keywords: Contamination, electrical resistivity, geochemical, groundwater, open waste dumpsite
The effects of leachate percolation on groundwater contamination were investigated at Awotan open waste dumpsite using both electrical resistivity and geochemical techniques to assess the quality of hand-dug wells bordering the dumpsite for potable water. Five resistivity traverses were acquired at the dumpsite using Wennerarray with electrode separation ranging from 5 to 25 m. The DIPROWIN 4.01 software was used to process and invert the 2-D resistivity data obtained. Geochemical test was carried out on soil and water samples according to Nigeria Industrial Standard (NIS). The subsurface models of the 2-D resistivity data revealed very low resistivity values below 10 Ω m and suspected to be leachate. The plume is concentrated on the top layer regolith of the dumpsite. The extent of migration is pronounced, suggesting continuous contamination of the shallow groundwater system. The soil analysis shows that, the clay content has values between 14.1 and 19.1% interpreted as low protective capacity. The results of the geochemical analysis revealed that most parameters of groundwater samples are within the limit of Nigeria NIS. However, the concentration of lead recorded was 0.01 mg/dm3 which is exactly the permissible limit set by NIS and E. coli with higher concentrations of 0.03 cm3. The study concludes that, people living around the dumpsite are prone to heath issues since there is tendency for leadto increase overtime. It is recommended that, periodic evaluation of Water Quality Index (WQI) of water samples bordering the dumpsite should be done regularly to give information on the source of groundwater contamination and management.