Fate, Transport, and Detection of Poly- and Perfluoroalkyl Substances in Natural and Engineered Environments

Exposure to poly- and perfluoroalkyl substances (PFASs) has been linked to metabolic disruption, immunotoxicity, and cancer in humans, among other adverse health outcomes. The widespread contamination of drinking water arising from the persistence and aqueous mobility of PFASs prompted the U.S. Environmental Protection Agency to issue a lifetime drinking water health advisory for two specific PFASs in 2016: perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). An overview of the intractable PFAS contamination issue is provided in Chapter 1. Given that groundwater is a major source of drinking water, the main objective in Chapter 2 was to investigate geochemical and hydrological processes governing the subsurface transport of PFASs at a former fire training area on Cape Cod, Massachusetts, where PFAS-containing aqueous film-forming foams (AFFFs) were used historically. AFFF is one of the primary sources of groundwater and surface water PFAS contamination in the United States. One of the outcomes from this study was the discovery of mobile perfluoroalkyl acid (PFAA) precursors. PFAA precursors can transform in the human body to terminal compounds such as PFOS and PFOA, but are not included in typical drinking water analysis. Chapter 3 presents an investigation of PFAS transport and the persistence of PFAA precursors across groundwater/surface water boundaries. Although the transport of PFASs through these boundaries was impacted by a complex mixture of hydrogeochemical conditions, the persistence of precursors in aerobic surface waters and downgradient groundwater (located in residential areas) was established. Chapters 2 and 3 highlight the importance of understanding the total mass of organic fluorine (including precursors) in water. Chapter 4 compliments this by presenting a method to measure total organic fluorine in the surface of consumer products, which are another primary source of PFAS exposure to humans. X-ray photoelectron spectroscopy is demonstrated to be a reliable tool to quantify surficial fluorine in consumer products, can provide important information on the depth distribution of fluorine, and does not require time-intensive extraction procedures prior to analysis, which is an advantage over traditional PFAS analysis techniques.