Bioavailability of Some Heavy Metals in Selected Dumpsites in Ozoro, South-South, Nigeria

This study investigated the concentrations and distribution patterns of some heavy metals in soil around some waste dumpsites in Ozoro, South-South, Nigeria. Two different dumpsites located at Kwale road and Owhelogbo roads in Ozoro were used for this study. Soil samples were collected at 0 – 15cm depth. A total of two composite samples were collected for this study. The soil samples were air dried, sieved and digested. Sequential extraction was used to separate metals into their various geochemical fractions. Atomic absorption spectrophotometer (Bulk 200 model) was used to determine the metal concentrations in the various geochemical fractions. Physicochemical characteristics like pH and electrical conductivity were determined. pH result ranged from 9.6 – 10.3. The pH values were basic in both sampling sites. The conductivity result for both sites was 81.0 µS/cm. The metal concentrations ranged from 0.29 – 0.53 mg/kg for Iron; 0.22 – 0.47 mg/kg for Copper; 0.16 – 0.21 mg/kg for Cadmium; 0.28 – 0.29 mg/kg for Zinc and 0.24 – 0.27 mg/kg for Manganese. The concentration of metals in both sites is in the order Fe>Cu>Pb>Zn>Mn>Cd for Kwale road and Pb>Fe>Zn>Mn>Cu>Cd for Owhelogbo road. Bioavailability results showed zinc, copper, cadmium, manganese, and lead more associated with the exchangeable fraction for Kwale road while zinc, copper, cadmium, lead and iron were associated more to the carbonate bound fraction for Owhelogbo road. However, lead and zinc associated more with both the carbonate bound and the exchangeable fractions for both sampling sites. There were significant variations in metal concentration from both sites. The mobility factors of metals in the soil profile follows in the order: Cd>Mn>Cu>Pb>Zn>Fe.