Microbial reduction of Fe(III) minerals occurring in soil and sediments, leads to mineral dissolution and transformation, as well as to the formation of reactive iron minerals. These geomicrobial processes thus influence the fate of nutrients and contaminants by both sorption and transformation reactions. The microbial reduction of Fe(III) minerals is often limited by the accessibility of the poorly soluble electron acceptors. It has been shown that redox-active biochar and natural organic matter (humic substances) can function as electron shuttles between microorganisms and the Fe(III) minerals and stimulate the rates and extent of Fe(III) mineral reduction. Here we present new data on the effect of biochar identity, variations of biochar particle sizes, and different biochar concentrations on biochar’s ability to either stimulate or inhibit microbial Fe(III) reduction. Additionally, we tested the effect of standard procedures used for isolation of humic substances (including extraction with strong acidic and alkaline solutions under oxic conditions) as they are used, <i>e.g</i>., by the International Humic Substance Society, IHSS, on the chemical and electron shuttling properties of the isolated humic material.

Electron transfer between microorganisms and Fe(III) minerals mediated by redox-active biochar and natural organic matter

255th National Meeting (2018)

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