Factors Controlling In Situ Uranium and Technetium Bio-Reduction and Reoxidation at the NABIR Field Research Center

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Summary of Recent Field Testing: Extensive in situ (in ground) field testing using the push-pull method has demonstrated that indigenous microorganisms in the shallow (< 8 m) aquifer in FRC Areas 1 and 2 are capable of coupling the oxidation/fermentation of injected ethanol, glucose, or acetate to the reduction of U(VI) and Tc(VII). Despite highly variable initial (prior to testing) contaminant concentrations (pH: 3.3-7.2; Nitrate: 0.1-140 mM; U(VI): 1-12 uM; Tc(VII): 200-15000 pM), sequential donor additions resulted in increased rates of microbial activity (Denitrification: 01.-4.0 mM/hr; sulfate reduction: 0- 0.03 mM/hr; U(VI) reduction: 10-4 to 10-3 uM/hr; Tc(VII) reduction: 4-150 ... continued below

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Istok, Jonathan; Krumholz, L; McKinley, J. & Gu, B. May 5, 2004.

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Summary of Recent Field Testing: Extensive in situ (in ground) field testing using the push-pull method has demonstrated that indigenous microorganisms in the shallow (< 8 m) aquifer in FRC Areas 1 and 2 are capable of coupling the oxidation/fermentation of injected ethanol, glucose, or acetate to the reduction of U(VI) and Tc(VII). Despite highly variable initial (prior to testing) contaminant concentrations (pH: 3.3-7.2; Nitrate: 0.1-140 mM; U(VI): 1-12 uM; Tc(VII): 200-15000 pM), sequential donor additions resulted in increased rates of microbial activity (Denitrification: 01.-4.0 mM/hr; sulfate reduction: 0- 0.03 mM/hr; U(VI) reduction: 10-4 to 10-3 uM/hr; Tc(VII) reduction: 4-150 pM/hr) in all wells tested. Tc(VII) reduction and denitrification proceeded concomitantly in all tests. U(VI) reduction was concomitant with Fe(II) production in Area 1 but little Fe(II) was detected under sulfate reducing conditions in Area 2. Reoxidation of U(IV) (precipitated in the vicinity of the wells during previous tests) but not Tc(IV) was observed when injected test solutions contained initial nitrate concentrations > {approx} 20 mM. Field data and laboratory studies suggest that U(IV) is likely oxidized by Fe(III) minerals produced by enzymatic Fe(II) oxidation or by Fe(II) oxidation by nitrite. U(IV) reoxidation rates (10-3 to 10-2 uM/hr) were somewhat larger than U(VI) reduction rates indicating that sustained nitrate removal will be necessary to maintain the stability of U(IV) in this environment.

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  • Report No.: NABIR-1022810-2004
  • Grant Number: None
  • DOI: 10.2172/893691 | External Link
  • Office of Scientific & Technical Information Report Number: 893691
  • Archival Resource Key: ark:/67531/metadc873599

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  • May 5, 2004

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 7, 2016, 1:31 p.m.

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Istok, Jonathan; Krumholz, L; McKinley, J. & Gu, B. Factors Controlling In Situ Uranium and Technetium Bio-Reduction and Reoxidation at the NABIR Field Research Center, report, May 5, 2004; United States. (digital.library.unt.edu/ark:/67531/metadc873599/: accessed December 14, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.