Assessment of Dumpsite Leachate Impact on Surface and Groundwater Quality in Ile-Oluji, Ondo State, Nigeria

Abstract

Municipal dumpsites remain major sources of environmental contamination in many developing regions, particularly where open dumping practices persist. This study assessed the impact of active municipal dumpsites on groundwater and surface water quality in Ile-Oluji, Ondo State, Nigeria. Physicochemical parameters, major cations, heavy metals, and microbial indicators were analysed in surface water, groundwater, leachate, and control samples using standard analytical procedures. The Water Quality Index (WQI) and Heavy Metal Pollution Index (HPI) were employed to evaluate the suitability of the water for drinking purposes. Results showed elevated concentrations of electrical conductivity, total dissolved solids, nutrients (nitrate, nitrite, sulphate, and phosphate), and organic pollution indicators in the impacted water samples compared with the corresponding controls. Heavy metals, including Pb (0.13–0.46 mg L⁻¹), Ni (0.45–1.05 mg L⁻¹), Co (0.10–3.82 mg L⁻¹), Fe (0.65–8.07 mg L⁻¹), and Mn (0.11–2.95 mg L⁻¹), occurred at elevated concentrations in several samples, while cadmium and chromium were below detection limits in water samples but detected in leachate, indicating a potential long-term contamination risk. Microbiological analyses further confirmed faecal contamination of the affected water sources. The computed WQI values ranged from 110.15 to 300.01, indicating that all investigated surface water and groundwater samples were unsuitable for drinking. Similarly, HPI values ranged from 308.98 to 1037.67, far exceeding the critical value of 100, indicating severe heavy metal pollution across all investigated water samples. The findings demonstrate active leachate migration and progressive deterioration of surrounding water resources and underscore the urgent need for improved waste management practices, effective leachate control measures, continuous groundwater monitoring, and appropriate water treatment to safeguard public health and environmental sustainability.