Per- and Polyfluoroalkyl Substances in Surface Runoff and Groundwater following Biosolids Land Application

Per- and polyfluoroalkyl substances (PFAS) in surface runoff and spatiotemporal patterns in groundwater impacted by the land application of biosolids since the 1980s were investigated at a site dominated by three soil types with varying permeabilities and drainage behaviors. The field has six groundwater monitoring sites with pairs of shallow and deep wells, in addition to two runoff collection sites downstream of plots that have historically received biosolids. Runoff samples were collected twice in 2023, and monitoring wells were sampled quarterly between November 2022 and September 2024. Nine years after biosolids application, substantial PFAS loads, up to 173 mg, of which PFOS was dominant, were measured in surface runoff during a rain event. In monitoring wells, total PFAS concentrations were generally between nondetect and 32 ng/L and dominated by short-chain carboxylates (PFCAs), with no exceedances of US EPA 2024 drinking water maximum concentration levels. Exceptions were two wells located in the sandier soils and bordering a multisource PFAS-impacted lake, in which PFAS concentrations up to hundreds of ppt were detected. The high concentrations in those wells suggest that advective flow through highly permeable aquifer materials and likely lateral flow (surface water-groundwater interactions) are influencing PFAS transport dynamics at the site.