Study On Release Characteristics Of Microplastics Derived Dissolved Organic Matter And Its Physicochemical Fate In Water

Microplastic pollution has become a globally recognized issue,prompting increased attention on the ecological and health risks associated with microplastic-derived pollutants.Microplastic-derived dissolved organic matter(MP-DOM)is a significant pollutant,but its environmental release characteristics and natural transformation have not been systematically studied.Based on the whole process of pollutant release and elimination,this study analyzed the characteristics of MP-DOM in water bodies in typical plastic aggregation industrial areas,utilized automatic machine learning to explore the main controlling factors for the environmental release of MP-DOM,and examined the impacts of photo-thermal,mineral adsorption,and photo-mineral coupled systems on the natural elimination of MP-DOM in the environment.Conclusions and insights were drawn accordingly.(1)During the complete process of plastic production wastewater discharge,the composition and fate of dissolved organic matter(DOM)are complex,with MP-DOM having a significant contribution to wastewater DOM.Sewage treatment plants achieve a removal rate of 57.46-80.14%for dissolved organic carbon(DOC),while the removal rate of aromatic substances is only 62.22%.The proportion of MP-DOM in production wastewater DOM ranges from 12.3%to 62.6%,and the degradation of MP-DOM in sewage treatment plants is inadequate,which can result in MP-DOM entering water bodies surrounding the industrial park via wastewater discharge.(2)Automated machine learning can be applied to simulate and predict MP-DOM release in complex environmental systems.In this study,the optimal condition model had an evaluation index R~2 of 0.99 and RMSE of 1.22 for the testing set,indicating highly accurate predictions(slope=1.0)of MP-DOM release.The variable importance ranking of the 10 factors was MP type(1.00)>release time(0.97)>>UV pre-aging(0.37)>MP size(0.1)>other(≤0.1).MP type was found to be the key factor determining MP-DOM release,while UV aging and MP particle size were important promoting factors for MP-DOM release.(3)MP-DOM exhibits stability to some extent,making it difficult to remove from aquatic environments using single external factors such as hydrolysis,photolysis,or iron-manganese minerals.Light-mineral coupling systems alter the release-elimination dynamic equilibrium of MP-DOM and affect the change in MP-DOM surface abundance.Specifically,hematite,siderite,and hydroxylated iron oxide-light coupling systems can reduce the apparent abundance of PVC-DOM,with an apparent degradation half-life of 289-495 hours and a net degradation half-life of173-462 hours.The apparent abundance of PBAT-DOM in mineral-light coupling systems,except for hydroxylated iron oxide,showed an increasing trend,while a net degradation half-life was calculated as 203-690 hours.This research presents a comprehensive study of the environmental migration and transformation regulations of MP-DOM,and extensively examines the environmental occurrence state of MP-DOM.Through automatic machine learning,the release characteristics of MP-DOM under complex driving factors were realized,and the leading factors that affect MP-DOM releasing were determined.The contribution of common environmental factors such as photo-thermo,mineral adsorption,and photo-mineral coupling to the non-biological natural decay of MP-DOM was explored.This research has significant implications for the evaluation of the environmental abundance and risk of MP-DOM.