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.