Release kinetics and environmental risks of TCPP from polyurethane foam microplastics: Insights from artificial seawater to natural estuarine water

Tris(1-chloro-2-propyl) phosphate (TCPP) is the predominant organophosphate ester detected in aquatic environments; however, its pollution sources and associated environmental risks remain poorly understood. Polyurethane foam (PUF), a common microplastic contaminant in marine environment, can contain substantial amounts of TCPP and thus potentially threaten aquatic ecosystem. This study investigated the release kinetics and environmental risks of TCPP from PUF microplastics in both artificial seawater and natural water collected from the Pearl River Estuary. Short-term, long-term sustained-release, and cyclic release experiments were conducted, and the resultant data were fitted with Fick's diffusion model, as well as first- and second-order kinetic models. The results revealed that TCPP release is governed primarily by intraparticle diffusion. The release rate was significantly influenced by PUF particle size (larger particles released TCPP faster), water temperature (2.47-fold higher at 25 °C than at 15 °C), and fulvic acid concentration (enhanced release at high concentrations), whereas salinity exerted only a weak inhibitory effect (release rates in freshwater exceeded those in seawater). During cyclic leaching, TCPP release decreased rapidly; concentrations in the final cycle were two orders of magnitude lower than those in the initial cycle. Long-term leaching experiments further indicated a multi-century release potential, with a maximum release half-life of 312 years. These findings highlight the persistent, gradual leaching risk of TCPP and underscore the critical importance of controlling microplastic emissions at the source to mitigate long-term environmental accumulation of the contaminant.