Estimation of soil characteristics based on the depth distributions of 238U, 232Th, 226Ra, 40K activity concentrations using laboratory HPGe gamma spectrometry

Identification of clay minerals and depositional environment in soil at Ben Tre Province—South Vietnam was studied in this work by using laboratory HPGe gamma spectrometry through the evaluation of 232 Th, 238 U, 226 Ra and 40 K natural radionuclide distributions in soil versus depths. The calculated values of activity concentration ranged from 2.13 ± 0.13 to 6.64 ± 0.40 ppm for 238 U, from 1.97 ± 0.12 to 4.95 ± 0.30 ppm for 226 Ra, from 8.87 ± 0.53 to 21.30 ± 1.27 ppm for 232 Th and from 0.85 ± 0.05 to 2.01 ± 0.12% for 40 K. The results showed that clay minerals at the investigated site can be divided into two major groups: montmorillonite (the Th/K ratio from 6.61 to 10.47) and kaolinite (from 12.37 to 19.79) which are in accordant with the previous studies at the investigated area.