Fate and Transformation of 15 Classes of Per- and\nPolyfluoroalkyl Substances in Aqueous Film-Forming Foam (AFFF)-Amended\nSoil Microcosms

The environmental fate of per- and\npolyfluoroalkyl substances (PFAS)\nin aqueous film-forming foams (AFFFs), especially those synthesized\nby electrochemical fluorination (ECF) processes, remains largely unknown.\nThis study evaluated the transformation of AFFF-derived ECF-based\nprecursors in aerobic soil microcosms amended with a historically\nused AFFF formulation (3M Light Water<sup>TM</sup>). Fifteen classes\nof PFAS, including AFFF components and transformation products, were\nidentified or tentatively identified by suspect screening/nontargeted\nanalysis (SSA/NTA) throughout a 308-day incubation. This study demonstrates\nthat AFFF-derived ECF-based precursors serve as sources of perfluoroalkane\nsulfonamides (FASAs) and perfluoroalkyl acids (PFAAs), which are commonly\ndetected at AFFF-impacted sites. Temporal sampling provided evidence\nfor biotransformation of multiple precursors including tri- or dimethyl\nammonio propyl perfluoroalkane sulfonamides. Additionally, the environmental\nstability (i.e., resistance to transformation) of ECF-based precursors\nwas found to depend upon structural characteristics, including perfluoroalkyl\nchain length, presence of sulfonamide or carboxamide groups, and functional\ngroups (e.g., a branch of carboxyalkyl group) attached to the nitrogen\natoms. These findings provide insights into the transformation pathways\nof AFFF-derived PFAS and other structurally similar ECF-based PFAS,\nwhich will support the management and remediation of PFAS contamination\nat legacy AFFF-impacted sites.