Spatial distribution of natural and artificial radioactivity concentrations in soil samples and statistical approach, Nevsehir, Turkey

Abstract

The concentrations of Ra-226, Th-232, K-40 and Cs-137 radionuclides in soil samples collected from 323 different regions of Nevsehir province were determined by using a gamma spectrometer with an HPGe detector. The mean gamma activity concentrations (ranges) of Ra-226, Th-232, K-40 and Cs-137 for districts were determined as 49.45 (7.40-193.90), 54.08 (<2.8-122.50), 698.43 (37.67-1370.20) and 8.26 (0.10-52.60) Bq kg(-1), respectively. The mean activity concentrations of Ra-226, Th-232 and K-40 were higher than the world mean value. According to Kolmogorov-Smirnov test, distributions of Ra-226, Th-232 and Cs-137 show log-normal distributions. Whereas, K-40 shows normal distribution. The mean radium equivalent activity was 181.68 Bq kg(-1) which is lower than the recommended maximum value of 370 Bq kg(-1) The mean external terrestrial gamma dose rate was found to be 85.12 nGy h(-1). The calculated external hazard value was 0.49 and within the acceptable limit which is less than unity (H-ex <= 1). Thermo Scientific RadEye NBR detector was used to determine environmental gamma dose rates. The gamma dose rates were measured at 445 points at a height of 1 m from land surface. The mean outdoor gamma dose rate (range) was found as 150.13 (50 -480) nGy h(-1). This mean value was found higher than world mean value. The fact that most of the Nevsehir province is based on volcanic rocks explains why the gamma dose rates are high.