Assessing PFAS uptake in hemp and alfalfa using congener-resolved analyses and soil quality measurements

Abstract

Understanding phytoaccumulation of environmental contaminants in agricultural crops is essential for assessing contaminant cycling, ecological restoration and risk, and exposure pathways. This study assessed the uptake of per - and polyfluoroalkyl substances (PFAS), in Cannabis sativa (CBD-hemp) and Medicago sativa (alfalfa) across two greenhouse trials. Congener-resolved-PFAS analyses were performed on soil and plant tissues to characterize uptake patterns and examine how variability in soil quality aligns with PFAS accumulation. In alfalfa, short-chain PFAS predominated in shoots and long-chain PFAS molecules in roots, while total PFAS concentrations were similar across tissues. In hemp, inflorescences carried the highest PFAS concentration and stems the lowest. For both species, translocation factors (TF; shoot/root PFAS concentration) and bioconcentration factors (BCF; plant tissue/soil PFAS concentration) decreased with increasing PFAS chain length for both perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs). Relationships between % soil organic matter (SOM) and PFAS uptake were species- and compound-specific, whereas soil electrical conductivity (EC) exhibited more consistent associations with PFAS concentrations in soil and plant tissues. Higher PFAS concentrations in hemp roots and lower residual soil PFAS concentrations at harvest were associated with lower EC, resulting in higher BCF values for both species. These findings suggest that soil ionic conditions may influence PFAS mobility and bioavailability and highlight the value of incorporating soil EC measurements alongside PFAS concentrations when evaluating PFAS uptake in agricultural systems.