Microbial Reduction of CobaltIIIEDTA- in the Presence and Absence of Manganese(IV) Oxide

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• 作者：Yuri A. Gorby ; Frank Caccavo ; Jr. ; and Harvey Bolton ; Jr.
• 刊名：Environmental Science & Technology
• 出版年：1998
• 出版时间：January 15, 1998
• 年：1998
• 卷：32
• 期：2
• 页码：244 - 250
• 全文大小：234K
• 年卷期：v.32,no.2(January 15, 1998)
• ISSN：1520-5851

文摘

Codisposal of ⁶⁰Co²⁺ and EDTA haspromoted the transportof radioactive ⁶⁰Co in the environment as⁶⁰CoEDTAcomplexes. Chemical oxidation ofCo^IIEDTA^2- tohighlystable and mobile Co^IIIEDTA^- bymanganese(VI) oxide mineralscan occur under aerobic and anaerobic conditions.Reduction of Co(III) to Co(II) decreases the stabilityof theradionuclide-chelate complex and can limit the transportof the ⁶⁰Co in subsurface environments. Thisstudy investigated the microbial reduction ofCo^IIIEDTA^- in the presenceand absence of reactive manganese(IV) oxides.Themetal-reducing bacterium Shewanella alga strainBrYenzymatically reduced Co^IIIEDTA^- toCo^IIEDTA^2- with a 1:1stoichiometry. Reduction ofCo^IIIEDTA^- was not affectedby radioactive⁶⁰Co^IIIEDTA^- atconcentrations exceedingthose recorded in contaminated environments.Bacterialreduction of Co^IIIEDTA^- could be coupledto the chemicaloxidation of Co^IIEDTA^2- by themanganese(IV) oxide mineralpyrolusite, resulting in biotic-abiotic cycling betweenCo^IIEDTA^2- andCo^IIIEDTA^-.Co^IIIEDTA^-significantlyincreased the rate and extent of manganese(IV) oxidereduction in the presence of metal reducing bacteria, and theCo^IIEDTA^2- complex did not dissociate inthese anoxicstudies. Direct reduction ofCo^IIIEDTA^- bymicroorganismsand geochemical oxidation of Co^IIEDTA^2-by manganese(IV) oxides are important components of a complex set ofcoupled microbial and geochemical reactions that mayinfluence the fate and transport of⁶⁰Co^IIIEDTA^2- intheenvironment.