Seasonal Metal Distribution in Ondo Coastal Sediment, Nigeria

The distribution of heavy metals in streambed sediment from an oil-producing region in Nigeria has been examined between the two distinct seasons (dry and wet). The highest mean concentration duringthe dry season (wet season in brackets) was 2083.3ｱ355.5 (2264.2ｱ347.3)mg/kg Cu and 0.16ｱ0.06 (0.19ｱ0.09)mg/kg Zn respectively. With similar patterns at both seasons, the order of increasing concentration was Zn Cd Ni Pb Cu. Apart from Pb, metal concentration occurred at greater concentrations during the wet season. Elevated concentration of Cu in the study was attributable to the nature of Nigerian soil. However, the impact of oil related activities within the study r egion may be contributing to the levels of other metals, particularly Pb. Significant correlations ( r = 0.05; 0.01) were record ed between some of the metals, pH and %clay in the mud fraction. Cadmium vs Ni and Cu vs Ni were both significant at both seasons. The clay fraction of the mud were significantly correlated with Pb (r = 0.949), Cd (r = 0.749) ad Ni (r = 0.869).The partition coefficient data showed that several f actors controlled the adsorption of metals unto the sediment. Comparison of sediment with guideline values indicated anthropogenic enrichment but it was considered that only Cu, and possibly Pb pose potential threats to the ecology of the area.