Sequential leaching dynamics of dissolved organic matter from microplastics: Implications for trihalomethane formation and microbial growth potential

초록

Despite extensive studies on the release behavior of microplastics-derived dissolved organic matter (MP-DOM) under continuous leaching, limited attention has been paid to the sequential leaching dynamics that better simulate realistic environmental conditions. Here, four types of microplastics-polylactic acid (PLA), polyethylene (PE), polystyrene (PS), and commercial PS (CPS)-were subjected to four sequential extractions under dark and UV irradiation conditions to investigate the evolving characteristics of MP-DOM across different leaching phases. Two important aspects of MP-DOM reactivity were examined: trihalomethane formation potential (THMFP) and microbial growth potential . Bio-based PLA exhibited the highest dissolved organic carbon (DOC) release and the fastest leaching rate, while petroleum-based MPs (PE, PS, CPS) showed progressively increasing DOC release under prolonged UV exposure. Phenol/protein-like substances dominated the MP-DOM across all MPs, but their evolution varied by polymer type and leaching condition. Under UV irradiation, PSDOM exhibited a gradual decline in protein-like components and an increase in aromaticity and humification, whereas PLA-, PE-, and CPS-DOM showed opposite trends. THM precursor leaching was more pronounced than DOC leaching under UV irradiation, with simple aromatic phenol/protein-like substances serving as the major precursors. Principal component analysis further revealed that PLA-DOM was characterized by higher lability and lower THMFP, while petroleum-based MP-DOMs exhibited higher THMFP and reduced microbial activity over time. Overall, this study highlights the dynamic compositional changes of MP-DOM during sequential leaching and their implications for disinfection by-product formation and microbial ecosystem function. These findings provide new insights into the environmental behavior of MP-DOM, emphasizing the need for timeresolved assessments of MP-water interactions.

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