Assessment of natural radioactivity levels and radiological hazard parameters of soils collected from Bulgaria–Turkey border region

The activity concentrations of naturally occuring radionuclides (226Ra, 232Th and 40K) were measured in topsoil samples collected from Bulgaria to Turkey border region. Naturally occurring radionuclide measurements were performed using high-purity germanium detector. The activity concentration of 226Ra, 232Th and 40K in soil samples was found to vary from of 12.64 ± 0.48 to 43.00 ± 1.02 Bq kg−1 with an average 23.98 ± 1.33 Bq kg−1, 22.81 ± 0.75 to 71.96 ± 1.89 Bq kg−1 with an average 42.37 ± 1.14 Bq kg−1 and 418.82 ± 8.71 to 908.33 ± 12.84 Bq kg−1 with an average 616.79 ± 9.37 Bq kg−1, respectively. The spatial distribution maps of 226Ra, 232Th and 40K were obtained. The radiological health hazard parameters such as radium equivalent activity, absorbed dose rate, annual effective dose equivalent, excess lifetime cancer risk and external hazard index were estimated based on activity concentrations of naturally occurring radionuclides. Statistical analyses were used to exhibit the distributions of obtained radiological data and correlation between them.