plastic products is reduced, the demand for these products will decrease. This could lead to a reduction in production, thereby reducing the generation of plastic waste. Using less plastic can prevent it from eventually ending up in our oceans and landfills, causing harm to wildlife and the environment. Plastic pollution can have serious consequences, such as endangering marine life, disrupting ecosystems, contaminating food chains, and affecting human health. Therefore, reducing plastic use can help preserve the natural environment and biodiversity as well as ensure the well-being of current and future generations. Table 16.2 Alternatives to Reduce Plastic Use in Daily Life Plastic items

Alternatives to reduce plastic use

Plastic straws

Drink directly, metal straws, reed straws

Plastic bags

Reuse plastic bags, eco-friendly bags

Plastic cups

Use in-house cups, eco-friendly cups, insulated cups, water bottles

Takeaway utensils

Eat in-house, eco-friendly utensils, food wraps, silicone food containers

Plastic bottles

Water bottles, water-filling apps: tea movement

Plastic packaging

Package-free stores, supermarket fresh produce naked selling area

Plastic fibers

Natural fibers: organic cotton, linen; second-hand clothes

Microplastics

Natural particles: sea salt, minerals, almonds

Sanitary pads

Menstrual pants, menstrual disks, cloth sanitary pads

16.3 Reduction, Substitution, and Control of Microplastics From Human Usage

Changing our habits can also influence others in our community to do the same, creating a larger collective impact. When individual consumption habits drive collective consumption habits, the impact that can be caused will be even greater. This can increase the motivation of manufacturers to develop sustainable alternatives, thereby effectively solving the plastic problem. By choosing eco-friendly products and services, consumers can express their preferences and values and encourage producers to adopt more environmentally responsible practices. This can create a positive feedback loop, where both consumers and producers contribute to the solution of plastic pollution. When consumers realize that environmental degradation is caused by excessive and improper consumption by humans, they expect to influence the supply and manufacturers of products by changing their personal or group consumption patterns and demand content and urge manufacturers to produce or provide products with environmental concepts, to meet consumers’ environmental needs and achieve the goal of green consumption in life. However, it is not easy to distinguish between general products and green products, so more than 25 industries and 199 countries around the world have established more than 460 different types of eco-labels (Eco-label or Green Mark or EcoLogo) (Hou et al., 2023; Lou et al., 2023; Xin & Long, 2023). These eco-labels are logos awarded by third-party organizations based on the environmental impact of the product’s life cycle and the environmental standards and regulations that the product meets, which can help consumers and business buyers quickly identify environment-friendly products. Figure 16.4 shows the patterns of common eco-labels from different countries, such as the European Flower from the

European Union

Germany

Nordic

Singapore

Taiwan

Netherlands

Canada

France

Japan

USA

Korea

China

Australia

Hong Kong

India

Figure 16.4

Common Eco-labels from Different Countries

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European Union, the Energy Star from the United States, the Green Mark from Taiwan, etc. When the general public cannot distinguish whether the consumer products they choose will professionally cause harm to the environment, they can choose more environmentfriendly products in their lives through these eco-labels, to reduce the impact of consumption on the environment. This way of life can also reduce the environmental pollution caused by plastic, because plastic is a material that is difficult to degrade and recycle, and millions of tons of plastic waste enter the ocean every year, endangering ecosystems and wildlife. Therefore, choosing products with eco-labels can not only protect the environment but also show social responsibility and civic awareness.

16.4

Future Directions

Plastic waste presents a critical environmental challenge with far-reaching negative impacts on ecosystems and human health. Addressing this issue effectively requires comprehensive changes at the societal level, involving shifts in consumer culture, behavior modifications, product redevelopment, and the promotion of alternatives. This section explores how these societal changes can contribute to minimizing and eradicating the plastic waste problem, proposing key future initiatives: Promoting Circular Economy: A circular economy, emphasizing resource efficiency and waste reduction, offers a strategic approach. By reducing dependence on raw materials, extending product lifespan, promoting reuse and remanufacturing, and transforming waste into resources, a circular economy can curtail the demand for virgin plastics, decrease plastic waste generation, and foster green jobs and competitiveness. Strengthening Environmental Education and Promotion: Crucial to this effort is the enhancement of environmental education and promotion. These initiatives can convey the impact of plastics on the environment, educate on the benefits and methods of plastic reduction, and encourage public participation through platforms such as schools, media, and communities. Strengthened environmental education can reshape public consumption attitudes and behaviors, elevate environmental awareness and responsibility, and foster social support for plastic reduction policies. Formulating and Implementing Effective Policies and Regulations: Policies and regulations are essential tools for plastic reduction, guiding production, use, and disposal through legal, economic, and administrative means. This includes measures such as restricting disposable plastics, implementing taxes on plastics, setting recycling targets, and promoting eco-labels. Effective policies can alter market dynamics, increase the environmental cost of plastics, encourage alternatives and innovations, and safeguard the public interest in environmental conservation. Additional Key Initiatives Include: Reduce Single-Use Plastic Products: The reduction of single-use plastic products requires the establishment of governmental regulations and policies. Encouraging manufacturers and consumers to choose reusable or biodegradable alternatives, such as cloth bags and metal utensils, is crucial.

References

Enhance Plastic Recycling and Processing Capabilities: Efficient waste collection, sorting, transportation, and disposal systems, coupled with increased public participation, are essential for effective plastic waste management. Develop and Utilize Biodegradable or Bio-Based Plastics: Strengthening scientific research, improving plastic design and manufacturing, and reinforcing regulation and education are vital for the development and correct usage of biodegradable or bio-based plastics. Education and Awareness: Creating educational materials, organizing workshops, incorporating environmental education into curricula, and utilizing various media channels are crucial in raising public awareness and concern about plastic pollution. Lifestyle Changes: Altering lifestyle habits, such as avoiding single-use plastic products, choosing biodegradable items, and participating in community recycling programs, can significantly reduce plastic usage. In conclusion, a holistic approach, incorporating these initiatives, is paramount to addressing the plastic waste crisis and fostering a sustainable future.

16.5 Conclusion The global issue of plastic pollution, driven by human consumption habits, has led to severe environmental contamination. Although current research has not conclusively confirmed the risks of microplastics within the human body (WHO, 2019), policymakers and the public alike should take action to reduce plastic released into the environment. These actions will yield significant benefits for the environment and ecosystems. This chapter proposes several social tools to minimize and eliminate plastic waste. Individuals, communities, businesses, and governments should all take proactive measures to change lifestyle habits and consumption patterns, reducing dependence on and emissions of plastics to protect our oceans and the environment. Participation in community activities and education for schools and the public are crucial avenues for changing individual consumption behaviors and reducing plastic waste. By altering these individual behaviors, we can influence mass consumption patterns and encourage producers to manufacture more environment-friendly products. Furthermore, through interdisciplinary and international cooperation, innovative materials and manufacturing processes can be developed to decrease the environmental footprint of plastics while simultaneously promoting sustainable economic and social development.

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17 Technologies for Removal and Remediation of Microplastics Sanket Dey Chowdhury1, Sudeep Kumar Mishra1, Puspendu Bhunia1, Rao Y. Surampalli2, and Tian C. Zhang3 1

Environmental Engineering, School of Infrastructure, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha, India Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 3 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 2

17.1 Introduction An unrestricted growth in plastic production due to the ever-increasing demand for plastic products has resulted in a 20-fold increase in global plastic production over the last 50 years (Geyer et al., 2017). It has been estimated that to date, around 9,200 million metric tons of plastics have been produced ever since the initiation of plastic production in 1950 (Walker & Fequet, 2023), which is expected to climb up to 12,000 million metric tons by 2050 (Ding et al., 2019). The global plastic production touched 368 million metric tons in 2019 (Walker & Fequet, 2023), which is predicted to be twice in the next two decades (Lebreton & Andrady, 2019). Most of the produced plastics have been designed for single-use purposes, escalating plastic waste generation and the risk of plastic pollution (Borrelle et al., 2020). Out of the total plastic waste generated globally, only 9% gets recycled, 12% gets incinerated, and the remaining 79% prowls in the midst of natural ecosystems (Geyer et al., 2017). Depending on the particle size, plastics can be broadly classified into four types: macroplastics (>25 mm), mesoplastics (5–25 mm), microplastics (MPs) (100 nm–5 mm), and nanoplastics ( 99.9

Aslan et al. (2016)

Four PAN nanofiber membranes were used: control (M1), negatively charged (M2), neutral (M3), and positively charged (M4) The Porosity of the prepared membranes: 65.1–86.4% Influent flux to different membranes: M1 = 1,452.4 ± 17.8 L/m2-h, M2 = 1,260.7 ± 74.3 L/m2-h, M3 = 867.1 ± 31.2 L/m2-h, and M4 = 860.6 ± 38.6 L/m2-h

M1: 12.3, M2: 67.9, M3: 89.2, M4: 99.3

Wang et al. (2020a)

The influent concentration of MPs was 17.88 items/L Rate of filtration: 7–10 m3/m2-h

M1: 2.3, M2: 3.3, M3: 14.9, M4: 89.9

85

Sarkar et al. (2021)

• Rapid sand filtration

Wastewater

A mixture of melamine, PVC, LDPE, and nylon

1,150 ± 80

Adsorption

Water

PS

1

• • • • • •

Filter bed specifications: size of sand particles = 1.1–1.5 mm, bed size: 84 m2, and bed depth = 0.95 m The influent concentration of the MP mixture was 1.08 ± 0.28 mg/L Rate of filtration: 6.68 m3/m2-s Filter bed specifications: size of sand particles = 0.9 mm and bed size: 29.96 m2

75.49

Bayo et al. (2020)

Sponge prepared from chitin and graphene oxide was used as the adsorbent The adsorption capacity of the sponge for the unmodified PS, aminemodified PS, and carboxylate-modified PS was compared Adsorption isotherm study: pH was varied between 4 and 10, and the PS concentration was varied between 1 and 15 mg/L

Unmodified PS: 89.8, Amine-modified PS: 88.9, Carboxylatemodified PS: 72.4

Sun et al. (2020)

(Continued)

Table 17.1 (Continued) MP remediation technology

Environmental matrix

Type of MPs

Particle size (μm)

Adsorption

Deionized water

PS

0.055

Adsorption

Water

PMMA, PVDF, and PS

0.1–0.2

Adsorption

Tap water

PE and fleece shirt fibers

PE: 10, fleece shirt fibers: not specified

Operational conditions

• • • • •

Adsorption

Water

PS

1

•

Removal efficiency (%)

Reference

Zinc-aluminium (Zn-Al) layered double hydroxides (LDHs) were used as adsorbents Adsorption isotherm study: PS concentration: 250 mg/L, mass of the adsorbent: 5 mg, pH: 6.5, and shaking speed: 200 rpm

96–100

Tiwari et al. (2020)

Zirconium metal-organic framework-based foam materials were used as adsorbents

PMMA: 88.2 ± 1.7, PVDF: 90.1 ± 2.1, PS: 85.7 ± 4.8

Chen et al. (2020)

Biochar produced from the slow pyrolysis of the bark of Scots pine (Pinus sylvestris) at 475 C as an adsorbent Adsorption study: 20 g of biochar was used, and 2 g of PE particles and 2 g of fleece shirt fibers were added to each column

PE: 100, fleece shirt fibers: 100

Siipola et al. (2020)

Cellulose nanofiber aerogel modified with 2, 3-epoxypropyl trimethyl ammonium

Adsorption capacity: 146.38 mg of PS/g of aerogel

Zhuang et al. (2022)

• Adsorption by marine microalgae

Seawater

PS (fluorescent MPs)

20

Adsorption by marine microalgae

Seawater

PS

0.05–0.5

Density separation

Marine sediment

A mixture of PE, PP, PS, LDPE,

200–400 and 800–1,000

• • • • •

chloride was used as an adsorbent Adsorption isotherm study: PS concentration: 50–150 mg/L, contact time: 5–120 min, and pH: 5–9 An edible marine microalgae (seaweed), Fucus vesiculosus, was used as an adsorbent Adsorption study: PS concentration: 2.65 mg/L, surface area of each side of distal tips of the microalgae: 4–6.9 cm2, shaking speed: 1 rpm, temperature: 10 C, and contact time: up to 120 min

94.5

Sundbaek et al. (2018)

A unicellular green algae, Pseudokirchneriella subcapitata, was used as an adsorbent Adsorption study: adsorbent added: 107 cells/mL, PS concentration: 10 mg/L, and adsorption time: 2 hr

Removal of positively charged PS > Removal of negatively charged PS

Nolte et al. (2017)

Four brine solutions, such as NaI, NaCl, and NaBr, and ZnBr2 were used

NaCl: >90, NaBr: >90, NaI: 95, ZnBr2: 95

Quinn et al. (2017)

(Continued)

Table 17.1 (Continued) MP remediation technology

Environmental matrix

Type of MPs

Particle size (μm)

Operational conditions

•

HDPE, nylon, PVC, and PET

• Density separation

Organic-rich sediment

A mixture of PP, PE, PVC, and PET

Mean surface area: 0.31–0.43 mm2

• • •

Density separation

Soil

LDPE, PP, PS, PVC, and PET

63–1,000

• • •

Removal efficiency (%)

Reference

ZnCl2 solution was used as the extraction solution ZnCl2 solution was poured into a sedimentMP isolation unit of 5.2 cm diameter and 37.5 cm height MPs were added to the solution, and the mixture was stirred for 5 min, followed by a resting period of 5 min The mixture was left for 24 hr

90.7 ± 7.7

Vermeiren et al. (2020)

CaCl2 solution was used for MP extraction Centrifugation was done to separate MPs from soil

LDPE: 98.1, PP: 97.7, PS: 97.5, PVC: 97.5, PET: 94.9

Grause et al. (2022)

66.67 g of clean sediment, 0.066 g of MPs, and 200 mL of brine solution (each in a separate beaker) were added to a 400 mL glass beaker The mixture was stirred at 300 rpm for 3 min, followed by 10 min of settling period

• Floatation

Soil

LDPE and PP

LDPE: 93; Freshwater: Medium (PE, PP, PET, PS, PVC, and PU): 84; Sediment: Medium (PE, PP, PET, PS, PVC, and PU): 78

Grbic et al. (2019)

The concentration of each MP: 100–1,000 mg/L Dosages of each coagulant (polyaluminum chloride (PAC) and ferric chloride (FeCl3)): 30–180 mg/L The initial pH was 7 Rapid mixing for 1 min at 500 rpm (PAC) and 400 rpm (FeCl3), followed by slow mixing for 15 min at 100 rpm and 30 min sedimentation

PAC: PE: 29.70, PS: 77.83 FeCl3: PE: 16, PS: 62

Zhou et al. (2021a)

40.5–54.5

Wang et al. (2020b) (Continued)

Table 17.1 (Continued) MP remediation technology

Environmental matrix

Type of MPs

Particle size (μm)

Coagulation

Drinking water

PE

1 mm) MPs from various environmental matrices including freshwater, seawater, and sediments. It was reported that 92% of small MP particles (PE and PS) and >93% of large MP particles (PE, PS, PET, PU, PP, and PVC) were recovered from seawater using magnetic separation. An 84% and 78% recovery of medium MPs (PE, PP, PET, PS, PVC, and PU) from freshwater and sediments, respectively, was also reported by Grbic et al. (2019) (Table 17.1). The removal of MPs from water by magnetic separation is governed by the shape and size of MP particles, the pH of the aquatic solution, and the concentration of nanoscale magnetic adsorbents (Gao et al., 2022). During the magnetic separation of MPs, the amount of magnetic adsorbents should exceed the amount of MP particles present in the water matrix. To ensure this, magnetic adsorbents are added to water/wastewater in abundance. Thus, the complete elimination of the externally added magnetic beads has been a major concern regarding the magnetic separation process, especially during its practical applications in WWTPs and DWTPs (Tang et al., 2021). The regeneration of magnetic particles by thermal treatment, followed by their recycling can be a good strategy; however, it does not negotiate the concern associated with the removal of the magnetic adsorbent residuals. Again, the performance of the magnetic separation technique is satisfactory in removing MPs from aquatic matrices, but the recovery of MPs from sediments is not up to the mark due to the nonspecific binding and soil (Nabi & Zhang, 2022).

17.2.2

Chemical Technologies

From the extensive literature, it has been observed that there are broadly two chemical MP remediation technologies, such as coagulation and agglomeration (Chen et al., 2021a; Ma et al., 2019a, b; Wang et al., 2020b) and advanced oxidation processes (AOPs) (Ali et al., 2016; Tofa et al., 2019; Uheida et al., 2021), which gained significant attention from researchers over the last few years. Each of the aforementioned technologies is elaborated below.

17.2.2.1 Coagulation and Agglomeration

To ensure substantial removal of colloidal MP particles from water and wastewater matrices, chemical reagents, also known as coagulants, are added externally, causing destabilization of colloidal MP particles through surface charge neutralization. This process is known as coagulation (Sonal & Mishra, 2021), which is followed by flocculation, sedimentation, and filtration to ensure substantial removal of MPs from aquatic matrices (Nabi & Zhang, 2022). Of late, various types of coagulants are employed to facilitate the eradication of colloidal MPs, of which aluminum salts (e.g., alum, polyaluminum chloride (PAC), etc.) and ferric salts (e.g., ferric chloride (FeCl3.6H2O)) are extensively used (Gao et al., 2022; Zhou et al., 2021a).

17.2 Microplastic Remediation Technologies

On the other hand, agglomeration is the process of separating MPs from water/wastewater matrices using organosilanes that attach to the surface of MPs, thus forming larger agglomerates, which stabilize due to the formation of a solid hybrid silica by water-induced sol–gel process (Herbort & Schuhen, 2017). Some of the commonly used organosilanes employed in the agglomeration of MP particles in aquatic matrices are n-butyltrichlorosilane, isooctyltrichlorosilane, (3-chloropropyl)trichlorosilane, etc. (Sturm et al., 2021). In the coagulation of colloidal MPs, immediately after the addition of coagulants, rapid mixing of the suspension is carried out for 1 min to ensure the complete dispersion of the coagulant in the solution as well as to facilitate colloidal MP particles to overcome the energy barrier between each other, namely electrostatic repulsion and van der Waals force of attraction. The van der Waals force of attraction is inversely proportional to the sixth power of the distance between the colloidal MP particles. At a greater distance, the net force acting between two MP particles is an electrostatic repulsive force, and it becomes attractive only when two particles come very close to each other by overcoming the maximum net repulsive force, also known as the energy barrier, occurring at a certain distance from a colloidal MP particle (Peavy et al., 1985). Once colloidal MP particles cross the energy barriers of other MP particles after the rapid mixing, the slow mixing of the solution is conducted for 15–20 min to encompass the floc formation. After that, the stirring is stopped, and the flocs containing MP particles are allowed to settle by gravity (Figure 17.9). The entire process can be simulated in a jar test (Peavy et al., 1985). Finally, the flocs are removed, and the MP particles are filtered out. The coagulation process largely depends on the pH of the medium, the types and dosages of coagulants, and the characteristics of MPs, such as size, shape, and density (Zhang et al., 2021a). Coagulation of colloidal MP particles, with the help of trivalent metallic salts (coagulants), in water or wastewater matrices may take place in one (or more) of the four mechanisms: ionic layer compression (Figure 17.10), charge neutralization and adsorption (Figure 17.11), sweep coagulation (Figure 17.12), and interparticle bridging (Figure 17.13) (Gao et al., 2022; Larue et al., 2003; Peavy et al., 1985). In ionic layer compression, with the increase in the coagulant dosage, the ionic concentration in the solution increases, which compresses the ionic layer, predominantly composed of counter ions, surrounding the colloidal MPs toward the surface of the MPs. If the ionic layer is compressed to such an

Figure 17.9

Schematic Representation of the Coagulation/Flocculation Process (Jar Test)

509

510

17 Technologies for Removal and Remediation of Microplastics

Figure 17.10

Mechanisms of Microplastic Removal via Ionic Layer Compression

Figure 17.11

Mechanisms of Microplastic Removal via Charge Neutralization and Adsorption

extent that the van der Waals force of attraction becomes prevalent, the energy barrier disappears, promoting the attachment of MP particles (Figure 17.10). When identical MP particles come close to each other, due to the presence of similar ionic clouds surrounding the colloidal MP particles (mostly embracing negative surface charges), an electrostatic repulsive force acts between them. As a result, the system (aqueous solution) remains stable. After the addition of coagulants, especially aluminum salts, aqua metallic cations are formed due to the chemical reactions between aluminum ions (Al3+) and water and become a part of the ionic cloud (Gao et al., 2022). Consequently, the cations and anions neutralize each other, dissipating the ionic cloud surrounding the surface of MP

17.2 Microplastic Remediation Technologies

Figure 17.12

Mechanisms of Microplastic Removal via Sweep Coagulation

Figure 17.13

Mechanisms of Microplastic Removal via Interparticle Bridging

particles. When MP particles come in contact with each other, the adsorption of an MP particle on the neutralized surface of the other MP particle takes place due to the prevalence of the van der Waals force of attraction (Figure 17.11). In sweep coagulation, the colloidal MP particles present in the suspension get entrapped in the amorphous and gelatinous flocs or attached to the flocs due to their sticky nature. Since these flocs are heavier than water, they settle down with time embracing colloidal MPs with them (Figure 17.12) (Peavy et al., 1985). In interparticle bridging, numerous colloidal MP particles get attached to the surface of large molecules formed during the dissociation of aluminum and ferric salts in water or to the highly reactive surface of externally added linear or branched synthetic polymers, forming a settleable mass (Figure 17.13). The removal of MPs from water by agglomeration has been pioneered by Herbort and Schuhen (2017), in which organosilanes embracing one organic group and three reactive groups are employed to facilitate the formation of agglomerates. First of all, the organic group of organosilanes interacts with the MP particles and gets attached to the surface

511

512

17 Technologies for Removal and Remediation of Microplastics

of MPs, thereby trapping MPs inside the agglomerates. Then, the reactive groups of organosilanes form a solid hybrid silica gel to chemically attach the MP particles by a waterinduced sol–gel process. In the first step of the sol–gel process, the hydrolysis of reactive groups to super-reactive silanols takes place, followed by the condensation of silanols, forming siloxane bonds (Sturm et al., 2020). Subsequently, stable agglomerates are produced. Zhou et al. (2021a) employed PAC and FeCl3 coagulants to remove PE and PS (200–400 μm) MPs from water at an initial pH of 7. The optimum dosage of PAC was found to be 90 mg/L, ensuring 77.83% and 29.70% removals of PS and PE, respectively. On the other hand, for FeCl3, the optimum dosage was 120 mg/L, portraying around 62% and 16% removals of PS and PE, respectively. The charge neutralization and adsorption were reported as the predominant mechanisms behind the coagulation of PS and PE (Table 17.1). Wang et al. (2020b) employed the coagulation/sedimentation process in an advanced DWTP to remove a mixture of MP particles, containing PE, PP, and PET, from the Yangtze River water in China and obtained a 40.5–54.5% removal of MPs. Ma et al. (2019b) examined the potential of FeCl3 6H2O coagulant to separate PE MPs ( PP > LDPE. The overall volume reduction of the parent PS, PP, and LDPE due to the exposure to UV light for 12 months was 100%, 19.5%, and 95%) at 1.42 V vs. reversible hydrogen electrodes with promising FA productivity rate of 4.87 mmol cm−2 h−1, which is 1.14 times of NiCo2O4 rod-shaped fiber by oxidation of EG (Figure 18.1b and c) (Mao et al., 2023). In a similar study for electrocatalytic upscaling of PET plastics, Zhou et al. reported the synthesis of bifunctional electrocatalyst CoNi0.25P (nickel-modified cobalt phosphide) that can convert PET plastics to value-added chemicals (PTA and potassium diformate), and H2 fuel. Initially, PET is readily hydrolyzed into PTA and EG in an aqueous KOH solution at 60 C with a high yield of 96.7%. The PET hydrolysate, used in membrane-electrode assembly electrolyzer, as analyte, shows selective EG oxidation to FA. Further acidification of PET electrolyte with formic acid revives pure PTA, and the remaining liquid is crystallized into potassium diformate (KDF) (Zhou et al., 2021). The Sankey diagram of mass flow analysis (Figure 18.1d) illustrates that 1 kg of PET feedstock ultimately produces 818.5 g of PTA, 389.2 g of FA, and 16.9 g of H2 (Zhou et al., 2021). In another study, Xiao et al. performed acid hydrolysis with H2SO4 for depolymerization followed by the electrochemical conversion of polyamide-66 into adipic acid and hexamethylenediamine using Ni3S2@Fe2O3 as electrocatalyst. Excess acid is removed via a base treatment. Hexamethylenediamine is then electrolytically oxidized to produce adiponitrile, which, along with adipic acid, can be reused to produce new polyamide-66 (Xiao et al., 2023). Interestingly, Pichler and coworkers found that PE can be degraded under acidic conditions, such as with nitric acid, to form dicarboxylic acids, primarily 22% glutaric acid and 44% succinic acid using fluorine-doped tin oxide as working electrode. These acids can undergo electrolysis to produce gaseous hydrocarbons, i.e., propylene and ethylene, respectively (Pichler et al., 2021). Nevertheless, harsh conditions, such as fuming nitric acid, can be detrimental to electrochemical devices and catalyst. Consequently, there is a need for milder methods for chemical pretreatment for depolymerization. To address this issue, the utilization of redox-tunable radicals or molecules as homogenous catalyst facilitates the interaction between electrode and solid polymers. Remarkably, Yan et al. (2022) provided evidence of inert C─C bond breaking of PS using N-hydroxyphthalimide as a redox mediator. N-hydroxyphthalimide oxidizes to a phthalimide-N-oxyl radical, which further reacts with the PS backbone, resulting in C─C bond cleavage and C─H oxygenation. The products obtained were identified as benzaldehyde, 2-diphenylethanone, benzoic acid, and benzyl. For the purpose of demonstrating its feasibility, PS was subjected to electrolysis at a voltage of 1.5 V compared to a silver/silver

551

(a) Microplastics H2

hydrolysate Hg/HgO (1M KOH)

H 2O

Mn0.1Ni0.9Co2O4–δ

60 40

0

1.42

1.52

1.62

1.72 Potential (V vs RHE)

1.82

Insoluble: 33.4

12 9 6 3 0

1.42

1.52

1.62 1.72 Potential (V vs RHE)

1.82

Electrolysis

20

CO32– Carbonate

PTA: 815.8

80

O–

Formate +

(d) NiCo2O4 Mn0.1Ni0.9Co2O4–δ

15

O –2e–

HO O– C—C cleavage Glycolic acid

Hydrolysis

Faradiac efficiency (%)

100

(c)

O

Terephthalate: 835.5

Mn0.1Ni0.9Co2O4–δ

18

Glycoladehyde

PET: 1000

NiCo2O4

OH

–2e–

H2O: 333.3

120

OH EG

EG: 312.2

Anode Formate productivity (mmol cm–2 h–1)

(b)

Cathode

HO

FA: 389.2

e– e– –2e– e– – e e– O

PET

H2: 16.9

Figure 18.1 (a) Schematic of Three-Electrode Setup for PET Upcycling into FA Using Mn0.1Ni0.9Co2O4-δ Rod-Shaped Fiber Electrocatalyst. (b) Faradaic Efficiency Over Mn0.1Ni0.9Co2O4-δ Rod-Shaped Fiber at Varying Potentials, with Error Bars Representing the Standard Deviation of the Measurements, and (c) FA Productivity Over Mn0.1Ni0.9Co2O4-δ Rod-Shaped fiber. (Source: Reproduced from Mao et al. (2023), copyright 2023, with permission from Elsevier) (d) Sankey diagram illustrating the mass flow in PET upcycling. Inset displays a photograph of the separated high-purity PTA. (Source: Reproduced from Zhou et al. (2021), copyright 2021, with permission of Springer Nature)

18.5 Application of Chemical Catalysts

chloride reference electrode. The electrolysis continued until all the initial PS was converted, resulting in the formation of 12% monomers and dimers. Redox mediators including polyoxometalates, silver ions, vanadium complexes, and active chlorine species are also being explored as potential homogeneous catalysts for electrochemical plastic upcycling (Cho et al., 2023). These advancements underscore the potential of electrocatalytic upcycling as a sustainable and efficient method for managing polymer waste. By transforming waste into valuable resources, this approach not only mitigates environmental impacts but also supports the development of a circular economy, fostering innovation in waste management and resource recovery.

18.5 Application of Chemical Catalysts The utilization of chemical catalysts in the process of converting polymers into highervalue products is a crucial breakthrough in promoting sustainable waste management. Chemical catalysts entail the transformation of polymeric polymers into shorter chains or their constituent monomers, which can then be utilized as feedstocks or fuels and subsequent production of valuable products including acids, hydrogen, syngas, and carbonaceous materials (Chu et al., 2022; Sajwan et al., 2024). Therefore, the initial step involves depolymerization, used for oxygen-containing plastics, such as PET, polyamides, and polycarbonate. The second step comprises chemical upcycling methods, wherein waste plastic undergoes chemical conversion into valuable products (Chen et al., 2021). The predominant techniques for chemical upcycling of polymers are hydrogenolysis, aminolysis, solvolysis, and pyrolysis. Hydrogenolysis enables the selective depolymerization of polyolefins into liquid fuels within certain molecular weight ranges by breaking the C─C bonds. For instance, Celik et al. (2019) demonstrated the effectiveness of platinum nanoparticles supported on SrTiO3 nanocuboids by atomic layer deposition (Figure 18.2a) for upcycling of polyolefins. These nanoparticles were able to catalyze the hydrogenolysis of PE at a temperature of 300 C in the presence of hydrogen gas. This reaction resulted in the formation of high-quality liquid products, such as waxes and lubricants, with a relatively narrow range of molecular sizes. Remarkably, Wang et al. (2022b) fabricated zinc-based catalyst (ZnX2), i.e., zinc chloride (ZnCl2) and zinc bis[bis(trimethylsilyl)amide] [Zn(HMDS)2] for upcycling of mixed polymers poly(bisphenol A carbonate) (BPA-PC) and PET. The amino-alcoholysis method used during chemical catalyst upcycling involves the depolymerization of BPA-PC using chiral amino alcohols as catalysts, with the assistance of ZnX2, under mild reaction conditions. Furthermore, this approach successfully facilitated the progressive depolymerization of BPA-PC/PET mixed plastics. The conversion of BPAPC involved the production of BPA and chiral 2-oxazolidinone, which was then followed by the retrieval of bis(2-hydroxyethyl) terephthalamide (BHETA) from PET. This strategy showcases a novel approach to upcycle BPA-PC plastic waste into BPA and valuable chiral compounds, hence achieving diverse transformation.

553

554

18 Catalysis for the Upcycling of Polymers

(a)

10 nm

50 nm

0

1

(b)

2 3 Diameter (nm) HO

BPA + Oxazolidinone PET

NH2 Ph Step 1

Zn(HMDS)2 r.t., 3 h

BPA 1.98 g, 87% 1b 1.50 g, 92%

HO BPA-PC + PET Plastic Mixture

5 nm

NH2 Ph Step 1

ZnCl2 r.t., 24 h

BPA + Oxazolidinone PET Filtration BPA + Oxazolidinone Purification 1b

BPA + Oxazolidinone 1b

+

+

PET

PET

Step 2 Zn(HMDS)2H2N 80 °C, 10 h Purification BHETA BHETA 2.34 g, 93%

5

BPA-PC 2.54 g PET 1.92 g

Filtration Purification

4

OH

H2N

BPA 1.89 g, 83% 1b 1.48 g, 91%

OH Zncl2 Step 2 80 °C, 15 h BHETA

Purification

BHETA 2.25 g, 89%

Figure 18.2 (a) Electron micrographs of platinum-supported SrTiO3 nanocuboids by atomic layer deposition. Inset displays platinum distribution over SrTiO3 nanocuboids (Source: Reproduced from Celik et al. (2019), copyright 2019, with permission of the American Chemical Society). (b) Schematic of stepwise breakdown of BPA-PC/PET mixed polymers using Zn(HMDS)2 and ZnCl2 (Source: Reproduced from Wang et al. (2022b), copyright 2022, with permission of the American Chemical Society)

In another notable study, Ogiwara and Nomura (2023) synthesized pentamethylcyclopentadienyl)titanium(IV) trichloride (Cp∗TiCl3) for PET depolymerization into morpholine amides, for which aminolysis was carried out using morpholine. Thus, utilization of chemical catalysts in polymer upcycling marks a pivotal step toward sustainable plastic waste management. Future research should aim at improving catalytic efficiency and process sustainability that will be critical in scaling these technologies, ultimately contributing to a greener and more circular economy.

References

18.6 Conclusion Plastics play a crucial role in modern society due to their long-lasting nature, efficiency, and cost-effectiveness. Nevertheless, the increasing abundance of plastic garbage is becoming a significant issue, as plastics quickly depreciate in worth once their intended use is fulfilled. Furthermore, the durability of plastics and their lack of susceptibility to natural decomposition provide a concerning issue in terms of disposal, posing a significant risk to the ecosystem. Thus, efforts are afoot to curb improper plastic disposal followed by effective upcycling of polymer wastes. Notably, chemical upcycling is receiving significant interest as a promising catalytic approach to transform waste plastics, including PET, PE, PS, and others, into different fuels, functionalized polymers, and other valuable chemicals. This process directly affects the cost-effectiveness and feasibility of such materials. Often, catalytic upcycling methods are more energy-intensive and costly to implement when compared to mechanical recycling and incineration. The pursuit of more effective techniques and better catalysts for catalytic upcycling of existing polymers should emerge as a crucial future perspective for further research. Focus must be given to catalyst design and mechanistic understanding at the molecular level, thus highlighting the significant potential for technological advancement. For instance, it is essential to ensure the long-term resilience of electrocatalysts, particularly under high current densities, to successfully proceed from laboratory research to large-scale polymer upcycling in industry. Similarly, it is recommended for future research to refrain from utilizing extra organic feedstocks as sacrificial agents during photoelectrocatalytic polymer upcycling and instead concentrate on achieving high selectivity in the primary oxidation products of plastics, which will undoubtedly improve total profitability and feasibility of polymer upcycling on industrial scale. In addition, there is a lack of investigation into the environmental consequences and economic evaluation of the catalytic upcycling methods. Thus, it is advisable to explore such findings in the future, as they would offer a profound understanding of the efficacy of catalytic upcycling processes. Finally, the utilization of alternative renewable energy sources to drive polymer upcycling represents a promising strategy for addressing the management of primary pollutants in the contemporary world. By leveraging sustainable energy, reducing emissions, and advancing technology, this strategy not only addresses environmental concerns but also promotes economic and ecological sustainability.

References Alabi, O. A., Kehinde, I. O., Oluwaseun, A., & Olufiropo, E.,. A. (2019). Public and environmental health effects of plastic wastes disposal: A review. Journal of Toxicology and Risk Assessment, 5, 1–13. Argyle, M. D., & Bartholomew, C. H. (2015). Heterogeneous catalyst deactivation and regeneration: A review. Catalysts, 5, 145–269. Balu, R., Dutta, N. K., & Roy Choudhury, N. (2022). Plastic waste upcycling: A sustainable solution for waste management, product development, and circular economy. Polymers, 14, 4788.

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Celik, G., Kennedy, R. M., Hackler, R. A., Ferrandon, M., Tennakoon, A., Patnaik, S., LaPointe, A. M., Ammal, S. C., Heyden, A., Perras, F. A., & Delferro, M. (2019). Upcycling single-use polyethylene into high-quality liquid products. ACS Central Science, 5, 1795–1803. Chen, H., Wan, K., Zhang, Y., & Wang, Y. (2021). Waste to wealth: Chemical recycling and chemical upcycling of waste plastics for a great future. ChemSusChem, 14, 4123–4136. Cho, J., Kim, B., Kwon, T., Lee, K., & Choi, S. I. (2023). Electrocatalytic upcycling of plastic waste. Green Chemistry, 25, 8444–8458. Chu, M., Liu, Y., Lou, X., Zhang, Q., & Chen, J. (2022). Rational design of chemical catalysis for plastic recycling. ACS Catalysis, 12, 4659–4679. Deng, L., Guo, W., Ngo, H. H., Zhang, X., Wei, D., Wei, Q., & Deng, S. (2023). Novel catalysts in catalytic upcycling of common polymer wastes. Chemical Engineering Journal, 471, 144350. Ellis, L. D., Rorrer, N. A., Sullivan, K. P., Otto, M., McGeehan, J. E., Román-Leshkov, Y., Wierckx, N., & Beckham, G. T. (2021). Chemical and biological catalysis for plastics recycling and upcycling. Nature Catalysis, 4, 539–556. Guselnikova, O., Semyonov, O., Sviridova, E., Gulyaev, R., Gorbunova, A., Kogolev, D., Trelin, A., Yamauchi, Y., Boukherroub, R., & Postnikov, P. (2023). “Functional upcycling” of polymer waste towards the design of new materials. Chemical Society Reviews, 52, 4755–4832. Hahladakis, J. N., Velis, C. A., Weber, R., Iacovidou, E., & Purnell, P. (2018). An overview of chemical additives present in plastics: Migration, release, fate and environmental impact during their use, disposal and recycling. Journal of Hazardous Materials, 344, 179–199. Hiller, W., Pasch, H., Macko, T., Hofmann, M., Ganz, J., Spraul, M., Braumann, U., Streck, R., Mason, J., & Van Damme, F. (2006). On-line coupling of high temperature GPC and 1H NMR for the analysis of polymers. Journal of Magnetic Resonance, 183, 290–302. Jiang, M., Wang, X., Xi, W., Yang, P., Zhou, H., Duan, J., Ratova, M., & Wu, D. (2024). Chemical catalytic upgrading of polyethylene terephthalate plastic waste into value-added materials, fuels and chemicals. Science of the Total Environment, 912, 169342. Jung, H., Shin, G., Kwak, H., Hao, L. T., Jegal, J., Kim, H. J., Jeon, H., Park, J., & Oh, D. X. (2023). Review of polymer technologies for improving the recycling and upcycling efficiency of plastic waste. Chemosphere, 320, 138089. Kosloski-Oh, S. C., Wood, Z. A., Manjarrez, Y., de los Rios, J. P., & Fieser, M. E. (2021). Catalytic methods for chemical recycling or upcycling of commercial polymers. Materials Horizons, 8, 1084–1129. Linger, J. G., Vardon, D. R., Guarnieri, M. T., Karp, E. M., Hunsinger, G. B., Franden, M. A., Johnson, C. W., Chupka, G., Strathmann, T. J., Pienkos, P. T., & Beckham, G. T. (2014). Lignin valorization through integrated biological funneling and chemical catalysis. Proceedings of the National Academy of Sciences, 111, 12013–12018. Liu, F., Gao, X., Shi, R., Guo, Z., Tse, E. C. M., & Chen, Y. (2023). Concerted and selective electrooxidation of polyethylene-terephthalate-derived alcohol to glycolic acid at an industrylevel current density over a Pd−Ni(OH)2 catalyst. Angewandte Chemie International Edition, 62, e202300094. Malkin, A. Y. (2009). The state of the art in the rheology of polymers: Achievements and challenges. Polymer Science, Series A, 51, 80–102. Mao, Y., Fan, S., Li, X., Shi, J., Wang, M., Niu, Z., & Chen, G. (2023). Trash to treasure: Electrocatalytic upcycling of polyethylene terephthalate (PET) microplastic to value-added products by Mn0.1Ni0.9Co2O4-δ RSFs spinel. Journal of Hazardous Materials, 457, 131743.

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19 Biodegradable Bioplastics Neha Sharma, Koran Barman, Nehaun Zargar, Almeenu Rasheed, and Sovik Das* Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, India

19.1 Production of Bioplastics The pollution caused by plastics and microplastics globally is inspiring a sustainable and plastic-free environment, which has further stimulated intense research on eco-friendly alternatives. In this regard, bioplastics, also known as “bio-based polymers” or “biodegradable plastics,” have been hailed as a solution to substitute conventional plastics (Arikan & Ozsoy, 2015). Generally, plastics are categorized into two types based on their origin, namely, bio-based and fossil-based plastics. Bio-based plastics are primarily or partially produced from biological sources like organic waste, algae, fungi, bacteria, and plants. In addition to this, bioplastics, such as polylactic acid (PLA), polyhydroxyalkanoates (PHA), and polyhydroxybutyrate (PHB), are directly derived from polymers that are naturally occurring in microbes and plants; whereas, fossil-based plastics are derived from petroleum-based materials (Nandakumar et al., 2021). Furthermore, bioplastics are created using biomass materials like wood, crop residue, corn stover, switchgrass, etc. These biomass materials are processed sequentially through processes like pretreatment, saccharification, detoxification of liquids, fermentation, purification, and bio-composite development (Brodin et al., 2017). Pretreatment processes, such as mechanical grinding, milling, scissor cutting, chipping, steam explosion, hot water treatment, microwave irradiation, and ultrasound irradiation, are used to modify the structure and chemical composition, and also reduce the particle size of the biomass by converting innate lignocellulosic biomass into simpler constituents, such as lactic acid and cellulose (Reshmy et al., 2021). Subsequently, the biomass can be directly saccharified by acidic hydrolysis through heating, which involves biomass degradation using cellulosic or hemicellulosic degrading microbes, such as Firmicutes, Proteobacteria, Ascomycetes, and Basidiomycetes (Hasunuma et al., 2013). After saccharification, the desired components are further fermented using a wide spectrum of microbes yielding various constituents which are then utilized for bioplastics production.

∗

Equal contributor.

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Cellulose, being most abundant in plants, can be used for the production of bioplastics through the lignocellulosic biomass extraction process. Some of the processes involved in the conversion of cellulose to bioplastics are delignification, removal of hemicelluloses, extraction of cellulose, surface modifications, and bioplastic composite production. The process of delignification removes lignin and hemicelluloses from the biomass using higher temperature (150–200 C) and pressure (3–10 atm) (Yang et al., 2019). Furthermore, the complete removal of the lignin, residual pectin, and hemicellulose is achieved through alkali treatments by utilizing compounds, such as NaOH and KOH (Boey et al., 2022; Samir et al., 2022). In addition to this, some of the major techniques used for cellulose extraction from lignocellulosic biomass are pulping, extrusion, micro fluidization, ultrasound treatments, ball milling, homogenization, etc. (Bari et al., 2019; Deepa et al., 2015). Through the process of pulping, cellulose is obtained from wood and can be transformed into various materials, including two main categories of cellulose-based bioplastics: regenerated cellulose and cellulose diacetates (Vroman & Tighzert, 2009). However, bioplastics sourced from natural origins can also be made through synthetic methods. The three main pathways for producing bioplastics are (a) bio-monomer polymerization, (b) modification of existing natural polymers, and (c) extraction from microorganisms (Di Bartolo et al., 2021; Quirino et al., 2021). Nowadays, various bioplastics, which are plant-derived thermoplastics, such as PLA, PHA, and polyethylene terephthalate (PET), are manufactured through fermentation of plant sugars, using microorganisms like Lactobacilli that aid in converting sugar to lactic acid. For example, for PLAs the resulting lactic acid is polymerized into low molecular weight PLAs, then depolymerized to form lactide, the cyclic dimer of PLA, and the ringopening polymerization of lactide creates high molecular weight PLA (Drumright et al., 2000; Garlotta, 2001). Bioplastics, such as PLAs, have significantly high tensile strength; however, these bioplastics have low thermal stability, crystallinity, and are brittle in nature. Similarly, PHAs are biocompatible and biodegradable, with high melting points and good tensile strength. Also, the partial crystalline nature of PHAs has been observed in various studies (Behera et al., 2022). Owing to its biodegradable nature and mechanical properties, such as tensile strength and elongation at break, bioplastics have widespread applications. Moreover, both ecological as well as carbon footprints get reduced due to the usage of bioplastics, as fossil carbons are substituted with bio-based carbons reducing the dependency on limited fossil fuels, eventually reducing greenhouse emissions. Furthermore, the production of bioplastics is energy-efficient and contributes to minimizing the extraction of fossil fuels (Ali et al., 2023; Arikan & Ozsoy, 2015). Thus, from the above discussion, it can be concluded that bioplastics present eco-friendly alternatives with comparable strength and stability to conventional plastics; hence, boosting the production of bioplastics can diminish reliance on conventional fuels and tackle environmental concerns. Additionally, various bioplastic production pathways, including bio-monomer polymerization and modification of natural polymers, highlight the resourcefulness of these alternatives. However, more dedicated research and developments are required in the field of production of bioplastics, such as reviewing the potential of novel raw materials and also investigating physical, chemical, thermal, and biological methodologies required for the bioplastics production for the reduction of the global reliance on fossil fuel-based plastics and fostering circular economy.

19.2 Standards and Guidelines to Test the Biodegradability of Bioplastics

19.2 Standards and Guidelines to Test the Biodegradability of Bioplastics Bioplastics are either biodegradable or bio-based, i.e., plastics derived from various biological sources, such as microorganisms, plants, and biological waste; or feature both these properties, i.e., bio-based and biodegradable, such as PHA, PLA, and PHB (Goel et al., 2021). Even though nonbiodegradable bioplastics, such as bio-polyethylene (bio-PE), bio-polyamide, and bio-polypropylene (bio-PP), are formed using green resources, such as biomass and corn, the nonbiodegradable ones persist in the ecosystem for a longer time behaving similarly to conventional plastics (Rahman & Bhoi, 2021). Also, it is essential to note that not all bioplastics derived from biological sources are biodegradable. However, certain petrochemical-based plastics are also categorized as bioplastic due to their biodegradable properties. With the growing application of various bioplastics with different compositions and properties, there is a vital requirement for the standardization and certification systems of these materials so as to comply with the various national and international regulations and quality standards in addition to appropriate categorization and labeling of the same. Also, these standards aid in defining the extent to which bioplastics can be categorized as biodegradable and/or compostable in a specific environment (Goel et al., 2021; Rashidi, 2022). In light of this, various test standards and protocols to evaluate the biodegradability and compostability of plastics have been developed by multiple international and national organizations like, International Organization for Standardization (ISO), Organisation for Economic Cooperation and Development (OECD), the American Society for Testing and Materials (ASTM), European Committee of Standardization (CEN), Association Francaise de Normalisation (AFNOR), Ente Italiano di Normazione (UNI), British Standards Institution (BSI) to name a few (Folino et al., 2023; Goel et al., 2021; Rashidi, 2022). For brevity, only the important standards developed by these institutes to measure the biodegradability of bioplastics in different environmental matrixes and conditions are discussed below.

19.2.1

Biodegradation in Aerobic Soil Environment

The standard test methods utilized for estimating the rate of biodegradation of plastics under normalized soil environments are, ASTM D5988, ISO 17556, UNI 11462, EN 17033, and NF U52-001. In the ASTM D5988, UNI 11462, EN 17033, and NF U52-001 methods, the rate, and degree of aerobic biodegradability of plastic materials in soil are determined by measuring the evolved carbon dioxide during the biodegradation process. Similarly in the ISO 17556 method, the degree of biodegradation is quantified either by measuring the evolved carbon dioxide or oxygen demand during the test (Bettas Ardisson et al., 2014; Briassoulis et al., 2020; Folino et al., 2023; Goel et al., 2021; Šerá et al., 2020).

19.2.2

Biodegradation in Freshwater Environment

Mainly ISO 14851, ISO 14852, and ISO 14853 standards are used to measure the ultimate biodegradability of plastic in aerobic and anaerobic aquatic environments. The ISO 14851 method quantifies the degree and rate of biodegradation of bioplastics also by measuring the

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oxygen demand during the test. Similarly, ISO 14852 and ISO 14853 methods quantify the rate of biodegradation by measuring the evolved carbon dioxide and biogas during the tests, respectively (Folino et al., 2023; Goel et al., 2021).

19.2.3

Biodegradation in the Marine Environment

Primarily ISO 18830, ISO 16221, ASTM D6691, ASTM D7473/D7473M, and OECD 306 are the standard test methods used to determine aerobic biodegradation of plastic materials in the lab-scale marine environment. The ISO 18830, ASTM D6691, and ASTM D7473/D727M standard methods quantify biodegradation by measuring the oxygen demand, evolved carbon dioxide, and loss of dry weight during the test, respectively. Moreover, ISO 16221 utilizes five different methods to measure the ultimate biodegradability of plastics, and these are, the die-away test, closed bottle test, two-phased closed bottle, CO2 evolution test, and CO2 headspace test (Folino et al., 2023; Goel et al., 2021; Jayakumar et al., 2023).

19.2.4

Biodegradation During Composting

The rate and degree of biodegradation during aerobic composting are measured by ASTM D5338, ISO 14855-1, ISO 14855-2, ISO 14852, and EN14046 standards. In ISO 14855-1, ISO 14855-2, and ASTM D5338 standards, the degree and rate of bioplastic degradation is evaluated by measuring the evolved carbon dioxide during composting (Folino et al., 2023; Goel et al., 2021).

19.2.5

Biodegradation in Anaerobic Digestion

Multiple standard test methods are utilized to measure the degree and rate of anaerobic biodegradation of plastic in an anaerobic digester, such as ISO 15985, ISO 13975, ISO 14853, and ASTM D5511. In these test methods, the sample material is introduced to the methanogenic inoculum extracted from an anaerobic digester, which is only operated with pretreated household waste. Also, ISO 15985, ISO 13975, and ISO 14853 test methods differ among themselves in terms of the number and size of the reactor, solid content, test temperature, etc. (Goel et al., 2021).

19.2.6

Biodegradation in Aerobic Landfill

The degree and rate of anaerobic biodegradation of bioplastic in the accelerated landfill test environment is measured by the ASTM D5526 standard. In the test, the sample plastic is mixed with pretreated household waste while maintaining a temperature of 35 C, followed by the addition of methanogenic inoculum obtained from an anaerobic digester, which is operated with pretreated household waste (Goel et al., 2021). All the above-discussed standards specify multiple testing methods to quantify the degree and rate of biodegradation of bioplastics in different stimulated lab-scale environments. However, these standard test methods have multiple drawbacks, such as large-scale discrepancies between the rate and degree of biodegradation in real environment and laboratory tests. In addition, the optimal test environmental conditions, such as temperature, pH, and experiment duration specified in the standard methods, are unrealistic when compared to the actual environmental conditions, and these conditions are impossible to reproduce in a

19.3 Application of Bioplastics

full-scale waste treatment facility. Moreover, these standard test methods fail to reproduce the complex dynamics of the natural environment, and hence, these existing standards require an urgent modification for the development of more comprehensive standards that accurately represent the rate and degree of biodegradation of bioplastic in the natural environment (Folino et al., 2023; Jayakumar et al., 2023; Kjeldsen et al., 2018).

19.3 Application of Bioplastics Bioplastics can be widely used for different applications, such as food packaging, agriculture, medical, and automobiles. It has been reported that the use of bio-based polymers for food packaging applications has increased accounting for 65% of the total 2.11 million tonnes of bioplastic being produced across the globe (Narancic et al., 2020). These biodegradable plastics can be used as mulch film for agriculture purposes, which can be easily installed and are proven to be advantageous over conventional polyethylene (PE)-based mulch film owing to their biodegradability and assist in improving soil fertility (Akhir & Mustapha, 2022). Furthermore, PHA bioplastic has been successfully used to develop medical instruments like nerve and tendon repair devices. Also, PHB bioplastic is used for surgical tools like staples, pins, and sutures, as well as for cell and tissue engineering practices, including blood vessel and bone replacement, drug delivery, and cardiovascular patches. Likewise, bioplastic also stepped into the automobile sector, where these are used to manufacture different automobile parts, maintaining the eco-friendly portfolio of the company. Biopolymers, namely, polypropylene (PP), polyamides, and polyesters, are employed to develop different components of cars, including steering wheels, seats, dashboards, and airbag covers. Besides this, PP has also been used by the top car manufacturers, namely, Volkswagen and Daimler for developing crankshaft and engine-covering coaches, respectively (Phadke & Rawtani, 2023). Toyota also integrated bioplastic to manufacture 60% of the inner surface for their environment-friendly hybrid car (Jeong & Ko, 2016). Another milestone that can be a revolution in the automobile industry is the development of the first complete bioplastic-based car NOAH, which was developed by the Eindhoven University of Technology and which can end the dependence on nonrenewable sources as well as relieve the burden on landfills (Europeanbioplastics, 2018). Apart from this, bioplastic has also been used in computers, cell phones, mouse, keyboards, and chargers. In addition, blends of PLA bioplastic possessing high heat resistance have been employed in tablets, game consoles, and headphones (Phadke & Rawtani, 2023). Although the tensile strength and elastic modulus of the PLA bioplastic are lesser than PET, studies have suggested that these mentioned properties of PLA are comparable to PET and thus may be used for manufacturing bottles, films, and pouches to phase out PET plastic (Farah et al., 2016; Jariyasakoolroj et al., 2020). Remarkably, today many companies produce various types of bioplastics that are commercially employed for different applications. For example, Badische Anilin- und Sodafabrik produces compostable plastic Ecovio®, which is used in agricultural films, vegetable and fruit bags, and carrier bags. Moreover, carrier bags made from these bioplastics are strong

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enough to be utilized multiple times and are easily compostable at the end of their life. In addition, Avantium, a Netherlands-based firm, manufactures plant-based, recyclable, and biodegradable plastic material with a wide range of uses, including film, textiles, and packaging. These bioplastics provide an extended shelf life for packed goods and also possess increased mechanical strength, heat resistance, as well as emit 50–70% less carbon dioxide (Phadke & Rawtani, 2023). Bioplastic can also be used to synthesize the media, which provides a surface for microbial growth for the wastewater treatment process. For instance, Accinelli et al. (2012) examined the feasibility of bioplastic-based moving bed biofilm carriers (MBBC) for the removal of atrazine, bisphenol A, and oseltamivir from wastewater, resulting in removal efficiency of 66%, 34%, and 49%, respectively. Besides, bioplastic-based MBBC can also solve the problem of disposal of nonbiodegradable MBBC derived from conventional plastics. Undoubtedly, it can be concluded that bioplastics can be a promising solution to reduce the dependence on nonrenewable resources, eliminate recalcitrant plastic pollution, as well as reduce the quantity of landfillable waste. In addition, bioplastic also envisions the path of switching to sustainable and environment-friendly materials aligning with sustainable development goals and circular economy.

19.4

Limitations of Bioplastic

Bioplastics are the potential substitute for conventional plastics; however, despite several advantages, various limitations and technical challenges are linked with this environment-friendly material (Figure 19.1). For example, the use of first-generation feedstocks like

Benefits

Limitations

Utilization of renew

able feedstocks

Lower CO and oth 2 er GHG em

issions

Less dependence on

High cost of prod

uction

fossil fuels

Poor mechanical

Low solid waste gen

eration

Low carbon footprint compared to traditional plastics Production of biopla energy compared stic consumes less to conventional pla stics

Use of first-gene

ration crops as fee

Certain bioplastics

dstock

are non-biodegrad

able

Uncertain end-of

Bioplastic

Figure 19.1

properties

Benefits and Limitations of Bioplastics

-life management

19.4 Limitations of Bioplastic

potato, sugarcane, wheat, and corn to produce bioplastics raises food security issues and land use conflicts. Furthermore, biomass-derived bioplastics, such as bio-PE, bio-PP, and bio-PET, are nonbiodegradable, resulting in a similar threat like conventional plastics (Phadke & Rawtani, 2023). On the contrary, biodegradable bioplastics, which are degraded by microorganisms require specific conditions like pH, temperature, and humidity, depending upon the type of bioplastic in question, to degrade them completely. These optimum conditions might not always be feasible on the site; thus, dumping the bioplastics with the hope that it will be degraded completely seems to be unrealistic (Rahman & Bhoi, 2021). In order to avoid this, the establishment of a dedicated facility for the degradation of bioplastics providing necessary optimum conditions and particular microorganisms is required to ensure the complete degradation of bioplastics, which demands capital expenditure (Nanda et al., 2022). Furthermore, compostable bioplastics, which are a type of bioplastic, require composting facilities to degrade, and so far, not all cities across the globe are well equipped with these facilities. Thus, a considerable number of bioplastics eventually end up going into landfills, which are left undegraded in the absence of a suitable environment. Other concerns linked with bioplastics are high cost and low mechanical strength compared to conventional plastics, which limit their public acceptability (Abang et al., 2023). Along with that, some of the bioplastics are limited to particular use cases only, such as PLA bioplastic is suitable for low-moisture items like dry food packaging due to the higher transmission rate of water vapor by them. Besides, difficulties during processing bioplastic through conventional technologies are still a major hurdle for their production as well as scalability (Narancic et al., 2020). Consequently, these are the probable reasons that bioplastics have not yet found widespread application and acceptance despite possessing enormous potential. In this regard, further efforts are needed to address the associated limitations and technical challenges with bioplastics so that these can be adopted at a larger scale by the public. Further development should be focused on enhancing the mechanical properties of bioplastics without compromising their renewability, thus allowing them to compete better with conventional plastics. Moreover, the problem of nonbiodegradable bioplastics can be solved by using them for pyrolysis to recover gasoline and diesel, which can be further processed and employed for transportation purposes. Also, these bioplastics can be used during gasification to recover energy, thus solving the issue of disposal of nonbiodegradable bioplastics (Rahman & Bhoi, 2021). In addition, the requirement of land and establishment of proper facilities for the degradation of bioplastics makes this route expensive; however, if the negative environmental impacts of conventional plastics are considered, then this cost can be compromised. In addition, the public must also be encouraged to use bioplastics, which will not only assist in eliminating the negative impacts of conventional plastics but also encourage large-scale production of bioplastics curtailing the per unit production cost. Finally, it is important that proper awareness is required for the end users to understand that suitable conditions are compulsorily required for the degradation of the bioplastics, which will eventually lead to the disposal of the bioplastics only at designated places and thus eliminating its undesirable dumping into landfills.

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19.5

Environmental Sustainability of Bioplastics

Bioplastics are the potential substitute for conventional plastics for ending the reliance on finite fossil fuels and for boosting the global bio-economy. Replacement of conventional plastics by bioplastics seems to be a sustainable option for the longer term due to the production of the latter from renewable sources like biomass thus promoting the sustainable development goals (Brodin et al., 2017). Moreover, the ability of bioplastics to be degraded by microbes is their unique feature, hence alleviating the problem of plastic pollution as well as abating the deleterious environmental impacts caused by the accumulation of conventional plastics in the environment. However, well understanding of the optimum conditions under which microbes can degrade the bioplastic is very crucial for ensuring the complete degradation of bioplastics so that, these do not pile up in the environment like conventional plastics (Thakur et al., 2018). Furthermore, the replacement of conventional plastics with bioplastics sounds environment-friendly option as it generates fewer carbon footprints in comparison to conventional plastics thus this is beneficial in achieving the net zero target (Rosenboom et al., 2022). Overall, switching to bioplastics provides a better alternative to maintain the harmony between humans and the environment, which has been disturbed by the usage of non-environment-friendly conventional plastics.

19.5.1

Degradation Pathways of Bioplastic

Different steps are involved in the degradation of the bioplastic, namely, biodeterioration, bio-fragmentation, assimilation, and mineralization. During the biodeterioration, microbes colonize on the surface of the bioplastic, lowering its durability and strength, hence making it more susceptible to degradation. The rate of biodeterioration is controlled by the surrounding environmental conditions like pH, temperature, and humidity as microbes are highly sensitive to these conditions, thus accelerating or retarding degradation of bioplastic. Furthermore, biodeterioration is followed by bio-fragmentation, during which longer-chain biopolymers are broken down into monomers by the microbes. In the next assimilation step, these monomers penetrate the cell walls of microbes, where the bioplastic particles are utilized as carbon and energy sources for their growth. At last, during the mineralization step, different metabolites, including water, carbon dioxide, and methane, are produced as the result of the degradation of bioplastics (Idris et al., 2023). During this whole process, extracellular and intracellular enzymes act on the bioplastics leading to their degradation. These extracellular enzymes break longer-chain biopolymers into shorter chains outside the cell, while intracellular enzymes work inside the microbes to further degrade these shorterchain biopolymers (Bátori et al., 2018). These bioplastics can be either degraded aerobically or anaerobically depending upon the type of the microbes. The aerobic degradation of bioplastics occurs in the presence of oxygen, where microbes utilize bioplastics as a source of carbon and energy-producing water, carbon dioxide, and digested residue as by-products. On the contrary, anaerobic degradation of bioplastics takes place in an oxygen-free environment in the presence of microbes, resulting in the formation of methane, hydrogen sulfide, carbon dioxide, water, ammonia, and digested residue as end products (Folino et al., 2020). Moreover, the degradability of bioplastic is influenced by its physicochemical properties, such as surface area, hydrophobic or hydrophilic surface,

19.5 Environmental Sustainability of Bioplastics

molecular weight, and chemical structure. For example, the degradability of bioplastic decreases as the molecular weight increases, while degradability increases as surface area increases (Idris et al., 2023). Furthermore, degradation of the bioplastic generally occurs in three distinct surroundings, namely, soil, compost, and marine environment. Among them, the soil consists of different varieties of microbes; thus, degradation of bioplastics is more viable in soil than in aqueous media. Different microbes that are responsible for the degradation of the bioplastics and are present in the soil are Amycolatopsis, Streptomyces, Laceyella, Thermomactimyces, Nonomuraea, and Actinomadura (Ahsan et al., 2023). In the compost, bioplastics present with organic matter are converted into carbon dioxide and humus by microbes like Proteobacteria ascomycota, Tramates versicolor, and Fomes fomentarius. This process is generally suitable for bioplastics employed for food packaging, as the majority of the bioplastic recycling facilities do not process food contaminated with bioplastics (Ahsan et al., 2023). Furthermore, bioplastics also enter into the marine ecosystem as a result of improper disposal or runoff, and as a result microbes like Avanivorax, Bacillus, Tenacibaculum, Lepthotrix, Pseudomonas, Variovorax, Entrobacter, and Gracilibacillus present in the marine environment are responsible for degrading these bioplastics in these conditions (Ahsan et al., 2023). However, the degradation rate of the bioplastics is slower in marine as compared to soil and compost due to lower microbial diversity and seasonal variation of temperature in marine conditions (Emadian et al., 2017). Nevertheless, either faster or slower, bioplastics are capable of being broken down in different surroundings by microbes and do not accumulate in the environment unlike conventional plastics, which concentrate in the environment due to their persistent nature. Therefore, greater public adoption of these degradable bioplastics must be encouraged in order to eliminate the risks that the environment and living beings face from conventional plastics. Moreover, adaptation of bioplastics will also reduce the expense incurred by the country in the cleaning of plastic pollution every year due to their persistent nature in the environment.

19.5.2

LCA of Biodegradable Bioplastic

The life cycle analysis (LCA) studies on biodegradable bioplastics aid in determining the environmental sustainability of bioplastics by analyzing categories, such as land use, carbon footprint, and global warming potential (GWP). Studies on LCA indicate that conventional plastics, such as PET and PS, exhibit a GWP within the range of 2.4–5 tonne CO2 eq. per tonne of polymer, which is approximately two times greater than the GWP exhibited by bioplastics, such as PLA (0.5–2.9 tonne CO2 eq. per tonne of polymer) (Rosenboom et al., 2022). Moreover, studies demonstrate considerable greenhouse gas (GHG) emissions from 1 tonne of various polymers, such as poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) (0.32–16.5 tonne CO2 eq. per tonne of PHBH), polyethylene furandicarboxylate (PEF) (2.05–2.38 tonne CO2 eq. per tonne of PEF), starch-based PHB (1.96 tonne CO2 eq. per tonne of PHB), starch-based PBS (2.9 tonne CO2 eq. per tonne of PBS), and PHAthermoplastic starch (TPS) (4.8 tonne CO2 eq. per tonne of PHA-TPS), as described in Table 19.1 (Amasawa et al., 2021; Broeren et al., 2017; Dilkes-Hoffman et al., 2018). In addition, enhancing the usage of corn- and starch-based bioplastics aids in reducing GHG emissions by 25% and 80%, respectively, compared to conventional plastics

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Table 19.1 LCA of Different Bioplastics Type of bioplastic

Functional unit

Boundary condition

Impact category (Unit)

Observations

Reference

PLA

1 tonne of polymer

Cradle to gate

GWP (kg CO2 eq.)

0.5–2.9

AP (kg SO2 eq.)

7–21

Rosenboom et al. (2022)

P3HB

1 tonne of polymer

Cradle to gate

GWP (kg CO2 eq.)

−2.3 – 4

AP (kg SO2 eq.)

14–25

Starch-based PHB

1 kg of polymer

Cradle to grave

GWP (kg CO2 eq.)

1.96

NREU (MJ/kg)

40

EP (kg PO43− eq.)

1.7

2

Starch-based PBS

PLA bottle

1 kg of polymer

Cradle to grave

Agri. LU (m yr/kg)

1.3

Agri. LU (m2 yr/kg)

0.3

GWP (kg CO2 eq.)

2.9

NREU (MJ/kg)

70

EP (kg PO43− eq.)

1.9

GWP (kg CO2 eq.)

0.616

Broeren et al. (2017)

Broeren et al. (2017)

Tamburini et al. (2021)

Bottles required for 1 year of use (1,095 bottles)

Cradle to grave

HTP (kg 1,4-dB eq.)

0.218

PHBH

1 kg of polymer

Cradle to grave

GWP (kg CO2 eq.)

0.32–16.5

Amasawa et al. (2021)

PHA-TPS

1 kg of polymer

Cradle to grave

GWP (kg CO2 eq.)

4.8

DilkesHoffman et al. (2018)

1 tonne of polymer

Cradle to grave

NREU (MJ/kg)

33.8–39.3

GWP (kg CO2 eq.)

2.05–2.38

PEF

−4

AP (kg SO2 eq.)

27.5 × 10

EP (kg PO43− eq.)

5.90 × 10−4

3

Water use (m water use/kg)

0.05

Eerhart et al. (2012)

Agri. LU, agricultural land use; AP, acidification potential; DB, dichlorobenzene; EP, eutrophication potential; GWP, global warming potential; HTP, human toxicity potential; MJ, mega joules; NREU, non-renewable energy use; P3HB, poly(3-hydroxybutyrate); PBS, polybutylene succinate; PEF, polyethylene furandicarboxylate; PHA-TPS, thermoplastic starch (TPS) and polyhydroxyalkanoate (PHA) layered material; PHB, polyhydroxy butyrate; PHBH, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate); PLA, polylactic acid.

(Ali et al., 2023). However, studies indicate that the eutrophication potential due to the usage of starch (1.2–1.9 g PO43− eq. per kg of polymer) for the manufacture of bioplastics is four times higher than that of petrochemical plastics, due to the usage of chemicals and pesticides for higher yield, which subsequently reaches the water matrices through surface water runoff and thereby causing algal bloom (Broeren et al., 2017; Rosenboom et al., 2022). Moreover, starch production elevates agricultural land usage to around 0.3–1.3 m2 yr per kg, whereas petrochemical plastics require negligible to zero land usage as no raw materials are required to be farmed for the manufacture of petrochemical plastics (Broeren et al., 2017). Thus, starch blends and reclaimed starch are utilized as an alternative to

19.6 Economic Assessment of Bioplastics

manufacture starch-based bioplastics to reduce the impacts on agricultural land usage (Broeren et al., 2017). Moreover, bioplastics can also be generated from various raw materials, such as sugar cane, corn, and rice, and also from biowastes, such as potato peels and cooking oil waste (Ali et al., 2023). Through observations from various studies, the utilization of appropriate impact categories, such as GHG emissions, agricultural land usage, eutrophication potential, and human toxicity potential, has shown significant importance for analyzing the environmental impacts caused during the manufacturing, usage, and disposal of biodegradable bioplastics. Also, the higher acidification potential indicates a higher probability of emitting compounds, such as sulfur and nitrogenous compounds from bioplastics that can acidify water and soil, compared to conventional plastics thus demanding deeper research for mitigating acidification impacts of bioplastics (Rosenboom et al., 2022). Even though various impact categories of certain bioplastics have been determined by the researchers (Table 19.1), deeper studies are required to identify suitable materials, which are equally economical, sustainable, and durable.

19.6 Economic Assessment of Bioplastics The term bioplastic is often misunderstood and synonymously used for biodegradable plastic, whereas not all bioplastics are biodegradable. By definition, bioplastics are either biobased or biodegradable or have both these properties (Goel et al., 2021). Biodegradability and other essential features, such as low greenhouse gas emission, low waste generation, and low carbon footprint, make bioplastics a viable substitute for conventional petroleum-based plastics (Arikan & Ozsoy, 2015). As a result, in recent decades, the demand for bioplastic as an alternative to petroleum-based plastic has increased significantly and will increase further in the near future. As of 2023, bioplastics contribute to approximately 0.5% of the 400 million tonnes of plastic produced per annum globally. In addition, as per the European Bioplastics Association’s estimate, the global bioplastic production capacity will exponentially increase from approximately 2.18 million tonnes in 2023 to around 7.43 million tonnes in 2028 (European Bioplastics, 2023). Further to meet these predictions, it is essential to reduce the manufacturing cost of bioplastics along with other drawbacks, such as poor mechanical properties and utilization of food crop feedstocks. Currently, bioplastics are expensive to produce and usually cost two to three times more than petroleum-based plastics due to the utilization of expensive raw materials and downstream recovery processes, the price competitiveness of crude oil, and low-scale production (Nikola, 2022; Thomas et al., 2023). Among all these contributing factors, the cost of bioplastic production majorly depends on the type of feedstocks employed and the technological advancement of bioplastic production (Wellenreuther et al., 2022). In addition, based on the type of feedstock, it may include various associated costs, such as the cost of agricultural land, irrigation, agrochemicals, machinery, and various other secondary resources. The prices of commonly used bioplastics, such as PLA, polybutylene succinate, cellulose acetate, starch-based polymers, bio-based PET, and bio-PE, generally range from US$1.31 to US$5.46/kg (values converted from Euro to USD, considering €1 = US$0.92) (Ali et al., 2023). In an investigation, Wellenreuther et al. (2022) explained

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19 Biodegradable Bioplastics

the different costs associated with biopolymer PLA manufactured from first-generation crops and second-generation biomass. As per this investigation, the total manufacturing cost of PLA produced from corn grain was US$1.18/kg, which includes the material cost of US$0.66/kg, energy cost of US$0.08/kg, and additional labor, depreciation, maintenance, and repair cost of US$0.44/kg. Moreover, the total manufacturing cost of PLA produced from second-generation biomass, such as corn stover, was US$1.38/kg, including the material cost of US$0.61/kg, the energy cost of US$0.15/kg, and additional labor, depreciation, maintenance, and repair cost of US$0.62/kg. Similarly, as of 2019, the global market price of poly-3-hydroybutyrate bioplastic was US$11,424/tonne, which is approx. 11 times higher compared to petroleum-based PET, which generally costs around US$1,000/tonne. Therefore, to overcome the problem of costly feedstocks, alternatives like woody biomass, crop residues, food waste, sludge, algae, etc., are currently being explored for bioplastic production (Kuddus, 2021; Nanda et al., 2022). Whereas, in terms of energy consumption, bioplastic production requires less energy compared to conventional petroleum-based plastics. Conventional petroleum-based plastic, such as low-density polyethylene, high-density polyethylene, and PP, consumes 81.8 MJ/kg, 73.7 MJ/kg, and 85.9 MJ/kg of plastic produced, respectively. Meanwhile, bioplastics, such as polylactide (PLA), TPS, and PHB, consume 54.1 MJ/kg, 25.4 MJ/kg, and 44.7 MJ/kg of plastic produced, respectively, which is comparatively lower compared to the energy required for producing conventional plastics (Costa et al., 2023). Currently, bioplastics have high demand due to their increasing application in various sectors, such as food packaging, agriculture, horticulture, consumer goods, automotive products, and toys (Costa et al., 2023; Rosenboom et al., 2022). However, as of 2023, bioplastics contributed only 0.5% of the total plastics produced in that year (European Bioplastics, 2023). In this veneration, the major factor that limits the market growth of bioplastics is the high production cost, the complexity of the production process, poor mechanical properties, and so forth (Wellenreuther et al., 2022). Different studies have suggested that the utilization of cheaper and renewable feedstocks can reduce the cost of production to around 50%, which will partially address the problem of costly feedstock employed for bioplastic production. Therefore, for a paradigm shift, bioplastics must compete with conventional fossil-based plastics in terms of reducing manufacturing costs increasing consumer awareness, large-scale production, and effective end-of-life management and other factors to render them as a viable alternative to traditional petrochemical-based plastics (Nanda et al., 2022; Thomas et al., 2023).

19.7

Comparison of Bioplastic with Polymer-Based Plastic

Conventional plastics, such as PE, PP, polyvinyl chloride, PET, polystyrene, polycarbonate, and polyurethane, are the derivatives of hydrocarbons, which originate from nonrenewable fossil fuels. Owing to their diverse applications, conventional plastics have become an integral part of human day-to-day life. However, the immense utilization of these plastics is becoming a threat to the environment, posing numerous adverse effects, such as global warming, abiotic resource depletion, and soil fertility reduction.

19.8 Conclusion and Future Perspectives

For instance, fossil fuel-based plastics are primarily nonbiodegradable, with quite low biodegradability, thus finally ending up in the different components of the environment. Moreover, during the production of these nondegradable plastics, toxins, such as bisphenol A and numerous other hormone-disrupting compounds, are also generated as by-products, which significantly affect human health and ecosystems. Furthermore, these plastics require extensively higher energy for their production, resulting in higher greenhouse gas emissions, rendering their production process to be unsustainable. Nonetheless, researchers have directed efforts to biodegrade single-use plastics in soil and compost environments to tackle the rising plastic pollution. However, the disposal of these plastics have adverse effect on the ecosystem, as during this process, nearly 400 million tons of CO2 are released into the environment (Idris et al., 2023). Furthermore, a large fraction of the total plastic produced finally arrives in marine water bodies leading to toxic effects on the marine environment. Moreover, these plastics also enter the food chain through seafood, adversely affecting marine and human life. To overcome these concerns, researchers are devoted to exploring viable alternatives to conventional plastics that can be recycled biologically, replicating the existing recyclable materials, thus countering the rising environmental and economical challenges. In this context, bioplastics based on cellulose, starch, lipid, chitin, and protein and PLA, polyamide, polyhydroxyalkanoate, polyhydroxy urethane, and polyhydroxy butyrate, sourced from agricultural waste, food waste, biowaste, paper waste, feather quills, etc., are more sustainable and eco-friendlier alternative. These bioplastics are predominantly biodegradable and comparatively less toxic compared to conventional plastics. Even though bioplastics require considerably low energy for their production, they incur nearly two to three times more capital during production compared to conventional plastics (Sanyang et al., 2016). Furthermore, the requirement of land, large water consumption, and intensive farming make the production route of bioplastics quite expensive. Moreover, the natural properties or composition of bioplastics are inconsistent in comparison to conventional plastics, which reduces their reliability. Furthermore, the global market of biodegradable plastics is still comparatively low and limited to a small scale only (Idris et al., 2023). Therefore, more research is required to understand the challenges associated with bioplastics in order to expedite the commercialization of these materials. Furthermore, techno-economic and life cycle assessments can be carried out to understand the overall economic aspect as well as the environmental impact of the bioplastics. Thus, from the above discussion, it can be concluded that bioplastics have great potential to replace conventionally used plastics and can emerge as probable alternative. However, more dedicated investigations are required to make bioplastic commercially available in order to reduce the potential risks associated with various types of plastics and their derivatives.

19.8 Conclusion and Future Perspectives According to the context of this chapter, a clear and strong paradigm shift to biodegradable bioplastics is evident, due to the detrimental MP pollution prevailing in the different sectors of the environment. Moreover, the comparison of bioplastics with polymer-based plastics in

571

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19 Biodegradable Bioplastics

terms of economic feasibility, environmental impacts through LCA, sustainability, etc., clearly indicates the potential of bioplastics as an emerging alternative that preserves a balance between sustainability and economic viability. However, comprehensive studies on bioplastics are required to overcome the challenges of increased agricultural land usage to produce first-generation crops as feedstock for the manufacture of bioplastics. Moreover, adapting various mechanical and chemical recycling processes, such as solvolysis and thermolysis, can aid in upcycling the bioplastics into higher-quality materials, which subsequently aids in rendering circular economy (Rosenboom et al., 2022). Also, clear implementation of guidelines and policies on bioplastics will create a positive pathway toward a sustainable future, by halting and mitigating the ill-effects caused by conventional plastic products.

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20 Global Strategies/Policies and Citizen Science for Microplastic Management Jin-Min Li1, Ming-Fang Yu1, Chih-Ming Kao1, Rao Y. Surampalli2, and Tian C. Zhang3 1

Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan Global Institute for Energy, Environment and Sustainability, Lenexa, KS, USA 3 Civil & Environmental Engineering Department, College of Engineering, University of Nebraska-Lincoln, Omaha, NE, USA 2

20.1 Guidelines for Pollutant Control at Source The development of guidelines for controlling microplastic (MP) pollution sources is essential due to the severe environmental and ecological impacts caused by MPs, necessitating measures to control their generation and release. The purpose of these guidelines is to provide industries, governments, and the public with guidance on how to reduce MP pollution, thereby mitigating its detrimental effects on the environment and biodiversity. To control MP pollution, it is imperative to first understand the sources and pathways of MPs. Subsequently, various methods can be employed to control the generation and release of MPs, such as regulating industrial emissions, improving wastewater treatment technologies, promoting eco-friendly product design, and encouraging recycling and reuse. Guidelines for controlling MP pollution typically include aspects such as providing definitions and classifications of MPs, assessing the risks and impacts of MPs, guiding relevant industries to take measures to reduce the generation and release of MPs, and promoting scientific research and monitoring to understand the distribution and impacts of MPs. However, developing and implementing guidelines for controlling MP pollution sources may encounter challenges. Firstly, MP sources are diverse, including those from industrial production, domestic wastewater, plastic debris, etc., necessitating a variety of measures for control. Secondly, involving multiple stakeholders requires coordination of interests among various parties, including governments, businesses, and the public. Additionally, regulation and enforcement pose challenges, necessitating the establishment of effective regulatory mechanisms and enforcement measures to ensure the guidelines’ effective implementation. Lastly, there are many unknown areas in MP research, requiring further scientific research and technological support. MPs are plastic particles with a diameter or length less than 5 mm, as defined by the National Oceanic and Atmospheric Administration (NOAA). The size of the particles determines the initial generation of MPs and also influences the primary and secondary types.

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High concentrations of primary and secondary MPs are found in marine environments and may adversely affect marine organisms and ecological processes. Primary MPs can be found in microbeads, cosmetic chemicals, clothing fibers, sandblasting materials, road paints, tire abrasion, and shipbreaking items. They are generally less than 5 mm. Larger plastic objects weather physically, chemically, and biologically to produce secondary MPs (Akdemir &Gedik, 2023; Surana et al., 2024). Primary and secondary MPs are subjected to processing at wastewater treatment plants (WWTPs). Nevertheless, should MPs remain inadequately eliminated in the WWTPs, they could be released into the natural surroundings, encompassing rivers, oceans, and diverse ecosystems. Numerous studies have reported significant concentrations of MPs in WWTPs’ effluent (Acarer, 2024). For instance, a study of WWTPs’ effluent in Turkey found daily MP concentrations ranging from 0.22 to 1.50 million MPs per liter. Multiple studies have evaluated the capability of WWTPs technologies in removing plastics and found that conventional WWTPs can remove MPs from influent within a range of 90–98%. However, due to continuous discharge of large volumes of wastewater, sewage remains a primary source of MPs entering aquatic environments. Membrane bioreactors, a commonly used advanced technology, demonstrate a higher efficiency in removal of MPs compared to traditional activated sludge processes, achieving up to 99.4%. Additionally, Biological Activated Filters exhibit high efficiency in removal of MPs. Electrocoagulation emerges as another effective method for removal of MPs from wastewater, with observed removal efficiencies exceeding 90% under different conditions, and this technology has been tested at both laboratory and industrial scales. Certain techniques (Figure 20.1) hold promise for application in other freshwater systems (Mahmud et al., 2022; Shi et al., 2022; Tang et al., 2021). The transferability and repeatability of these

Microplastic removal techniques

Physical

Filtration

Chemical

Adsorption

Coagulation

Biological

Electrocoagulation

Bioremediation

Permeate tank Magnetic nanomaterials

MPs

OH– Membrane step

An

ode

Al3+

Ca

tho

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Water MPs Figure 20.1

• Nano-Fe3O4 • Magnetic carbon nan-otubes etc.

MPs

Polyacrylamide (Fe and Al salts)

MPs

Removal Approaches of Microplastics

Al3+

MPs

OH–

H2O

CO2 CH4

20.1 Guidelines for Pollutant Control at Source

techniques have been demonstrated, holding promise for their application in WWTPs to reduce the discharge of MPs into natural water bodies. MPs are ubiquitous in WWTPs. During primary treatment, solid waste skimming and sludge settling are commonly used to remove MPs. However, the efficiency of these methods is limited, and a significant portion of MPs can escape removal (Picó & Barceló, 2019). Once discharged into the environment, MPs can persist for hundreds of years, posing a serious threat to ecological and human health. Biodegradable plastics have been proposed as a potential solution to the MPs problem. Researchers have proposed that the use of bio-based and/or biodegradable polymers is an important strategy for addressing the current plastic pollution issue. With increasing concern over the negative environmental impacts of conventional plastics, bioplastics have garnered widespread attention and research as a sustainable and environment-friendly alternative. Bioplastics are primarily derived from renewable materials such as starch, cellulose, lignin, and bioethanol. In comparison to traditional petrochemical plastics, the production process of bioplastics can reduce dependence on finite petroleum resources, thereby mitigating negative environmental impacts. Currently, bioplastics account for approximately 0.5% of the global annual plastic production, and this proportion is expected to increase to around 2.62 million tons by 2023 (Qiu et al., 2024). Bioplastics can be categorized into different types, including bio-based or partially biobased nonbiodegradable plastics, plastics that are both bio-based and biodegradable, and plastics derived from fossil resources that are biodegradable. While these bioplastics offer certain environmental advantages, they also present some challenges and limitations. For instance, some bioplastics, while biodegradable, may require specific conditions and microorganisms in the actual environment for degradation, thereby potentially limiting their biodegradation rate. Additionally, the biodegradation process of some bioplastics may release harmful substances, posing potential environmental impacts. In addition to bioplastics, bioengineering-based solutions represent a promising research direction. By exploring new biodegradation pathways or isolating enzymes to accelerate the biodegradation of plastics, it is possible to further enhance the biodegradability of plastics. Some specialized bacteria have been found to decompose specific types of plastics such as polyethylene terephthalate (PET) and polyethylene (PE), but these bioengineering technologies are still in their early stages of practical application and require further research and development. In conclusion, bioplastics and bioengineering-based solutions offer a hopeful pathway for addressing the plastic pollution issue. Through ongoing research and innovation, we have the potential to develop more sustainable and environmentfriendly plastic materials, thus achieving more effective protection of the environment (Picó & Barceló, 2019). Although compostable materials are often touted as an environment-friendly alternative, a study by the Oregon Department of Environmental Quality (DEQ) in the United States suggests that using composability as a metric for assessing the environmental benefits of packaging and foodware is a poor indicator (Robbins, 2020). The study evaluated compostable materials across a range of environmental impact categories, including raw material use, production processes, transportation systems, and end-of-life management. The findings demonstrated that compostable materials can have an even greater negative impact on the environment during manufacture and composting than noncompostable materials

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when they are recycled, disposed of in a landfill, or burned. For example, the production of compostable plastics requires the use of significant amounts of fossil fuels and emits greenhouse gases. Additionally, compostable materials can generate methane, a potent greenhouse gas, during the composting process. The use of biodegradable plastic items has been strongly opposed by the United Nations (UN) and the European Union (EU), who point out that this does not solve the issue of plastic pollution in the ocean (Robbins, 2020). The Life Cycle Assessment (LCA) serves as a tool for evaluating the environmental impacts of MPs, allowing for the assessment of product or process environmental impacts from cradle to grave, cradle to cradle, or cradle to gate, facilitating the development of the most sustainable environmental production routes or processes. LCA is essential to address the toxicity, potential hazards, and uncertainties of MP pollution on water and the environment. LCA tools assess the potential impacts of MPs, including identifying and resolving pollution issues throughout the plastic life cycle and their global distribution. Impact assessment categories encompass ecological toxicity, respiratory organic compounds, carcinogenicity, and land use. LCA tools such as SimaPro employ various impact assessment methods, utilizing different evaluation categories and calculation approaches as per the scenario. Most LCA studies cover impacts from cradle to grave and cradle to gate, including impacts from raw materials to product end-of-life and leaving the manufacturer’s gate (Yusuf et al., 2022).

20.2

Enforcement of Legislative Measures

The effective implementation of legislative measures is crucial for addressing the issue of MP pollution. Firstly, governments should establish relevant laws and regulations specifically targeting MP pollution, covering various aspects such as production, use, handling, and discharge of MPs, and ensuring clear standards and obligations for all parties involved. Secondly, governments should establish specialized regulatory agencies or departments with expertise and enforcement powers to oversee and enforce the relevant laws and regulations, and enhance monitoring and enforcement efforts against violations, ensuring the effective implementation of the laws. Additionally, governments should provide sufficient technical support and resource allocation to regulatory agencies, funding research and development of new monitoring technologies, governance techniques, and innovative solutions. Public participation and transparency are also crucial, and governments should actively promote public involvement in the management and regulatory processes of MPs as well as ensure transparency of relevant information. Furthermore, as MP pollution is a global issue, governments should engage in international cooperation, establish common standards and regulations, and implement continuous monitoring and evaluation mechanisms to regularly assess the status and effects of MP pollution and promptly adjust and improve relevant management measures and policies. In conclusion, addressing MP pollution requires collaborative efforts from governments, regulatory agencies, businesses, and the public to protect the environment and public health.

20.2 Enforcement of Legislative Measures

Numerous nations have implemented a range of source management strategies in an effort to decrease the quantity of MPs that are released into the environment (Diana et al., 2022; Li, 2022; Yusuf et al., 2022). These policies can be broadly categorized into four types: 1) Affirmative regulatory measures. Affirmative regulatory measures encourage the development and adoption of technologies and practices that reduce MP emissions. Examples include: 1) Requiring manufacturers to develop new products that are less likely to release MPs; 2) Providing financial incentives for businesses to develop new technologies that reduce MP emissions; and 3) Implementing postleakage capture systems to collect MPs that have already entered the environment. 2) Prohibitive regulatory measures. Prohibitive regulatory measures restrict or ban the use of certain products or materials that are known to release MPs. Examples include: 1) Banning the use of single-use plastics; 2) Banning the use of microbeads in personal care products (PCPs); and 3) Restricting the use of plastic bags. 3) Economic measures. Economic measures use economic incentives to discourage the use of MPs. Examples include: 1) Imposing a tax on plastic bags; 2) Offering a cash reward for the return of used plastic bottles; and 3) Providing subsidies for businesses that develop new technologies that reduce MP emissions. 4) Information measures. Information measures raise awareness about MP pollution and provide information about how to reduce MP emissions. Examples include: 1) Public education campaigns about MP pollution; 2) Providing information about how to reduce MP emissions on government websites; and 3) Working with businesses to develop and implement MP reduction plans. The majority of MPs are synthetic or partially synthetic microscale polymers, which are mainly made up of microbeads added to the products as either foundation or exfoliants (e.g., toothpaste and cosmetics). As a result, legislative efforts around the world are currently concentrated on measures such as outlawing the use of microbeads in relevant products and outlawing their sale, import, and export, among other things. For instance, the United States enacted “The Microbead-Free Waters Act” of 2015, which prohibited the production of rinse-off cosmetics containing microbeads effective from July 1, 2017. The final deadline for discontinuing the production of products described in the ban for over-the-counter drugs that are also rinse-off cosmetics was July 1, 2018. The deadline was extended to July 1, 2019, to cease introducing or delivering such products into interstate commerce (Li, 2022). The United States Environmental Protection Agency (USEPA) played a pivotal role in mitigating microbead pollution by establishing a process to identify and assess waterway

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contamination sources. This action, coupled with the enactment of the Microbead-Free Waters Act of 2015, spurred a significant shift within the manufacturing industry. Companies have increasingly embraced natural alternatives such as salt, sugar, and powdered fruit shells, which has resulted in a significant decrease in the use of microbeads. On a broader front, the EU has emerged as a leader in the fight against plastic pollution. In 2019, the EU launched the Single-Use Plastics Directive, a landmark initiative designed to curb the environmental impact of disposable items. This directive expressly forbids the use and sale of some single-use plastics, such as cotton buds, straws, balloon sticks, and cutlery. Furthermore, it mandates extended producer responsibility schemes, incentivizing manufacturers to prioritize environmental considerations throughout the product life cycle, from design to pricing. Producers are incentivized to create more sustainable products by taking on the costs of trash management and cleaning, which ultimately lowers the overall environmental impact of single-use plastics. The European Environmental Council started initial talks on a worldwide plastic convention in December 2022. The goal of the treaty is to provide a thorough and legally binding framework to deal with the problem of plastic pollution. By 2024, the pact should be completely in effect, supporting coordinated international efforts to reduce plastic waste and advance sustainable practices (Martins & Marto, 2023; Zhou & Luo, 2024). It is noteworthy that the fluidity of the oceans not only enables MP pollution to transcend national borders but also renders the prevention and control of transboundary pollution a challenging issue that necessitates global cooperation and collective governance. However, differences in economic development levels, technological capabilities, policy frameworks among countries, as well as the varying levels of engagement and willingness of the public, industries, and governments, can impede the progress of international cooperation. Currently, marine MP pollution has become a global issue, and measures taken by individual countries are insufficient to effectively address this problem, posing a significant challenge to the prevention and control of marine MP pollution. In recent years, various countries and regions have introduced a range of legislative and policy initiatives aimed at addressing marine MP pollution. For instance, the European industrial association has proactively implemented measures to curb the production and utilization of MP-containing products, resulting in a notable decline in MP levels. Similarly, some countries have regulated the import, production, and sale of products containing MPs, which has had a positive impact on reducing MP emissions. Additionally, some countries have strengthened the control and management of MPs by amending existing laws, designating MPs as toxic substances, or guiding industry development through policy documents (Li, 2022). In summary, legislative and policy measures addressing marine MP pollution can be categorized into three modes: adding clauses, designating MPs as toxic substances, and guiding through policy. The implementation of these measures is crucial for reducing marine MP pollution and protecting the marine ecological environment. However, to truly solve this global issue, concerted efforts from all countries are still required to enhance cooperation, establish more comprehensive international mechanisms, and collectively safeguard our marine environment.

20.3 Existing Regulations and Acts in Global Scenarios

20.3 Existing Regulations and Acts in Global Scenarios Currently, global regulations and laws concerning MPs primarily cover three aspects. Firstly, many countries and regions have established prohibitions or restrictions on the use of MPs, particularly in products such as detergents, cosmetics, and plastic microbeads, prohibiting or limiting their production, sale, and use. For example, the EU, Canada, Australia, and New Zealand have enacted relevant regulations. Secondly, some regions control the emission and pollution of MPs through regulations, such as emission standards for WWTPs and oversight of plastic production. For instance, the USEPA has issued a series of regulations to regulate the emission of MPs. Lastly, some countries and regions regulate the monitoring and research of MPs through laws to understand their impact on the environment and human health. For example, the EU requires member states to monitor and research MPs. The formulation of these regulations and laws aims to protect the environment and human health, providing an important legal basis for addressing the issue of MP pollution. The emergence of MP pollution, a novel consequence of scientific and technological advancements, presents a challenge to existing legal frameworks at national and global levels (Lusher & Primpke, 2023). Identifying effective legal and management tools to control MP contamination has become a global priority. Currently, most national legislation focuses on specific measures such as microbead bans in relevant products, including restrictions on their sale, import, and export. For example, the United States enacted the Microbead-Free Waters Act of 2015, prohibiting the manufacture of rinse-off cosmetics containing microbeads starting in July 2017. Similarly, Canada (2016) and New Zealand (2018) classified plastic beads as harmful chemicals and banned their inclusion in PCPs under their respective environmental protection acts (Li, 2022; Lin et al., 2023). France (2017) implemented a decree prohibiting the marketing of exfoliating cosmetics containing solid plastic particles (Li, 2022). Additionally, the European Association of Industry carried out voluntary initiatives from 2012 to 2015 to lessen the amount of synthetic solid particles used in product washing, which led to an 82% decrease in microbeads in this category (Anagnosti et al., 2021). Thailand (2019) followed suit with a similar ban on microbeads in cosmetics (Kumar et al., 2021). Ireland became the first EU member state to ban microbeads in all rinse-off products in 2020 (Anagnosti et al., 2021). These examples highlight a focus on microbeads in exfoliating products, with limited attention to broader MP sources in cosmetics and other items. Secondary MPs, originating from diverse sources such as land-based waste, maritime activities, and various industrial processes, pose a more significant contamination threat (Anagnosti et al., 2021; Miller et al., 2021). While secondary sources are believed to contribute the majority of MPs currently found in the environment, there are currently no comprehensive national or global regulations to address them. The ubiquitous nature of these sources presents a significant challenge in developing effective legislation specifically targeting secondary MP contamination. Banning the use of single-use plastic products is another preventive measure reported worldwide. In essence, banning single-use plastic items can greatly lower the percentage of MPs that readily make their way through garbage collection systems because of their tiny size and/or ineffective municipal management. More than 60 nations have implemented

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policies (such as high taxes or bans) to reduce the use of single-use plastic and/or plastic bags. For instance, the Australian Capital Territory banned the use of single-use plastic bags in 2011, resulting in a reduction of approximately 2,600 tons in the consumption of conventional PE bags by 2018. Scotland’s plastic bag ban policy also prevented around 6.5 billion plastic bags from entering the waste stream. Federal governments in Canada, Australia, Austria, Luxembourg, Belgium, the Netherlands, Sweden, and Germany have comprehensively prohibited the use of microbeads in PCPs (Chen et al., 2021; Macintosh et al., 2020). It’s noteworthy to see that large cities are now aggressively enforcing these prohibitions; this could be because national bans take longer to take effect (Hettiarachchi & Meegoda, 2023). Recently, EU proposed a continent-wide plastic strategy as part of transitioning to a circular economy. Based on this strategy, by 2030, the consumption of single-use plastics will significantly decrease, and all plastic packaging materials will be recyclable in the EU market (Chen et al., 2021).

20.3.1

Microplastics and the UN Sustainable Development Goals

The United Nations Environment Assembly (UNEA) is one of the highest-level environmental decision-making bodies within the UN. Since 2014, it has adopted four resolutions on marine litter, with a particular emphasis on the issue of MP pollution. These resolutions acknowledge the threat of MP pollution to the environment and ecosystems, emphasizing the urgent need for global solutions. However, as the issue of MP pollution has become increasingly severe, UNEA recognized that existing global governance frameworks were inadequate in effectively addressing this problem. Therefore, an expert group was established at the third assembly in 2017 to seek solutions. A major step in the UNEA’s history with regard to MP pollution was made when members unanimously decided to draft a legally binding pact to battle plastic pollution at the organization’s fifth session in 2022. This resolution signifies that the international community has recognized the urgency of the MP pollution issue and is willing to take substantive action to address it. Additionally, UNEA convened an intergovernmental negotiating committee, aiming to complete this work by the end of 2024 to further promote global cooperation on the issue of MP pollution. During the fourth congress in 2019, UNEA took another important step by establishing the UN Alliance for Sustainable Fashion. This alliance aims to drive government-level action, promote the transition of the textile industry toward sustainability while minimizing its environmental impact. The prevalence of synthetic fibers in textiles is a major concern for MP pollution. Roughly 60% of clothing materials are composed of nylon, acrylic, and polyester, contributing an estimated 9% of the annual MP load entering oceans (Hettiarachchi & Meegoda, 2023; Thacharodi et al., 2024). While the UNEA actively promotes action, the effectiveness of governmental implementation remains unclear. EU has taken a more proactive approach to addressing MP pollution. In 2020, the European Commission, the EU’s executive branch, adopted a comprehensive Circular Economy Action Plan that includes measures to reduce plastic pollution. The strategy calls for limitations on purposefully added MPs, such as microbeads, in addition to the creation of standards, certification, labeling, and regulatory procedures to stop MPs from accidentally leaking into the environment. The EU has also set a target to reduce MP emissions into the environment by 30% and proposed measures to limit plastic pollution from car tire wear. In addition, the EU announced the Circular

20.3 Existing Regulations and Acts in Global Scenarios

and Sustainable Textiles Strategy in 2022, which specifically addresses MP pollution caused by synthetic fibers. These actions demonstrate the EU’s leadership in tackling the MP pollution challenge (Hettiarachchi & Meegoda, 2023). Governments and businesses have embraced the Sustainable Development Goals (SDGs) since its introduction in 2015 in an effort to enhance their sustainability performance (Thacharodi et al., 2024). There are 17 objectives, 169 targets, and 247 distinct indicators in the SDGs. Even though (micro)plastic contamination is ubiquitous worldwide, Goal 14 only has one indicator that is especially focused on decreasing the consequences of (micro)plastics. For governments and organizations, ensuring accurate reporting and tracking of all 247 SDG indicators presents special challenges. The widespread occurrence of (micro)plastic pollution could worsen these issues if it is not adequately tracked across all metrics. Thus, improper handling of (micro)plastics endangers the world’s capacity. The number of national and international commitments to minimize (micro)plastic pollution is increasing in tandem with the growth of global plastic production. National governments are increasingly enforcing bans or imposing taxes on single-use plastic products (Figure 20.2) (Adam et al., 2020; Bezerra et al., 2021; Clayton et al., 2021). At the international level, the UN has made commitments to reduce plastic leakage into the environment. For instance, these pledges encompass tackling pollution from single-use plastic products; the UNEA’s resolutions on marine litter and MPs, and the UN SDGs aimed at promoting sustainable practices in plastic production, utilization, and disposal (Da Costa et al., 2020; United Nations, 2024). As a recognized worldwide concern, marine (micro) plastics are included in the UN SDGs under Goal 14: Conserve and sustainably use the oceans, seas and marine resources for sustainable development. Specifically, target 14.1 aims to prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution, by 2025 (Nakhle et al., 2024). This will be measured by indicator 14.1.1: Index of coastal eutrophication and floating plastic debris density. MPs are not particularly mentioned in Goal 14, the sole SDG that deals with plastics (i.e., indicator 14.1.1b: plastic debris density). Although (micro)plastic pollution has been widely recognized as a planetary threat affecting nearly every marine and freshwater ecosystem globally, there is currently no specific indicator for MPs in the SDGs (Figure 20.3). This lack of a specific indicator for MPs makes it difficult to track progress in reducing MP pollution and to identify effective mitigation strategies. There is a need for Figure 20.2 Microplastic Bans Around a more comprehensive approach to addressing the World

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End poverty in all its forms everywhere

Reduce inequality within and among countries

End hunger, achieve food security and improved nutrition and promote sustainable agriculture

Make cities and human settlements inclusive, safe, resilient and sustainable

Ensure healthy lives and promote well-being for all at all ages

Ensure sustainable consumption and production patterns

Ensure inclusive and equitable quality education and promote lifelong learning opportunities for all

Take urgent action combat climate change and its impacts

Achieve gender equality and empower all women and girls

Conserve and sustainably use the oceans, seas and marine resources for sustainable development

Ensure availability and sustainable management of water and sanitation for all

Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss

Ensure access to affordable, reliable, sustainable and modern energy for all

Promote peaceful and inclusive societies for sustainable development, provide access to justice for all and build effective, accountable and inclusive institutions at all levels

Promote sustained, inclusive and sustainable economic growth, full and productive employment and decent work for all

Strengthen the means of implementation and revitalize the Global Partnership for Sustainable Development

Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation Figure 20.3 17 Sustainable Development Goals (Source: United Nations (2024). Reprinted with permission with United Nations)

20.4 Public Perception and Participation

(micro)plastic pollution, including the development of a specific indicator for MPs in the SDGs (Borrelle et al., 2020; Krause et al., 2021). Currently, there is no standardized approach or internationally agreed protocol for measuring indicator 14.1.1b: plastic debris density. Therefore, citizen scientists’ visual observations are the primary method used to quantify floating plastic marine trash (>2.5 cm) (Ambrose et al., 2019). Nonetheless, recent research has suggested that citizen scientists could contribute to the quantification of floating debris by taking part in marine debris clean-ups led by groups such as Litter Intelligence, International Coastal Cleanup (ICC), and Marine Debris National Oceanic and Atmospheric Administration (NOAA) (Fraisl et al., 2020; Fritz et al., 2019). UN Environment Programme (UNEP), tasked with overseeing this indicator, is presently devising a methodology leveraging citizen science data as the principal source for assessing the presence of marine plastics along coastlines and beaches (Fraisl et al., 2020). While using citizen scientists to help measure and track changes is fascinating, this goal does not yet acknowledge the problem posed by MP pollution. While the 17 SDGs tackle the most pressing threats to our planet, only one indicator within Goal 14 is specifically dedicated to mitigating the impacts of plastics. In contrast, the remaining SDGs lack explicit targets or indicators addressing the reduction of (micro) plastics, assuming baseline data exists. Given the widespread impact of (micro)plastic pollution on the environment, society, and economy, governments and organizations working to build strong reporting and monitoring procedures for the other SDGs face substantial problems as a result of this omission. It has been determined by this critical review that (micro)plastic pollution affects at least 12 UN SDGs, either directly or indirectly. Therefore, it is recommended that a minimum of 12 UN SDGs undergo revision to incorporate baseline data collection, enabling future monitoring and reporting to effectively combat the cross-border threat of (micro)plastics and safeguard the successful realization of broader UN SDG objectives (Hettiarachchi & Meegoda, 2023; Walker, 2021).

20.4 Public Perception and Participation According to the data collected by Google Trends, the search heat of people on Google about MPs has been increasing from 2004 to 2024, which proves that people are paying more and more attention to MPs. Among them, the most popular keywords are “plastic,” “MPs,” “pollution,” “MPs pollution,” “MPs water,” etc. (Figure 20.4). Recent data indicate that unless marine litter is addressed, plastic in the oceans will triple within a decade, underscoring its critical nature. Given that human behavior is recognized as the sole source of marine litter, this implies that changing attitudes and behaviors are key to addressing the garbage problem in the natural environment (Henderson & Green, 2020). Behavioral change and multilevel governance are paramount in preventing MP leakage into the environment, requiring involvement from ordinary citizens, governments, industries, nongovernmental organizations, academia, fishermen, and local communities. Currently, MPs and marine litter dominate the scientific literature, with increasing concern over these issues to the extent that there are fears that the “plastic” as a hot topic may overshadow other less newsworthy but more urgent issues.

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Figure 20.4 The Popularity of Microplastics in Google Searches (Source: Data used from https:// trends.google.com). Y-axis numbers represent the popularity of keywords in Google searches: 100 means the popularity of the term reached its peak at that point in time, and 50 means the popularity of the term is half of the peak. The chart below shows the top 10 most popular searches for microplastics

To gain a deeper understanding of public perceptions of marine litter, several large-scale quantitative surveys have been conducted. For example, a survey of 3,748 respondents from 16 European countries found that the majority of people reported seeing marine litter on most or all visits to the coast, and that they perceived this situation to be worsening. Environmental groups expressed higher levels of concern about marine litter than the average, while manufacturing and retail stakeholders expressed lower levels of concern than other groups (Henderson & Green, 2020). This article also presents other concluding viewpoints: 1) There exists a certain degree of inadequacy and misunderstanding in the public’s awareness of MPs, especially regarding the sources and impacts of MP particles. 2) The media plays a significant role in shaping public awareness of plastic pollution issues, particularly among environmentally conscious individuals. 3) Sociocultural factors have a significant influence on individuals’ attitudes toward reducing single-use plastic, necessitating consideration of personal values and behavioral habits. 4) Public awareness of MP issues is a complex and often ambiguous process that requires enhancing public awareness and understanding of plastic pollution issues through education, media coverage, and policy guidance. Another study conducted a nationally representative survey of 1,960 American adults in 2021 to explore public knowledge, perceptions, and concerns regarding marine threats, particularly plastic and MP pollution (Baechler et al., 2024). Based on this study, the authors arrived at the following conclusions:

20.4 Public Perception and Participation

1) Both American adults and members of marine conservation associations exhibit a high level of awareness and concern regarding marine plastic and MP pollution issues. 2) The American public widely supports measures to reduce single-use plastic products, believing that industries must take action to address this issue. 3) General awareness of marine health among American adults reflects a complex yet generally positive attitude, especially among adults residing near the coast. 4) American individuals are least likely to formally express their opinions to public officials or companies regarding personal efforts to reduce plastic usage. 5) Providing targeted information regularly can help enhance public awareness and perceptions of plastic pollution issues, thereby safeguarding the collective future from the impacts of plastic pollution. These conclusions underscore the concern over plastic pollution issues, support for solutions, and emphasize the importance of education and information dissemination in addressing plastic pollution problems. A study conducted in Malaysia utilized various social media platforms such as WhatsApp, Telegram, Facebook, Twitter, and Instagram to distribute survey questionnaires, aiming to broaden the scope of respondents and enhance diversity. Through snowball sampling techniques and social media platforms, the research team successfully collected 750 survey responses (Praveena, 2024). The application of this method enhanced the credibility and inclusivity of the study results. The report indicated that the majority of respondents showed willingness to reduce MP emissions, with some expressing strong commitments. Specifically, a significant proportion of respondents were willing to switch brands or reduce the use of PCPs containing MPs. However, a small fraction of respondents indicated their intention to continue using products containing MPs, while some were uncertain about their actions. Survey results revealed that people are willing to take various actions to reduce MP pollution, with the most common response being reducing the use of plastic products, reflecting a growing awareness of minimizing plastic consumption. Moreover, the interest in using biodegradable plastics also signifies concern for alternative materials, although the effectiveness and environmental impacts of different materials need to be considered. Furthermore, many respondents expressed a desire to acquire more knowledge before engaging in efforts to reduce MPs, highlighting the importance of education. The report also noted that while a considerable proportion of respondents have an above-average level of education, educational initiatives tailored to different educational backgrounds are needed to bridge knowledge gaps. Moreover, the resolution of MP pollution demands a comprehensive strategy encompassing individual initiatives, community mobilization, and structural reforms. Ultimately, fostering a collective commitment to conscientious consumption and environmental guardianship will prove pivotal in alleviating the adverse effects of MP contamination.

20.4.1

Education and Public Engagement

According to the SDGs, MPs, as a substance that exerts long-term and irreversible effects on the environment, must become a key focus of future environmental education. Therefore, scientific education should encompass issues related to environmental protection. Environmental knowledge and values serve as crucial starting points for environmental education.

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The challenge of reducing environmental plastic pollution is reflected in several SDGs. Through education people can better understand the contribution of their behaviors to MP pollution, leading them to be more willing to change habits that generate plastic waste in their daily lives and take more environment-friendly actions. There are various forms of education: 1) Classroom Education: Educational institutions can incorporate the issue of MP pollution into different subjects such as science, environmental education, or sociology. By introducing relevant case studies, videos, charts, and stories, students can gain a deeper understanding of the sources, impacts, and solutions to MPs. 2) Promotion and Media: Utilize various media platforms including social media, television, radio, newspapers, and online news to disseminate information and warnings about MPs to the public. Design attention-grabbing promotional materials and advertisements to raise awareness about this issue. 3) Exhibitions and Events: Organize exhibitions, forums, seminars, and workshops on plastic pollution and MPs to provide the public with opportunities to engage, interact, and learn from experts. Showcase innovative solutions and feasible actions to inspire active participation in solving this issue. 4) Community Engagement and Volunteer Activities: Encourage community organizations, schools, and businesses to participate in beach clean-ups, waste recycling, and sustainable development projects, involving the public directly in addressing MP pollution. Through practical actions, raise awareness and promote environmental initiatives. 5) Online Resources and Games: Provide online educational resources, interactive games, and applications for people to access knowledge and information about MPs anytime, anywhere. These platforms can offer engaging and easily understandable content to attract more individuals to participate in environmental actions. The integrated application of these educational methods can significantly increase public awareness of MPs, encouraging more people to engage in actions to reduce plastic pollution. The collaborative project “Clean Community Clean Coast” (4Cs) aims to promote applied research and outreach activities in Pinellas County, Florida, and Atlanta, Georgia (Torres et al., 2019). This project has attracted the participation of thousands of youth from municipal authorities, city staff, educators, and civil organizations. Led by the College of Marine Science at the University of South Florida (USF), the research collaborates with the College of Arts and Design at Georgia State University, the St. Petersburg College of Education at USF, and the College of Behavioral and Community Sciences at USF. Community partners include Keep Pinellas Beautiful, Tampa Bay Watch, Girls Inc. of Pinellas, among other relevant organizations. Research methods include opinion and assessment meetings, which involve focus groups of middle and high school students, as well as community forums aimed at exploring the impact of social norms and attitudes on littering behavior among teenagers. Furthermore, the project utilizes public art as an educational tool, engaging young people in creating sculptures made from marine debris. Additionally, the team has developed informal education modules and supplementary teacher resources, along with hosting youth environmental leadership workshops to enhance high school students’ engagement. It is worth noting that the promotion of “social media” is playing an increasingly important role

20.5 Community Analysis-Based Models

in everyday life (Da Costa et al., 2020). Media plays a crucial role in drawing attention to emerging environmental issues for the general public and policymakers. More importantly, media can influence public awareness and political action, shaping public and policy discussions. The issue is not just in media coverage; many studies also discuss how certain issues become part of ideological processes at specific times and under specific conditions. Media simplifies complex scientific issues for viewers and provides them with “narratives” that they can engage with and understand. The attention given to certain issues often mirrors societal and media priorities rather than being solely driven by rigorous scientific evaluation (Henderson & Green, 2020). Behavior change and multilevel governance are crucial in preventing MP leakage into the environment among ordinary citizens, governments, industries, nongovernmental organizations, academia, fishermen, and local communities. Therefore, raising environmental literacy and awareness among youth and adults and encouraging stakeholders to advocate for reducing plastic pollution are important strategies in addressing the issue of littering.

20.5 Community Analysis-Based Models This chapter should introduce the application of community analysis models in MP management, including how to use community analysis models to assess the situation of MP pollution and analyze the sources, pathways and fate of MPs: Track Marine Plastic Debris (TrackMPD) is a three-dimensional non-Lagrangian particle tracking numerical model designed to simulate the transport of plastic waste in marine and coastal systems. Renowned for its structured and consistent modeling framework, this model satisfies the criteria for flexibility, scalability, and interchangeability. It is based on the Particle Tracking and Analysis Toolset (PaTATO), which can utilize velocity data from multiple sources, such as various Ocean General Circulation Models including the Princeton Ocean Model, Regional Ocean Modeling System, and the Massachusetts Institute of Technology General Circulation Model, as well as from satellite observations. The model is capable of calculating both two-dimensional and three-dimensional forward and backward trajectories. The TrackMPD consists of a series of coupled, interactive modules that execute specific functions independently, such as defining behavior, reading inputs, implementing physical processes, or generating outputs. This modular structure permits the independent development of modules and facilitates the straightforward integration of new modules into the model without necessitating modifications to other components. Moreover, TrackMPD stands out as a user-friendly tool developed in Mat lab, designed to cater to a wide audience with ease of access. It boasts the capability to simulate a diverse array of processes, encompassing windage, beaching, resuspension, degradation, biofouling, sinking, and sedimentation. Notably, the sinking and sedimentation processes are intricately influenced by factors such as particle density, size, shape, fouling state, and degradation status. What sets this model apart is its adaptability, allowing for the integration of novel processes and behaviors, as well as adjustments to existing processes based on emerging experimental findings or specific application needs. TrackMPD models play a pivotal role in unraveling the origins, trajectories, and destinies

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of MP debris (MPD). The models are capable of addressing gaps present in other models, particularly in three key aspects: (a) utilization of three-dimensional methodologies; (b) compatibility with diverse ocean models; and (c) consideration of an extensive array of physical processes and MPD behaviors, contingent upon particle dynamic characteristics, aggregation, and degradation status (Jalón-Rojas et al., 2019). Markovian Models, a type of mathematical model, are utilized to depict the probabilities of transitions between different states within a system. Researchers utilized a Markovian model to investigate the transport of MPs in open-channel flows. By introducing a Markov predictive model, the study explored the transport behavior of actual PE MP particles in open-channel flows (referring to the movement of fluids, typically water, in an open channel or waterway). Open-channel flows are commonly used to describe the movement of water in natural and artificial bodies of water such as rivers, streams, canals, and waterways. In hydrology and fluid mechanics, research on open-channel flows is crucial for understanding water movement, hydrological cycles, water resources management, and other related aspects. Studying the transport of MPs in open-channel flows requires an understanding of the characteristics of open-channel flows and the influence of water flow dynamics on the transport of MPs. By investigating the transport behavior of MPs in open-channel flows, we can better comprehend the migration and distribution of MPs in water bodies, thereby aiding in the development of effective environmental protection and pollution control measures. This model is distinguished by a unique characteristic where transition probabilities are solely determined by the current state, independent of past states. Markovian Models find extensive applications across various domains including physics, biology, economics, and computer science. In the field of environmental science, Markovian Models are employed to simulate and predict the dynamic behaviors of diverse systems such as climate change, ecological system variations, and hydrological systems. Particularly in MP transport studies, scientists leverage Markovian Models to analyze and forecast the transport behaviors of MPs in water flow, thereby enhancing the comprehension and mitigation of MP pollution issues (Xing et al., 2022). Another novel numerical model named ADVECT is used to simulate the three-dimensional dispersion of floating plastic debris in the global oceans (Klink et al., 2022). This model considers characteristics such as the size, shape, and density of plastic particles, as well as factors such as ocean currents, wind-driven drift, wave-induced vertical mixing, and buoyancy-induced vertical transport, to calculate the three-dimensional trajectories of these particles. By simulating the distribution of plastic particles of varying sizes, shapes, and densities on the global ocean surface, within the water column, and on the seabed, researchers have observed that buoyant particles tend to sort based on their size in the ocean, being influenced by wind-driven drift and ascent rates both at the surface and within the water column. The significance of this study lies in providing a deeper understanding of the transport processes of plastic pollution in the marine environment. By simulating the behavior of plastic particles in the oceans, we can gain clearer insights into the distribution patterns of plastics in the oceans and the impacts of various factors on their transport and dispersion. This aids in conducting risk assessments, formulating effective plastic reduction strategies, and laying the groundwork for the protection of marine environments and ecosystems.

20.6 Conclusions

The Gaussian Mixture Model (GMM) is an effective method for handling the distribution and characteristics of plastic particles on the surface of the ocean. This model can categorize plastic particles based on their interrelationships and distribution in terms of different categories, sizes (length and width), and polymer types. Through the analysis of over 6,900 plastic particles in the Atlantic Ocean, researchers revealed potential distribution patterns and correlations between sizes and polymer types among different categories. These findings are crucial for monitoring plastic pollution and assessing risks. By employing the GMM, researchers can more accurately describe and classify plastic particles on the ocean surface and uncover the relationships between size and polymer type. Utilizing a statistical approach known as latent class analysis for the recognition of floating large plastic and MP particles as distinct subsets, researchers employed infrared spectroscopy and image analysis to evaluate the characteristics of 6,942 particles and items retrieved from the Atlantic Ocean. Through GMM, the research revealed six primary normal distributions based on physical dimensions, with two distributions distinguished within each category of fragments, films, and filaments. These distinct categories exhibited notable discrepancies in polymer compositions. Furthermore, results indicated that smaller films and fragments demonstrated a higher correlation between length and width, implying their approximate equality in size across both dimensions. Conversely, larger films and fragments exhibited a lower correlation between height and length/ width, suggesting greater shape variability for larger particles, thus linking plastic fragmentation to particle rounding. These findings offer valuable insights for improving risk assessment methodologies and for simulating the fragmentation and dispersal of plastics within the marine environment. Additionally, they underscore the utility of GMM as a viable approach for generating marine plastic distribution charts, offering advantages over methods that rely on arbitrary classifications or assume independence or normal distribution of particle sizes. These findings will enrich the development of simulation and predictive models concerning plastic pollution, thereby advancing our comprehension of plastic distribution and its impacts within marine ecosystems. Furthermore, this research provides important references and methodologies for future monitoring and management of plastic pollution (Alkema et al., 2022). People are concerned about the fate, transport, and potential toxicity of MPs in the natural environment. However, challenges in technology and practice, such as the diversity of plastics and their widespread distribution in the environment, often hinder the use of real-world plastics for risk assessment. Community analysis models can effectively address these issues.

20.6 Conclusions The production and indiscriminate disposal of plastics are continuously increasing, posing a serious threat to our environment, aquatic organisms, food safety, human health, and societal well-being. With the ongoing development of society, people have gained a deeper understanding of the issue of plastic pollution, further recognizing the impacts of plastics on the environment, economy, society, public safety, and personal health. This has

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prompted governments at all levels and the international community to actively formulate regulatory measures to address the various challenges posed by plastic pollution. While some effective measures have been implemented, further expansion and coordination of policies at national and international levels are needed, along with the introduction of more measurable tools to better assess the impacts of these policies. Efforts to address plastic pollution on a global scale require increased support for scientific research, policy development, and international cooperation. Only through collective efforts can we effectively tackle the growing problem of plastic pollution, safeguarding our planet and the living environment for future generations. Therefore, active participation and cooperation from all global stakeholders are urgently needed to ensure that we can collectively achieve solutions to the issue of plastic pollution and make positive contributions to the sustainable development of our planet.

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21 Life Cycle and Techno-Economic Assessment of Microplastics Remediation Technologies and Policies Almeenu Rasheed, Divyanshu Sikarwar, and Sovik Das Department of Civil Engineering, Indian Institute of Technology Delhi, New Delhi, India

21.1 Introduction Analyzing microplastic (MP) remediation technologies by utilizing tools such as life cycle assessment (LCA) and techno-economic assessment (TEA) is necessary to identify the environmental impacts contributed as part of implementing the remediation technologies. Moreover, LCA and TEA analyses aid in distinguishing the different technologies capable of MP remediation based on various impact categories such as greenhouse gas (GHG) emissions, eutrophication potential, human toxicity potential, etc. while prioritizing sustainability and feasibility of the technique (Savla et al., 2021). Even though conventional wastewater treatment technologies are applied for MP remediation, various studies demonstrate the deficiency of conventional technologies in reducing the toxicity of the prevailing MPs, subsequently harming the ecosystem over time. On the other hand, TEA analyses the cost requirements during the construction, maintenance, and operation of the considered technology along with analyzing any revenue generation from the same (Savla et al., 2021). Moreover, the essence of LCA and TEA analyses is to recognize an economically feasible method that is technologically efficient and has the least environmental impacts.

21.2 Technological Efficiency and Social Impact The term technological efficiency describes the effectiveness of various MP remediation technologies in removing MPs from the considered matrix, which can be either soil, water, or air. The technological efficiency of the techniques is demonstrated as the percentage of MP released through the process, compared to the inlet MP concentration provided to the process. However, the majority of the MP remediation methods neglect the contribution of separated-out MPs, which are entrapped within the sludge, in calculating the effectiveness of the treatment method. Moreover, the sewage sludge from wastewater treatment plants are considered as a major MP pollutant source in European Union countries, thus

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appropriate sludge management measures are implemented at wastewater treatment plants and the disposal of untreated sludge on agricultural land is strictly prohibited unless necessary in most EU countries (Usman et al., 2022). Also, adoption measures to mitigate the effects and to control the transport of plastic pollutants to marine habitats were taken at the United Nations Environmental Assembly of the United Nations Environment Programme (UNEP) in 2019, as a result of the growing concern about MP pollution, globally (Usman et al., 2022). However, proper awareness and implementation of strict guidelines are necessary to halt and reverse the ill-effects caused by the persistently accumulating MP pollutants. Studies indicate that physical MP remediation processes such as filtration, adsorption, and density separation (DS) exhibit high efficacy in MP separation by demonstrating 75–90%, 92–98%, and 83–97% of MP removal, respectively (Duong et al., 2022; Jiang et al., 2020; Rasheed et al., 2023). In addition, the utilization of membrane filtration techniques such as ultrafiltration and reverse osmosis methods for MP separation from water matrices has enhanced the MP removal to 96.97% and 90%, respectively (Tadsuwan & Babel, 2022; Talvitie et al., 2017). Moreover, studies demonstrate that combining various treatment methods, such as coagulation and filtration, aids in enhancing the efficacy of MP separation from 73 to 90%, by forming agglomerates around the small-sized MP particles, which subsequently facilitates better MP separation through the filtration process (Ahmed et al., 2021). However, the study by Jiang et al. (2020) illustrated that 75.7% of the filtered MPs were transferred to the sludge, which is subsequently dried and applied as fertilizers thereafter. The MP-entrapped sludge has the potential to cause soil contamination leading to terrestrial contamination as well. The presence of MPs within the roots of strawberry plants and in various vegetables such as potatoes, cucumber, tomatoes, etc. is the indication of the extent of terrestrial contamination of MP particles (Giannetto et al., 2023; Zhang et al., 2023). Moreover, these MP particles illustrate the potential of social impacts such as affecting the health and well-being of the living beings within the affected ecosystem. In contrast to physical remediation methods, chemical treatment methods aid in mineralizing the MP particles to less or nontoxic substances rather than merely separating them from the matrix. Several chemical remediation methods such as the advanced oxidation process, ozonation, and Fenton process oxidize MPs into less toxic particles with the aid of oxidizing species such as hydroxyl radicals, ozone, Cl− species, etc. (Ahmed et al., 2021; Rasheed et al., 2023). In this regard, the study on MP removal through the photocatalysis method demonstrated 65% degradation of polypropylene MPs due to the attack of formed hydroxyl radicals on the C─C bonds of the polymer, under visible light (Uheida et al., 2021). Through mineralization of the MPs, these remediation methods eliminate the potential detrimental effects of MPs on the ecosystem. However, the increased use of chemicals in these methods leads to GHG emissions and abiotic resource depletion leading to various impacts on the ecosystem (Rasheed et al., 2023). Further, LCA studies indicating the impacts of these remediation methods are minimal, thus there is a strong need to analyze the various environmental effects caused due to the implementation of chemical-based MP remedial methods. In addition to physical and chemical treatment methods, biological treatment methods are proven to be beneficial in separating out and partially degrading the MPs from various matrices. Analytical research on biological MP remediation methods such as activated

21.3 Economic Aspect and Cost–Benefit Analysis

sludge process (ASP) and constructed wetlands (CW) demonstrated 64–80% and 96–99% removal efficiency, respectively, from the influent water matrix (Lares et al., 2018; Liu et al., 2019). Whereas implementation of hybrid methods such as electrochemical oxidation, electro-Fenton, electrocoagulation, and membrane bioreactor (MBR) techniques has exhibited MP removal efficiency of 58%, 56%, 91–93%, and 92–99%, respectively (Egea-Corbacho et al., 2023; Kiendrebeogo et al., 2021; Lares et al., 2018; Miao et al., 2020; Shen et al., 2022). However, in ASP, MBR, and CW techniques, the MP particles are entrapped within the sludge of ASP and MBR or retained within the CW, which later needs to be posttreated before releasing it into the ecosystem. The raw sludge excluded from ASP, MBR, or desorbed sludge from CW, when utilized as fertilizers, elevates the probability of terrestrial contamination; moreover, the transport of these MPs from agricultural land to water sources through stormwater runoff leads to surface water contamination, ultimately triggering marine contamination (Zhang et al., 2020). However, various emerging treatment methods for MP removal such as bioelectrochemical systems (BESs) are still under research to identify the potential and efficacy for MP removal. Also, there exists an essential demand for identifying various societal and environmental impacts of the emerging MP remediation methods.

21.3 Economic Aspect and Cost–Benefit Analysis The economic viability of new technology is an essential component for its commercialization; hence, TEA is used to determine the economic feasibility of the process based on the cost incurred during construction, operation, maintenance, and end of life. In this context, Mahmoudnia et al. (2023) examined MP removal through electrocoagulation, where energy, electrode, and overall operating cost added up to US$0.0456/m3 of wastewater treated. In another examination, the cost of MP removal through flotation separation (FS), DS, and electrostatic separation (ES) was US$0.011, US$1.19, and US$1.07, respectively (Jiang et al., 2022). The electrical cost was the major contributor to the overall cost for all these treatment methods investigated above, accounting for almost 100% of the overall cost in ES, 77.7% in DS, and 44.8% in FS method (Jiang et al., 2022). Further, in the FS method, freshwater (45.7%) and wastewater (6.5%) costs also contributed significantly to the overall expenditure of the treatment (Jiang et al., 2022). However, the FS method was the most costeffective due to minimal electricity consumption compared to the DS and ES techniques. In contrast to physical remediation methods, chemical treatment methods possess high energy density, consequently increasing the cost of treatment. In this regard, chemical oxidation methods demonstrated MP removal efficiency of 50–98% from water with MP size ranging from 0.1 to 45 μm (Allé et al., 2021; Kiendrebeogo et al., 2021; Nabi et al., 2020; Uheida et al., 2021). To add further, in one investigation, Kiendrebeogo et al. (2021) reported the cost of MP removal through the electrooxidation method to be US$68.5/m3 of water with 89% MP removal efficiency in 6 hr of electrolysis. Conversely, biological treatment methods demonstrated low removal efficiency of 20–58% and higher retention time and were suggested to be cost effective as well as eco-friendly for the removal of MP from water (Muhonja et al., 2018; Skariyachan et al., 2018). Apart from physical treatment methods, very few

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investigations on chemical and biological treatment methods have studied the economic aspects of MP removal from water, providing scope for future research. Furthermore, Savla and researchers’ investigation outlined labor and electricity consumption costs as significant expenditures, accounting for around 35% and 34%, respectively, of the total cost for the operation of a conventional treatment plant (Savla et al., 2021). Thus, the automation of the treatment facility could significantly reduce the operation cost of the concerned facility but would increase the capital expenditure (Yadav et al., 2023). Similarly, construction and maintenance costs for BESs such as microbial fuel cells, microbial electrolysis cells, etc., could be reduced by employing durable and cost-effective electrodes and membranes combined with monitory gain from bioelectricity and other valuable recovered during MP remediation from wastewater. However, MP removal through filtration and membrane techniques incur high costs due to the use of membrane, media, and energy required for filtration, backwashing, and treatment of sludge. Likewise, in biological methods, although construction costs are low, sludge handling and treatment costs are very high due to the entrapment of the MP in the sludge. However, at present, the cost differentiation between the bioelectrochemical and biological/physical methods is still significant for MP removal from wastewater. Nonetheless, to have a comprehensive economic outlook on the efficient MP removal techniques, additional research is needed on the TEA of MP removal via different technologies.

21.3.1

SWOT Analysis

The Strength-Weakness-Opportunity-Threat (SWOT) analysis of MP remediation technologies in terms of technological efficacy, societal impacts, and sustainability aids in determining the underlying challenges and future opportunities associated with various MP remedial methods. The SWOT analysis on treatment technologies aids in navigating through these techniques by evaluating their strengths and weaknesses so as to mitigate the potential threats and optimize the available opportunities. According to SWOT analysis, the environmental compatibility and negligible formation of toxic by-products during MP separation are the major strengths of various physical treatment methods such as filtration, DS, membrane separation, etc. and biological treatment methods such as ASP, CW, etc. (Ahmed et al., 2021). However, these strengths are countered by the entrapment of MPs in the sludge during physical and biological processes, leading to the spread of MP toxicity in different sectors of the ecosystem. In methods of filtration and membrane separation, the separated-out MPs from the wastewater matrices get entrapped with in the remaining residue, which subsequently reaches the environment from the excluded sludge. Thus, posttreatment of the MP-entrapped sludge is necessary to bring down the toxicity spread of MPs in the environment (Rasheed et al., 2023). Similarly, in biological processes such as ASP and CW, the action of microbes and macroinvertebrates aids in the transfer of MPs from wastewater to the sludge, which further requires posttreatment methods before disposing it into the environment. Moreover, the higher land footprint and the elevation of the overall costs due to the posttreatment requirements of sludge are additional drawbacks of these physical and biological remedial methods (Rasheed et al., 2023). However, in case of advanced oxidation processes and ozonation, the polymeric chains of MPs are degraded into by-products with the action of oxidizing agents, which is

21.3 Economic Aspect and Cost–Benefit Analysis

characterized as the dominant strength of chemical methods of MP removal (Ahmed et al., 2021). Whereas, in case of electrochemical oxidation and electro-Fenton processes, the MPs are mineralized into nontoxic compounds, which aid in the complete removal of MPs from the wastewater matrices. In addition, the less land footprint requirement and the minimal sludge formation are the dominant strengths of electrochemical remediation processes (Rasheed et al., 2023).However, the increased GHG emissions, abiotic resource depletion, and increase in cost associated with the usage of chemicals and electrodes are considered as the threats and weaknesses for chemical treatment processes such as ozonation, electrochemical oxidation, advanced oxidation processes, etc. (Rasheed et al., 2023). Nevertheless, the emerging hybrid methods such as BESs have an additional opportunity to produce valuables such as bioelectricity, H2, etc. simultaneously while removing the MP pollutants, compared to other conventional removal methods. With deeper research in BESs, the challenges of their limited scalability and electrode biofouling can be rectified economically and sustainably. This analysis, however, provides different alternative suggestions for existing MP remediation techniques on the grounds of improvement, thereby guiding researchers to develop sustainable and economical treatment technologies (Figure 21.1).

Figure 21.1 SWOT Analysis on MP Remediation Through (a) Physical Treatment Methods, (b) Biological Treatment Methods, and (c) Chemical Treatment Methods

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21 Life Cycle and Techno-Economic Assessment of Microplastics Remediation Technologies and Policies

21.4

LCA of Treatment Techniques

LCA is a technique typically used to determine a product, technology, or service’s impact on the surrounding environment. Further, the impact assessment is performed by estimating midpoint indicators consisting of impact categories and endpoint indicators containing categories such as ecosystem quality, resource depletion, and human health. In this context, Jiang et al. (2022) performed an investigation to compare the environmental impact of MP removal with functional unit of 1 kg sediment containing 1 g of MP and gate-to-gate system, through FS, ES, and DS treatment methods. In this investigation, it was observed that ES and DS demonstrated 290 times (5.10 kg of CO2 eq.) and 177 times (3.12 kg of CO2 eq.) more global warming potential (GWP), respectively, as compared to the FS method with GWP of 0.017 kg of CO2 eq. (Jiang et al., 2022). A similar trend was observed for other impact categories, such as primary energy demand, abiotic depletion potential, respiratory inorganics, photochemical ozone formation, and ecotoxicity, where FS was found more environment friendly than DS and ES. In addition, the FS method outperformed the DS and ES techniques due to its minimal energy requirement and produced lesser sludge. Nevertheless, this investigation did not account for the toxicity, fate, or indirect emissions of MPs trapped in sludge. Incorporation of these criteria will enhance the credibility of the analyses to further gauze their environmental sustainability and open opportunities for improvement of the treatment process. Moreover, the dumping of sludge mainly from primary and secondary treatment entraps MPs, which could further release heavy metals and other contaminants sorbed on the MP surface, and thus can be hazardous to humans and aquatic ecosystems. In another veneration, Jiang et al. (2023) investigated the environmental impact of micro/ nanoplastic remediation using preparation of one membrane as functional unit and gate-to-gate boundary condition. As per the current investigation, the ecosystem quality suffered the maximum damage compared to other damage categories; for instance, the impact on human health and resources was around 2,800 and 3 × 105 times, respectively, lower than the impact on ecosystem quality. Further, impact categories such as malodourous air, marine aquatic ecotoxicity, marine sediment ecotoxicity, etc. had the maximum contribution in deteriorating the ecosystem quality due to MP removal from wastewater using cellulose membrane. Using physical treatment procedures for MP removal, in conjunction with sludge drying and disposal processes, will inevitably result in higher energy usage, GWP, and land footprint. Additionally, sludge management is also necessary for biological treatment methods, which raises energy consumption and GWP. On the other hand, chemical treatments such as advanced oxidation processes mineralize the presence of MPs in wastewater, which increases the GWP due to the release of CO2 although the toxicity of the MPs to human and aquatic life reduces due to the complete mineralization of MP when treated via chemical methods. However, it’s difficult to conclude the comparison of different MP treatment technologies as there is a dearth of data on LCA of MP removal, specifically for biological and chemical methods. Nonetheless, the lack of research articles on the LCA of MP removal techniques highlights the need to expand this area of study with more comprehensive works to enable an accurate interpretation of the environmental impact of these technologies (Table 21.1).

Table 21.1 TEA and LCA on MP Remediation Techniques Life cycle assessment (LCA) Technology

Froth floatation

Electrostatic separation

Raw materials

Impact category (unit)

Quantity

Functional unit

Remarks

References

Electricity Fresh water Sodium oleate Terpineol Calcium chloride

GWP (kg CO2 eq.) PED (MJ) ADP (kg antimony eq.) ET (CTUe) EP (kg PO43−eq.) HT-cancer (CTUh) CO2 (kg) SO2 (kg)

0.0175 0.2333 2.0823 × 10−7 0.00005 8.493 × 10−6 2.78 × 10−12 0.016 5.55 × 10−5

Disposal of 1 kg of sediment containing 1 g MP

Since floatation separation works on the principle of hydrophobicity, hence minimal energy and chemicals are required for MP removal.

Jiang et al. (2022)

GWP (kg CO2 eq.) PED (MJ) ADP (kg antimony eq.) ET (CTUe) EP (kg PO43−eq.) HT-cancer (CTUh) CO2 (kg) SO2 (kg)

3.116 41.325 3.69 × 10−5 8.99 × 10−3 1.07 × 10−3 4.92 × 10−10 2.876 9.83 × 10−3

High PED and ET values due to high energy demand and use of chemicals such as CaCl2.

(Continued)

Table 21.1 (Continued) Life cycle assessment (LCA) Technology

Raw materials

Density separation

Filtration using a cellulose membrane

Fe4O3 Tris–HCl DA-HCl Electricity Hydrochloric acid

Impact category (unit)

Quantity

GWP (kg CO2 eq.) PED (MJ) ADP (kg antimony eq.) ET (CTUe)

5.104 67.678 6.04 × 10−5 0.0147

EP (kg PO43− eq.) HT-cancer (CTUh) CO2 (kg) SO2 (kg) AP (kg SO2 eq.) GWP (kg CO2 eq.) HT (kg 1,4-DB eq.) EP (kg PO43− eq.) LU (m2) MAETP (kg 1,4-DB eq.) ADP (kg antimony eq.)

1.76 × 10−3 8.07 × 10−10 4.711 0.016 2.10 × 10−5 2.72 × 10−2 3.31 × 10−3 1.45 × 10−4 8.48 × 10−6 3.33 × 10−3 2.580 × 10−4

Functional unit

Remarks

References

High SO2, CO2, and NOx emissions directly increase the adverse environmental impact.

Preparation of a membrane

High MAETP and HT value due to entrapment of MPs in sludge.

Jiang et al. (2023)

Functional unit

Remarks

References

One kilogram of sediment

Removal of MP at low cost due to low electricity use

Jiang et al. (2022)

Techno-economic assessment (TEA) Technology

Froth floatation

Substrate

Electricity Fresh water Sodium oleate

Electricity consumption (kWh) Landfilling sludge

Cost ($) a

0.0042 2.21 × 10−6a

Electrostatic separation

Terpineol Calcium chloride

Density separation Filtration using a cellulose membrane

Fe4O3 Tris–HCl DA-HCl electricity Hydrochloric acid

Electricity consumption (kWh) Landfilling sludge

1.07a 5.74 × 10−8a

Maximum energy cost and minimal sludge management cost

Electricity consumption (kWh) Landfilling sludge

0.92a 0.013x

High cost due to more energy requirements and sludge management

Electricity consumption (kWh) Raw materials

0.028b 4.138c

50 mm diameter membrane

Sludge management cost not considered

Jiang et al. (2023)

ADP, abiotic depletion potential; AP, acidification potential; CTUe, comparative toxic units equivalent; CTUh, comparative toxic unit for human; DB, dichlorobenzene; EP, eutrophication potential; ET, ecotoxicity; GWP, global warming potential; HT, human toxicity; LU, land use; MAETP, marine aquatic ecotoxicity potential; MJ, mega joules; PED, potential energy demand. a 1 CNY = $0.14 used for yuan to dollar conversion. b cost of 1 unit electricity in China as $0.09. c Sigma Aldrich (www.sigmaaldrich.com)—For raw materials cost calculation.

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21 Life Cycle and Techno-Economic Assessment of Microplastics Remediation Technologies and Policies

21.5

Conclusion

The utilization of tools such as LCA, TEA, and SWOT analysis aids in determining the balance between environmental sustainability, economic feasibility, and technological efficiency of different MP remedial methods. However, limited studies have been conducted on identifying the environmental impacts caused during the entire process of MP treatment in terms of GWP, ADP, ET, etc., which demonstrates the strong need to incorporate LCA in emerging technologies to prioritize sustainability as a major factor of concern. In addition, TEA and SWOT analysis aids in executing strategic decisions based on the pros, cons, possibilities, and vulnerabilities of various MP treatment techniques. Consequently, this aids in improving the potentialities of the existing treatment techniques by working on their disadvantages and enhancing their advantages on the basis of sustainable and economical MP removal. Moreover, exploring the technical and economical efficacies guides researchers in creating a strong framework for implementing efficient guidelines and policies for halting and reverting the societal and environmental impacts caused by the MPs.

References Ahmed, M. B., Rahman, M. S., Alom, J., Hasan, M. S., Johir, M., Mondal, M. I. H., Lee, D.-Y., Park, J., Zhou, J. L., & Yoon, M.-H. (2021). Microplastic particles in the aquatic environment: A systematic review. Science of the Total Environment, 775, 145793. Allé, P. H., Garcia-Muñoz, P., Adouby, K., Keller, N., & Robert, D. (2021). Efficient photocatalytic mineralization of polymethylmethacrylate and polystyrene nanoplastics by TiO 2/β-SiC alveolar foams. Environmental Chemistry Letters, 19, 1803–1808. Duong, T. T., Le, P. T., Nguyen, T. N. H., Hoang, T. Q., Ngo, H. M., Doan, T. O., Le, T. P. Q., Bui, H. T., Bui, M. H., & Trinh, V. T. (2022). Selection of a density separation solution to study microplastics in tropical riverine sediment. Environmental Monitoring and Assessment, 194, 1–17. Egea-Corbacho, A., Martín-García, A. P., Franco, A. A., Quiroga, J. M., Andreasen, R. R., Jørgensen, M. K., & Christensen, M. L. (2023). Occurrence, identification and removal of microplastics in a wastewater treatment plant compared to an advanced MBR technology: Full-scale pilot plant. Journal of Environmental Chemical Engineering, 11(3), 109644. Giannetto, D., Aydın, R. B., Yozukmaz, A., & Temiz, F. (2023). Occurrence of microplastics in most consumed fruits and vegetables from Turkey and public risk assessment for consumers. Life (Basel), 13, 1686. Jiang, H., Zhang, Y., Bian, K., Wang, C., Xie, X., Wang, H., & Zhao, H. (2022). Is it possible to efficiently and sustainably remove microplastics from sediments using froth flotation? Chemical Engineering Journal, 448, 137692. Jiang, J., Wang, X., Ren, H., Cao, G., Xie, G., Xing, D., & Liu, B. (2020). Investigation and fate of microplastics in wastewater and sludge filter cake from a wastewater treatment plant in China. Science of the Total Environment, 746, 141378. Jiang, Z., Wang, X., Zhao, H., Yang, Z., Zhou, J., Sun, X., Yang, H., Wang, C., & Huan, S. (2023). Micro/nano-plastic removal from wastewater using cellulose membrane: Performance and life cycle assessment. Separation and Purification Technology, 317, 123925.

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Kiendrebeogo, M., Estahbanati, M. K., Mostafazadeh, A. K., Drogui, P., & Tyagi, R. D. (2021). Treatment of microplastics in water by anodic oxidation: A case study for polystyrene. Environmental Pollution, 269, 116168. Lares, M., Ncibi, M. C., Sillanpaa, M., & Sillanpaa, M. (2018). Occurrence, identification and removal of microplastic particles and fibers in conventional activated sludge process and advanced MBR technology. Water Research, 133, 236–246. Liu, X., Yuan, W., Di, M., Li, Z., & Wang, J. (2019). Transfer and fate of microplastics during the conventional activated sludge process in one wastewater treatment plant of China. Chemical Engineering Journal, 362, 176–182. Mahmoudnia, A., Mehrdadi, N., Baghdadi, M., & Moussavi, G. (2023). Simultaneous removal of microplastics and benzalkonium chloride using electrocoagulation process: Statistical modeling and techno-economic optimization. Environmental Science and Pollution Research, 30(24), 66195–66208. Miao, F., Liu, Y., Gao, M., Yu, X., Xiao, P., Wang, M., Wang, S., & Wang, X. (2020). Degradation of polyvinyl chloride microplastics via an electro-Fenton-like system with a TiO2/graphite cathode. Journal of Hazardous Materials, 399, 123023. Muhonja, C. N., Makonde, H., Magoma, G., & Imbuga, M. (2018). Biodegradability of polyethylene by bacteria and fungi from Dandora dumpsite Nairobi-Kenya. PLoS One, 13(7), e0198446. Nabi, I., Li, K., Cheng, H., Wang, T., Liu, Y., Ajmal, S., Yang, Y., Feng, Y., & Zhang, L. (2020). Complete photocatalytic mineralization of microplastic on TiO2 nanoparticle film. Iscience, 23 (7), 101326. Rasheed, A., Sharma, N., Surampalli, R. Y., & Das, S. (2023). Evaluating treatment solutions: Critical review on technologies employed for microplastic removal from water matrices. Current Opinion in Environmental Science & Health, 36, 100516. Savla, N., Pandit, S., Verma, J. P., Awasthi, A. K., Sana, S. S., & Prasad, R. (2021). Technoeconomical evaluation and life cycle assessment of microbial electrochemical systems: A review. Current Research in Green and Sustainable Chemistry, 4, 100111. Shen, M., Zhang, Y., Almatrafi, E., Hu, T., Zhou, C., Song, B., Zeng, Z., & Zeng, G. (2022). Efficient removal of microplastics from wastewater by an electrocoagulation process. Chemical Engineering Journal, 428, 131161. Skariyachan, S., Patil, A. A., Shankar, A., Manjunath, M., Bachappanavar, N., & Kiran, S. (2018). Enhanced polymer degradation of polyethylene and polypropylene by novel thermophilic consortia of Brevibacillus sps. and Aneurinibacillus sp. screened from waste management landfills and sewage treatment plants. Polymer Degradation and Stability, 149, 52–68. Tadsuwan, K., & Babel, S. (2022). Microplastic abundance and removal via an ultrafiltration system coupled to a conventional municipal wastewater treatment plant in Thailand. Journal of Environmental Chemical Engineering, 10(2), 107142. Talvitie, J., Mikola, A., Koistinen, A., & Setala, O. (2017). Solutions to microplastic pollution – Removal of microplastics from wastewater effluent with advanced wastewater treatment technologies. Water Research, 123, 401–407. Uheida, A., Mejía, H. G., Abdel-Rehim, M., Hamd, W., & Dutta, J. (2021). Visible light photocatalytic degradation of polypropylene microplastics in a continuous water flow system. Journal of Hazardous Materials, 406, 124299. Usman, S., Abdull Razis, A. F., Shaari, K., Azmai, M. N. A., Saad, M. Z., Mat Isa, N., & Nazarudin, M. F. (2022). The burden of microplastics pollution and contending policies and regulations. International Journal of Environmental Research and Public Health, 19(11), 6773.

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Yadav, R. K., Das, S., & Patil, S. A. (2023). Are integrated bioelectrochemical technologies feasible for wastewater management? Trends in Biotechnology, 41(4), 484–496. Zhang, C., Yue, N., Li, X., Shao, H., Wang, J., An, L., & Jin, F. (2023). Potential translocation process and effects of polystyrene microplastics on strawberry seedlings. Journal of Hazardous Materials, 449, 131019. Zhang, L., Xie, Y., Liu, J., Zhong, S., Qian, Y., & Gao, P. (2020). An overlooked entry pathway of microplastics into agricultural soils from application of sludge-based fertilizers. Environmental Science & Technology, 54(7), 4248–4255.

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22 Case Studies on Microplastic Contamination with a Focus on the Impact of the COVID-19 Pandemic Lourembam Nongdren1, Sai Lahar Reddy1, Biswajit Samal2, Kumar Raja Vanapalli1, and Brajesh K. Dubey2,3 1

Civil Engineering Department, National Institute of Technology Mizoram, Aizawl, Mizoram, India School of Environmental Science and Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India 3 Department of Civil Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India 2

22.1 Introduction In the past few years, microplastics (MPs) have emerged as a concerning form of pollution, with approximately 51 trillion MP particles (UN News, 2017), littered in the oceans. They have spread virtually to every corner of the globe, from the depths of the sea to the highest peaks, resulting from various sources, including industrial processes, consumer products, and the breakdown of larger plastic items, posing a harmful threat to the ecosystem and biodiversity. Due to their specific attributes, like being composed with high polymer content, nonbiodegradability, and hydrophobic nature, MPs easily enter the environment and persist there for a long duration. Several research studies have detected the widespread presence of MPs in various ecosystems, such as beaches (Maynard et al., 2021), surface water (Han et al., 2020), freshwater sediments (Shruti et al., 2019), marine sediments (Reed et al., 2018), and snow (Villanova-Solano et al., 2023). Due to their presence in various aquatic ecosystems (surface waters, oceans, estuaries, etc.), MPs directly or indirectly threaten marine organisms, which can potentially impact the food chain through biomagnification. As a result, humans are exposed to these pollutants when they consume seafood and fish. The COVID-19 pandemic has profound effects on a wide range of aspects of global life. The pandemic has influenced areas ranging from public health and the economy to social dynamics and mental well-being, affecting nearly all aspects of human existence. With the advent of the COVID-19 pandemic, the widespread utilization of personal protective equipment (PPE) as a precautionary measure has significantly increased, whereas before the pandemic, PPE was primarily employed in research laboratories and specialized healthcare facilities. Moreover, the management and regulation of disposal of plastic waste resulting from food packaging, medical packaging, and single-use plastics have not kept pace with the

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22 Case Studies on Microplastic Contamination with a Focus on the Impact of the COVID-19 Pandemic

rapid increase in demand growth, leading to significant sources of MP pollution. According to estimates, the global pandemic has resulted in the generation of 4.4–15.1 million tons of mismanaged plastic waste (Peng et al., 2021). This chapter explores the interactions between MPs and COVID-19, their implications for the environment, and the potential consequences for human health.

22.2

Microplastic Contamination

22.2.1

Definition

Depending on their sizes, plastic is usually categorized as macro- and mesoplastics (>5 mm), MPs (