Forms of state and the migration of radionuclides in the soil of the East Ural radioactive trace
The authors give the results of geochemical mobility study of radionuclides in the soils of East-Ural natural reserve of the forest-steppe zone (the Chelyabinsk Region) where the so called East Ural Radioactive Trace (EURT) had been formed as a result of thermonuclear explosion of highly radioactive wastes from Mayak Production Association in 1957. It is shown that the undisturbed soil (black soil and leached gray timber) 55 years after contamination 90Sr contains mainly in mobile forms: in soluble - from 1.5 to 2.0 %, in the exchange - from 85 to 87 % of the gross content. From 10 to 12 % fall on acid-soluble form of 90Sr. Cesium-137, by contrast, is in the non-exchange form share of movable 137Cs in a gray forest soil is from 2.5 to 3.0 %, and a leached chernozem does not exceed 7.0 %. The most part of the radionuclides (>99% of total content in the soil) are concentrated in the root zone of 0-25 cm. The share of radionuclides in the lower layers is tenths of a percent of the total content. This is not observed dependence of the distribution of radionuclides in the proﬁle of the studied soils from the amount of precipitation dropped out of the twelve-year period of observation. It is noted that 55 years after plowing contaminated soil (leached chernozem) 90Sr is almost uniformly distributed in the topsoil of 0-25 cm. In subsurface horizon 90Sr share is tenths of a percent of the total content. On this basis, we can con-clude that the reduction of radionuclides (90Sr and 137Cs) in the upper layers of the soil is caused by mainly their physical decay. This information may be claimed when creating technologies of rehabilitation and remediation of contaminated areas of Primorye, referred to the former repository for spent nuclear fuel from nuclear submarines.