Geochemical Partitioning of Some Heavy Metals in Bottom Sediment of River Delimi in Jos, Nigeria

The determination of total metal content is usually insufficient to fully assess the environmental impacts of contaminated sediments. In order to differentiate metals of lithogenic from those of anthropogenic origins and assess their bioavailability and potential toxicity, detailed information on their partitioning to various geochemical fractions of the sediment is necessary. In recent times there has been alot of concern on the rate at which River Delimi ecosystem deteriorates as it passes through Jos city. This study was aimed at determining the geochemical partitioning of Cd, Cu, Pb and Zn in River Delimi sediment with a view to determining the extent to which they might be remobilized and affect the quality of the river ecosystem. The study was conducted at three sites along River Delimi and one control site at Lamingo Dam, all within Jos city. The total metals in sediment were extracted using aqua-regia. A five-step sequential extraction procedure was used to determine the partitioning of the metals into different geochemical fractions of the sediment. The metals extracted were determined using Atomic Absorption Spectrophotometer (AAS). The total metals in sediment were generally higher at the study compared to the control site. The mean values of Cd in sediment (1.330mg/kg, 1.515mg/kg, 1.301mg/kg and 0.900mg/kg) respectively for stations I, II, III and IV were all above the limit of 0.68mg/kg recommended by USEPA. Sediment samples obtained from River Delimi had more metals associated with the non-residual fractions compared to those from Lamingo Dam. The high amount of these metals recovered in non – residual fractions means that the metals are in potentially available forms and could pose a serious threat to the river ecosystem. Measures should therefore be put in place by the relevant authorities to curtail indiscriminate dumping of domestic wastes and discharge of industrials effluents into the river.