Impact of organic acids and mineral properties on microbial iron oxide reduction.

Microbial Fe oxide reduction is essential in soil and groundwater ecosystems and plays an important role in microbial degradation of organic contaminants. This work showed that citrate, abundant in soils, leads to colloid stabilization out of macroaggregate ferrihydrite and enhances microbial Fe reduction. Results indicated that reactivity of ferrihydrite decreases with decreasing aggregation state below a critical size. Therefore, reactivity of Fe oxides and therefore microbial turnover rates are strongly influenced by their aggregate size and presence of organic acids