Detecting the Source of Contaminant Zones Down-Gradient of the Alborz Sharghi Coal Washing Plant Using Geo-electrical Methods, Northeastern Iran

Abstract

Environmental contamination from the Alborz Sharghi coal washing plant in northeast Iran was evaluated with geo-electrical techniques. The internal structure of a coal waste pile was first studied using one dimensional geo-electrical techniques, including a Schlumberger array. The oxidised zone had low resistivity while the unoxidised shallower and middle to deeper levels had higher resistivity. Next, the geo-electrical surveys were repeated after 6 months to investigate possible changes in the oxidation zone associated with seasonal variations. Precipitation affected the shallower levels of the pile. Two dimensional geo-electrical surveys, including a dipole–dipole array, were then conducted between the pile and tailings impoundments. Low resistivity values in the area appeared to indicate contaminated zones at depth. Again, two surveys were conducted at a 6 month interval. Results indicate the transportation of contaminants to deeper layers due to atmospheric precipitation. Considering the expansion of the contamination zones, the results of prior chemical analysis of the tailings impoundment water, and the increasing trend of the resistivity values in the deeper layers of the pile, seepage from the tailings impoundment is the most likely source of pollution in the area.