The Closing of a Mine: A Case Study of the Effectiveness of Rehabilitation Works at the Moshaneng Asbestos Mine, Botswana
A preliminary analysis of the reclamation efforts at the Moshaneng asbestos mining area in Botswana was undertaken. The study was performed in order to determine a benchmark for more detailed studies on the environmental hazard potential due to the potential presence of asbestos minerals within and outside of the former mining region. The analysis included the physical examination of the closed mining shafts, the chemical and mineralogical analysis of surface water, asbestos tailing dumps and air samples. The closing of the inclined and vertical shafts was incomplete as the potential for collapse of several of the old shafts was found. The chemical and mineralogical analysis indicated that asbestos minerals were present in the sampled surface waters, tailing dumps and air samples. Leached products (e.g., Mg and Ca) were present in the surface water, but the source of these may have been leached from non asbestiform amphiboles. The most dominant asbestos mineral found at all sites was chrysotile. A variety of minerals associated with the mining (quartz, calcite and sillimanite) were found in the tailings dumps but these minerals were not abundant in the nearby stream sediments or soils, suggesting that the vegetation surrounding the tailings dumps prevented their transport. Analysis of surface waters found high concentrations of heavy metals (Cd, Fe and Mn) that were also found in the tailings dumps. The leaching of these minerals is downgrading the water quality of nearby ponds used by domestic livestock. Analysis of air samples determined that all samples contained small amounts of asbestos fibers which are probably the greatest health risk to the local community due to the abandoned asbestos mining. Future studies should expand the number of sampled sites as well as number of locations for air, water and tailing samples analysed to further clarify the results of this study.