Aqueous film-forming foams (AFFFs) that have been used to extinguish solvent based fires contain complex chemical mixtures including poly- or per-fluorochemicals. Since perfluoroalkyl acids (PFAAs), such as perfluorooctane sulfonate and perfluorooctanoic acid have been demonstrated to be persistent in the environment and harmful to public health, their use in AFFFs is being phased out. However, polyfluoroalkyl substances (PFASs) that contain perfluoroalkyl chains and various ionic functional heads in AFFFs have been suspected to contribute to the formation of PFAAs at contaminated sites. Although recent analytical studies have revealed the identities of principle PFASs in different AFFF formulations, knowledge of the environmental fate and specifically the anaerobic biotransformation products of these PFASs are still lacking.The objective of this study was to investigate the microbial transformation products (TPs) of 6:2 fluorotelomer thioamidosulfonate (6:2FtTAoS) in a widely used AFFF formulation. Microcosms, representing different redox conditions (i.e., nitrate-, iron-, sulfate-reducing and methanogenic conditions) were constructed with this AFFF using both AFFF impacted soil and pristine sediments. Samples from the live and control microcosms were analyzed by liquid-chromatography-tandem mass spectrometry to quantify 6:2FtTAoS and to acquire mass spectrometry data. A high-throughput screening method was developed to identify candidate TPs, of which the elemental compositions and structures were proposed using high resolution mass spectrometry analysis and MS/MS fragment analysis.Our results indicate that 6:2FtTAoS was transformed via a fluorotelomer thiol carboxylic acid intermediate in all anaerobic microcosms. However, the further transformation of this intermediate varied among redox conditions. A list of previously reported and unreported TPs were identified from live microcosms. The results of this study expand the understanding of the fate of PFASs in the environment, which will help to determine appropriate monitoring and remedial strategies applied to AFFF-impacted sites.

Detection and identification of anaerobic biotransformation products of polyfluorochemicals in aqueous film-forming foams

248th National Meeting (2014)

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