Polyvinyl chloride microplastic derived dissolved organic matter: A dual-function matrix governing antibiotic sequestration and photochemistry

Dissolved organic matter leached from microplastics (MP-DOM) modulates the fate of co-occurring micropollutants, yet its reactivity and ecological implications remain poorly understood. Antibiotics are of particular concern, as their persistence drives antimicrobial resistance, a growing threat to aquatic and human health. This study investigates the dual-function role of DOM leached from polyvinyl chloride -derived (PVC-DOM) in regulating the sequestration, transformation, and toxicity of seven representative antibiotics. Under dark conditions, PVC-DOM sequestered 28.53% of the initial antibiotic mass, nearly three times more than solid PVC particles (10.12%), through hydrogen bonding and π-π interactions. Under sunlight, PVC-DOM enhanced antibiotic photodegradation (up to 88.86%), with ³DOM* as the dominant contributor. Spectroscopy analysis revealed a staged, non-monotonic response: initial complexation, concurrent photochemical attack, and complex destabilization. Molecular characterization identified oxidized, condensed aromatic, and chlorinated compounds, enriched in carboxylated and oxygen-rich functional groups, as key drivers. Toxicity to Microcystis aeruginosa was more severe under sunlight (40.0% growth inhibition, 94.7% chlorophyll loss) than in darkness (71.1% growth inhibition, 84.1% chlorophyll loss), indicating that phototransformation products may amplify ecological risk. Non-target screening tentatively identified interactions products, with in silico predictions confirming their toxicity. These findings demonstrate that MP-DOM acts as a dynamic biogeochemical agent controlling micropollutant sequestration, photochemical transformation, and ecological risk, emphasizing the need to incorporate its reactivity into environmental risk assessments.