Environmental Effect of Dredging and Geochemical Fractionation of Heavy METALS in Sediments Removed from River

Abstract

Geochemical fractionation of six heavy metals; Zn, Pb, Cd, Cu, Cr, and Ni in soil from two dredging sites at Chokocho and Umuechem communities in Etche Local Government Area of Rivers State, Nigeria, which is characterized by domestic, oil exploration and other industrial activities. The heavy metal concentration determined were 26.30 ± 0.38 mg/kg, Pb; 10.60 ± 0.04 mg/kg, Cd; 486.00 ± 1.20 mg/kg, Zn; 35.50 ± 0.30 mg/kg, Cr; 43.50 ± 0.40 mg/kg, Ni and 37.70 ± 0.10 mg/kg, Cu for Chokocho site. For Umuechem site, the concentration of the metals revealed were 18.40 ± 0.10 mg/kg, Pb; 6.80 ± 0.70 mg/kg, Cd; 437.00 ± 0.60 mg/kg, Zn; 29.30 ± 0.20 mg/kg, Cr; 36.40 ± 0.10 mg/kg, Ni; and 28.30 ± 0.20 mg/kg, Cu. Results from umuechem site was greater than Chokocho site. Heavy metal fractionation using conventional method was adopted for sequential extraction which was accomplished in five steps. Results revealed that Cd and Pb were dispersed more at exchangeable phase in the sample; Cu and Zn were the least bioavailable. Cd, Pb, and Cr show health risks because of high percent in the exchangeable or dissolved fraction. The results of the analysis also revealed that the bioavailablity and mobility of the heavy metals were in order; Cd > Pb > Cr > Ni > Zn > Cu.