Activity concentration and transfer of 226Ra, 232Th, and 40K from soil-to-crops in Irele Local Government Area of Ondo State, Southwestern Nigeria

Abstract

The activity concentration of radionuclides in soil and crop samples obtained from Irele local government area in Ondo State, Southwestern Nigeria, was evaluated using a 760 mm x 760 mm NaI(Tl) gamma-ray detector system of model 8075, and resolution of 8 % at 0.662 MeV line of 137Cs. In addition, the radionuclide transfer from soil to crops was determined as a result. In soil samples, the mean activity concentrations of 226Ra, 232Th, and 40K were (21.81 ± 3.32, 12.10 ± 4.13, 381.02 ± 11.87Bqkg−1); (31.26 ± 3.98, 15.20 ± 3.82, 357.46 ± 14.62Bqkg−1); (29.81 ± 2.43, 18.86 ± 2.34, 504.25 ± 20.42Bqkg−1) and (27.44 ± 3.07, 21.54 ± 3.61, 449.48 ± 16.14Bqkg−1) corresponding to plantain, maize, yam and cassava, respectively. The mean activity concentration of 226Ra, 232Th, and 40K for plantain, maize, yam and cassava samples are (13.27 ± 4.58, 6.48 ± 3.94, 265.81 ± 13.19Bqkg−1); (27.03 ± 3.70, 10.72 ± 3.07, 345.70 ± 14.63Bqkg−1); (24.03 ± 4.65, 13.79 ± 4.25, 523.53 ± 16.43Bqkg−1) and (21.47 ± 3.57, 14.44 ± 2.20, 432.99 ± 18.56Bqkg−1), respectively. The mean transfer factor values of 226Ra, 232Th and 40K are (0.611, 0.536, 0.700); (0.867, 0.708, 0.967); (0.807, 0.736, 1.040) and (0.785, 0.668, 0.974) for soil-to-plantain, soil-to-maize, soil-to-yam, and soil-to-cassava, respectively. The results revealed that the transfer factor of the crop samples is in the following order: yam>cassava>maize>plantain. The activity concentrations of 226Ra, 232Th, and 40K in the soil and crop samples and corresponding soil-to-crop transfer values did not cause radiation damage to human health as reported levels were below recommended limits. The results of this study may serve as the basis and future criteria for the radionuclide concentrations in soil and their migration factors for the various crops in the study area.