Dissimilatory Iron-Reducing Microorganisms Are Present and Active in the Sediments of the Doce River and Tributaries Impacted by Iron Mine Tailings from the Collapsed Fundão Dam (Mariana, MG, Brazil)

On 5 November 2015, a large tailing deposit failed in Brazil, releasing an estimated 32.6 to 62 million m3 of iron mining tailings into the environment. Tailings from Fundão Dam flowed down through Gualaxo do Norte and Carmo riverbeds floodplains reached Doce River. Since then, bottom sediments have become enriched Fe(III) oxyhydroxides. Dissimilatory iron-reducing microorganisms (DIRMs) are anaerobes able couple organic matter oxidation reduction, producing CO2 Fe(II), which can precipitate as magnetite (FeO·Fe2O3) other Fe(II) minerals. In this work, we investigated presence DIRMs affected non-affected Rivers. The increase concentrations culture media over time indicated Fe(III)-reducing all tested, could reduce both amorphous ferric oxyhydroxide. Half our enrichment cultures converted oxyhydroxide magnetite, was characterized by X-ray diffraction, transmission electron microscopy, magnetic measurements. conversion solid phases soluble and/or is characteristic DIRM cultures. River tributaries points possibility reductive dissolution goethite (α-FeOOH) hematite (α-Fe2O3) sediments, along with consumption organics, release trace elements, impairment water quality.