The effects of soil properties and sorbent amendments on immobilization of perfluorooctane sulfonate (PFOS) in contrasting soils: Experimental and numerical study

Per-and polyfluoroalkyl substances (PFAS), a class of manmade organo-fluorine chemicals, are a serious chal-lenge to water supplies. In this study, the effects of physicochemical properties of Florida topsoil and Ringold formation Hanford site sediment as well as the influence of immobilizers on the sorption behavior of PFOS were tested. Activated charcoal (AC) and food waste compost amendments were added to the soil and sediment at 0.1 and 3 wt% concentration, respectively. The PFOS adsorption fits best to pseudo second-order kinetic and Freundlich isotherm models. PFOS uptake was greater in Florida topsoil compared to Hanford site sediment, indicating that organic matter played a key role in the retention of PFOS. The food waste compost amendment at 3 wt% had no impact on PFOS uptake. However, AC amendment at 0.1 wt% enhanced PFOS sorption in Florida topsoil by 80% and Hanford site sediment by 99% through increasing the soil/water partitioning coefficients (kd value). A one-dimensional model was used to simulate the influence of AC in Florida topsoil on the leaching of PFOS to the groundwater by the percolation of rainwater over time. The results demonstrated the addition of 0.1 wt% AC, to the soil dramatically inhibits or delays the leaching of PFOS for up to one year under certain con-ditions to below the guideline for maximum concentration level (0.02 ng/L). The amendment could control PFOS release for more than 10 years by increasing the kd value by 10 times.