Abstract
We investigated the effects of Fe-mining tailings of the Fundao dam on water quality, concerning physical and chemical parameters, aiming to infer the recovery process of the affected areas, and prospects of water quality in the coming years. Water quality data from the Gualaxo do Norte and Carmo rivers were evaluated in three moments: (i) before the dam rupture (1999–2000), (ii) 1 year after the rupture of the Fundao dam (2016), and (iii) after the implementation of recover mitigation activities (2017–2019). Concerning the variables evaluated, the mean concentrations of Fe and Mn were higher in the dry period, and increasing turbidity was detected in the rainy season. The turbidity, even after the recovery measures, peaked at 300 and 400 NTU in 2017 and 2019, respectively. The concentrations of dissolved Fe, Mn, and Cr, closely related to the tailings, decreased with rainfall by a dilution mechanism. Conversely, the concentrations of Cd, Al, Zn, and Cu increased in the rainy season, probably by greater erosion. The implementation of the recovery actions at the Gualaxo do Norte headwaters are helping to reduce the Mn and Fe concentrations and turbidity downriver, all associated with the Fe-mining tailings.
Highlights
The Minas Gerais state, in southeastern Brazil, extracted more than 406 million ton of iron ore in 2017, which represented 68% of the Brazilian Fe production (DNPM 2019), besides having 81.6% of the country's iron reserves (ANM 2019)
We investigated the effects of Fe-mining tailings of the Fundão dam on water quality, concerning physical and chemical parameters, aiming to infer the recovery process of the affected areas, and prospects of water quality in the coming years
In the present work we evaluated the water quality of the Gualaxo do Norte and Carmo rivers in the first zone, just below the Fundão dam burst
Summary
The Minas Gerais state, in southeastern Brazil, extracted more than 406 million ton of iron ore in 2017, which represented 68% of the Brazilian Fe production (DNPM 2019), besides having 81.6% of the country's iron reserves (ANM 2019). In the ‘Ore Treatment Units’; OTU-(place that allocates the residue from the plants to the tailing’s dams); consists of successive steps to concentrate iron ore, operate soon after extraction, with ore fragmentation, concentration for flotation, and drainage, in the wet procedure, as in the case of Fundão dam (Quaresma 2009). In this unit, tailings dams are the final destination of the silica rich material without market value (Ghose and Sen 2001; Srivastava et al 2001; Rao et al 2016). OTU with wet treatment of tailings are considered to have a large pollution potential, due to the presence of large volumes of disposed mot ends in dams
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