Soil Profile Quality of a Contaminated Dumpsite (Aba-Eku) in Ibadan, Nigeria

Abstract

Solid waste disposal may result in soil pollution with implications for groundwater quality. The impact of waste disposal on soil quality of the Aba-Eku dumpsite, Ibadan, Nigeria was studied at five depths in the profile. Soil samples were collected bi-monthly over a 21-month period at three sub-sites:- Waste Dump Area (WDA), Leachate Lagoon Area (LLA) 250m down-gradient of WDA; and control (600m away from WDA and LLA); using an auger and analyzed for various physico-chemical parameters. Data were analyzed using Principal Component Analysis (PCA) and ANOVA. Contamination factors were also computed using relevant formulas. Seven, five and four factors were extracted by PCA, explaining 83%, 86% and 80% variation in WDA, LLA and control respectively. Positive loadings for percent gravel (0.941) and permeability (0.596) and negative loadings from percent sand (-0.912) on the first PC for WDA suggested increases in the coarse fraction and decreases in the fine fraction were associated with moderate increases in permeability at the site. Except iron and potassium, other parameters were significantly elevated (p<0.05) in WDA profiles compared to LLA and control.  Cadmium reduced significantly (p<0.05) with depth from 23.7±5.3; (0-15cm) to 12.7±3.0 mg/kg; (75-100cm) suggestive of gradual leaching into groundwater. Zinc, copper and cadmium had contamination factors of 56.84, 21.30 and 19.29 respectively in WDA which reduced to 3.28, 3.71 and 1.09 in LLA down-gradient. Two plants, Chromoleana odorata and Pennisetum pupureum found between WDA and LLA sites may have contributed to contaminant reduction and may be exploited for further remediation of the site.