We found that transfer of the radionuclide 241Am isotope from roots to top of the Arabidopsis thaliana plant was comparatively slow because the membranes served as an osmotic barrier [10]. Runoff played an important role in radionuclide transport. During flooding the radioactivity of bottom sediments was incorporated into the water column increasing the radioactivity by a many-fold increase. Radioactivity added from air-contaminated Chernobyl dust (nanometre to micrometer particles) too. Following rainfall, the deposition of this dust onto the surface of soil and water reservoirs increased radioactivity levels. By contrast, the radioactivity levels decreased in the Pripyat and Dnipro rivers and ChNPP cooling pond.

These data allowed us to develop a risk assessment approach for testing waste-water of Glyboke Lake, where radionuclide contamination with was considered high. We used sensitive plant assays to evaluate the genotoxicity of waters with different levels of radioactive pollution. Strong mutagenic effects were determined in water taken from Glyboke and Telbin lakes. Results obtained in all assays were related to the contaminated site levels.

Among scientists, there is a debate about the ChNPP cooling pond future. The problem is that the cooling reservoir surface is 7 m above the Pripyat river. This situation promotes annual discharge of about 100 million cubic meters of cooling water to the river. One solution being considered is the gradual draining of the reservoir. This will contribute to the formation of stable plant communities preventing dust transport in the form of micro-and nano-sized radioactive substances.

Radionuclide transformation in river water is a synchronous reflection of mobile species dynamics in soils that testifies to geochemical mechanisms controlling contaminant transport in the natural environment. For example bottom deposits of the Dnipro river reservoir system control the exchange of 137Cs. Dynamic transformation of the 137Cs from the solid phase in bottom sediment to water soluble form is described by logarithmical normal regularity, but the leaching of the 90Sr from sediments occurs according to a first-order kinetic law. Total radionuclide transport into the Black Sea basin during 15 years is assessed as 200 TBq of 90Sr and 20 TBq of 137Cs [11]. There are times after a rainfall that Dnipro and Pripyat river concentrations for radionuclide 90Sr and 137Cs ranges from 1.59 to 2.70 Bq/l and from 3.35 to 5.95 Bq/l. In contrast to 137Cs, the radionuclide 90Sr migrates in river water as a soluble compound within the range of 50-99%. The increased genotoxicity of plant test-assays suggest that there also was significant radionuclide contamination In the Chernobyl area was added to surface water by rainout of atmospheric dust (micro-and/or nano-sizes).

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