Migration of contaminants into groundwater at a landfill site: A case study of the Avu landfill site Owerri, SE, Nigeria

The risk of groundwater pollution is regarded as the principal impact of the disposal of waste on land. In examining this problem, geophysical and geochemical studies were carried out at a solid waste disposal site in Owerri, southeastern Nigeria. The method of solid waste disposal in use is the landfill disposal method. Azimuthal electrical resistivity (ER) soundings were conducted around the site to determine the directions of contaminant transport. Surface and groundwater samples were collected and analysed to determine some geochemical parameters usually considered to be indicators of pollution from solid waste disposal. Comparative studies were made of the geochemical regime before and after the siting of the landfill. Grain size analysis of sediment samples collected at the landfill site were analysed, and found to consist of sand particles with high porosity and permeability. A collection of litho-geophysical logs of the study area gives insight about the nature of the porosity and permeability. The grain size analysis results together with the litho-geophysical logs show that contaminants/leachates can migrate through the unsaturated zone to the saturated zone into groundwater. Results indicate that the dumpsite and its management pose a threat to the health of the citizens. Surface and groundwater samples near the dumpsite are notably acidic at certain locations while the concentration of PO4 and NO3 are well above the guidelines recommended by WHO.