Perfluoroalkane Sulfonamides and Derivatives, a Different Class of PFAS: Sorption and Microbial Biotransformation Insights.

Perfluoroalkane sulfonamides and their derivatives (FASAs), an emerging subclass of per- and polyfluoroalkyl substances (PFAS), have attracted increasing attention due to their widespread applications, environmental persistence, and potential biological toxicity. Unlike perfluoroalkyl acids (PFAAs), FASAs can be transformed by microorganisms in the environment, producing fluorinated intermediates that eventually form stable PFAAs. A key difference of FASAs is that their pKas enable them to exist as neutral species or zwitterions, unlike all other PFAS subclasses, which are all anions. Sorption processes regulate the bioavailability of FASAs to microorganisms for transformation, driving the environmental transport and fate of FASAs. In this critical review, we provide a comprehensive overview of the classification, properties, and environmental fate of FASAs, with a focus on sorption and microbial transformation. We discuss recent advancements in understanding the sorption of FASAs onto soil, sediment, and microbial biomass, including key sorption descriptors and influencing factors. Additionally, we examine the microbial biotransformation of FASAs, detailing transformation pathways, key intermediates, transformation kinetics, and enzymes involved. Finally, we identify critical research gaps and propose future directions to advance the study of the sorption and biotransformation of FASAs in environmental systems. Mechanistic understanding of these processes is crucial for managing sites impacted with FASAs.