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Type: Journal article
Title: Cobalt distribution and speciation: Effect of aging, intermittent submergence, in situ rice roots
Author: Beak, D.
Kirby, J.
Hettiarachchi, G.
Wendling, L.
McLaughlin, M.
Khatiwada, R.
Citation: Journal of Environmental Quality, 2011; 40(3):679-695
Publisher: Amer Soc Agronomy
Issue Date: 2011
ISSN: 0047-2425
Statement of
Douglas G. Beak, Jason K. Kirby, Ganga M. Hettiarachchi, Laura A. Wendling, Michael J. McLaughlin and Raju Khatiwada
Abstract: The speciation and distribution of Co in soils is poorly understood. This study was conducted using x-ray absorption spectroscopy (XAS) techniques to examine the influence of soluble cobalt in the +2 oxidation state (Co[II]) aging, submergence-dried cycling, and the presence of in vivo rice roots on the speciation and distribution of added Co(II) in soils. In the aging and submerged-dried cycling studies, Co was found to be associated with Mn oxide fraction (23 to 100% of total Co) and Fe oxide fractions (0 to 77% of total Co) of the soils as either Co(II) species or a mixed Co(II), and Co in the +3 oxidation state (Co[III]) species. The surface speciation of Co in the Mn oxide fraction suggests an innersphere complex was present and the speciation of Co in the Fe oxide fraction was an innersphere surface complex. The in vivo root box experiments showed similar Co speciation in the Mn oxide fraction (13 to 76% of total Co) as the aging and submerged-dried cycling studies. However, the Fe oxide fraction of the soil was unimportant in Co retention. A significant amount (24 to 87% of total Co) of the Co in root box treatments was identified as a Co precipitate. The importance of this finding is that in the presence of rice roots, the Co is redistributed to a Co precipitate. This work confirmed earlier macroscopic work that Mn oxides are important in the sequestration of Co in soils and the influence of roots needs to be taken into account when addressing Co speciation. The information gained from this study will be used to improve models to predict the lability and hence the availability of Co in terrestrial environments.
Keywords: Oryza sativa; Plant Roots; Oxides; Cobalt; Manganese; Soil; Soil Pollutants; Fresh Water; Water Movements; Environmental Monitoring; Oxidation-Reduction; X-Ray Absorption Spectroscopy
Rights: Copyright © 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.
RMID: 0020106650
DOI: 10.2134/jeq2010.0139
Appears in Collections:Agriculture, Food and Wine publications
Environment Institute publications

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