This article presents two aspects of an Environmental Security Technology Certification Program (ESTCP) demonstration conducted at Camp Grayling Army Airfield in Grayling, Michigan: verification of an accelerated per‐ and polyfluoroalkyl substances (PFAS) screening method using liquid chromatography and tandem mass spectroscopy and its application to develop a flux‐based conceptual model. The ESTCP project information can be found here: https://serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER19-5203. The objective is to demonstrate the value of adaptive high‐resolution PFAS site characterization using a quantitative screening method that is selective for PFAS compounds and sensitive across the range of concentrations between screening levels at 40 nanograms per liter and source impacts within the milligram per liter range. The reliability of the method is demonstrated using three metrics: sample pair comparability statistics with an Environmental Laboratory Accreditation Program‐certified lab, visual interpretation of characterization and relative flux, and comparison of contaminant mass discharge calculated at flux transects. In addition, the study measured vadose zone source strength using three methods: soil to groundwater concentration ratios, lysimeter porewater sample analysis, and synthetic precipitation leaching procedure testing. The overall results demonstrate that application of the mobile lab and the stratigraphic flux approach can distinguish individual PFAS sources, visually map perfluorooctanoic acid and perfluorooctane sulfonate and migration pathways, and provide an efficient means of ranking source contributions to plumes.

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For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit https://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov/.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.Suggested citation: Hayes, T.S., Miller, M.M., Orris, G.J., and Piatak, N.M., 2017, Fluorine, chap. G of Schulz, K.J., DeYoung, J.H., Jr., Seal, R.R., II, and Bradley, D.C., eds., Critical mineral resources of the United States-Economic and environmental geology and prospects for future supply: U.S. Geological Survey Professional Paper 1802, p. G1-G80, https://doi.org/ 10.3133/pp1802G. Supplemental InformationSpecific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25 °C). Activities for radioactive constituents in air are given in microcuries per milliliter (µCi/mL). ConcentrationsDeposit grades are commonly given in percent, grams per metric ton (g/t)-which is equivalent to parts per million (ppm)-or troy ounces per short ton (oz/T).Geologic ages are expressed in mega-annum (Ma, million years before present, or 10 6 years ago) or giga-annum (Ga, billion years before present, or 10 9 years ago).For ranges of years, "to" and (or) the en dash ("-") mean "up to and including." Concentration unit Equals AbstractFluorine compounds are essential in numerous chemical and manufacturing processes.

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