Identification of biogenic Fe(11) oxides resulting from microbial reduction.
EMSL Project ID
1718
Abstract
The objectives of this project are to: (i) examine the effect of iron oxide mineralogy on iron mineralization induced by microbial reduction of that oxide, (ii) determine the mechanism(s) by which these transformations proceed, and (iii) determine how these processes affect the chemistry of adsorbed metals. Our approach is to expose various synthetic iron oxide minerals (e.g. ferrihydrite, goethite, lepidocrocite) to iron reducing bacteria in both the presence and absence of adsorbed Zn. The speciation of Fe(II) and Zn will be followed with time, and samples for spectroscopic work will be taken at intervals indicated by trends in the wet chemical data. Results from these bacterial experiments will be contrasted with results from analyses performed on cell-free controls. Zinc is used as a model metal because it has simple redox chemistry, is easy to analyze, is present at high concentrations at many DOE sites, and has an ionic radius similar to that of Fe(II). Previous work has shown microbially induced formation of magnetite, siderite, Zn-enriched siderite, and surface coatings of as-yet-unidentified micro-crystallites. We have also seen evidence that microbial iron reduction may transform less crystalline ferric minerals into goethite. This work is still preliminary, and we need access to equipment that can identify these transformations. Thus, we need to be able to (i) resolve crystallites in the 10 - 50 nm range, (ii) be able to obtain EDAX spectra from single crystals between 0.5 - 5 microns in size, (iii) determine the relative distribution of iron and iron-metal minerals present, (iv) be able to look at metal/Fe(II) complexes with an iron oxide surface, and (v) be able to visualize samples in a wet system. Samples need to be analyzed at room temperature, and isolated from atmospheric oxygen. Resolution specifications will be dependent on the size of the biologically induced minerals formed.
Project Details
Project type
Exploratory Research
Start Date
1999-10-25
End Date
2002-11-25
Status
Closed
Released Data Link
Team
Principal Investigator