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Pan J, Zhang S, Qiu X, Ding L, Liang X, Guo X. Molecular Weights of Dissolved Organic Matter Significantly Affect Photoaging of Microplastics. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:13973-13985. [PMID: 39046080 DOI: 10.1021/acs.est.4c04608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
The fate of ubiquitous microplastics (MPs) is largely influenced by dissolved organic matter (DOM) in aquatic environments, which has garnered significant attention. The reactivity of DOM is reported to be greatly regulated by molecular weights (MWs), yet little is known about the effects of different MW DOM on MP aging. Here, the aging behavior of polystyrene MPs (PSMPs) in the presence of different MW fulvic acids (FAs) and humic acids (HAs) was systematically investigated. Under ultraviolet (UV) illumination, O/C of PSMPs aged for 96 h surged from 0.008 to 0.146 in the lower MW FA (FA<1kDa) treatment, suggesting significant PSMP aging. However, FA exhibited a stronger effect on facilitating PSMP photoaging than HA, which can be attributed to the fact that FA<1kDa contains more quinone and phenolic moieties, demonstrating a higher redox capacity. Meanwhile, compared to other fractions, FA<1kDa was more actively involved in the increase of different reactive species yields by 50-290%, including •OH, which plays a key role in PSMP photoaging, and contributed to a 25% increase in electron-donating capacity (EDC). This study lays a theoretical foundation for a better understanding of the environmental fate of MPs.
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Affiliation(s)
- Jianrui Pan
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Shilong Zhang
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Xinran Qiu
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Ling Ding
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
| | - Xujun Liang
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
- Key Laboratory of Plant Nutrition and the Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China
| | - Xuetao Guo
- College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi 712100, China
- Key Laboratory of Plant Nutrition and the Agro-environment in Northwest China, Ministry of Agriculture, Yangling, Shaanxi 712100, China
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2
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Rahman E, BinAhmed S, Keyes P, Alberg C, Godfreey-Igwe S, Haugstad G, Xiong B. Nanoscale Abrasive Wear of Polyethylene: A Novel Approach To Probe Nanoplastic Release at the Single Asperity Level. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:13845-13855. [PMID: 38874627 DOI: 10.1021/acs.est.3c09649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2024]
Abstract
There is a growing concern that nanoplastic pollution may pose planetary threats to human and ecosystem health. However, a quantitative and mechanistic understanding of nanoplastic release via nanoscale mechanical degradation of bulk plastics and its interplay with photoweathering remains elusive. We developed a lateral force microscope (LFM)-based nanoscratch method to investigate mechanisms of nanoscale abrasive wear of low-density polyethylene (LDPE) surfaces by a single sand particle (simulated by a 300 nm tip) under environmentally relevant load, sliding motion, and sand size. For virgin LDPE, we found plowing as the dominant wear mechanism (i.e., deformed material pushed around the perimeter of scratch). After UVA-weathering, the wear mechanism of LDPE distinctively shifted to cutting wear (i.e., deformed material detached and pushed to the end of scratch). The shift in the mechanism was quantitatively described by a new parameter, which can be incorporated into calculating the NP release rate. We determined a 10-fold higher wear rate due to UV weathering. We also observed an unexpected resistance to initiate wear for UV-aged LDPE, likely due to nanohardness increase induced by UV. For the first time, we report 0.4-4 × 10-3 μm3/μm sliding distance/μN applied load as an initial approximate nanoplastic release rate for LDPE. Our novel findings reveal nanoplastic release mechanisms in the environment, enabling physics-based prediction of the global environmental inventory of nanoplastics.
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Affiliation(s)
- Ehsanur Rahman
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, Minnesota 55455, United States
| | - Sara BinAhmed
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, Minnesota 55455, United States
| | - Phoebe Keyes
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, Minnesota 55455, United States
| | - Claire Alberg
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, Minnesota 55455, United States
| | - Stacy Godfreey-Igwe
- Department of Mechanical Engineering, Massachusetts Institute of Technology, 33 Massachusetts Ave, Cambridge, Massachusetts 02139, United States
| | - Greg Haugstad
- Characterization Facility, University of Minnesota, 100 Union St. SE, Minneapolis, Minnesota 55455, United States
| | - Boya Xiong
- Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, 500 Pillsbury Dr SE, Minneapolis, Minnesota 55455, United States
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3
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Ma W, He J, Han L, Ma C, Cai Y, Guo X, Yang Z. Hydrophilic Fraction of Dissolved Organic Matter Largely Facilitated Microplastics Photoaging: Insights from Redox Properties and Reactive Oxygen Species. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:11625-11636. [PMID: 38848335 DOI: 10.1021/acs.est.3c11111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2024]
Abstract
Dissolved organic matter (DOM) exists widely in natural water, which inevitably influences microplastic (MP) photoaging. Nevertheless, the impacts of DOM fractions with diverse molecular structures on MP photoaging remain to be elucidated. This study explored the photoaging mechanisms of polylactic acid (PLA)-MPs and polystyrene (PS)-MPs in the presence of DOM and its subfractions (hydrophobic acid (HPOA), hydrophobic neutral (HPON), and hydrophilic (HPI)). Across DOM fractions, HPI exhibited the highest electron accepting capacity (23 μmol e- (mg C)-1) due to its abundant tannin-like species (36.8%) with carboxylic groups, which facilitated more reactive oxygen species generation (particularly hydroxyl radical), leading to the strongest photoaging rate of two MPs by HPI. However, the sequences of bond cleavage during photoaging of each MPs were not clearly shifted as revealed by two-dimensional infrared correlation spectra. Inconspicuous effects on the extent of PS- and PLA-MPs photoaging were observed for HPOA and HPON, respectively. This was mainly ascribed to the occurrence of inhibitory mechanisms (e.g., light-shielding and quenching effect) counteracting the reactive oxygen species-promoting effects. The findings identified the HPI fraction of DOM for promoting PS- and PLA-MPs photoaging rate and first constructed a link among DOM molecular structures, redox properties, and effects on MP photoaging.
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Affiliation(s)
- Weiwei Ma
- Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Jiehong He
- Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Lanfang Han
- Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Chuanxin Ma
- Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Yanpeng Cai
- Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
| | - Xiaoyu Guo
- Key Laboratory of Agro-Forestry Environmental Processes and Ecological Regulation of Hainan Province, Hainan University, Haikou 570228, China
| | - Zhifeng Yang
- Guangdong Basic Research Center of Excellence for Ecological Security and Green Development, Key Laboratory for City Cluster Environmental Safety and Green Development of the Ministry of Education, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou 510006, China
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4
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Elmer-Dixon MM, Fawcett LP, Sorensen EN, Maurer-Jones MA. Bovine Serum Albumin Bends Over Backward to Interact with Aged Plastics: A Model for Understanding Protein Attachment to Plastic Debris. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:10207-10215. [PMID: 38809092 PMCID: PMC11171446 DOI: 10.1021/acs.est.3c10028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 05/16/2024] [Accepted: 05/17/2024] [Indexed: 05/30/2024]
Abstract
Plastic pollution, a major environmental crisis, has a variety of consequences for various organisms within aquatic systems. Beyond the direct toxicity, plastic pollution has the potential to absorb biological toxins and invasive microbial species. To better understand the capability of environmental plastic debris to adsorb these species, we investigated the binding of the model protein bovine serum albumin (BSA) to polyethylene (PE) films at various stages of photodegradation. Circular dichroism and fluorescence studies revealed that BSA undergoes structural rearrangement to accommodate changes to the polymer's surface characteristics (i.e., crystallinity and oxidation state) that occur as the result of photodegradation. To understand how protein structure may inform docking of whole organisms, we studied biofilm formation of bacteriaShewanella oneidensison the photodegraded PE. Interestingly, biofilms preferentially formed on the photodegraded PE that correlated with the state of weathering that induced the most significant structural rearrangement of BSA. Taken together, our work suggests that there are optimal physical and chemical properties of photodegraded polymers that predict which plastic debris will carry biochemical or microbial hitchhikers.
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Affiliation(s)
- Margaret M. Elmer-Dixon
- Department
of Physics & Astronomy, University of
Minnesota, Duluth, Duluth, Minnesota 55812, United States
- Department
of Mechanical and Industrial Engineering, University of Minnesota, Duluth, Duluth, Minnesota 55812, United States
| | - Liam P. Fawcett
- Department
of Chemistry and Biochemistry, University
of Minnesota, Duluth, Duluth, Minnesota 55812, United States
| | - Emma N. Sorensen
- Department
of Chemistry and Biochemistry, University
of Minnesota, Duluth, Duluth, Minnesota 55812, United States
| | - Melissa A. Maurer-Jones
- Department
of Chemistry and Biochemistry, University
of Minnesota, Duluth, Duluth, Minnesota 55812, United States
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5
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Jansen MAK, Andrady AL, Bornman JF, Aucamp PJ, Bais AF, Banaszak AT, Barnes PW, Bernhard GH, Bruckman LS, Busquets R, Häder DP, Hanson ML, Heikkilä AM, Hylander S, Lucas RM, Mackenzie R, Madronich S, Neale PJ, Neale RE, Olsen CM, Ossola R, Pandey KK, Petropavlovskikh I, Revell LE, Robinson SA, Robson TM, Rose KC, Solomon KR, Andersen MPS, Sulzberger B, Wallington TJ, Wang QW, Wängberg SÅ, White CC, Young AR, Zepp RG, Zhu L. Plastics in the environment in the context of UV radiation, climate change and the Montreal Protocol: UNEP Environmental Effects Assessment Panel, Update 2023. Photochem Photobiol Sci 2024; 23:629-650. [PMID: 38512633 DOI: 10.1007/s43630-024-00552-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 02/05/2024] [Indexed: 03/23/2024]
Abstract
This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) considers the interactive effects of solar UV radiation, global warming, and other weathering factors on plastics. The Assessment illustrates the significance of solar UV radiation in decreasing the durability of plastic materials, degradation of plastic debris, formation of micro- and nanoplastic particles and accompanying leaching of potential toxic compounds. Micro- and nanoplastics have been found in all ecosystems, the atmosphere, and in humans. While the potential biological risks are not yet well-established, the widespread and increasing occurrence of plastic pollution is reason for continuing research and monitoring. Plastic debris persists after its intended life in soils, water bodies and the atmosphere as well as in living organisms. To counteract accumulation of plastics in the environment, the lifetime of novel plastics or plastic alternatives should better match the functional life of products, with eventual breakdown releasing harmless substances to the environment.
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Affiliation(s)
- Marcel A K Jansen
- School of Biological, Earth and Environmental Sciences, University College, Cork, Ireland.
| | - Anthony L Andrady
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Janet F Bornman
- Food Futures Institute, Murdoch University, Perth, Australia.
| | | | - Alkiviadis F Bais
- Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Anastazia T Banaszak
- Unidad Académica Sistemas Arrecifales, Universidad Nacional Autónoma de México, Puerto Morelos, Mexico
| | - Paul W Barnes
- Department of Biological Sciences and Environment Program, Loyola University New Orleans, New Orleans, LA, USA
| | | | - Laura S Bruckman
- Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Rosa Busquets
- Chemical and Pharmaceutical Sciences, Kingston University London, Kingston Upon Thames, UK
| | | | - Mark L Hanson
- Department of Environment and Geography, University of Manitoba, Winnipeg, MB, Canada
| | | | - Samuel Hylander
- Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden
| | - Robyn M Lucas
- National Centre for Epidemiology and Population Health, College of Health and Medicine, Australian National University, Canberra, Australia
| | - Roy Mackenzie
- Centro Universitario Cabo de Hornos, Universidad de Magallanes, Puerto Williams, Chile
- Millennium Institute Biodiversity of Antarctic and Subantarctic Ecosystems BASE, Santiago, Chile
- Cape Horn International Center CHIC, Puerto Williams, Chile
| | - Sasha Madronich
- UV-B Monitoring and Research Program, Colorado State University, Fort Collins, CO, USA
| | - Patrick J Neale
- Smithsonian Environmental Research Center, Edgewater, MD, USA
| | - Rachel E Neale
- Population Health Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
- School of Public Health, University of Queensland, Brisbane, Australia
| | - Catherine M Olsen
- Population Health Program, QIMR Berghofer Medical Research Institute, Brisbane, Australia
- Frazer Institute, University of Queensland, Brisbane, Australia
| | - Rachele Ossola
- Department of Chemistry, Colorado State University, Fort Collins, CO, USA
| | | | - Irina Petropavlovskikh
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
- Ozone and Water Vapor Division, NOAA ESRL Global Monitoring Laboratory, Boulder, CO, USA
| | - Laura E Revell
- School of Physical and Chemical Sciences, University of Canterbury, Christchurch, New Zealand
| | - Sharon A Robinson
- Securing Antarctica's Environmental Future, University of Wollongong, Wollongong, Australia
- School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, Australia
| | - T Matthew Robson
- UK National School of Forestry, University of Cumbria, Ambleside Campus, Ambleside, UK
- Organismal & Evolutionary Ecology, Viikki Plant Science Centre, Faculty of Biological & Environmental Sciences, University of Helsinki, Helsinki, Finland
| | - Kevin C Rose
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Keith R Solomon
- School of Environmental Sciences, University of Guelph, Guelph, Canada
| | - Mads P Sulbæk Andersen
- Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA, USA
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
| | - Barbara Sulzberger
- Retired From Eawag: Swiss Federal Institute of Aquatic Science and Technology, Dubendorf, Switzerland
| | - Timothy J Wallington
- Center for Sustainable Systems, School for Environment and Sustainability, University of Michigan, Ann Arbor, MI, USA
| | - Qing-Wei Wang
- Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China
| | - Sten-Åke Wängberg
- Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden
| | | | | | - Richard G Zepp
- ORD/CEMM, US Environmental Protection Agency, Athens, GA, USA
| | - Liping Zhu
- State Key Lab for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, China
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6
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Tuttle E, Wiman C, Muñoz S, Law KL, Stubbins A. Sunlight-Driven Photochemical Removal of Polypropylene Microplastics from Surface Waters Follows Linear Kinetics and Does Not Result in Fragmentation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:5461-5471. [PMID: 38489752 DOI: 10.1021/acs.est.3c07161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/17/2024]
Abstract
Floating microplastics are susceptible to sunlight-driven photodegradation, which can convert plastic carbon to dissolved organic carbon (DOC) and can facilitate microplastic fragmentation by mechanical forces. To understand the photochemical fate of sub-millimeter buoyant plastics, ∼0.6 mm polypropylene microplastics were photodegraded while tracking plastic mass, carbon, and particle size distributions. Plastic mass loss and carbon loss followed linear kinetics. At most time points DOC accumulation accounted for under 50% of the total plastic carbon lost. DOC accumulation followed sigmoidal kinetics, not the exponential kinetics previously reported for shorter irradiations. Thus, we suggest that estimates of plastic lifespan based on exponential DOC accumulation are inaccurate. Instead, linear plastic-C mass and plastic mass loss kinetics should be used, and these methods result in longer estimates of photochemical lifetimes for plastics in surface waters. Scanning electron microscopy revealed that photoirradiation produced two distinct patterns of cracking on the particles. However, size distribution analyses indicated that fragmentation was minimal. Instead, the initial population of microplastics shrank in size during irradiations, indicating photoirradiation in tranquil waters (i.e., without mechanical forcing) dissolved sub-millimeter plastics without fragmentation.
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Affiliation(s)
- Erin Tuttle
- Department of Biological and Physical Sciences, Assumption University, Worcester, Massachusetts 01609, United States
| | - Charlotte Wiman
- Department of Marine and Environmental Science, Northeastern University, Boston, Massachusetts 02115, United States
| | - Samuel Muñoz
- Department of Marine and Environmental Science, Northeastern University, Boston, Massachusetts 02115, United States
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
| | - Kara Lavender Law
- Sea Education Association, Woods Hole, Massachusetts 02540, United States
| | - Aron Stubbins
- Department of Marine and Environmental Science, Northeastern University, Boston, Massachusetts 02115, United States
- Department of Civil and Environmental Engineering, Northeastern University, Boston, Massachusetts 02115, United States
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, Massachusetts 02115, United States
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7
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Brown M, Badzinski TD, Pardoe E, Ehlebracht M, Maurer-Jones MA. UV Light Degradation of Polylactic Acid Kickstarts Enzymatic Hydrolysis. ACS MATERIALS AU 2024; 4:92-98. [PMID: 38221918 PMCID: PMC10786133 DOI: 10.1021/acsmaterialsau.3c00065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 10/12/2023] [Accepted: 10/16/2023] [Indexed: 01/16/2024]
Abstract
Polylactic acid (PLA) and bioplastics alike have a designed degradability to avoid the environmental buildup that petroplastics have created. Yet, this designed biotic-degradation has typically been characterized in ideal conditions. This study seeks to relate the abiotic to the biotic degradation of PLA to accurately represent the degradation pathways bioplastics will encounter, supposing their improper disposal in the environment. Enzymatic hydrolysis was used to study the biodegradation of PLA with varying stages of photoaging. Utilizing a fluorescent tag to follow enzyme hydrolysis, it was determined that increasing the amount of irradiation yielded greater amounts of total enzymatic hydrolysis by proteinase K after 8 h of enzyme incubation. While photoaging of the polymers causes minimal changes in chemistry and increasing amounts of crystallinity, the trends in biotic degradation appear to primarily be driven by photoinduced reduction in molecular weight. The relationship between photoaging and enzyme hydrolysis appears to be independent of enzyme type, though commercial product degradation may be impacted by the presence of additives. Overall, this work reveals the importance of characterizing biodegradation with relevant samples that ultimately can inform optimization of production and disposal.
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Affiliation(s)
- Margaret
H. Brown
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Dr, Duluth, Minnesota 55812, United States
| | - Thomas D. Badzinski
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Dr, Duluth, Minnesota 55812, United States
| | - Elizabeth Pardoe
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Dr, Duluth, Minnesota 55812, United States
| | - Molly Ehlebracht
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Dr, Duluth, Minnesota 55812, United States
| | - Melissa A. Maurer-Jones
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Dr, Duluth, Minnesota 55812, United States
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8
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Tigner JM, Elmer-Dixon MM, Maurer-Jones MA. Quantification of Polymer Surface Degradation Using Fluorescence Spectroscopy. Anal Chem 2023. [PMID: 37326575 DOI: 10.1021/acs.analchem.3c01151] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
One solution to minimizing plastic pollution is to improve reuse and recycling strategies. Recycling, however, is limited by the overall degradation of plastics being used, and current techniques for monitoring this plastic degradation fail to observe this in its early stages, which is key for optimizing reusability. This research seeks to develop an inexpensive, reproducible, and nondestructive technique for monitoring degradation of polyethylene (PE) and polypropylene (PP) materials using Nile red as a fluorescent probe. Changes in Nile red's fluorescence spectra were observed upon exposure to stained, aged PE and PP samples. As the surface hydrophobicity of the plastic decreases, Nile red's fluorescence signal undergoes a corresponding signal shift to longer wavelengths (lower energy). The trends seen in the fluorescent profile were related to more commonly used measurements of plastic degradation, namely, the carbonyl index from infrared spectroscopy and bulk crystallinity from calorimetry. Results demonstrate clear trends in fluorescence spectra shifts as related to the chemical and physical changes to the plastics, with trends dependent on the polymer type but independent of polymer film thickness. The strength of this technique is divided into two defined fits of the fluorescence signal; one fit characterizes the degradation throughout the whole range of degradative oxidation and the other is tailored to provide insight into the early stages of degradation. Overall, this work establishes a characterization tool that assesses the extent of plastics' degradation, which may ultimately impact our ability to recover plastics and minimize plastic waste.
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Affiliation(s)
- Jonathan M Tigner
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Drive, Duluth, Minnesota 55812, United States
| | - Margaret M Elmer-Dixon
- Department of Physics and Astronomy, University of Minnesota Duluth, 1049 University Drive, Duluth, Minnesota 55812, United States
| | - Melissa A Maurer-Jones
- Department of Chemistry and Biochemistry, University of Minnesota Duluth, 1038 University Drive, Duluth, Minnesota 55812, United States
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9
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Lian F, Han Y, Zhang Y, Li J, Sun B, Geng Z, Wang Z, Xing B. Exposure Order to Photoaging and Humic Acids Significantly Modifies the Aggregation and Transformation of Nanoplastics in Aqueous Solutions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:6520-6529. [PMID: 37043333 DOI: 10.1021/acs.est.2c09140] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
The colloidal stability of nanoplastics in aqueous solutions is greatly regulated by photoaging and dissolved organic matter (DOM). However, how the exposure order to sunlight and DOM modifies the environmental behavior of nanoplastics is seldomly determined. Here, with two different exposure orders, we investigated the impact of molecular-weight (MW)-fractionated humic acids (HAs) derived from biochar and the Suwannee River, respectively, on the aggregation of poly(ethylene terephthalate) nanoplastics (PET-NPs) in mono- and divalent electrolyte solutions. For exposure pattern (i) (photoaging followed by HA coating), photoaged PET-NPs had more oxidized surfaces and exhibited 22-320% higher binding affinity to HAs (especially the higher MW fractions) than the pristine counterparts, which greatly improved the dispersion of PET-NPs. For exposure pattern (ii) (HA coating followed by photoaging), HA-PET assemblies were formed, the dispersion of which increased with increasing irradiation time and was significantly higher than that of the samples in the exposure pattern (i) at the end of the experiment. This high dispersion of photoaged HA-PET assemblies was ascribed to the extra oxidation of PET by reactive oxygen species generated in the PET-HA interfaces during photoaging. These findings highlight the "active nature" of HA-PET assemblies, which provide new insight into the reaction of HA with nanoplastics beyond adsorption in the natural environment.
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Affiliation(s)
- Fei Lian
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
| | - Yaru Han
- Institute of Environmental Processes and Pollution Control, and School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China
| | - Yikang Zhang
- Institute of Environmental Processes and Pollution Control, and School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China
| | - Jiaqi Li
- Institute of Environmental Processes and Pollution Control, and School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China
| | - BinBin Sun
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
| | - Zexuan Geng
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China
| | - Zhenyu Wang
- Institute of Environmental Processes and Pollution Control, and School of Environment and Civil Engineering, Jiangnan University, Wuxi 214122, China
| | - Baoshan Xing
- Stockbridge School of Agriculture, University of Massachusetts, Amherst, Massachusetts 01003, United States
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