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Title: Rifle geochemistry and abiotic U(VI) reactions under Fe-reducing conditions

Publication Date:
Research Org.:
USGS, Menlo Park, CA
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
Report Number(s):
R&D Project: ERSD 1027705
Resource Type:
Resource Relation:
Conference: Annual Environmental Remediation Science Program (ERSP) Principal Investigator Meeting, April 16-19, 2007, Lansdowne, VA
Country of Publication:
United States

Citation Formats

James A. Davis. Rifle geochemistry and abiotic U(VI) reactions under Fe-reducing conditions. United States: N. p., 2007. Web.
James A. Davis. Rifle geochemistry and abiotic U(VI) reactions under Fe-reducing conditions. United States.
James A. Davis. Thu . "Rifle geochemistry and abiotic U(VI) reactions under Fe-reducing conditions". United States. doi:.
title = {Rifle geochemistry and abiotic U(VI) reactions under Fe-reducing conditions},
author = {James A. Davis},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Apr 19 00:00:00 EDT 2007},
month = {Thu Apr 19 00:00:00 EDT 2007}

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  • Dissimilatory metal-reducing microorganisms may be useful in processes designed for selective removal of uranium from aqueous streams. These bacteria can use U(VI) as an electron acceptor and thereby reduce soluble U(VI) to insoluble U(IV). While significant research has been devoted to demonstrating and describing the mechanism of dissimilatory metal reduction, the reaction kinetics necessary to apply this for remediation processes have not been adequately defined. In this study, pure culture Shewanella alga strain BrY reduced U(VI) under non-growth conditions in the presence of excess lactate as the electron donor. Initial U(VI) concentrations ranged from 13 to 1,680{micro}M. A maximum specificmore » U(VI) reduction rate of 2.37 {micro}mole-U(VI)/(mg-biomass h) and Monod half-saturation coefficient of 132 {micro}M-U(VI) were calculated from measured U(VI) reduction rates. U(VI) reduction activity was sustained at 60% of this rate for at least 80 h. The initial presence of oxygen at a concentration equal to atmospheric saturation at 22 C delays but does not prevent U(VI) reduction. The rate of U(VI) reduction by BrY is comparable or better than rates reported for other metal reducing species. BrY reduces U(VI) at a rate that is 30% of its Fe(III) reduction rate.« less
  • Dinitrophenols are hazardous chemicals commonly detected in the environment. Little is known about their fate under sulfate-reducing conditions (SRC) where H{sub 2}S level is elevated due to microbial activity. Dinitrophenols are susceptible to both biotic and abiotic transformation under SRC. The objectives of this research are to investigate dinitrophenol transformation using hydrogen sulfide as a reductant, and to determine factors that affect the abiotic transformation kinetics under SRC. Dinitrophenols studied were 2,4-dinitrophenol (DNP), 4,6-dinitro-o-cresol (DNOC), and 2-sec-butyl-4,6-dinitrophenol (dinoseb). All three dinitrophenols were transformed through an ortho-nitroreduction pathway. In the presence of H{sub 2}S as the bulk reductant and a smallmore » amount of trace metals (10{sup -6} to 10{sup -7} M), pseudo-first-order kinetics was observed. Addition of yeast extract (YE, 0.02%) enhanced dinoseb transformation rate significantly. An increase in HS concentration resulted in Michaelis-Menton type kinetics for dinoseb in the presence of trace metals and YE, suggesting that trace metals and YE functioned as electron mediators.« less
  • No abstract prepared.
  • The potential for biological reduction of Cr(VI) under acidic conditions was evaluated with the acidophilic, facultatively metal-reducing bacterium Acidiphilium cryptum strain JF-5 to explore the role of acidophilic microorganisms in the Cr cycle in low-pH environments. An anaerobic suspension of washed A. cryptum cells rapidly reduced 50 M Cr(VI) at pH 3.2; biological reduction was detected from pH 1.7-4.7. The reduction product, confirmed by XANES analysis, was entirely Cr(III) that was associated predominantly with the cell biomass (70-80%) with the residual residing in the aqueous phase. Reduction of Cr(VI) showed a pH optimum similar to that for growth and wasmore » inhibited by 5 mM HgCl2, suggesting that the reaction was enzyme-mediated. Introduction of O2 into the reaction medium slowed the reduction rate only slightly, whereas soluble Fe(III) (as ferric sulfate) increased the rate dramatically, presumably by the shuttling of electrons from bioreduced Fe(II) to Cr(VI) in a coupled biotic-abiotic cycle. Starved cells could not reduce Cr(VI) when provided as sole electron acceptor, indicating that Cr(VI) reduction is not an energy-conserving process in A. cryptum. We speculate, rather, that Cr(VI) reduction is used here as a detoxification mechanism.« less