Seasonal Contrast in Oceanic Regulation of Traditional and Emerging Per- and Polyfluoroalkyl Substances in the Coastal East China Sea

Traditional and emerging per- and polyfluoroalkyl substances
(PFAS)
are widespread in coastal environments influenced by intense anthropogenic
activity. However, their spatiotemporal dynamics in response to seasonal
oceanographic processes remains insufficiently understood. By integrating
basic hydrological and biogeochemical data, this study systematically
compares the occurrence and behavior of traditional and emerging PFAS
in full-depth seawater and surface sediments across the coastal East
China Sea (ECS) during summer and winter. Waterborne PFAS consistently
exhibited nearshore-to-offshore decreasing gradients and surface enrichment
in both seasons, highlighting persistent terrestrial inputs. Notably,
summer concentrations were generally lower, with weaker negative correlations
with salinity, likely due to enhanced freshwater discharge during
the wet season, which diluted and dispersed PFAS more effectively.
Seasonal reversal of coastal currents driven by the monsoon further
modulated the contaminant transport pathways. In contrast, sediment
PFAS concentrations were generally higher in the summer, which can
be attributed to stronger vertical mixing in the winter that facilitates
the remobilization of contaminants. Enhanced sediment resuspension
during the winter also promoted greater partitioning of PFAS, especially
hydrophilic short-chain compounds, into the aqueous phase. These findings
offer valuable insights into the seasonal variability and environmental
behavior of PFAS in coastal marine systems.