Determination of radioactivity concentrations in soil samples and dose assessment for Rize Province, Turkey

In this study, the activity concentrations of naturally occurring ⁴⁰K, ²³⁸U, and ²³²Th radionuclides and of the artificial, Chernobyl accident-induced ¹³⁷Cs radionuclide were measured in soil samples collected from Rize Province in the Black Sea region of Turkey. Rize is a city located in the Northeastern District of Turkey, which was significantly affected by the 1986 Chernobyl nuclear reactor accident in Ukraine, and the effects have continued to today. Tea is the main production plant of the region, and was contaminated by the artificial radioactivity. Therefore, measurements of residual ¹³⁷Cs contamination in soil are critical for monitoring the potential impacts on human health. The activity concentrations of radionuclides in 24 soil samples from the study area were measured by means of gamma spectrometry with a Nal(TI) detector. The activity concentrations in soil samples varied in the range of 7.4 79.8 Bq kg^-1 for ²³⁸U, 9.5 170.8 Bq kg^-1 for ²³²Th, 35.7 913.8 Bq kg^-1 for ⁴⁰K, and 0.6 154.3 Bq kg^-1 for ¹³⁷Cs. The gamma absorbed dose rates in air were in the range of 10.7 156.4 n Gy h^-1, with an arithmetic mean of 56.9 n Gy h^-1, while the annual effective dose rates were determined to be in the range of 13.1 191.8 mSv y^-1. The calculated values of external hazard index (H_ex) for the soil sample sin the study area were in the range of 0.12 0.94. The average value of radium equivalent activity was 125.0 Bq kg^-1.The activity concentrations of radionuclides in soil samples were compared to the international values reported by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 2000)and previous studies on the area