Effects of soil aging on distribution and desorption kinetics of per- and polyfluoroalkyl substances by diffusive gradients in thin films

Soil aging is recognized to influence the soil-water partitioning behavior of organic pollutants, altering their mobility and bioavailability. However, the specific impacts of soil aging on the desorption behavior of per- and polyfluoroalkyl substances (PFAS) from the solid phase require further investigation. This study investigated the impact of soil aging on the distribution and desorption kinetics of eleven legacy and emerging PFAS in agricultural soils, using the diffusive gradients in thin films (DGT) technique. The results demonstrate that soil aging strengthened interactions between PFAS and soil particles, simultaneously reducing concentrations in both the soil solution and solid phase compartments. Additionally, high organic matter content facilitated PFAS sequestration. The nonlinear increase in PFAS mass accumulated by DGT device suggested that the consumption of PFAS at the DGT surface was partially offset by the resupply of labile PFAS from the solid phase. Modeling with the DGT-induced fluxes in soil model indicated that the labile pool size decreased following soil aging, with values ranging from 0.11 to 168 mL/g after 14 days and from 0.34 to 83 mL/g after 120 days. Overall, this study demonstrates that soil aging reduced PFAS concentration in the soil solution while also decreasing the labile pool size. These findings are significant for assessing PFAS transfer, fate, bioavailability, and potential risks to ecosystems and human health.