DIURNAL-VARIATION OF THE CONCENTRATIONS OF RADON AND ITS SHORT-LIVED DAUGHTERS IN THE ATMOSPHERE NEAR THE GROUND

The continuous measurement of radon (Rn-222) and randon daughters (RaA (Po-218), RaB (Pb-214), RaC (Bi-214)) concentrations and meteorological parameters (temperature, wind velocity) is carried out simultaneously at different heights of the boundary layer near ground level (0.1, 1, 2 and 5 m above the ground) over a long time period with the aim of determining the change of the eddy diffusivity near ground level during a day under different weather conditions. The results show the great variation of the activity concentration of randon and randon daughters during a day (up to a factor of 20) depending on weather conditions. The temperature gradient appears to provide a good indication of which eddy diffusivity most closely represents the mixing strength in the atmosphere. The change of the equilibrium values between radon and its daughters during a day were used to calculate the diurnal variation of the eddy diffusivity.