Title

Quantitative Charge State Analysis Of Manganese Biominerals In Aqueous Suspension Using Scanning Transmission X-Ray Microscopy (Stxm)

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(II)-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(III)-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. © 2003 Elsevier Science Ltd.

Publication Date

3-15-2003

Publication Title

Geochimica et Cosmochimica Acta

Volume

67

Issue

6

Number of Pages

1089-1098

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/S0016-7037(02)01229-2

Socpus ID

0037443981 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0037443981

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