GROUND WATER POLLUTION

The threat that groundwater is being polluted is a major environmental and health threat to society, especially around urban centres where waste disposal is not well controlled. The present research used the two-dimensional Electrical Resistivity Tomography (2D ERT) to determine potential pollution of the ground water at the Health Centre, University of Benin, Nigeria. The study was also meant to map the changes in resistivity of the subsurface and locate possible contamination areas that could be related to infiltration of the leachate. On-site measurements were obtained in two traverses in the Wenner Schlumberger array format and put into the RES2DINV software to provide resistivity sections. The resultant resistivity models presented values of between 217 Ωm and above 15,000 Ωm in the area of study. Such values outweigh the 100 Om mark normally considered as the contamination level of the leachates in the contaminated area, a fact that suggests that the groundwater was not polluted in the depth to which the test was carried out. Empirical resistivity of upper layers (07 m) were high (700 – 2700 Ωm), which was viewed as lateritic or compact sandy soils whereas generic layers (718 m) were moderate (700 – 1700 Ωm) and were regarded as sandy-clayey formations that held natural moisture. The resistivity of deeper zones (>18 m) was extremely high (>4000 Ωm) and was characterized by weathered or solidified lateritic materials and bedrock. According to the resistivity distribution, the subsurface is well-drained, dry and contains no leachate or chemical deposits. It can therefore be concluded that there is no contamination of ground water in the area under the Health Centre. The findings demonstrate the usability of 2D ERT as a simple and efficient instrument of early detection of ground water contamination and as a tool of implementing sustainable ground water protection control measures in the environmentally sensitive locations like learning and healthcare facilities.