No signs of microbial-influenced corrosion of cast iron and copper in bentonite microcosms after 400 days

• Published in: Chemosphere (Oxford) 2024-09, Vol.364, p.143007, Article 143007
• Main Authors: Sushko, Vladyslav, Dressler, Magdalena, Wei, Sean Ting-Shyang, Neubert, Tom, Kühn, Luise, Cherkouk, Andrea, Stumpf, Thorsten, Matschiavelli, Nicole
• Format: Article
• Language: English
• Subjects: Bentonite; Cast iron; Copper; Deep geological repository; Microbial diversity; Microbiologically influenced corrosion
• ISSN: 0045-6535; 1879-1298; 1879-1298
• DOI: 10.1016/j.chemosphere.2024.143007

High-level radioactive waste needs to be safely stored for a long time in a deep geological repository by using a multi-barrier system. In this system, suitable barrier materials are selected that ideally show long-term stability to prevent early radionuclide release into the biosphere. In this study, different container matals (copper and cast iron) and pore water compositions (Opalinus Clay pore water and saline cap rock solution) were combined with Bavarian bentonite in static batch experiments to investigate microbial-influenced corrosion. The increasing concentration of iron and copper in the solution as well as detected corrosion products on the metal surface are indicative of anaerobic corrosion of the respective metals during an incubation of 400 days at 37 °C. However, although the intrinsic microbial bentonite community was stimulated with either lactate or H2, an acceleration of cast iron- and copper corrosion did not occur. Furthermore, neither corrosive bacteria nor conventional bacterial corrosion products, such as metal sulfides, were detected in any of the analyzed samples. The analyses of geochemical parameters (e.g. ferrous iron-, iron-, copper- and potassium concentrations as well as redox potentials) showed significant changes in some cast iron- and copper-containing setups, but these changes did not correlate with the microbial community structure in the respective microcosms, as confirmed by statistical analyses. Hence, the analyzed Bavarian bentonite (type B25) showed no significant contribution to cast iron and copper corrosion under the applied conditions after 400 days of incubation. From this perspective, bentonite B25 could be a suitable candidate as a geotechnical barrier in future repositories. [Display omitted] •Selecting geotechnical barrier material (e.g. bentonite) relevant for the storage of nuclear waste remains important.•Microcosms were used to analyze the microbial effects of B25 bentonite on metal corrosion.•Indigenous microorganisms in B25 bentonite did not affect cast iron- and copper corrosion.•Corrosion was mainly attributed to abiotic factors of Opalinus Clay pore water and cap rock solution.•Statistical analysis (e.g. dbRDA) is a powerful tool to evaluate the microbial influence.