Transformation of sulfide minerals and metal speciation in sulfide tailings

Sulfide wastes stored in a channel of the M.Talmovaya river, have during a storage period (60 years) changed considerably from the initial structure. Chemical weathering has resulted in the formation of secondary minerals of Fe, Pb, Cu. Oxidation of sulfide minerals, metal release and their re-precipitation have caused the formation of several accumulation horizons of the mobile species: water soluble and exchangeable. Up to 40% Cd and 30% Cu in some layers are in water soluble forms. The portion of exchangeable forms is high for Zn, Cd, Cu. As a result, water and the bottom sediments of the river are considerably polluted by metals which are washed out from tailings. The excess above Maximum Allowable Concentrations is especially great for Zn and Cu, which could be considered as the most dangerous metals for the region.