EVALUATION OF THE EFFECT OF HORIZONTAL DIFFUSION ON THE LONG-RANGE ATMOSPHERIC TRANSPORT SIMULATION WITH CHERNOBYL DATA

The effect of horizontal diffusion on the long-range transport simulation is examined with a Lagrangian particle transport model. The transport of radioactivity released from Chernobyl is simulated by the model with different values of horizontal diffusivity. The computed concentrations are statistically compared with measured concentration. The best simulation is found when the magnitude of the horizontal diffusivity is between 3.3 X 10(4) and 1.0 x 10(5) m(2) s(-1). The performance of empirical formulas of horizontal diffusion, in which mean-square displacement sigma y is specified as a function of time, is also examined. A part of measured concentrations, which are relatively low concentrations, cannot be explained by transport and diffusion only. It is shown that these measured concentrations can be explained by resuspension of deposited radioactivity.