An experimental investigation on the leaching of per- and polyfluoroalkyl substances (PFAS) from contaminated soil

For per- and polyfluoroalkyl substances (PFAS) released into the natural environment, soil represents a major pathway for their transport to the underlying groundwater, which represents a major drinking water source. Presently, there is a knowledge gap related to the transport of PFAS within the unsaturated soil.
The primary goal of this research is to fill this knowledge gap by quantifying PFAS leaching from intact, contaminated soil cores, which will be collected from several locations within Wisconsin. The location of the soil core collection sites will be determined based on factors such as soil type and properties and PFAS contamination history. Rainwater will be collected and applied to the top of the intact leaching experiment soil cores at rates that are relevant to natural infiltration conditions. The flow patterns within the intact soil cores will be monitored using soil moisture sensors and tensiometers. The leachate will be collected over time, the volume of the leachate will be measured, and both aqueous and colloid-bound PFAS concentrations in the leachate samples will be determined.
The findings from this research will allow us to quantify PFAS export from the contaminated soil to underlying groundwater aquifers, and to determine how long the contaminated soil can serve as important source of PFAS in the future. If different transport behavior of PFAS within soil cores collected from different sites is observed, the comparison of the soil physicochemical properties and hydrological patterns can allow us to identify the key factors that control PFAS mobility within the vadose zone. Together with our understanding of PFAS transport within the groundwater aquifer, we may be able to identify potential “high risk” (and currently overlooked) areas in Wisconsin, which can provide guidance for future investigations. We will also use the experimental results to drive mathematical and numerical simulations with existing model frameworks.