Uranium, thorium and potassium are the main terrestrial sources of radiation that are located at different levels in the soil depending on the geographical and geological conditions and contribute to increase of the natural radiation levels of the regions. In addition to the natural radiation sources, Cesium-137 which can spread from nuclear tests and accidents such as Chernobyl Nuclear Power Plant Accident is also an important artificial radiation source of that contributes to the increase of radioactivity in the soil. Determination of both natural and artificial radioactivity levels of soil is important in terms of assessing people's possible exposure to the internal radiation and ensuring that people can be protected from the harmful effects of the external radiation. In this study, on the 30th anniversary of the Chernobyl Nuclear Power Plant Accident, soil samples were collected from Rize province which was affected by the Chernobyl Nuclear Power Plant Accident in 1986 and the activity concentrations of natural and artificial radionuclides were measured and radiological hazard parameters were calculated. Radioactivity measurements were caried out with gamma spectrometry system with a high purity germanium detector. The activity concentrations were measured in range of 4.45 ± 0.39 to 32.19 ± 0.78 Bq kg-1 with an average of 17.68 ± 0.68 Bq kg-1 for 226Ra, 5.58 ± 0.65 to 43.61 ± 1.67 Bq kg-1 with an average of 22.53 ± 1.26 Bq kg-1 for 232Th, 28.82 ± 1.37 to 773.19 ± 12.14 Bq kg-1 with an average of 277.14 ± 6.24 Bq kg-1 for 40K and 1.99 ± 0.17 to 376.85 ± 2.52 Bq kg-1 with an average of 110.11 ± 0.98 Bq kg-1. The average activity concentrations of 226Ra, 232Th and 40K were found below the world median activity concentrations of 35, 30 and 400 Bq kg-1, respectively. Despite the high 137Cs activity concentrations were determined in present study compared to similar works being done in Turkey and other countries, the average activity concentration of 137Cs in investigated samples was significantly found lower than the 137Cs values in soil samples from Rize in 1990 carried out by TAEA. In present study, the average radium equivalent activity (Raeq), external hazard index (Hex) and internal hazard index (Hin) values were below the recommended limits by UNSCEAR. The average absorbed dose rate in air (D) and annual effective dose equivalent (AEDE) values were found lower than the world median values. The calculated excess lifetime cancer risk (ELCR) values for soil samples were obtained less than the precautionary limit of 0.29 × 10-3.
Keywords: Cesium; Chernobyl; Radioactivity; Rize; Soil.
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