Assessing the Shifts in Atmospheric Per- and Polyfluoroalkyl Substances (PFAS) Levels in the Great Lakes and Implications for the Environmental Transport and Fate

This study presents the first multiyear investigation of per- and polyfluoroalkyl substances (PFAS) in the atmosphere over the Great Lakes. The levels of ∑PFAS exhibit a broad range from 2.9 to 280 pg/m³. Higher concentrations of PFAS at the urban-influenced site compared to the rural site signified spatial variability between the two sampling locations. Despite the absence of a consistent seasonal pattern, concentrations of perfluorooctanoic acid (PFOA) and neutral PFAS (nPFAS) tend to be higher during the summer months. This pattern appears to be influenced by the seasonal variations of air back trajectories and potential influences from south of the sampling site. The study elucidates potential shifts in atmospheric PFAS dynamics during the COVID-19 pandemic. Applying a modified model with a probabilistic approach, we investigated the transport and fate of PFOA and perfluorooctanesulfonic acid (PFOS) within Lake Ontario. The estimated loadings of PFOA and PFOS from air-to-water were 9.5 ± 3.6 and 17 ± 6.6 kg/y, respectively, close to the values from wet deposition (10 ± 3.9 and 31 ± 12 kg/y, respectively) but much lower than those from inflow and all other sources. The primary output pathways for PFOA and PFOS were from water outflow.

PFAS in the Great Lakes’ atmosphere reveal various spatial and seasonal variability impacted by potential sources and COVID-19, with fate modeling underscoring unaccounted for PFOA inputs to Lake Ontario.