Study of Heavy Metal Speciation in Sediments Impacted with Crude Oil in the Niger Delta, Nigeria

Sequential chemical extraction was used to assess trace metal speciation and availability in sediments from Abalagada-Aboh catchments in the Niger Delta that have received significant impact of crude oil spillage. The proportions of trace metals in the various geochemical fractions were variable. The result of speciation among the five geochemical fractions indicates that Cd was associated with easily exchangeable/adsorbed and carbonate fractions, Cu and Cr predominantly to organic and residual fraction, Pb was associated with Fe-Mn oxides and carbonate fractions, Ni to residual and Fe-Mn oxides, Mn was associated with Fe-Mn oxides and residual and Zn was associated with carbonate and Fe-Mn oxide fractions. The data revealed that Cd, Pb, Zn and Ni have high mobility indices and are thus relatively labile and bioavailable to aquatic flora and fauna.