Natural radioactivity levels of great soil groups in Seferihisar Geothermal Region, Turkey

In this study, measurement of natural radioactivity and analyses of physical properties of soil were carried on great soil groups around the Seferihisar Geothermal Region. The radioactivity levels in soils were analyzed using scintillation gamma spectroscopy. The activity concentrations for 226Ra, 232Th, and 40K range from 7.1 to 32.0 Bq kg−1, 15.2 to 35.9 Bq kg−1 and 223.1 to 802.2 Bq kg−1, respectively. Obtained data was compared with average values given by UNSCEAR and the other studies. The radium equivalent activity (Raeq) in soil samples ranges from 42.2 to 144.7 Bq kg−1 which are lower than the suggested maximal admissible value of 370 Bq kg−1 recommended by OECD. In addition, the value of external exposure dose has been determined from the content of natural radionuclides in soil. The absorbed dose rates change between 20.6 and 70.9 nGy h−1 with a mean value of 46.7 nGy h−1 which is lower than the global average value of 55 nGy h−1. The annual effective dose rates varied from 25.2 to 87.0 μSv year−1 with an average value of 57.3 μSv year−1. Obviously, all the calculated values were lower than this value, and therefore the environment of Tuzla Fault can be regarded as an area with normal natural background radiation.