Colloidal stability and aggregation of polyethylene (PE) nanoplastics under UV weathering and PFOA contamination

, but rapidly aggregate at higher salt concentrations. Environmental modifications have contrasting effects on PE NP stability. The presence of PFOA does not significantly impact the overall colloidal stability, especially at low salt concentrations, but introduces a small additional barrier for aggregation at higher salt concentrations. In contrast, UV weathering promotes particle aggregation. Our findings show that PE NPs can have some colloidal stability even in the absence of stabilizing ligands, likely due to the presence of heterogeneous surface charge caused by ion adsorption. The decrease in stability upon UV weathering is attributed to the formation of free radicals. The findings demonstrate that environmental modifications to PE NPs through pollutant adsorption or photochemical weathering can significantly alter their colloidal stability.