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

Description: 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.
Date: May 5, 2004
Creator: Istok, Jonathan; Krumholz, L; McKinley, J. & Gu, B.
Partner: UNT Libraries Government Documents Department

Control of biologically active degradation zones by vertical heterogeneity: Applications in fractured media. 1998 annual progress report

Description: 'The objective of this research is to determine the relationship between biologically active contaminant degradation zones in a fractured, subsurface medium and vertical geological heterogeneities. The research is being performed on samples collected from the Test Area North (TAN) site at the Idaho National Engineering and Environmental Laboratory (INEEL) where a dissolved trichloroethylene (TCE) plume is migrating in the basalts and interbed sediments of the Eastern Snake River Plain (ESRP) aquifer. Results are leading to an enhanced understanding of the constraints placed on the activities and distribution of TCE-degrading organisms by the geochemical and hydrological environment. This understanding allows better decisions to be made regarding the use of remedial technologies such as natural attenuation and in-situ bioremediation at geologically complex waste sites. Through this research, investigations conducted by the DOE Subsurface Science Program at TAN have been extended in order to develop a mechanistic understanding of the coupled geomicrobial and hydrogeochemical processes that are necessary to predict field-scale intrinsic degradation rates of TCE. The research objective is being accomplished by characterizing paired cores and water samples from boreholes located in differing geochemical and flow environments within the plume. Analysis of these samples will allow the determination of the spatial correlation between microbial degradation and preferred flow paths for the contaminant and required electron donors and acceptors. A combination of traditional microbiological methods (e.g., enrichments) and molecular tools are being used to characterize the indigenous microbial communities. This report summarizes work conducted after 1.5 years of a three year project.'
Date: June 1, 1998
Creator: Colwell, F.S.; Smith, R.; McKinley, J.P.; Fredrickson, J.K.; Onstott, T.C. & Reysenbach, A.L.
Partner: UNT Libraries Government Documents Department

Control of biologically active degradation zones by vertical heterogeneity: Applications in fractured media. 1997 annual progress report

Description: 'The objective of this research is to determine the relationship between of biologically active contaminant degradation zones in a fractured, subsurface medium and vertical geological heterogeneities. The research is being performed on samples collected from the Test Area North (TAN) site at the Idaho National Engineering and Environmental Laboratory (INEEL) where a dissolved trichloroethylene (TCE) plume is migrating in the basalts and interbed sediments of the Eastern Snake River Plain (ESRP) aquifer. Research results are leading to an enhanced understanding of the constraints that the geochemical and hydrological environment place on the activities and distribution of TCE-degrading organisms in this fractured subsurface medium. Enhanced understanding allows better decisions to be made regarding the use of remedial technologies such as natural attenuation and in situ bioremediation at geologically complex waste sites. Through this research, investigations conducted by the Subsurface Science Program (SSP) at TAN are being extended in order to develop a mechanistic understanding of the coupled geomicrobial and hydrogeochemical processes that are necessary to predict the field-scale intrinsic degradation rates of TCE. The research objective is being accomplished by characterizing paired cores and water samples from boreholes located in differing geochemical and flow environments within the plume. Analysis of these samples will allow the determination of the spatial correlation and microbial characterization. The results presented in this report consist primarily of TAN-33 data as many of those analyses have been completed. Nearly all of the TAN-37 data has yet to be acquired. It should be noted that most of the cores were collected from zones that consist of relatively competent, massive basalt. This was because the authors were doubtful about the quality of samples obtained from rubble zones due to potential alteration by the drilling fluids. Thus, microbiological results on the core samples likely represent a conservative estimate of the ...
Date: November 1, 1997
Creator: Colwell, F.S.; Smith, R.W.; McKinley, J.; Fredrickson, J.; Onstott, T.C. & Reysenbach, A.L.
Partner: UNT Libraries Government Documents Department

Control of biologically Active Degradation Zones By Vertical Heterogeneity : Applications In Fractured Media

Description: The key objective of this research was to determine the distribution of biologically active contaminant degradation zones in a fractured, subsurface medium with respect to vertical heterogeneities. Our expectation was that hydrogeological properties would determine the size, diversity, and activities of microbial communities in fractured basalt by controlling the fluxes and concentrations of aqueous constituents upon which these communities depend. We expected that microorganisms would be more abundant, of greater diversity, and of relatively higher metabolic activity within zones of high permeability that contain favorable concentrations of electron donors and acceptors; the composition and flux of these solutes will reflect the spatial continuity of interflow fracture and rubble zones. We further expected that the composition and dynamics of microbial communities associated with rock surfaces in fractured basalt aquifers could be predicted by the incubation of a native rock substratum placed at discreet, isolated intervals within a borehole.
Date: 2001
Creator: Colwell, F. S.; Smith, R.; Fredrickson, J. K.; Reysenbach, A.-L.; Mckinley, J. P. & Onstott, T. C.
Partner: UNT Libraries Government Documents Department

Feasibility Study of Supercritical Light Water Cooled Reactors for Electric Power Production

Description: The supercritical water reactor (SCWR) has been the object of interest throughout the nuclear Generation IV community because of its high potential: a simple, direct cycle, compact configuration; elimination of many traditional LWR components, operation at coolant temperatures much higher than traditional LWRs and thus high thermal efficiency. It could be said that the SWR was viewed as the water counterpart to the high temperature gas reactor.
Date: February 13, 2005
Creator: MacDonald, Philip; Buongiorno, Jacopo; Sterbentz, James; Davis, Cliff; Witt, Robert; Was, Gary et al.
Partner: UNT Libraries Government Documents Department

Factors Controlling In Situ Uranium and Technetium Bioreductionat the NABIR Field Research Center

Description: This research hypotheses is: (1) Indigenous microorganisms in the shallow aquifer at the FRC have the capability to reduce U(VI) and Tc(VII) but rates are limited by--Scarce electron donor, Low pH and potentially toxic metals, and High nitrate. (2) U(VI) and Tc(VII) reduction rates can be increased by--Successive donor additions, Raising pH to precipitate toxic metals, and Adding humics to complex toxic metals and serve as electron shuttles.
Date: March 17, 2004
Creator: Istok, J.; Jones, J.; Park, M.; Sapp, M.; Selko, E.; Laughman, R. et al.
Partner: UNT Libraries Government Documents Department