Impact of the electron donor on in situ microbial nitrate reduction in Opalinus Clay: results from the Mont Terri rock laboratory (Switzerland)

Autor: Hugo Moors, Elie Valcke, Steven Smets, Joe S. Small, Achim Albrecht, Bernhard Schwyn, Pierre De Cannière, Natalie Leys, Charles Wittebroodt, Nele Bleyen
Přispěvatelé: Agence Nationale pour la Gestion des Déchets Radioactifs (ANDRA), PSE-ENV/SEDRE/LETIS, Institut de Radioprotection et de Sûreté Nucléaire (IRSN)
Jazyk: angličtina
Rok vydání: 2017
Předmět:
Zdroj: Swiss Journal of Geosciences
Swiss Journal of Geosciences, Springer, 2017, 110 (110), pp.355-374. ⟨10.1007/s00015-016-0256-x⟩
ISSN: 1661-8726
1661-8734
DOI: 10.1007/s00015-016-0256-x⟩
Popis: International audience; At the MontTerri rock laboratory (Switzerland), an in situ experiment is being carried out to examine the fate of nitrate leaching from nitrate-containing bituminized radioactive waste, in a clay host rock for geological disposal. Such a release of nitrate may cause a geochemical perturbation of the clay, possibly affecting some of the favorable characteristics of the host rock. In this in situ experiment, combined transport and reactivity of nitrate is studied Inside anoxic and water-saturated chambers in a borehole in the Opalinus Clay. Continuous circulation of the solution fromthe borehole to the surface equipment allows a regular sampling and online monitoring of its chemical composition. In this paper, in situ microbial nitrate reduction in the Opalinus Clay is discussed, in the presence or absence of additional electron donors relevant for the disposal concept and likely to be released from nitrate-containing bituminized radioactive waste: acetate (simulating bitumen degradation products) and H2 (originating from radiolysis and corrosion in the repository). The results of these tests indicate that in case microorganisms would be active in the repository or the surrounding clay—microbial nitrate reduction can occur using electron donors naturally present in the clay (e.g. pyrite, dissolved organic matter). Nevertheless, non-reactive transport of nitrate in the clay is expected to be the main process. In contrast, when easily oxidizable electron donors would be available (e.g. acetate and H2), the microbial activity will be strongly stimulated. Both in the presence of H2 and acetate, nitrite and nitrogenous gases are predominantly produced, although some ammonium can also be formed when H2 is present. The reduction of nitrate in the clay could have an impact on the redox conditions in the pore-water and might also lead to a gas-related perturbation of the host rock, depending on the electron donor used during denitrification.
Databáze: OpenAIRE
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