Determination of ²³⁸U, ²³²Th and ⁴⁰K activity concentrations in riverbank soil along the Chao Phraya river basin in Thailand

The activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K in riverbank soil along the Chao Phraya river basin was determined through gamma-ray spectrometry measurements made using a hyper-pure germanium detector in a low background configuration. The ranges of activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K were found to be 13.9 ↔ 76.8, 12.9 ↔ 142.9 and 178.4 ↔ 810.7 Bq kg⁻¹, respectively. The anthropogenic radionuclide, ¹³⁷Cs, was not observed in statistically significant amounts above the background level in the current study. The absorbed gamma dose rate in air at 1 m above the ground surface, the outdoor annual effective dose equivalent, the values of the radium equivalent activity and the external hazard index associated with all the soil samples in the present work were evaluated. The results indicate that the radiation hazard from primordial radionuclides in all soil samples from the area studied in this current work is not significant. - Highlights: • Radioactivity in surface soils from the Chao Phraya river basin in Thailand is evaluated. • Gamma-ray spectrometric analysis is to identify decays associated with ²²⁶Ra, ²³²Th and ⁴⁰K. • The results provide baseline measurements for any changes in future radioactivity levels