A study of chemical speciation of metals in aquatic bottom sediment of Aiba reservoir, Iwo, Nigeria

The species and total mean metal concentrations of some potentially environmental toxic metals (manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), and lead (Pb)) in the sediments of Aiba reservoir were examined. The total mean value were in the order of Fe > Mn > Zn > Cu > Pb. The metal concentrations (mean ± standard deviation (SD) in ìg/g dry weight) were Mn, 28 ± 0.88; Fe, 42.03 ± 1.11; Cu, 5.82 ± 0.21; Zn, 11.91 ± 0.37; and Pb, 0.44 ± 0.02. Some physico-chemical parameters of the bottom sediments were also measured and their average levels and range are pH, 6.2 to 6.6; conductivity, 104 ± 5 ìScm-1 (50 to 170 ìScm-1); water absorbency, 54.66 ± 2.17 (50 to 63.3). The speciation result revealed that high levels of these metals studied (Mn, Fe, Cu, Zn, and Pb) were associated with exchangeable and carbonate bound fractions, pointing out that they are in potentially available forms and may pose serious problems to the reservoir ecosystem.Key words: Bottom sediments, speciation, Aiba reservoir, metals