The rupture of the SAMARCO Fundão dam occurred in November 2015, in Mariana, Minas Gerais, releasing approximately 50 million m³ of iron ore (Fe) tailings along the Doce river at its mouth, located in Regência, Linhares district, Espírito Santo. The tailings are mainly composed of Fe oxides that may have potentially toxic elements (PTEs) occluded or retained on the surface. Fe oxides are susceptible to changes in redox potential (Eh) that occur in estuarine environments and can make PTEs available to the environment and to humans. In vitro bioaccessibility methods are used to simulate different routes of human exposure to PTEs in the soil. Oral bioaccessibility refers to a portion of a contaminant in the soil that is soluble in the gastrointestinal system and available for transport across the cell membrane. In order to understand the dynamics of Fe oxides on oral bioaccessibility of PTEs, samples collected at 8 points distributed in the estuary of Doce river will be evaluated in two stages, 2 and 6 years after the arrival of the tailings in Regência. Bearing in mind that during the drying process in sample preparation, soil oxidation occurs, we raised the hypothesis that this procedure may affect the dynamics of oral bioaccessibility of PTEs. Based on this, the in vitro test will be performed on three sets of samples (I) kiln dried at 45 ° C and sieved at 250 µm, according to the standard procedure; (II) kiln dried at 45 ° C and sieved at 2 mm; and (III) moist samples, unchanged after collection and kept refrigerated (< 4 °C). In addition, the influence of the distribution of PTEs and Fe from the solid phase on oral bioaccessibility will be evaluated, through sequential and mineralogical extraction analyses, before and after in vitro tests.
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