The Spatiotemporal Variation, Background, and Baseline Activities of Radionuclides in the Soil of Aragats Massif (Armenia)

The present study was performed to reveal the distribution patterns and spatiotemporal changes of radionuclides in the soil of the highest mountain of Armenia: Aragats Massif. In this regard, two surveys were implemented in 2016-2018 and 2021 with an altitudinal sampling strategy. The activities of radionuclides were determined by gamma spectrometry system with HPGe detector (CANBERRA). Correlation and linear regression analysis were applied to determine the dependence of radionuclides' distribution from altitude. Classical and robust statistical methods were used to assess the local background and baseline values. In two sampling profiles, the spatiotemporal variation of radionuclides was studied. A significant correlation was revealed between Cs and altitude pointing to global atmospheric migration as a primary source of Cs in Armenian environment. The predicted values of regression model revealed a 0.08-Bq/kg and 0.03-Bq/kg increase of Cs in each m on average, for the old and new survey, respectively. The assessment of background activities of NOR (naturally occurring radionuclides) enables setting the local background for Ra, Th, and  K in soils of Aragats Massif: 831.3 ± 20.2 Bq/kg and 540.6 ± 18.3 Bq/kg for  K, 85.5 ± 3.1 Bq/kg and 27.7 ± 2.6 Bq/kg for Ra, and 66.8 ± 3.2 and 46.4 ± 3.0 Bq/kg for Th, respectively, for the years of 2016-2018 and 2021. Cs baseline activity was estimated by altitude: 350 ± 3.7 Bq/kg and 108 ± 2.5 Bq/kg, respectively, for the years of 2016-2018 and 2021.