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

Abstract

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 automobile 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.

Lead and Cadmium Levels in Residential Soils of Lagos and Ibadan, Nigeria

“…Residual fraction (F6) metals are crystal lattice fixed, mobilize slowly and decomposition of crystal can make them available. 52 The mean fractional content of lead was 2.9–27% in Lagos and 17.1–28.3% in Ibadan and the fractional content of cadmium was 5.3–79.3% in Lagos and 18.6–42.8% in Ibadan ( Figure 2 , Figure 3 ).…”

Partitioning Of Some Trace Metals in Floodplain Soil in Onitsha, Anambra State, Nigeria.

“…The fact that total concentrations of metals should be used as a yardstick to determine the potential health risk of these metal pollutants in the environment implies that the bulk metal concentration is available to the biota. This assertion has been refuted by many authors [10,11,12,13]. It is evidence that the speciation of trace metal pollutants with the various sediment phases determines their specific impact on the environment.…”

“…This signifies that they are highly available to plants and aquatic organisms. This is call for immediate attention as a result of possible health risk to humans through the plants/aquatic organisms' uptake-dietary route [12] and do not have explicit exposure threshold for the introduction of adverse effects [20]. Cadmium has an exact toxic effect even at low concentration [21].…”

Speciation of Some Trace Metals in Floodplain Soil of Eke-Mgbom, Afikpo, Nigeria

“…Metals in this fraction exist as cement between soil particles. The metal fraction occluded in this form are known to be less soluble under oxidizing conditions but are more soluble under reducing environment with variation in redox conditions [18]. Therefore, metals in this form are thermodynamically unstable under anoxic conditions and could increase mobility with increased toxicity [10,11,12,15].…”

“…The fact that total concentrations of metals should be used as a yardstick to determine the potential health risk of these metal pollutants in the environment implies that the bulk metal concentration is available to the biota. This assertion has been refuted by many authors [13,16,17,18]. It is evidence that the speciation of trace metal pollutants with the various sediment phases determines their specific impact on the environment.…”