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Barker GR, West LJ, Graham JT, Abrahamsen-Mills L, Burke IT. Effect of grain size variation on strontium sorption to heterogeneous aquifer sediments. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2024; 277:107451. [PMID: 38851005 DOI: 10.1016/j.jenvrad.2024.107451] [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: 03/27/2024] [Revised: 05/09/2024] [Accepted: 05/13/2024] [Indexed: 06/10/2024]
Abstract
Strontium-90 (90Sr) is a major contaminant at nuclear legacy sites. The mobility of 90Sr is primarily governed by sorption reactions with sediments controlled by high surface area phases such as clay and iron oxides. Sr2+ adsorption was investigated in heterogeneous unconsolidated aquifer sediments, analogous to those underlying the UK Sellafield nuclear site, with grainsizes ranging from gravels to clays. Batch sorption tests showed that a linear Kd adsorption model was applicable to all grainsize fractions up to equilibrium [Sr] of 0.28 mmol L-1. Sr2+ sorption values (Kd; Langmuir qmax) correlated well with bulk sediment properties such as cation exchange capacity and surface area. Electron microscopy showed that heterogeneous sediments contained porous sandstone clasts with clay minerals (i.e. chlorite) providing an additional adsorption capacity. Therefore, gravel corrections that assumed that the > 2 mm fractions are inert were not appropriate and underestimated Kd(bulk) adsorption coefficients. However, Kd (<2 mm) values measured from sieved sediment fractions, were effectively adjusted to within error of Kd (bulk) using a surface area dependant gravel correction based on particle size distribution data. Amphoteric pH dependent Sr2+ sorption behaviour observed in batch experiments was consistent with cation exchange modelling between pH 2-7 derived from the measured cation exchange capacities. Above pH 7 model fits were improved by invoking a coupled cation exchange/surface complexation which allowed for addition sorption to iron oxide phases. The overall trends in Sr2+ sorption (at pH 6.5-7) produced by increasing solution ionic strength was also reproduced in cation exchange models. Overall, the results showed that Sr2+ sorption to heterogeneous sediment units could be estimated from Kd (<2 mm) data using appropriate gravel corrections, and effectively modelled using coupled cation exchange and surface complexation processes.
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Affiliation(s)
| | | | - James T Graham
- National Nuclear Laboratory Ltd., Sellafield, CA20 1PG, UK.
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2
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Wang J, Xu B. Removal of radionuclide 99Tc from aqueous solution by various adsorbents: A review. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2023; 270:107267. [PMID: 37598575 DOI: 10.1016/j.jenvrad.2023.107267] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 08/05/2023] [Indexed: 08/22/2023]
Abstract
Technetium isotope 99Tc is a main radioactive waste produced in the process of nuclear reaction, which has the characteristics of long half-life and strong environmental mobility, and can be bio-accumulated in organisms, resulting in serious threat to human health and ecosystem. Adsorption method is widely used in the field of removing radionuclides from water due to the advantages of high treatment rate, simple and mature industrial application. In this review paper, the recent advances in research and application of various adsorption materials for 99Tc pollution treatment were summarized and analyzed for the first time, including inorganic adsorbents, such as activated carbon, zero-valent iron, metallic minerals, clay minerals, layered double hydroxides (LDHs), tin-based materials, and sulfur-based materials; organic adsorbents, such as porous organic polymers (POPs), covalent-organic frameworks (COFs), metal-organic frameworks (MOFs), and ion exchange resin; and biological adsorbents, such as biopolymers (chitosan, cellulose, alginate), and microbial cells. The performance characteristics and the adsorption kinetics and isotherms of various adsorption materials were discussed. This review could deepen the understanding of the adsorptive removal of 99Tc from aqueous solution, and provide a reference for the future research in this field.
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Affiliation(s)
- Jianlong Wang
- Laboratory of Environmental Technology, INET, Tsinghua University, Beijing 100084, PR China; Beijing Key Laboratory of Radioactive Waste Treatment, INET, Tsinghua University, Beijing 100084, PR China.
| | - Bowen Xu
- Laboratory of Environmental Technology, INET, Tsinghua University, Beijing 100084, PR China
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3
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Robinson C, Shaw S, Lloyd JR, Graham J, Morris K. Phosphate (Bio)mineralization Remediation of 90Sr-Contaminated Groundwaters. ACS ES&T WATER 2023; 3:3223-3234. [PMID: 37854271 PMCID: PMC10580321 DOI: 10.1021/acsestwater.3c00159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2023] [Revised: 08/01/2023] [Accepted: 08/02/2023] [Indexed: 10/20/2023]
Abstract
Historical operations at nuclear mega-facilities such as Hanford, USA, and Sellafield, UK have led to a legacy of radioactivity-contaminated land. Calcium phosphate phases (e.g., hydroxyapatite) can adsorb and/or incorporate radionuclides, including 90Sr. Past work has shown that aqueous injection of Ca-phosphate-generating solutions into the contaminated ground on both laboratory and field scales can reduce the amount of aqueous 90Sr in the systems. Here, two microbially mediated phosphate amendment techniques which precipitated Ca-phosphate, (i) Ca-citrate/Na-phosphate and (ii) glycerol phosphate, were tested in batch experiments alongside an abiotic treatment ((iii) polyphosphate), using stable Sr and site relevant groundwaters and sediments. All three amendments led to enhanced Sr removal from the solution compared to the sediment-only control. The Ca-citrate/Na-phosphate treatment removed 97%, glycerol phosphate 60%, and polyphosphate 55% of the initial Sr. At experimental end points, scanning electron microscopy showed that Sr-containing, Ca-phosphate phases were deposited on sediment grains, and XAS analyses of the sediments amended with Ca-citrate/Na-phosphate and glycerol phosphate confirmed Sr incorporation into Ca-phosphates occurred. Overall, Ca-phosphate-generating treatments have the potential to be applied in a range of nuclear sites and are a key option within the toolkit for 90Sr groundwater remediation.
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Affiliation(s)
- Callum Robinson
- Research
Centre for Radwaste Disposal and Williamson Research Centre for Molecular
Environmental Science, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K.
| | - Samuel Shaw
- Research
Centre for Radwaste Disposal and Williamson Research Centre for Molecular
Environmental Science, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K.
| | - Jonathan R. Lloyd
- Research
Centre for Radwaste Disposal and Williamson Research Centre for Molecular
Environmental Science, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K.
| | - James Graham
- National
Nuclear Laboratory, Sellafield, Cumbria CA20 1PG, U.K.
| | - Katherine Morris
- Research
Centre for Radwaste Disposal and Williamson Research Centre for Molecular
Environmental Science, Department of Earth and Environmental Sciences, The University of Manchester, Manchester M13 9PL, U.K.
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4
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Ho MS, Vettese GF, Morris K, Lloyd JR, Boothman C, Bower WR, Shaw S, Law GTW. Retention of immobile Se(0) in flow-through aquifer column systems during bioreduction and oxic-remobilization. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 834:155332. [PMID: 35460788 DOI: 10.1016/j.scitotenv.2022.155332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Revised: 04/12/2022] [Accepted: 04/12/2022] [Indexed: 06/14/2023]
Abstract
Selenium (Se) is a toxic contaminant with multiple anthropogenic sources, including 79Se from nuclear fission. Se mobility in the geosphere is generally governed by its oxidation state, therefore understanding Se speciation under variable redox conditions is important for the safe management of Se contaminated sites. Here, we investigate Se behavior in sediment groundwater column systems. Experiments were conducted with environmentally relevant Se concentrations, using a range of groundwater compositions, and the impact of electron-donor (i.e., biostimulation) and groundwater sulfate addition was examined over a period of 170 days. X-Ray Absorption Spectroscopy and standard geochemical techniques were used to track changes in sediment associated Se concentration and speciation. Electron-donor amended systems with and without added sulfate retained up to 90% of added Se(VI)(aq), with sediment associated Se speciation dominated by trigonal Se(0) and possibly trace Se(-II); no Se colloid formation was observed. The remobilization potential of the sediment associated Se species was then tested in reoxidation and seawater intrusion perturbation experiments. In all treatments, sediment associated Se (i.e., trigonal Se(0)) was largely resistant to remobilization over the timescale of the experiments (170 days). However, in the perturbation experiments, less Se was remobilized from sulfidic sediments, suggesting that previous sulfate-reducing conditions may buffer Se against remobilization and migration.
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Affiliation(s)
- Mallory S Ho
- Radiochemistry Unit, Department of Chemistry, University of Helsinki, 00014, Finland
| | - Gianni F Vettese
- Radiochemistry Unit, Department of Chemistry, University of Helsinki, 00014, Finland
| | - Katherine Morris
- Department of Earth and Environmental Sciences, University of Manchester, M13 9PL, UK.
| | - Jonathan R Lloyd
- Department of Earth and Environmental Sciences, University of Manchester, M13 9PL, UK
| | - Christopher Boothman
- Department of Earth and Environmental Sciences, University of Manchester, M13 9PL, UK
| | - William R Bower
- Radiochemistry Unit, Department of Chemistry, University of Helsinki, 00014, Finland
| | - Samuel Shaw
- Department of Earth and Environmental Sciences, University of Manchester, M13 9PL, UK
| | - Gareth T W Law
- Radiochemistry Unit, Department of Chemistry, University of Helsinki, 00014, Finland.
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Kuippers G, Morris K, Townsend LT, Bots P, Kvashnina K, Bryan ND, Lloyd JR. Biomineralization of Uranium-Phosphates Fueled by Microbial Degradation of Isosaccharinic Acid (ISA). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:4597-4606. [PMID: 33755437 DOI: 10.1021/acs.est.0c03594] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Geological disposal is the globally preferred long-term solution for higher activity radioactive wastes (HAW) including intermediate level waste (ILW). In a cementitious disposal system, cellulosic waste items present in ILW may undergo alkaline hydrolysis, producing significant quantities of isosaccharinic acid (ISA), a chelating agent for radionuclides. Although microbial degradation of ISA has been demonstrated, its impact upon the fate of radionuclides in a geological disposal facility (GDF) is a topic of ongoing research. This study investigates the fate of U(VI) in pH-neutral, anoxic, microbial enrichment cultures, approaching conditions similar to the far field of a GDF, containing ISA as the sole carbon source, and elevated phosphate concentrations, incubated both (i) under fermentation and (ii) Fe(III)-reducing conditions. In the ISA-fermentation experiment, U(VI) was precipitated as insoluble U(VI)-phosphates, whereas under Fe(III)-reducing conditions, the majority of the uranium was precipitated as reduced U(IV)-phosphates, presumably formed via enzymatic reduction mediated by metal-reducing bacteria, including Geobacter species. Overall, this suggests the establishment of a microbially mediated "bio-barrier" extending into the far field geosphere surrounding a GDF is possible and this biobarrier has the potential to evolve in response to GDF evolution and can have a controlling impact on the fate of radionuclides.
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Affiliation(s)
- Gina Kuippers
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Katherine Morris
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Luke T Townsend
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Pieter Bots
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- Civil and Environmental Engineering, University of Strathclyde, Glasgow, G11XQ, U.K
| | - Kristina Kvashnina
- The Rossendorf Beamline at ESRF-The European Synchrotron, CS40220, 38043 Grenoble Cedex 9, France
- Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology, P.O. Box 510119, 01314 Dresden, Germany
| | - Nicholas D Bryan
- National Nuclear Laboratory Limited, Chadwick House, Warrington Road, Birchwood Park, Warrington, WA3 6AE, U.K
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal & Williamson Research Centre for Molecular Environmental Science, Department of Earth and Environmental Sciences, University of Manchester, Oxford Road, Manchester M13 9PL, U.K
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6
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Sediment Dynamics of the Neretva Channel (Croatia Coast) Inferred by Chemical and Physical Proxies. APPLIED SCIENCES-BASEL 2020. [DOI: 10.3390/app10030807] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We examined the transport of sediments and their surficial pathways from the mouth of Neretva River, through the Neretva Channel, toward the Adriatic Sea. This research was based on twelve box-cores and five grab samples collected within the Neretva Channel. Sediment dynamics were evaluated using several proxies, such as organic matter, radiochemical isotopes and select metal concentrations and physical parameters. The data analysis showed that the influence of the river on particle distribution along the Neretva Channel decreases northward, with an estimated sediment accumulation rate ranging from 1.9 to 8.5 mm/yr. The lowest accumulation rate was found in the sector not influenced by river inflow, whereas the preferential sediment accumulation area is in the center of the basin. We speculate that dispersion and accumulation of sediments are both driven by an eddy in the waters of the Neretva Channel triggered/or intensified seasonally by the interaction of karstic springs, river input and Adriatic Sea waters. Our results indicate that the anthropogenic factor does not affect the concentration of metals within the channel and that the river particles dynamics determine the Pb areal distribution, while Cr and Ni have a possible source located to the northwest of the river-mouth.
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Bower WR, Morris K, Livens FR, Mosselmans JFW, Fallon CM, Fuller AJ, Natrajan L, Boothman C, Lloyd JR, Utsunomiya S, Grolimund D, Ferreira Sanchez D, Jilbert T, Parker J, Neill TS, Law GTW. Metaschoepite Dissolution in Sediment Column Systems-Implications for Uranium Speciation and Transport. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:9915-9925. [PMID: 31317743 DOI: 10.1021/acs.est.9b02292] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Metaschoepite is commonly found in U-contaminated environments and metaschoepite-bearing wastes may be managed via shallow or deep disposal. Understanding metaschoepite dissolution and tracking the fate of any liberated U is thus important. Here, discrete horizons of metaschoepite (UO3·nH2O) particles were emplaced in flowing sediment/groundwater columns representative of the UK Sellafield Ltd. site. The column systems either remained oxic or became anoxic due to electron donor additions, and the columns were sacrificed after 6- and 12-months for analysis. Solution chemistry, extractions, and bulk and micro/nano-focus X-ray spectroscopies were used to track changes in U distribution and behavior. In the oxic columns, U migration was extensive, with UO22+ identified in effluents after 6-months of reaction using fluorescence spectroscopy. Unusually, in the electron-donor amended columns, during microbially mediated sulfate reduction, significant amounts of UO2-like colloids (>60% of the added U) were found in the effluents using TEM. XAS analysis of the U remaining associated with the reduced sediments confirmed the presence of trace U(VI), noncrystalline U(IV), and biogenic UO2, with UO2 becoming more dominant with time. This study highlights the potential for U(IV) colloid production from U(VI) solids under reducing conditions and the complexity of U biogeochemistry in dynamic systems.
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Affiliation(s)
- William R Bower
- Centre for Radiochemistry Research, School of Chemistry , The University of Manchester , Manchester , U.K. , M13 9PL
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences , The University of Manchester , Manchester , U.K. , M13 9PL
- Radiochemistry Unit, Department of Chemistry , The University of Helsinki , Helsinki , Finland , 00014
| | - Katherine Morris
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences , The University of Manchester , Manchester , U.K. , M13 9PL
| | - Francis R Livens
- Centre for Radiochemistry Research, School of Chemistry , The University of Manchester , Manchester , U.K. , M13 9PL
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences , The University of Manchester , Manchester , U.K. , M13 9PL
| | | | - Connaugh M Fallon
- Centre for Radiochemistry Research, School of Chemistry , The University of Manchester , Manchester , U.K. , M13 9PL
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences , The University of Manchester , Manchester , U.K. , M13 9PL
- Radiochemistry Unit, Department of Chemistry , The University of Helsinki , Helsinki , Finland , 00014
| | - Adam J Fuller
- Centre for Radiochemistry Research, School of Chemistry , The University of Manchester , Manchester , U.K. , M13 9PL
| | - Louise Natrajan
- Centre for Radiochemistry Research, School of Chemistry , The University of Manchester , Manchester , U.K. , M13 9PL
| | - Christopher Boothman
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences , The University of Manchester , Manchester , U.K. , M13 9PL
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences , The University of Manchester , Manchester , U.K. , M13 9PL
| | - Satoshi Utsunomiya
- Kyushu University , Department of Chemistry , 744 Motooka , Nishi-ku , Fukuoka Japan , 819-0395
| | - Daniel Grolimund
- Swiss Light Source , Paul Scherrer Institute , Villigen , Switzerland , 5232
| | | | - Tom Jilbert
- Ecosystems and Environmental Research Programme, Faculty of Biological and Environmental Sciences , The University of Helsinki , Helsinki , Finland , 00014
| | - Julia Parker
- Diamond Light Source , Harwell Science and Innovation Campus , Didcot , U.K. , OX11 0DE
| | - Thomas S Neill
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences , The University of Manchester , Manchester , U.K. , M13 9PL
| | - Gareth T W Law
- Centre for Radiochemistry Research, School of Chemistry , The University of Manchester , Manchester , U.K. , M13 9PL
- Radiochemistry Unit, Department of Chemistry , The University of Helsinki , Helsinki , Finland , 00014
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Thorpe CL, Williams HA, Boothman C, Lloyd JR, Morris K. Positron emission tomography to visualise in-situ microbial metabolism in natural sediments. Appl Radiat Isot 2019; 144:104-110. [DOI: 10.1016/j.apradiso.2018.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Accepted: 11/13/2018] [Indexed: 10/27/2022]
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9
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Boylan AA, Stewart DI, Graham JT, Burke IT. Behaviour of carbon-14 containing low molecular weight organic compounds in contaminated groundwater under aerobic conditions. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2018; 192:279-288. [PMID: 29990775 DOI: 10.1016/j.jenvrad.2018.06.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 06/22/2018] [Accepted: 06/22/2018] [Indexed: 06/08/2023]
Abstract
Short chain carbon-14 (14C) containing organic compounds can be formed by abiotic oxidation of carbides and impurities within nuclear fuel cladding. During fuel reprocessing and subsequent waste storage there is potential for these organic compounds to enter shallow subsurface environments due to accidental discharges. Currently there is little data on the persistence of these compounds in such environments. Four 14C-labelled compounds (acetate; formate; formaldehyde and methanol) were added to aerobic microcosm experiments that contained glacial outwash sediments and groundwater simulant representative of the Sellafield nuclear reprocessing site, UK. Two concentrations of each electron donor were used, low concentration (10-5 M) to replicate predicted concentrations from an accidental release and high concentration (10-2 M) to study the impact of the individual electron donor on the indigenous microbial community in the sediment. In the low concentration system only ∼5% of initial 14C remained in solution at the end of experiments in contact with atmosphere (250-350 h). The production of 14CO2(g) (measured after 48 h) suggests microbially mediated breakdown is the primary removal mechanism for these organic compounds, although methanol loss may have been partially by volatilisation. Highest retention of 14C by the solid fractions was found in the acetate experiment, with 12% being associated with the inorganic fraction, suggesting modest precipitation as solid carbonate. In the high concentration systems only ∼5% of initial 14C remains in solution at the end of the experiments for acetate, formate and methanol. In the formaldehyde experiment only limited loss from solution was observed (76% remained in solution). The microbial populations of unaltered sediment and those in the low concentration experiments were broadly similar, with highly diverse bacterial phyla present. Under high concentrations of the organic compounds the abundance of common operational taxonomic units was reduced by 66% and the community structure was dominated by Proteobacteria (particularly Betaproteobacteria) signifying a shift in community structure in response to the electron donor available. The results of this study suggest that many bacterial phyla that are ubiquitous in near surface soils are able to utilise a range of 14C-containing low molecular weight organic substances very rapidly, and thus such substances are unlikely to persist in aerobic shallow subsurface environments.
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Affiliation(s)
- Aislinn A Boylan
- School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
| | - Douglas I Stewart
- School of Civil Engineering, University of Leeds, Leeds, LS2 9JT, UK
| | - James T Graham
- National Nuclear Laboratory, Sellafield, Cumbria, CA20 1PG, UK
| | - Ian T Burke
- School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK.
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Masters-Waage NK, Morris K, Lloyd JR, Shaw S, Mosselmans JFW, Boothman C, Bots P, Rizoulis A, Livens FR, Law GTW. Impacts of Repeated Redox Cycling on Technetium Mobility in the Environment. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:14301-14310. [PMID: 29144125 DOI: 10.1021/acs.est.7b02426] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Technetium is a problematic contaminant at nuclear sites and little is known about how repeated microbiologically mediated redox cycling impacts its fate in the environment. We explore this question in sediments representative of the Sellafield Ltd. site, UK, over multiple reduction and oxidation cycles spanning ∼1.5 years. We found the amount of Tc remobilised from the sediment into solution significantly decreased after repeated redox cycles. X-ray Absorption Spectroscopy (XAS) confirmed that sediment bound Tc was present as hydrous TcO2-like chains throughout experimentation and that Tc's increased resistance to remobilization (via reoxidation to soluble TcO4-) resulted from both shortening of TcO2 chains during redox cycling and association of Tc(IV) with Fe phases in the sediment. We also observed that Tc(IV) remaining in solution during bioreduction was likely associated with colloidal magnetite nanoparticles. These findings highlight crucial links between Tc and Fe biogeochemical cycles that have significant implications for Tc's long-term environmental mobility, especially under ephemeral redox conditions.
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Affiliation(s)
- Nicholas K Masters-Waage
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , M13 9PL, Manchester, United Kingdom
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Katherine Morris
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Samuel Shaw
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - J Frederick W Mosselmans
- Diamond Light Source Ltd ., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
| | - Christopher Boothman
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Pieter Bots
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Athanasios Rizoulis
- Research Centre for Radwaste Disposal and Williamson Research Centre, School of Earth and Environmental Sciences, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Francis R Livens
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , M13 9PL, Manchester, United Kingdom
| | - Gareth T W Law
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , M13 9PL, Manchester, United Kingdom
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11
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Thorpe CL, Law GTW, Lloyd JR, Williams HA, Atherton N, Morris K. Quantifying Technetium and Strontium Bioremediation Potential in Flowing Sediment Columns. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:12104-12113. [PMID: 28968094 DOI: 10.1021/acs.est.7b02652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The high-yield fission products 99Tc and 90Sr are found as problematic radioactive contaminants in groundwater at nuclear sites. Treatment options for radioactively contaminated land include bioreduction approaches, and this paper explores 99mTc and 90Sr behavior and stability under a range of biogeochemical conditions stimulated by electron donor addition methods. Dynamic column experiments with sediment from the Sellafield nuclear facility, completed at site relevant flow conditions, demonstrated that Fe(III)-reducing conditions had developed by 60 days. Sediment reactivity toward 99Tc was then probed using a 99mTc(VII) tracer at <10-10 mol L-1 and γ camera imaging showed full retention of 99mTc in acetate amended systems. Sediment columns were then exposed to selected treatments to examine the effects of different acetate amendment regimes and reoxidation scenarios over 55 days when they were again imaged with 99mTc. Here, partially oxidized sediments with no further electron donor additions remained reactive toward 99mTc under relevant groundwater O2 and NO3- concentrations over 55 days. Immobilization of 99mTc was highest where continuous acetate amendment had resulted in sulfate-reducing conditions. Interestingly, the sulfate reducing system showed enhanced Sr retention when stable Sr2+ was added continuously as a proxy for 90Sr. Overall, sediment reactivity was nondestructively imaged over an extended period to provide new information about dynamic iron and radionuclide biogeochemistry throughout realistic sediment redox cycling regimes.
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Affiliation(s)
- Clare L Thorpe
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester , Manchester M13 9PL, United Kingdom
| | - Gareth T W Law
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester , Manchester M13 9PL, United Kingdom
- Centre for Radiochemistry Research, School of Chemistry, The University of Manchester , Manchester M13 9PL, United Kingdom
| | - Jonathan R Lloyd
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester , Manchester M13 9PL, United Kingdom
| | - Heather A Williams
- Nuclear Medicine Centre, Manchester Royal Infirmary , Manchester M13 9WL, United Kingdom
| | - Nick Atherton
- Sellafield Ltd. , Land Quality, Sellafield, Seascale, Cumbria CA20 1PG, United Kingdom
| | - Katherine Morris
- Research Centre for Radwaste Disposal and Williamson Research Centre for Molecular Environmental Science, School of Earth and Environmental Sciences, The University of Manchester , Manchester M13 9PL, United Kingdom
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12
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Newsome L, Cleary A, Morris K, Lloyd JR. Long-Term Immobilization of Technetium via Bioremediation with Slow-Release Substrates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:1595-1604. [PMID: 28051295 DOI: 10.1021/acs.est.6b04876] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Radionuclides are present in groundwater at contaminated nuclear facilities with technetium-99, one of the most mobile radionuclides encountered. In situ bioremediation via the generation of microbially reducing conditions has the potential to remove aqueous and mobile Tc(VII) from groundwater as insoluble Tc(IV). However, questions remain regarding the optimal methods of biostimulation and the stability of reduced Tc(IV) phases under oxic conditions. Here, we selected a range of slow-release electron donor/chemical reduction based substrates available for contaminated land treatment, and assessed their potential to stimulate the formation of recalcitrant Tc(IV) biominerals under conditions relevant to radioactively contaminated land. These included a slow-release polylactate substrate (HRC), a similar substrate with an additional organosulfur ester (MRC) and a substrate containing zerovalent iron and plant matter (EHC). Results showed that Tc was removed from solution in the form of poorly soluble hydrous Tc(IV)-oxides or Tc(IV)-sulfides during the development of reducing conditions. Reoxidation experiments showed that these phases were largely resistant to oxidative remobilization and were more resistant than Tc(IV) produced via biostimulation with an acetate/lactate electron donor mix in the sediments tested. The implications of the targeted formation of recalcitrant Tc(IV) phases using these proprietorial substrates in situ is discussed in the context of the long-term management of technetium at legacy nuclear sites.
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Affiliation(s)
- Laura Newsome
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Adrian Cleary
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Katherine Morris
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Jonathan R Lloyd
- Williamson Research Centre and Research Centre for Radwaste Disposal, School of Earth, Atmospheric and Environmental Sciences, University of Manchester , Williamson Building, Oxford Road, Manchester M13 9PL, United Kingdom
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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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Hu N, Ding DX, Li SM, Tan X, Li GY, Wang YD, Xu F. Bioreduction of U(VI) and stability of immobilized uranium under suboxic conditions. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2016; 154:60-67. [PMID: 26854555 DOI: 10.1016/j.jenvrad.2016.01.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 01/28/2016] [Accepted: 01/28/2016] [Indexed: 06/05/2023]
Abstract
In order to study the bioreduction of U(VI) and stability of immobilized uranium under suboxic conditions, microcosm were amended with ethanol, lactate and glucose, and incubated under suboxic conditions. During the incubation, total dissolved U in amended microcosms decreased from 0.95 mg/L to 0.03 mg/L. Pyrosequencing results showed that, the proportion of anaerobic microorganisms capable of reducing U(VI) under suboxic conditions was small compared with that under anoxic conditions; the proportion of aerobic and facultative anaerobic microorganisms capable of consuming the dissolved oxygen was large; and some of the facultative anaerobic microorganisms could reduce U(VI). These results indicated that different microbial communities were responsible for the bioreduction of U(VI) under suboxic and anoxic conditions. After the electron donors were exhausted, total dissolved U in the amended microcosms remained unchanged, while the U(VI)/U(IV) ratio in the solid phase of sediments increased obviously. This implied that the performance of bioreduction of the U(VI) can be maintained under suboxic condition.
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Affiliation(s)
- Nan Hu
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, PR China
| | - De-xin Ding
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, PR China.
| | - Shi-mi Li
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, PR China
| | - Xiang Tan
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, PR China
| | - Guang-yue Li
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, PR China
| | - Yong-dong Wang
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, PR China
| | - Fei Xu
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, PR China
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Fuller AJ, Shaw S, Peacock CL, Trivedi D, Burke IT. EXAFS Study of Sr sorption to Illite, Goethite, Chlorite, and Mixed Sediment under Hyperalkaline Conditions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:2937-2946. [PMID: 26938867 DOI: 10.1021/acs.langmuir.5b04633] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Strontium is an important contaminant radionuclide at many former nuclear sites. This paper investigates the effect of changing pH and ionic strength on the sorption of Sr to a range of common soil minerals. Specifically it focuses on the sorption of Sr onto illite, chlorite, goethite, and a mixed sediment. The interplay between ionic strength and pH was determined by varying the background ionic strength of the system using both NaCl (for a constant pH) and NaOH (to also vary pH). Under conditions of moderate pH, Sr sorption decreased with increasing ionic strength, due to competition between the Na and Sr atoms for the outer-sphere complexes. However, where increasing ionic strength was accompanied by increasing pH, Sr sorption remained high. This suggested that Sr was sorbed to the minerals without competition from background Na ions. Extended X-ray absorption fine structure (EXAFS) spectra confirmed that at highly alkaline pH (>12.5) Sr was forming inner-sphere complexes on the surfaces of all minerals. This specific adsorption of the Sr (as SrOH(+)) explains why it was still adsorbed to the minerals under very high ionic strength conditions and was not out-competed by Na.
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Affiliation(s)
- Adam J Fuller
- School of Earth and Environment, University of Leeds , Leeds LS2 9JT, United Kingdom
| | - Samuel Shaw
- School of Earth, Atmospheric and Environmental Science, University of Manchester , Manchester M13 9PL, United Kingdom
| | - Caroline L Peacock
- School of Earth and Environment, University of Leeds , Leeds LS2 9JT, United Kingdom
| | - Divyesh Trivedi
- National Nuclear Laboratory Ltd , Chadwick House, Warrington Road, Birchwood Park, Warrington WA3 6AE, United Kingdom
| | - Ian T Burke
- School of Earth and Environment, University of Leeds , Leeds LS2 9JT, United Kingdom
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Lee JH, Fredrickson JK, Plymale AE, Dohnalkova AC, Resch CT, McKinley JP, Shi L. An autotrophic H2 -oxidizing, nitrate-respiring, Tc(VII)-reducing Acidovorax sp. isolated from a subsurface oxic-anoxic transition zone. ENVIRONMENTAL MICROBIOLOGY REPORTS 2015; 7:395-403. [PMID: 25558059 DOI: 10.1111/1758-2229.12263] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 12/19/2014] [Indexed: 06/04/2023]
Abstract
Increasing concentrations of H2 with depth were observed across a geologic unconformity and associated redox transition zone in the subsurface at the Hanford Site in south-central Washington, USA. An opposing gradient characterized by decreasing O2 and nitrate concentrations was consistent with microbial-catalysed biogeochemical processes. Sterile sand was incubated in situ within a multilevel sampler placed across the redox transition zone to evaluate the potential for Tc(VII) reduction and for enrichment of H2 -oxidizing denitrifiers capable of reducing Tc(VII). H2 -driven TcO4 (-) reduction was detected in sand incubated at all depths but was strongest in material from a depth of 17.1 m. Acidovorax spp. were isolated from H2 -nitrate enrichments from colonized sand from 15.1 m, with one representative, strain JHL-9, subsequently characterized. JHL-9 grew on acetate with either O2 or nitrate as electron acceptor (data not shown) and on medium with bicarbonate, H2 and nitrate. JHL-9 also reduced pertechnetate (TcO4 (-) ) under denitrifying conditions with H2 as the electron donor. H2 -oxidizing Acidovorax spp. in the subsurface at Hanford and other locations may contribute to the maintenance of subsurface redox gradients and offer the potential for Tc(VII) reduction.
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Affiliation(s)
- Ji-Hoon Lee
- Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | | | | | | | - Charles T Resch
- Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | | | - Liang Shi
- Pacific Northwest National Laboratory, Richland, WA, 99352, USA
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17
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The impact of gamma radiation on sediment microbial processes. Appl Environ Microbiol 2015; 81:4014-25. [PMID: 25841009 DOI: 10.1128/aem.00590-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 03/29/2015] [Indexed: 11/20/2022] Open
Abstract
Microbial communities have the potential to control the biogeochemical fate of some radionuclides in contaminated land scenarios or in the vicinity of a geological repository for radioactive waste. However, there have been few studies of ionizing radiation effects on microbial communities in sediment systems. Here, acetate and lactate amended sediment microcosms irradiated with gamma radiation at 0.5 or 30 Gy h(-1) for 8 weeks all displayed NO3 (-) and Fe(III) reduction, although the rate of Fe(III) reduction was decreased in 30-Gy h(-1) treatments. These systems were dominated by fermentation processes. Pyrosequencing indicated that the 30-Gy h(-1) treatment resulted in a community dominated by two Clostridial species. In systems containing no added electron donor, irradiation at either dose rate did not restrict NO3 (-), Fe(III), or SO4 (2-) reduction. Rather, Fe(III) reduction was stimulated in the 0.5-Gy h(-1)-treated systems. In irradiated systems, there was a relative increase in the proportion of bacteria capable of Fe(III) reduction, with Geothrix fermentans and Geobacter sp. identified in the 0.5-Gy h(-1) and 30-Gy h(-1) treatments, respectively. These results indicate that biogeochemical processes will likely not be restricted by dose rates in such environments, and electron accepting processes may even be stimulated by radiation.
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Burke IT, Mosselmans JFW, Shaw S, Peacock CL, Benning LG, Coker VS. Impact of the Diamond Light Source on research in Earth and environmental sciences: current work and future perspectives. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:20130151. [PMID: 25624516 PMCID: PMC4308981 DOI: 10.1098/rsta.2013.0151] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Diamond Light Source Ltd celebrated its 10th anniversary as a company in December 2012 and has now accepted user experiments for over 5 years. This paper describes the current facilities available at Diamond and future developments that enhance its capacities with respect to the Earth and environmental sciences. A review of relevant research conducted at Diamond thus far is provided. This highlights how synchrotron-based studies have brought about important advances in our understanding of the fundamental parameters controlling highly complex mineral-fluid-microbe interface reactions in the natural environment. This new knowledge not only enhances our understanding of global biogeochemical processes, but also provides the opportunity for interventions to be designed for environmental remediation and beneficial use.
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Affiliation(s)
- Ian T Burke
- Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
| | - J Frederick W Mosselmans
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, UK
| | - Samuel Shaw
- School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK
| | - Caroline L Peacock
- Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
| | - Liane G Benning
- Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
| | - Victoria S Coker
- School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 9PL, UK
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Lehoux AP, Lockwood CL, Mayes WM, Stewart DI, Mortimer RJG, Gruiz K, Burke IT. Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility. ENVIRONMENTAL GEOCHEMISTRY AND HEALTH 2013; 35:643-56. [PMID: 23793510 DOI: 10.1007/s10653-013-9547-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 02/18/2013] [Indexed: 05/23/2023]
Abstract
Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e.g. Al, As, Mo and V). Release of up to 1 million m(3) of bauxite residue (red mud) suspension from the Ajka repository, western Hungary, caused large-scale contamination of downstream rivers and floodplains. There is now concern about the potential leaching of toxic metal(loid)s from the red mud as some have enhanced solubility at high pH. This study investigated the impact of red mud addition to three different Hungarian soils with respect to trace element solubility and soil geochemistry. The effectiveness of gypsum amendment for the rehabilitation of red mud-contaminated soils was also examined. Red mud addition to soils caused a pH increase, proportional to red mud addition, of up to 4 pH units (e.g. pH 7 → 11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33 % w/w); experiments using this soil also had much lower aqueous Al, As and V concentrations. Gypsum addition to soil/red mud mixtures, even at relatively low concentrations (1 % w/w), was sufficient to buffer experimental pH to 7.5-8.5. This effect was attributed to the reaction of Ca(2+) supplied by the gypsum with OH(-) and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities, and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum addition could therefore provide a cheaper alternative to recovery (dig and dump) for the treatment of red mud-affected soils. The observed inhibition of trace metal release within red mud-affected soils was relatively insensitive to either the percentage of red mud or gypsum present, making the treatment easy to apply. However, there is risk that over-application of gypsum could lead to detrimental long-term increases in soil salinity.
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Affiliation(s)
- Alizée P Lehoux
- Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds, UK
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Wallace SH, Shaw S, Morris K, Small JS, Burke IT. Alteration of sediments by hyperalkaline K-rich cement leachate: implications for strontium adsorption and incorporation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:3694-3700. [PMID: 23510060 DOI: 10.1021/es3051982] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Results are presented from 1 year batch experiments where K-rich hyperalkaline pH 13.5 young cement water (YCW) was reacted with sediments to investigate the effect of high pH, mineral alteration, and secondary mineral precipitation on (90)Sr sorption. After reaction with YCW, Sr sorption was found to be greater than 75% in all samples up to 365 days and 98% in a sample reacted for 365 days at 70 °C. Scanning electron microscopy analysis of sediment samples reacted at room temperature showed surface alteration and precipitation of a secondary phase, likely a K-rich aluminosilicate gel. The presence of Sr-Si(Al) bond distances in Sr K-edge extended X-ray absorption fine structure (EXAFS) analysis suggested that the Sr was present as an inner-sphere adsorption complex. However, sequential extractions found the majority of this Sr was still exchangeable with Mg(2+) at pH 7. For the sample reacted for 1 year at 70 °C, EXAFS analysis revealed clear evidence for ∼6 Sr-Si(Al) backscatters at 3.45 Å, consistent with Sr incorporation into the neoformed K-chabazite phase that was detected by X-ray diffraction and electron microscopy. Once incorporated into chabazite, (90)Sr was not exchangeable with Mg(2+), and chemical leaching with pH 1.5 HNO3 was required to remobilize 60% of the (90)Sr. These results indicate that, in high pH cementitious leachate, there is significantly enhanced Sr retention in sediments due to changes in the adsorption mechanism and incorporation into secondary silicate minerals. This suggests that Sr retention may be enhanced in this high pH zone and that the incorporation process may lead to irreversible exchange of the contaminant over extended time periods.
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Affiliation(s)
- Sarah H Wallace
- Earth Surface Science Institute, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, United Kingdom
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Thorpe CL, Morris K, Boothman C, Lloyd JR. Alkaline Fe(III) reduction by a novel alkali-tolerant Serratia sp. isolated from surface sediments close to Sellafield nuclear facility, UK. FEMS Microbiol Lett 2011; 327:87-92. [PMID: 22092936 DOI: 10.1111/j.1574-6968.2011.02455.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Accepted: 11/10/2011] [Indexed: 11/28/2022] Open
Abstract
Extensive denitrification resulted in a dramatic increase in pH (from 6.8 to 9.5) in nitrate-impacted, acetate-amended sediment microcosms containing sediment representative of the Sellafield nuclear facility, UK. Denitrification was followed by Fe(III) reduction, indicating the presence of alkali-tolerant, metal-reducing bacteria. A close relative (99% 16S rRNA gene sequence homology) to Serratia liquefaciens dominated progressive enrichment cultures containing Fe(III)-citrate as the sole electron acceptor at pH 9 and was isolated aerobically using solid media. The optimum growth conditions for this facultatively anaerobic Serratia species were investigated, and it was capable of metabolizing a wide range of electron acceptors including oxygen, nitrate, FeGel, Fe-NTA and Fe-citrate and electron donors including acetate, lactate, formate, ethanol, glucose, glycerol and yeast extract at an optimum pH of c. 6.5 at 20 °C. The alkali tolerance of this strain extends the pH range of highly adaptable Fe(III)-reducing Serratia species from mildly acidic pH values associated with acid mine drainage conditions to alkali conditions representative of subsurface sediments stimulated for extensive denitrification and metal reduction.
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Affiliation(s)
- Clare L Thorpe
- Research Centre for Radwaste and Decommissioning and Williamson Research Centre for Molecular Environmental Science, School of Earth, Atmospheric and Environmental Sciences, The University of Manchester, Manchester, UK
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Hubbard CG, West LJ, Morris K, Kulessa B, Brookshaw D, Lloyd JR, Shaw S. In search of experimental evidence for the biogeobattery. ACTA ACUST UNITED AC 2011. [DOI: 10.1029/2011jg001713] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Law GTW, Geissler A, Lloyd JR, Livens FR, Boothman C, Begg JDC, Denecke MA, Rothe J, Dardenne K, Burke IT, Charnock JM, Morris K. Geomicrobiological redox cycling of the transuranic element neptunium. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2010; 44:8924-8929. [PMID: 21047117 DOI: 10.1021/es101911v] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Microbial processes can affect the environmental behavior of redox sensitive radionuclides, and understanding these reactions is essential for the safe management of radioactive wastes. Neptunium, an alpha-emitting transuranic element, is of particular importance because of its long half-life, high radiotoxicity, and relatively high solubility as Np(V)O(2)(+) under oxic conditions. Here, we describe experiments to explore the biogeochemistry of Np where Np(V) was added to oxic sediment microcosms with indigenous microorganisms and anaerobically incubated. Enhanced Np removal to sediments occurred during microbially mediated metal reduction, and X-ray absorption spectroscopy showed this was due to reduction to poorly soluble Np(IV) on solids. In subsequent reoxidation experiments, sediment-associated Np(IV) was somewhat resistant to oxidative remobilization. These results demonstrate the influence of microbial processes on Np solubility and highlight the critical importance of radionuclide biogeochemistry in nuclear legacy management.
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Affiliation(s)
- Gareth T W Law
- Research Centre for Radwaste and Decommissioning, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
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