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Long-term tracking of the microbiology of uranium-amended water-saturated bentonite microcosms: A mechanistic characterization of U speciation

Mar Morales-Hidalgo, Cristina Povedano-Priego, Marcos F. Martinez-Moreno, Jesus Ojeda Ledo Orcid Logo, Fadwa Jroundi, Mohamed L. Merroun

Journal of Hazardous Materials, Volume: 476, Start page: 135044

Swansea University Author: Jesus Ojeda Ledo Orcid Logo

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DOI (Published version): 10.1016/j.jhazmat.2024.135044

Abstract

Deep geological repositories (DGRs) stand out as one of the optimal options for managing high-level radioactive waste (HLW) such as uranium (U) in the near future. Here, we provide novel insights into microbial behavior in the DGR bentonite barrier, addressing potential worst-case scenarios such as...

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Published in: Journal of Hazardous Materials
ISSN: 0304-3894
Published: Elsevier BV 2024
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URI: https://cronfa.swan.ac.uk/Record/cronfa66892
Abstract: Deep geological repositories (DGRs) stand out as one of the optimal options for managing high-level radioactive waste (HLW) such as uranium (U) in the near future. Here, we provide novel insights into microbial behavior in the DGR bentonite barrier, addressing potential worst-case scenarios such as waste leakage (e.g., U) and groundwater infiltration of electron rich donors in the bentonite. After a three-year anaerobic incubation, Illumina sequencing results revealed a bacterial diversity dominated by anaerobic and spore-forming micro-organisms mainly from the phylum Firmicutes. Highly U tolerant and viable bacterial isolates from the genera Peribacillus, Bacillus, and some SRB such as Desulfovibrio and Desulfosporosinus, were enriched from U-amended bentonite. The results obtained by XPS and XRD showed that U was present as U(VI) and as U(IV) species. Regarding U(VI), we have identified biogenic U(VI) phosphates, U(UO2)·(PO4)2, located in the inner part of the bacterial cell membranes in addition to U(VI)-adsorbed to clays such as montmorillonite. Biogenic U(IV) species as uraninite may be produced as result of bacterial enzymatic U(VI) reduction. These findings suggest that under electron donor-rich water-saturation conditions, bentonite microbial community can control U speciation, immobilizing it, and thus enhancing future DGR safety if container rupture and waste leakage occurs.
Keywords: DGR; bentonite slurry; uranium; long-term incubation, microbial diversity; sulfate reducing bacteria
College: Faculty of Science and Engineering
Funders: This study was supported by the grant RTI2018–101548-B-I00 “ERDF A way of making Europe” to MLM from the “Ministerio de Ciencia, Innovación y Universidades” (Spanish Government). The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 847593 to MLM and the grant FPU20/00583 to the first author from the “Ministerio de Universidades” (Spanish Government).
Start Page: 135044

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