Assessment of Heavy Metals in a Soil Contaminated by Petroleum Hydrocarbons at Ebudu, Rivers State, Nigeria.

Abstract

<jats:p>Surface (0–15 cm) and subsurface (15–30 cm) depth of soil samples contaminated with petroleum hydrocarbons were collected from impacted sites at Ebudu community in River State, Nigeria, after a field reconnaissance survey. An uncontaminated soil sample collected 500m from the impacted sites, but within the same geographical area, was used as a control. Trace heavy metals such as, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, and Zn which are normal constituents of petroleum hydrocarbon were determined by atomic absorption spectroscopy. Trace heavy metal concentrations ( mg kg− 1) were: As, 1.00 – 4.42 mg kg− 1; Cd, 1.76 – 7.50 mg kg− 1;Cr, 1.07 – 6.38 mg kg− 1;Cu, 1.84 – 9.78 mg kg− 1; Fe, 6.64 – 24.3 mg kg− 1; Hg 1.0– 4.18 mg kg− 1; Mn, 3.42 – 13.62 mg kg− 1;Ni, 2.02 –7.26 mg kg− 1; Pb, 4.57 – 22.3 mg kg− 1; and Zn, 3.38 – 21.71 mg kg− 1; in surface and subsurface soils. A positive correlation among the heavy metal contents shows pollution is from the same source (both oil pollution and allochthonous inputs). Fe, Mn, Pb and Zn were more enhanced (p&lt;0.05) in the oil-spill-polluted soils, especially at surface depth, and this may be attributed to the fact that metal profiles in polluted soils penetrate a little below the 10-cm region, even after many years, thereby making the metal concentration in surface soils usually higher.</jats:p>