ABSTRACT
Groundwater is the main source of drinking water and it has a vital importance in developed and developing countries. Nearly 80% of all diseases arise as a result of using unsafe and contaminated water. Dumping of solid waste in unscientific manner and discharge of sewage effluents are the main reasons for contamination of groundwater. The main dumping sites of Chennai are Perungudi, South Chennai, and Kondungaiyur, North Chennai. Perungudi dumping yard is one of the major municipal solid waste dumpsite of Chennai and started functioning since 1987. In the recent past, it is found that the site is subjected to many environmental changes. On an average 1500 ton/d waste has been dumping in open dumpsite. The precipitation seeps through the solid waste, producing contaminated water referred as leachate. Due to infiltration and normal flows of the groundwater, the leachate extends away from the dumpsite causing further contamination. The people living near the dumpsite face many problems due to contaminant groundwater source. Geochemical analyses were carried out in which it was found that the contamination is very high within half a kilometre from the dumpsite. As the groundwater flow in the area is towards east, the spread of contaminants are also towards east of the dumpsite. Several parameters such as pH, TDS, Cl- and Pb were analysed. TDS was 6780 mg/l 0.34 km and 290 mg/l at 1.5 km from the dumpsite. Hence, this project aims to detect and monitor the polluting effect of the Perungudi dumpsite on the aquifer as well as to assist in the reduction of groundwater contamination practices and suggest appropriate remedial measures which will be useful for betterment of people living near the dumpsite. Geophysical techniques of investigating the composition, structure and nature of the subsurface have reached a high degree of sophistication with the convergence of the need to investigate the earth for scientific and societal problems. The electrical resistivity technique is particularly suited for the detection of ionic impurities in groundwater owing to the Resistivity Contrast between the polluted zone and the host rock. It is faster and more economical than going through the process of drilling to the target formation. Geophysics provides spatially integrated information, which may be superior for some purposes to the point data provided by drilling. The Electrical Resistivity method provides a veritable tool for mapping the degree and the immediate subsurface vicinity. It is a fast, economic, and non-invasive method of studying ground water contamination, as well as other environmental issues and it has proved to be promising and useful as predicted. The method is not used to directly detect contaminants. Rather, it is used in the investigation of the geological environment through which the contaminants move, and in the determination of the distribution of pollutant in space and time through monitoring.
