Mobilização de elementos químicos nos depósitos tecnogênicos formados a partir do rompimento da barragem de rejeitos de fundão, no Alto Rio Doce, MG

Abstract

The breaking of Fundão’s tailing’s dam in rio Doce basin, which occurred in November of 2015, is considered to be the biggest environmental (technological) disaster of the history of the country. The sudden deposal of sedimentar cargo on the bottom the valley caused the formation of thick packages of technogenic sendimentals. The handling option adopted by the managers of the disaster, “Fundação Renova”, is the maintaince of the tailings on the deposit environments. That proposal is based on a supposed chemical inertia from the material, which would keep geochemically stable as long as, it is not submitted to reduction conditions. This condition would not imply potential damage by the chemical contamination of fresh waters and groundwater. Bearing in mind, the handling option and the chemical inertia questioning, it’s main goal is to evaluate the mobilization of the chemical elements on the deposit tailings in marginal environments in the hydric corridor affected by the propositions of the handling. In order to do that study, it was selected a part of the affected hydric corridor between Fundão’s dam and Risoleta Neves UHE. Three cross sections were chosen, where they were allocated by section pair points, in total of six sample points which tailings samples were collected. Lixiviation tests were made in the tailings to verify the mobilization of the chemical elements by the contact with the percolant waters with acid and basic pH. On the measured extract, it was measured the physical- chemical parameters pH, electrical conductivity, turbidity and the biggest elements Fe, Al, Si e Mn and the trace elements As, Ba, Cd, Pb, Cu, Co, Cr, Ti, Ni, V and ZC were measured. Which indicates, in face of the measured concentrations in the leachates extracts, the preconized chemical inertia is questionable, especially if the technogenic materials are kept in reducing conditions, on a big acid environment. The sample points placed on adjacent marginal environments to the fluvial channel were those, which presented, the largest concentrations of chemical elements on the leachates. The mobilization of the observed chemical elements makes the need of debating around handling practices that best fit the naturally reducing humid areas with the potencial of providing optimal conditions to enable leaching, consedering the permanente or periodical contact with those waters.