Sources and Pathways of PFAS Occurrence in Water Sources: Relative Contribution of Land-Applied Biosolids in an Agricultural Dominated Watershed.

This study evaluated PFAS occurrence in rural well water and surface water relative to land application of biosolids in a tile-drained agriculture-dominated watershed. Spatial data were used to identify potentially vulnerable rural wells based on their proximity to biosolid-permitted land and location with respect to groundwater flow. Water was collected from 103 private wells in Greater Tippecanoe County Indiana and 168 surface water locations within the Region of the Great Bend of the Wabash River watershed. Overall, results indicate that surface water (∑PFAS ≤ 169.4 ng/L) is more vulnerable to PFAS contamination than well water (∑PFAS ≤ 15.7 ng/L). Short-chain perfluoroalkyl acids made up 72% of the ∑PFAS in both water sources. Nonetheless, long-chain homologues were detected more frequently in surface water (94%) than well water (82%). Hierarchical cluster analysis identified biosolid-applied fields, WTTPs, and industrial discharges as PFAS sources in first-order streams with high ∑PFAS. Temporal trends revealed an inverse relationship between streamflow and concentrations in surface water sites impacted by point discharges and vice versa for diffuse sources, thereby providing complementary evidence of potential sources. The well water data set did not show a distinct spatial trend between ∑PFAS and distance from biosolid application or well characteristics.