Assessment of Heavy Metal Concentration around Erelu Water Dam, Oyo, South-western Nigeria

Abstract

Erelu water dam was constructed to supply quality water to Oyo town and its environs. Due to the agrarian nature of the Oyo and its environs, the dam receives inflows of anthropogenic contaminants, thereby increasing the concentration of heavy metals, which then pose threats to the water. Hence, the objective of this paper is to investigate the concentration of heavy metals around Erelu Water Dam, Oyo, Southwestern Nigeria, using appropriate standard methods, including atomic absorption spectrophotometers (AAS). The concentrations of Pb (0.008 mg/l), Cd (0.003 mg/l), As (0.006 mg/l), Ni (0.017 mg/l), Cr (0.012 mg/l), and Zn (0.035 mg/l) in treated water samples were below the permissible limit. The results of the analysis were compared with national and international standards for drinking water. The concentrations of lead, mercury, cadmium, arsenic, nickel, chromium, and zinc in all the water samples (with the exception of treated water samples) exceeded the permissible limit of the Standards Organization of Nigeria, the United States Environment Protection Agency, and the World Health Organization for drinking water. The results show a high impact of contaminants in the untreated water. Stream water and river water are not safe due to the high concentration of contaminants inflow from effluents and other industrial and anthropological activities.