To better understand the effects of Fe(III) oxide mineralogy on the biogeochemical dynamics of Fe, S, and C under sulfate- and iron-reducing conditions, we created bicarbonate-buffered batch systems containing lactate as the electron donor and with sulfate and ferrihydrite, goethite, or lepidocrocite as electron acceptors that were inoculated with native sediment containing a mixed microbial community. Prior to indications of Fe(III) or sulfate reduction, lactate was rapidly fermented to acetate and propionate, with subsequent sulfate reduction coupled to complete oxidation of propionate. Distinctly different community profiles were observed for each of the Fe(III) oxides with high and low sulfate. These results suggest that when DIR is slow and both sulfate and Fe(III) oxide are available, sulfide produced by microbial sulfate reduction can drive Fe(III) oxide reduction. However, the rate and extent of the Fe(III) reduction by sulfide are strongly affected by the specific Fe(III) oxide.

Effects of dissimilatory sulfate reduction on Fe(III) oxide reduction and microbial community development

245th National Meeting (2013)

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