Fe isotope fractionation during equilibration of Fe-organic complexes

Jennifer L.L. Morgan, Laura E. Wasylenki, Jochen Nuester, Ariel Anbar

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Despite the importance of Fe-organic complexes in the environment, few studies have investigated Fe isotope effects driven by changes in Fe coordination that involve organic ligands. Previous experimental (Dideriksen et al., 2008, Earth Planet Sci. Lett. 269:280-290) and theoretical (Domagal-Goldman et al., 2009, Geochim. Cosmochim. Acta 73:1-12) studies disagreed on the sense of fractionation between Fe-desferrioxamine B (Fe-DFOB) and Fe(H 2O)63+. Using a new experimental technique that employs a dialysis membrane to separate equilibrated Fe-ligand pools, we measured the equilibrium isotope fractionations between Fe-DFOB and (1) Fe bound to ethylenediaminetetraacetic acid (EDTA) and (2) Fe bound to oxalate. We observed no significant isotope fractionation between Fe-DFOB and Fe-EDTA (Δ 56/54FeFe-DFOB/Fe-EDTA ≈ 0.02 ± 0.11%o) and a small but significant fractionation between Fe-DFOB and Fe-oxalate (Δ56/54FeFe-DFOB/Fe-EDTA-ox3 = 0.20 ± 0.11%). Taken together, our results and those of Dideriksen et al. (2008) reveal a strong positive correlation between measured fractionation factors and the Fe-binding affinity of the ligands. This correlation supports the experimental results of Dideriksen et al. (2008). Further, it provides a simple empirical tool that may be used to predict fractionation factors for Fe-ligand complexes not yet studied experimentally.

Original languageEnglish (US)
Pages (from-to)6095-6101
Number of pages7
JournalEnvironmental Science and Technology
Volume44
Issue number16
DOIs
StatePublished - Aug 15 2010

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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