Analyses of Selected Heavy Metals and Mineral Elements in Pollution Prone Aquatic Environments of North-Western Region of Nigeria

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 (p>0.05) low in all the study sites. Biochemical Oxygen Demand (BOD) for Rivers Bunsuru and Gagare were also significantly (p>0.05) low when compared with WHO standard of 7.0 mg L-1. Rima River and Goronyo Dam had BOD (p<0.05) on the high side. Except for Rima River, all other rivers had Cu concentrations significantly (p<0.05) 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 μg 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.