Assessing the Impact of Leachate Infiltration from Dumpsites into the Groundwater System of Agu-Awka and Environs, Southeastern Nigeria

Abstract

This study was carried out in Agu-Akwa, Southeastern Nigeria, to investigate the impacts of leachate infiltration from dumpsites on the groundwater system using an integrated approach that combines geotechnical, geochemical, and geophysical methods. The research methodology involves a preliminary study through literature reviews, followed by integrated geotechnical, geophysical, and geochemical approaches to achieve its aim. The geotechnical analysis identifies two major soil types, sand and shale, with an average hydraulic conductivity of 0.011cm/s, ranging from 0.007 to 0.022cm/s. The soils are generally poorly graded. The interpretation of geo-electric layers reveals water-saturated sandstones and weathered shales, the primary aquifers, with average depth, thickness, resistivity, and transmissivity values of 55.01m, 26.45m, 327.09 Ωm, and 143.44m2/day, respectively. The area's aquifer protective capacity and aquifer vulnerability index were found to be poor to good and low to moderate, respectively. Hydrogeochemical analysis revealed elevated levels of pH (5.10 – 6.80), Biological Oxygen Demand (104 – 488), Chemical Oxygen Demand (23.68 – 102.08), Mercury (0.040 – 0.253mg/L), Chromium (0 – 0.321mg/L), and Arsenic (0.004 – 0.218mg/L) above permissible limits of the World Health Organization for drinking water. The result of the study reveals that areas with low hydraulic conductivity, poor aquifer protective capacity, and moderate vulnerability exhibit elevated concentrations of heavy metals, turbidity, and contaminants. This result concludes that leachate infiltration significantly affects groundwater quality in these areas, underscoring the importance of our research. Hence, sanitary landfills should be located in areas with lower aquifer vulnerability, and strict waste management and monitoring practices should be implemented to prevent groundwater contamination.