PFAS fate using lysimeters during degraded soil reclamation using biosolids

Abstract Carbon‐ and nutrient‐rich biosolids are used in agriculture and land reclamation. However, per‐ and polyfluoroalkyl substances (PFAS) typically present in biosolids raise concerns of PFAS leaching to groundwater and plant uptake. Here, we investigated PFAS persistence and leaching from biosolids applied to a site constructed artificially to mimic degraded soils. Treatments included biosolids and biosolids blended with mulch applied at different rates to attain either one and five times the agronomic N rate for vegetable crops and a control treatment with synthetic urea and triple superphosphate fertilizer. Leachates were collected for a 2‐year period from 15‐cm depth zero‐tension drainage lysimeters. Soils were analyzed post biosolids application. PFAS were quantified using isotope‐dilution, solid‐phase extraction and liquid chromatography tandem mass spectrometry. Leachate profiles exemplified an initial high total PFAS concentration, followed by a sharp decline and subsequent small fluctuations attributed to pre‐existing soil conditions and rainfall patterns. Quantifiable PFAS in leachate were proportional to biosolids application rates. Short‐chain perfluoroalkyl acids (CF 2 < 6) were dominant in leachate, while the percentage of longer chains homologues was higher in soils. A 43% biosolids blend with mulch resulted in 21% lower PFAS leachate concentrations even with the blend application rate being 1.5 times higher than biosolids due to the blend's lower N‐content. The blending effect was more pronounced for long‐chain perfluoroalkyl sulfonic acids that have a greater retention by soils and the air–water interface. Biosolids blending as a pragmatic strategy for reducing PFAS leachate concentrations may aid in the sustainable beneficial reuse of biosolids.