Geochemical evaluation of bottom sediments affected by historic mining and the rupture of the Fundão dam, Brazil.
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Date
2020
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Abstract
The rupture of the Fundão dam released about 39 million m3 of tailings into the Rio Doce/Brazil. The sediment load increase in
the affected rivers has become a concern. As such, this article provides recent information about the region. In addition, based on
past studies in the region, it shows the magnitude and dynamics of the environmental impacts caused by the rupture of the dam on
the bottom sediments. Sediment samples in different seasonal periods were collected at eleven sampling stations located along the
Gualaxo do Norte River, the first tributary of the Rio Doce affected by the environmental disaster. These sediments underwent
physical, chemical, and granulometric analyses for their organic, metal, and semimetal content. The contamination factor and the
enrichment factor of the samples also were calculated. To evaluate the anthropogenic contributions to sediment metal concentrations, reference values (regional background values) for the Gualaxo do Norte River were used. The results indicate that, in the
sampling stations not affected by the disaster, the concentrations of the metals and semimetals reflect the geology of the
Quadrilátero Ferrífero. However, in the area affected by the environmental disaster, there were changes in the chemical and
physical properties of the bottom sediment, mainly in the concentrations of iron, organic matter, and fine sediment fractions. This
was reflected in the contamination factors and enrichment factors calculated for the sediments of the sampling stations. Iron and
manganese concentrations in sediments are much higher than other rivers in the world that are unaffected by mining activities.
The observed changes in the bottom sediments of the river suggest a need for constant monitoring of the iron because the iron
oxide minerals present in silt and clay have a high adsorption capacity. In the long term, these factors may contribute to the
decrease of the quality of these sediments and consequently of the waters and biota present in these environments.
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Keywords
Enrichment factor, Environmental disaster, Environmental impacts, Rio Doce, Metals/semimetals
Citation
REIS, D. A. dos et al. Geochemical evaluation of bottom sediments affected by historic mining and the rupture of the Fundão dam, Brazil. Environmental Science and Pollution Research, v. 27, p. 4365–4375, 2020. Disponível em: <https://link.springer.com/article/10.1007/s11356-019-07119-1>. Acesso em: 10 mar. 2020.