Iron oxides are ubiquitous. These tiny, often nanoscale, particles profoundly influence the quality of our water, air, and soil through the biologically-driven redox cycling between ferric and ferrous iron. We have used stable Fe isotopes in conjunction with 57Fe M�ssbauer spectroscopy to study redox reactions between ferrous Fe and Fe oxides, as well as Fe containing clays. Our results have shown that sorbed Fe(II) is oxidized by Fe(III) in Fe oxides, such as goethite, hematite, ferrihydrite, and magnetite and that Fe(II)-Fe(III) electron transfer initiates atom exchange between the Fe oxide and aqueous Fe(II). As a result of our work, and many others, a new conceptual model for redox chemistry at the Fe mineral-water interface has emerged. I will present the evidence for this revised conceptual model and discuss the implications for important environmental processes, such as trace metal cycling and contaminant fate.

Redox chemistry at the Fe mineral-water interface: New insights from isotope games

248th National Meeting (2014)

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