Transfer of radionuclides to plants of natural ecosystems at the Semipalatinsk Test Site.

A systematic study devoted to Cs, Sr, Am, Pu radionuclides in vegetation cover from several spots of the Semipalatinsk test site (STS) is summarised in this paper, highlighting the main findings obtained. The analysed spots are characterized by various types of radioactive contamination. Transfer factors (Tf) required for the quantitative description of the radionuclides transition from the soil to aboveground plant parts were determined, being found that, on average, the minimum Tf for all the radionuclides concerned were determined on the "Experimental Field" ground, followed by the determined ones in the "plumes" of radioactive fallout and in the conditionally "background" territories analysed. The highest transfer factors were characteristic of zones of radioactive streamflows and places of warfare radioactive agent (WRA) tests. On the other hand, ordering the radionuclide transferring factors in descending order, the following sequence was obtained: Sr Tf > Cs Tf > Pu Tf > Am Tf, with the Sr Tf, on the average, exceeding the Cs Tf by 8 times and exceeding the Pu Tf by up 16 times. Pu Tf values were up to 3 times higher than the Am Tf. The exception to the indicated radionuclide Tf descending order corresponded to places of WRA tests where Tf of radionuclides of interest by plants follows the sequence Sr > Pu > Cs.