Biogeochemical impact on the distribution variations of organophosphorus flame retardants in estuarine area and insight into climate change

This study investigated the biogeochemical dynamics influencing the distribution of organophosphorus flame retardants (OPFRs) from the Changjiang Estuary to the adjacent East China Sea, a region characterized by pronounced physicochemical gradients. Twelve out of thirteen OPFR congeners, including traditional and emerging OPFRs, were detected in sediments and seawater samples. Tris(2-chloroethyl) phosphate (TCEP) and tris(2-chloroisopropyl) phosphate (TCIPP) were the dominant congeners. Intensive relationships emerged between OPFR concentrations and biogeochemical parameters. Turbidity maximum zone (TMZ) was identified as a critical hotspot for OPFR pollution. Elevated OPFR levels in nutrient-rich upwelling and offshore regions suggest linkages to biological processes and potential ecological impacts. Furthermore, OPFR concentrations in seawater displayed inverse correlations with tidal fluctuations, highlighting hydrodynamic influences on contaminant dispersal. Based on the relationship between biogeochemical parameters and OPFR concentrations, a Random Forest (RF) model was developed to project OPFR concentrations for the year 2100 under a high-emission climate-change scenario (RCP 8.5). The prediction results were marginally lower compared to current conditions, and temperature emerged as the most significant driver of future OPFRs changes. Notably, emerging OPFRs presented comparable ecological risk to traditional OPFRs, which should be a concern in future regulations.