Levels of Selected Heavy Metals in Water and Sediment of the Soku Oil Field Area of the Niger Delta, Nigeria

The concentration of heavy metals (Cd, Pb, Fe, Al and V) in surface water and sediment and their sediment enrichment factor were determined in Soku oil field area of Rivers State, Nigeria. Surface water and sediment were collected in duplicates, bimonthly from four stations from July 2017 to May 2018, upstream and downstream of the Soku oil field. The physicochemical parameters (ToC, Dissolved oxygen, salinity, pH) were measured according to standard methods. The total metal concentrations were analyzed using AANALYST 400 Perkin Elmer Atomic Absorption Spectrometer. The heavy metal mean concentrations (mg/L) in surface water were 1.95(Fe), 0.88(Al), 0.64(Pb), 0.08 (V) and 0.01(Cd), while in sediments the heavy metal concentrations (mg/kg) were 6608.63(Fe), 2.84(Pb), 2.54(Al), 2.16(Cd) and 1.90(V). All recorded values were above permissible limits for both water and sediment with the exception of Al in water. Heavy metals concentrations were generally high in the dry season depicting heavy metal pollution and suggestive of high dilutions by heavy rain fall in the wet season. Higher concentrations of heavy metals in the sediment as against the surface water were indicative of overtime pollution of the river and confirmation of the sediment as a sink for heavy metals. Enrichment factor using Fe as the reference element ranged from depletion (0.0003) to extremely significant enrichment of 137.27 in the order of Al˂V<Fe<Pb<Cd indicating a high Cd and Pb pollution, of the environment which is a potential threat to aquatic and human life. The determination of Al level in water and sediment was a first in the area. Al at the recorded pH between 6-7, may form soluble hydroxides that act as respiratory toxicant for fish.

Author(s): Olu U, Ugbomeh AP, Bob Manuel KNO and Ekweozor IKE

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