Characterization of microbial communities in sedimentary clays used for deep geological repository


Characterization of microbial communities in sedimentary clays used for deep geological repository

Wei, T.-S.; Matschiavelli, N.; Sushko, V.; Schleicher, A. M. S.; Cherkouk, A.

A deep geological repository (DGR) is a multi-barrier concept that has been a solution to store high-level nuclear waste (HLW). The natural Opalinus clay rocks are one of the candidates for entire DGR due to their unique geochemical features. However, the first direct barrier is bentonites which are the processed clay materials that embed metal containers for HLW. The microbial impact, especially when porewater is introduced into DGR and H2 gas is generated via anoxic corrosion of containers, on these clay barriers remains elusive.
Here, we showed that mineral composition between sandy and shaley Opalinus clays from underground laboratory Mt. Terri were discernible. The microbial diversity of Opalinus clay, together with Calcigel bentonite (CaB) and previously published data from Opalinus porewater and Bavarian bentonite (B25) were significantly distinct principal coordinates analysis. The CaB supported diverse phyla, whereas other communities were dominated by Proteobacteria. Moreover, genus Desulfobacterium (phylum Desulfobacterota) was largely enriched by injecting H2 gas into the porewater communities; however, in the B25 incubated with synthetic Opalinus porewater, genera Desulfosporosinus and Pelotomaculum (phylum Firmicutes) were enriched by H2 gas. Interestingly, the signature of these bacteria was also identified in the sandy clay and CaB communities, indicating that these two communities have the capacity in alleviating H2 pressure accumulated in DGR.
In the future, microcosm setup with porewater and H2 gas will be applied to Opalinus clay and CaB samples with different compacted dry density. The understanding of impact on these clay materials will be achieved via metagenome and geochemical analyses.

Keywords: Bentonite; Opalinus clay; Deep geological repository (DRG); Nuclear waste management; 16S amplicon sequencing

  • Poster
    18th International Symposium on Microbial Ecology, 14.-19.08.2022, Lausanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-35057
Publ.-Id: 35057