Seasonal Variations in Heavy Metal Status of the Calabar River, Cross River State, Nigeria

摘要

The study examined heavy metal status of the Calabar River in Cross River, Nigeria. Surface water samples were collected during the wet and dry seasons for ten months across five stations and analyzed for heavy metal parameters using standard methods. Result showed that the concentrations of iron (Fe), zinc (Zn), manganese (Mn), copper (Cu), lead (Pb) and total hydrocarbon (THC) in the dry and wet seasons were low and within WHO and FEPA tolerable limits The proportion of copper (Cr), cadmium (Cd), barium (B), nickel (Ni), vanadium (V) and mercury (M) were not detected indicating the absence of these metals in the sampled stations. The low levels of heavy metal contents across the sampled stations showed they were not polluted and as such suitable for aquatic live. Independent samples test result indicated seasonal difference in the proportion of Fe, Zn, Cu, Pb and THC (p<0.01).The study identified runoff from industrial, agricultural and residential areas as sources of heavy metal pollution in the wet season and effluent discharges from industrial and municipal wastes as major sources of pollution of the Calabar River in the dry season. To sustain the ecological status of the Calabar River, waste management practice of waste re-use through the use of retention ponds is encouraged.