Activity Concentrations of Cs-137, Sr-90, Am-241, Pu-238, and Pu-239+240 and an Assessment of Pollution Sources Based on Isotopic Ratio Calculations and the HYSPLIT Model in Tundra Landscapes (Subarctic Zone of Russia)

Abstract

The paper is devoted to the assessment of the content of anthropogenic radionuclides in tundra landscapes of the subarctic zone of Russia. The authors of the article studied the features of accumulation and migration of anthropogenic radionuclides and identified probable sources of their entry into environmental objects. Peat samples were collected on the territory of the Kaninskaya Tundra of the Nenets Autonomous Okrug (Northwest Russia). A total of 46 samples were taken. The following parameters were determined in each peat sample: (1) activity and pollution density of anthropogenic radionuclides; (2) isotopic ratios of anthropogenic radionuclides; (3) activity ratios of each radionuclide for layers 10–20 cm and 0–10 cm. The results of the studies showed that the pollution density of the Nes River basin with the radionuclides Cs-137 and Sr-90 is up to 4.85 × 103 Bq×m−2 and 1.88 × 103 Bq×m−2, respectively, which is 2–5 times higher than the available data for the Kanin tundra, as well as for Russia and the world as a whole. The data obtained for Am-241, Pu-238, and Pu-239+240 showed insignificant activity of these radionuclides and generally correspond to the values for other tundra areas in Russia and the world. It was found that some tundra areas (“peat lowlands”) are characterized by increased radionuclide content due to the process of accumulation and migration along the vertical profile. Calculations of isotope ratios Sr-90/Cs-137, Pu-238/Pu-239+240, Pu-239+240/Cs-137, Am-241/Pu-239+240 and air mass trajectories based on the HYSPLIT model showed that the main sources of anthropogenic radionuclide contamination are global atmospheric fallout and the Chernobyl accident.