In Situ Bioreduction of Uranium (VI) to Submicromolar Levels and Reoxidation by Dissolved Oxygen
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- 作者：Wei-Min Wu ; Jack Carley ; Jian Luo ; Matthew A. Ginder-Vogel ; Erick Cardenas ; Mary Beth Leigh ; Chiachi Hwang ; Shelly D. Kelly ; Chuanmin Ruan ; Liyou Wu ; Joy Van Nostrand ; Terry Gentry ; Kenneth Lowe ; Toni
- 刊名：Environmental Science & Technology
- 出版年：2007
- 出版时间：August 15, 2007
- 年：2007
- 卷：41
- 期：16
- 页码：5716 - 5723
- 全文大小：366K
- 年卷期：v.41,no.16(August 15, 2007)
- ISSN：1520-5851
文摘
Groundwater within Area 3 of the U.S. Department ofEnergy (DOE) Environmental Remediation SciencesProgram (ERSP) Field Research Center at Oak Ridge, TN(ORFRC) contains up to 135 
M uranium as U(VI). Througha series of experiments at a pilot scale test facility, weexplored the lower limits of groundwater U(VI) that can beachieved by in-situ biostimulation and the effects ofdissolved oxygen on immobilized uranium. Weekly 2 dayadditions of ethanol over a 2-year period stimulated growthof denitrifying, Fe(III)-reducing, and sulfate-reducingbacteria, and immobilization of uranium as U(IV), withdissolved uranium concentrations decreasing to low levels.Following sulfite addition to remove dissolved oxygen,aqueous U(VI) concentrations fell below the U.S.Environmental Protection Agengy maximum contaminantlimit (MCL) for drinking water (<30 g L-1 or 0.126 M). Underanaerobic conditions, these low concentrations werestable, even in the absence of added ethanol. However,when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L-1) entered the injection well, spatially variablechanges in aqueous U(VI) occurred over a 60 day period,with concentrations increasing rapidly from <0.13 to 2.0M at a multilevel sampling (MLS) well located close to theinjection well, but changing little at an MLS well locatedfurther away. Resumption of ethanol addition restoredreduction of Fe(III), sulfate, and U(VI) within 36 h. After 2years of ethanol addition, X-ray absorption near-edge structurespectroscopy (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 concentrationsin MLS wells were less than 0.1 M. The microbialcommunity at MLS wells with low U(VI) contained bacteriathat are known to reduce uranium, including Desulfovibriospp. and Geobacter spp., in both sediment and groundwater.The dominant Fe(III)-reducing species were Geothrix spp.
M uranium as U(VI). Througha series of experiments at a pilot scale test facility, weexplored the lower limits of groundwater U(VI) that can beachieved by in-situ biostimulation and the effects ofdissolved oxygen on immobilized uranium. Weekly 2 dayadditions of ethanol over a 2-year period stimulated growthof denitrifying, Fe(III)-reducing, and sulfate-reducingbacteria, and immobilization of uranium as U(IV), withdissolved uranium concentrations decreasing to low levels.Following sulfite addition to remove dissolved oxygen,aqueous U(VI) concentrations fell below the U.S.Environmental Protection Agengy maximum contaminantlimit (MCL) for drinking water (<30 g L-1 or 0.126 M). Underanaerobic conditions, these low concentrations werestable, even in the absence of added ethanol. However,when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L-1) entered the injection well, spatially variablechanges in aqueous U(VI) occurred over a 60 day period,with concentrations increasing rapidly from <0.13 to 2.0M at a multilevel sampling (MLS) well located close to theinjection well, but changing little at an MLS well locatedfurther away. Resumption of ethanol addition restoredreduction of Fe(III), sulfate, and U(VI) within 36 h. After 2years of ethanol addition, X-ray absorption near-edge structurespectroscopy (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 concentrationsin MLS wells were less than 0.1 M. The microbialcommunity at MLS wells with low U(VI) contained bacteriathat are known to reduce uranium, including Desulfovibriospp. and Geobacter spp., in both sediment and groundwater.The dominant Fe(III)-reducing species were Geothrix spp.