Rates of microbial hydrogen oxidation and sulfate reduction in Opalinus Clay rock |
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| Institution: | 1. Environmental Microbiology Laboratory, EPFL, Station 6, Lausanne 1015, Switzerland;2. Stream Biofilm and Ecology Research Laboratory, EPFL, Station 2, Lausanne 1015, Switzerland;3. NAGRA, National Cooperative for the Disposal of Radioactive Waste, Hardstrasse 73, Wettingen 5430, Switzerland;1. Institute of Petroleum Engineering, Clausthal University of Technology, Clausthal-Zellerfeld, Germany;2. Laboratoire d''Energétique et de Mécanique Théorique et Appliquée, CNRS-UMR 7563, Université de Lorraine, Vand?uvre-lès-Nancy, France;1. Al-Farabi Kazakh National University, Almaty, Kazakhstan;2. Laboratoire d''Energétique et de Mécanique Théorique et Appliquée, CNRS/Université de Lorraine, France;1. Institute of Biotechnology and Department of Biosciences, University of Helsinki, Helsinki, Finland;1. GFZ German Research Centre for Geosciences - Section 5.3 Hydrogeology, Telegrafenberg, 14473 Potsdam;2. GFZ German Research Centre for Geosciences - Centre for Geological Storage CGS, Telegrafenberg, 14473 Potsdam;1. Huazhong Agricultural University, 1 Shi-zi-shan Street, 430070 Wuhan, China;2. Colorado Mesa University, Wubben Science Bldg. 223D, Grand Junction, CO 81501, United States |
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| Abstract: | Hydrogen gas (H2) may be produced by the anoxic corrosion of steel components in underground structures, such as geological repositories for radioactive waste. In such environments, hydrogen was shown to serve as an electron donor for autotrophic bacteria. High gas overpressures are to be avoided in radioactive waste repositories and, thus, microbial consumption of H2 is generally viewed as beneficial. However, to fully consider this biological process in models of repository evolution over time, it is crucial to determine the in situ rates of microbial hydrogen oxidation and sulfate reduction. These rates were estimated through two distinct in situ experiments, using several measurement and calculation methods. Volumetric consumption rates were calculated to be between 1.13 and 1.93 μmol cm?3 day?1 for H2, and 0.14 and 0.20 μmol cm?3 day?1 for sulfate. Based on the stoichiometry of the reaction, there is an excess of H2 consumed, suggesting that it serves as an electron donor to reduce electron acceptors other than sulfate, and/or that some H2 is lost via diffusion. These rate estimates are critical to evaluate whether biological H2 consumption can negate H2 production in repositories, and to determine whether sulfate reduction can consume sulfate faster than it is replenished by diffusion, which could lead to methanogenic conditions. |
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| Keywords: | Deep geological repository Mt Terri Underground Rock Laboratory Anoxic steel corrosion Sulfate-reducing bacteria Geomicrobiology |
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