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)

Abstract

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

Morphological, Microstructural, and In Situ Chemical Characteristics of Siderite Produced by Iron-Reducing Bacteria

“…Before inoculation, the headspace in each serum bottle was flushed with N 2 :CO 2 (v:v, 80%:20%) for 1 h. Triplicate bottles were used for biotic experiments, and each bottle was inoculated with 6 mL of the precultured MR-4 cells and incubated at 30 °C in the dark. Triplicate bottles were sampled at intervals of 0, 1,3,7,9,11,14,17,20,23,26,32,38,40,44,48, and 54 days for protein concentration, Fe concentration, pH quantification, TEM and SEM-Raman experiments.…”

“…3−5 Such mineralization processes induced extracellularly by DIRB could affect directly and indirectly the redox cycling and mobilization of metals and the degradation of organic contaminants in modern groundwater, soil, and sediment systems. 6,7 Unlike size-tailored and morphology-controlled magnetite nanocrystals biologically controlled by magnetotactic bacteria, 8,9 both the mineralization process and products extracellularly induced by DIRB can be influenced significantly by environmental factors under which the bacteria are growing. 10−12 For instance, DIRB produced magnetite, a mixed-valence and ferromagnetic magnetic mineral, as major end products when the bacteria are growing anaerobically with ferrihydrite (Fh) as a ferric source and HEPES (4-(2hydroxyethyl)-1-piperazine-ethanesulfonic acid) or PIPES (1,4-pipera-zinediethanesulfonic acid) as a buffer.…”

“…Dissimilatory iron-reducing bacteria (DIRB) are ubiquitous and important for the fate of metals and organic matter in diverse natural environments. , These organisms have the capability of using ferric ions as electron acceptors and organic compounds or H 2 as electron donors to produce dissolved ferrous ions, which often result in the extracellular formation of ferrous minerals (e.g., siderite (FeCO 3 ) and vivianite (Fe 3 (PO 4 ) 2 ·8H 2 O)) or mixed-valence iron minerals (e.g., magnetite (Fe 3 O 4 ) and green rust ([Fe­(II) 1– x Fe­(III) x (OH) 2 ] x +. [( x / n )­A n – , m H 2 O] x − )). − Such mineralization processes induced extracellularly by DIRB could affect directly and indirectly the redox cycling and mobilization of metals and the degradation of organic contaminants in modern groundwater, soil, and sediment systems. , …”

Major, Trace and Rare Earth Elements Geochemistry of Bottom Sediments in the Retiro Baixo Reservoir after the B1 Tailings Dam Rupture, Paraopeba River (Brazil)

“…The pollution of soil and water by mining deposits has negative effects on both agricultural and tourism land uses; thus, a correct environmental characterization of the affected area is important for any proposal of effective measures that could help to minimize environmental impact and concern [4][5][6][7][8][9][10][11][12][13][14][15][16]. In November 2015, an iron mining tailing dam owned by Samarco Company collapsed in Brazil, releasing an estimated 52 million m 3 of tailings into the environment, affecting the public water supply, which was interrupted for a few weeks, to approximately 400,000 people, as well as industrial activities, electricity generation in three hydroelectric plants, fishing, tourism, and agriculture [17,18].…”

Genomic features of a multidrug-resistant and mercury-tolerant environmental Escherichia coli recovered after a mining dam disaster in South America

“…Dam rupture constitutes a disruption of nature-mediated mass transfer between geological reservoirs on Earth, inducing severe environmental damage. Specifically, anomalous enrichment of trace metals found in aquatic environments evidence this damage ( Buch et al, 2020 ), contributing to the selection of environmental microbiota expressing tolerance to hazardous heavy metals ( Keim et al, 2021 ). In addition, contamination by dam disaster tailings has increased the amount and abundance of antimicrobial resistance genes in the environment ( Furlan et al, 2020 ).…”