Analysis and distribution of metals in the Paraopeba and the Das Velhas Rivers, Brazil

Instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS) were used to analyse water and sediment samples of the Paraopeba and the Das Velhas Rivers in the state of Minas Gerais, Brazil to assess the impact of mining activities on the water environment. Elemental concentrations of Cr, Fe, Co, Ni, Cu, As, Cs, Ba, La and Ce were measured in water and sediment samples collected in different parts of the Paraopeba River, the Betim River, one of its tributaries, and in the lake near the confluence of these two rivers. Results indicate an increase in the concentration of these polluting metals in an area of industrial discharge. Elemental concentrations of Cr, Fe, Co, As and Au were also measured in water and sediment samples in the Das Velhas River. It has been clearly demonstrated that the pollution of the Das Velhas River is associated with mining exploitation. One of its tributaries, the Itabira River, carries large concentrations of Fe and Cr, and the Agua Suja tributary is highly contaminated with As from a 20-year-old deposit known as Morro do Galo, and Au from the waste of a 160-year-old gold mine, owned by the Morro Velho Company.