Traditional and Emerging Per- and Polyfluoroalkyl Substances in the Amundsen Sea Polynya, Antarctica: Physical and Biogeochemical Drivers

Antarctic polynyas serve as natural laboratories for investigating the complex atmosphere-ocean-ice interactions and potential ecological risks of per- and polyfluoroalkyl substances (PFAS) in remote polar environments. This study presents the first comprehensive assessment of traditional and emerging PFAS in the Amundsen Sea Polynya (ASP) during the austral summer (December 2023 to January 2024), integrating their occurrence in seawater and biological samples with key hydrographic and biogeochemical parameters. Short-chain compounds, such as perfluorobutanoic acid (PFBA), exhibited nearshore enrichment driven by atmospheric deposition followed by summertime meltwater release. Continuous sea-ice formation and brine rejection within the ASP further promoted the expulsion of PFBA with brine and its accumulation in the underlying Winter Water layer. In contrast, long-chain compounds, particularly 6:2 fluorotelomer sulfonic acid (6:2 FTSA), were preferentially incorporated into sea ice and advected toward the ASP margin─typically the marginal ice zone (MIZ)─by strong offshore winds. Their subsequent release during late-summer melting, coincident with elevated colored dissolved organic matter (CDOM), resulted in enhanced 6:2 FTSA concentrations throughout the MIZ water column, possibly modulated by both microbial transformation and particle adsorption-settling processes. High bioaccumulation and biomagnification of 6:2 FTSA in Antarctic krill and Adélie penguins highlight its ecological risk to the Antarctic marine ecosystem. Furthermore, PFBA detection in Circumpolar Deep Water (CDW) suggests potential interbasin transport via the Meridional Overturning Circulation (MOC), implying that global mid- and deep-ocean waters may serve as a long-term reservoir for PFAS.