Analysis of PFAS in Wet Deposition near Lake Superior
Alissia M. Milani1, *, Kaitlyn J. Gruber2, Martin Shafer3, and Christina K. Remucal1, 4
Historic and ongoing per- and polyfluoroalkyl substances (PFAS) contamination in Lake Superior is of great concern. Wet deposition (rain and snow) is a significant source of PFAS to Lake Superior due to the limited number of PFAS point sources in the region, large lake surface area, and relatively small watershed. However, these atmospheric inputs are poorly characterized and constrained. Being the furthest upstream and having a hydraulic residence time of 173 years, PFAS concentrations in Lake Superior will likely affect downstream rivers and the lower Laurentian Great Lakes for decades to come. With many PFAS species being persistent and toxic, understanding sources of PFAS and mitigating contamination is critical. From 2022 to 2023, wet deposition samples were collected on a weekly basis from nine National Trend Network sites around Lake Superior through collaboration with the National Atmospheric Deposition Program (NADP). The wet deposition samples were analyzed for 36 PFAS compounds in five major classes by liquid chromatography-tandem mass spectrometry. The distribution of PFAS classes varied between sites, potentially indicating a regional impact on the concentration of PFAS species in wet deposition. Perfluorocarboxylic acids (PFCAs) were the most frequently detected and most abundant class of PFAS quantified. The high abundance of PFCAs is consistent with previous wet deposition studies and may partially result from atmospheric transformation of volatile precursor PFAS. This wet deposition study will compliment Lake Superior tributary and sediment core datasets to provide a comprehensive analysis of PFAS source contributions to Lake Superior.
1 Environmental Chemistry and Technology Program, University of Wisconsin – Madison, Madison, WI
2 Department of Chemistry , University of Wisconsin – Madison, Madison, WI
3 Wisconsin State Laboratory of Hygiene, University of Wisconsin – Madison, Madison, WI
4 Department of Civil and Environmental Engineering, University of Wisconsin – Madison, Madison, WI
* Corresponding author: ammilani@wisc.edu