NATURAL RADIOACTIVITY IN THE SOIL SAMPLES OF COASTAL KARNATAKA OF SOUTH INDIA

Abstract

Studies on radiation level and radionuclide distribution in the region of Coastal Karnataka, India, were undertaken. The purpose of this study is to provide baseline data on radiation level and radionuclide distribution in the region for the future assessment of the impact of the nuclear and thermal power stations that are being set up in the region. Further, this study may reveal information on the transportation of radionuclides in the environment. The external gamma dose rates in air have been measured throughout Coastal Karnataka using a sensitive plastic scintillometer. The measured dose rates include both terrestrial and cosmic ray components. The gamma dose rates in air range from 26 to 174 nGy h(-1) with a median value of 74 nGy h(-1). The activities of naturally occurring radionuclides in the soil samples of the region were measured using HPGe gamma ray spectrometry, and the resulting doses in air were calculated. The activity of 40K varies from 61.0 to 316.7 Bq kg(-1) with a median of 117.5 Bq kg(-1); the activity of 226Ra varies from 20.1 to 62.3 Bq kg(-1) with a median value 35.0 Bq kg(-1) and that of 232Th from 14.3 to 48.6 Bq kg(-1) with a median value of 29.8 Bq kg(-1). The mean absorbed dose rate in air due to naturally occurring radionuclides is found to be 41.5 nGy h(-1). In addition to this, the correlations between 226Ra and 40K, 232Th and 40K, and 226Ra and 232Th were computed from the results of the concentration of these naturally occurring radionuclides. A weak correlation was observed between 226Ra and 40K and between 232Th and 40K while a moderately good correlation was observed between 226Ra and 232Th. The results of these systematic investigations are presented and discussed in this paper.