OCCURRENCE AND TRANSPORT OF POLY- AND PERFLUOROALKYL SUBSTANCES (PFAS) IN GROUNDWATER NEAR A FORMER FIRE-TRAINING AREA AND WASTEWATER DISPOSAL SITE ON CAPE COD, MASSACHUSETTS (Invited Presentation)

Poly- and perfluoroalkyl substances (PFAS) have been used since the 1950s for many applications because of their high stability and surfactant, hydrophobic, and oleophobic properties. Contamination of groundwater by PFAS is a growing concern because of their use in industrial processes, widespread use in aqueous film-forming foams (AFFFs) for fire suppression, and presence in landfill leachate and wastewater. We are investigating a PFAS plume at the site of a former fire-training area (operated from 1958 to 1985, with AFFF use beginning in 1970) and downgradient wastewater-infiltration beds (used from 1936 to 1995) near a military base on western Cape Cod to understand the subsurface transport of PFAS. More than 100 groundwater samples were collected in 2015 from monitoring wells located along a 1-km-long transect that is aligned with the direction of groundwater flow in the glacial sand and gravel aquifer. Concentrations of PFAS compounds analyzed by LC-MS/MS were used to construct vertical profiles of the subsurface PFAS distribution. Concentrations as high as 63 micrograms per liter (µg/L) perfluorooctanesulfonic acid (PFOS) and 8 µg/L perfluorooctanoic acid (PFOA) were measured. The Environmental Protection Agency has established a drinking water health advisory standard of 0.070 µg/L for the sum of PFOS and PFOA concentrations. PFAS signatures in shallow groundwater near the water table indicate that the PFAS sources in the vadose zones at the fire-training area and downgradient wastewater-infiltration beds are compositionally different, suggesting that the PFAS composition in groundwater samples can be used to “fingerprint” the potential sources. The PFAS plume partly discharges into a groundwater-flow-through glacial kettle lake about 1.1 km from the fire-training area. We measured concentrations as high as 1.8 µg/L PFOS and 0.14 µg/L PFOA in groundwater samples collected from shallow wells pushed about 1 m into the lake bottom near shore. Lake-water samples collected near the discharge area had concentrations as high as 0.080 µg/L PFOS and 0.029 µg/L PFOA. Studies are underway to determine whether PFOS and PFOA are present in lake-derived groundwater downgradient from the lake.