Distribution of radionuclides in surface soils, Singhbhum Shear Zone, India and associated dose

Gamma emitters were estimated in surface soils from a mineralized zone in Eastern India using high purity Germanium detector-based high resolution gamma spectrometry system. Activities of U-238, Ra-226, Th-232, U-235, Th-227, Pa-234m, Pb-210, K-40, and Cs-137 were 79 +/- 50, 81 +/- 53, 65 +/- 23, 4 +/- 2, 5 +/- 4, 92 +/- 50, 97 +/- 45, 517 +/- 201, and 4 +/- 2 Bq/kg, respectively. Most radionuclides were observed to follow log-normal distribution. The correlation between physicochemical properties of the samples, like pH, organic matter content, particle size, and moisture content were also studied. Activity ratios of Ra-226/U-238, Pb-210/Ra-226, and Th-227/U-235 indicated deviation from secular equilibrium in some samples. The associated annual effective dose ranged from 0.07 to 0.24 mSv and the mean was calculated to be 0.12 +/- 0.04 mSv for this region, indicating it to be one of normal natural background radiation.