Large Fraction of Unidentified Organofluorine in a Coastal Watershed has Implications for River to Marine Ecosystems Active

Water supplies for millions of people in the United States exceed Federal guidelines for perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), which are two compounds in a broad class of persistent human-made chemicals known as per- and polyfluoroalkyl substances (PFAS). Major uses of PFAS include nonstick coatings on cookware, home textiles, food packaging, and as a component of aqueous film forming foams (AFFF) used in firefighting and fire training. PFAS enter watersheds through numerous pathways, including infiltration of AFFF through the unsaturated zone, industrial and domestic wastewater discharges to surface water, and septic system discharges to groundwater. The large number of compounds, variety of uses, and varying compositions of PFAS in use can make it difficult to identify PFAS origins.

An additional difficulty in identifying the origins of PFAS in a watershed is that the composition of PFAS changes as it moves through surface water and groundwater. Moreover, traditional laboratory methods are limited to a small fraction of the PFAS present in AFFF and environmental samples.

To address these limitations, scientists at the Harvard University John A. Paulson School of Engineering and Applied Sciences and at the U.S. Geological Survey (USGS) examined PFAS transport among six adjacent coastal watersheds (with well-characterized hydrology through previous USGS research efforts) on Cape Cod, Massachusetts  during 2016–19. Laboratory methods, including analyses of 27 targeted PFAS, total oxidizable PFAS precursors, and total extractable organofluorine, were used along with unique multivariate clustering techniques to distinguish PFAS sources in natural waters and quantify movement of various forms of PFAS to coastal watersheds.

The scientists identified a distinct signature of AFFF in watersheds with an AFFF source compared to watersheds without an AFFF source. There were greater concentrations of the targeted PFAS and total oxidizable precursors in AFFF-affected watersheds compared to watersheds without known AFFF sources. The scientists also determined that only 24 to 63 percent of the extractable organofluorine can be explained by targeted PFAS and oxidizable precursors, indicating the presence of unidentified non-AFFF organofluorine sources in these coastal watersheds.

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This study also indicated that legacy PFAS in slowly moving groundwater constitute a source to the downstream coastal environment. There can be a substantial lag between environmental PFAS release and discharge to the coastal environment in  where groundwater is the predominant transport pathway. For example, legacy PFAS are still being observed in the Quashnet River that flows into a local estuary more than 20 years after the AFFF release at Joint Base Cape Cod indicating potential marine life exposure to PFAS at this site long after the original contamination.

This study was funded by the National Institute for Environmental Health Sciences Superfund Research Program (P42ES027706) through the Sources, Transport, Exposure and Effects of PFAS (STEEP) Program led by the University of Rhode Island, with additional support by the Strategic Environmental Research and Development Program (ER18-1280). Support for Andrea Tokranov and Denis LeBlanc was provided by the Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology) of the USGS Ecosystems Mission Area.

Reference

Ruyle, B. J., Pickard, H.M., LeBlanc, D.R., Tokranov, A.K.,Thackray, C.P., Hu, X.C., Vecitis, C.D., and Sunderland, E.M., 2021, Isolating the AFFF Signature in Coastal Watersheds Using Oxidizable PFAS Precursors and Unexplained Organofluoine, Environmental Science & Technology v. 55, pp. 3686-3695, https://pubs.acs.org/doi/10.1021/acs.est.0c07296.