Radioaktivnoe zagryaznenie rastitel' nosti Belarusi.

Nearly the entire territory of Belarus was exposed to radioactive contamination; more than 40000 km exp (2) (1/5 of Republic's territory) was hit by isotopes of strontium and cesium (2 Ci/km exp (2)), about 300000 ha of arable lands were "put to nought". The ecological aspects of radioactive contamination of the territory are determined by the presence of the following isotopes: I-131, Sr-90, Pu-238, 239, 240, Ce-144, Pr-144, Ru-103, 106, Zr-95, Cs-134, 137, Nb-95 etc. In 1993, some radionuclides decayed completely due to their short half-life period, and the soil radioactivity became governed by Sr-90, Pu-238, 239, 240, Ce-144, Pr-144, Ru-106, Cs-134, 137. Among them, Sr-90, Pu isotopes and Cs-137 are long-lived isotopes. During the accident, forest phytocoenoses, especially coniferous forests, suffered most severely from radioactive contamination; these played the role of natural filters on the ways of air/wind streams saturated with radioactive aerosols. Hence, the level of contaminations of meadows and plowed fields, as a rule, is less by a factor of 3 or 5 times. A direct relationship has been established between radionuclides accumulation in plants and the density of radioactive contamination of soil. In forest communities, the best accumulators of radionuclides are mushrooms, lichens and mosses. Radionuclides concentration in them is 1-2 orders of magnitude higher than in the soil. It was determined that the accumulation of Sr-90 by vegetation increases with time in connection with its increased mobility in soils. Wood plants of the upper layer (forest-forming species) accumulate considerably less radionuclides in their assimilating organs than the plants of lower layers. Monitoring of the dynamics of radionuclides accumulation in the soil and plants of meadow phytocoenoses (1986-1993) demonstrated its dependence on the level of soil contamination, its elemental composition, peculiarities of radionuclides-soil interaction which depends on soil composition, mechanical, physical and chemical properties, species peculiarities of root nutrition and biology of meadow grasses development. Of all agricultural plants, the highest level of radionuclides accumulation is characteristic of species Leguminosae (various species of Lupinus). Spring and winter crop Gramineae accumulate radionuclides 5-8 times less. Radiosensitivity of plants is species-dependent to a marked degree. It is determined by evolutionary developed characteristics of species genetic system and species ecological-biological peculiarities. The most radiosensitive are species of low ecological amplitude, high level of ploidy and apomicts, and species growing on the bound of natural distribution in marginal zones of distribution areas. But, the threat of disappearance under the constant irradiation exist only for a few species which are not dominants or codominants of communities.