Mapping the flow pathways and contaminants transportation around a coal washing plant using the VLF-EM, Geo-electrical and IP techniques—A case study, NE Iran

Abstract

Coal washing operation is now being carried out in the Alborz-Sharghi plant, located in northeast of Iran. This can in effect create a number of environmental problems. In this research, different geophysical surveys were conducted to investigate the leachate flow pathways and time-dependent transportation of contaminants in downstream of the plant which is situated between a coal waste pile and tailings impoundments. The very low frequency survey identified the most likely contamination zones and flow pathways. Furthermore, two-dimensional resistivity models obtained by the inversion of geoelectrical data (measured with the use of a dipole–dipole array incorporating a time-laps technique) showed the contaminated plumes with low resistivity values (<1 Ω m). To carry out a time-laps technique, 2-D geoelectrical surveys were repeated at same profiles by a time interval of 6 months. The results distinguished a time-dependent movement of the plume in a lateral and longitudinal form as well as its further extension to the deeper layers towards the groundwater table. This was also verified by the results obtained by the induced polarization measurements.