EFFECTS OF AGRICULTURAL EFFLUENTS ON WATER QUALITY DYNAMICS OF OBINNA RIVER WATERSHED IN ADANI COMMUNITY ENUGU STATE, NIGERIA.

Abstract

Agricultural activities are the major source of nitrate and phosphate pollution of surface water. The study aims to ascertain the effects of agricultural effluents on water quality dynamics of Obinna River watershed in Adani community. Surface water was collected during wet season at up river, middle and down river. Water samples were analyzed for hardness, ammonia-nitrogen, pH, chloride, dissolved oxygen (DO), turbidity, nitrates, phosphate, chemical oxygen demand (COD), and cations bases (sodium, potassium, calcium and magnesium). The concentration of heavy metals (Fe, Cd, Cr, Pb, Cu, Zc and Ni) in water from Obinna River were analyzed using atomic absorption spectrophotometer Model VPG210. The result obtained were compared with control area, and WHO standard. The data collected for laboratory analysis were subjected to descriptive statistical analysis (Analysis of Variance Test). The result showed that most of the parameters analyzed in water fall within the permissible limit except dissolved solids, ammonia-nitrogen, turbidity and phosphate with highest overall mean value of 8.71mg/l, 13.57mg/l, 8.04NTU and 5.98mg/l respectively which exceeded WHO permissible limit of 6mg/l, 0.2mg/l, 5mg/l and 5NTU. The mean concentration of heavy metals in water from Obinna River were recorded Cd (0.05), Cr (0.06), Cu (0.03), Fe (0.37), Pb (0.14) and Zn (0.07) all in mg/l. The findings showed that Obinna River were polluted mostly due to high turbidity, dissolved solids, ammonia-nitrogen and phosphate obtained in surface water. This could lead to eutrophication due to deposits from the surface run-off emanating from the agricultural activities which includes application of inorganic fertilizer and animal manure into the farm land to promote crop yield. Therefore, the obtained result confirmed the need to keep the concentrations of physico-chemical parameters of Obinna River under control.