Assessment of the level of heavy metal contamination of Ibadan inland valley bottom land and its impact on horticultural crop production.

Rivers and their valley bottom in developing countries are often subjected to various land use cover types ranging from ornamental gardens, vegetable farms, fruit orchards, industrial effluents refue dumps, and crop processing units. Soil samples from one of such rivers (River Ona in Ibadan, Nigeria)were taken from fifteen sites along the valley bottom land at two depths (o-15cm and 15-30cm)to determine the concentration of some heavy metals (lead-pb, chromium Cr, cobalt-co, and cadmium-Cd)and trace elements (iron-Fe,copper-Cu,zinc-Zn, and manganese-Mn). The results showed that though the valley bottom serves as outlets for effluents for a few industries ,it has not reached the level of heavy metal contamination but it is likely to be in danger of contamination due to the accumulation of these elements over time as dictated by the changing land use /land cover types. Also, the impact of these seemingly low levels of contamination on the production of horticultural crops and safety of the horticultural products is of great concern