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Ighalo JO, Chen Z, Ohoro CR, Oniye M, Igwegbe CA, Elimhingbovo I, Khongthaw B, Dulta K, Yap PS, Anastopoulos I. A review of remediation technologies for uranium-contaminated water. CHEMOSPHERE 2024; 352:141322. [PMID: 38296212 DOI: 10.1016/j.chemosphere.2024.141322] [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: 10/24/2023] [Revised: 01/24/2024] [Accepted: 01/27/2024] [Indexed: 02/09/2024]
Abstract
Uranium is a naturally existing radioactive element present in the Earth's crust. It exhibits lithophilic characteristics, indicating its tendency to be located near the surface of the Earth and tightly bound to oxygen. It is ecotoxic, hence the need for its removal from the aqueous environment. This paper focuses on the variety of water treatment processes for the removal of uranium from water and this includes physical (membrane separation, adsorption and electrocoagulation), chemical (ion exchange, photocatalysis and persulfate reduction), and biological (bio-reduction and biosorption) approaches. It was observed that membrane filtration and ion exchange are the most popular and promising processes for this application. Membrane processes have high throughput but with the challenge of high power requirements and fouling. Besides high pH sensitivity, ion exchange does not have any major challenges related to its application. Several other unique observations were derived from this review. Chitosan/Chlorella pyrenoidosa composite adsorbent bearing phosphate ligand, hydroxyapatite aerogel and MXene/graphene oxide composite has shown super-adsorbent performance (>1000 mg/g uptake capacity) for uranium. Ultrafiltration (UF) membranes, reverse osmosis (RO) membranes and electrocoagulation have been observed not to go below 97% uranium removal/conversion efficiency for most cases reported in the literature. Heat persulfate reduction has been explored quite recently and shown to achieve as high as 86% uranium reduction efficiency. We anticipate that future studies would explore hybrid processes (which are any combinations of multiple conventional techniques) to solve various aspects of the process design and performance challenges.
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Affiliation(s)
- Joshua O Ighalo
- Department of Chemical Engineering, Nnamdi Azikiwe University, P. M. B. 5025, Awka, Nigeria; Tim Taylor Department of Chemical Engineering, Kansas State University, Manhattan, KS 66506, USA.
| | - Zhonghao Chen
- Department of Civil Engineering, Xi'an Jiaotong-Liverpool University, Suzhou, 215123, China
| | - Chinemerem R Ohoro
- Water Research Group, Unit for Environmental Sciences and Management, North-West University, 11 Hoffman St, Potchefstroom 2520, South Africa
| | - Mutiat Oniye
- Department of Chemical and Material Science, School of Engineering and Digital Sciences, Nazarbayev University, Astana, 010000 Kazakhstan
| | - Chinenye Adaobi Igwegbe
- Department of Chemical Engineering, Nnamdi Azikiwe University, P. M. B. 5025, Awka, Nigeria; Department of Applied Bioeconomy, Wroclaw University of Environmental and Life Sciences, 51-630 Wroclaw, Poland
| | - Isaiah Elimhingbovo
- Department of Animal and Environmental Biology, University of Benin, Benin City, Nigeria
| | - Banlambhabok Khongthaw
- Faculty of Applied Sciences and Biotechnology, Shoolini University, Solan, Himachal Pradesh, 173229, India
| | - Kanika Dulta
- Department of Food Technology, School of Applied and Life Sciences, Uttaranchal University, Dehradun-248007, Uttarakhand, India
| | - Pow-Seng Yap
- Department of Civil Engineering, Xi'an Jiaotong-Liverpool University, Suzhou, 215123, China
| | - Ioannis Anastopoulos
- Department of Agriculture, University of Ioannina, UoI Kostaki Campus, Arta 47100, Greece
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2
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Zelenina D, Kuzmenkova N, Sobolev D, Boldyrev K, Namsaraev Z, Artemiev G, Samylina O, Popova N, Safonov A. Biogeochemical Factors of Cs, Sr, U, Pu Immobilization in Bottom Sediments of the Upa River, Located in the Zone of Chernobyl Accident. BIOLOGY 2022; 12:biology12010010. [PMID: 36671703 PMCID: PMC9854679 DOI: 10.3390/biology12010010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Revised: 12/14/2022] [Accepted: 12/17/2022] [Indexed: 12/24/2022]
Abstract
Laboratory modeling of Cs, Sr, U, Pu immobilization by phytoplankton of the river Upa, affected after the Chernobyl accident, has been carried out. Certain conditions are selected for strong fixation of radionuclides in bottom sediments due to biogeochemical processes. The process of radionuclide removal from the water phase via precipitation was based on their accumulation by phytoplankton, stimulated by nitrogen and phosphorus sources. After eight days of stimulation, planktonic phototrophic biomass, dominated by cyanobacteria of the genus Planktothrix, appears in the water sample. The effectiveness of U, Pu and Sr purification via their transfer to bottom sediment was observed within one month. The addition of ammonium sulfate and phosphate (Ammophos) led to the activation of sulfate- and iron-reducing bacteria of the genera Desulfobacterota, Desulfotomaculum, Desulfosporomusa, Desulfosporosinus, Thermodesulfobium, Thiomonas, Thiobacillus, Sulfuritallea, Pseudomonas, which form sulphide ferrous precipitates such as pyrite, wurtzite, hydrotroillite, etc., in anaerobic bottom sediments. The biogenic mineral composition of the sediments obtained under laboratory conditions was verified via thermodynamic modeling.
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Affiliation(s)
- Darya Zelenina
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, RAS, Obrucheva Str. 40, Moscow 117342, Russia
| | - Natalia Kuzmenkova
- Radiochemistry Division, Faculty of Chemistry, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia
- V. Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, Kosygina Str. 19, Moscow 119991, Russia
| | - Denis Sobolev
- Nuclear Safety Institute, RAS, Bolshaya Tulskaya St. 52, Moscow 115191, Russia
| | - Kirill Boldyrev
- Nuclear Safety Institute, RAS, Bolshaya Tulskaya St. 52, Moscow 115191, Russia
| | - Zorigto Namsaraev
- Kurchatov Centre for Genome Research, NRC Kurchatov Institute, Akad. Kurchatov Sq., 2, Moscow 123098, Russia
| | - Grigoriy Artemiev
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, RAS, Obrucheva Str. 40, Moscow 117342, Russia
| | - Olga Samylina
- Winogradsky Institute of Microbiology, Research Centre for Biotechnology, Russian Academy of Sciences, Prospect 60-Letiya Oktyabrya 7/2, Moscow 117312, Russia
| | - Nadezhda Popova
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, RAS, Obrucheva Str. 40, Moscow 117342, Russia
| | - Alexey Safonov
- A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, RAS, Obrucheva Str. 40, Moscow 117342, Russia
- Correspondence:
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Rogiers T, Merroun ML, Williamson A, Leys N, Houdt RV, Boon N, Mijnendonckx K. Cupriavidus metallidurans NA4 actively forms polyhydroxybutyrate-associated uranium-phosphate precipitates. JOURNAL OF HAZARDOUS MATERIALS 2022; 421:126737. [PMID: 34388922 DOI: 10.1016/j.jhazmat.2021.126737] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/21/2021] [Accepted: 07/22/2021] [Indexed: 06/13/2023]
Abstract
Cupriavidus metallidurans is a model bacterium to study molecular metal resistance mechanisms and its use for the bioremediation of several metals has been shown. However, its mechanisms for radionuclide resistance are unexplored. We investigated the interaction with uranium and associated cellular response to uranium for Cupriavidus metallidurans NA4. Strain NA4 actively captured 98 ± 1% of the uranium in its biomass after growing 24 h in the presence of 100 µM uranyl nitrate. TEM HAADF-EDX microscopy confirmed intracellular uranium-phosphate precipitates that were mainly associated with polyhydroxybutyrate. Furthermore, whole transcriptome sequencing indicated a complex transcriptional response with upregulation of genes encoding general stress-related proteins and several genes involved in metal resistance. More in particular, gene clusters known to be involved in copper and silver resistance were differentially expressed. This study provides further insights into bacterial interactions with and their response to uranium. Our results could be promising for uranium bioremediation purposes with the multi-metal resistant bacterium C. metallidurans NA4.
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Affiliation(s)
- Tom Rogiers
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium; Center for Microbial Ecology and Technology (CMET), UGent, Ghent, Belgium.
| | | | - Adam Williamson
- Center for Microbial Ecology and Technology (CMET), UGent, Ghent, Belgium.
| | - Natalie Leys
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Rob Van Houdt
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Nico Boon
- Center for Microbial Ecology and Technology (CMET), UGent, Ghent, Belgium.
| | - Kristel Mijnendonckx
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
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4
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Kim S, Bender WM, Becker U. Exploring the kinetics of actinyl-EDTA reduction by ferrous iron using quantum-mechanical calculations. Phys Chem Chem Phys 2021; 23:5298-5314. [PMID: 33634290 DOI: 10.1039/d0cp05179a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reduction of An(vi) (An = U, Np, and Pu) to An(iv) significantly decreases its solubility and mobility. This reaction can be hindered by complexation with inorganic (e.g., carbonate) or organic ligands. Ethylenediaminetetraacetic acid (EDTA) is one such organic ligand that forms stable complexes with actinides. Therefore, it may enhance the mobility of actinides. However, the redox kinetics and mechanisms of actinyl (An(v/vi)O2+/2+)-EDTA are not well characterized yet and are thus studied here using quantum-mechanical calculations. The principle is to approach the actinyl-EDTA and Fe2+ (reductant) in small incremental steps and calculate the system energy at each distance. The overall reaction is then delineated into sub-processes (encounter frequency in bulk solution, formation of outer-sphere complex, transition from outer- to inner-sphere complex, and electron transfer), and reaction rates are determined for each sub-process. The formation of outer-sphere complexes occurs rapidly in microseconds to seconds over a wide range of actinyl concentrations (pM to μM); in contrast, the transition to the inner-sphere complex is relatively slow (milliseconds to a few seconds). Immediate electron transfer to form the pentavalent actinide is observed along the reaction path for Np(vi) and Pu(vi), but not for U(vi). Surprisingly, in acidic conditions, one of the carboxylic groups gets protonated in EDTA of [UO2(edta)]2- rather than one of the amino groups. This process-based series of calculations can be applied to any redox reaction and allows the prediction of changes to the rate law and rate-limiting step in a more fundamental way for different environments.
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Affiliation(s)
- Sooyeon Kim
- Department of Earth and Environmental Sciences, University of Michigan, Room 2534, North University Building, 1100 N University Ave, Ann Arbor, MI 48109-1005, USA.
| | - Will M Bender
- Department of Earth and Environmental Sciences, University of Michigan, Room 2534, North University Building, 1100 N University Ave, Ann Arbor, MI 48109-1005, USA. and Geosyntec Consultants, 1111 Broadway, 6th Floor, Oakland, CA 94607, USA
| | - Udo Becker
- Department of Earth and Environmental Sciences, University of Michigan, Room 2534, North University Building, 1100 N University Ave, Ann Arbor, MI 48109-1005, USA.
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5
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Lakaniemi AM, Douglas GB, Kaksonen AH. Engineering and kinetic aspects of bacterial uranium reduction for the remediation of uranium contaminated environments. JOURNAL OF HAZARDOUS MATERIALS 2019; 371:198-212. [PMID: 30851673 DOI: 10.1016/j.jhazmat.2019.02.074] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 01/29/2019] [Accepted: 02/20/2019] [Indexed: 06/09/2023]
Abstract
Biological reduction of soluble uranium from U(VI) to insoluble U(IV) coupled to the oxidation of an electron donor (hydrogen or organic compounds) is a potentially cost-efficient way to reduce the U concentrations in contaminated waters to below regulatory limits. A variety of microorganisms originating from both U contaminated and non-contaminated environments have demonstrated U(VI) reduction capacity under anaerobic conditions. Bioreduction of U(VI) is considered especially promising for in situ remediation, where the activity of indigenous microorganisms is stimulated by supplying a suitable electron donor to the subsurface to contain U contamination to a specific location in a sparingly soluble form. Less studied microbial biofilm-based bioreactors and bioelectrochemical systems have also shown potential for efficient U(VI) reduction to remove U from contaminated water streams. This review compares the advantages and challenges of U(VI)-reducing in situ remediation processes, bioreactors and bioelectrochemical systems. In addition, the current knowledge of U(VI) bioreduction mechanisms and factors affecting U(VI) reduction kinetics (e.g. pH, temperature, and the chemical composition of the contaminated water) are discussed, as both of these aspects are important in designing efficient remediation processes.
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Affiliation(s)
- Aino-Maija Lakaniemi
- Tampere University, Faculty of Engineering and Natural Sciences, P.O. Box 541, FI- 33104, Tampere University, Finland; CSIRO Land and Water, 147 Underwood Avenue, Floreat, Western Australia, 6014, Australia.
| | - Grant B Douglas
- CSIRO Land and Water, 147 Underwood Avenue, Floreat, Western Australia, 6014, Australia
| | - Anna H Kaksonen
- CSIRO Land and Water, 147 Underwood Avenue, Floreat, Western Australia, 6014, Australia
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6
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Kolhe N, Zinjarde S, Acharya C. Responses exhibited by various microbial groups relevant to uranium exposure. Biotechnol Adv 2018; 36:1828-1846. [PMID: 30017503 DOI: 10.1016/j.biotechadv.2018.07.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 07/08/2018] [Accepted: 07/09/2018] [Indexed: 11/28/2022]
Abstract
There is a strong interest in knowing how various microbial systems respond to the presence of uranium (U), largely in the context of bioremediation. There is no known biological role for uranium so far. Uranium is naturally present in rocks and minerals. The insoluble nature of the U(IV) minerals keeps uranium firmly bound in the earth's crust minimizing its bioavailability. However, anthropogenic nuclear reaction processes over the last few decades have resulted in introduction of uranium into the environment in soluble and toxic forms. Microbes adsorb, accumulate, reduce, oxidize, possibly respire, mineralize and precipitate uranium. This review focuses on the microbial responses to uranium exposure which allows the alteration of the forms and concentrations of uranium within the cell and in the local environment. Detailed information on the three major bioprocesses namely, biosorption, bioprecipitation and bioreduction exhibited by the microbes belonging to various groups and subgroups of bacteria, fungi and algae is provided in this review elucidating their intrinsic and engineered abilities for uranium removal. The survey also highlights the instances of the field trials undertaken for in situ uranium bioremediation. Advances in genomics and proteomics approaches providing the information on the regulatory and physiologically important determinants in the microbes in response to uranium challenge have been catalogued here. Recent developments in metagenomics and metaproteomics indicating the ecologically relevant traits required for the adaptation and survival of environmental microbes residing in uranium contaminated sites are also included. A comprehensive understanding of the microbial responses to uranium can facilitate the development of in situ U bioremediation strategies.
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Affiliation(s)
- Nilesh Kolhe
- Institute of Bioinformatics and Biotechnology, Savitribai Phule Pune University, Pune 411007, India; Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Smita Zinjarde
- Institute of Bioinformatics and Biotechnology, Savitribai Phule Pune University, Pune 411007, India; Department of Microbiology, Savitribai Phule Pune University, Pune 411007, India.
| | - Celin Acharya
- Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India; Homi Bhabha National Institute, Anushakti Nagar, Trombay, Mumbai 400094, India.
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7
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Krawczyk-Bärsch E, Gerber U, Müller K, Moll H, Rossberg A, Steudtner R, Merroun ML. Multidisciplinary characterization of U(VI) sequestration by Acidovorax facilis for bioremediation purposes. JOURNAL OF HAZARDOUS MATERIALS 2018; 347:233-241. [PMID: 29324323 DOI: 10.1016/j.jhazmat.2017.12.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 12/04/2017] [Accepted: 12/10/2017] [Indexed: 06/07/2023]
Abstract
The contamination of the environment by U may affect plant life and consequently may have an impact on animal and human health. The present work describes U(VI) sequestration by Acidovorax facilis using a multidisciplinary approach combining wet chemistry, transmission electron microscopy, and spectroscopy methods (e.g. cryo-time resolved laser-induced fluorescence spectroscopy, extended X-ray absorption fine structure spectroscopy, and in-situ attenuated total reflection Fourier transform infrared spectroscopy). This bacterial strain is widely distributed in nature including U-contaminated sites. In kinetic batch experiments cells of A. facilis were contacted for 5 min to 48 h with 0.1 mM U(VI). The results show that the local coordination of U species associated with the cells depends upon time contact. U is bound mainly to phosphate groups of lipopolysaccharide (LPS) at the outer membrane within the first hour. And, that both, phosphoryl and carboxyl functionality groups of LPS and peptidoglycan of A. facilis cells may effectuate the removal of high U amounts from solution at 24-48 h of incubation. It is clearly demonstrated that A. facilis may play an important role in predicting the transport behaviour of U in the environment and that the results will contribute to the improvement of bioremediation methods of U-contaminated sites.
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Affiliation(s)
- E Krawczyk-Bärsch
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, D-01328 Dresden, Germany.
| | - U Gerber
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, D-01328 Dresden, Germany
| | - K Müller
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, D-01328 Dresden, Germany
| | - H Moll
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, D-01328 Dresden, Germany
| | - A Rossberg
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, D-01328 Dresden, Germany
| | - R Steudtner
- Helmholtz-Zentrum Dresden-Rossendorf, Institute of Resource Ecology, Bautzner Landstraße 400, D-01328 Dresden, Germany
| | - M L Merroun
- University of Granada, Department of Microbiology, Campus Fuentenueva, E-18071 Granada, Spain
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8
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Shen Y, Zheng X, Wang X, Wang T. The biomineralization process of uranium(VI) by Saccharomyces cerevisiae - transformation from amorphous U(VI) to crystalline chernikovite. Appl Microbiol Biotechnol 2018; 102:4217-4229. [PMID: 29564524 DOI: 10.1007/s00253-018-8918-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 03/05/2018] [Accepted: 03/06/2018] [Indexed: 11/30/2022]
Abstract
Microorganisms play a significant role in uranium(VI) biogeochemistry and influence U(VI) transformation through biomineralization. In the present work, the process of uranium mineralization was investigated by Saccharomyces cerevisiae. The toxicity experiments showed that the viability of cell was not significantly affected by 100 mg L-1 U(VI) under 4 days of exposure time. The batch experiments showed that the phosphate concentration and pH value increased over time during U(VI) adsorption. Meanwhile, thermodynamic calculations demonstrated that the adsorption system was supersaturated with respect to UO2HPO4. The X-ray powder diffraction spectroscopy (XRD), field emission scanning electron microscopy (FE-SEM) equipped with energy dispersive spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses indicated that the U(VI) was first attached onto the cell surface and reacted with hydroxyl, carboxyl, and phosphate groups through electrostatic interactions and complexation. As the immobilization of U(VI) transformed it from the ionic to the amorphous state, lamellar uranium precipitate was formed on the cell surface. With the prolongation of time, the amorphous uranium compound disappeared, and there were some crystalline substances observed extracellularly, which were well-characterized as tetragonal-chernikovite. Furthermore, the size of chernikovite was regulated at nano-level by cells, and the perfect crystal was formed finally. These findings provided an understanding of the non-reductive transformation process of U(VI) from the amorphous to crystalline state within microbe systems, which would be beneficial for the U(VI) treatment and reuse of nuclides and heavy metals.
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Affiliation(s)
- Yanghao Shen
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China
| | - Xinyan Zheng
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China
| | - Xiaoyu Wang
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China
| | - Tieshan Wang
- School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China.
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Chen T, Philips C, Hamilton J, Chartbrand B, Grosskleg J, Bradshaw K, Carlson T, Timlick K, Peak D, Siciliano SD. Citrate Addition Increased Phosphorus Bioavailability and Enhanced Gasoline Bioremediation. JOURNAL OF ENVIRONMENTAL QUALITY 2017; 46:975-983. [PMID: 28991988 DOI: 10.2134/jeq2017.02.0064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Phosphorus (P) bioavailability often limits gasoline biodegradation in calcareous cold-region soils. One possible method to increase P bioavailability in such soils is the addition of citrate. Citrate addition at the field scale may increase hydrocarbon degradation by: (i) enhancing inorganic and organic P dissolution and desorption, (ii) increasing hydrocarbon bioavailability, and/or (iii) stimulating microbial activity. Alternatively, citrate addition may inhibit activity due to competitive effects on carbon metabolism. Using a field-scale in situ biostimulation study, we evaluated if citrate could stimulate gasoline degradation and what the dominant mechanism of this stimulation will be. Two large bore injectors were constructed at a site contaminated with gasoline, and a biostimulation solution of 11 mM MgSO, 1 mM HPO, and 0.08 mM HNO at pH 6.5 in municipal potable water was injected at ∼5000 L d for about 4 mo. Following this, 10 mM citric acid was incorporated into the existing biostimulation solution and the site continued to be stimulated for 8 mo. After citrate addition, the bioavailable P fraction in groundwater and soil increased. Iron(II) groundwater concentrations increased and corresponded to decreases in benzene, toluene, ethylbenzene, xylenes (BTEX) in groundwater, as well as a decrease in F1 in the soil saturated zone. Overall, citrate addition increased P bioavailability and may stimulate anaerobic microbial activity, resulting in accelerated anaerobic gasoline bioremediation in cold-region calcareous soils.
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Wufuer R, Wei Y, Lin Q, Wang H, Song W, Liu W, Zhang D, Pan X, Gadd GM. Uranium Bioreduction and Biomineralization. ADVANCES IN APPLIED MICROBIOLOGY 2017; 101:137-168. [PMID: 29050665 DOI: 10.1016/bs.aambs.2017.01.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Following the development of nuclear science and technology, uranium contamination has been an ever increasing concern worldwide because of its potential for migration from the waste repositories and long-term contaminated environments. Physical and chemical techniques for uranium pollution are expensive and challenging. An alternative to these technologies is microbially mediated uranium bioremediation in contaminated water and soil environments due to its reduced cost and environmental friendliness. To date, four basic mechanisms of uranium bioremediation-uranium bioreduction, biosorption, biomineralization, and bioaccumulation-have been established, of which uranium bioreduction and biomineralization have been studied extensively. The objective of this review is to provide an understanding of recent developments in these two fields in relation to relevant microorganisms, mechanisms, influential factors, and obstacles.
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11
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Şengör SS, Singh G, Dohnalkova A, Spycher N, Ginn TR, Peyton BM, Sani RK. Impact of different environmental conditions on the aggregation of biogenic U(IV) nanoparticles synthesized by Desulfovibrio alaskensis G20. Biometals 2016; 29:965-980. [PMID: 27623995 DOI: 10.1007/s10534-016-9969-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 08/31/2016] [Indexed: 11/25/2022]
Abstract
This study investigates the impact of specific environmental conditions on the formation of colloidal U(IV) nanoparticles by the sulfate reducing bacteria (SRB, Desulfovibrio alaskensis G20). The reduction of soluble U(VI) to less soluble U(IV) was quantitatively investigated under growth and non-growth conditions in bicarbonate or 1,4-piperazinediethanesulfonic acid (PIPES) buffered environments. The results showed that under non-growth conditions, the majority of the reduced U nanoparticles aggregated and precipitated out of solution. High resolution transmission electron microscopy revealed that only a very small fraction of cells had reduced U precipitates in the periplasmic spaces in the presence of PIPES buffer, whereas in the presence of bicarbonate buffer, reduced U was also observed in the cytoplasm with greater aggregation of biogenic U(IV) particles at higher initial U(VI) concentrations. The same experiments were repeated under growth conditions using two different electron donors (lactate and pyruvate) and three electron acceptors (sulfate, fumarate, and thiosulfate). In contrast to the results of the non-growth experiments, even after 0.2 μm filtration, the majority of biogenic U(IV) remained in the aqueous phase resulting in potentially mobile biogenic U(IV) nanoparticles. Size fractionation results showed that U(IV) aggregates were between 18 and 200 nm in diameter, and thus could be very mobile. The findings of this study are helpful to assess the size and potential mobility of reduced U nanoparticles under different environmental conditions, and would provide insights on their potential impact affecting U(VI) bioremediation efforts at subsurface contaminated sites.
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Affiliation(s)
- S Sevinç Şengör
- Department of Civil and Environmental Engineering, Southern Methodist University, Dallas, TX, 75275-0339, USA
| | - Gursharan Singh
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, 501 East St. Joseph Street, Rapid City, SD, 57701-3995, USA
| | - Alice Dohnalkova
- WR Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Nicolas Spycher
- Lawrence Berkeley National Laboratory, Earth Sciences Division, 1 Cyclotron Rd, Berkeley, CA, 94720, USA
| | - Timothy R Ginn
- Department of Civil and Environmental Engineering, Washington State University, 405 Spokane Street, Pullman, WA, 99164, USA
| | - Brent M Peyton
- Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT, 59715, USA
| | - Rajesh K Sani
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, 501 East St. Joseph Street, Rapid City, SD, 57701-3995, USA.
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12
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Bao C, Wu H, Li L, Newcomer D, Long PE, Williams KH. Uranium bioreduction rates across scales: biogeochemical hot moments and hot spots during a biostimulation experiment at Rifle, Colorado. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:10116-10127. [PMID: 25079237 DOI: 10.1021/es501060d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We aim to understand the scale-dependent evolution of uranium bioreduction during a field experiment at a former uranium mill site near Rifle, Colorado. Acetate was injected to stimulate Fe-reducing bacteria (FeRB) and to immobilize aqueous U(VI) to insoluble U(IV). Bicarbonate was coinjected in half of the domain to mobilize sorbed U(VI). We used reactive transport modeling to integrate hydraulic and geochemical data and to quantify rates at the grid block (0.25 m) and experimental field scale (tens of meters). Although local rates varied by orders of magnitude in conjunction with biostimulation fronts propagating downstream, field-scale rates were dominated by those orders of magnitude higher rates at a few selected hot spots where Fe(III), U(VI), and FeRB were at their maxima in the vicinity of the injection wells. At particular locations, the hot moments with maximum rates negatively corresponded to their distance from the injection wells. Although bicarbonate injection enhanced local rates near the injection wells by a maximum of 39.4%, its effect at the field scale was limited to a maximum of 10.0%. We propose a rate-versus-measurement-length relationship (log R' = -0.63 log L - 2.20, with R' in μmol/mg cell protein/day and L in meters) for orders-of-magnitude estimation of uranium bioreduction rates across scales.
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Affiliation(s)
- Chen Bao
- John and Willie Leone Department of Energy and Mineral Engineering, ‡EMS Energy Institute, and §Earth and Environmental Systems Institute (EESI), Pennsylvania State University , University Park, Pennsylvania 16802, United States
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Determination of U(VI) and U(IV) concentrations in aqueous samples containing strong luminescence quenchers using TRLFS. J Radioanal Nucl Chem 2014. [DOI: 10.1007/s10967-014-3319-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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14
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Choi D, Lee SB, Kim S, Min B, Choi IG, Chang IS. Metabolically engineered glucose-utilizing Shewanella strains under anaerobic conditions. BIORESOURCE TECHNOLOGY 2014; 154:59-66. [PMID: 24384311 DOI: 10.1016/j.biortech.2013.12.025] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 12/04/2013] [Accepted: 12/06/2013] [Indexed: 05/20/2023]
Abstract
Comparative genome analysis of Shewanella strains predicted that the strains metabolize preferably two- and three-carbon carbohydrates as carbon/electron source because many Shewanella genomes are deficient of the key enzymes in glycolysis (e.g., glucokinase). In addition, all Shewanella genomes are known to have only one set of genes associated with the phosphotransferase system required to uptake sugars. To engineer Shewanella strains that can utilize five- and six-carbon carbohydrates, we constructed glucose-utilizing Shewanella oneidensis MR-1 by introducing the glucose facilitator (glf; ZMO0366) and glucokinase (glk; ZMO0369) genes of Zymomonas mobilis. The engineered MR-1 strain was able to grow on glucose as a sole carbon/electron source under anaerobic conditions. The glucose affinity (Ks) and glucokinase activity in the engineered MR-1 strain were 299.46 mM and 0.259 ± 0.034 U/g proteins. The engineered strain was successfully applied to a microbial fuel cell system and exhibited current generation using glucose as the electron source.
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Affiliation(s)
- Donggeon Choi
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan gwagi-ro, Buk-gu, Gwangju 500-712, Republic of Korea
| | - Sae Bom Lee
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan gwagi-ro, Buk-gu, Gwangju 500-712, Republic of Korea
| | - Sohyun Kim
- College of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-gu, Seoul 136-701, Republic of Korea
| | - Byoungnam Min
- College of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-gu, Seoul 136-701, Republic of Korea
| | - In-Geol Choi
- College of Life Sciences and Biotechnology, Korea University, Anam-dong, Sungbuk-gu, Seoul 136-701, Republic of Korea.
| | - In Seop Chang
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan gwagi-ro, Buk-gu, Gwangju 500-712, Republic of Korea.
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15
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Konopka A, Plymale AE, Carvajal DA, Lin X, McKinley JP. Environmental controls on the activity of aquifer microbial communities in the 300 area of the Hanford site. MICROBIAL ECOLOGY 2013; 66:889-896. [PMID: 24061343 DOI: 10.1007/s00248-013-0283-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 08/22/2013] [Indexed: 06/02/2023]
Abstract
Aquifer microbes in the 300 Area of the Hanford Site in southeastern Washington State, USA, are located in an oligotrophic environment and are periodically exposed to U(VI) concentrations that can range up to 10 μM in small sediment fractures. Assays of (3)H-leucine incorporation indicated that both sediment-associated and planktonic microbes were metabolically active, and that organic C was growth-limiting in the sediments. Although bacteria suspended in native groundwater retained high activity when exposed to 100 μM U(VI), they were inhibited by U(VI) <1 μM in synthetic groundwater that lacked added bicarbonate. Chemical speciation modeling suggested that positively charged species and particularly (UO2)3(OH)5 (+) rose in concentration as more U(VI) was added to synthetic groundwater, but that carbonate complexes dominated U(VI) speciation in natural groundwater. U toxicity was relieved when increasing amounts of bicarbonate were added to synthetic groundwater containing 4.5 μM U(VI). Pertechnetate, an oxyanion that is another contaminant of concern at the Hanford Site, was not toxic to groundwater microbes at concentrations up to 125 μM.
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Affiliation(s)
- Allan Konopka
- Microbiology Group, Pacific Northwest National Laboratory, P.O. Box 999, MSIN J4-18, Richland, WA, 99352, USA,
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16
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Prakash D, Gabani P, Chandel AK, Ronen Z, Singh OV. Bioremediation: a genuine technology to remediate radionuclides from the environment. Microb Biotechnol 2013; 6:349-60. [PMID: 23617701 PMCID: PMC3917470 DOI: 10.1111/1751-7915.12059] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 03/19/2013] [Accepted: 03/25/2013] [Indexed: 12/01/2022] Open
Abstract
Radionuclides in the environment are a major human and environmental health concern. Like the Chernobyl disaster of 1986, the Fukushima Daiichi nuclear disaster in 2011 is once again causing damage to the environment: a large quantity of radioactive waste is being generated and dumped into the environment, and if the general population is exposed to it, may cause serious life-threatening disorders. Bioremediation has been viewed as the ecologically responsible alternative to environmentally destructive physical remediation. Microorganisms carry endogenous genetic, biochemical and physiological properties that make them ideal agents for pollutant remediation in soil and groundwater. Attempts have been made to develop native or genetically engineered (GE) microbes for the remediation of environmental contaminants including radionuclides. Microorganism-mediated bioremediation can affect the solubility, bioavailability and mobility of radionuclides. Therefore, we aim to unveil the microbial-mediated mechanisms for biotransformation of radionuclides under various environmental conditions as developing strategies for waste management of radionuclides. A discussion follows of '-omics'-integrated genomics and proteomics technologies, which can be used to trace the genes and proteins of interest in a given microorganism towards a cell-free bioremediation strategy.
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Affiliation(s)
- Dhan Prakash
- Institute of Microbial Technology (CSIR), Sector 39-A, Chandigarh, 160036, India
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17
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Stewart BD, Girardot C, Spycher N, Sani RK, Peyton BM. Influence of chelating agents on biogenic uraninite reoxidation by Fe(III) (Hydr)oxides. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:364-371. [PMID: 23163577 DOI: 10.1021/es303022p] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Microbially mediated reduction of soluble U(VI) to U(IV) with subsequent precipitation of uraninite, UO(2(S)), has been proposed as a method for limiting uranium (U) migration. However, microbially reduced UO(2) may be susceptible to reoxidation by environmental factors, with Fe(III) (hydr)oxides playing a significant role. Little is known about the role that organic compounds such as Fe(III) chelators play in the stability of reduced U. Here, we investigate the impact of citrate, DFB, EDTA, and NTA on biogenic UO(2) reoxidation with ferrihydrite, goethite, and hematite. Experiments were conducted in anaerobic batch systems in PIPES buffer (10 mM, pH 7) with bicarbonate for approximately 80 days. Results showed EDTA accelerated UO(2) reoxidation the most at an initial rate of 9.5 μM day(-1) with ferrihydrite, 8.6 μM day(-1) with goethite, and 8.8 μM day(-1) with hematite. NTA accelerated UO(2) reoxidation with ferrihydrite at a rate of 4.8 μM day(-1); rates were less with goethite and hematite (0.66 and 0.71 μM day(-1), respectively). Citrate increased UO(2) reoxidation with ferrihydrite at a rate of 1.8 μM day(-1), but did not increase the extent of reaction with goethite or hematite, with no reoxidation in this case. In all cases, bicarbonate increased the rate and extent of UO(2) reoxidation with ferrihydrite in the presence and absence of chelators. The highest rate of UO(2) reoxidation occurred when the chelator promoted both UO(2) and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO(2) dissolution did not occur, UO(2) reoxidation likely proceeded through an aqueous Fe(III) intermediate with lower reoxidation rates observed. Reaction modeling suggests that strong Fe(II) chelators promote reoxidation whereas strong Fe(III) chelators impede it. These results indicate that chelators found in U contaminated sites may play a significant role in mobilizing U, potentially affecting bioremediation efforts.
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Affiliation(s)
- Brandy D Stewart
- Chemical and Biological Engineering and Center for Biofilm Engineering, Montana State University, Bozeman, Montana 59717, United States
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18
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Cho K, Zholi A, Frabutt D, Flood M, Floyd D, Tiquia SM. Linking bacterial diversity and geochemistry of uranium-contaminated groundwater. ENVIRONMENTAL TECHNOLOGY 2012; 33:1629-1640. [PMID: 22988623 DOI: 10.1080/09593330.2011.641036] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
To understand the link between bacterial diversity and geochemistry in uranium-contaminated groundwater, microbial communities were assessed based on clone libraries of 16S rDNA genes from the USDOE Oak Ridge Field Research Centre (FRC) site. Four groundwater wells (GW835, GW836, FW113-47 and FW215-49) with a wide range of pH (3 to 7), nitrate (44 to 23,400 mg L(-1)), uranium (0.73 to 60.36 mg L(-1)) and other metal contamination, were investigated. Results indicated that bacterial diversity correlated with the geochemistry of the groundwater. Microbial diversity decreased in relation to the contamination levels of the wells. The highly contaminated well (FW113-47) had lower gene diversity than less contaminated wells (FW215-49, GW835 and GW836). The high concentrations of contaminants present in well FW113-47 stimulated the growth of organisms capable of reducing uranium (Shewanella and Pseudomonas), nitrate (Pseudomonas, Rhodanobacter and Xanthomonas) and iron (Stenotrophomonas), and which were unique to this well. The clone libraries consisted primarily of sequences closely related to the phylum Proteobacteria, with FW-113-47 almost exclusively containing this phylum. Metal-reducing bacteria were present in all four wells, which may suggest that there is potential for successful bioremediation of the groundwater at the Oak Ridge FRC. The microbial community information gained from this study and previous studies at the site can be used to develop predictive multivariate and geographical information system (GIS) based models for microbial populations at the Oak Ridge FRC. This will allow for a better understanding of what organisms are likely to occur where and when, based on geochemistry, and how these organisms relate to bioremediation processes at the site.
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Affiliation(s)
- Kelly Cho
- 115F Science Building, Department of Natural Sciences, The University of Michigan, Dearborn, MI 48128, USA
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19
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Microbial community succession during lactate amendment and electron acceptor limitation reveals a predominance of metal-reducing Pelosinus spp. Appl Environ Microbiol 2012; 78:2082-91. [PMID: 22267668 DOI: 10.1128/aem.07165-11] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The determination of the success of in situ bioremediation strategies is complex. By using controlled laboratory conditions, the influence of individual variables, such as U(VI), Cr(VI), and electron donors and acceptors on community structure, dynamics, and the metal-reducing potential can be studied. Triplicate anaerobic, continuous-flow reactors were inoculated with Cr(VI)-contaminated groundwater from the Hanford, WA, 100-H area, amended with lactate, and incubated for 95 days to obtain stable, enriched communities. The reactors were kept anaerobic with N(2) gas (9 ml/min) flushing the headspace and were fed a defined medium amended with 30 mM lactate and 0.05 mM sulfate with a 48-h generation time. The resultant diversity decreased from 63 genera within 12 phyla to 11 bacterial genera (from 3 phyla) and 2 archaeal genera (from 1 phylum). Final communities were dominated by Pelosinus spp. and to a lesser degree, Acetobacterium spp., with low levels of other organisms, including methanogens. Four new strains of Pelosinus were isolated, with 3 strains being capable of Cr(VI) reduction while one also reduced U(VI). Under limited sulfate, it appeared that the sulfate reducers, including Desulfovibrio spp., were outcompeted. These results suggest that during times of electron acceptor limitation in situ, organisms such as Pelosinus spp. may outcompete the more-well-studied organisms while maintaining overall metal reduction rates and extents. Finally, lab-scale simulations can test new strategies on a smaller scale while facilitating community member isolation, so that a deeper understanding of community metabolism can be revealed.
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20
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Luo W, Gu B. Dissolution of uranium-bearing minerals and mobilization of uranium by organic ligands in a biologically reduced sediment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2011; 45:2994-2999. [PMID: 21395303 DOI: 10.1021/es103073u] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The stability and mobility of uranium (U) is a concern following its reductive precipitation or immobilization by techniques such as bioremediation at contaminated sites. In this study, the influences of complexing organic ligands such as citrate and ethylenediaminetetraacetate (EDTA) on the mobilization of U were investigated in both batch and column flow systems using a contaminated and bioreduced sediment. Results indicate that both reduced U(IV) and oxidized U(VI) in the sediment can be effectively mobilized with the addition of EDTA or citrate under anaerobic conditions. The dissolution and mobilization of U appear to be correlated to the dissolution of iron (Fe)- or aluminum (Al)-bearing minerals, with EDTA being more effective (with R2≥0.89) than citrate (R2<0.60) in dissolving these minerals. The column flow experiments confirm that U, Fe, and Al can be mobilized by these ligands under anoxic conditions, although the cumulative amounts of U removal constituted ∼0.1% of total U present in this sediment following a limited period of leaching. This study concludes that the presence of complexing organic ligands may pose a long-term concern by slowly dissolving U-bearing minerals and mobilizing U even under a strict anaerobic environment.
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Affiliation(s)
- Wensui Luo
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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21
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Stewart BD, Amos RT, Fendorf S. Effect of uranium(VI) speciation on simultaneous microbial reduction of uranium(VI) and iron(III). JOURNAL OF ENVIRONMENTAL QUALITY 2011; 40:90-97. [PMID: 21488497 DOI: 10.2134/jeq2010.0304] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Uranium is a pollutant of concern to both human and ecosystem health. Uranium's redox state often dictates whether it will reside in the aqueous or solid phase and thus plays an integral role in the mobility of uranium within the environment. In anaerobic environments, the more oxidized and mobile form of uranium (UO2(2+) and associated species) may be reduced, directly or indirectly, by microorganisms to U(IV) with subsequent precipitation of UO. However, various factors within soils and sediments, such as U(VI) speciation and the presence of competitive electron acceptors, may limit biological reduction of U(VI). Here we examine simultaneous dissimilatory reduction of Fe(III) and U(VI) in batch systems containing dissolved uranyl acetate and ferrihydrite-coated sand. Varying amounts of calcium were added to induce changes in aqueous U(VI) speciation. The amount of uranium removed from solution during 100 h of incubation with S. putrefaciens was 77% in absence of Ca or ferrihydrite, but only 24% (with ferrihydrite) and 14% (without ferrihydrite) were removed for systems with 0.8 mM Ca. Dissimilatory reduction of Fe(III) and U(VI) proceed through different enzyme pathways within one type of organism. We quantified the rate coefficients for simultaneous dissimilatory reduction of Fe(III) and U(VI) in systems varying in Ca concecentration (0-0.8 mM). The mathematical construct, implemented with the reactive transport code MIN3P, reveals predominant factors controlling rates and extent of uranium reduction in complex geochemical systems.
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Affiliation(s)
- Brandy D Stewart
- Environmental Earth System Science, Stanford Univ., Stanford, CA 94305, USA.
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22
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Mercury and other heavy metals influence bacterial community structure in contaminated Tennessee streams. Appl Environ Microbiol 2010; 77:302-11. [PMID: 21057024 DOI: 10.1128/aem.01715-10] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
High concentrations of uranium, inorganic mercury [Hg(II)], and methylmercury (MeHg) have been detected in streams located in the Department of Energy reservation in Oak Ridge, TN. To determine the potential effects of the surface water contamination on the microbial community composition, surface stream sediments were collected 7 times during the year, from 5 contaminated locations and 1 control stream. Fifty-nine samples were analyzed for bacterial community composition and geochemistry. Community characterization was based on GS 454 FLX pyrosequencing with 235 Mb of 16S rRNA gene sequence targeting the V4 region. Sorting and filtering of the raw reads resulted in 588,699 high-quality sequences with lengths of >200 bp. The bacterial community consisted of 23 phyla, including Proteobacteria (ranging from 22.9 to 58.5% per sample), Cyanobacteria (0.2 to 32.0%), Acidobacteria (1.6 to 30.6%), Verrucomicrobia (3.4 to 31.0%), and unclassified bacteria. Redundancy analysis indicated no significant differences in the bacterial community structure between midchannel and near-bank samples. Significant correlations were found between the bacterial community and seasonal as well as geochemical factors. Furthermore, several community members within the Proteobacteria group that includes sulfate-reducing bacteria and within the Verrucomicrobia group appeared to be associated positively with Hg and MeHg. This study is the first to indicate an influence of MeHg on the in situ microbial community and suggests possible roles of these bacteria in the Hg/MeHg cycle.
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Suzuki Y, Kitatsuji Y, Ohnuki T, Tsujimura S. Flavin mononucleotide mediated electron pathway for microbial U(VI) reduction. Phys Chem Chem Phys 2010; 12:10081-7. [PMID: 20623083 DOI: 10.1039/c0cp00339e] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Microbial reduction of U(VI) is an important phenomenon affecting uranium mobility in the subsurface environments. Elucidation of its mechanism is necessary for predicting uranium migration and for applying environmental remediation. In this study, we have examined the electron pathway for the U(VI) reduction mediated by flavin mononucleotide (FMN), which is secreted by Shewanella species. The cyclic voltammetry (CV) and photo-electrochemical methods with an optically transparent thin-layer electrode (OTTLE) cell were utilized in investigating in vitro the electron transfer reactions that take place between FMN and U(VI). The CV measurements of U(VI) were carried out in a citrate and Tris-HCl buffer both with and without FMN. A scarce U(VI) reduction current was observed in the absence of the FMN. To the contrary, a catalytic U(VI) reduction current was observed in the presence of FMN at the redox potential of the FMN. The reduction current increased with an increase in the concentration of the U(VI). The reduced form of the U was confirmed to be U(VI) by the photo-electrochemical analysis using the OTTLE cell. The results demonstrated that FMN acts as a mediator in the electro-reduction of U(VI) to U(iv). In addition, in vivo bio-reduction experiments on U(VI) with Shewanella putrefaciens revealed that the addition of FMN accelerated the reduction rate of U(VI). These results indicate that the bio-reduction of U(VI) by the Shewanella species can be catalyzed by FMN secreted from the cells.
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Affiliation(s)
- Yoshinori Suzuki
- School of Bioscience and Biotechnology, Tokyo University of Technology, Katakura, Hachioji, Tokyo 192-0982, Japan.
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Uranium(VI) complexation in cell culture medium: influence of speciation on Normal Rat Kidney (NRK-52E) cell accumulation. RADIOCHIM ACTA 2009. [DOI: 10.1524/ract.2005.93.11.691] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Summary
Uranium bioavailability and toxicity are closely linked to the metal's speciation in solution. However in biological fluids or in media classically used for cell culture – and subsequently for in vitro cell exposure –, uranium is rarely present as free-ion since these media contain non-negligible concentrations of potential ligands such as phosphate and bicarbonate but also co-ions such as calcium which can cause U(VI) complexes precipitation. The chemical form of uranium that is internalized in cells and interferes with biological processes is of major concern. Uranium toxicity and accumulation were evaluated in vitro on NRK-52E cells, model for rat renal proximal tubule. Uranium intracellular accumulation begins after 12 h exposure to 600 μM U(VI); toxicity appears as soon as cells accumulated 25 to 30 mg U/g protein. Modification of uranium speciation in the exposure medium induces great changes in toxicity and cell accumulation. Comparison of toxicity and accumulation results to theoretical uranium speciation, calculated with the J-Chess computer program, shows that free-ion concentration can not explain the total uranium intracellular accumulation. Low molecular weight U(VI) complexes, such as UO2(CO3)3
4− but also UO2PO4
− could be implicated in U(VI) cellular accumulation and toxicity.
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Vazquez GJ, Dodge CJ, Francis AJ. Bioreduction of U(VI)−Phthalate to a Polymeric U(IV)−Phthalate Colloid. Inorg Chem 2009; 48:9485-90. [DOI: 10.1021/ic900694k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gustavo J. Vazquez
- Environmental Sciences Department, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973
| | - Cleveland J. Dodge
- Environmental Sciences Department, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973
| | - Arokiasamy J. Francis
- Environmental Sciences Department, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973
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Can microbially-generated hydrogen sulfide account for the rates of U(VI) reduction by a sulfate-reducing bacterium? Biodegradation 2009; 21:81-95. [PMID: 19597947 DOI: 10.1007/s10532-009-9283-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2009] [Accepted: 06/25/2009] [Indexed: 10/20/2022]
Abstract
In situ remediation of uranium contaminated soil and groundwater is attractive because a diverse range of microbial and abiotic processes reduce soluble and mobile U(VI) to sparingly soluble and immobile U(IV). Often these processes are linked. Sulfate-reducing bacteria (SRB), for example, enzymatically reduce U(VI) to U(IV), but they also produce hydrogen sulfide that can itself reduce U(VI). This study evaluated the relative importance of these processes for Desulfovibrio aerotolerans, a SRB isolated from a U(VI)-contaminated site. For the conditions evaluated, the observed rate of SRB-mediated U(VI) reduction can be explained by the abiotic reaction of U(VI) with the microbially-generated H(2)S. The presence of trace ferrous iron appeared to enhance the extent of hydrogen sulfide-mediated U(VI) reduction at 5 mM bicarbonate, but had no clear effect at 15 mM. During the hydrogen sulfide-mediated reduction of U(VI), a floc formed containing uranium and sulfur. U(VI) sequestered in the floc was not available for further reduction.
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Thioredoxin is involved in U(VI) and Cr(VI) reduction in Desulfovibrio desulfuricans G20. J Bacteriol 2009; 191:4924-33. [PMID: 19482922 DOI: 10.1128/jb.00197-09] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A transposon insertion mutant has been identified in a Desulfovibrio desulfuricans G20 mutant library that does not grow in the presence of 2 mM U(VI) in lactate-sulfate medium. This mutant has also been shown to be deficient in the ability to grow with 100 microM Cr(VI) and 20 mM As(V). Experiments with washed cells showed that this mutant had lost the ability to reduce U(VI) or Cr(VI), providing an explanation for the lower tolerance. A gene encoding a cyclic AMP (cAMP) receptor protein (CRP) was identified as the site of the transposon insertion. The remainder of the mre operon (metal reduction) contains genes encoding a thioredoxin, thioredoxin reductase, and an additional oxidoreductase whose substrate has not been predicted. Expression studies showed that in the mutant, the entire operon is downregulated, suggesting that the CRP may be involved in regulating expression of the whole operon. Exposure of the cells to U(VI) resulted in upregulation of the entire operon. CdCl(2), a specific inhibitor of thioredoxin activity, inhibits U(VI) reduction by washed cells and inhibits growth of cells in culture when U(VI) is present, confirming a role for thioredoxin in U(VI) reduction. The entire mre operon was cloned into Escherichia coli JM109 and the transformant developed increased U(VI) resistance and the ability to reduce U(VI) to U(IV). The oxidoreductase protein (MreG) from this operon was expressed and purified from E. coli. In the presence of thioredoxin, thioredoxin reductase, and NADPH, this protein was shown to reduce both U(VI) and Cr(VI), providing a mechanism for the cytoplasmic reduction of these metals.
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Gavrilescu M, Pavel LV, Cretescu I. Characterization and remediation of soils contaminated with uranium. JOURNAL OF HAZARDOUS MATERIALS 2009; 163:475-510. [PMID: 18771850 DOI: 10.1016/j.jhazmat.2008.07.103] [Citation(s) in RCA: 256] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2007] [Revised: 07/23/2008] [Accepted: 07/23/2008] [Indexed: 05/13/2023]
Abstract
Environmental contamination caused by radionuclides, in particular by uranium and its decay products is a serious problem worldwide. The development of nuclear science and technology has led to increasing nuclear waste containing uranium being released and disposed in the environment. The objective of this paper is to develop a better understanding of the techniques for the remediation of soils polluted with radionuclides (uranium in particular), considering: the chemical forms of uranium, including depleted uranium (DU) in soil and other environmental media, their characteristics and concentrations, and some of the effects on environmental and human health; research issues concerning the remediation process, the benefits and results; a better understanding of the range of uses and situations for which each is most appropriate. The paper addresses the main features of the following techniques for uranium remediation: natural attenuation, physical methods, chemical processes (chemical extraction methods from contaminated soils assisted by various suitable chelators (sodium bicarbonate, citric acid, two-stage acid leaching procedure), extraction using supercritical fluids such as solvents, permeable reactive barriers), biological processes (biomineralization and microbial reduction, phytoremediation, biosorption), and electrokinetic methods. In addition, factors affecting uranium removal from soils are furthermore reviewed including soil characteristics, pH and reagent concentration, retention time.
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Affiliation(s)
- Maria Gavrilescu
- Technical University Iasi, Faculty of Chemical Engineering and Environmental Protection, Department of Environmental Engineering and Management, 71 Mangeron Boulevard, 700050 Iasi, Romania.
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Plutonium(V/VI) Reduction by the Metal-Reducing Bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1. Appl Environ Microbiol 2009; 75:3641-7. [PMID: 19363069 DOI: 10.1128/aem.00022-09] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We examined the ability of the metal-reducing bacteria Geobacter metallireducens GS-15 and Shewanella oneidensis MR-1 to reduce Pu(VI) and Pu(V). Cell suspensions of both bacteria reduced oxidized Pu [a mixture of Pu(VI) and Pu(V)] to Pu(IV). The rate of plutonium reduction was similar to the rate of U(VI) reduction obtained under similar conditions for each bacteria. The rates of Pu(VI) and U(VI) reduction by cell suspensions of S. oneidensis were slightly higher than the rates observed with G. metallireducens. The reduced form of Pu was characterized as aggregates of nanoparticulates of Pu(IV). Transmission electron microscopy images of the solids obtained from the cultures after the reduction of Pu(VI) and Pu(V) by S. oneidensis show that the Pu precipitates have a crystalline structure. The nanoparticulates of Pu(IV) were precipitated on the surface of or within the cell walls of the bacteria. The production of Pu(III) was not observed, which indicates that Pu(IV) was the stable form of reduced Pu under these experimental conditions. Experiments examining the ability of these bacteria to use Pu(VI) as a terminal electron acceptor for growth were inconclusive. A slight increase in cell density was observed for both G. metallireducens and S. oneidensis when Pu(VI) was provided as the sole electron acceptor; however, Pu(VI) concentrations decreased similarly in both the experimental and control cultures.
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Biffinger J, Ribbens M, Ringeisen B, Pietron J, Finkel S, Nealson K. Characterization of electrochemically active bacteria utilizing a high-throughput voltage-based screening assay. Biotechnol Bioeng 2009; 102:436-44. [DOI: 10.1002/bit.22072] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Tokunaga TK, Wan J, Kim Y, Daly RA, Brodie EL, Hazen TC, Herman D, Firestone MK. Influences of organic carbon supply rate on uranium bioreduction in initially oxidizing, contaminated sediment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:8901-8907. [PMID: 19192816 DOI: 10.1021/es8019947] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Remediation of uranium-contaminated sediments through in situ stimulation of bioreduction to insoluble UO2 is a potential treatment strategy under active investigation. Previously, we found that newly reduced U(IV) can be reoxidized under reducing conditions sustained by a continuous supply of organic carbon (OC) because of residual reactive Fe(III) and enhanced U(VI) solubilitythrough complexation with carbonate generated through OC oxidation. That finding motivated this investigation directed at identifying a range of OC supply rates that is optimal for establishing U bioreduction and immobilization in initially oxidizing sediments. The effects of OC supply rate, from 0 to 580 mmol of OC (kg of sediment)(-1) year(-1), and OC form (lactate and acetate) on U bioreduction were tested in flow-through columns containing U-contaminated sediments. An intermediate supply rate on the order of 150 mmol of OC (kg of sediment)(-1) year(-1) was determined to be most effective at immobilizing U. At lower OC supply rates, U bioreduction was not achieved, and U(VI) solubilitywas enhanced by complexation with carbonate (from OC oxidation). At the highest OC supply rate, the resulting highly carbonate-enriched solutions also supported elevated levels of U(VI), even though strongly reducing conditions were established. Lactate and acetate were found to have very similar geochemical impacts on effluent U concentrations (and other measured chemical species), when compared at equivalent OC supply rates. While the catalysts of U(VI) reduction to U(IV) are presumably bacteria, the composition of the bacterial community,the Fe-reducing community, and the sulfate-reducing community had no direct relationship with effluent U concentrations. The OC supply rate has competing effects of driving reduction of U(VI) to low-solubility U(IV) solids, as well as causing formation of highly soluble U(VI)-carbonato complexes. These offsetting influences will require careful control of OC supply rates in order to optimize bioreduction-based U stabilization.
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Affiliation(s)
- Tetsu K Tokunaga
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, and University of California, Berkeley, California 94720, USA.
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Francis AJ, Dodge CJ. Bioreduction of uranium(VI) complexed with citric acid by Clostridia affects its structure and solubility. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:8277-8282. [PMID: 19068806 DOI: 10.1021/es801045m] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Uranium contamination of the environment from mining and milling operations, nuclear-waste disposal, and ammunition use is a widespread global problem. Natural attenuation processes such as bacterial reductive precipitation and immobilization of soluble uranium is gaining much attention. However, the presence of naturally occurring organic ligands can affect the precipitation of uranium. Here, we report that the anaerobic spore-forming bacteria Clostridia, ubiquitous in soils, sediments, and wastes, capable of reduction of Fe(III) to Fe(II), Mn(IV) to Mn(II), U(VI) to U(IV), Pu(IV) to Pu(III), and Tc(VI) to Tc(IV); reduced U(VI) associated with citric acid in a dinuclear 2:2 U(VI): citric acid complex to a biligand mononuclear 1:2 U(IV):citric acid complex,which remained in solution, in contrast to reduction and precipitation of uranium. Our findings show that U(VI) complexed with citric acid is readily accessible as an electron acceptor despite the inability of the bacterium to metabolize the complexed organic ligand. Furthermore, it suggests that the presence of organic ligands at uranium-contaminated sites can affect the mobility of the actinide under both oxic and anoxic conditions by forming such soluble complexes.
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Affiliation(s)
- A J Francis
- Environmental Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
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Wan J, Tokunaga TK, Kim Y, Brodie E, Daly R, Hazen TC, Firestone MK. Effects of organic carbon supply rates on uranium mobility in a previously bioreduced contaminated sediment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:7573-7579. [PMID: 18983077 DOI: 10.1021/es800951h] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Bioreduction-based strategies for remediating uranium (U)-contaminated sediments face the challenge of maintaining the reduced status of U for long times. Because groundwater influxes continuously bring in oxidizing terminal electron acceptors (O2, NO3(-)), it is necessary to continue supplying organic carbon (OC) to maintain the reducing environment after U bioreduction is achieved. We tested the influence of OC supply rates on mobility of previously microbial reduced uranium U(IV) in contaminated sediments. We found that high degrees of U mobilization occurred when OC supply rates were high, and when the sediment still contained abundant Fe(III). Although 900 days with low levels of OC supply minimized U mobilization, the sediment redox potential increased with time as did extractable U(VI) fractions. Molecular analyses of total microbial activity demonstrated a positive correlation with OC supply and analyses of Geobacteraceae activity (RT-qPCR of 16S rRNA) indicated continued activity even when the effluent Fe(II) became undetectable. These data support our hypothesis on the mechanisms responsible for remobilization of U under reducing conditions; that microbial respiration caused increased (bi)carbonate concentration and formation of stable uranyl carbonate complexes, thereby shifted U(IV)/U(VI) equilibrium to more reducing potentials. The data also suggested that low OC concentrations could not sustain the reducing condition of the sediment for much longer time. Bioreduced U(IV) is not sustainable in an oxidizing environment for a very long time.
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Affiliation(s)
- Jiamin Wan
- Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
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Sani RK, Peyton BM, Dohnalkova A. Comparison of uranium(VI) removal by Shewanella oneidensis MR-1 in flow and batch reactors. WATER RESEARCH 2008; 42:2993-3002. [PMID: 18468655 DOI: 10.1016/j.watres.2008.04.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2007] [Revised: 03/21/2008] [Accepted: 04/01/2008] [Indexed: 05/26/2023]
Abstract
To better understand the interactions among metal contaminants, nutrients, and microorganisms in subsurface fracture-flow systems, biofilms of pure culture of Shewanella oneidensis MR-1 were grown in six fracture-flow reactors (FFRs) of different geometries. The spatial and temporal distribution of uranium and bacteria were examined using a tracer dye (brilliant blue FCF) and microscopy. The results showed that plugging by bacterial cells was dependent on the geometry of the reactor and that biofilms grown in FFRs had a limited U(VI)-reduction capacity. To quantify the U(VI)-reduction capacity of biofilms, batch experiments for U(VI) reduction were performed with repetitive U(VI) additions. U(VI)-reduction rates of stationary phase cultures decreased after each U(VI) addition. After the fourth U(VI) addition, stationary phase cultures treated with U(VI) with and without spent medium yielded gray and black precipitates, respectively. These gray and black U precipitates were analyzed using high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Data for randomly selected areas of black precipitates showed that reduced U particles (3-6 nm) were crystalline, whereas gray precipitates were a mixture of crystalline and amorphous solids. Results obtained in this study, including a dramatic limitation of S. oneidensis MR-1 and its biofilms to reduce U(VI) and plugging of FFRs, suggest that alternative organisms should be targeted for stimulation for metal immobilization in subsurface fracture-flow systems.
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Affiliation(s)
- Rajesh K Sani
- Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701, USA.
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Neiss J, Stewart BD, Nico PS, Fendorf S. Speciation-dependent microbial reduction of uranium within iron-coated sands. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:7343-7348. [PMID: 18044509 DOI: 10.1021/es0706697] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Transport of uranium within surface and subsurface environments is predicated largely on its redox state. Uranyl reduction may transpire through either biotic (enzymatic) or abiotic pathways; in either case, reduction of U(VI) to U(IV) results in the formation of sparingly soluble UO2 precipitates. Biological reduction of U(VI), while demonstrated as prolific under both laboratory and field conditions, is influenced by competing electron acceptors (such as nitrate, manganese oxides, or iron oxides) and uranyl speciation. Formation of Ca-UO2-CO3 ternary complexes, often the predominate uranyl species in carbonate-bearing soils and sediments, decreases the rate of dissimilatory U(VI) reduction. The combined influence of uranyl speciation within a mineralogical matrix comparable to natural environments and under hydrodynamic conditions, however, remains unresolved. We therefore examined uranyl reduction by Shewanella putrefaciens within packed mineral columns of ferrihydrite-coated quartz sand under conditions conducive or nonconducive to Ca-UO2-CO3 species formation. The results are dramatic. In the absence of Ca, where uranyl carbonato complexes dominate, U(VI) reduction transpires and consumes all of the U(VI) within the influent solution (0.166 mM) over the first 2.5 cm of the flow field for the entirety of the 54 d experiment. Over 2 g of U is deposited during this reaction period, and despite ferrihydrite being a competitive electron acceptor, uranium reduction appears unabated for the duration of our experiments. By contrast, in columns with 4 mM Ca in the influent solution (0.166 mM uranyl), reduction (enzymatic or surface-bound Fe(III) mediated) appears absent and breakthrough occurs within 18 d (at a flow rate of 3 pore volumes per day). Uranyl speciation, and in particular the formation of ternary Ca-UO2-CO3 complexes, has a profound impact on U(VI) reduction and thus transport within anaerobic systems.
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Affiliation(s)
- Jim Neiss
- Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA
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Simonoff M, Sergeant C, Poulain S, Pravikoff MS. Microorganisms and migration of radionuclides in environment. CR CHIM 2007. [DOI: 10.1016/j.crci.2007.02.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Electron crystallography of the scrapie prion protein complexed with heavy metals. Arch Biochem Biophys 2007; 467:239-48. [PMID: 17935686 DOI: 10.1016/j.abb.2007.08.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Accepted: 08/09/2007] [Indexed: 11/21/2022]
Abstract
The insolubility of the disease-causing isoform of the prion protein (PrP(Sc)) has prevented studies of its three-dimensional structure at atomic resolution. Electron crystallography of two-dimensional crystals of N-terminally truncated PrP(Sc) (PrP 27-30) and a miniprion (PrP(Sc)106) provided the first insights at intermediate resolution on the molecular architecture of the prion. Here, we report on the structure of PrP 27-30 and PrP(Sc)106 negatively stained with heavy metals. The interactions of the heavy metals with the crystal lattice were governed by tertiary and quaternary structural elements of the protein as well as the charge and size of the heavy metal salts. Staining with molybdate anions revealed three prominent densities near the center of the trimer that forms the unit cell, coinciding with the location of the beta-helix that was proposed for the structure of PrP(Sc). Differential staining also confirmed the location of the internal deletion of PrP(Sc)106 at or near these densities.
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Luo J, Weber FA, Cirpka OA, Wu WM, Nyman JL, Carley J, Jardine PM, Criddle CS, Kitanidis PK. Modeling in-situ uranium(VI) bioreduction by sulfate-reducing bacteria. JOURNAL OF CONTAMINANT HYDROLOGY 2007; 92:129-48. [PMID: 17291626 DOI: 10.1016/j.jconhyd.2007.01.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2005] [Revised: 09/28/2006] [Accepted: 01/03/2007] [Indexed: 05/13/2023]
Abstract
We present a travel-time based reactive transport model to simulate an in-situ bioremediation experiment for demonstrating enhanced bioreduction of uranium(VI). The model considers aquatic equilibrium chemistry of uranium and other groundwater constituents, uranium sorption and precipitation, and the microbial reduction of nitrate, sulfate and U(VI). Kinetic sorption/desorption of U(VI) is characterized by mass transfer between stagnant micro-pores and mobile flow zones. The model describes the succession of terminal electron accepting processes and the growth and decay of sulfate-reducing bacteria, concurrent with the enzymatic reduction of aqueous U(VI) species. The effective U(VI) reduction rate and sorption site distributions are determined by fitting the model simulation to an in-situ experiment at Oak Ridge, TN. Results show that (1) the presence of nitrate inhibits U(VI) reduction at the site; (2) the fitted effective rate of in-situ U(VI) reduction is much smaller than the values reported for laboratory experiments; (3) U(VI) sorption/desorption, which affects U(VI) bioavailability at the site, is strongly controlled by kinetics; (4) both pH and bicarbonate concentration significantly influence the sorption/desorption of U(VI), which therefore cannot be characterized by empirical isotherms; and (5) calcium-uranyl-carbonate complexes significantly influence the model performance of U(VI) reduction.
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Affiliation(s)
- Jian Luo
- Stanford University, Department of Civil and Environmental Engineering, Stanford, CA 94305-4020, USA.
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Icopini GA, Boukhalfa H, Neu MP. Biological reduction of Np(V) and Np(V) citrate by metal-reducing bacteria. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2007; 41:2764-9. [PMID: 17533836 DOI: 10.1021/es0618550] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Oxidized actinide species are often more mobile than reduced forms. Bioremediation strategies have been developed to exploit this chemistry and stabilize actinides in subsurface environments. We investigated the ability of metal-reducing bacteria Geobacter metallireducens and Shewanella oneidensis to enzymatically reduce Np(V) and Np(V) citrate, as well as the toxicity of Np(V) to these organisms. A toxic effect was observed for both bacteria at concentrations of > or = 4.0 mM Np(V) citrate. Below 2.0 mM Np(V) citrate, no toxic effect was observed and both Fe(III) and Np(V) were reduced. Cell suspensions of S. oneidensis were able to enzymatically reduce unchelated Np(V) to insoluble Np(IV)(s), but cell suspensions of G. metallireducens were unable to reduce Np(V). The addition of citrate enhanced the Np(V) reduction rate by S. oneidensisand enabled Np(V) reduction by G. metallireducens. The reduced form of neptunium remained soluble, presumably as a polycitrate complex. Growth was not observed for either organism when Np(V) or Np(V) citrate was provided as the sole terminal electron acceptor. Our results show that bacteria can enzymatically reduce Np(V) and Np(V) citrate, but that the immobilization of Np(IV) may be dependent on the abundance of complexing ligands.
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Affiliation(s)
- Gary A Icopini
- Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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Elias DA, Yang F, Mottaz HM, Beliaev AS, Lipton MS. Enrichment of functional redox reactive proteins and identification by mass spectrometry results in several terminal Fe(III)-reducing candidate proteins in Shewanella oneidensis MR-1. J Microbiol Methods 2006; 68:367-75. [PMID: 17137661 DOI: 10.1016/j.mimet.2006.09.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Revised: 09/14/2006] [Accepted: 09/15/2006] [Indexed: 10/23/2022]
Abstract
Identification of the proteins directly involved in microbial metal-reduction is important to understanding the biochemistry involved in heavy metal-reduction/immobilization and the ultimate cleanup of DOE contaminated sites. Although previous strategies for the identification of these proteins have traditionally required laborious protein purification/characterization of metal-reducing capability, activity is often lost before the final purification step, thus creating a significant knowledge gap. In the current study, subcellular fractions of Shewanella oneidensis MR-1 were enriched for Fe(III)-NTA reducing proteins in a single step using several orthogonal column matrices. The protein content of eluted fractions that demonstrated activity was determined by ultra-high pressure liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). A comparison of the proteins identified from active fractions in all separations produced 30 proteins that may act as the terminal electron-accepting protein for Fe(III)-reduction. These include MtrA, MtrB, MtrC and OmcA as well as a number of other proteins not previously associated with Fe(III)-reduction. This is the first report of such an approach where the laborious procedures for protein purification are not required for identification of metal-reducing proteins. Such work provides the basis for a similar approach with other cultured organisms as well as analysis of sediment and groundwater samples from biostimulation efforts at contaminated sites.
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Affiliation(s)
- Dwayne A Elias
- Department of Biochemistry, University of Missouri-Columbia, United States
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Abstract
The dramatic decrease in solubility accompanying the reduction of U(VI) to U(IV), producing the insoluble mineral uraninite, has been viewed as a potential mechanism for sequestration of environmental uranium contamination. In the past 15 years, it has been firmly established that a variety of bacteria exhibit this reductive capacity. To obtain an understanding of the microbial metal metabolism, to develop a practical approach for the acceleration of in situ bioreduction, and to predict the long-term fate of environmental uranium, several aspects of the microbial process have been experimentally explored. This review briefly addresses the research to identify specific uranium reductases and their cellular location, competition between uranium and other electron acceptors, attempts to stimulate in situ reduction, and mechanisms of reoxidation of reduced uranium minerals.
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Affiliation(s)
- Judy D Wall
- Biochemistry and Molecular Microbiology & Immunology, University of Missouri-Columbia, Columbia, Missouri 65211, USA.
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Wu Q, Sanford RA, Löffler FE. Uranium(VI) reduction by Anaeromyxobacter dehalogenans strain 2CP-C. Appl Environ Microbiol 2006; 72:3608-14. [PMID: 16672509 PMCID: PMC1472366 DOI: 10.1128/aem.72.5.3608-3614.2006] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies demonstrated growth of Anaeromyxobacter dehalogenans strain 2CP-C with acetate or hydrogen as the electron donor and Fe(III), nitrate, nitrite, fumarate, oxygen, or ortho-substituted halophenols as electron acceptors. In this study, we explored and characterized U(VI) reduction by strain 2CP-C. Cell suspensions of fumarate-grown 2CP-C cells reduced U(VI) to U(IV). More-detailed growth studies demonstrated that hydrogen was the required electron donor for U(VI) reduction and could not be replaced by acetate. The addition of nitrate to U(VI)-reducing cultures resulted in a transitory increase in U(VI) concentration, apparently caused by the reoxidation of reduced U(IV), but U(VI) reduction resumed following the consumption of N-oxyanions. Inhibition of U(VI) reduction occurred in cultures amended with Fe(III) citrate, or citrate. In the presence of amorphous Fe(III) oxide, U(VI) reduction proceeded to completion but the U(VI) reduction rates decreased threefold compared to control cultures. Fumarate and 2-chlorophenol had no inhibitory effects on U(VI) reduction, and both electron acceptors were consumed concomitantly with U(VI). Since cocontaminants (e.g., nitrate, halogenated compounds) and bioavailable ferric iron are often encountered at uranium-impacted sites, the metabolic versatility makes Anaeromyxobacter dehalogenans a promising model organism for studying the complex interaction of multiple electron acceptors in U(VI) reduction and immobilization.
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Affiliation(s)
- Qingzhong Wu
- School of Civil and Environmental Engineering, Georgia Institute of Technology, 311 Ferst Drive, 3228 ES&T Building, Atlanta, GA 30332-0512, USA
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Wu WM, Carley J, Gentry T, Ginder-Vogel MA, Fienen M, Mehlhorn T, Yan H, Caroll S, Pace MN, Nyman J, Luo J, Gentile ME, Fields MW, Hickey RF, Gu B, Watson D, Cirpka OA, Zhou J, Fendorf S, Kitanidis PK, Jardine PM, Criddle CS. Pilot-scale in situ bioremedation of uranium in a highly contaminated aquifer. 2. Reduction of u(VI) and geochemical control of u(VI) bioavailability. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2006; 40:3986-95. [PMID: 16830572 DOI: 10.1021/es051960u] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
In situ microbial reduction of soluble U(VI) to sparingly soluble U(IV) was evaluated at the site of the former S-3 Ponds in Area 3 of the U.S. Department of Energy Natural and Accelerated Bioremediation Research Field Research Center, Oak Ridge, TN. After establishing conditions favorable for bioremediation (Wu, et al. Environ. Sci. Technol. 2006, 40, 3988-3995), intermittent additions of ethanol were initiated within the conditioned inner loop of a nested well recirculation system. These additions initially stimulated denitrification of matrix-entrapped nitrate, but after 2 months, aqueous U levels fell from 5 to approximately 1 microM and sulfate reduction ensued. Continued additions sustained U(VI) reduction over 13 months. X-ray near-edge absorption spectroscopy (XANES) confirmed U(VI) reduction to U(IV) within the inner loop wells, with up to 51%, 35%, and 28% solid-phase U(IV) in sediment samples from the injection well, a monitoring well, and the extraction well, respectively. Microbial analyses confirmed the presence of denitrifying, sulfate-reducing, and iron-reducing bacteria in groundwater and sediments. System pH was generally maintained at less than 6.2 with low bicarbonate level (0.75-1.5 mM) and residual sulfate to suppress methanogenesis and minimize uranium mobilization. The bioavailability of sorbed U(VI) was manipulated by addition of low-level carbonate (< 5 mM) followed by ethanol (1-1.5 mM). Addition of low levels of carbonate increased the concentration of aqueous U, indicating an increased rate of U desorption due to formation of uranyl carbonate complexes. Upon ethanol addition, aqueous U(VI) levels fell, indicating that the rate of microbial reduction exceeded the rate of desorption. Sulfate levels simultaneously decreased, with a corresponding increase in sulfide. When ethanol addition ended but carbonate addition continued, soluble U levels increased, indicating faster desorption than reduction. When bicarbonate addition stopped, aqueous U levels decreased, indicating adsorption to sediments. Changes in the sequence of carbonate and ethanol addition confirmed that carbonate-controlled desorption increased bioavailability of U(VI) for reduction.
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Affiliation(s)
- Wei-Min Wu
- Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, USA
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Groh JL, Luo Q, Ballard JD, Krumholz LR. A method adapting microarray technology for signature-tagged mutagenesis of Desulfovibrio desulfuricans G20 and Shewanella oneidensis MR-1 in anaerobic sediment survival experiments. Appl Environ Microbiol 2005; 71:7064-74. [PMID: 16269742 PMCID: PMC1287673 DOI: 10.1128/aem.71.11.7064-7074.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Signature-tagged mutagenesis (STM) is a powerful technique that can be used to identify genes expressed by bacteria during exposure to conditions in their natural environments. To date, there have been no reports of studies in which this approach was used to study organisms of environmental, rather than pathogenic, significance. We used a mini-Tn10 transposon-bearing plasmid, pBSL180, that efficiently and randomly mutagenized Desulfovibrio desulfuricans G20 in addition to Shewanella oneidensis MR-1. Using these organisms as model sediment-dwelling anaerobic bacteria, we developed a new screening system, modified from former STM procedures, to identify genes that are critical for sediment survival. The screening system uses microarray technology to visualize tags from input and output pools, allowing us to identify those lost during sediment incubations. While the majority of data on survival genes identified will be presented in future papers, we report here on chemotaxis-related genes identified by our STM method in both bacteria in order to validate our method. This system may be applicable to the study of numerous environmental bacteria, allowing us to identify functions and roles of survival genes in various habitats.
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Affiliation(s)
- Jennifer L Groh
- Department of Botany and Microbiology, University of Oklahoma, Norman, OK 73019, USA
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Lee BD, Walton MR, Megio JL. Biological and chemical interactions with U(VI) during anaerobic enrichment in the presence of iron oxide coated quartz. WATER RESEARCH 2005; 39:4363-74. [PMID: 16236343 DOI: 10.1016/j.watres.2005.09.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2003] [Revised: 05/19/2005] [Accepted: 09/08/2005] [Indexed: 05/04/2023]
Abstract
Microcosm experiments were performed to understand chemical and biological interactions with hexavalent uranium (U(VI)) in the presence of iron oxide bearing minerals and trichloroethylene (TCE) as a co-contaminant. Interactions of U(VI) and hydrous iron oxide moieties on the mineral oxide surfaces were studied during enrichments for dissimilatory iron reducing (DIRB) and sulfate reducing bacteria (SRB). Microbes enriched from groundwater taken from the Test Area North (TAN) site at the Idaho National Laboratory (INL) were able to reduce the U(VI) in the adsorption medium as well as the iron on quartz surfaces. Early in the experiment disappearance of U(VI) from solution was a function of chemical interactions since no microbial activity was evident. Abiotic removal of U(VI) was enhanced in the presence of carbonate. As the experiment proceeded, further removal of U(VI) from solution was associated with the fermentation of lactate to propionate and acetate. During later phases of the experiment when lactate was depleted from the growth medium in the microcosm containing the DIRB enrichments, U(VI) concentrations in the solution phase increased until additional lactate was added. When additional lactate was added and fermentation proceeded, U(VI) concentrations in the liquid phase again returned to near zero. Similar results were shown for the SRB enrichment but lower uranium concentrations were seen in the liquid phase, while in the enrichment with carbonate a similar increase in uranium concentration was not seen. Chemical and biological interactions appear to be important on the mobilization/immobilization of U(VI) in an iron oxide system when TCE is present as a co-contaminant. Interestingly, TCE present in the microcosm experiments was not dechlorinated which was probably an effect of redox conditions that were unsuitable for reductive dechlorination by the microbial culture tested.
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Affiliation(s)
- Brady D Lee
- Biological Sciences Department, Idaho National Laboratory, P. O. Box 1625, Idaho Falls, ID 83415, USA.
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Wan J, Tokunaga TK, Brodie E, Wang Z, Zheng Z, Herman D, Hazen TC, Firestone MK, Sutton SR. Reoxidation of bioreduced uranium under reducing conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2005; 39:6162-9. [PMID: 16173577 DOI: 10.1021/es048236g] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Nuclear weapons and fuel production have left many soils and sediments contaminated with toxic levels of uranium (U). Although previous short-term experiments on microbially mediated U(VI) reduction have supported the prospect of immobilizing the toxic metal through formation of insoluble U(IV) minerals, our longer-term (17 months) laboratory study showed that microbial reduction of U can be transient, even under sustained reducing conditions. Uranium was reduced during the first 80 days, but later (100-500 days) reoxidized and solubilized, even though a microbial community capable of reducing U(VI) was sustained. Microbial respiration caused increases in (bi)-carbonate concentrations and formation of very stable uranyl carbonate complexes, thereby increasing the thermodynamic favorability of U(IV) oxidation. We propose that kinetic limitations including restricted mass transfer allowed Fe-(III) and possibly Mn(IV) to persist as terminal electron acceptors (TEAs) for U reoxidation. These results show that in-situ U remediation by organic carbon-based reductive precipitation can be problematic in sediments and groundwaters with neutral to alkaline pH, where uranyl carbonates are most stable.
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Affiliation(s)
- Jiamin Wan
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
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Gu B, Yan H, Zhou P, Watson DB, Park M, Istok J. Natural humics impact uranium bioreduction and oxidation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2005; 39:5268-75. [PMID: 16082956 DOI: 10.1021/es050350r] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Although humic substances occur ubiquitously in soil and groundwater, their effect on the biological reduction of uranium(VI) and subsequent reoxidation of U(IV) is poorly understood. This study investigated the role of humics in enhancing the bioreduction of U(VI) in laboratory kinetic studies, in field push-pull tests, and in the presence or absence of metal ions such as Ca2+ and Ni2+, which are known to inhibit the biological reduction of U(VI). Results from laboratory experiments indicate that, under strict anaerobic conditions, the presence of humic materials enhanced the U(VI) reduction rates (up to 10-fold) and alleviated the toxicity effect of Ni2+ on microorganisms. Humic acid was found to be more effective than fulvic acid in enhancing the reduction of U(VI). Such an enhancement effect is attributed to the ability of these humics in facilitating electron-transfer reactions and/or in complexing Ca2+ and Ni2+ ions. Similarly, field push-pull tests demonstrated a substantially increased rate of U(VI) reduction when humic acid was introduced into the site groundwater. However, humics were also found to form complexes with reduced U(IV) and increased the oxidation of U(IV) (when exposed to oxygen) with an oxidation halflife on the order of a few minutes. Both of these processes render uranium soluble and potentially mobile in groundwater, depending on site-specific and dynamic geochemical conditions. Future studies must address the stability and retention of reduced U(IV) under realistic field conditions (e.g., in the presence of dissolved oxygen and low concentrations of complexing organics).
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Affiliation(s)
- Baohua Gu
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
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Zhou P, Gu B. Extraction of oxidized and reduced forms of uranium from contaminated soils: effects of carbonate concentration and pH. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2005; 39:4435-40. [PMID: 16047778 DOI: 10.1021/es0483443] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Uranium may present in soil as precipitated, sorbed, complexed, and reduced forms, which impact its mobility and fate in the subsurface soil environment. In this study, a uranium-contaminated soil was extracted with carbonate/ bicarbonate at varying concentrations (0-1 M), pHs, and redox conditions in an attempt to evaluate their effects on the extraction efficiency and selectivity for various forms of uranium in the soil. Results indicate that at least three differentforms of uranium existed in the contaminated soil: uranium(VI) phosphate minerals, reduced U(IV) phases, and U(VI) complexed with soil organic matter. A small fraction of U(VI) could be sorbed onto soil minerals. The mechanism involved in the leaching of U(VI) by carbonates appears to involve three processes which may act concurrently or independently: the dissolution of uranium(VI) phosphate and other mineral phases, the oxidation-complexation of U(IV) under oxic conditions, and the desorption of U(VI)-organic matter complexes at elevated pH conditions. This study suggests that, depending on site-specific geochemical conditions, the presence of small quantities of carbonate/bicarbonate could result in a rapid and greatly increased leaching and the mobilization of U(VI) from the contaminated soil. Even the reduced U(IV) phases (only sparingly soluble in water) are subjected to rapid oxidation and therefore potential leaching into the environment.
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Affiliation(s)
- Ping Zhou
- Environmental Sciences Division, Oak Ridge National Laboratory, MS 6036, PO Box 2008, Oak Ridge, Tennessee 37831, USA
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Abdelouas A, Grambow B, Fattahi M, Andrès Y, Leclerc-Cessac E. Microbial reduction of 99Tc in organic matter-rich soils. THE SCIENCE OF THE TOTAL ENVIRONMENT 2005; 336:255-268. [PMID: 15589263 DOI: 10.1016/j.scitotenv.2004.06.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2004] [Revised: 05/28/2004] [Accepted: 06/07/2004] [Indexed: 05/24/2023]
Abstract
For safety assessment purposes, it is necessary to study the mobility of long-lived radionuclides in the geosphere and the biosphere. Within this framework, we studied the behaviour of (99)Tc in biologically active organic matter-rich soils. To simulate the redox conditions in soils, we stimulated the growth of aerobic and facultative denitrifying and anaerobic sulphate-reducing bacteria (SRB). In the presence of either a pure culture of denitrifiers (Pseudomonas aeruginosa) or a consortium of soil denitrifiers, the solubility of TcO(4)(-) was not affected. The nonsorption of TcO(4)(-) onto bacteria was confirmed in biosorption experiments with washed cells of P. aeruginosa regardless of the pH. At the end of denitrification with indigenous denitrifiers in soil/water batch experiments, the redox potential (E(H)) dropped and this was accompanied by an increase of Fe concentration in solution as a result of reduction of less soluble Fe(III) to Fe(II) from the soil particles. It is suggested that this is due to the growth of a consortium of anaerobic bacteria (e.g., Fe-reducing bacteria). The drop in E(H) was accompanied by a strong decrease in Tc concentration as a result of Tc(VII) reduction to Tc(IV). Thermodynamic calculations suggested the precipitation of TcO(2). The stimulation of the growth of indigenous sulphate-reducing bacteria in soil/water systems led to even lower E(H) with final Tc concentration of 10(-8) M. Experiments with glass columns filled with soil reproduced the results obtained with batch cultures. Sequential chemical extraction of precipitated Tc in soils showed that this radionuclide is strongly immobilised within soil particles under anaerobic conditions. More than 90% of Tc is released together with organic matter (60-66%) and Fe-oxyhydroxides (23-31%). The present work shows that ubiquitous indigenous anaerobic bacteria in soils play a major role in Tc immobilisation. In addition, organic matter plays a key role in the stability of the reduced Tc.
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Affiliation(s)
- A Abdelouas
- Ecole des Mines de Nantes, SUBATECH (UMR 6457), 4, rue Alfred Kastler-La chantrerie, BP 20722, 44307 Nantes Cedex 3, France.
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Kalin M, Wheeler WN, Meinrath G. The removal of uranium from mining waste water using algal/microbial biomass. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2005; 78:151-177. [PMID: 15511557 DOI: 10.1016/j.jenvrad.2004.05.002] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2003] [Revised: 03/01/2004] [Accepted: 05/04/2004] [Indexed: 05/24/2023]
Abstract
We describe a three step process for the removal of uranium (U) from dilute waste waters. Step one involves the sequestration of U on, in, and around aquatic plants such as algae. Cell wall ligands efficiently remove U(VI) from waste water. Growing algae continuously renew the cellular surface area. Step 2 is the removal of U-algal particulates from the water column to the sediments. Step 3 involves reducing U(VI) to U(IV) and transforming the ions into stable precipitates in the sediments. The algal cells provide organic carbon and other nutrients to heterotrophic microbial consortia to maintain the low E(H), within which the U is transformed. Among the microorganisms, algae are of predominant interest for the ecological engineer because of their ability to sequester U and because some algae can live under many extreme environments, often in abundance. Algae grow in a wide spectrum of water qualities, from alkaline environments (Chara, Nitella) to acidic mine drainage waste waters (Mougeotia, Ulothrix). If they could be induced to grow in waste waters, they would provide a simple, long-term means to remove U and other radionuclides from U mining effluents. This paper reviews the literature on algal and microbial adsorption, reduction, and transformation of U in waste streams, wetlands, lakes and oceans.
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Affiliation(s)
- Margarete Kalin
- Boojum Research, 450 E. Queen St., Suite 101, Toronto, ON M5A 1T7, Canada
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