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Advancing understanding of microplastics-derived dissolved organic matter release: From source-dependent behavior to micro-interfacial processes
Summary
Researchers compared dissolved organic matter released by microplastics from river-collected versus newly purchased plastics under UV aging, finding that environmentally pre-aged plastics released chemically more oxidized DOM while fresh plastics preferentially shed higher-molecular-weight, aromatic humic-like compounds — with salinity amplifying these source-dependent differences in seawater conditions.
The release of microplastics-derived dissolved organic matter (MPs-DOM) during MPs aging poses increasing environmental concern, yet source-dependent release behaviors of environmentally relevant MPs remain poorly understood. Here, we conducted a comparative investigation of MPs-DOM release from MPs prepared from river-collected plastics and newly purchased products under UV-induced aging conditions, focusing on two widely used commercial plastic types: polyethylene terephthalate (PET) from beverage bottle and expandable polystyrene (PS) from foam boxes. The results showed that, under identical aging conditions, MPs derived from river-collected plastics exhibited a higher degree of aging, whereas MPs derived from newly purchased plastics released more DOM. Upon aging, MPs-DOM from both river-collected and newly purchased plastics exhibited a consistent compositional evolution toward increased oxygenation, aromaticity, and molecular complexity. Notably, MPs prepared from newly purchased products preferentially released DOM enriched in high-molecular-weight, aromatic, and humic-like components, whereas river-collected plastics released DOM that was chemically more oxidized, structurally reorganized, and more responsive to redox transformation during photoaging. These contrasting behaviors highlight the lasting influence of prior environmental exposure on MPs aging and DOM release characteristics. Furthermore, simulated seawater conditions amplified these source-dependent differences, with salinity enhancing the preferential release of aromatic DOM from newly purchased MPs relative to river-collected MPs. Molecular dynamics simulations revealed that MPs-DOM release is governed by the combined effects of MPs-DOM interaction energy, MPs-water affinity, and DOM diffusion properties, with low-molecular-weight DOM exhibiting higher release propensity and repeated release-re-adsorption behavior. Overall, this study demonstrates that MPs-DOM release is strongly controlled by plastic source history and environmental conditions, providing molecular-level insights into the mechanisms governing MPs-DOM release and its environmental fate across aquatic systems.