Water Erosion of Mine Wastes May Add Potentially Toxic Elements to the River Sediments

Mine wastes in developing countries are generally disposed of with no treatment. Dispersion of wastes is an environmental concern. This study evaluated the potentially toxic elements (PTE) pollution in sediments due to runoff, the PTE´s geo-accumulation index, enrichment factor, and contamination factor based on the total and available (DTPA-TEA-CaCl2) concentrations. Near the tailing heaps on the right river bank, high total Zn (1244-2171 mg kg^-1), Fe (89273 - 106,709 mg kg^-1), Cu (168 - 259 mg kg^-1), Cd (39 - 46 mg kg^-1), and Pb (1591 - 2337 mg kg^-1) concentrations were observed. Sediments from the river floor: Zn and Fe decreased as the distance increased (810 mg kg^-1 and 23,833 mg kg^-1, respectively); Cd and Pb were low (15 mg kg^-1 and 920 mg kg^-1). The availability index on the right bank was high for Zn (14.6%), Fe (0.9%), Cd (16.2%), and Pb (9.4%); but low in the riverbed Zn (11%), Pb (6.7%), Cd (4.7) and Fe (0.4%). There was moderate Zn and Cu geo-accumulation in the sediments, but high levels of Cd and Pb. A severe enrichment factor was observed for Zn, Cd, and Pb in the riverbed sediments. The PTE have dispersed as far as 1.5 km.