Accumulation of Cs-137 and Sr-90 by lettuce culture (Lactuca sativa L.) from radioactively contaminated soils of the former Semipalatinsk test site

The paper presents the study of Cs-137 and Sr-90 transfer from soils of the former technical sites of the Semipalatinsk test site to the salad culture (Lactuca sativa L.) as an example of the leaf vege-table. The factors affecting the transfer of the radionuclides from soils with a different character of radioactive contamination to the salad culture were identified under the model vegetation ex-periment conditions. The variation ranges of Cs-137 and Sr-90 transfer factors values were 2 and 1 orders of magnitude respectively. With the use of the private correlation method, it was found that the content of biologically available forms of Cs-137 and Sr-90 in the soils of the former Semipala-tinsk test site, and, consequently, accumulation of these radionuclides by the salad, depended on their nonisotopic analogs K and Ca concentration in the soil, respectively (rxy–z=-0.81; n=4, p<0.2 – for Cs-137 and gross K; rxy-z=-0.64; n=4, p<0.2 – for Sr-90). There was a moderate positive relationship between the value of Cs-137 transfer factor and physical clay content (fraction >0.01%) in the soil (ρ=0.47; n=12, p<0.05), the relationship between value of Sr-90 transfer factor and the physical clay content was weak negative (ρ=-0.3; n=11, p<0.05). The migration of Cs-137 and Sr-90 to the salad culture from the radioactively contaminated soils of the Semipalatinsk test site mainly depended on biologically available forms content of radionuclides and their non-isotopic analogs K and Ca speciation, respectively. The impact of physical clay on the accumulation of Cs-137 and Sr-90 by the salad culture was less pronounced, it could be due to the specific conditions for radioactive contamination of the soil surface in the territory of the former technical sites of the Semipalatinsk test site.