Aerobic biotransformation of 6:2 fluorotelomer sulfonate in soils from two aqueous film-forming foam (AFFF)-impacted sites.

ABSTRACT

Although 62 fluorotelomer sulfonate (62 FTS) is a common ingredient in aqueous film-forming foam (AFFF) formulations, its environmental fate at AFFF-impacted sites remains poorly understood. This study investigated the biotransformation of 62 FTS in microcosms prepared with soils collected from two AFFF-impacted sites; the former Loring Air Force Base (AFB) and Robins AFB. The half-life of 62 FTS in Loring soil was 43.3 days; while >60 mol% of initially spiked 62 FTS remained in Robins soil microcosms after a 224-day incubation. Differences in initial sulfate concentrations and the depletion of sulfate over the incubation likely contributed to the different 62 FTS biotransformation rates between the two soils. At day 224, stable transformation products, i.e., C4C7 perfluoroalkyl carboxylates, were formed with combined molar yields of 13.8 mol% and 1.2 mol% in Loring and Robins soils, respectively. Based on all detected transformation products, the biotransformation pathways of 62 FTS in the two soils were proposed. Microbial community analysis suggests that Desulfobacterota microorganisms may promote 62 FTS biotransformation via more efficient desulfonation. In addition, species from the genus Sphingomonas, which exhibited higher tolerance to elevated concentrations of 62 FTS and its biotransformation products, are likely to have contributed to 62 FTS biotransformation. This study demonstrates the potential role of biotransformation processes on the fate of 62 FTS at AFFF-impacted sites and highlights the need to characterize site biogeochemical properties for improved assessment of 62 FTS biotransformation behavior.