Natalia Viktorovna Kuzmenkova

The features of cesium-137 (137Cs) root uptake by spring oat (Avena sativa L.) and lettuce (Lactuca sativa L.) plants have been studied in a model experiment with simulation of radionuclide fallout into undisturbed monoliths of arable chernozems from the Plavsk radioactive spot. An integrated approach using digital autoradiography and γ-spectrometry methods has revealed a uniform pattern of vertical and lateral 137Cs distribution in the soil profile and low bioavailability of the radionuclide or root uptake by plants. Certain biological features of the test crops with respect to root uptake of 137Cs have been demonstrated: limited translocation of the element into shoots via its relative accumulation in roots for oats and limitation of general root uptake of 137Cs into plants, given its uniform distribution between roots and shoots for lettuce.

The study of ¹³⁷Cs and K behavior in «soil-plant» system of chernozem zone in remote period after Chernobyl accident was carried out. Experimental plots in agrosystems such as wheat, soybean, buckwheat, rapeseed, sunflower, grass mixture, and natural biosystem of a dry meadow were selected in the central part of Plavsk radioactive hotspot in Tula region. The level of ¹³⁷Cs soil contamination was 171 ± 26 kBq/m² (498 ± 100 Bq/kg). Average gross K content in soils was 2,0 ± 0,1%, including exchangeable K — 235 ± 54 mg/kg and non–exchangeable K — 816 ± 116 mg/kg. Vertical distribution of ¹³⁷Cs within contaminated 30-cm soil layer of agrosystems, as well as gross K, was uniformly accumulative, while K_ex and K_non-ex distribution was regressive and accumulative. At the same time, ¹³⁷Cs microdistribution in root zone was invariant, and gradient enrichment of soil near the root surface was shown for mobile forms of potassium. Intensity of ¹³⁷Cs transfer from soils to plants for all studied crops was 1–2 orders lower than intensity of K root uptake. Element distribution between plant organs differed. ¹³⁷Cs distribution was acropetal for Cereals and basipetal for crops from other families, and K was distributed basipetally in all tested plants.