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Geochemical Implications of Brine Leakage into Freshwater Aquifers

Authors

  • Assaf Wunsch,

    Corresponding author
    1. Hydrologic Science and Engineering Program, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401.
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  • Alexis K. Navarre-Sitchler,

    1. Hydrologic Science and Engineering Program, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401.
    2. Geology and Geological Engineering Department, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401.
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  • John E. McCray

    1. Hydrologic Science and Engineering Program, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401.
    2. Civil and Environmental Engineering Department, Colorado School of Mines, 1500 Illinois St., Golden, CO 80401.
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  • Authors' Note: There are no known conflicts of interest associated with submission of this manuscript to Ground Water journal. Funds for this research were provided by the EPA STAR grant (#R834387) and by a graduate-student fellowship from IHS.

Abstract

CO2 injection into deep saline formations as a way to mitigate climate change raises concerns that leakage of saline waters from the injection formations will impact water quality of overlying aquifers, especially underground sources of drinking water (USDWs). This paper aims to characterize the geochemical composition of deep brines, with a focus on constituents that pose a human health risk and are regulated by the U.S. Environmental Protection Agency (USEPA). A statistical analysis of the NATCARB brine database, combined with simple mixing model calculations, show total dissolved solids and concentrations of chloride, boron, arsenic, sulfate, nitrate, iron and manganese may exceed plant tolerance or regulatory levels. Twelve agricultural crops evaluated for decreased productivity in the event of brine leakage would experience some yield reduction due to increased TDS at brine-USDW ratios of < 0.1, and a 50% yield reduction at < 0.2 brine-USDW ratio. A brine-USDW ratio as low as 0.004 may result in yield reduction in the most sensitive crops. The USEPA TDS secondary standard is exceeded at a brine fraction of approximately 0.002. To our knowledge, this is the first study to consider agricultural impacts of brine leakage, even though agricultural withdrawals of groundwater in the United States are almost three times higher than public and domestic withdrawals.

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