The catastrophe on Chernobyl nuclear-power station was the cause of pollution of terrain of Belarus by technogenic radionuclides. The big danger to alive organisms now represents Sr–90 and Cs-137 with a half-life of 28.5 and 30 years accordingly. At present practically all radionuclides are in the upper layer of the soil and are accessible to plants on meadow land and an arable land owing to small speed of migration of radionuclides in the depth of a profile of the soil. On the majority of not processed of species of the soils sod-podzolic wetland are of 80… 90 % radionuclides in a 5-centimetric layer. The erect migration of cesium-137 and strontium - 90 on depth of an edaphic profile on not processed land is proceeded with small speed. The layer of the soil is deeper than 25 sm is characterized by a background level of a radio-activity. On the arable soils the radionuclides are distributed rather in regular intervals on all depth of a processed layer (0 - 30 sm).

The results of researches is shown, that the basic sorbents of radionuclides are:

• organic substances of soils (humic and phulvo -acids)

• colloidal part of physical clay

Absorbed radionuclides strongly kept by soil particles therefore their migration from the superficial polluted layer of soil in deeper horizons is extremely limited. Even in the conditions of washing of superficially polluted soils by rains and waters from thawed snow within several years there is no appreciable moving of radioactive pollution in a soil profile. The great bulk (mass) of radionuclides on virgin soil and on not processed soils remains in the upper layer of soil of 2-5 sm. As a rule, horizontal migration of the radionuclides on the soil surface, caused by soil blowing or carrying over of the polluted soil particles by surface water stream is insignificant. The Migration of radionuclides on a soil profile, their biological availability to plants is appreciably defined by processes of their interaction with soil. To the soil characteristics influencing behaviour of radionuclides in soil and in system soil - a plant, concern:

 Acidity,

 Base exchange capacity,

 compound of exchange cations,

 content of a humus,

 mineralogical compound.

At the same time processes of local secondary pollution are observed on account of horizontal migration of radionuclides owing to the wind and water erosion of the soils.

The content of radionuclides in the plants depends on variety of factors. The fundamental are:

1. The concentration and forms of a finding of radionuclides in a layer of soil.

2. Geochemical features of radionuclides and presence of relatives of chemical elements

3. Specific features of plants.

As a result of studying of circulation of radionuclides in nature-vegetative complexes it is possible to make the scheme of distribution of radionuclides between biogeocenosis ingredients. Soil solution destruction hot particles sorption a desorption.