Monitoring the distribution of cadmium in sediment samples from Obajana stream in North central Nigeria
The distribution of cadmium species in sediments of different depths from Obajana stream was investigated by sequential extraction procedure and flame atomic absorption spectrometric detection. Index of geoaccumulation was used to assess the level of sediment pollution and it was found not to be polluted. However, the speciation results were found to contain Cd in the order exchangeable > organic matter/sulphide > residual > carbonate bound > Fe-Mn oxide at top soil and 5 cm depths. For 10 cm, 15 cm and 25 cm depths the observed trend in Cd concentration is Fe-Mn oxide bound > exchangeable > organic matter/sulphide > residual > carbonate bound. The order of decreasing concentration of Cd at 20 cm and 30 cm is Fe-Mn oxide > exchangeable > residual > organic matter/sulphide > carbonate bound. The Cd species in the exchangeable fraction occurs mostly at the topsoil followed by 5 cm and decreases progressively as the depth is increased. Thus plants and animals that may be exposed to this environment may, as a result of bioaccumulation, have concentrations of Cd in their systems beyond the acceptable limits prescribed by world health orgnisation.
Keywords: Speciation, cadmium, pollution, sediment, geoaccummulation.
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