Evaluation of radiological hazards due to natural radioactivity in soil samples collected in and around some gold mining areas of the Mayo-Kebbi region in Chad with statistical analyses

• Published in: Arabian journal of geosciences 2023, Vol.16 (10), Article 566
• Main Authors: Samafou, Penabeï, Daniel, Bongue, Alexandre, Ngwa Ebongue, Maleka, Peane, Ajani, Mistura Bolaji, Hazou, Eyakifama, Joel, Guembou Shouop Cebastien, Dlamini, Thulani, Halawlaw, Yacoub Idriss, Godfroy, Kwato Njock Moïse
• Format: Article
• Language: English
• Subjects: Correlation; Earth and Environmental Science; Earth science; Earth Sciences; Environmental impact; Germanium; Gold; Gold mines & mining; Kaolinite; Mean; Montmorillonite; Montmorillonites; Natural radioactivity; Original Paper; Radioactivity; Radioisotopes; Radionuclide kinetics; Samples; Soil; Statistical analysis; Statistical methods; Statistics; Thorium; Thorium isotopes
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-023-11668-8

In this work, a high-purity germanium (HPGe) detector in a low-background setup was used to determine the activity concentrations of 238 U, 232 Th, and 40 K in soil samples collected in and around some gold mining areas of the Mayo-Kebbi region in Chad. Subsequently, the radiological risks due to these natural radionuclides were also assessed. The activity concentrations of 238 U, 232 Th, and 40 K varied from 1.42 ± 0.32 to 430.88 ± 7.3 Bq / kg , 1.19 ± 0.98 - 56.61 ± 1.61 Bq / kg , and 27.38 ± 2.17 – 840.51 ± 8.99 Bq/kg with average values of 29.67 ± 15.80 ( STD ) Bq / kg , 11.98 ± 2.80 ( STD ) Bq / kg , and 234.43 ± 43.28 ( STD ) Bq / kg , respectively. The highest values of 238 U, 232 Th, and 40 K concentrations were found in soil sample collected at a gold mining area of Zabili. The 232 Th/ 238 U activity ratio was consistently lower than the naturally occurring equilibrium ratio of 1.1 at the majority of the sampling sites. The assessment of the 232 Th/ 40 K mass ratio revealed the existence of montmorillonite, kaolinite, and heavy thorium-bearing minerals in the regions under investigation. The mean annual effective dose of the soil samples collected in the studied area was found to be 0.18 mSv/y. The calculated mean values of the external hazard index ( H ex ) and the internal hazard index ( H in ) of the study area were 0.18 and 0.26, respectively. Correlation studies between 238 U versus 232 Th, 40 K versus 238 U, and 40 K versus 232 Th were performed. The results showed a good correlation between the pairs ( 238 U, 232 Th); however, a weak correlation was observed between the pair ( 238 U, 40 K) and ( 232 Th, 40 K). In order to investigate the statistical variation of the data and its implications on environmental exposure, the hierarchical binary cluster tree was implemented.