Comprehensive Assessment of Per- and Polyfluoroalkyl Substances (PFAS) Pollution in a Coastal Region: Contributions from Nearshore and Offshore Sources

Per- and polyfluoroalkyl substances (PFAS) have become a well-known class of anthropogenic pollutants in coastal regions. It is known that PFAS primarily enter the sea from nearshore sources, dry deposition, and wet deposition. However, the contribution of offshore sources to PFAS pollution in the sea remains poorly understood. Our study aims to investigate the occurrence of 74 PFAS across 15 groups in a coastal region of eastern China and to characterize their spatial distribution by focusing on the critical roles of both nearshore and offshore sources. Results revealed that 26 PFAS were detected in the coastal region (i.e., Ou River and Wenzhou Bay), with detection frequencies ranging from 4.3% to 100.0%. Notably, over 10 PFAS were detected for the first time in the region, such as perfluorooctane sulfonamide (FOSA), hexafluoropropylene oxide dimer acid (HFPO-DA), and 6:2 fluorotelomer sulfonic acid (6:2 FTSA), among others. The concentrations of detected PFAS ranged from 0.0018 to 76.31 ng/L, with perfluorooctanoic acid (PFOA) as the dominant congener. Spatial analysis indicated that the nearshore area was more severely polluted compared to the offshore area, with specific hotspots identified near industrialized areas. However, the distribution of certain PFAS, such as perfluorobutane sulfonic acid (PFBS) and perfluoro-3,6-dioxaheptanoic acid (PFDHA), exhibited a contrasting pattern, with higher concentrations observed in the offshore area and near island perimeters. These findings suggest that PFAS pollution in Wenzhou Bay originates from both nearshore and offshore sources, highlighting a complex interplay between nearshore and island-related activities.