Groundwater Quality in the Vicinity of Aba-Eku Dumpsite, Ibadan, SW Nigeria: A Detailed Report

Abstract

Groundwater contamination by landfill leachate is a recognized socio-economic and environmental problem in many countries. The Aba-Eku dumpsite was upgraded and the present study undertaken to characterize groundwater quality in the vicinity of the site to assess the effectiveness of the upgrades. Twenty three parameters were assessed in two groundwater wells (GW1 and GW2 located 600m from the site) over a twenty-month period using Inductively Coupled Plasma Spectroscopy and Ion Chromatography. Data were analyzed using t-test, ANOVA and correlation coefficients. Phosphates and nitrites were below detection limits. Suspended solids: [42.96±67.68 mg/l]; COD-[9.80±4.07mg/l]; and four metals [Pb: 0.047±0.029; Cu: 0.017±0.009; Ni: 0.012±0.011; Cr: 0.014±0.019 mg/l] were elevated in the up-gradient well GW1. However, only lead was significant (p<0.05). Fifteen parameters were elevated in GW2 down-gradient, of which nine including: pH: 8.15±0.11, dissolved solids: 241.39±62.89; magnesium: 28.25±17.52; chloride: 38.19±16.80; sulphate: 27.00±9.62 and cadmium: 0.070±0.045 mg/l were significant (p<0.05). Mean lead, GW1-0.047±0.029; GW2- 0.015±0.018; cadmium GW1-0.028±0.047; GW2-0.070±0.045 and iron GW1-0.82±0.61; GW2- 2.43±4.33 mg/l levels in both wells exceeded regulatory limits. Correlation results [GW1:TSSCOD; 0.713;p<0.01; GW2:TSS-COD:0.262] indicated that the turbid nature of GW1 reflected in higher levels of TSS appeared to be composed of organics and may have contributed to lead mobilization in this well. Zinc mobilization in both wells was strongly pH dependent [GW1: pH-Zn: -0.491;p<0.01; GW2:pH-Zn: -0.682;p<0.05]. Seasonal variations were less distinct. However, increased leachate influx into GW2 resulted in significantly elevated wet season levels of pH, nitrates, sulphates, chloride and TDS. There is urgent need for remediation in view of the health implications of these pollutants.

Key words: Groundwater, Aba-Eku dumpsite, landfill leachate, Remediation.