Fate and Transformation of 15 Classes of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foam (AFFF)-Amended Soil Microcosms

Environ Sci Technol. 2024 Dec 24;58(51):22777-22789. doi: 10.1021/acs.est.4c08665. Epub 2024 Dec 10.

Abstract

The environmental fate of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foams (AFFFs), especially those synthesized by electrochemical fluorination (ECF) processes, remains largely unknown. This study evaluated the transformation of AFFF-derived ECF-based precursors in aerobic soil microcosms amended with a historically used AFFF formulation (3M Light WaterTM). Fifteen classes of PFAS, including AFFF components and transformation products, were identified or tentatively identified by suspect screening/nontargeted analysis (SSA/NTA) throughout a 308-day incubation. This study demonstrates that AFFF-derived ECF-based precursors serve as sources of perfluoroalkane sulfonamides (FASAs) and perfluoroalkyl acids (PFAAs), which are commonly detected at AFFF-impacted sites. Temporal sampling provided evidence for biotransformation of multiple precursors including tri- or dimethyl ammonio propyl perfluoroalkane sulfonamides. Additionally, the environmental stability (i.e., resistance to transformation) of ECF-based precursors was found to depend upon structural characteristics, including perfluoroalkyl chain length, presence of sulfonamide or carboxamide groups, and functional groups (e.g., a branch of carboxyalkyl group) attached to the nitrogen atoms. These findings provide insights into the transformation pathways of AFFF-derived PFAS and other structurally similar ECF-based PFAS, which will support the management and remediation of PFAS contamination at legacy AFFF-impacted sites.

Keywords: AFFF; biotransformation; high resolution mass spectrometry (HRMS); per- and polyfluoroalkyl substances (PFAS); soil microcosm; sulfonamide- and carboxamide-based precursors.

MeSH terms

  • Fluorocarbons* / chemistry
  • Halogenation
  • Soil Pollutants*
  • Soil* / chemistry

Substances

  • Soil Pollutants
  • Soil
  • Fluorocarbons