Radioprotective effect of microelements at the territories contaminated by radionuclides

The most radioactively contaminated region of Ukrainian and Byelorussian Palesse belongs to a biogeochemical province where soils, plants, and, accordingly, forage for animals and food stuffs are poor with biologically important microelements - iodine, zinc, copper, cobalt, fluorine, manganese, lithium, boron. It is a cause of specific diseases of plants, animals and people known as hypomicroelementhoses. Carrying out the radioprotective measures (countermeasures), particularly liming of soils and applying the heightened doses of phosphoric fertilizers, reduces transfer of radionuclides from soil to plants and also elements of mineral nutrition included the microelements. It aggravates the deficiency of microelements following the decrease of productivity and quality of production in plant and animal breeding and exacerbation of the mentioned diseases. It is known, that many microelements have radioprotective properties, and same of them can influence on uptake of other elements in plants. Therefore, considering the situation with microelements, we can expect of their role in radiation protection of living organisms in a zone affected by accident in Chernobyl NPP. It was shown the applying (root injection) of zinc, manganese, cobalt, copper in the sulfates and chlorides (4-6 kg of metal per hectare) on soddy-podsolic soil, reduced the Sr 90 and Cs 137 transfer factor. Zinc was the most effective: the content of both radionuclides in grain of oats and lupine decreased in 1,5-2 times. Lesser efficiency was observed with manganese and cobalt, much less - with copper. Moreover, in some cases the increase of Sr 90 accumulation was observed. Influence of microelements was stronger in variants without fertilizers, than with their heightened doses. It happened because, firstly, fertilizers contain some various microelements. And, secondly, in favorable conditions for growth and development of plants provided by fertilizers, the action of both factors, positive, and negative, as a rule, is shown in a lesser degree. However, applying of microelements into row at sowing is a labor-consuming, technologically inconvenient and expensive method. Because of that method of foliar top-dressing or spraying by solutions of microelements salts was tested. Carried out field experiments on contaminated territories shown, that spraying of lupine and rape by 0,5 % water solutions of zinc, manganese, cobalt and copper sulfates (total content of microelements from 150 up to 450 g per hectare, i.e. in order less, than at direct applying into soil) reduced Sr 90 accumulation in a crop in 25-40 % and Cs 137 in 1,5-2 times. Increasing the quantity of salts their radioblockating properties, as a rule, increased. Addition of ammonium nitrate (1 %) to solutions intensified the action of microelements. Above method promotes the yield increase at the contaminated territories and solve a problem of use of nitrogen fertilizers, because direct applying of nitrogen fertilizers into soil acidify the soil solution. The foliar top-dressing of microelements in the form of complexonates solutions is essentially increased their radioblockating properties. Application of joint zinc-manganese bicomplexonate reduced Sr 90 accumulation in 1,5 times and Cs 137 in 1,5-2,5 times. In all cases the application of microelements, especially in the form of complexonates, promoted the plant productivity in 10-30 %. Under influence of microelements the degree of radiation damage of plants decreased. Radiation damages were estimated by amount of chromosomes aberrations in meristem cells of the next generation of plants, grown on the contaminated territories. It is shown that addition of the mentioned microelements, bicomplexonates and iodine to a ration of cows in the quantities compensating their natural need, reduced radionuclides accumulation in milk and meat in 30-50 %, and also promoted the increase of the microelements content in milk and, accordingly, its quality. (authors)