Trace metals in Rio Doce sediments before and after the collapse of the Fundao iron ore tailing dam, Southeastern Brazil

The collapse of the Fundao Dam, in Southeastern Brazil, caused about 50 million m(3) of iron ore tailings to sluice down the mountain to Rio Doce, in what is considered the greatest environmental disaster in Brazilian history. The fluvial system received an intense and sudden mudflow that was transported for more than 650 km, before reaching the Atlantic Ocean. Because the area was already impacted by the mineral activities in the region, it becomes essential to evaluate the environmental conditions before the disaster to correctly assess the disaster real damage. This study compares the concentration of trace metals in the sediments of the Rio Doce alluvial plain, before and after the dam collapse, as well as the newly deposited iron ore tailings that became part of the sedimentary framework. The data indicate that the fine particles deposited have since been incorporated into the sandy river sediments. The cadmium and arsenic contents in the sediments increased to levels above the National Environment Council thresholds. The comparison between the levels of trace metals in the situations before and after disaster shows that the mining mud is the source of cadmium while the arsenic was present before the environmental disaster, and its concentration increased due to sediment remobilization. The iron ore tailings deposited on the alluvial sediments also affected the physical parameters since the formed ferruginous crusts waterproofed the ground surface and may, gradually, release toxic metals when exposed to weathering and river reworking. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The collapse of the Fundao Dam in Southeastern Brazil led to a significant environmental disaster, impacting the Rio Doce river and its surrounding areas. Large amounts of iron ore tailings flowed into the river, affecting the concentration of trace metals in the sediments. The study found an increase in cadmium and arsenic levels in sediment after the disaster, with mining mud identified as the main source of cadmium.