The use of geoelectrical imaging to study groundwater pollution at Gemenceh waste disposal site, Negeri Sembilan

Geoelectrical imaging method is now frequently used for environmental pollution studies. The resistivity imaging surveys carried out in the present study basically measures and maps the resistivity of subsurface materials. It provides the general information on subsurface stratification of the soil and wastes and the depth to the bedrock below the lines of traverse. The survey was conducted using ABEM LUND Automatic imaging system. Groundwater that has been contaminated by leachate frequently has a significantly lower resistivity value. This paper briefly describes some preliminary results of the electrical resistivity imaging survey to assist in understanding the underground conditions and to study the groundwater pollution at Gemenceh waste disposal site in Negeri Sembilan. The geoelectrical imaging technique was used in this study to help in delineating contaminated groundwater at the disposal site. The quality and contaminated zone of the undergroundwater was determined based on the measured geoelectrical resistivity value of subsurface materials. Two dimensional resistivity profiles and subsurface geological information from both boreholes as well as seismic refraction data were used to interpret the extension and direction of the contaminant flow within the undergroundwater system in the area being studied. The contaminated zone of the groundwater aquifer gives relatively low resistivity values ofless than 10.0 ohm-m compared to that of the uncontaminated groundwater which gives resistivity values ranging from 10 to 100 ohm-m. The geoelectrical resistivity and chemical analysis of the water samples indicate that the undergroundwater aquifer in all boreholes except boreholes SPS and SP12 have been contaminated by the leachate. In comparison, the groundwater sample from borehole SP4 is highly contaminated. However the groundwater contamination in this area appears to be confined within the vacinity of the dumping ground. The resistivity profiles suggest a flow of contaminant towards north east which follows the regional trend of groundwater flow of the area.