Laboratory simulation of an oxidizing perturbation in a deep granite environment |
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Authors: | Laurent TrotignonValrie Michaud Jean-Eric Lartigue Jean-Paul AmbrosiLaurent Eisenlohr Lise GriffaultMichel de Combarieu Sylvie Daumas |
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Institution: | 1 Commissariat à l’Energie Atomique, DEN/DED, Centre d’Etudes de Cadarache, 13108 Saint-Paul lez Durance, France 2 CNRS, CEREGE, UMR 6635, Europôle Méditerranéen de l’Arbois, BP 80, 13545 Aix-en-Provence Cedex 04, France 3 Andra, Service Hydro-Géochimie, Parc de la Croix Blanche, 1-7 rue Jean Monnet, 92298 Châtenay-Malabry Cedex, France 4 Compagnie Française de Géothermie, Groupe BRGM, 117 avenue de Luminy, 13009 Marseille, France |
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Abstract: | An experiment designed to study oxidizing perturbations in deep crystalline rock, a potential host for nuclear waste disposal, was conducted. This experiment simulated a fracture surface in contact with circulating groundwater, in which dissolved oxygen was injected periodically. Major physicochemical and biological parameters were monitored during this 1-yr experiment. Modeling of the results indicates that the kinetics of oxygen uptake may be represented by a simple steady-state rate law combining enzymatic catalysis (Monod) and a first-order rate law. Combined chemical and biological data demonstrate the coupling of organic/inorganic processes during the uptake of dissolved oxygen and the progressive return to reducing conditions. Timescales for these stages are discussed. Experimental results also suggest that iron-reducing bacteria, which are robust and well-adapted microorganisms, play a key role in these interfacial processes. These results show that an operational definition of the “redox buffering capacity” in a granitic medium cannot ignore the effect of bacteria and therefore the controls on bacterial substrates (organic carbon, H2, CH4, CO2). |
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