Fractionation of some natural radionuclides in Albic Retisol.

In the present work, the fractionation of heavy natural radionuclides was investigated in Albic Retisol in the Moscow region of Russia. Fractionation was performed using the Pavlotskaya method. 238U and 232Тh were measured via inductively coupled plasma mass spectrometry and 226Ra was measured using an alpha-radiometer that considered the decay of Ra isotopes and accumulation of the resulting decay-related products. Results showed that the potential mobility of radionuclides during migration to adjacent environments and biological availability to plants follows the order 226Ra > 238U > 232Тh. The depletion of 226Ra in the humus horizon A was manifested as a decrease in the 226Ra/238U activity ratio to below 1 in fraction F4.1 (associated with organic matter) and fraction F4.2 (acid-soluble compounds). The profile distribution of 226Ra and 238U in the residual fraction revealed the genetic relationship between these radionuclides. Mobile compounds of 238U and 232Th leached into the lower part of the profile where they became fixed, mainly as the components of fractions associated with organic matter and crystallized iron oxides. A similar profile distribution was found for 238U, 232Тh, and Fe in the acid-soluble fraction associated with crystallized iron oxides. The results obtained herein can form the basis for regulating the mobility and bioavailability of radionuclides to ameliorate their adverse effects on plants and soil ecosystems.

[Spatial Distribution of ¹³7Cs in Soil of Spruce Forest in the Distant Zone of Chernobyl Fallout].

The vertical distribution of ¹³7Cs in Albeluvisols of the spruce forest in the Roslavl district of Smolensk region was investigated. The statistical characteristics of spatial variability and distribution laws for the activity con- centrations and activity depositions of ¹³7Cs in upper soil layers (forest litter, 0-5, 5-10, 10-19 cm) were de- termined. Positive correlations between the height, crown length of spruce trees and the content of ¹³7Cs in the soil under them were revealed. The regularities of spatial configuration of ¹³7Cs contamination in soil were related to the parcel structure of spruce forest. The lateral trends for distribution of 137Cs along the tessers un- der spruce and during the transfer to the open positions between the trees were recorded.

[Distribution of 137Cs, 90Sr and their chemical analogues in the components of an above-ground part of a pine in a quasi-equilibrium condition].

The additional study of the distribution of radioactive isotopes of caesium and strontium and their chemical analogues in the above-ground components of pine in the remote from the accident period was carried out. The results of the research confirmed the existence of analogy in the distribution of these elements on the components of this type of wood vegetation in the quasi-equilibrium (relatively radionuclides) condition. Also shown is the selective possibility of using the data on the ash content of the components of forest stands of pine and oak as an information analogue.

[The comparative analysis of 137Cs, 40K, K, 90Sr and Ca allocation in builders of an ground part of wood plants in a quasi-equilibrium condition].

The examinations of allocation of radioactive isotopes of caesium and of strontium and of their chemical analogs in a stand of forest ecosystems are carried out. By results of examinations and analysis of literary data the presence of analogy in allocation of these elements on builders in quasi-balanced (concerning radionuclides) state was confirmed. The question about the opportunity of use of data about behaviour of K and of Ca is considered at an explanation of the mechanisms of redistribution of 137Cs and of 90Sr in wood plants and for buildup of mathematical models of behaviour of datas of radionuclides in ground ecosystems.