HEAVY METALS MOBILITY AND BIOAVAILABILITY IN SOME SELECTED DUMPSITES OF OKENE METROPOLIS, NIGERIA

Abstract

The chemical fractionation and bioavailability of Cd, Cu, Mn, Pb and Zn in the refuse waste soils of some dumpsites in Okene metropolis were investigated. The heavy metals in the waste soils were sequentially extracted and analysed using atomic absorption spectrometry. The sites from which the samples were collected were Inike (INI), Idoji (IDO), Ammco (AAM), Lafia (LAF), Iruvucheba (IRU), Idogido (IDG), Oboroja (OBO) and Idichie (IDI). The means of total extractable metals in the samples ranged between 63.80 (INI) to 236.65 mg/kg (IDO) for Cd, 36.80 (AAM) to 312.00 mg/kg (LAF) for Cu, 192.00 (IRU) to 472.62 mg/kg (INI) for Mn, 98.30 (IDG) to 214.45 mg/kg (IRU) for Pb, and 269.35 (OBO) to 1898.15 mg/kg (IRU)for Zn. The non-residual fractions were found to be the most abundant pools for all the metals across the sites. Cadmium, Manganese and Lead were mostly found to be in the mobile phase of the samples indicating that these metals are potentially more bioavailable to the environment. This spread of metal pollution from waste dumpsites to agricultural areas can lead to health risks for human and livestock. The resulting bioaccumulation of Cadmium, Manganese and Lead can lead to damages to the liver and brain. Irreversible nervous system disorders and brain protoplasmic poisoning are typical. This study indicates that consumption of plants grown on these sites can pose health hazard to man. The observed mobility trend of the metals in this study is Cd > Mn > Pb > Cu > Zn. Key words: Heavy metals, Okene, dumpsites, mobility, bioavailability.