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Survival and activity of an indigenous iron-reducing microbial community from MX80 bentonite in high temperature / low water environments with relevance to a proposed method of nuclear waste disposal

Lookup NU author(s): Katie Gilmour, Dr Colin Davie, Professor Neil GrayORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

MX80 bentonite clay has been selected as the buffer and backfill in a proposed method for long-term deep geological storage of nuclear waste. Extensive studies have been carried out on the geomechanical properties of the clay; however, it is not clear what effect microbes, specifically iron-reducing bacteria, will have on its ability to function as an affective barrier. Iron-reducing bacteria can reduce structural or external Fe(III) to Fe(II) and have been previously identified in the indigenous microbial community of MX80 bentonite. Experiments to assess bacterial survival at the high temperature and low water conditions likely to exist in the repository were carried out at different temperatures with the addition of steel to represent a nuclear waste canister. The resulting microbial enrichments were analysed, and mineralogical and geomechnical analysis was carried out on the clay. Microbial sequencing revealed that iron-reducing bacteria, and other indigenous species can survive these conditions in MX80 bentonite in either an active or dormant state. Microbial influenced mineralogical changes may lead to a loss of silica from the clay and reduction of Fe(III) to Fe(II). These changes could alter the ability of the clay to act as an effective barrier in nuclear waste disposal. Furthermore, evidence of reduced steel corrosion when microbes were present suggested that microbial activity may lead to either a protective coating on the steel or depletion of oxygen to slow corrosion. The production of such a layer would benefit nuclear waste disposal by inhibiting corrosion of a metal waste canister.


Publication metadata

Author(s): Gilmour KA, Davie CT, Gray N

Publication type: Article

Publication status: Published

Journal: Science of the Total Environment

Year: 2022

Volume: 814

Print publication date: 25/03/2022

Online publication date: 24/12/2021

Acceptance date: 20/12/2021

Date deposited: 05/01/2022

ISSN (print): 0048-9697

ISSN (electronic): 1879-1026

Publisher: Elsevier BV

URL: https://doi.org/10.1016/j.scitotenv.2021.152660

DOI: 10.1016/j.scitotenv.2021.152660


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Funding

Funder referenceFunder name
EPSRC

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