DefinePK

Abstract

Pollution by heavy metals deserves a special attention because of their high toxicities and persistence in aquatic environment, especially with respect to such ecosystems that receive chronic inputs of these metals. Physicochemical properties such as pH, Dissolved Oxygen DO and Biochemical Oxygen Demand BOD that can influence the availability of the metals in aquatic environment were investigated. Water, sediment and floodplain samples were digested by standard laboratory methods. Metal analyses on water, sediment and flood plain samples were carried out by Atomic Absorption Spectrophotometry AAS. On the whole, the pH of water, sediment and floodplain samples were in the range of neutrality to a little alkalinity 6.52-7.70. The Dissolved Oxygen DO for the two seasons were significantly p0.05 low in all the study sites. Biochemical Oxygen Demand BOD for Rivers Bunsuru and Gagare were also significantly p0.05 low when compared with WHO standard of 7.0 mg L-1. Rima River and Goronyo Dam had BOD p0.05 on the high side. Except for Rima River, all other rivers had Cu concentrations significantly p0.05 high. Lead Pb concentrations during the rainy season sampling from River Rima and Goronyo Dam were present above the WHO acceptable limit of 2.0 g g-1. Other mineral elements and Cd were however within the WHO limits. Significant levels of Pb in water, sediment and floodplain samples mean possible Pb toxicity to aquatic organisms and by implication man through food chain. Presence of Cd even at WHO acceptable limit is at the potential risk of bioaccumulation.