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Title: Interactions Between Microbial Iron Reduction and Metal Geochemistry: Effect of Redox Cycling on Transition Metal Speciation in Iron Bearing Sediments

Abstract

Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respect to Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. Inmore » addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a ~3× increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by ~12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest that in situ redox cycling may serve as an effective method for mitigating divalent metal contamination in subsurface environments.« less

Authors:
; ;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - SC
OSTI Identifier:
912346
Report Number(s):
INL/JOU-05-00678
Journal ID: ISSN 0013-936X; ESTHAG; TRN: US200801%%781
DOE Contract Number:  
DE-AC07-99ID-13727
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science and Technology; Journal Volume: 40; Journal Issue: 6
Country of Publication:
United States
Language:
English
Subject:
36 - MATERIALS SCIENCE, 58 - GEOSCIENCES; AIR; BEARINGS; CONTAMINATION; COORDINATION NUMBER; GEOCHEMISTRY; GOETHITE; IRON; MIXTURES; OXIDATION; SEDIMENTS; TRANSITION ELEMENTS; metal; microbial; redox cycling; sediments

Citation Formats

D. Craig Cooper, Flynn W. Picardal, and Aaron J. Coby. Interactions Between Microbial Iron Reduction and Metal Geochemistry: Effect of Redox Cycling on Transition Metal Speciation in Iron Bearing Sediments. United States: N. p., 2006. Web. doi:10.1021/es051778t.
D. Craig Cooper, Flynn W. Picardal, & Aaron J. Coby. Interactions Between Microbial Iron Reduction and Metal Geochemistry: Effect of Redox Cycling on Transition Metal Speciation in Iron Bearing Sediments. United States. doi:10.1021/es051778t.
D. Craig Cooper, Flynn W. Picardal, and Aaron J. Coby. Wed . "Interactions Between Microbial Iron Reduction and Metal Geochemistry: Effect of Redox Cycling on Transition Metal Speciation in Iron Bearing Sediments". United States. doi:10.1021/es051778t.
@article{osti_912346,
title = {Interactions Between Microbial Iron Reduction and Metal Geochemistry: Effect of Redox Cycling on Transition Metal Speciation in Iron Bearing Sediments},
author = {D. Craig Cooper and Flynn W. Picardal and Aaron J. Coby},
abstractNote = {Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respect to Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a ~3× increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by ~12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest that in situ redox cycling may serve as an effective method for mitigating divalent metal contamination in subsurface environments.},
doi = {10.1021/es051778t},
journal = {Environmental Science and Technology},
number = 6,
volume = 40,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2006},
month = {Wed Feb 01 00:00:00 EST 2006}
}