NATURE AND FATE OF PFAS IN A STAGNANT ICE TERRAIN SAND AND GRAVEL AQUIFER

Detection of per- and polyfluoroalkyl substances (PFAS) in concentrations above EPA health advisory limits in 2019 led to closure of two of the five City of Rhinelander municipal water wells. The wells are in close proximity to potential PFAS source areas including biosolid sludge disposal on airport property along with potential firefighting foam use at the airport. Current exploration has determined that the closed, unlined landfill is not a contributing source of contamination. Here, I hypothesize that nearby surficial application of PFAS chemicals and subsequent migration in the vadose and saturated zones accounts for the observed concentrations in the downgradient wells #7 and #8. The goal of this thesis is to apply site characterization methods, including PFAS fingerprinting and groundwater modeling to the Rhinelander field site, to gain insight into the nature and fate of PFAS in soil and groundwater. The geology and hydrogeology of the field site is characterized using geophysical methods including electrical resistivity, electromagnetic, ground penetrating radar, and passive seismic techniques. Soil water characteristic curves, loss on ignition tests, and grain-size distributions from auger cuttings provide useful soil parameters for groundwater modeling and understanding of fate/transport of PFAS. Secondly, an environmental forensic technique termed “PFAS fingerprinting” is applied to water samples around the region. Multiple “PFAS fingerprints” are identified indicative of multiple and possibly comingled contamination sources. Additional sampling data collected from lysimeters installed near suspected source areas will further validate this effort. Lastly, a regional groundwater model is created to understand the regional and site-specific groundwater flow, in relation to possible areas of surficial PFAS releases. Using this, specific areas of influence are identified using forward and reverse modeled particle tracking