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Title: INVESTIGATION OF THE TRANSFORMATION OF URANIUM UNDER IRON-REDUCING CONDITIONS: REDUCTION OF UVI BY BIOGENIC FEII/FEIII HYDROXIDE (GREEN RUST)

Abstract

The recent identification of green rusts (GRs) as products of the reduction of FeIII oxyhydroxides by dissimilatory iron-reducing bacteria, coupled with the ability of synthetic (GR) to reduce UVI species to insoluble UO2, suggests that biogenic green rusts (BioGRs) may play an important role in the speciation (and thus mobility) of U in FeIII-reducing environments. The objective of our research was to examine the potential for BioGR to affect the speciation of U under FeIII-reducing conditions. To meet this objective, we designed and executed a hypothesis-driven experimental program to identify key factors leading to the formation of BioGRs as products of dissimilatory FeIII reduction, to determine the key factors controlling the reduction of UVI to UIV by GRs, and to identify the resulting U-bearing mineral phases. The results of this research significantly increase our understanding of the coupling of biotic and abiotic processes with respect to the speciation of U in iron-reducing environments. In particular, the reduction of UVI to UIV by BioGR with the subsequent formation of U-bearing mineral phases may be effective for immobilizing U in suboxic subsurface environments. This information has direct applications to contaminant transport modeling and bioremediation engineering for natural or enhanced in situ remediationmore » of subsurface contamination.« less

Authors:
; ;
Publication Date:
Research Org.:
Argonne National Laboratory (ANL), Argonne, IL; University of Iowa
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
896297
Report Number(s):
ERSD-1022397-2006
R&D Project: ERSD 1022397; TRN: US0700760
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; BACTERIA; BIOREMEDIATION; CONTAMINATION; HYDROXIDES; SIMULATION; TRANSFORMATIONS; TRANSPORT; URANIUM

Citation Formats

O'Loughlin, Edward J., Scherer, Michelle M., and Kemner, Kenneth M.. INVESTIGATION OF THE TRANSFORMATION OF URANIUM UNDER IRON-REDUCING CONDITIONS: REDUCTION OF UVI BY BIOGENIC FEII/FEIII HYDROXIDE (GREEN RUST). United States: N. p., 2006. Web. doi:10.2172/896297.
O'Loughlin, Edward J., Scherer, Michelle M., & Kemner, Kenneth M.. INVESTIGATION OF THE TRANSFORMATION OF URANIUM UNDER IRON-REDUCING CONDITIONS: REDUCTION OF UVI BY BIOGENIC FEII/FEIII HYDROXIDE (GREEN RUST). United States. doi:10.2172/896297.
O'Loughlin, Edward J., Scherer, Michelle M., and Kemner, Kenneth M.. Sun . "INVESTIGATION OF THE TRANSFORMATION OF URANIUM UNDER IRON-REDUCING CONDITIONS: REDUCTION OF UVI BY BIOGENIC FEII/FEIII HYDROXIDE (GREEN RUST)". United States. doi:10.2172/896297. https://www.osti.gov/servlets/purl/896297.
@article{osti_896297,
title = {INVESTIGATION OF THE TRANSFORMATION OF URANIUM UNDER IRON-REDUCING CONDITIONS: REDUCTION OF UVI BY BIOGENIC FEII/FEIII HYDROXIDE (GREEN RUST)},
author = {O'Loughlin, Edward J. and Scherer, Michelle M. and Kemner, Kenneth M.},
abstractNote = {The recent identification of green rusts (GRs) as products of the reduction of FeIII oxyhydroxides by dissimilatory iron-reducing bacteria, coupled with the ability of synthetic (GR) to reduce UVI species to insoluble UO2, suggests that biogenic green rusts (BioGRs) may play an important role in the speciation (and thus mobility) of U in FeIII-reducing environments. The objective of our research was to examine the potential for BioGR to affect the speciation of U under FeIII-reducing conditions. To meet this objective, we designed and executed a hypothesis-driven experimental program to identify key factors leading to the formation of BioGRs as products of dissimilatory FeIII reduction, to determine the key factors controlling the reduction of UVI to UIV by GRs, and to identify the resulting U-bearing mineral phases. The results of this research significantly increase our understanding of the coupling of biotic and abiotic processes with respect to the speciation of U in iron-reducing environments. In particular, the reduction of UVI to UIV by BioGR with the subsequent formation of U-bearing mineral phases may be effective for immobilizing U in suboxic subsurface environments. This information has direct applications to contaminant transport modeling and bioremediation engineering for natural or enhanced in situ remediation of subsurface contamination.},
doi = {10.2172/896297},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Dec 31 00:00:00 EST 2006},
month = {Sun Dec 31 00:00:00 EST 2006}
}

Technical Report:

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  • The research we are proposing addresses fundamental aspects of the effects of coupled biotic and abiotic processes on U speciation in subsurface environments where Fe redox cycling is significant. The long-term objective of this research is to evaluate whether reduction of U{sup VI} by biogenic GRs is a significant immobilization mechanism in subsurface environments. Our preliminary experiments have shown that biogenic GRs can reduce U{sup VI} to U{sup IV}; however, little is known about how biogeochemical conditions (such as pH, U concentration, carbonate concentration, and the presence of cocontaminants) and GR composition affect the rate and products of U{sup VI}more » reduction by GRs. It is also unclear which biogeochemical conditions favor formation of GR over other non-reactive Fe-bearing biomineralization products from the reduction of Fe{sup III} by DIRB. To address these issues, the following objectives are proposed: (1) Identify the geochemical conditions that favor the formation of biogenic GRs from the reduction of Fe{sup III} oxyhydroxides by DIRB (e.g., Shewanella and Geobacter species). (2) Characterize the chemical composition of biogenic GRs (e.g., Fe{sup II}:Fe{sup III} ratios and interlayer anions) and the effects of compositional variability on the rate and extent of U{sup VI} reduction. (3) Evaluate the effects of variations in geochemical conditions--particularly pH, U concentration, carbonate concentration, the presence of organic ligands, and the presence of reducible co-contaminants--both on the kinetics of U{sup VI} reduction by biogenic GR and on the composition of U-bearing mineral phases. Particular attention will be given to examining geochemical conditions relevant to conditions at DOE field sites. (4) Determine the potential for coupling the reduction of Fe{sup III} by DIRB to the reduction of U{sup VI} via biogenic Fe{sup II} species (including biogenic GRs). The objectives outlined above will be achieved by testing the following hypotheses: (1) The formation of GRs by dissimilatory Fe{sup III} reduction is controlled by Fe{sup III} speciation, solution composition, and microbial physiology. (2) The chemical composition and structural properties of biogenic GRs are variable and depend on the conditions under which they were formed. (3) The rate of U{sup VI} reduction by biogenic GRs varies depending on their chemical composition and structure, particularly with respect to the Fe{sup II}/Fe{sup III} ratio and the nature of the interlayer anions. (4) The rate of U{sup VI} reduction by a given biogenic GR is affected by the solution composition (e.g., pH, uranium concentration, the concentration of carbonate and other ligands, and the presence of other potential oxidants). Moreover, the solution composition affects both the speciation of U{sup VI} and U{sup IV} and the stability of the GR. (5) The reduction of UVI to UIV can be coupled to dissimilatory FeIII reduction under conditions that promote the formation of biogenic GR and other reactive Fe{sup II} species. The results of this research will increase our understanding of the coupling of biotic and abiotic processes with respect to the speciation of U in Fe{sup III}-reducing environments. This information has direct applications to understanding contaminant transport and the development of in situ bioremediation technologies for treatment of subsurface U contamination.« less
  • No abstract prepared.
  • Our understanding of subsurface microbiology is hindered by the inaccessibility of this environment, particularly when the hydrogeologic medium is contaminated with toxic substances. Research in our labs indicated that the composition of the growth medium (e.g., bicarbonate complexation of U(VI)) and the underlying mineral phase (e.g., hematite) significantly affects the rate and extent of U(VI) reduction and immobilization through a variety of effects. Our research was aimed at elucidating those effects to a much greater extent, while exploring the potential for U(IV) reoxidation and subsequent re-mobilization, which also appears to depend on the mineral phases present in the system. Inmore » situ coupons with a variety of mineral phases were placed in monitoring wells at the NABIR FRC. These coupons showed that the mineral phase composition significantly affected the resulting attached phase microbial community. Our comparative use of both batch and open flow reactors (more representative of field conditions) indicates that hydrodynamics and continual influx of substrate and contaminants can also yield significantly different results than those obtained with closed serum bottles. To this end, the following overall experimental hypothesis tested was the following: On a mineral surface under anaerobic conditions, accumulations of secondary inorganic precipitates are controlled by a) the bacteria associated with the mineral surface, b) the electron acceptors available for anaerobic bacterial respiration, and c) local hydrodynamics and pH buffers govern micro- and meso-scale interaction of U in the presence of electron donors and acceptors, and nutrients.« less