Abstract Number: 693 Working Group: Aerosol Transport and Transformation
Abstract One of the possible ways of formation of radionuclide release in the atmosphere is the wind rise of radioactive aerosol particles from surfaces contaminated with radioactive substances. The report will describe software for assessing the possible impact of atmospheric emissions of radioactive substances on the environment – RELTRAN. The main objective of this method is to estimate the source of emissions in the atmosphere and to predict the radiation situation around nuclear object in the territory of Russian Federation. A quantitative characteristic of the rising by the wind dust (with the known radionuclide composition of previous depositions) is the flux of dust particles.
The study of wind soil erosion is at the crossroads of several disciplines: deflation theory of soil, soil science, atmospheric physics, the theory of turbulence in the lower atmosphere, etc. At the present time, to solve the problems of interaction atmosphere and land surface are widely used hydrodynamic atmospheric models (WRF-ARW, COSMO and etc.). Such models numerically resolve a wide range of meteorological processes and contain information on the characteristics of the underlying surface. However, it is not possible to use only hydrodynamic models within this task because of secondary dust formation are not described in the framework of numerical prognostic models. The wind-lifting and radioactive dust transfer processes require the creation of an additional physical description. Hydrodynamic models can be used in this work as a source of input data for the created RELTRAN software.
It is extremely important to determine the critical wind speed necessary for the beginning of the ascent of soil particles for creating a physical description of these processes. The method of determining the critical wind speed must take into account the soil properties. The upper soil layer humidity is a special characteristic, as it is subject to strong changes. In the event that the force of the air flow is sufficient to start the salting, the concentration of sand particles will be calculated at the salting level. The salting level defines as a function of the friction velocity [Buttner, 1978, Pomeroy et al., 1992].
The amount of the flow depends on the ratio of the actual speed to its critical value and on the thermo physical characteristics of soil. The magnitude of the flow will give an opportunity to estimate the scale of soil erosion. It is important to consider the number of potentially available dispersed soil particles for blowing. If the ability of the flow to carry suspended particles increases, the processes of formation the suspension are activated. Since the main source of the solid phase is a surface, the concentration of suspended particles will decrease with altitude in proportion to the rate of their settling.
For creating the RELTRAN software, optimal methods will be chosen for calculating the critical wind speed and the flow of sand particles for the territory of the Russian Federation.