PFAS hotspots in Swedish offshore sediments: Regional patterns and sorption dynamics

Elevated concentrations of per- and polyfluoroalkyl substances (PFAS) were detected in Swedish offshore sediments, particularly in the Gulf of Bothnia, a region not typically associated with high pollution loads. We investigated PFAS distribution and sorption behaviour in sediments from five sub-basins: Bothnian Bay, Bothnian Sea, Baltic Proper, Southern Baltic, and North Sea. PFAS levels were highest in the northern basins, with ∑PFAS reaching 27 μg kg^-1 dry weight. Composition patterns varied, with perfluoroalkyl carboxylates dominating in the north and sulfonates more prominent in the south, including perfluorohexanesulfonic acid (PFHxS)-enriched signatures in the Baltic Proper. Sorption experiments showed no stronger affinity in northern sediments; instead, organic carbon content explained most partitioning variability. These results indicate that elevated northern PFAS levels are source-driven rather than controlled by sediment properties. Offshore sediments thus represent important PFAS reservoirs, underscoring the need for region-specific monitoring, source control, and integration of sorption dynamics into marine pollutant assessments.