BIOACCUMULATION OF NATURALLY OCCURING RADIONUCLIDES IN RICE AND SWEET POTATOE SAMPLES CULTIVATED IN SELECTED FARMLANDS OF KEBBI STATE, NIGERIA
ABSTRACT
This study details the bioaccumulation of natural radionuclides in rice and sweet potatoes samples acquired from selected farmlands of Kebbi State. Ten (10) samples of rice and five (5) samples of sweet potatoes were collected from (15) different farmlands in Kebbi State and analyzed by means of Gamma-rays spectroscopy using Nal(Tl) detector. Activity concentration for 238U,232Thand40K, in soil sample from the rice farms ranged from, 10.19±0.5-19.56±1.98, 13.58±0.43-32.77±3.02 and 205.32±4.73-512.25±36.51Bqkg-1respectively,with mean values of 14.42±1.31, 20.11±2.28 and 336.90±17.11Bqkg-1 accordingly. Similarly, the range of activity for soils from the sweet potatoes farms varies from 5.76±1.09-15.41±2.36, 9.28±1.34-24.28±2.34 and 220.55±7.773-
431.32±22.65Bqkg-1 respectively, with the average values of 12.32±1.7, 17.43±1.95 and 309.17±13.42Bqkg-1in accordingly for238U,232Thand40K.These values were found to be lower than the world average values of, 30, 35and 400Bq kg-1 respectively for 238U,232Thand40K in soil, provided by the United Nations Scientific Committee on the Effects of Atomic Radiation. Furthermore, the activity concentration of in rice samples ranged from 0.95±0.02-3.96±0.63, 4.73±0.15-8.65±0.77 and 60.77±1.09-125.59±2.72Bqkg-1, with the mean value of 2.81±0.21, 6.22±0.42 and 84.27±1.69Bqkg-1respectively. Similarly, the range of activity in sweet potatoes sample varies from 0.18±0.03-1.79±0.09, 1.01±0.14-5.29±0.41and 81.55±0.15-203.48±2.22Bqkg-
1respectively, with the average value of 0.93±0.06, 3.89±0.27 and 116.92±1.32Bqkg-1 respectively. The mean transfer factor (TF) for238U,232Thand40K in rice samples were 0.18, 0.33and 0.26respectively; while in sweet potatoes samples valueof TFfor238U,232Thand40K were 0.59, 0.19 and 0.32respectively. The computed TFof natural radionuclides in the crops were found to be lower than unity which signifies that the bioaccumulation of 238U,232Thand40K is insignificant. The crops considered could be thus not constitutes a source of radiotoxicity to consumers.