Density functional theory predictions of equilibrium isotope fractionation of iron due to redox changes and organic complexation

Domagal-Goldman, Shawn; Kubicki, James D.

doi:10.1016/j.gca.2008.05.066

Cited by 70 publications

(56 citation statements)

References 48 publications

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“…Because Fe(III) preferentially incorporates heavy isotopes relative to Fe(II), partial oxidation of Fe(II) results in heavy isotope enrichment in Fe(III) precipitates Beard and Johnson, 2004;Anbar et al, 2005;Johnson and Beard, 2006;Johnson et al, 2008;Domagal-Goldman and Kubicki, 2008). However, (near-)quantitative oxidation of aqueous ferrous iron will yield ferric iron species with the same Fe isotopic composition.…”

Section: Redox Control On Fe Isotope Fractionationmentioning

confidence: 99%

Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

Zhang

Zhu

Yan

et al. 2015

Earth and Planetary Science Letters

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Section: Redox Control On Fe Isotope Fractionationmentioning

confidence: 99%

Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

Zhang

Zhu

Yan

et al. 2015

Earth and Planetary Science Letters

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“…Much attention has been paid to the isotopic fractionation among the major species controlling the speciation of the transition metals (i. e. Fe, Ni, Cu, Zn, Cr) in natural fluids, including seawater, and its application in geochemistry and biogeochemistry (Schauble et al, 2001;Anbar et al, 2005;Fujii et al, 2006Fujii et al, , 2011Fujii et al, , 2013Fujii et al, , 2014Domagal-Goldman and Kubicki, 2008;Hill and Schauble, 2008;Zuccolini, 2005, 2009;Black et al, 2011;Saunier et al, 2011). In contrast, much less attention has been devoted to the isotopic fractionation among the inorganic and organic species that control the aqueous speciation of the alkaline Earth metals, including magnesium (the notable exception is the observation by Li et al (2014) of a preferential partitioning of light Mg isotopes into aqueous Mg-EDTA complexes relative to Mg aquo ions).…”

Section: Introductionmentioning

confidence: 99%

The control of carbonate mineral Mg isotope composition by aqueous speciation: Theoretical and experimental modeling

et al. 2016

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“…Schauble et al, 2001;Welch et al, 2003). In addition, chloride speciation may change Fe isotope fractionations on the order of 0.2 ‰/M Cl − in 56 Fe/ 54 Fe ratios (e.g., Hill and Schauble, 2008), and isotopic fractionations up to 1 ‰ are predicted or measured between aqueous Fe and Fe complexed by organic ligands (e.g., Domagal-Goldman and Kubicki, 2008;Dideriksen et al, 2008). Iron isotope fractionation during bacterial Fe(II) oxidation has been investigated in experiments on anaerobic photosynthetic Fe(II)-oxidizing bacteria at circum-neutral pH, where CO 2 was the terminal electron acceptor (Croal et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria

Kappler

Johnson

Crosby

et al. 2010

Geochimica et Cosmochimica Acta

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Iron isotope fractionations produced during chemical and biological Fe(II) oxidation are sensitive to the proportions and nature of dissolved and solid-phase Fe species present, as well as the extent of isotopic exchange between precipitates and aqueous Fe. Iron isotopes therefore potentially constrain the mechanisms and pathways of Fe redox transformations in modern and ancient environments. In the present study, we followed in batch experiments Fe isotope fractionations between Fe(II) aq and Fe(III) oxide/hydroxide precipitates produced by the Fe(III) mineral encrusting, nitrate-reducing, Fe (II)-oxidizing Acidovorax sp. strain BoFeN1. Isotopic fractionation in 56 Fe/ 54 Fe approached that expected for equilibrium conditions, assuming an equilibrium Δ 56 Fe Fe(OH)3 -Fe(II)aq fractionation factor of +3.0 ‰. Previous studies have shown that Fe(II) oxidation by this Acidovorax strain occurs in the periplasm, and we propose that Fe isotope equilibrium is maintained through redox cycling via coupled electron and atom exchange between Fe(II) aq and Fe(III) precipitates in the contained environment of the periplasm. In addition to the apparent equilibrium isotopic fractionation, these experiments also record the kinetic effects of initial rapid oxidation, and possible phase transformations of the Fe(III) precipitates. Attainment of Fe isotope equilibrium between Fe(III) oxide/hydroxide precipitates and Fe(II) aq by neutrophilic, Fe(II)-oxidizing bacteria or through abiologic Fe(II) aq oxidation is generally not expected or observed, because the poor solubility of their metabolic product, i.e. Fe(III), usually leads to rapid precipitation of Fe(III) minerals, and hence expression of a kinetic fractionation upon precipitation; in the absence of redox cycling between Fe (II) aq and precipitate, kinetic isotope fractionations are likely to be retained. These results highlight the distinct Fe isotope fractionations that are produced by different pathways of biological and abiological Fe(II) oxidation.

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Density functional theory predictions of equilibrium isotope fractionation of iron due to redox changes and organic complexation

Cited by 70 publications

References 48 publications

Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

Oxygenation of a Cryogenian ocean (Nanhua Basin, South China) revealed by pyrite Fe isotope compositions

The control of carbonate mineral Mg isotope composition by aqueous speciation: Theoretical and experimental modeling

Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria

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