Unveiling the occurrence and ecological risks of organophosphate esters in seawater of the northern South China Sea

As a class of emerging contaminants in marine environments, organophosphate esters (OPEs) have attracted increasing attention of environmental scientists and policymakers due to their ubiquity and ecotoxicity. However, little is known about the environmental geochemical behaviors of OPEs in seawater of the South China Sea (SCS). In this study, the concentration, composition, pollution source, and ecological risk of twelve typical OPEs were analyzed in the surface seawater of the northern SCS between August and September 2021. The results showed that five out of twelve OPEs were detectable with the total concentration of five OPEs (Sigma 5OPEs) ranging from 7.17 to 67.6 ng/L in seawater. Chlorinated OPEs (Cl-OPEs) were the predominant OPEs, with a mean concentration of 18.4 ng/L, accounting for more than 69.8% of Sigma 5OPEs. Among the detected congeners, tris(2-chloroethyl) phosphate (TCEP) was the most abundant OPE (mean: 14.8 ng/L, 56.2 %), followed by triethyl phosphate (TEP) (mean: 7.75 ng/L, 29.5%) and tris(1-chloro-2-propyl) phosphate (TCIPP) (mean: 2.07 ng/L, 7.87 %). Principal component analysis and Spearman correlation analysis indicated that terrestrial inputs, atmospheric deposition, and shipping activities were the potential sources of OPEs in the northern SCS. The ecological risk assessment revealed that TCEP posed low threats to algae and low ecological risks were predominantly observed from the mixture of OPEs. This work provides a basis for further investigation into the environmental behavior, toxicity, and risk of OPEs in the SCS and facilitates a better implementation of effective management actions.