Chemical, mineralogical and physical characteristics of a material accumulated on the river margin from mud flowing from the collapse of the iron ore tailings dam in Bento Rodrigues, Minas Gerais, Brazil

Abstract

The rupture of an itabirito mining tailings dam at the headwaters of the Doce River Basin (Minas Gerais and Espirito Santo, Brazil) caused the greatest environmental catastrophe of the planet Earth related to this activity. The tailings were deposited both in the bottom and on the riverside terrace of the rivers, causing silting and deep changes in the water quality and burial of the main agricultural areas of this basin. For these areas to return to pre-disaster levels, it is imperative that the material deposited on the river terraces be thoroughly characterized. The objective of this work was to characterize the material from the rupture of the Fundao dam, deposited on the river terrace of the Carmo River, a tributary of the Doce River. The material was collected at a depth of 0 to 30 cm from a tail layer about 3 meters thick deposited on the river terrace on the right bank of the Carmo River in the urban area of Barra Longa, Minas Gerais. The physical analyses included soil, particle and porosity density, chemical analyses were pH, sorption complex, organic matter, exchangeable Fe, Mn, Cu, Zn, Pb, Cd and Ni, total oxides, and mineralogical analyses were performed by X-ray diffractometer and Mossbauer spectrometry. The reject has high levels of sand and silt and a low clay content. The densities of soil and particles are high, and the porosity is low. The pH is alkaline, the levels of organic matter, plant nutrients and CEC are very low. The exchangeable heavy metals Zn, Cd, Cu, Pb and Ni are very low, and the exchangeable Mn contents of the tailings are high. The predominant total oxides of the tailings are SiO2 and Fe2O3. The most abundant minerals of the tailings are quartz and hematite. The physical, chemical, and mineralogical attributes of mine tailings restrict the restoration of native vegetation or the agricultural use of the river terraces on which it was deposited.