Speciation of heavy metals in inter-tidal sediments of the Okrika river system, rivers state, Nigeria

Abstract

The species and total metal concentrations of some environmentally toxic metals in inter-tidal sediments of the Okrika river system was examined. The determination of the heavy metal loadings, speciation patterns and other chemical parameters has revealed some significant correlation in inter-tidal sediments taken from the Okrika river system as it passes through Okrika. The metal concentrations (mean ± RSD in μg g-1 dry weight) were: Pb, 18.74 ± 0.08; Ni, 46.51 ± 0.70; Cd, 1.05 ± 0.78; Co, 11.41 ± 0.87; Zn, 245.49 ± 0.51; Cu, 66.70 ± 0.49. Chemical variables related to the retention of heavy metals by sediments were also measured and their average levels are % H2O (52.34), % organic matter (3.93), % CaCO3 (14.67), and % organic nitrogen (0.98). The speciation results revealed a higher environmental risk for cadmium and lead and a lesser degree for zinc due to their higher percentages in the more easily remobilize fractions.