Beyond targeted PFAS: contamination patterns and trophic dynamics in an estuarine food web.

Over the past decade, emerging per- and polyfluoroalkyl substances (PFAS) have been increasingly reported in aquatic environments. Still, the environmental behavior of numerous emerging PFAS remains poorly understood. This study investigated trophic dynamics and contamination patterns of both legacy and emerging PFAS revealed by HRMS, in the food web of common sole (benthic) and European sea bass (demersal). Overall, 14 estuarine species collected in the Seine Estuary (France) were studied, including zooplankton, polychaetes, shellfish, crustaceans and fish. Through suspect screening, 92 PFAS belonging to 31 classes were detected, several of which were found in all samples (e.g., FHxSA and 6:2 FTSAm), and further (semi-)quantified using an innovative similarity-based approach. 6:2 FTAB was identified as one of the most abundant compounds in all samples, with concentrations up to five times higher (62 ng/g wet weight (ww)) than the highest PFOS concentration (12 ng/g ww). Contamination profiles appeared to be influenced by habitat, trophic level and metabolic capacities. An influence of habitat was evidenced, with benthic organisms being mainly contaminated by long-head precursors (e.g., X:2 FTAB and X:2 FTSA-HOPrS), and pelagic organisms primarily by short-head precursors (FASA and X:3 FTCA), PFCA and PFSA. Across the food web, concentrations of long-head precursors tended to decrease with trophic level, while concentrations of short-head precursors, PFCA and PFSA tended to increase, suggesting a biotransformation of long-head precursors in the organisms of higher trophic levels. Finally, fish species showed relatively lower levels of long-head precursors, strengthening the hypothesis of biotransformation processes by the liver.