What is the biotransformation of 1H,1H,2H,2H-perfluorooctanesulfonic acid?

1H,1H,2H,2H-Perfluorooctanesulfonic acid (6:2 FTS) is one of the representative compounds of perfluoro- and polyfluoroalkyl substances (PFAS) and is present in some aqueous film-forming foam (AFFF) products. Studies have shown that significant levels of 6:2 FTS and 8:2 FTS are produced following the oxidation of these AFFFs. For example, 6:2 fluoroterminated alkyl sulphamido betaine (6:2 FTAB), a key component of AFFFs used in firefighting, is frequently detected alongside one of its suspected transformation products—6:2 FTS—in terrestrial and aquatic ecosystems affected by AFFF use. A study on the biotransformation of 6:2 FTS found that its biotransformation is rate-limited: When the pore water flow rate decreased from 3.7 cm/day to 2.4 cm/day, the effluent concentration of 6:2 FTS decreased by 21.7–26.1%, whilst the yield of late-stage biotransformation products (C4–C7 perfluoroalkyl carboxylates) was higher (1.0–1.4 mol% vs. 0.3 mol%) The model-fitted biotransformation rate for the 6:2 FTS column (0.039–0.041 cm³/g·s·d) was approximately 3.5 times lower than the rate observed in the microcosm (0.137 cm³/g·s·d). Additionally, during column experiments, planktonic microbial communities remained relatively stable, whereas the composition of the attached microbial communities shifted along the flow path, which may have been attributed to oxygen availability and the toxicity of 6:2 FTS and associated biotransformation products. Genus Pseudomonas dominated in planktonic microbial communities, while in the attached microbial communities, Rhodococcus decreased and Pelotomaculum increased along the flow path, suggesting their potential involvement in early- and late-stage 6:2 FTS biotransformation, respectively.

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