Analysis of 226Ra, 232Th and 40K in soil samples for the assessment of the average effective dose

Abstract

The activity concentrations of the natural radionuclides namely 238Ra, 232Th and 40K are measured for soil samples collected from different locations of Faridkot and Mansa districts of Punjab. HPGe detector, based on high-resolution gamma spectrometry system is used for the measurement of activity concentration. The range of activity concentrations of 226Ra, 232Th and 40K in the soil from the studied areas varies from 21.42 Bq kg-1 to 40.23 Bq kg-1 , 61.01 Bq kg-1 to 142.34 Bq kg-1 and 227.11 Bq kg-1 to 357.13 Bq kg-1 with overall mean values of 27.17 Bq kg-1, 95.22 Bq kg-1 and 312.76 Bq kg-1, respectively. Radium equivalent activities are calculated for the analyzed samples to assess the radiation hazards arising due to the use of these soil samples in the construction of dwellings. The absorbed dose rate calculated from activity concentration of 226Ra, 232Th and 40K ranges between 9.87 and 18.55, 38.01 and 88.68 and 9.40 and 14.79 nGy h-1, respectively. The total absorbed dose in the study area ranges from 61.10 nGy h-1 to 112.86 nGy h-1 with an average value of 84.80 nGy h-1. The calculated values of external hazard index (H ex ) for the soil samples of the study area range from 0.36 to 0.68. Since these values are lower than unity, according to the Radiation Protection 112 (European Commission, 1999) report, soil from these regions is safe and can be used as construction material without posing any significant radiological threat to population. The corresponding average annual effective dose for indoor and outdoor measured in the study area are 0.42 mSv and 0.10 mSv respectively.