Natural radioactivity levels in topsoil from the Pearl River Delta Zone, Guangdong, China

Concentrations of the natural radionuclides ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K have been measured by γ-ray spectrometry in 796 topsoil samples from the Pearl River Delta Zone (PRDZ) of Guangdong, China. The mean concentrations for ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 140 ± 37 Bq kg⁻¹, 134 ± 41 Bq kg⁻¹, 187 ± 80 Bq kg⁻¹ and 680 ± 203 Bq kg⁻¹ dry mass, respectively. These values were all higher than the mean values in soil for China and the world. Outdoor air-absorbed dose rates, calculated from activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, ranged from 86 to 237 nGy h⁻¹, with a mean value of 165 ± 46 nGy h⁻¹. The corresponding annual outdoor effective dose rate per person was estimated to be between 0.11 and 0.29 mSv y⁻¹, with a mean value of 0.20 ± 0.06 mSv y⁻¹, which was also higher than the world mean value of 0.07 mSv y⁻¹. The radium equivalent activity (Ra_eq) and the external hazard index (I_r) resulted from the natural radionuclides in soil, were also calculated and found to vary from 230 to 676 Bq kg⁻¹ and from 0.6 to 1.8, respectively. The Ra_eq and the I_r in all the investigated regions were up to 75% higher than the set limits of 370 Bq kg⁻¹ and 1.0, respectively.     

High background radiation investigated by gamma spectrometry of the soil in the southwestern region of Cameroon

The aim of this work is to determine the radioactivity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in sub-surface (0-5 cm) soil samples collected from Awanda, Bikoué, Ngombas in the southwestern region of Cameroon, to assess their contribution to the external dose exposure relative to the United Nation Scientific Committee on Effects of Atomic Radiation (UNSCEAR) data. An HPGe p-type detector coupled to a multichannel analyzer was used to perform measurements and data processing. The activity concentrations of ²²⁶Ra varied from 0.06 ± 0.01 to 0.27 ± 0.02 kBq kg⁻¹ with a mean value of 0.13 ± 0.01 kBq kg⁻¹ wet weight. The activity concentrations of ²³²Th varied from 0.10 ± 0.01 to 0.70 ± 0.05 kBq kg⁻¹ with a mean value of 0.39 ± 0.03 kBq kg⁻¹ wet weight, and ⁴⁰K concentrations varied from 0.37 ± 0.02 to 1.53 ± 0.11 kBq kg⁻¹ with a mean value of 0.85 ± 0.07 kBq kg⁻¹ wet weight, respectively. The mean value of outdoor annual effective doses were estimated to be 0.48 mSv y⁻¹, 0.39 mSv y⁻¹ and 0.38 mSv y⁻¹ from Ngombas, Awanda and Bikoué, respectively. The studied areas can be said to have a high background radiation level.     

Evaluation of natural radioactivity in soil, sediment and water samples of Niger Delta (Biseni) flood plain lakes, Nigeria

This paper presents the findings of a baseline study undertaken to evaluate the natural radioactivity levels in soil, sediment and water samples in four flood plain lakes of the Niger Delta using a hyper pure germanium (HPGe) detector. The activity profile of radionuclides shows low activity across the study area. The mean activity level of the natural radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K is 20 ± 3, 20 ± 3 and 180 ± 50 Bq kg⁻¹, respectively. These values are well within values reported elsewhere in the country and in other countries with similar environments. The study also examined some radiation hazard indices. The mean values obtained are, 76 ± 14 Bq kg⁻¹, 30 ± 5.5 ηGy h⁻¹, 37 ± 6.8 μSv y⁻¹, 0.17 and 0.23 for Radium Equivalent Activity (Ra_eq), Absorbed Dose Rates (D), Annual Effective Dose Rates (E_ff Dose), External Hazard Index (H_ex) and Internal Hazard Index (H_in) respectively. All the health hazard indices are well below their recommended limits. The soil and sediments from the study area provide no excessive exposures for inhabitants and can be used as construction materials without posing any significant radiological threat to the population. The water is radiologically safe for domestic and industrial use. The paper recommends further studies to estimate internal and external doses from other suspected radiological sources to the population of the Biseni kingdom.