The assessment of water quality for irrigation and sediment along Asa River

Abstract

The effects of industrial, agriculture and domestic discharges on the quality of water for irrigation along Asa River located in Ilorin were assessed. In this study, Asa river in which effluent from different industries is discharged was studied for heavy metals (Cu, Pb, Zn and Cd) to ascertain its water quality for irrigation and sediment. Water and sediment samples were collected at four points used for dry season irrigation along the river. The total concentration of Cu, Pb, Zn and Cd were analyzed using Atomic Absorption Spectrophotometer (AAS) (210/211 VAP model). The range of concentration of these metals in water were Cu (1.23 5.60)mg/l, Pb (2.20-4.10), Zn (2.60-5.11)mg/l and Cd (1.80-5.01)mg/l, while that of sediment were Cu (1.80-5.09)mg/kg, Pb (2.54-5.89)mg/kg, Zn (3.84 5.21)mg/kg and Cd (3.02-6.02)mg/kg. It was found that the metals in water and sediment were above the permissible level by FEPA(1999) and W.H.O (1996). The index of salinity hazard in water was found below the FAO (1997) standard for EC (0.04-0.29) and pH (6.0-6.3) as well as U.S Salinity (1954) level for SP (0.17-0.44) %, which showed that the water was not saline. Pyrite was prominent at location three receiving effluent from a detergent and pharmaceutical industries ladened Osere river and received by Asa River. The finding showed that the quality of Asa River water for irrigation is very poor due to the high level of heavy metals in water and sediment. Consequently, the high level of metal concentration in the study area would lead to the people dependent on this river water for domestic use including cooking, bathing, washing and even drinking or for agricultural uses like fishing and farming may be exposed to public health risks. Also, the irrigated soil by this River water would influence soil processes and soil organism induction to the soil ecosystem through a reduction in the soil microbial population and the concomitant soil nutrient transformation. Similarly, due to the high level of these metals in the soil which could be transfered to the plant tissue (vegetables), their consumption could be cancerous.

Keywords: Asa River, Heavy metals and salinity hazard, water quality and sediment pollution