The transport and deposition of radionuclides in the atmosphere can be intercepted by trees and other vegetation. Also, a large amount of rain precipitation can be caught by trees and vegetation as interception. Therefore, the simple process of modeling deposition due to the wet removal (Dw = Dw(x, y, z, t)) by taking into account the effect of leaf interception in the terrestrial ecosystem can be described below for a specific radionuclide, i, with mean concentration Cj = C(x, y, z, t):
where L is the leaf area index, R(x, y, z, t) is the amount of rain precipitation (mm), kx and k2 are the constants. The wet deposition process can be refined by employing the following improved equation:
where Dw depends not only on the amount of rain precipitation but also on the frequency and duration of the precipitation event. F(x, y, z, t) is the fraction of the cloud in which the precipitation occurred. @ is the frequency with which cloud water is converted to rainwater
Figure 3 Schematic diagram of physical, chemical, and biological processes influencing the biogeochemical cycles of radionuclides.
Top of turbulent mixing layer
Wind advection ocy
Dry deposition / L I I
Radioactive decay, physical, chemical and biological processes
Venting to free troposphere
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