Assessment of Fe, Zn, Cd, Hg, and Pb in the Jordan and Yarmouk River sediments in relation to their physicochemical propperties and sequential extraction characterization

Forty-six surface sediment samples taken along the beds of both the Jordan and Yarmouk Rivers were analysed for Pb, Cd, Zn, Fe and Hg by atomic absorption spectrophotometer. Extraction techniques were used to establish the association of the total concentrations of Pb, Cd, Zn and Fe in the sediment samples with their contents in the exchangeable, carbonate, Fe/Mn oxides, organic and residual fractions. In the sediments of the Jordan River the recorded heavy metals concentrations were as follow: 8.1 ppm for Pb, 0.63 ppm for Cd, 20.3 ppm for Zn, 6 ppm for Hg and 1265.6 ppm for Fe; whereas in the sediment of Yarmouk River were 8.4 ppm for Pb, 0.67 ppm for Cd, 26.4 ppm for Zn, 6.2 ppm for Hg and 1370 ppm for Fe. Pb, Cd, Zn, and Fe concentrations in the sediments of both rivers reflect the natural background value in shale, whereas Hg is moderately enriched. I-geo (geo-accumulation index) of metals in the sediments under study indicates that they are uncontaminated with Pb, Zn and Fe; contaminated to moderately contaminated with Cd; and strongly contaminated with Hg. Heavy metal content in the sediments were found to be significantly influenced by different physico-chemical parameters. The effect of these physico-chemical parameters can be arranged in the following order: clay fraction > organic matter fractions > carbonate fraction > silt fraction. As sequential extraction procedure shows that the total concentration of the heavy metals are largely bound to the residual phase (retained 79.5% of Pb, 38% of Cd, 54.4% of Zn and 51.6% of Fe in Jordan River Sediments; and 88.6% of Pb, 48.2% of Cd, 37.6% of Zn and 59.5% of Fe in the Yarmouk River sediments). The following sequence of mobility are suggested: Fe > Cd > Zn > Pb in Jordan River sediments, and Fe > Zn > Cd > Pb. in Yarmouk River sediments.