Soil Profile Quality of a Contaminated Dumpsite 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 downgradient. 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