Correlation Analysis of Perfluoroalkyl Substances in Regional U.S. Precipitation Events

Per- and polyfluoroalkyl substances (PFAS) are transported in the atmosphere, leading to both wet and dry deposition to the surface. The concentrations of 15 PFAS were measured at six locations in the Ohio-Indiana region of the U.S. during the summer of 2019 and compared to samples collected at a distant site in NW Wyoming. ΣPFAS concentrations ranged from 50-850 ng L^-1, with trifluoroacetic acid (TFA) being the dominant compound (~90%). Concentrations of perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS) were similar to amounts observed over the past 20 years, indicating persistence in the atmosphere despite regulatory action, and the newer species HFPO-DA (GenX) was also widely detected in rainwater. ANOVA modeling and correlation matrices were used to determine association of PFAS concentrations, location, and functional group and chain length. Statistically significant differences (p < 0.05) in PFAS profiles across sites separated by 10-100 km indicate that local point sources strongly contribute to wet deposition. This work introduces correlation plots for PFAS that allow rapid visual comparison of multi-analyte and multi-site data sets.