AMD formation and dispersion of inorganic pollutants along the main stream in a mining area

The highveld coalfields area in Mpumalanga Province of South Africa is well known for the intensive mining activities focusing mostly on coal processing. The imminent impact of these activities on the water systems has been addressed by the mining companies over the years but the potential threat to the degradation of surface and ground waters quality has resurfaced (BFAP, 2012). This study aimed to quantitatively evaluate the level of mine pollution indicators in the surface water around the mining areas and particularly the implication efflorescent salt iron phase on the acidification of water. Water and efflorescent salts samples were collected along the stream from the mining areas in summer. These samples were analysed for their geochemical properties, anions and metal concentrations. High level of potentially toxic elements such as As, Cd, Co, Cu, Fe, Ni, Pb, U and Zn were detected in the main stream from mining areas that was very acidic (pH < 4) with high level of sulphate (2000 to 9000 mg/L). The efflorescent salts formed from acidic water were characterized using XRD and Mossbauer. Mikasaite, romerite, greigeite, cesanite, merwinite, maghemite, magnetite, nickelhexahydrite and thernardite were the dominant minerals in the salt samples. These results are indicative of acid mine drainage resulting from mining activities in the region. The formation of efflorescent salts near the stream with the potential to further acidify water and release metal pollutants was further indication of the presence of permanent threat to the degradation of water quality. This study highlights the potential of formation and the characteristics of a typical acid mine drainage as well as the impact of mine wastes on the quality of environmental water in the neighborhood of mining activities.