ASSESSING PFAS ENRICHMENT IN SURFACE WATER FOAMS WITHIN THE NESHAMINY CREEK BASIN IN SOUTHEASTERN PENNSYLVANIA

One understudied phenomenon that has been shown to concentrate and release per-and polyfluoroalkyl substances (PFAS) in the environment is the formation of surface water foams. For foams to form, surface active compounds (humic and fulvic acids, colloidal particles, and/or proteins) or surfactants must be present in the water along with a source of agitation that creates gas bubbles. Studies have shown that these surface water foams can concentrate individual PFAS up to 2800 times the surrounding bulk water. Yet, there is still somewhat limited information available on PFAS concentrations and composition within surface water foams. The goals of this study were to 1) further refine foam sampling and mass estimation methods and 2) sample foam bodies on streams within the Neshaminy Creek basin, a basin with documented PFAS sources (military bases with AFFF releases and sewage treatment plant outfalls). From June through October, 2022, five unique foam bodies and surrounding waters (upstream, downstream, and water under foam) were sampled and analyzed for target PFAS (draft EPA Method 1633), total oxidizable precursors, and dissolved organic matter (DOM). Sediment at each foam location was also sampled for target PFAS analysis. Results showed that PFAS and DOM composition and PFAS concentrations varied between matrices. Foam PFAS composition consisted of more long-chain (up to C14) PFAS and precursor compounds compared to surrounding waters. PFAS concentrations were also higher in foams than in surrounding waters. Foam enrichment was especially apparent for PFOS; enrichment factors ranged from 155 to 3300 times more PFOS in foam than underlying water. The maximum PFOS enrichment factor occurred at a site closest to a known military base PFAS source and was associated with the maximum PFOS foam concentration detected (215,000 ng/L). Results from this study suggest that surface water foams are an important matrix to consider in stream systems from the perspectives of PFAS fate and transport and potential exposure to aquatic organisms and humans in stream recreation areas.