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Title: In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen

Abstract

Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 {micro}M uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agency maximum contaminant limit (MCL) for drinking water (<30 {micro}g L{sup -1} or 0.126 {micro}M). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L{sup -1}) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from <0.13 to 2.0 {micro}M at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLSmore » well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. At the completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 {micro}M. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp.« less

Authors:
 [1];  [1];  [2];  [2];  [3];  [3];  [4];  [5];  [1];  [6];  [6];  [1];  [1];  [1];  [1];  [1];  [4];  [1];  [1];  [5] more »;  [3];  [3];  [6];  [2];  [2];  [1];  [1] « less
  1. ORNL
  2. Stanford University
  3. Michigan State University, East Lansing
  4. Miami University, Oxford, OH
  5. Argonne National Laboratory (ANL)
  6. University of Oklahoma, Norman
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
945330
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science & Technology; Journal Volume: 41; Journal Issue: 16
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; URANIUM; IN-SITU PROCESSING; BIODEGRADATION; REDUCTION; GROUND WATER; OAK RIDGE RESERVATION; BACTERIA; ETHANOL

Citation Formats

Wu, Weimin, Carley, Jack M, Luo, Jian, Ginder-Vogel, Matthew A., Cardenas, Erick, Leigh, Mary Beth, Hwang, Chaichi, Kelly, Shelly D, Ruan, Chuanmin, Wu, Liyou, Van Nostrand, Joy, Gentry, Terry J, Lowe, Kenneth Alan, Mehlhorn, Tonia L, Carroll, Sue L, Luo, Wensui, Fields, Matthew Wayne, Gu, Baohua, Watson, David B, Kemner, Kenneth M, Marsh, Terence, Tiedje, James, Zhou, Jizhong, Fendorf, Scott, Kitanidis, Peter K., Jardine, Philip M, and Criddle, Craig. In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen. United States: N. p., 2007. Web. doi:10.1021/es062657b.
Wu, Weimin, Carley, Jack M, Luo, Jian, Ginder-Vogel, Matthew A., Cardenas, Erick, Leigh, Mary Beth, Hwang, Chaichi, Kelly, Shelly D, Ruan, Chuanmin, Wu, Liyou, Van Nostrand, Joy, Gentry, Terry J, Lowe, Kenneth Alan, Mehlhorn, Tonia L, Carroll, Sue L, Luo, Wensui, Fields, Matthew Wayne, Gu, Baohua, Watson, David B, Kemner, Kenneth M, Marsh, Terence, Tiedje, James, Zhou, Jizhong, Fendorf, Scott, Kitanidis, Peter K., Jardine, Philip M, & Criddle, Craig. In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen. United States. doi:10.1021/es062657b.
Wu, Weimin, Carley, Jack M, Luo, Jian, Ginder-Vogel, Matthew A., Cardenas, Erick, Leigh, Mary Beth, Hwang, Chaichi, Kelly, Shelly D, Ruan, Chuanmin, Wu, Liyou, Van Nostrand, Joy, Gentry, Terry J, Lowe, Kenneth Alan, Mehlhorn, Tonia L, Carroll, Sue L, Luo, Wensui, Fields, Matthew Wayne, Gu, Baohua, Watson, David B, Kemner, Kenneth M, Marsh, Terence, Tiedje, James, Zhou, Jizhong, Fendorf, Scott, Kitanidis, Peter K., Jardine, Philip M, and Criddle, Craig. Mon . "In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen". United States. doi:10.1021/es062657b.
@article{osti_945330,
title = {In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen},
author = {Wu, Weimin and Carley, Jack M and Luo, Jian and Ginder-Vogel, Matthew A. and Cardenas, Erick and Leigh, Mary Beth and Hwang, Chaichi and Kelly, Shelly D and Ruan, Chuanmin and Wu, Liyou and Van Nostrand, Joy and Gentry, Terry J and Lowe, Kenneth Alan and Mehlhorn, Tonia L and Carroll, Sue L and Luo, Wensui and Fields, Matthew Wayne and Gu, Baohua and Watson, David B and Kemner, Kenneth M and Marsh, Terence and Tiedje, James and Zhou, Jizhong and Fendorf, Scott and Kitanidis, Peter K. and Jardine, Philip M and Criddle, Craig},
abstractNote = {Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 {micro}M uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agency maximum contaminant limit (MCL) for drinking water (<30 {micro}g L{sup -1} or 0.126 {micro}M). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L{sup -1}) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from <0.13 to 2.0 {micro}M at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. At the completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 {micro}M. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp.},
doi = {10.1021/es062657b},
journal = {Environmental Science & Technology},
number = 16,
volume = 41,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Microbially mediated in situ reduction of soluble U(VI) to insoluble U(IV) (as UO2) has been proposed as a means of preventing the migration of that radionuclide with groundwater, but preventing the oxidative resolubilization of U has proven difficult. We hypothesized that relatively slow rates of U(VI) bioreduction would yield larger UO2 precipitates that would be more resistant to oxidation than those produced by rapid U(VI) bioreduction. We manipulated U(VI) bioreduction rates by varying the density of Shewanella putrefaciens CN32 added to U(VI) containing solutions with lactate as an electron donor. Characterization of biogenic UO2 particles by extended X-ray absorption fine-structuremore » spectroscopy and transmission electron microscopy revealed that UO2 nanoparticles formed by relatively slow rates of U(VI) reduction were larger and more highly aggregated than those formed by relatively rapid U(VI) reduction. UO2 particles formed at various rates were incubated under a variety of abiotically and biologically oxidizing conditions. In all cases, UO2 that was formed by relatively slow U(VI) reduction was oxidized at a slower rate and to a lesser extent than UO2 formed by relatively rapid U(VI) bioreduction, suggesting that the stability of UO2 in situ may be enhanced by stimulation of relatively slow rates of U(VI) reduction.« less
  • The influence of sediment bioreduction and reoxidation on U(VI) sorption was studied using Fe(III) oxide-containing saprolite from the U.S. Department of Energy (DOE) Oak Ridge site. Bioreduced sediments were generated by anoxic incubation with a metal reducing bacterium, Shewanella putrefaciens strain CN32, supplied with an electron donor. The reduced sediments were subsequently reoxidized by air contact. U(VI) sorption was studied in Na-NO3-HCO3 electrolytes that were both closed and open to atmosphere, and where pH, U(VI) and carbonate concentration was varied. Moessbauer spectroscopy and chemical analyses showed that 50% of the Fe(III)-oxides were reduced to Fe(II) that was sorbed to themore » sediment during incubation with CN32. However, this reduction and subsequent reoxidation of the sorbed Fe(II) had negligible influence on the rate and extent of U sorption, or the extractability of sorbed U by 0.2 mol/L NaHCO3. Various results indicated that U(VI) surface complexation was the primary process responsible for uranyl sorption by the bioreduced and reoxidized sediments. A two-site, non-electrostatic surface complexation model best described U(VI) adsorption under variable pH, carbonate and U(VI) conditions. A ferrihydrite-based diffuse double layer model provided a better estimation of U(VI) adsorption without parameter adjustment than did a goethite-based model, even though a majority of the Fe(III)-oxides in the sediments were goethite.« less
  • Microbial enumeration, 16S rRNA gene clone libraries, and chemical analysis were used to evaluate the in situ biological reduction and immobilization of uranium(VI) in a long-term experiment (more than 2 years) conducted at a highly uranium-contaminated site (up to 60 mg/liter and 800 mg/kg solids) of the U.S. Department of Energy in Oak Ridge, TN. Bioreduction was achieved by conditioning groundwater above ground and then stimulating growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria in situ through weekly injection of ethanol into the subsurface. After nearly 2 years of intermittent injection of ethanol, aqueous U levels fell below the U.S. Environmentalmore » Protection Agency maximum contaminant level for drinking water and groundwater (<30 {micro}g/liter or 0.126 {micro}M). Sediment microbial communities from the treatment zone were compared with those from a control well without biostimulation. Most-probable-number estimations indicated that microorganisms implicated in bioremediation accumulated in the sediments of the treatment zone but were either absent or in very low numbers in an untreated control area. Organisms belonging to genera known to include U(VI) reducers were detected, including Desulfovibrio, Geobacter, Anaeromyxobacter, Desulfosporosinus, and Acidovorax spp. The predominant sulfate-reducing bacterial species were Desulfovibrio spp., while the iron reducers were represented by Ferribacterium spp. and Geothrix spp. Diversity-based clustering revealed differences between treated and untreated zones and also within samples of the treated area. Spatial differences in community structure within the treatment zone were likely related to the hydraulic pathway and to electron donor metabolism during biostimulation.« less