Predicting per- and poly-fluoroalkyl substances leaching potential from biosolids-amended soils based on soil properties

Biosolids are often land-applied to improve crop production, but they can also introduce per- and poly-fluoroalkyl substances (PFAS) to agricultural fields. Here, column leaching experiments were used to quantify PFAS mobility from twelve varying soils amended with three different biosolids. Leachate PFAS concentrations dropped rapidly with increasing liquid-to-solid ratio, indicating an early flush of water-soluble PFAS followed by slower desorption of more strongly retained PFAS. Biosolids differed markedly in PFAS leaching behavior, with those containing the highest water-soluble PFAS fraction producing the highest initial leachate PFAS concentrations and total PFAS mass loss. Correlation analysis revealed that cumulative PFAS mass leached was associated with soil organic matter, iron and aluminum oxides, and clay content. Forward-selected multiple linear regression (MLR) collectively explained approximately 74–92% of the variance across treatments. In compound-specific MLR, statistically significant models for PFOA, PFOS, PFNA, PFBS, PFHxA, and PFHxS were obtained for one biosolids that acted as a net PFAS source within all 12 soils. The predictive relationship was weaker for the other two biosolids, possibly due to biosolids acting as a PFAS sink in several studied soils. Biosolids addition may increase total PFAS loading, but the water-soluble PFAS fraction can increase or decrease depending on whether the biosolids amendment functions as a source or a sink. Accordingly, PFAS leaching is jointly controlled by soil and biosolids properties, and the water-soluble PFAS fraction is a more informative predictor of leaching potential than total PFAS following biosolids application.