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Decoding microplastic pollution in China freshwater: interpretable machine learning insights into composition-specific distribution and associated phthalate ester leaching risk
Summary
Scientists analyzed nearly a decade of data from over 800 Chinese rivers and lakes to map out different types of plastic pollution and predict where they're likely to leak a harmful chemical additive called DEHP, which is used to make plastics flexible. They found that weather patterns like rainfall and temperature help predict where certain plastics show up, and that some river regions face a real risk of this chemical leaching into the water at concerning levels. Since these waterways are sources of drinking water and food (like fish), understanding where plastic pollution and its toxic chemicals concentrate can help target cleanup efforts and protect public health.
Microplastics (MPs) pollution in freshwater ecosystems, combined with the leaching of toxic additives such as phthalate esters (PAEs), poses a pervasive and escalating threat to aquatic environmental health. As the top plastic producer/consumer, China exhibits widespread MP pollution, yet national-scale, composition-specific analyses of MP distribution and the associated PAE leaching risks remain limited. This study established a comprehensive dataset from 846 sampling sites (523 rivers, 323 lakes) across China (2014-2024), with MP sizes unified to 20-5000 μm. An interpretable multi-output multilayer perceptron (MLP) model was developed to simultaneously map spatial distribution of five dominant MPs (polyethylene [PE], polypropylene [PP], polyethylene terephthalate [PET], polyvinyl chloride [PVC], and polystyrene [PS]). Although the MLP exhibited a slightly lower average R (0.61) relative to random forest (0.69) and XGBoost (0.68), its shared‑parameter architecture retains inherent co‑occurrence patterns across MP compositions. Independent validation confirmed model robustness and generalizability. Shapley additive explanation analysis highlighted key associated factors: precipitation was closely linked to PVC, and PET in rivers, while, temperature was correlated with PE and PP in lakes. National risk assessment of composition-specific PAE leaching identified di(2-ethylhexyl) phthalate (DEHP) as the primary concern. Under average leaching scenarios, low ecological risks were observed in rivers of Beijing, Tianjin, Taiwan and southeastern coastal regions as well as southern lakes; under maximum leaching scenarios, risks escalated to medium levels in focal river regions. This study provides the national-scale quantification of composition-specific MP distribution and PAE leaching risks, offering a transferable framework for targeted pollution management and policy formulation.