Water Quality From Gualaxo Do Norte And Carmo Rivers (Minas Gerais, Brazil) After The Fundão Dam Failure

Abstract

Mining waste is rich in trace elements, which present a high toxic potential and may represent a risk for aquatic ecosystems. The Fundão dam failure, considered the largest environmental disaster in the world, affected 663.2 km of watercourses, including Carmo and Gualaxo do Norte Rivers. The ore tail also affected the riverside communities, destroying villages, killing people and affecting the subsistence farming. To evaluate the influence of the mine tailing wave on the water quality of the Carmo and Gualaxo do Norte Rivers water samples were collected at nine points located in Barra Longa during the rainy season. Physicochemical parameters (conductivity, resistivity, EH, total dissolved solids, pH and temperature) and major, minor and trace elements concentrations (Ba, Co, Cr, Cu, Ni, Sc, Sr, V, Zn, As, Pb, Al, Fe, Mn, Ca, K, Mg and P) were evaluated and compared with previous studies and conformity limits established by a national resolution (CONAMA Resolution N°357/2005). Only conductivity, Fe and Mn presented non-conformity values according to CONAMA Resolution N°357/2005. These results may be related not only to the dam burst but also to the rainy season and non-detectable pollution sources. Furthermore, the decreased levels in the toxic elements in the rivers over time, may be related to its association with sediments in addition to their flux to the Atlantic Ocean. Thus, after nearly six years, the environmental and social impacts are still alive and the minerals dragged to the riverbed could bring cumulative effects for the entire environment what means an uncertain future to the Rio Doce Basin and adjacent coastal zone.

Has the Rio Doce “time bomb” been defused? Using a weight‐of‐evidence approach to determine sediment quality

“…Immediately following the incident, environmental impacts were documented, including increased metal concentrations in the water and sediments downstream from the dam, loss of aquatic biodiversity, fragmentation of habitats, destruction of native vegetation and areas of permanent preservation, and changes in water quality, among other impacts (Duarte et al, 2021;Escobar, 2015). However, since the initial incident, the concentrations of metals that were attributed to the tailing dam failure have generally decreased in most of the Rio Doce basin (Instituto Mineiro de Gestão das Águas [IGAM], 2020[IGAM], , 2021Nogueira et al, 2021), although some datasets have reported increased concentrations of metals in water, sediment, and biota samples from the estuarine and marine regions (Gabriel et al, 2021;Nascimento et al, 2022). Although elevated tissue concentrations of some metals have been reported in fish in samples collected three years after the dam rupture (Ferreira et al, 2020;Passos et al, 2020), water and sediment toxicities appear to be decreasing (Vergilio et al, 2021).…”