Natural attenuation of acid mine drainage by various rocks in a typical Karoo coalfield:case study of the Witbank, Ermelo and Highveld coalfields, South Africa

1. Sakala1,2, F. Fourie2, M. Gomo2 and G. Madzivire1,3
2. Council for Geoscience, Pretoria, South Africa
3. Institute for Groundwater Studies, University of the Free State
4. The University of South Africa, Department of Environmental Science, 28 Pioneer Avenue, Florida Park, Roodepoort, 1709, South Africa

ABSTRACT In the Karoo coalfields, mining operations which release acid mine drainage (AMD) are threatening groundwater resources. An important parameter controlling the extent and severity of AMD impacts is the natural attenuation of rocks in response to introduced of AMD. Very little is known about such responses for Karoo rocks in saturated and unsaturated conditions, a research gap filled by this paper. Laboratory column leach experiments were used to study the responses of different rock types from Witbank, Ermelo and Highveld coalfields of South Africa. The results show that various rocks have varied responses and are a function of the quartz, plagioclase or carbonate mineral content. The presence of oxygen increased the rate of heavy metal removal from the AMD. For all rock samples under saturated and unsaturated conditions, the sulphate and chloride concentrations of the AMD remained unchanged after the leaching process, showing that these parameters are conservative and can be used as potential natural tracers of AMD movement in the subsurface. The research shows that laboratory leach tests may be used to rank the various rock types found in the Karoo coalfields in terms of their capacities to buffer the impacts of AMD. Such a ranking could inform policy and decision-makers regarding the handling and storage of AMD-generating wastes, as well as the location and design of AMD waste storage facilities.

PLEASE NOTE THAT THIS EVENT HAS REACHED CAPACITY AND WILL NOT TAKE IN MORE ATTENDEES. ADD YOUR DETAILS SHOULD YOU WISH TO BE INCLUDED IN THE AFTER-EVENT REPORT