PFAS in Iowa drinking water sources: Chemical and geospatial patterns

Per- and polyfluoroalkyl substances (PFAS) are toxic, persistent, and ubiquitous contaminants which are harmful to the environment and human health. We analyzed publicly accessible records of PFAS concentrations in surface water and groundwater used for public drinking water supplies across the state of Iowa, along with groundwater from private wells near suspected contamination sources. We analyzed these data using the Mann-Whitney U test, principal component analysis, analysis of variance, and Tukey's honestly significant difference test to identify contamination patterns at the regional and local scale. Results indicate that surface water sources across the state are much more likely to contain PFAS than groundwater sources (i.e., 94 % vs. 30 %), but among contaminated public water sources, groundwater has a higher average total PFAS concentration than surface water (i.e., 43.9 ng/L vs. 9.8 ng/L). Two short-chain PFAS (PFBA and PFPeA) dominate surface water sources across the state apart from the Mississippi River, which contains elevated concentrations of PFOS and PFOA. The Mississippi River also influences groundwater within the breadth of its floodplain and associated alluvial aquifer; most groundwater under the influence of the Mississippi River has a similar PFAS fingerprint to the river itself and contains greater concentrations of PFBA than is typical of contaminated groundwaters located outside the influence of the river. Case studies from public and private wells in four PFAS-impacted communities further illustrate that despite regional-scale patterns, PFAS contamination of non-alluvial groundwater often reflects highly local point sources, including firefighting activities and fluorochemical manufacturing, storage, or use. These results demonstrate the utility of regional analyses for characterizing PFAS threats to water supplies and contextualizing local PFAS data in spite of complex source mixtures and fate and transport behavior.