Occurrence and distribution of per- and polyfluoroalkyl substances (PFASs) in the seawater and sediment of the South China sea coastal region

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are anthropogenic chemicals widely used in industrial and consumer products. PFASs can be readily transported by water due to their relatively high solubility and polarity, and oceans are believed to be their final global sink. The heavily industrialized and urbanized Pearl River Delta in South China represents a major source of PFASs. In the present study, samples of surface waters, bottom waters, and sediments of the South China Sea (SCS) were collected during summer 2017 and 2018 to determine the level, distribution, and potential regional risk of PFASs. The PFAS concentrations in surface seawater, bottom seawater, and sediment were 125-1015 pg/L, 38-779 pg/L, and 7.5-84.2 pg/g dry weight, respectively. Perfluorobutanoic acid (PFBA) and perfluorooctanoic acid (PFOA) were the dominant PFASs in seawater, while perfluorooctanesulfonic acid (PFOS) was dominant in sediment. The PFAS alternatives 6:2 and -8:2 Cl-polyfluorinated ether sulfonate (6:2 and 8:2 Cl-PFESA) as well as hexafluoropropylene oxide dimer (HFPO-DA) were detected in the SCS for the first time. The spatial distribution of PFASs in seawater and sediment were impacted by river outflows and sea currents, and concentrations decreased from the estuaries to the offshore regions due to the dilution effect. PFAS concentrations were relatively low compared to other coastal regions worldwide, and a preliminary environmental hazard assessment showed that PFASs posed minimal risk to marine organisms in the coastal region of the SCS, with the exception of PFOS.