Radiogenic Components of Limestone Samples Collected from Ewekoro SW Nigeria: Implications for Public Radiological Health Risks Assessment and Monitoring

Abstract

AIM: This research presents the radiogenic components in thirteen limestone samples from a quarry site in Ewekoro, southwestern Nigeria.
 METHODS: The distributions of natural radionuclides (238U, 232Th and 40K) in the limestone samples were determined by gamma spectroscopy using a well-type thallium-doped sodium iodide detector. Also, estimated associated radiological hazards are presented and compared with the standard threshold values.
 RESULTS: The activity concentrations for 238U, 232Th and 40K radionuclides range 18.09 ± 3.43-239.50 ± 25.74 Bqkg-1, 8.33 ± 0.83 - 360.01 ± 21.33 Bqkg-1 and 11.28 ± 0.81-735.26 ± 0.95 Bqkg-1 respectively. The radium equivalent activity concentration in the samples ranges 58.857-758.832 Bqkg-1 with samples S3, S4 and S11 values higher than the threshold limit of 370 Bqkg-1. Estimated dose rate and annual effective dose rate (AEDE) from the samples have ranges 28.754-330.917 nGyh-1 and 35.26-405.84 μSvy−1 respectively greater than the standard limit of 59 nGyh-1 and 70 μSvy−1 respectively for all samples except S9. The estimated external and internal indices are ranging 0.16 – 2.05 and 0.21 – 2.68 respectively, greater than permissible unity in some limestone samples such as S3, S4, S8, S11 and S13. Excess lifetime cancer risk was also computed using a life expectancy of 54.5 years. The results of higher radiological parameters in the limestone samples revealed that the miners have a high probability of contracting induced cancer.
 CONCLUSION: A regular check-up is recommended for the miners and staffs within the quarry site. Also, the residents within the environs should be relocated far away from the quarry site, as the particulates from the limestone rock blasting could contaminate the air in the study area.

Radiological Hazard of Limestone at Tse-Kucha Mining and Processing Site, Gboko, Nigeria

“…3 and also less than the 4694.0±366.0 and 547.0±242.0 Bq kgG 1 mean concentrations for 40 K and 238 U, respectively but higher than 0.0±32.0 mean concentration for 232 Th obtained by Ajayi et al 4 . The values obtained in this study are also seen to be less than the 212.41±0.64 and 22.97±0.20 Bq kgG 1 mean concentration for 238 U and 232 Th, respectively but higher than 151.16±0.10 Bq kgG 1 mean concentration for 40 K obtained by Fakeha et al 7 16 ), but within acceptable limits for 232 Th (except Awodugba et al 3 and Oyeyemi et al 9 ) and 40 K (except Awodugba et al 3 , Ajayi et al 4 and Najam et al 10 ). 0.01±0.00 0.01±0.00 2.62±0.15 5.00±0.28 0.00±0.00 0.02±0.00 0.02±0.00 0.019 5.6 D-700 m 7.34±0.46 0.02±0.00 0.02±0.00 3.68±0.22 7.07±0.44 0.00±0.00 0.03±0.00 0.03±0.00 0.027 8.4 E-600 m 133.56±9.58 0.36±0.03 0.46±0.04 64.53±4.50 126.19±8.93 0.08±0.01 0.62±0.00 0.71±0.01 0.469 198.8 F-500 m 11.69±0.79 0.03±0.00 0.04±0.00 5.65±0.37 11.08±0.74 0.01±0.00 0.05±0.00 0.05±0.00 0.041 14 G-400 m 102.44±6.70 0.28±0.02 0.31±0.02 50.96±3.25 98.16±6.32 0.06±0.00 0.48±0.03 0.54±0.03 0.373 151.2 H-300 m 33.33±1.86 0.09±0.01 0.09±0.01 17.56±0.98 33.67±1.87 0.02±0.00 0.17±0.01 0.19±0.01 0.13 53.2 I-200 m 14.52±0.88 0.04±0.00 0.04±0.03 7.17±0.43 13.73±0.82 0.01±0.00 0.07±0.00 0.08±0.00 0.052 22.…”

“…Comparison of mean activity concentration (Bq kgG1 ) of Radionuclides in the present study and other studies around the Qureshi et al19 values of this study are higher than the 35.86±7.06 and 5.75±2.57 Bq kgG 1 for 40 K and 232 Th mean concentrations, respectively but less than 91.30±2.33 Bq kgG1 for 238 U from a study of radionuclide pollutants in bedrocks from Southwest Nigeria 5 and also higher than 18 and 0.7 Bq kgG 1 for 40 K and 232 Th mean activity concentrations, respectively but less than 26 Bq kgG 1 for 238 U from a study of natural radioactivity in rocks of the Modane-Aussois (SE France)8 . The table also shows the comparison of the mean concentration of the present study to be much lower than 121.30±14.80 and 112.25±6.73 Bq kgG 1 values for 238 U and 232 Th, respectively estimated by Oyeyemi et al9 , but higher than 158.47±5.86 Bq kgG 1 for 40 K radionuclide. The mean concentration values from this study are also seen to be much lower than 578.43 and 51.94 Bq kgG 1 for 40 K and 238 U concentration values from Najam et al10 .…”

“…Furthermore, Malczewski and Żaba 8 evaluated the natural radioactivity in rocks of the Modane-Aussois (SE France) and reported safe activity concentrations of 18 Bq kgG 1 for 40 K, 26 Bq kgG 1 for 238 U and 0.7 Bq kgG 1 for 232 Th in limestone. Kehinde et al 9 , also assessed the radionuclides in limestone at Ewekoro, South Western Nigeria in 2019 and reported high mean concentrations for 238 U and 232 Th. The study reported mean activity concentrations of 158.47±5.86, 121.30±14.80 and 112.25±6.73 Bq kgG 1 for 40 K, 238 U and 232 Th, respectively.…”