A new natural background radiation area on the southwest coast of India.

The systematic study of background radiation and the distribution of radionuclides in the environment of coastal Karnataka, South India, has been initiated with an objective of establishing reliable baseline data on the background radiation level of the region for future assessment of the impact of nuclear and thermal power stations that are being set up in the region. The ambient gamma radiation survey in the environment of Mangalore, a major industrial city of coastal Karnataka, revealed significantly high gamma dose in air in certain locations of the Mangalore beach area. Thermoluminescent dosimetric studies indicated conspicuously high gamma dose in air in these places. Gamma spectrometric analyses of the soil and sand samples of this high background area have been carried out. The measured gamma dose in air in high background area is in the range 44-2102 nGy h-1. The average activity of 232Th, 238U, and 40K in soil samples is 2,971 Bq kg-1, 546 Bq kg-1, and 268 Bq kg-1, respectively. In sand samples, the respective activities are 1,842 Bq kg-1, 374 Bq kg-1, and 158 Bq kg-1. Results of these systematic investigations which establish the existence of new patches of monazite in the Mangalore beach area, on the southwest coast of India, are presented in this paper.