Previous laboratory studies have demonstrated the potential biotransformation of select perfluoroalkyl acids (PFAA) precursors found in aqueous film-forming foam (AFFF). However, most of these studies have been conducted under oxic conditions using bacteria from activated sludge, pristine soils, and aerobic bacterial enrichment cultures, which may differ from those at AFFF-impacted sites. Therefore, this work aims to demonstrate the potential for PFAA precursor biotransformation, including anaerobic defluorination, under conditions more representative of AFFF-impacted sites using native microbial communities. Two representative fluorotelomer PFAA precursors, 8:2 fluorotelomer alcohol (8:2 FTOH) and 6:2 fluorotelomer sulfonate (6:2 FTS), were selected for study based on prior detection in AFFF formulations. Microcosms were prepared under oxic and anoxic (i.e., nitrate-, sulfate-, and iron-reducing) conditions with surface soils collected from two AFFF-impacted sites, Robins Air Force Base (AFB) and the former Loring AFB. The biotransformation of 8:2 FTOH occurred under all redox conditions, but the rate, extent, and transformation pathways were redox condition specific. For example, under oxic and nitrate-reducing natural attenuation conditions (i.e., without external substrate addition), the 8:2 FTOH half-life was 3 days and 36 days, respectively, whereas under iron- and sulfate- reducing conditions, less than 30% was biotransformed over a +400-day incubation period. Preliminary results of non-targeted PFAS analysis have shown that additional previously undocumented metabolites were formed during the biotransformation of 8:2 FTOH. It is hypothesized that detections of these novel byproducts are a result of differences in the microbial community source from prior studies. The aerobic biotransformation of 6:2 FTS also revealed differences in the two soils/microbial communities tested, with slower transformation in Robins (63.7 mol% 6:2 FTS remained after 224 days) than in Loring (half-life of 43 days and &lt;0.3% remaining after 224 days). Further, for 6:2 FTS, anaerobic biotransformation has not been observed after 266 days of incubation. Collectively, these results improve fundamental understanding of fluorotelomer PFAA precursor biotransformation and the potential attenuation of these chemicals at AFFF-impacted sites, while also highlighting that differences in site microbial communities may impact remediation outcomes.

Biotransformation of 8:2 Fluorotelomer alcohol and 6:2 Fluorotelomer Sulfonate using microbial communities from AFFF-impacted soils </i>

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