PFAS in soil and groundwater following historical land application of biosolids

The land application of digested sewage sludge (biosolids) is widely employed across the globe. Studies show that biosolids contain significant amounts of inorganic and organic materials, as well as emerging pollutants, including per- and polyfluorinated alkyl substances (PFAS). With the wide range of pollutants commonly reported in biosolids, the potential risks associated with long-term land application operations are concerning. In this study, PFAS in surface soils, deeper soils into the vadose zone, and immediately-underlying groundwater was measured at an agricultural station with a long record of biosolids applications plus irrigation using treated wastewater. Twelve PFAS homologues were detected in every near surface soil sampled 0-30 cm depth below ground surface with multiple PFAS (especially short-chain) distributed through the soil profile. Average measured concentrations of PFAS in these soils suggest the soil burden PFOS>PFDA>PFOA for all substations sampled, independent of the historical loading rates and patterns of agricultural operations on those substations. Measured concentrations of PFOA and PFOS in the soil profile (0-90 cm) suggest these compounds have migrated to deeper soil depths (up to 9 m below the surface) with quantifiable concentrations in the soil and the immediate underlying groundwater located approximately 17 m below. Estimates of the total mass of PFAS in surface soils were effectively made using PFAS levels reported in sludges from the USEPA NSSS combined with long-term loading rates on record at the substations. With the land application of biosolids in the USA regulated by the USEPA, additional and updated risk assessments and surveys to include emerging pollutants such as PFAS are needed to protect public health and the environment.