Application of Direct Current Electrical Resistivity and Hydrogeochemical Methods in Investigating Groundwater Contamination: Ga East Municipal Assembly and Its Environs, Southern Ghana.

Abstract

A combined electrical resistivity and hydrogeochemical methods have been used in investigating groundwater contamination in the Ga-East municipality. Thirty five vertical electrical sounding (VES) using the Schlumberger array configuration (with a maximum of AB/2 = 500 m) and one azimuthal array resistivity sounding were conducted and analysed using the single channel Scintrex Automated Resistivity Imaging System (SARIS) and IPI2WIN software. The resistivity survey revealed mainly four geoelectric layers correlating very well with the borehole logs used in constraining the interpretation in the area. The interpreted pseudo and resistivity sections showed that the water quality at the Pantang dumpsite is contaminated and it is on a downward trend with a tendency of affecting deeper depth with time. The low resistivity signatures of the VES has positive correlation with areas of high electrical conductivity (EC) of groundwater in the study area. The analysis of trace metals revealed that only few areas were affected by the disposal of solid waste. The study also characterised the hydrochemistry of the area and assessed the suitability of groundwater for domestic and agricultural purposes. The study area was found to be characterized by the Na-Cl and Na-HCO3-water types from the piper diagram. Na+ and Ca2+ were the dominant cations whiles Cl- and HCO3- were the dominant anions detected. Sodium adsorption ratio (SAR) and hydrochemical index revealed that the groundwater around the dump site is generally unsuitable for drinking and irrigation whiles the groundwater samples from around the Legon, Pantang hospital and Ghana Atomic Energy Commission (GAEC) areas are generally good for irrigation but only about 50% are good for drinking.