On the use of electrical resistivity methods in monitoring infiltration of salt fluxes in dry coal ash dumps in Mpumalanga, South Africa
Department of Earth Sciences, University of the Western Cape, Bellville, South Africa; Institute for Groundwater Studies, University of Free State, Bloemfontein, South Africa; Chemical Technologies, ESKOM, Pretoria, South Africa; Department of Applied Physics, National University of Science and Technology, Bulawayo, Zimbabwe
One of the principal environmental concerns relating to coal combustion waste disposal is the potential for groundwater contamination from salt fluxes and trace elements that may be leached into the underlying groundwater system. Since changes in moisture and salt concentrations usually provide contrasts in electrical properties against the host media, electrical resistivity methods can be used to monitor ingression of solute plumes as well as to detect any preferential flow paths within the ash medium. In this study, 2D electrical resistivity tomography was used to monitor brine (10% NaCl) water ingression through the unsaturated zone of a dry coal ash dump at Tutuka Power Station, Mpumalanga, South Africa. This was after the initial laboratory determination of the relation between electrical resistivity and moisture/salt content for the ash dump. The results showed that infiltration plume progression was more pronounced in the vertical direction, suggesting that moisture movement is mainly due to gravitational pull. There was no evidence of preferential flow within the ash medium, although the different infiltration rates for different sites suggested different permeability within the unsaturated zone.
Cementation factor; Coal combustion wastes; Electrical resistivity methods; Electrical resistivity tomography; Environmental concerns; Groundwater contamination; Laboratory determinations; Salt concentration; Coal ash; Electric conductivity; Groundwater; Groundwater flow; Moisture; Waste disposal; Infiltration; cementation; coal; electrical resistivity; groundwater pollution; infiltration; moisture; permeability; preferential flow; salt; solute; trace element; vadose zone; waste disposal; Mpumalanga; South Africa