Radiocapacity: Characteristic of stability and reliability of biota in ecosystems

Abstract

In models of radiocapacity for miscellaneous types of ecosystems (slopes, water ecosystems etc.) rather small levels of primary contamination of ecosystems are established, which, due to the laws of reallocating of radionuclides, may result in concentration in biota of critical levels of the contents of radionuclides and formation of noticeable radiation doses. From a number of estimations, dose rates in biota of 0.4 Gy/year for animals and 4 Gy/year for plants can notably oppress growth and condition of biota in ecosystems. If we accept ecological risk arising at these doses, it is possible to define for a unit of biomass, concentrations of radionuclides which are capable of giving similar radiation doses. This give a value for 137Cs of 100 kBq/kg for animals and 1000 kBq/kg for plants, as an example. Based on a hypothesis about linear increase of ecological risk for biota from 0 up to 1, with increase in the level of radionuclide contamination of ecosystems, the general ecological risk from miscellaneous radionuclides which accumulate in a real ecosystem can be estimated. Thus, for each type of ecosystem (aqueous or terrestrial), depending on dynamics of reallocating of radionuclides, with the help of models of radiocapacity, it is possible to establish marginal primary levels of radionuclide contamination of ecosystems. It is shown that these primary levels of radionuclide contamination can be very rigid. We for the first time demonstrate a method for ecological standardisation of miscellaneous ecotoxicants-pollutants on the basis of the theory of both models of ecological capacity and radiocapacity of a miscellaneous type of ecosystem. The analysis of dynamics of distribution and reallocating of tracer (137Cs) in model ecosystems - aquacultures of plants - is conducted. This analysis has allowed us to establish that in response to stressful factors, the biota of ecosystems is able to change rapidly the TF (Transfer Factor) and consequently to cause fast reallocation of tracer and its removal from biota in the environment. As stressful factors we have used in experiments - acute gamma-irradiation of seeds and deposition of salts of heavy metals (CdCl2) in different doses. In laboratory experiments the dose relation is established as the rate of change of parameters of radiocapacity at operating doses of irradiation and heavy metals. The given approach and method allows one to predict an ecological setting of permissible resets and outlets of pollutants in environment using unified idealised standards. The given method obeys the fundamentals of equidosimetry showing that stressful factors affect biota in the same way as influencing the parameters of radiocapacity. Thus, it is feasible to sum the total effect of miscellaneous factors on biota in terms of radiation doses. © 2006 Springer.