Metal Fractionation in Soil Profiles in Umutu Oil Field, Northwest Niger Delta Nigeria

Exploitation of petroleum began recently in Umutu area, a part of the prolific Niger Delta Oil province, Nigeria. Soil profiles at six locations in this area were investigated to determine the current status of Cr, Cu, Cd, Co, Ni, Zn, Pb, Mn and Fe, and their bioavailability, in order to have reference data for future monitoring of their bioaccumulation. The procedure used sequential extraction technique. Except for the high contents of Cu, Cd, Co, Zn, and Pb in Site B (an auto-mobile mechanic waste dumpsite), mean metal levels in mgkg-1 for Umutu soils are Cd (0.65-1.83), Cu (2.20- 6.30), Pb (4.06-5.90), Cr (7.10-15.60), Ni (1.10-2.00), Zn (33.00- 45.00), Co (0.01- 0.06), Fe (1126.22- 2955.87) and Mn (1.83-18.81). Sequential extraction shows that the bioavailability of Cr except for Site E (all horizons) and Site D (0-15cm) are high. That of Fe is also high at depths of 0-15cm. Monitoring programme is herein suggested.