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Volume 9 October 2004
ISSN 1438-7890
African Journal of Environmental Assessment and Management
Revue africaine de gestion et d’évaluation environnementales
The Ebocha-8 Oil Spillage: II. Fate of Associated Heavy Metals Six Months After

Leo C. Osuji and Chukunedum M. Onojake

Some implications of the Ebocha-8 oil pollution  on Ni, V, Pb, Cu and Cd as well as its concomitant effects on soils  were evaluated approximately six months after recorded incidence of oil spillage. Mean concentration of nickel in surface and subsurface soils of the polluted plots ( Standard Error at 95% Confidence Limit) was 12.803.20mg/kg in polluted soils and 6.90mg/kg in unpolluted soils. Copper was 5.200.68mg/kg in polluted soils and 1.90mg/kg in the control soils; lead varied from 10.0mg/kg to 10.8mg/kg in polluted plots but was 3.6mg/kg in the control site. Concentrations of vanadium and cadmium were <0.20mg/kg and showed no significant differences in polluted and control soils. While oiling might have been partly responsible for the significantly higher levels of nickel, copper and lead of the Ebocha polluted soils, the slightly lower soil-pH (i.e, slightly higher acidity), higher moisture content, mobility of metals, TOC and TOM detected in the affected soils as well as the intense rainfall and flooding that preceded the period of sampling may have also contributed in part to the enhanced concentrations of the metals. Immediate depollution measures should be effected on the affected site to avoid the possibility of  biomagnification of these metals, especially Ni and V  which are inherently persistent. On the other hand, liming of the soils with calcium and magnesium compounds may de-acidify the acidified soils by appropriately raising their pH to an acceptable range
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