Source and fate of ultra-short-chain PFAS in water and biota from an AFFF impacted site

This study adopted and validated a quantitative LC-MS/MS method for the rapid detection of five ultra-short-chain (USC) and three short chain (SC) per - and polyfluoroalkyl substances (PFAS) in diverse environmental matrices. The method was applied to soil from an active fire training site, as well as to freshwater and seawater, at and near Bergen airport, Norway, and was further validated for blue mussels. The total oxidizable precursor assay (TOPA), applied to soil and aqueous film-forming foam (AFFF), provided evidence that AFFF-derived precursors in foam and contaminated soil degrade to USC PFAS, indicating the AFFF as continuing secondary source. USC PFAS concentrations in freshwater ranged from 13 to 725 ng/L, with the highest levels detected at the fire training site. Seawater near the airport contained 10.4–14.9 ng/L, with concentration decreasing offshore. Depth profiling showed USC PFAS to be surface-associated. USC PFAS were also detected in mussels for the first time, both from urban and remote areas, indicating potential for bioaccumulation. This study addresses an important methodological gap by validating and applying a reliable analytical approach for monitoring USC PFAS in complex matrices, thereby supporting advancements in environmental monitoring and regulation. The results reveal AFFF impacted sites as major point sources of USC-/SC-PFAS and highlight their high mobility, persistence, and potential bioaccumulation in mussels. • Broad scope LC-MS/MS method developed and validated for quantitative screening of ultra short chain PFAS with confirmation using LC-HRMS. • Method applied to soil, freshwater, seawater and blue mussels from a hotspot where aqueous film forming foam (AFFF) has been used previously. • Ultra short chain PFAS found to decrease with distance from the hotspot and with depth in the surrounding seawater. • Total oxidizable precursor test demonstrated that the hotspot is a significant source of ultra short chain PFAS through degradation of PFAS precursors.