Ex and in situ reactivity and sorption of selenium in Opalinus clay in the presence of a selenium reducing microbial community

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Authors

Institutes & Expert groups

  • FANC-AFCN - Federaal agentschap voor nucleaire controle-Agence fédérale de contrôle nucléaire
  • NLL - National Nuclear Laboratory
  • ANDRA - National Agency for Radioactive Waste Management
  • SCK CEN
  • IRSN - Institute for Radioprotection and Nuclear Safety - Institut Radioprotection Sûreté Nucléaire

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DOI

Abstract

79Se is a critical radionuclide concerning the safety of deep geological disposal of certain radioactive wastes in clay-rich formations. To study the fate of selenium oxyanions in clayey rocks in the presence of a selenium reducing microbial community, in situ tests were performed in the Opalinus Clay at the Mont Terri Rock Laboratory (Switzerland). Furthermore, biotic and abiotic batch tests were performed to assess Se(VI) and Se(IV) reactivity in the presence of Opalinus Clay and/or stainless steel, in order to support the interpretation of the in situ tests. Geochemical modeling was applied to simulate Se(VI) reduction, Se(IV) sorption and solubility, and diffusion processes. This study shows that microbial activity is required to transform Se(VI) into more reduced and sorbing Se species in the Opalinus Clay, while in abiotic conditions, Se(VI) remains unreactive. On the other hand, Se(IV) can be reduced by microorganisms but can also sorb in the presence of clay without microorganisms. In situ microbial reduction of Se oxyanions can occur with electron donors provided by the clay itself. If microorganisms would be active in the clay surrounding a disposal facility, microbial reduction of leached Se could thus contribute to the overall retention of Se in clayey host rocks.

Details

Original languageEnglish
Article number11070757
Pages (from-to)1-33
Number of pages33
JournalMinerals
Volume11
Issue number757
DOIs
Publication statusPublished - 13 Jul 2021

Keywords

  • Diffusion, Reactivity, Clay, Mont Terri, Selenium reduction, Sorption, Opalinus clay, In situ, Batch tests

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