Environmental Impact Assessment of Radionuclide and Metal Contamination in Heavily Urbanized River, Ibadan, Nigeria

Abstract

Naturally occurring radionuclides and other contaminants are present in drinking water, these contaminants are threats to human health. The present study measured activity concentrations of (⁴⁰K, ²²⁸Ra, and ²³²Th) and some heavy metals in Ona River, Ibadan, Southwestern Nigeria. Fifteen water samples were collected from different points at different locations along the course of the river. The activity concentrations and heavy metals were analyzed using NaI(Tl) gamma-ray spectrometer and Atomic Absorption Spectrometer (AAS). The average values for ⁴⁰K, ²²⁶Ra and ²³²Th were 21.89 Bq∙L⁻¹, 5.53 Bq∙L⁻¹, 3.87 Bq∙L⁻¹ respectively. Lifetime cancer risk obtained in the present study as compared with the world recommendation showed no elevated risk of lifetime cancer due to the ingestion of the water. The mean annual effective dose for adults in the present study was not different from the WHO standard but the mean annual effective dose value for children in the present study is two times higher than the WHO standard values. The total average effective dose for children was also higher than the world recommended value contrary to adults, estimated total dissolved solids (TDS) vary from 510 to 4609 µs/cm at 25°C, against the acceptable limit of <1500 µs/cm at 25°C. the concentration of Pb (lead) in the water samples varies from 0.001 to 0.011(mg/l) with an average of 0.00868±1.8 mg/l, Chromium (Cr) and Cadmium (Cd) concentration varies from 0.001 to 0.004 (mg/l). The result from the study indicated that Ona River is toxic and it should not be taken as a source of drinking water without due purification.