PER- AND POLYFLUORINATED ALKYL SUBSTANCES (PFAS) IN PENNSYLVANIA SURFACE WATERS: A STATEWIDE ASSESSMENT, ASSOCIATED SOURCES, AND LAND-USE RELATIONS

The objective of this study was to survey PFAS occurrence and spatial distribution in Pennsylvania surface waters and explore potential sources of PFAS contamination (PSOC) using a multivariate approach. In September of 2019, discrete surface water samples were collected from 161 Pennsylvania Water Quality Network stations of major streams that had a median upstream catchment area of roughly 600 square-kilometers and a range of land use. Study streams were surrounded by PSOC from military bases and water pollution control facilities (WPCF), to electronic manufacturing and oil and gas wells, among others. Sample collection integrated the entire stream channel and samples were analyzed for 33 target PFAS. The R package “party” was utilized to produce conditional inference tree algorithms for the total hydrologic yield of 33 target PFAS (∑PFAS yield). Model features included ancillary water chemistry (e.g., pH, alkalinity, chloride, ammonia, and total nitrogen), physical parameters (e.g., depth to rock and precipitation), land use (e.g., development, cropland, and wetland), and geospatial counts of PSOC. The primary drivers of ∑PFAS yield were the percentage of development and number of WPCF in the drainage areas of streams. However, 10 sites that were surrounded by ≥2 electronic manufacturing facilities had the most elevated ∑PFAS yields (median=241 ng/sec/km²). In oil and gas development regions, ∑PFAS yields were associated with combined sewage outfalls. Surface water concentrations of total nitrogen, chloride, and ammonia, that are commonly associated with landscape alteration (e.g., development or agricultural cropland), were also significant predictors of ∑PFAS yield. Concentrations of PFOA and PFOS were compared to United States Environmental Protection Agency human health advisory levels (USEPA HAL) for drinking-water. Although the USEPA PFOA and PFOS HAL exceeded the respective analytical reporting levels, incidence of PFOA and PFOS HAL exceedances occurred at 70% and 47% of the study streams, respectively. Roughly half of the study streams may be sources for public drinking-water. This research highlights the first state-wide description of PFAS contamination, source attribution, and incidence of non-enforceable human health guideline exceedances in Pennsylvania surface water.