Quantitative charge state analysis of manganese biominerals in aqueous suspension using Scanning Transmission X-ray Microscopy (STXM)

    Authors

    K. Pecher; D. McCubbery; E. Kneedler; J. Rothe; J. Bargar; G. Meigs; L. Cox; K. Nealson;B. Tonner

    Comments

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    Abbreviated Journal Title

    Geochim. Cosmochim. Acta

    Keywords

    TRANSITION-METAL COMPOUNDS; ADVANCED LIGHT-SOURCE; MARINE BACILLUS SP; ABSORPTION-SPECTROSCOPY; MATERIALS SCIENCE; OXIDATION-STATE; STRAIN; SG-1; SPORE COATS; MN; SPECTROMICROSCOPY; Geochemistry & Geophysics

    Abstract

    We have applied Scanning Transmission Soft X-ray Microscopy (STXM) to investigate the charge state distribution of Mn in two kinds of Mn-biominerals, Mn nodules collected from Lake Michigan sediments and Mn precipitates formed by spores of a marine bacillus SG-1 under transport limited reaction conditions. A data analysis technique was developed, which allows for extraction of spatially resolved 2-d charge state maps of manganese on a submicron level. We find that the charge state of Mn dominates the spectral shape of L-edge spectra of environmentally important single oxidation state Mn minerals and that spectra of mixed oxidation state oxides can be modelled by a combination of appropriate single oxidation state reference spectra. Two-dimensional maps of charge state distributions clearly reveal domains of different oxidation states within single particles of Mn-micronodules. Spots of preferred accumulation of Mn(II) were found, which indicates biogenic precipitation of Mn(Il)-species as a first step of nodule formation. The presence of Mn(III) in the studied sediment samples suggests the involvement of one-electron oxidation processes and reaction conditions which inhibit or slow down the disproportionation of Mn(Ill)-products. Under transport limited conditions, Mn oxidation products formed by spores of the marine bacillus SG-1 can vary from cell to cell. The presence of significant amounts of Mn(III) containing species points to the involvement of one-electron oxidation reactions as in the case of the micro-nodules. Our technique and the results obtained form a new basis for the mechanistic understanding of the formation of Mn biominerals in the environment. Copyright (C) 2003 Elsevier Science Ltd.

    Journal Title

    Geochimica Et Cosmochimica Acta

    Volume

    67

    Issue/Number

    6

    Publication Date

    1-1-2003

    Document Type

    Article

    Language

    English

    First Page

    1089

    Last Page

    1098

    WOS Identifier

    WOS:000181604900001

    ISSN

    0016-7037

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