Per- and Polyfluoroalkyl Substances (PFAS) Fate and Transport in Surface Waters Near Eaker Air Force Base, Arkansas

Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic fluorinated compounds commonly associated with aqueous film-forming foam used in fire-training at Air Force bases. Target perfluoroalkyl acids and sulfonates (PFAAs) were quantified in surface waters around Eaker Air Force Base (Arkansas, USA) using U.S. Environmental Protection Agency Method 1633, with a total oxidizable precursor (TOP) assay (modified Method 537) applied at targeted sites. Spatially distributed grab samples characterized PFAS occurrence, followed by oxidation testing at one control site, one hotspot, and one downstream site to assess precursor presence. Perfluorooctanesulfonic acid (≤ 69 ng/L) and perfluorohexanesulfonic acid (≤ 54 ng/L) dominated downstream sites, while upstream reference sites showed trace detections (≤ 1.5 ng/L). TOP assay oxidation increased perfluoroalkyl acid concentrations at the most contaminated site, indicating the presence of oxidizable precursors. These findings indicate legacy contamination and demonstrate that precursor transformation contributes to downstream PFAS exposure, supporting inclusion of precursor compounds in future monitoring programs.