Determination of natural radioactivity levels in soil and travertine of the region of Tokat and Sivas, Turkey

In this study, the environmental radioactivity measurements for Tokat and Sivas provinces in the northeast of Turkey were performed. Using gamma ray spectrometry, the activity concentrations of natural radionuclides in soil and travertine samples (232Th, 226Ra, and 40K) were determined. The annual effective dose equivalent, the absorbed doses rate in air, the radium equivalent, and the external hazard index were obtained from these activities. The activity concentrations vary from 9.09 to 17.04 Bq kg−1 for 232Th, from 36.53 to 76.95 Bq kg−1 for 226Ra, and from 216.56 to 576.59 Bq kg−1 for 40K in soil samples. The activity concentrations in travertines vary from 15.99 to 21.01 Bq kg−1 for 232Th, from 19.89 to 67.71 Bq kg−1 for 226Ra, and from 179.89 to 314.43 Bq kg−1 for 40K. The average dose rate in air for soil and travertine samples was 43.41 and 41.05 nGy h−1 respectively. The obtained results are presented and compared with other studies, and the results of this study are lower than the international recommended value (55 nGy h−1) given by UNSCEAR ( 2000). The results show that the region has a background radiation level within the natural limits.