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Photoaging-induced variations in heteroaggregation of nanoplastics and suspended sediments in aquatic environments: A case study on nanopolystyrene
Summary
Researchers investigated how photoaging affects the aggregation behavior of polystyrene nanoplastics with suspended sediments in water. They found that 30 days of photoaging retarded aggregation in sodium chloride solutions due to steric hindrance from leached organic matter, but promoted aggregation in calcium chloride solutions through calcium bridging of newly formed oxygen-containing surface groups. The study provides mechanistic insights into how environmental weathering changes the transport and fate of nanoplastics in aquatic systems.
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 >85.44 %. Contrarily, photoaging caused more oxygen-containing functional groups produced on the surface of PSNPs through Ca bridging promoting heteroaggregation and thus destabilizing in CaCl 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.