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Polyvinyl chloride microplastic derived dissolved organic matter: A dual-function matrix governing antibiotic sequestration and photochemistry
Summary
When PVC plastic breaks down in water, it releases dissolved substances that can trap antibiotics or, under sunlight, break them apart into new byproducts—but these breakdown products can actually be more toxic to aquatic algae than the original antibiotics. This matters because it shows microplastics aren't just passive pollution; they actively change how antibiotics behave in the environment, potentially creating new toxic chemicals and influencing the spread of antibiotic-resistant bacteria that can affect drinking water and food sources.
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.