Like for other legacy compounds, such as polychlorinated biphenyls (PCBs), atmospheric deposition could be a significant environmental pathway for delivering PFAS in the environment. PFAS are washed out from the atmosphere by wet and dry deposition and the gas absorption process, of which precipitation is generally considered the dominant mechanism. To date, the mass transfer flow of PFAS via atmospheric deposition to the Great Lakes was not well addressed.

In this study, precipitation (n=207) and air (n = 60) from five sites and water samples (n = 87) from all five Great Lakes were collected in 2021-2023 and analyzed for 41 per- and polyfluoroalkyl substances (PFAS) as part of the Integrated Atmospheric Deposition Network (IADN). These measurements were combined with other available data to estimate the mass budget for 4 representative compounds, PFBA, PFBS, PFOS, and PFOA for the basin. The Σ₄₁PFAS concentrations in precipitation across the five sites ranged between 2.4 and 4.5 ng/L. The median Σ₄₁PFAS concentration in lake water was highest in Lake Ontario (11 ng/L) and lowest in Lake Superior (1.3 ng/ L). The median Σ₄₁PFAS concentration in air samples was highest in Cleveland at 403 pg/m³ and lowest at Sleeping Bear Dunes at 150 pg/m³. The net mass transfer flows were generally negative for Lakes Superior, Michigan, and Huron and positive for Lakes Erie and Ontario, indicating that the three most northern lakes are accumulating PFAS and the other two eliminating PFAS. Atmospheric deposition is an important source of PFAS, particularly for Lake Superior.

¹ O'Neill School of Public and Environmental Affairs, Indiana University, Bloomington, IN

² Environment and Climate Change Canada, Water Quality Monitoring and Surveillance, Burlington, ON, Canada

* Corresponding Author: mvenier@iu.edu