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Berlin Brandenburg

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  • 1
    Language: English
    Description: Although changes in the bulk electrical conductivity in aquifers have been attributed to microbial activity, electrical conductivity has never been used to infer biogeochemical reaction rates quantitatively. To explore the use of electrical conductivity to measure reaction rates, we conducted iron oxide reduction experiments of increasing biological complexity. To quantify reaction rates, we proposed composite reactions that incorporated the stiochiometry of five different types of reactions: redox, acid-based, sorption, dissolution/precipitation, and biosynthesis. In batch and column experiments, such reaction stiochiometries inferred from a few chemical measurements allowed quantification of the Fe-oxide reduction rate based on changes in electrical conductivity. The relationship between electrical conductivity and fluid chemistry did not hold during the latter stages of the column experiment when electrical conductivity increased while fluid chemistry remained constant. Growth of an electrically conductive biofilm could explain this late stage electrical conductivity increase. This work demonstrates that measurements of electrical conductivity and flow rate, combined with a few direct chemical measurements, can be used to quantify biogeochemical reaction rates in controlled laboratory situations and may be able to detect the presence of biofilms.
    Keywords: Kinetics, Biotic, Abiotic, Geophysical, Quantifying ; 54 Environmental Sciences Kinetics, Biotic, Abiotic, Geophysical, Quantifying
    Source: University of North Texas
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  • 2
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    Pennsylvania State University
    Language: English
    Description: To provide the scientific understanding required to allow DOE sites to incorporate relevant biological, chemical, and physical processes into decisions concerning environmental remediation, a fundamental understanding of the controls on micro-organism growth in the subsurface is necessary. Specifically, mobility of metals in the environment, including chromium, technetium and uranium, is greatly affected by the process of dissimilatory metal reduction (DMR), which has been shown to be an important biological activity controlling contaminant mobility in the subsurface at many DOE sites. Long-term maintenance of DMR at constant rates must rely upon steady fluxes of electron donors to provide the maintenance energy needed by organisms such as Geobacter sulfurreducens to maintain steady state populations in the subsurface.
    Keywords: 09 Biomass Fuels ; Metal Reduction, Microbial Survival, Energy Metabolism ; 54 Environmental Sciences Metal Reduction, Microbial Survival, Energy Metabolism
    Source: University of North Texas
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  • 3
    Language: English
    Description: This work examined and quantified processes controlling changes in the transport characteristics of natural fractures, subjected to coupled thermal-mechanical-chemical (TMC) effects. Specifically, it examined the effects of mineral dissolution and precipitation mediated by mechanical effects, using laboratory through-flow experiments concurrently imaged by X-ray CT. These were conducted on natural and artificial fractures in cores using water as the permeant. Fluid and mineral mass balances are recorded and are correlated with in-sample saturation, porosity and fracture aperture maps, acquired in real-time by X-ray CT-imaging at a maximum spatial resolution of 15-50 microns per pixel. Post-test, the samples were resin-impregnated, thin-sectioned, and examined by microscopy to define the characteristics of dissolution and precipitation. The test-concurrent X-ray imaging, mass balances, and measurements of permeability, together with the post-test microscopy, were used to define dissolution/precipitation processes, and to constrain process-based models. These models define and quantify key processes of pressure solution, free-face dissolution, and shear-dilation, and the influence of temperature, stress level, and chemistry on the rate of dissolution, its distribution in space and time, and its influence on the mechanical and transport properties of the fracture.
    Keywords: Geochemistry ; Saturation ; Temperature Dependence ; Dissolution ; 58 Geosciences ; Geologic Fractures ; Porosity ; Rock Mechanics ; Permeability ; Minerals ; Precipitation
    Source: University of North Texas
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  • 4
    Language: English
    Description: No abstract prepared.
    Keywords: Geology ; Geothermal ; Radionuclide Interation ; 58 Geosciences ; Carbon Dioxide ; Geochemistry ; Water ; Degassing ; Carbon Sequestration ; Interactions Hydrogen ; Nanoscience ; Hydrogen ; Water-Rock ; Weathering
    Source: University of North Texas
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