Abidemi O. Omopariola^1,, Funso I. Adeniyi²

This study assessed the spatial and seasonal variations in heavy metal concentrations of groundwater sources of Ayedaade LGA. It also assessed the suitability of the investigated groundwater sources for domestic use and compared the water quality with the minimum standard of drinking water provided by the World Health Organization (WHO). Twenty-five sampling stations were established covering the three bedrock types (migmatite gneiss, biotite and undifferentiated schist) identified in the three major towns of the study area. A total of a hundred and fifty (150) water samples were collected from the stations at three monthly intervals over the period of study, and analyzed for cadmium, chromium, iron, lead, nickel, and zinc using Atomic Absorption Spectrophotometric method. The results showed that approximately 60% of the water samples could be classified as soft-moderately hard fresh water type, occurring within the range of Bromothymol Blue indicator (pH 6.0 – 7.6). The result showed that all metals investigated for were present in the water samples. None of the samples analyzed had Zn concentration above the permissible limit, while Fe concentration was above the permissible limit for drinking water by WHO in 82% of the samples. Chromium, Ni, Cd, and Pb exceeded the limit for potable water in 99.7, 91.3, 90.0 and 42.0% respectively of the samples investigated. The study concluded that the water quality fell below minimum standard of drinking water provided by WHO and hence unfit for drinking.

boreholes, contamination, groundwater, hand dug wells, heavy metal, season