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Martinez-Moreno MF, Povedano-Priego C, Mumford AD, Morales-Hidalgo M, Mijnendonckx K, Jroundi F, Ojeda JJ, Merroun ML. Microbial responses to elevated temperature: Evaluating bentonite mineralogy and copper canister corrosion within the long-term stability of deep geological repositories of nuclear waste. Sci Total Environ 2024; 915:170149. [PMID: 38242445 DOI: 10.1016/j.scitotenv.2024.170149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 01/09/2024] [Accepted: 01/11/2024] [Indexed: 01/21/2024]
Abstract
Deep Geological Repositories (DGRs) consist of radioactive waste contained in corrosion-resistant canisters, surrounded by compacted bentonite clay, and buried few hundred meters in a stable geological formation. The effects of bentonite microbial communities on the long-term stability of the repository should be assessed. This study explores the impact of harsh conditions (60 °C, highly-compacted bentonite, low water activity), and acetate:lactate:sulfate addition, on the evolution of microbial communities, and their effect on the bentonite mineralogy, and corrosion of copper material under anoxic conditions. No bentonite illitization was observed in the treatments, confirming its mineralogical stability as an effective barrier for future DGR. Anoxic incubation at 60 °C reduced the microbial diversity, with Pseudomonas as the dominant genus. Culture-dependent methods showed survival and viability at 60 °C of moderate-thermophilic aerobic bacterial isolates (e.g., Aeribacillus). Despite the low presence of sulfate-reducing bacteria in the bentonite blocks, we proved their survival at 30 °C but not at 60 °C. Copper disk's surface remained visually unaltered. However, in the acetate:lactate:sulfate-treated samples, sulfide/sulfate signals were detected, along with microbial-related compounds. These findings offer new insights into the impact of high temperatures (60 °C) on the biogeochemical processes at the compacted bentonite/Cu canister interface post-repository closure.
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Affiliation(s)
| | | | - Adam D Mumford
- Department of Chemical Engineering, Faculty of Science and Engineering, Swansea University, Swansea, United Kingdom
| | - Mar Morales-Hidalgo
- Faculty of Sciences, Department of Microbiology, University of Granada, Granada, Spain
| | | | - Fadwa Jroundi
- Faculty of Sciences, Department of Microbiology, University of Granada, Granada, Spain
| | - Jesus J Ojeda
- Department of Chemical Engineering, Faculty of Science and Engineering, Swansea University, Swansea, United Kingdom
| | - Mohamed L Merroun
- Faculty of Sciences, Department of Microbiology, University of Granada, Granada, Spain
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Ruiz-Fresneda MA, Morales-Hidalgo M, Povedano-Priego C, Jroundi F, Hidalgo-Iruela J, Cano-Cano M, Pérez-Muelas E, Merroun ML, Martín-Sanchez I. Unlocking the key role of bentonite fungal isolates in tellurium and selenium bioremediation and biorecovery: Implications in the safety of radioactive waste disposal. Sci Total Environ 2024; 912:169242. [PMID: 38072256 DOI: 10.1016/j.scitotenv.2023.169242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 11/27/2023] [Accepted: 12/07/2023] [Indexed: 01/18/2024]
Abstract
Research on eco-friendly bioremediation strategies for mitigating the environmental impact of toxic metals has gained attention in the last years. Among all promising solutions, bentonite clays, to be used as artificial barriers to isolate radioactive wastes within the deep geological repository (DGR) concept, have emerged as effective reservoir of microorganisms with remarkable bioremediation potential. The present study aims to investigate the impact of bentonite fungi in the speciation and mobility of selenium (Se) and tellurium (Te), as natural analogues 79Se and 132Te present in radioactive waste, to screen for those strains with bioremediation potential within the context of DGR. For this purpose, a multidisciplinary approach combining microbiology, biochemistry, and microscopy was performed. Notably, Aspergillus sp. 3A demonstrated a high tolerance to Te(IV) and Se(IV), as evidenced by minimal inhibitory concentrations of >16 and >32 mM, respectively, along with high tolerance indexes. The high metalloid tolerance of Aspergillus sp. 3A is mediated by its capability to reduce these mobile and toxic elements to their elemental less soluble forms [Te(0) and Se(0)], forming nanostructures of various morphologies. Advanced electron microscopy techniques revealed intracellular Te(0) manifesting as amorphous needle-like nanoparticles and extracellular Te(0) forming substantial microspheres and irregular accumulations, characterized by a trigonal crystalline phase. Similarly, Se(0) exhibited a diverse array of morphologies, including hexagonal, irregular, and needle-shaped structures, accompanied by a monoclinic crystalline phase. The formation of less mobile Te(0) and Se(0) nanostructures through novel and environmentally friendly processes by Aspergillus sp. 3A suggests it would be an excellent candidate for bioremediation in contaminated environments, such as the vicinity of deep geological repositories. It moreover holds immense potential for the recovery and synthesis of Te and Se nanostructures for use in numerous biotechnological and biomedical applications.
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Affiliation(s)
| | - Mar Morales-Hidalgo
- University of Granada, Department of Microbiology, Campus Fuentenueva, 18071 Granada, Spain
| | | | - Fadwa Jroundi
- University of Granada, Department of Microbiology, Campus Fuentenueva, 18071 Granada, Spain
| | - Javier Hidalgo-Iruela
- University of Granada, Department of Microbiology, Campus Fuentenueva, 18071 Granada, Spain
| | - Mónica Cano-Cano
- University of Granada, Department of Microbiology, Campus Fuentenueva, 18071 Granada, Spain
| | - Eduardo Pérez-Muelas
- University of Granada, Department of Microbiology, Campus Fuentenueva, 18071 Granada, Spain
| | - Mohamed Larbi Merroun
- University of Granada, Department of Microbiology, Campus Fuentenueva, 18071 Granada, Spain
| | - Inés Martín-Sanchez
- University of Granada, Department of Microbiology, Campus Fuentenueva, 18071 Granada, Spain
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Povedano-Priego C, Jroundi F, Morales-Hidalgo M, Pinel-Cabello M, Peula-Ruiz E, Merroun ML, Martin-Sánchez I. Unveiling fungal diversity in uranium and glycerol-2-phosphate-amended bentonite microcosms: Implications for radionuclide immobilization within the Deep Geological Repository system. Sci Total Environ 2024; 908:168284. [PMID: 37924892 DOI: 10.1016/j.scitotenv.2023.168284] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 10/31/2023] [Accepted: 10/31/2023] [Indexed: 11/06/2023]
Abstract
Uranium (U) represents the preeminent hazardous radionuclide within the context of nuclear waste repositories. Indigenous microorganisms in bentonite can influence radionuclide speciation and migration in Deep Geological Repositories (DGRs) for nuclear waste storage. While bacterial communities in bentonite samples have been extensively studied, the impact of fungi has been somewhat overlooked. Here, we investigate the geomicrobiological processes in bentonite microcosms amended with uranyl nitrate and glycerol-2-phosphate (G2P) for six-month incubation. ITS sequencing revealed that the fungal community was mainly composed of Ascomycota (96.6 %). The presence of U in microcosms enriched specific fungal taxa, such as Penicillium and Fusarium, potentially associated with uranium immobilization mechanisms. Conversely, the amendment of U into G2P-suplemented samples exhibited minimal impact, resulting in a fungal community akin to the control group. Several fungal strains were isolated from bentonite microcosms to explore their potential in the U biomineralization, including Fusarium oxysporum, Aspergillus sp., Penicillium spp., among others. High Annular Angle Dark-Field Scanning Transmission Electron Microscopy (HAADF) analyses showed the capacity of F. oxysporum B1 to form U-phosphate mineral phases, likely mediated by phosphatase activity. Therefore, our study emphasizes the need to take into account indigenous bentonite fungi in the overall assessment of the impact of microbial processes in the immobilization of U within DGRs environments.
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Affiliation(s)
- Cristina Povedano-Priego
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n 18071, Granada, Spain.
| | - Fadwa Jroundi
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n 18071, Granada, Spain.
| | - Mar Morales-Hidalgo
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n 18071, Granada, Spain.
| | - María Pinel-Cabello
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n 18071, Granada, Spain.
| | - Esther Peula-Ruiz
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n 18071, Granada, Spain.
| | - Mohamed L Merroun
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n 18071, Granada, Spain.
| | - Inés Martin-Sánchez
- Department of Microbiology, University of Granada, Campus Fuentenueva s/n 18071, Granada, Spain.
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Martinez-Moreno MF, Povedano-Priego C, Morales-Hidalgo M, Mumford AD, Ojeda JJ, Jroundi F, Merroun ML. Impact of compacted bentonite microbial community on the clay mineralogy and copper canister corrosion: a multidisciplinary approach in view of a safe Deep Geological Repository of nuclear wastes. J Hazard Mater 2023; 458:131940. [PMID: 37390682 DOI: 10.1016/j.jhazmat.2023.131940] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 06/16/2023] [Accepted: 06/23/2023] [Indexed: 07/02/2023]
Abstract
Deep Geological Repository (DGR) is the preferred option for the final disposal of high-level radioactive waste. Microorganisms could affect the safety of the DGR by altering the mineralogical properties of the compacted bentonite or inducing the corrosion of the metal canisters. In this work, the impact of physicochemical parameters (bentonite dry density, heat shock, electron donors/acceptors) on the microbial activity, stability of compacted bentonite and corrosion of copper (Cu) discs was investigated after one-year anoxic incubation at 30 ºC. No-illitization in the bentonite was detected confirming its structural stability over 1 year under the experimental conditions. The microbial diversity analysis based on 16 S rRNA gene Next Generation Sequencing showed slight changes between the treatments with an increase of aerobic bacteria belonging to Micrococcaceae and Nocardioides in heat-shock tyndallized bentonites. The survival of sulfate-reducing bacteria (the main source of Cu anoxic corrosion) was demonstrated by the most probable number method. The detection of CuxS precipitates on the surface of Cu metal in the bentonite/Cu metal samples amended with acetate/lactate and sulfate, indicated an early stage of Cu corrosion. Overall, the outputs of this study help to better understand the predominant biogeochemical processes at the bentonite/Cu canister interface upon DGR closure.
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Affiliation(s)
| | | | - Mar Morales-Hidalgo
- Department of Microbiology, Faculty of Sciences, University of Granada, Granada, Spain
| | - Adam D Mumford
- Department of Chemical Engineering, Faculty of Science and Engineering, Swansea University, Swansea, United Kingdom
| | - Jesus J Ojeda
- Department of Chemical Engineering, Faculty of Science and Engineering, Swansea University, Swansea, United Kingdom
| | - Fadwa Jroundi
- Department of Microbiology, Faculty of Sciences, University of Granada, Granada, Spain
| | - Mohamed L Merroun
- Department of Microbiology, Faculty of Sciences, University of Granada, Granada, Spain
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Ruiz-Fresneda MA, Martinez-Moreno MF, Povedano-Priego C, Morales-Hidalgo M, Jroundi F, Merroun ML. Impact of microbial processes on the safety of deep geological repositories for radioactive waste. Front Microbiol 2023; 14:1134078. [PMID: 37007474 PMCID: PMC10062484 DOI: 10.3389/fmicb.2023.1134078] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 02/27/2023] [Indexed: 03/18/2023] Open
Abstract
To date, the increasing production of radioactive waste due to the extensive use of nuclear power is becoming a global environmental concern for society. For this reason, many countries have been considering the use of deep geological repositories (DGRs) for the safe disposal of this waste in the near future. Several DGR designs have been chemically, physically, and geologically well characterized. However, less is known about the influence of microbial processes for the safety of these disposal systems. The existence of microorganisms in many materials selected for their use as barriers for DGRs, including clay, cementitious materials, or crystalline rocks (e.g., granites), has previously been reported. The role that microbial processes could play in the metal corrosion of canisters containing radioactive waste, the transformation of clay minerals, gas production, and the mobility of the radionuclides characteristic of such residues is well known. Among the radionuclides present in radioactive waste, selenium (Se), uranium (U), and curium (Cm) are of great interest. Se and Cm are common components of the spent nuclear fuel residues, mainly as 79Se isotope (half-life 3.27 × 105 years), 247Cm (half-life: 1.6 × 107 years) and 248Cm (half-life: 3.5 × 106 years) isotopes, respectively. This review presents an up-to-date overview about how microbes occurring in the surroundings of a DGR may influence their safety, with a particular focus on the radionuclide-microbial interactions. Consequently, this paper will provide an exhaustive understanding about the influence of microorganisms in the safety of planned radioactive waste repositories, which in turn might improve their implementation and efficiency.
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