Applying in-Situ and Laboratory-based Gamma Spectrometry to Determine Activity Concentration and Distribution of 40K, 226Ra and 232Th in Abeokuta, Southwest Nigeria

The applications of radionuclides are potential sources of health risk and also a concern in the area of nuclear security. It is therefore imperative to determine the presence of the different radionuclides present in the environment at all times, because it is necessary to control and assess the risk level in the environment. The present study compares activity concentrations of the primordial radionuclides 40K, 226Ra and 232Th obtained from laboratory gamma spectrometry measurements with the activity concentrations of the radionuclides as obtained from in-situ measurements. Soil samples were randomly collected from nineteen different points within Abeokuta city ensuring good coverage of the city area. A mobile gamma spectrometry system was used to collect gamma spectra measurements in the field. The obtained values are presented. The ranges of activity concentrations for 40K, 226Ra and 232Th have been found to be 113 – 1975, 5 – 128 and 181 – 3284 Bqkg-1, respectively for laboratory gamma spectrometry and 104 – 1312, 31 – 121 and 104 – 2578 Bqkg-1, respectively for in-situ gamma spectrometry measurements. This study showed that the average activity concentrations of the primordial radionuclides in Abeokuta were much higher than worldwide averages of 400, 35 and 30 Bqkg-1 for 40K, 226Ra and 232Th, respectively. From both methods, 232Th is seen to be the major contributor to the environmental radioactivity of Abeokuta. Good correlations also were deduced between the activity concentration results obtained from laboratory and in-situ gamma spectrometry, which therefore implies a significant relationship between the two methods used in the study. Keywords: In-situ gamma, Gamma spectrometry, Activity concentration, Radionuclides.

Evaluation of Primordial Radionuclides in Ocimum gratissimum and health Risk to the Consumers at Ewekoro Southwest of Nigeria

Primordial radionuclides are transported in to the plants through the leaves and roots. Medicinal plants are widely used in Africa for prevention and treatment of diseases. Ocimum Gratissimum is medicinal plant that is so used in southwest of Nigeria due to its multifunctional traditional medicinal health uses and as spice in cooking. The research is to determine the radiological health risk of these primordial radionuclides to the consumers of Ocimum Gratissimum in the study area. Fresh leaves of the medicinal plant were plucked from ten (10) different locations at Ewekoro where mining of limestone had been taking place in Ogun State, southwest of Nigeria, been the part of the plant that was commonly used. The concentrations of 40K, 238U and 232Th in the fresh leaves were determined using gamma spectrometry method, and average annual committed effective dose to the adult consumers was determined. No artificial radionuclide was detected. The highest annual committed effective doses of 40K, 238U and 232Th to the consumers of Ocimum Gratissimum were obtained to be 0.00133mSvy-1, 0.00147mSvy-1 and 0.00336mSvy-1 respectively. The highest excess lifetime cancer risk of 40K, 238U and 232Th to the consumers were calculated to be 0.0211 x 10-3, 0.0136 x 10-3 and 0.1434 x 10-3 respectively. The average annual committed effective dose and average excess lifetime cancer risk of the radionuclides to the consumers were calculated to be 0.0109mSvy-1 and 0.0379 x 10-3 respectively. The values were below the limits of 0.3mSvy-1 and 0.29 x 10-3 respectively, recommended globally. The consumers of the medicinal plant do not have significant radiological health risk. Furthermore, the results obtained can serve as reference data for future studies in the study area and its environs. Keywords: Primordial Radionuclide, Medicinal plant, Dose, Cancer