Geographical Features of Pollution of the Territory of Yakutia With Cesium-137

A study is made of the present-day levels of global 137Cs deposition in permafrost soils of the tundra and taiga zones of Yakutia. It is shown that the reserves of 137Cs in the soils of Yakutia vary over a significant range according to the landscape and climatic features of the territory. The largest amount of 137Cs is contained in soils of the mountain areas (Aldan Highlands and Ulakhan-Chistai Range) located in the zone with maximum average annual precipitation amount, and the smallest amount occurs in the soils of the tundra zone. It is found that the average density of soil pollution by 137Cs in the flat study areas of the territory of Yakutia has now decreased by a factor of 3 to 4 in general when compared with data of airborne gamma-ray spectrometric surveys conducted during 1968–1974 on the territory of the Yakut ASSR, due to its radioactive decay, burial, removal from the surface waters and accumulation by vegetation. It is shown that in the surveyed areas of the plains and mountains of Yakutia, the global deposition of 137Cs in soils is, on average, by a factor of 2–4 less than in the soils of Ural, Western and Southern Siberia and other territories of Russia. A correlation between the density of soil pollution by 137Cs and the atmospheric precipitation amount was revealed. The main regularities of 137Cs migration and redistribution were established in different types of soils of the areas of cryogenic landscapes associated by the runoff. In the harsh climatic conditions of Yakutia, vertical and lateral migration of 137Cs is weaker in frozen soils than in soils of the European part of Russia contaminated by radioactive cesium after the accident at the Chernobyl nuclear power plant.