Impact of Open Dumpsites on Groundwater Quality along Old Ikare Road, Owo, Southwestern Nigeria

Background and Objective: Owo, a rapidly growing town in Southwestern Nigeria with a population exceeding 400,000, accommodates two tertiary institutions and a Federal Medical Center. Disposing of medical and household waste in open dumpsites raises concerns about potential groundwater contamination via leachate. This study aims to evaluate the impact of leachate on groundwater quality by analyzing physicochemical parameters in well water samples collected near the dumpsite. Materials and Methods: Fifteen water samples were collected from wells near the dumpsite, and their physicochemical parameters were analyzed. The tested parameters included electrical conductivity (E/C), Total Dissolved Solids (TDS), pH, bicarbonate, nitrate, sulfate, chloride, potassium, magnesium, sodium, and calcium. The results were compared against the safe limits recommended by the Standards Organization of Nigeria (SON) and the World Health Organization (WHO). Results: The results showed that electrical conductivity ranged from 90.8 to 410 μS/cm, total dissolved solids from 29 to 321 mg/L, pH from 5.86 to 6.89, bicarbonate from 20 to 180 mg/L, nitrate from 0.05 to 30.43 mg/L, sulfate from 1.71 to 32.11 mg/L, chloride from 5.48 to 66.21 mg/L, potassium from 0.276 to 3.699 mg/L, magnesium from 0.35 to 2.16 mg/L, sodium from 0.79 to 3.19 mg/L, and calcium from 0.56 to 3.77 mg/L. All parameters were within SON and WHO safe limits. However, samples 14 and 15, closest to the dumpsite, exhibited the highest concentrations of most cations and anions, except for sodium. This indicates localized and progressive groundwater contamination. Calcium ions were dominant, forming an alkaline environment associated with rock weathering and bedrock dissolution within the aquifers. Weak acid presence was linked to anionic facies like bicarbonate, originating from carbon dioxide dissolution in the atmosphere and soil zone. Conclusion: Groundwater near the dumpsite exhibits localized contamination due to leachate infiltration. Despite this, the water quality index suggests that the water remains fit for drinking. Continued monitoring and improved waste management are recommended to prevent further contamination.