Determination of Radioactivity and Heavy Metals Concentration in Underground Water Sources in Three Selected Local Government Areas of Benue State

The Heavy metals (Cadmium, Manganese, Copper, Nickel and Lead) concentration and activity of radionuclides (gross alpha and beta) from boreholes and surface wells in Oju, Obi and Otukpo Local Government Areas of Benue State. They were determined using Atomic Absorption Spectrometer and Proportional Counter respectively. The results obtained show that the mean concentrations of heavy metals for borehole water samples are; Cd: 0.103 mg/L; Cu: 4.749 mg/L; Mn: 7.313 mg/L; and Ni: 1.376 mg/L; and that for surface wells are; Cd: 0.092 mg/L; Cu: 10.756 mg/L; Mn: 8.011 mg/L; and Ni: 1.238 mg/L. The Pb concentration was below detection limit in both water sources. The mean activity concentration for water samples was found to be: borehole 0.041 ? 0.004 Bq/L and 0.071 ? 0.007 Bq/L; surface well: 0.022 ? 0.002 Bq/L and 0.058 ? 0.003 Bq/L for alpha and beta respectively. The values of the heavy metals concentrations are higher compared to Nigerian Standard on Drinking Water Quality (NSDWQ) (Cd: 0.003 mg/L, Cu: 2 mg/L, Pb: 0.01 mg/L, Mn: 0.4 mg/L and Ni 0.07) and World Health Organization (WHO) (Cd: 0.003 mg/L, Cu: 1 mg/L, Pb: 0.01 mg/L, Mn: 0.2 mg/L and Ni 0.02) except for Pb which was below detection limit. The results revealed that the boreholes and surface wells in the study area have become contaminated by heavy metals discharged into them. However, the measured gross alpha and beta activity were below the reference level set by WHO (0.500 Bq/L for gross alpha and 1.000 Bq/L for gross beta). Similarly, the calculated annual committed effective dose for adults and children were all below the Individual Dose Criterion (IDC) value of 0.1mSvy-1. The low alpha and beta activity concentrations in boreholes and surface wells show that there is low natural radionuclide activity of the underlying rocks in the areas. By this finding radioactivity in the water samples is not a threat to the users in the study area, however heavy metal concentrations is a problem.