Poly- and perfluoroalkyl substances (PFASs) are widespread environmental contaminants that have been used by various industries for over 60 years for their unique stability, and hydrophobic, oleophobic, and surfactant properties. Evidence for negative impacts on human health associated with PFAS exposure has prompted a national response to protect the public’s drinking water supplies. However, understanding of the hydrological fate and transport of PFASs and implications for exposure from drinking water is still limited. In particular, perfluoroalkyl acid (PFAA) precursors, which can break down to perfluoroalkyl acids in the human body, have been understudied. PFAA precursors are not typically measured during water testing, resulting in underestimates of total exposure to PFASs. To address this gap, we investigated the fate and transport of PFAA precursors at a long-term U.S. Geological Survey research site on Cape Cod. This site was impacted by PFAS-containing aqueous film-forming foam (AFFF), which was used during fire training exercises between 1970 and 1985. This study presents new data tracking PFAA precursors as they are transported along a flow path from the AFFF point source to two groundwater-fed kettle ponds, and back into the groundwater, which is the source of drinking water for Cape Cod residents. Along this flow path the PFAA precursors encounter both oxic and anoxic conditions, among other geochemical variations. This field-scale study investigates whether oxygenated groundwater results in biotransformation of PFAA precursors on short time scales of a few years, while anaerobic conditions preserve PFAA precursors, allowing them to be transported in groundwater. Additionally, the finding of enriched concentrations (up to ~10x concentration enrichment) of PFASs near the groundwater table directly downgradient from the two ponds will be presented and the potential mechanisms discussed. This enrichment has implications for shallow groundwater quality near any PFAS-contaminated surface-water body that has interactions with groundwater.

Fate and transport of poly- and perfluoroalkyl substances across groundwater/surface-water boundaries

256th National Meeting (2018)

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