Source Apportionment of Perfluoroalkyl sSubstances in Sediments of the Western Arctic and Bering Sea: Implications for Transport Pathway and Wildlife Exposure

Although perfluoroalkyl substances (PFASs) are ubiquitous in the arctic environment, the dominant pathways of PFASs to the arctic remain unsettled-main controversy exit between direct oceanic transport supported by global models versus atmospheric oxidation of volatile precursors supported by temporal PFAS variations in arctic biota. Distributions of PFASs in sediments, which act as important sink for seawater and potential source to benthic food web, are important for interpreting the fate of PFASs in the arctic. Here we investigated the spatial and temporal trends of 9 PFASs in 29 surface and one core sediments in the Bering Sea and Chukchi Sea. PFAS concentrations in surface sediments ranged from 0.06-1.73 ng/g (mean 0.55 ng/g), with the highest levels observed in the Bering shelf and Chukchi slope. Spatial variations of PFNA and PFBS showed negative and positive correlations with clay content, and total organic carbon and total nitrogen ratios (C/N). The temporal variations of total PFASs largely conformed to the estimated global release of PFCAs, indicating the arctic as aggregated sink on a global basis. The same profiles and historical variations of PFASs in sediment and arctic biota implied that sediment might act as important reservoir and source to arctic food web. The emission sources and transport pathways were assigned and quantified by PMF model, which showed the major sources of PFASs in Arctic surface sediments were atmospheric oxidation of consumer use of POSF product (27.1.7%, mainly PFOS), oceanic transport of fluoropolymer manufacture of PCDF (42.8%, mainly PFNA) and terrestrial input of aqueous fire-fighting foams (30.1%, mainly PFBS and PFOS). In the past 20 years, atmospheric deposition played a predominant role of PFAS transport (45.0%), but oceanic transport showed growing importance gradually. The potential possibility of sediment as direct PFAS source to arctic biota and its different transport pathways from seawater, to large extent, explained the controversy between modeled results and biota monitoring.