The Geochemical Properties of Rural Rivers: The case of River Oni in Efon Alaaye Area of Central Western Nigeria

Abstract

The geochemical properties of River Oni which passes close to Efon Alaaye and supplies it and nearby settlements with potable water are presented in this paper especially in view of potential pollution of the river from urban influences. The river with seasonal discharge varying from 4 l/s to 104 l/s had suspended sediment load ranging from 125 mg/l to 835 mg/l and solute load ranging from 13 mg/l to 581 mg/l. pH ranged from 6.6 to 7.5, electrical conductivity from 66.7 to 73.4 mS /cm, and alkalinity from 19 mg/l to 29 mg/l. The dominance pattern of the analysed ions was Ca²⁺ > Mg²⁺ > K₊> NO₃> PO₄-P. The first two were derived mainly from atmospheric fall out and weathered rocks, while the last three derived mainly from fertilizer residues from the farms. As the concentrations of these elements are still below the WHO safety level, there is need to prevent a decline in the river water quality.