Assessment of natural radioactivity and its dependence on clay minerals of the soil of Dakshina Kannada district, South India

The current study is the first in-depth investigation into the natural radioactivity in soils and assessment of associated radiological risks to the population in Dakshina Kannada district of southern India. The specific activity of natural radionuclides was determined by NaI(Tl) gamma spectroscopy. The trace minerals found in the soil were detected by FTIR spectroscopy and their relative distribution is quantified by calculating the extinction coefficient. The specific activity of Ra-226, Th-232, and K-40 range from 9.73 +/- 0.7 to 59.97 +/- 1.9 Bq kg(-1) with a mean of 26.47 +/- 1.2 Bq kg(-1), 15.88 +/- 0.8 to 78.8 5 +/- 2.1 Bq kg(-1) with a mean of 35.45 +/- 1.2 Bq kg(-1) and 147.06 +/- 3.4 to 535.92 +/- 6.7 Bq kg(-1) with a mean of 403.11 +/- 5.5 Bq kg(-1), respectively. The normality of frequency distribution curves of radionuclide concentrations was confirmed by the Kolmogorov-Smirnov test. The estimated hazard indices were found to be within acceptable levels. Higher levels of Ra-226, Th-232 and K-40 in soils were detected in certain parts of Dakshina Kannada, which was linked to the mineralogy of the region. The specific activity of radionuclides was discovered to be dependent on the minerals kaolinite and calcite. The extinction coefficients of Kaolinite, Calcite, and Quartz in soil ranged from 33.11 to 63.98, 29.63 to 111.24, and 84.47 to 115.83, respectively.