The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) have arouse growing concerning due their widely distribution in environment and adverse health effects to ecosystem and human health. Certain PFAS such as PFOA and PFOS have been listed in POPs and thus subject to global restriction in use and produce, in the meanwhile alternatives have been introduced. Emerging perfluorinated compounds such as perfluorinated ether carboxylic acids (PFECAs) have  been introduced as alternatives for PFOA, and been widely detected in the coastal and marine environment. In this study, 36 PFAS were examined in the surface water of the Bohai Sea, and the constituent concentrations and compositions of these PFAS were analysed, the spatial distributions were investigated, and the quarterly variations of these PFAS were observed. The concentration of PFAS in the surface water of the Bohai Sea ranged from 15.28 ~ 217.30 ng/L (mean 50.23 ± 30.95 ng/L). The proportions of legacy PFAS and emerging PFAS in the Bohai Sea water were 73.7% and 26.3%, respectively. The highest concentration was perfluorooctanoic acid (PFOA), followed by perfluoro-(3,5-dioxahexanoic) acid (PFO2HxA). Laizhou Bay was the most serious  pollution area in the Bohai Sea with quite high concentrations of PFAS. The seasonal distribution showed the highest PFAS level in autumn and the lowest PFAS pollution in summer. The main factors for the low concentration in summer include ocean currents dispersion and rainfall dilution. In the Bohai Sea, the total PFAS concentration has shown an increasing trend and then decreasing trend in recent years, especially for PFOA, with a significant decrease in 2022. However, at the same time, its alternative, PFBA, is showing a rising trend in both concentration and share. This study increases our knowledge of the pollution of novel pollutants in the Bohai Sea region and provides an understanding of the changes in legacy PFAS.