Photoaging of nanoplastics (NPs) and heteroaggregate with suspended sediments (SS) determines transport processes and ecological risks of NPs in aquatic environments. This study investigated the disruption of photoaging on the heteroaggregation behavior of polystyrene NPs (PSNPs) and SS in different valence electrolyte solutions and deduced the interaction mechanisms by integrating aggregation kinetics and molecular dynamics (MD) simulation. Increasing the electrolyte concentration significantly enhanced the heteroaggregation between PSNPs and SS, and the divalent electrolytes induced the heteroaggregation more efficiently. MD simulation at the molecular level revealed that PS and SS could spontaneously form clusters, and photoaged PS has a stronger potential to fold into a dense state with SS. Photoaging for 30 d retarded heteroaggregation due to the steric hindrance produced by the leached organic matter in NaCl solutions, and the critical coagulation concentration (CCC) increased by more than 85.44%. Contrarily, photoaging caused more oxygen-containing functional groups produced on the surface of PSNPs through Ca²⁺ bridging promoting heteroaggregation and thus destabilizing in CaCl₂ solutions, the CCC decreased by 23.53% ∼ 35.29%. These findings provide mechanistic insight into the environmental process of NPs and SS and are crucial for a comprehensive understanding of the environmental fate and transport of NPs in aquatic environments.

中文翻译：

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光老化诱导的水生环境中纳米塑料和悬浮沉积物异质聚集的变化：纳米聚苯乙烯的案例研究


纳米塑料 （NPs） 和异质聚集体与悬浮沉积物 （SS） 的光老化决定了 NPs 在水生环境中的运输过程和生态风险。本研究研究了光老化对聚苯乙烯 NPs （PSNP） 和 SS 在不同价电解质溶液中的异质聚集行为的破坏，并通过整合聚集动力学和分子动力学 （MD） 模拟推导出相互作用机制。提高电解质浓度显著增强了 PSNPs 和 SS 之间的异质聚集，二价电解质更有效地诱导了异质聚集。分子水平的 MD 模拟显示，PS 和 SS 可以自发形成簇，并且光老化的 PS 具有更强与 SS 折叠成致密态的可能性。由于 NaCl 溶液中浸出有机物产生的空间位阻，光老化 30 d 延迟了异质聚集，临界凝血浓度 （CCC） 增加了 85.44% 以上。相反，光老化导致 Ca²⁺ 桥接在 PSNPs 表面产生更多的含氧官能团，促进异质聚集，从而在 CaCl₂ 溶液中不稳定，CCC 降低 23.53% ∼ 35.29%。这些发现为了解 NPs 和 SS 的环境过程提供了机制见解，对于全面了解 NPs 在水生环境中的环境归宿和运输至关重要。