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Molecular interaction of pristine and photoaged polylactic acid microplastics with extracellular polymeric substances from Microcystis aeruginosa
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Researchers investigated how pristine and UV-aged polylactic acid microplastics interact with extracellular polymeric substances produced by the cyanobacterium Microcystis aeruginosa. They found that aging enhanced the interaction between the microplastics and these biological substances, primarily through hydrogen bonding, leading to greater surface changes and molecular weight reduction. The study suggests that aged biodegradable microplastics may be more susceptible to transformation in aquatic environments than pristine ones.
Microplastics (MPs) existence in aquatic environments may cause changes in properties of water bodies and associated sediments. In freshwater systems, most of the photosynthetic products of phytoplankton are released in the form of extracellular polymeric substances (EPS). EPS often interact with some charged particles through specific functional groups in their macromolecules. An in-depth understanding of EPS-MPs interactions is essential to assess the environmental effects of MPs on freshwater and marine systems. In this study, the mechanism behind the interactions of pristine and photoaged polylactic acid microplastics (PLA-MPs) with EPS was systematically investigated at the molecular scale. Results show that the addition of EPS remarkably enhanced the fluorescence intensity of humic- and fulvic-like substances within pristine and aged PLA as revealed by fluorescence excitation-emission matrix. Fourier transform infrared spectroscopy, Raman spectra, and atomic force microscopy coupled with infrared spectroscopy (AFM-IR) further demonstrated that interactions between EPS and pristine PLA were mainly via hydrogen bonding-induced local chain rearrangement or breakage. Meanwhile, aging of PLA led to the stronger interaction with EPS. Compared with pristine PLA, aged PLA exhibited more pronounced surface alteration and molecular weight reduction after exposure to EPS under the applied experimental conditions, suggesting a greater susceptibility to hydrolytic transformation. Moreover, the aged PLA displayed pronounced cracks and grooves, especially after reaction with EPS. EPS addition also increased the negative surface charge of PLA, especially in aged PLA. This study highlights the complexity of PLA-EPS interaction mechanisms, and offers a possible view on predicting the environmental behavior of MPs and regulating their biodegradation process.
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Researchers studied how different types of UV-simulated aging affect the ability of polylactic acid microplastics to adsorb and release bisphenol A. The study found that aging conditions changed the surface properties of the biodegradable plastic, altering its interaction with this common environmental contaminant. The findings suggest that even biodegradable microplastics can act as carriers of harmful chemicals depending on their degradation state.
Aging behavior of biodegradable polylactic acid microplastics accelerated by UV/H2O2 processes
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Researchers used UV and hydrogen peroxide to simulate environmental aging of biodegradable polylactic acid (PLA) microplastics, finding that PLA microplastics undergo significant surface and structural changes during weathering that alter their environmental behavior and persistence.
Acute Toxicity Effects of Aged Polyethylene and Polylactic Acid Microplastics on Microcystis aeruginosa: Growth and Oxidative Stress Response
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Researchers compared the acute toxicity of aged polyethylene (conventional plastic) and polylactic acid (biodegradable plastic) microplastics on the cyanobacterium Microcystis aeruginosa. Aged PLA microplastics inhibited algal growth more than aged PE, and UV-aged particles were more toxic than heat-aged ones for both plastic types. The study suggests that biodegradable plastics may not be less harmful than conventional plastics once they begin degrading in the environment.
Change in adsorption behavior of aquatic humic substances on microplastic through biotic and abiotic aging processes
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Researchers found that both UV irradiation and microbial aging of polyethylene microplastics significantly altered their surface chemistry, changing how aquatic humic substances adsorb onto the plastic surface and highlighting the importance of weathering state in assessing microplastic-contaminant interactions.
Probing the molecular interaction between photoaged polystyrene microplastics and fulvic acid
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Researchers investigated how photoaged polystyrene microplastics interact with fulvic acid, a common natural organic compound found in water environments. Using advanced spectroscopy techniques, they found that aging changed the surface chemistry of the microplastics and altered how they bind to fulvic acid at the molecular level. The study suggests that weathering processes in the environment may significantly change how microplastics interact with and transport other dissolved substances in water.
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