Due to the ubiquity of redox dynamic zones in the environment, the effects of oscillating redox conditions on ferric oxide mineralogy and phosphate retention were studied.  Ferrihydrite was reduced by one of two abiotic reductants: FeSO4 or AH2DS. Changes in mineralogy and phosphate retention in relation to differences in electron transfer mechanisms were examined.  Solid phase analysis included XRD and SEM, while aqueous phosphate and ferrous iron concentrations were measured using colorimetry techniques. Preliminary batch reactions to study electron transfer mechanisms show a decreasing electron transfer when AH2DS, was used. This decrease lead to decreased Fe(II) release and mineralization of high surface area Fe (III) (hydr) oxides. Conversely, when FeSO4 was the reducing agent, an increase in aqueous Fe(II) and mineralization of Fe (III) (hydr)oxides was observed. These differences in mineralogy are expected to influence mineralogical transformations and phosphate retention upon oxidation and re-reduction.

Iron (hydr)oxide abiotic redox cycling as a proxy for riparian zone mineralogical transformations

245th National Meeting (2013)

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