Assessment of heavy metals in a soil contaminated by oil spill: a case study in Nigeria

Abstract

Abstract Surface and subsurface soil samples contaminated with crude oils were collected from an impacted site at Bodo City in the Niger Delta, Nigeria, after a field reconnaissance survey. An uncontaminated soil sample collected 100 m from the impacted site, but within the same geographical area, was used as a control. Trace elements such as, As, Cu, Cr, Cd, Fe, Pb, Ba, Ni, V, Hg and cation-exchange capacity constituents of the contaminated and uncontaminated soils were determined by atomic absorption spectroscopy. Trace element concentrations were: Cu, 0.5–13.4 mg kg− 1; Cr, 0.2–0.8 mg kg− 1; Fe, 6.2–8.7 mg kg− 1; Ba 80.0–108.0 mg kg− 1; Ni, 0.6–4.8 mg kg− 1; and V, 4.0–9.4 mg kg− 1; cation-exchange capacity ranged from 43.6 to 57.2 mg kg− 1 in surface and subsurface soils. Results showed that eigenvalues for the two first principal components represent up to 49% of the total variance. A positive correlation of the first principal component with Cu, Cr and cation-exchange capacity shows pollution from oil spillage, while a positive correlation of the second principal component with Cr, Fe, V, and dissolved oxygen (DO) shows both oil pollution and allochthonous inputs. Keywords: oil pollutiontoxictrace metalsallochthonousprincipal component Acknowledgements The authors are sincerely grateful to Dr Abrakasa Selegha of the Department of Petroleum Engineering Niger Delta University, Wilberforce Island Yenogoa for his advice and constructive criticism and to the multinational oil companies operating in the Niger Delta for granting us access to oil spill site.