Interfacial processes govern the differential release of dibutyl phthalate (DBP) and bisphenol A (BPA) from microplastics under dam-induced water-sediment changes: A combined kinetic and ecological perspective

Dam construction significantly alters hydrological and sediment regimes, creating novel environmental contexts for the fate of emerging contaminants. However, the release mechanisms of plastic-associated compounds from microplastics under these engineered water-sediment conditions remain poorly quantified. This study systematically investigated the release of DBP, a typical phthalate plasticizer, and BPA, a bisphenol-type plastic-associated compound, from polyvinyl chloride (PVC) microplastics in response to key water-sediment parameters. We found that the release is synergistically regulated by flow velocity, sediment content, and particle gradation. Notably, sediment surface potential selectively promoted the release of polar BPA through electrostatic interactions, while exerting a negligible effect on non-polar DBP. Random forest modeling further validated their distinct control mechanisms: hydrodynamic-driven release for DBP versus electrostatic interaction-dominated release for BPA. Ecologically, the released DBP and BPA inhibited biofilm growth but shifted community function toward degradation, although this stress was buffered in natural river water. Collectively, our findings reveal the multidimensional regulation of DBP and BPA release by water-sediment factors and provide a mechanistic basis for assessing the environmental risks of microplastic-associated organic contaminants in dammed rivers.