Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface

Wei Min Wu; Jack Carley; Stefan J. Green; Jian Luo; Shelly D. Kelly; Joy Van Nostrand; Kenneth Lowe; Tonia Mehlhorn; Sue Carroll; Benjaporn Boonchayanant; Frank E. Löfller; David Watson; Kenneth M. Kemner; Jizhong Zhou; Peter K. Kitanidis; Joel E. Kostka; Philip M. Jardine; Craig S. Criddle

doi:10.1021/es1000837

Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface

Wei Min Wu, Jack Carley, Stefan J. Green, Jian Luo, Shelly D. Kelly, Joy Van Nostrand, Kenneth Lowe, Tonia Mehlhorn, Sue Carroll, Benjaporn Boonchayanant, Frank E. Löfller, David Watson, Kenneth M. Kemner, Jizhong Zhou, Peter K. Kitanidis, Joel E. Kostka, Philip M. Jardine, Craig S. Criddle

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Abstract

The effects of nitrate on the stability of reduced, immobilized uranium were evaluated in field experiments at a U.S. Department of Energy site in Oak Ridge, TN. Nitrate (2.0 mM) was injected into a reduced region of the subsurface containing high levels of previously immobilized U(IV). The nitrate was reduced to nitrite, ammonium, and nitrogen gas; sulfide levels decreased; and Fe(II) levels increased then deceased. Uranium remobilization occurred concomitant with nitrite formation, suggesting nitrate-dependent, iron-accelerated oxidation of U(IV). Bromide tracer results indicated changes in subsurface flowpaths likely due to gas formation and/or precipitate. Desorption-adsorption of uranium by the iron-rich sediment impacted uranium mobilization and sequestration. After rereduction of the subsurface through ethanol additions, background groundwater containing high levels of nitrate was allowed to enter the reduced test zone. Aqueous uranium concentrations increased then decreased. Clone library analyses of sediment samples revealed the presence of denitrifying bacteria that can oxidize elemental sulfur, H₂S, Fe(II), and U(IV) (e.g., Thiobacillus spp.), and a decrease in relative abundance of bacteria that can reduce Fe(III) and sulfate. XANES analyses of sediment samples confirmed changes in uranium oxidation state. Addition of ethanol restored reduced conditions and triggered a short-term increase in Fe(II) and aqueous uranium, likely due to reductive dissolution of Fe(III) oxides and release of sorbed U(VI). After two months of intermittent ethanol addition, sulfide levels increased, and aqueous uranium concentrations gradually decreased to <0.1 μM.

Original language	English
Pages (from-to)	5104-5111
Number of pages	8
Journal	Environmental Science and Technology
Volume	44
Issue number	13
DOIs	https://doi.org/10.1021/es1000837
State	Published - Jul 1 2010

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Wu, W. M., Carley, J., Green, S. J., Luo, J., Kelly, S. D., Van Nostrand, J., Lowe, K., Mehlhorn, T., Carroll, S., Boonchayanant, B., Löfller, F. E., Watson, D., Kemner, K. M., Zhou, J., Kitanidis, P. K., Kostka, J. E., Jardine, P. M., & Criddle, C. S. (2010). Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface. Environmental Science and Technology, 44(13), 5104-5111. https://doi.org/10.1021/es1000837

@article{e76b1da03c8747779472899603e49af9,

title = "Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface",

abstract = "The effects of nitrate on the stability of reduced, immobilized uranium were evaluated in field experiments at a U.S. Department of Energy site in Oak Ridge, TN. Nitrate (2.0 mM) was injected into a reduced region of the subsurface containing high levels of previously immobilized U(IV). The nitrate was reduced to nitrite, ammonium, and nitrogen gas; sulfide levels decreased; and Fe(II) levels increased then deceased. Uranium remobilization occurred concomitant with nitrite formation, suggesting nitrate-dependent, iron-accelerated oxidation of U(IV). Bromide tracer results indicated changes in subsurface flowpaths likely due to gas formation and/or precipitate. Desorption-adsorption of uranium by the iron-rich sediment impacted uranium mobilization and sequestration. After rereduction of the subsurface through ethanol additions, background groundwater containing high levels of nitrate was allowed to enter the reduced test zone. Aqueous uranium concentrations increased then decreased. Clone library analyses of sediment samples revealed the presence of denitrifying bacteria that can oxidize elemental sulfur, H2S, Fe(II), and U(IV) (e.g., Thiobacillus spp.), and a decrease in relative abundance of bacteria that can reduce Fe(III) and sulfate. XANES analyses of sediment samples confirmed changes in uranium oxidation state. Addition of ethanol restored reduced conditions and triggered a short-term increase in Fe(II) and aqueous uranium, likely due to reductive dissolution of Fe(III) oxides and release of sorbed U(VI). After two months of intermittent ethanol addition, sulfide levels increased, and aqueous uranium concentrations gradually decreased to <0.1 μM.",

author = "Wu, {Wei Min} and Jack Carley and Green, {Stefan J.} and Jian Luo and Kelly, {Shelly D.} and {Van Nostrand}, Joy and Kenneth Lowe and Tonia Mehlhorn and Sue Carroll and Benjaporn Boonchayanant and L{\"o}fller, {Frank E.} and David Watson and Kemner, {Kenneth M.} and Jizhong Zhou and Kitanidis, {Peter K.} and Kostka, {Joel E.} and Jardine, {Philip M.} and Criddle, {Craig S.}",

year = "2010",

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doi = "10.1021/es1000837",

language = "English",

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Wu, WM, Carley, J, Green, SJ, Luo, J, Kelly, SD, Van Nostrand, J, Lowe, K, Mehlhorn, T, Carroll, S, Boonchayanant, B, Löfller, FE, Watson, D, Kemner, KM, Zhou, J, Kitanidis, PK, Kostka, JE, Jardine, PM & Criddle, CS 2010, 'Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface', Environmental Science and Technology, vol. 44, no. 13, pp. 5104-5111. https://doi.org/10.1021/es1000837

TY - JOUR

T1 - Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface

AU - Wu, Wei Min

AU - Carley, Jack

AU - Green, Stefan J.

AU - Luo, Jian

AU - Kelly, Shelly D.

AU - Van Nostrand, Joy

AU - Lowe, Kenneth

AU - Mehlhorn, Tonia

AU - Carroll, Sue

AU - Boonchayanant, Benjaporn

AU - Löfller, Frank E.

AU - Watson, David

AU - Kemner, Kenneth M.

AU - Zhou, Jizhong

AU - Kitanidis, Peter K.

AU - Kostka, Joel E.

AU - Jardine, Philip M.

AU - Criddle, Craig S.

PY - 2010/7/1

Y1 - 2010/7/1

N2 - The effects of nitrate on the stability of reduced, immobilized uranium were evaluated in field experiments at a U.S. Department of Energy site in Oak Ridge, TN. Nitrate (2.0 mM) was injected into a reduced region of the subsurface containing high levels of previously immobilized U(IV). The nitrate was reduced to nitrite, ammonium, and nitrogen gas; sulfide levels decreased; and Fe(II) levels increased then deceased. Uranium remobilization occurred concomitant with nitrite formation, suggesting nitrate-dependent, iron-accelerated oxidation of U(IV). Bromide tracer results indicated changes in subsurface flowpaths likely due to gas formation and/or precipitate. Desorption-adsorption of uranium by the iron-rich sediment impacted uranium mobilization and sequestration. After rereduction of the subsurface through ethanol additions, background groundwater containing high levels of nitrate was allowed to enter the reduced test zone. Aqueous uranium concentrations increased then decreased. Clone library analyses of sediment samples revealed the presence of denitrifying bacteria that can oxidize elemental sulfur, H2S, Fe(II), and U(IV) (e.g., Thiobacillus spp.), and a decrease in relative abundance of bacteria that can reduce Fe(III) and sulfate. XANES analyses of sediment samples confirmed changes in uranium oxidation state. Addition of ethanol restored reduced conditions and triggered a short-term increase in Fe(II) and aqueous uranium, likely due to reductive dissolution of Fe(III) oxides and release of sorbed U(VI). After two months of intermittent ethanol addition, sulfide levels increased, and aqueous uranium concentrations gradually decreased to <0.1 μM.

AB - The effects of nitrate on the stability of reduced, immobilized uranium were evaluated in field experiments at a U.S. Department of Energy site in Oak Ridge, TN. Nitrate (2.0 mM) was injected into a reduced region of the subsurface containing high levels of previously immobilized U(IV). The nitrate was reduced to nitrite, ammonium, and nitrogen gas; sulfide levels decreased; and Fe(II) levels increased then deceased. Uranium remobilization occurred concomitant with nitrite formation, suggesting nitrate-dependent, iron-accelerated oxidation of U(IV). Bromide tracer results indicated changes in subsurface flowpaths likely due to gas formation and/or precipitate. Desorption-adsorption of uranium by the iron-rich sediment impacted uranium mobilization and sequestration. After rereduction of the subsurface through ethanol additions, background groundwater containing high levels of nitrate was allowed to enter the reduced test zone. Aqueous uranium concentrations increased then decreased. Clone library analyses of sediment samples revealed the presence of denitrifying bacteria that can oxidize elemental sulfur, H2S, Fe(II), and U(IV) (e.g., Thiobacillus spp.), and a decrease in relative abundance of bacteria that can reduce Fe(III) and sulfate. XANES analyses of sediment samples confirmed changes in uranium oxidation state. Addition of ethanol restored reduced conditions and triggered a short-term increase in Fe(II) and aqueous uranium, likely due to reductive dissolution of Fe(III) oxides and release of sorbed U(VI). After two months of intermittent ethanol addition, sulfide levels increased, and aqueous uranium concentrations gradually decreased to <0.1 μM.

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JO - Environmental Science and Technology

JF - Environmental Science and Technology

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Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface

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