Delineation Of Concentration Of Ferruginous Minerals In Aquifers In Yenagoa, Bayelsa State, Nigeria, Using Geoelectric Vertical Electrical Sounding (Ves) And Physicochemical Techniques

A total of sixteen Vertical Electrical Sounding (VES) surveys and five physicochemical analyses were carried out in selected locations within the Yenagoa Metropolis, in Bayelsa State, Nigeria, to delineate the concentration of ferruginous minerals in freshwater aquifers in the area. For the geophysical survey, the Schlumberger electrode configuration was employed. The resulting data obtained was processed and interpreted using Excel suite, IPI2WIN resistivity, Surfer-11 and Rockworks software. The results revealed four to six geologic layers across the area, and were used to generate geoelectric maps which showed that in most part of the study area, there were uneven distributions of shallow aquifers (4 – 10m), and uneven layers of clay and sandy-silt at varying depths up to 20m. The physicochemical analysis of raw water samples collected from five boreholes located in close proximity to the VES sounding locations were analysed for physical and chemical parameters. Physical parameters tested include colour, conductivity, turbidity, and temperature. Chemical parameters analysed are pH, Dissolved Oxygen (DO), Total Dissolved Solids (TDS) Alkalinity, Total Iron, Carbonate, Chloride, Sulphate, and heavy metals such as copper, chromium, nickel, cadmium, manganese, zinc and lead. The pH was determined using a Mettler Toledo (GmbH 8603 Schwerzenbach) pH meter by direct measurement. An analogue mercury thermometer was used for temperature measurements and a Hach 2100A turbidimeter for turbidity determination. Also, the concentrations of Zinc, Lead, and Copper in the water samples were obtained using the flame atomic absorption spectrophotometer. It was observed that the values SO42- , Cl-, Na2+, Mg2+, Ca2+, F- have values below World Health Organization (WHO) standard in all boreholes tested while Mn2+, NH3, PO3−and Fe2+, K+, and Cu2+ have values above WHO standard in some boreholes. The pH values all showed that the water was slightly basic as the values all exceeded the neutral limit 7, with only station showing slightly elevated pH value 9, suggesting the presence of iron bacteria. F-, K+, Fe2+ and Mn2+ have values that exceeded the WHO standard. The results from Physicochemical and geophysical analysis suggest that at depths of 20 – 45m, the concentration of ferruginous minerals is high especially towards the north eastern section of the study area and so drilling should be made to approximate depths of 50 – 80m for minimal iron contamination in the aquifers.