Sedimentation behavior of aggregated microplastics: Influence of particle size and water constituents in environmental waters

作者：Zhijian Ding, Hao Wang, Sili Chen, Yao Chen, Yingchun Liu, Xiaoli Zhao · 发表于：The Science of The Total Environment · 年份：2025 · DOI：10.1016/j.scitotenv.2025.180931 · 被引用次数：5 · 研究领域：Microplastics and Plastic Pollution、biodegradable polymer synthesis and properties、Marine Biology and Environmental Chemistry

Understanding the aggregation and settling behaviors of micro/nanoplastics (M/NPs) is essential for predicting their transport and fate in aquatic environments. However, gaps remain in comprehending how particle size and common environmental water constituents jointly influence M/NPs aggregation and sedimentation. This study investigated the effects of metal cations (Na + and Ca 2+ ) and humic acid (HA) on polystyrene particles of 100 nm (PS-100) and 500 nm (PS-500). The resulted indicated that larger PS-500 particles exhibited lower critical coagulation concentration (CCC) and a stronger tendency to aggregate, yet remained suspended even after aggregation (“aggregation without settling”) due to their larger secondary energy minima, lower ion adsorption, and a lower density relative to water. In contrast, smaller PS-100 particles displayed a two-stage behavior of “settling following by floating”, driven by stronger ion adsorption that increased their relative density and induced sedimentation (“settling without aggregation”). HA modified these processes differently in Na + and Ca 2+ systems: it increased CCC in Na + solutions by enhancing electrostatic repulsion, but CCC in Ca 2+ solutions through Ca 2+ –HA complexation and bridging effects. DLVO analysis confirmed that particle size and ion valence jointly controlled energy barriers and secondary minima, determining aggregate stability. Environmental water experiments further revealed that dissolved organic matter (DOM) comp...