Accumulation of Cs-137 and Sr-90 by lettuce culture from radioactively contaminated soils of the former Semipalatinsk test site

Under conditions of a simulated pot experiment in the case of salad (Lactuca sativa), quantitative parameters of Cs-137 and Sr-90 (Tf) accumulation by plants on soils from the former Semipalatinsk Test Site territory were obtained. The variation range of Tf values derived for soil samples from different STS areas was 2 orders of magnitude for Cs-137 and 1 order of magnitude for Sr-90. Using nonparametric statistical analytical techniques, determinants of the transfer of Cs-137 and Sr-90from soil to plants for STS soils with various natures of radioactive contamination were identified. The content of biologically available species of radionuclides has a significant effect on the accumulation of Cs-137 and Sr-90by salad. Values derived for Kendall correlation coefficients showed a complete functional dependence (r=1, n=4, p<0,05) between accumulation parameters and the content of biologically available species of Cs-137 and Sr-90in soil from radioactively contaminated test site areas. The use of partial correlation coefficients allowed identification of key soil contributors to the content of available speciation and, respectively, the accumulation of Cs-137 and Sr-90by the experimental crop: for 137Cs, the common content of K (rxy-z = -0,81); for Sr-90 — the common content of Ca (r xy-z = — 0,64). Findings reveal the main mechanisms of Cs-137 and Sr-90transfer from soil to plants, which are of great practical importance in the radio ecological monitoring and planning of rehabilitation measures taken in radioactively contaminated STS areas as well as in areas impacted by nuclear fuel cycle facilities (NFC) located under similar soil and climatic conditions.