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Ammar A, Nouira A, El Mouridi Z, Boughribil S. Recent trends in the phytoremediation of radionuclide contamination of soil by cesium and strontium: Sources, mechanisms and methods: A comprehensive review. CHEMOSPHERE 2024; 359:142273. [PMID: 38750727 DOI: 10.1016/j.chemosphere.2024.142273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 05/03/2024] [Accepted: 05/05/2024] [Indexed: 05/19/2024]
Abstract
This comprehensive review examines recent trends in phytoremediation strategies to address soil radionuclide contamination by cesium (Cs) and strontium (Sr). Radionuclide contamination, resulting from natural processes and nuclear-related activities such as accidents and the operation of nuclear facilities, poses significant risks to the environment and human health. Cs and Sr, prominent radionuclides involved in nuclear accidents, exhibit chemical properties that contribute to their toxicity, including easy uptake, high solubility, and long half-lives. Phytoremediation is emerging as a promising and environmentally friendly approach to mitigate radionuclide contamination by exploiting the ability of plants to extract toxic elements from soil and water. This review focuses specifically on the removal of 90Sr and 137Cs, addressing their health risks and environmental implications. Understanding the mechanisms governing plant uptake of radionuclides is critical and is influenced by factors such as plant species, soil texture, and physicochemical properties. Phytoremediation not only addresses immediate contamination challenges but also provides long-term benefits for ecosystem restoration and sustainable development. By improving soil health, biodiversity, and ecosystem resilience, phytoremediation is in line with global sustainability goals and environmental protection initiatives. This review aims to provide insights into effective strategies for mitigating environmental hazards associated with radionuclide contamination and to highlight the importance of phytoremediation in environmental remediation efforts.
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Affiliation(s)
- Ayyoub Ammar
- Laboratory of Virology, Microbiology, Quality and Biotechnology /Eco-toxicology and Biodiversity (LVMQB/EB), Faculty of Sciences and Techniques Mohammedia, University Hassan II, Casablanca, Morocco; National Center for Energy, Sciences, and Nuclear Techniques (CNESTEN), Rabat, Morocco; Laboratory of Environment and Conservation of Natural Resources, National Institute of Agronomique Research (INRA), Rabat, Morocco.
| | - Asmae Nouira
- National Center for Energy, Sciences, and Nuclear Techniques (CNESTEN), Rabat, Morocco
| | - Zineb El Mouridi
- Laboratory of Environment and Conservation of Natural Resources, National Institute of Agronomique Research (INRA), Rabat, Morocco
| | - Said Boughribil
- Laboratory of Virology, Microbiology, Quality and Biotechnology /Eco-toxicology and Biodiversity (LVMQB/EB), Faculty of Sciences and Techniques Mohammedia, University Hassan II, Casablanca, Morocco
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Lu X, Zhang YY, Cheng W, Liu Y, Li Q, Li X, Dong F, Li J, Nie X. Chelating Effect of Siderophore Desferrioxamine-B on Uranyl Biomineralization Mediated by Shewanella putrefaciens. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:3974-3984. [PMID: 38306233 DOI: 10.1021/acs.est.3c05753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2024]
Abstract
In contaminated water and soil, little is known about the role and mechanism of the biometabolic molecule siderophore desferrioxamine-B (DFO) in the biogeochemical cycle of uranium due to complicated coordination and reaction networks. Here, a joint experimental and quantum chemical investigation is carried out to probe the biomineralization of uranyl (UO22+, referred to as U(VI) hereafter) induced by Shewanella putrefaciens (abbreviated as S. putrefaciens) in the presence of DFO and Fe3+ ion. The results show that the production of mineralized solids {hydrogen-uranium mica [H2(UO2)2(PO4)2·8H2O]} via S. putrefaciens binding with UO22+ is inhibited by DFO, which can both chelate preferentially UO22+ to form a U(VI)-DFO complex in solution and seize it from U(VI)-biominerals upon solvation. However, with Fe3+ ion introduced, the strong specificity of DFO binding with Fe3+ causes re-emergence of biomineralization of UO22+ {bassetite [Fe(UO2)2(PO4)2·8(H2O)]} by S. putrefaciens, owing to competitive complexation between Fe3+ and UO22+ for DFO. As DFO possesses three hydroxamic functional groups, it forms hexadentate coordination with Fe3+ and UO22+ ions via these functional groups. The stability of the Fe3+-DFO complex is much higher than that of U(VI)-DFO, resulting in some DFO-released UO22+ to be remobilized by S. putrefaciens. Our finding not only adds to the understanding of the fate of toxic U(VI)-containing substances in the environment and biogeochemical cycles in the future but also suggests the promising potential of utilizing functionalized DFO ligands for uranium processing.
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Affiliation(s)
- Xiaojing Lu
- National Collaborative Innovation Center for Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang621000, China
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou 730000, China
| | - Yang-Yang Zhang
- Department of Chemistry and Guangdong Provincial Key Laboratory of Catalytic Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wencai Cheng
- National Collaborative Innovation Center for Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang621000, China
| | - Yingzhangyang Liu
- National Collaborative Innovation Center for Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang621000, China
| | - Qingrong Li
- National Collaborative Innovation Center for Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang621000, China
| | - Xiaoan Li
- Mianyang Central Hospital, NHC Key Laboratory of Nuclear Technology Medical Transformation, Mianyang 621000, China
| | - Faqin Dong
- National Collaborative Innovation Center for Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang621000, China
- Key Laboratory of Solid Waste Treatment and Resource Recycle of Ministry of Education, Southwest University of Science and Technology, Mianyang 621010, China
| | - Jun Li
- Department of Chemistry and Guangdong Provincial Key Laboratory of Catalytic Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
- Department of Chemistry and Engineering Research Center of Advanced Rare-Earth Materials of Ministry of Education, Tsinghua University, Beijing 100084, China
| | - Xiaoqin Nie
- National Collaborative Innovation Center for Nuclear Waste and Environmental Safety, Southwest University of Science and Technology, Mianyang621000, China
- Key Laboratory of Solid Waste Treatment and Resource Recycle of Ministry of Education, Southwest University of Science and Technology, Mianyang 621010, China
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Yuan W, She J, Liu J, Zhang Q, Wei X, Huang L, Zeng X, Wang J. Insight into microbial functional genes' role in geochemical distribution and cycling of uranium: The evidence from covering soils of uranium tailings dam. JOURNAL OF HAZARDOUS MATERIALS 2024; 461:132630. [PMID: 37774604 DOI: 10.1016/j.jhazmat.2023.132630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/26/2023] [Accepted: 09/23/2023] [Indexed: 10/01/2023]
Abstract
There exists a research gap on microbial functional genes' role in U geochemical behavior and cycling in U contaminated soils, which has been poorly understood. Herein, 16S rRNA sequencing gene amplifiers and metagenome analysis were applied to probe microbial community structure and functional metabolism of different depth layers of covering soils in U tailings dam. Results showed that the soils were highly enriched with U (47.5-123.3 mg/kg) and a remarkable portion of 35-70% was associated with the labile fractions. It was found that U geochemical distribution was notably interacted with functional genes from N, S, Fe and P related microbes. Importantly, diminution in gene NirK and amplification in nrfH involving in nitrate reduction could induce microbial tolerance to U. Moreover, gene Sat in microbial sulfate reduction, NosZ and NorB in nitrate reduction, phnD, upgA and upgC in P transportation and phnI, phnK, phoA and opd in microbial organic P mineralization, were all closely linked to U geochemical distribution, species and cycling. All these findings disclose the functional genes that may control the transfer and transformation behavior of U in soil environment, which provides important and novel indications for the bio-remediation strategies towards U polluted sites.
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Affiliation(s)
- Wenhuan Yuan
- Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China
| | - Jingye She
- Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China
| | - Juan Liu
- Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China
| | - Qiong Zhang
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Xudong Wei
- Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China
| | - Liting Huang
- Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China
| | - Xuan Zeng
- Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China
| | - Jin Wang
- Guangdong Provincial Key Laboratory of Radionuclides Pollution Control and Resources, School of Environmental Science and Engineering, Guangzhou University, Guangzhou, China.
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Xiong J, Chen J, Han Y, Ma J, Liu S, Xu Z, Liu X, Tong X, Luo J. Graphene oxide sheathed cobalt vanadate porous nanospheres for enhanced uranium extraction. J SOLID STATE CHEM 2023. [DOI: 10.1016/j.jssc.2023.123972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/13/2023]
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Sun H, Tang Q, Li Y, Liang ZH, Li FH, Li WW, Yu HQ. Radionuclide Reduction by Combinatorial Optimization of Microbial Extracellular Electron Transfer with a Physiologically Adapted Regulatory Platform. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:674-684. [PMID: 36576943 DOI: 10.1021/acs.est.2c07697] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Microbial extracellular electron transfer (EET) is the basis for many microbial processes involved in element geochemical recycling, bioenergy harvesting, and bioremediation, including the technique for remediating U(VI)-contaminated environments. However, the low EET rate hinders its full potential from being fulfilled. The main challenge for engineering microbial EET is the difficulty in optimizing cell resource allocation for EET investment and basic metabolism and the optimal coordination of the different EET pathways. Here, we report a novel combinatorial optimization strategy with a physiologically adapted regulatory platform. Through exploring the physiologically adapted regulatory elements, a 271.97-fold strength range, autonomous, and dynamic regulatory platform was established for Shewanella oneidensis, a prominent electrochemically active bacterium. Both direct and mediated EET pathways are modularly reconfigured and tuned at various intensities with the regulatory platform, which were further assembled combinatorically. The optimal combinations exhibit up to 16.12-, 4.51-, and 8.40-fold improvements over the control in the maximum current density (1009.2 mA/m2) of microbial electrolysis cells and the voltage output (413.8 mV) and power density (229.1 mW/m2) of microbial fuel cells. In addition, the optimal strains exhibited up to 6.53-fold improvement in the radionuclide U(VI) removal efficiency. This work provides an effective and feasible approach to boost microbial EET performance for environmental applications.
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Zhao B, Sun Z, Guo Y, Zhou Z, Wang X, Ke P. Occurrence characteristics of uranium mineral-related substances in various environmental media in China: A critical review. JOURNAL OF HAZARDOUS MATERIALS 2023; 441:129856. [PMID: 36115096 DOI: 10.1016/j.jhazmat.2022.129856] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 08/17/2022] [Accepted: 08/24/2022] [Indexed: 06/15/2023]
Abstract
The high demand and extensive exploitation of uranium resources resulted in the ubiquity and high detection levels of uranium mineral-related substances in various environment media in China. The potential adverse effects of uranium mineral-related substances on environment and human health have received extensive attention. Therefore, we reviewed the occurrence and spatial distribution of uranium mineral-related substances in various basins and environmental media in China to obtain an overall understanding. We collected information from over 70 papers reporting the occurrence and distribution of uranium mineral-related substances in multiple environments and 183 articles on the genesis of uranium deposits in China from 2001 to 2021. Then the occurrence of uranium mineral-related substances and corresponding correlation in different basins, environmental media and depth ranges were compared in detail. And this review assessed the uranium mineral-related pollution in China based on various environmental quality standards of China, EPA and WHO, and proposed the priority uranium mineral-related heavy metals and radioactive substances based on cluster analysis. This review showed that there were obvious differences in the occurrence characteristics of various uranium mineral-related substances in different environmental media, especially in the surrounding environment of sandstone type and hard rock type uranium deposits. These results will guide us to tackle the challenge of uranium mineral-related pollution in China. The correlation analysis of uranium mineral-related pollutants in different environmental media and the identification of priority pollutants will also provide instructions for us to control uranium mineral-related pollution. Finally, we put forward a series of urgent and practical suggestions on risk management and control of uranium mining according to the current situation of uranium mining environment in China, which is of guiding significance for the realization of "green uranium mining".
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Affiliation(s)
- Bei Zhao
- China University of Geosciences (Beijing), Beijing 100083, China
| | - Zhanxue Sun
- China University of Geosciences (Beijing), Beijing 100083, China; State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China.
| | - Yadan Guo
- State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
| | - Zhongkui Zhou
- State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
| | - Xuegang Wang
- State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
| | - Pingchao Ke
- State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China
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He RL, Wu J, Cheng ZH, Li HH, Liu JQ, Liu DF, Li WW. Biomolecular Insights into Extracellular Pollutant Reduction Pathways of Geobacter sulfurreducens Using a Base Editor System. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:12247-12256. [PMID: 35960254 DOI: 10.1021/acs.est.2c02756] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Geobacter species are critically involved in elemental biogeochemical cycling and environmental bioremediation processes via extracellular electron transfer (EET), but the underlying biomolecular mechanisms remain elusive due to lack of effective analytical tools to explore into complicated EET networks. Here, a simple and highly efficient cytosine base editor was developed for engineering of the slow-growing Geobacter sulfurreducens (a doubling time of 5 h with acetate as the electron donor and fumarate as the electron acceptor). A single-plasmid cytosine base editor (pYYDT-BE) was constructed in G. sulfurreducens by fusing cytosine deaminase, Cas9 nickase, and a uracil glycosylase inhibitor. This system enabled single-locus editing at 100% efficiency and showed obvious preference at the cytosines in a TC, AC, or CC context than in a GC context. Gene inactivation tests confirmed that it could effectively edit 87.7-93.4% genes of the entire genome in nine model Geobacter species. With the aid of this base editor to construct a series of G. sulfurreducens mutants, we unveiled important roles of both pili and outer membrane c-type cytochromes in long-range EET, thereby providing important evidence to clarify the long-term controversy surrounding their specific roles. Furthermore, we find that pili were also involved in the extracellular reduction of uranium and clarified the key roles of the ExtHIJKL conduit complex and outer membrane c-type cytochromes in the selenite reduction process. This work developed an effective base editor tool for the genetic modification of Geobacter species and provided new insights into the EET network, which lay a basis for a better understanding and engineering of these microbes to favor environmental applications.
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Affiliation(s)
- Ru-Li He
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science & Technology of China, Hefei 230026, China
- University of Science and Technology of China-City University of Hong Kong Joint Advanced Research Center, Suzhou Institute for Advance Research of USTC, Suzhou 215123, China
| | - Jie Wu
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science & Technology of China, Hefei 230026, China
- University of Science and Technology of China-City University of Hong Kong Joint Advanced Research Center, Suzhou Institute for Advance Research of USTC, Suzhou 215123, China
| | - Zhou-Hua Cheng
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science & Technology of China, Hefei 230026, China
| | - Hui-Hui Li
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science & Technology of China, Hefei 230026, China
| | - Jia-Qi Liu
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science & Technology of China, Hefei 230026, China
| | - Dong-Feng Liu
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science & Technology of China, Hefei 230026, China
| | - Wen-Wei Li
- CAS Key Laboratory of Urban Pollutant Conversion, Department of Environmental Science and Engineering, University of Science & Technology of China, Hefei 230026, China
- University of Science and Technology of China-City University of Hong Kong Joint Advanced Research Center, Suzhou Institute for Advance Research of USTC, Suzhou 215123, China
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Zhao LQ, Zhao YL, He YJ, Yang XW, Luo XD. Tuberindine A, a Truffle Alkaloid with an Unprecedented Skeleton Exhibiting Anti-hyperuricemic Bioactivity. Org Lett 2022; 24:4333-4337. [PMID: 35699727 DOI: 10.1021/acs.orglett.2c01421] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tuberindines A and B (1 and 2), truffle alkaloids with intriguing structures, were isolated from Tuber indicum and detected in other truffle species. They appear to arise biosynthetically from amino acid and isosaccharinic units. Compound 1 upregulated the expression of organic anion transporters OAT1 and ABCG2 and significantly exhibited antihyperuricemic bioactivity in vitro and in vivo, which might support the value of truffles as a dietary supplement.
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Affiliation(s)
- Lan-Qin Zhao
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, People's Republic of China
| | - Yun-Li Zhao
- Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education; Yunnan Provincial Center for Research & Development of Natural Products; School of Chemical Science and Technology, Yunnan University, Kunming 650091, People's Republic of China
| | - Ying-Jie He
- Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education; Yunnan Provincial Center for Research & Development of Natural Products; School of Chemical Science and Technology, Yunnan University, Kunming 650091, People's Republic of China
| | - Xing-Wei Yang
- School of Pharmaceutical Sciences (Shenzhen), Sun Yat-sen University, Shenzhen 518107, People's Republic of China
| | - Xiao-Dong Luo
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, People's Republic of China.,Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education; Yunnan Provincial Center for Research & Development of Natural Products; School of Chemical Science and Technology, Yunnan University, Kunming 650091, People's Republic of China
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Enhancement of uranium(VI) biomineralization by Saccharomyces cerevisiae through addition of inorganic phosphorus. J Radioanal Nucl Chem 2022. [DOI: 10.1007/s10967-022-08276-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Kvashnina KO, Butorin SM. High-energy resolution X-ray spectroscopy at actinide M 4,5 and ligand K edges: what we know, what we want to know, and what we can know. Chem Commun (Camb) 2022; 58:327-342. [PMID: 34874022 PMCID: PMC8725612 DOI: 10.1039/d1cc04851a] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/15/2021] [Indexed: 12/20/2022]
Abstract
In recent years, scientists have progressively recognized the role of electronic structures in the characterization of chemical properties for actinide containing materials. High-energy resolution X-ray spectroscopy at the actinide M4,5 edges emerged as a promising direction because this method can probe actinide properties at the atomic level through the possibility of reducing the experimental spectral width below the natural core-hole lifetime broadening. Parallel to the technical developments of the X-ray method and experimental discoveries, theoretical models, describing the observed electronic structure phenomena, have also advanced. In this feature article, we describe the latest progress in the field of high-energy resolution X-ray spectroscopy at the actinide M4,5 and ligand K edges and we show that the methods are able to (a) provide fingerprint information on the actinide oxidation state and ground state characters (b) probe 5f occupancy, non-stoichiometry, defects, and ligand/metal ratio and (c) investigate the local symmetry and effects of the crystal field. We discuss the chemical aspects of the electronic structure in terms familiar to chemists and materials scientists and conclude with a brief description of new opportunities and approaches to improve the experimental methodology and theoretical analysis for f-electron systems.
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Affiliation(s)
- Kristina O Kvashnina
- The Rossendorf Beamline at ESRF, The European Synchrotron, CS40220, 38043 Grenoble Cedex 9, France.
- Institute of Resource Ecology, Helmholtz Zentrum Dresden-Rossendorf (HZDR), PO Box 510119, 01314 Dresden, Germany
- Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia
| | - Sergei M Butorin
- Condensed Matter Physics of Energy Materials, X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala, Sweden.
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Bioremediation of Uranium- and Nitrate-Contaminated Groundwater after the In Situ Leach Mining of Uranium. WATER 2021. [DOI: 10.3390/w13223188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Uranium and nitrate are common groundwater pollutants near in situ leach uranium mines. However, we still lack techniques that can simultaneously immobilize uranium and reduce nitrate using a single bacterial species. In this study, the potential of simultaneous uranium immobilization and nitrate reduction by a single AFODN (anaerobic Fe(II) oxidizing denitrifier), Clostridium sp. PXL2, was investigated. Clostridium sp. PXL2 showed tolerance to U(VI) concentrations varying from 4.2 µM to 42 µM. The U(VI) immobilization and nitrate reduction rates in groundwater samples inoculated with this bacterium reached up to 75.1% and 55.7%, respectively, under neutral conditions. Exposure to oxidation conditions led to further U(VI) removal but did not show any noticeable effect on nitrate reduction. The U(VI) immobilization rate reached up to 85% with an increased Fe(II) initial concentration, but this inhibited nitrate reduction. SEM (scanning electron microscopy) coupled with EDS (energy dispersive spectroscopy) showed that the U(VI) immobilization was mainly due to sorption to amorphous ferric oxides. U(VI) and nitrate bioremediation by AFODNs, including Clostridium sp. PXL2, may provide a promising method for the treatment of uranium- and nitrate-contaminated groundwater after the in situ leach mining of uranium.
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