Geophysical survey and radiometric assessment of aquifer strata and vulnerable groundwater quality of Ukwuani Ommunities in Delta State

Abstract

The study assessed the aquifer strata and groundwater quality of Obeti, Umuaja, and Ebedei communities of Ukwuani, Delta State, Nigeria using electrical resistivity technique and sodium iodide [Na(TI)] detector. The electrical resistivity technique revealed that lithology has five to six geoelectric strata, which ranged from topsoil to clay formations with thickness of 0.6 to 6.0 m sits and aquifer resistivity range of 182.1– 6032.0 Ωm with depth of 29–70 m. These ranges indicate significant changes in the aquifer level and sufficient reservoirs for groundwater. To assess the activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K at the aquifer depth of 29–70 m groundwater, a total of fifteen groundwater samples were collect for analysis and the mean results are 9.00±1.24Bql−¹, 4.82±2.95Bql−¹ and 57.93±4.20Bql⁻¹ respectively. These results are all above world threshold limits. However, the computed mean radiological health risk values for radium equivalent (Raeq), representative index (Iy), external hazard index (Hin), internal hazard index (Hex), absorbed dose rate (D), annual effective dose equivalent (AEDE), outdoor and indoor, and excess lifetime cancer risk (ELCR) outdoor and indoor are 20.35±5.78 Bql−1, 0.15mSvy−1, 0.056mSvy−1, 0.08mSvy⁻¹, 9.55μGyh⁻¹, 11.71mSvy⁻¹, 46.84mSvy⁻¹and 0.04×10⁻³, 0.16×10⁻³ and 0.20×10⁻³ for the addition of (ELCR) outdoor and indoor respectively. The computed mean radiological values are below world threshold limits. Hence, the studied communities’ drinking groundwater is safe radiologically. It is advised that government, oil and gas operators and individuals should drill above 30 m depth for quality groundwater and should be treated before usage. These values will serve as baseline data.