Seawater-Sediment Partitioning, Source Apportionment and Ecological Risk of Organophosphate Esters in the Bohai Sea and Northern Yellow Sea, China

Organophosphate esters OPEs are pervasive emerging pollutants endangering semi-enclosed marine ecosystems under intense anthropogenic stress. In May 2023 we collected surface seawater and sediment samples at 23 stations across the Bohai Sea and Northern Yellow Sea, analyzing 16 OPE congeners via GC-MS to clarify their partitioning characteristics, source profiles and ecological risks. Nine OPEs were detected in seawater with a mean total concentration of 126.08 ng/L, showing a pattern of nearshore enrichment and estuarine hotspots dominated by alkyl and chlorinated congeners. Sediments contained 13 OPEs with a mean total concentration of 169.77 ng/g dry weight, concentrated in industrial and shipping zones with chlorinated OPEs and EHDP as dominant components. OPE seawater-sediment partition coefficients correlated strongly with log Kow ( R 2 =0.72, p<0.01). PCA identified medium-specific sources: seawater OPEs derived from plastic, electronic and rubber industries; sediment OPEs from domestic emissions, flame retardant activities and shipping. Ecological risk assessment showed low seawater OPE risk with TMP reaching an RQ of 0.0089 to Daphnia magna , while sediments had low-to-medium risk with TNBP at an RQ of 0.92 to Phaeodactylum tricornutum and notable composite pollution effects. This study offers scientific support for targeted OPE control in the Bohai Rim and global industrialized semi-enclosed coastal zones.