Abstracts

Water Ecosystems

More then 30 years the plutonium-producing Mining-Chemical Combine (Zheleznogorsk city) discharged radioactive wastes into the Yenissei river. The radioactive contamination zone that formed is the longest in Russia, it extends for about 1500 km along the Yenissei banks. For a long time until three out of five reactors in operation at the Mining-chemical combine have been shutdown (1992) the radioecological situation on the Yenissei was under control of Minatom and information was not accessible for the public. Several Minatom-independent expeditions of the Russian Academy of Sciences held since 1992 formed prerequisites for objective estimate of the radiation situation in the Yenissei river valley.

For this purpose we develop a one-dimensional mathematical model of radionuclide migration in the Yenissei river ecosystem which no involves the following processes: dilution, advective transfer of by water masses, radioactive decay, bioaccumulation and migration of radionuclides over trophic chains, adsorption of radionuclides sedimentation of dead organic matter and formation of detritus.

The ecosystem model consists of 7 equation describing the process of space and time dynamics of dissolved organic matter (DOM), bacteria, phytoplankton, zooplankton, phytobenthos, zoobenthos and detritus. The radiation submodel describing migration of radionuclide over the trophic chain involves 10 equations that make possible to calculate content of radionuclide and its stable analog in water, in hydrobiont biomass and detritus. The ecosystem model and the radiological submodel verified against all available information on the Yenissei river. These are data of Goskomgidromet on the hydrochemistry of the river, data of the Institute of Biophysics (Russian Academy of Sciences, Siberian Branch) on kinetic characteristics of certain plankton groups and data of the Yenissei expedition of the Limnological Institute (Russian Academy of Sciences, Siberian Branch) on spatial distribution of biomass of major hydrobiont groups.

Experiments on spatial distribution of cesium-137 in the Yenissei river ecosystem components were provided. This preliminary calculation showed that the natural selfpurification process contribution was not great. The extended zone contaminated with cesium-137 could form both as a result of primary contamination and is not necessarily resedimentation of bottom sediments contaminated in the near zone. The work is supported by joint grant № 99-05096003 р99Yenissei of the Russian Fundamental Research Fund and Krasnoyarsk krai Science Fund and the US CRDF, grant REC002.

Note. Abstracts are published in author's edition

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