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Iron isotope fractionation by chemotrophic iron-oxidisers

Leighton, E. M., Elliott, T., Hawkesworth, C. J., Parkes, Ronald John and Coath, C. 2004. Iron isotope fractionation by chemotrophic iron-oxidisers. Geochimica Et Cosmochimica Acta 68 (11) , A398-A398.

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Knowledge of the isotopic behaviour of iron in natural and experimental systems has expanded considerably since initial work began in this field However, a greater understanding of the pathways and controls on Fe isotopic fractionation, produced from the abiological and biological transformations of Fe, is still needed to characterise the global Fe biogeochemical cycle in a manner comparable to that of the carbon isotope system. Oxidation and reduction of Fe by direct or indirect microbial activity plays a large role in the global cycling of Fe. The discovery of chemotrophic microorganisms able to oxidise Fe anaerobically increases the importance of Fe recycling via redox reactions in natural environments, as well as extending the diversity of Fe-utilising microbial metabolisms. Fe isotopic fractionation by strains of the chemolithotrophic bacterium Thiobacillus denitrificans, has been investigated. Batch experiments have been done using different inoculum potentials, temperatures, and pO2 levels with Fe(II) as the only electron donor. Iron isotope compositions were determined by high-resolution, multiple collector, ICP-MS, with an external precision (1 s) on d56Fe and d57Fe of ± 0.05 and 0.08 ‰, respectively. The analytical methods were similar to those in the literature [3]. Preliminary data shows a – 0.8 ‰ d56Fe Fe isotopic fractionation between Fe(II) in solution and FeOOH precipitate. This isotopic shift between substrate and product can be attributed to biological oxidation as no abiotic Fe oxidation occurred in concomitant sterile controls. Experiments examining variable pO2 levels in both abiotic and biological systems provide a useful basis to examine how the isotopic signature of biological oxidation is modified by abiotic Fe oxidation.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
ISSN: 0016-7037
Last Modified: 04 Jun 2017 02:05

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