Study of natural radioactivity in riverbank soils along the Chao Phraya river basin in Thailand

Levels of naturally occurring radioactivity in surface soils along the Chao Phraya river have been investigated. The activity concentrations of radionuclides in the U-238 and Th-232 decay chains and from K-40 were determined through gamma-ray spectrometry measurements made using a hyperpure germanium detector in a low background configuration. Activity concentrations of U-238, Th-232 and K-40 were found to be 55.3 +/- 1.2 <-> 65.2 +/- 1.4, 60.7 +/- 1.2 <-> 69.1 +/- 1.3 and 393 +/- 13 <-> 478 +/- 16 Bq/kg, respectively. Concerning radiological risk, the absorbed gamma dose rate in air from those soils was estimated to lie in the range 81.6 +/- 1.9 <-> 90.4 +/- 2.1 nGy/h; the outdoor annual effective dose equivalent was calculated to be 100.1 +/- 2.3 <-> 110.8 +/- 2.5 mu Sv/yr. These results are compared with radioactivity measurements with world mean values. (C) 2010 Elsevier B.V. All rights reserved.