Assessment of heavy metal in domestic waters in four local government area of Osun State,Nigeria
The study determined the concentrations of lead, arsenic, cadmium, zinc and copper in domestic water samples in four Local Government Areas of Osun State, Nigeria; compared the concentrations of selected heavy metals in the water samples from two sources and also compared the results with the permissible values from two regulatory bodies: World Health Organization (WHO) and Nigeria Environmental Standard and Regulatory Enforcement Agency (NESREA).This was with a view to providing information on the quality and safety of domestic waters from wells and boreholes in the study area. Two hundred (200) water samples were collected from wells and boreholes in four Local Government Areas (LGAs) of Osun State (Ife Central, Irewole, IlaOrangun and Ejigbo). Fifty samples were collected from each Local Government Area (LGA). The grid locations of the sampling points were determined using a Global Positioning System. Ambient and water temperature and the pH were determined in situ while lead (Pb), arsenic (As), cadmium (Cd),zinc (Zn) and copper (Cu) contents were determined using Atomic Absorption Spectrophotometer (AAS). Data collected were analysed using One-way analysis of variance and the correlation matrix was also determined. The results showed that the highest mean air temperature (30.7±0.3ºC), water temperature (29.9±0.3ºC) and pH (8.67±0.3) of the borehole and well samples were recorded in water samples collected from in Ife Central LGA. Samples collected from Ila-Orangun LGA was found to have the highest mean lead concentration (21 ± 0.004 µg/L and 60 ± 0.007µg/L) for borehole and well water samples respectively. The highest copper concentrations (633 ± 0.31 µg/L) and 596 ± 0.104 µg/L) in the well and borehole water samples were also recorded in IlaOrangun LGA .Water samples collected from Ife Central and Ejigbo LGA were found to have the highest arsenic (28 ± 0.004 µg/L and 28 ± 0.002µg/L),Cadmium (173 ± 0.015 µg/L and 147 ± 0.006 µg/L) and zinc (213 ± 0.022 µg/L and 255 ± 0.008 µg/L) concentrations for the borehole and well water samples respectively. Lead (Pb) and copper (Cu) concentrations in the water samples from the two sources fell within WHO and NESREA standard limits except for water samples collected from Ila-Orangun LGA. Arsenic (As) and cadmium (Cd) concentrations recorded were low in water samples collected from Ila-Orangun, but were high in samples from the other three LGAs. However, the concentration recorded were lower than the WHO and NESREA regulatory standards. The concentration of Zn recorded in the samples also fell within WHO and NESREA standard limits in the LGAs sampled. The study concluded that although the heavy metals concentrations recorded in all the studied locations varied, however, they were within the permissible levels recommended by regulatory agencies.