Die Anlagerung von Zerfallsprodukten der natürlichen Emanationen an elektrisch geladene Aerosole (Schwebstoffe).

In a previous paper an equation was derived for the attachment of the decay products of radon and thoron to aerosol particles. Considering the deposition to be solely governed by thermal diffusion (not by electrostatic forces) and assuming a quasi-stationary density distribution for the diffusing atoms, it was shown that the attached activity is proportional to where R is the particle radius and h=7·10 cm at NTP. As most aerosols in nature are electrically charged it is shown in the following paper how the diffusion process is modified by the influence of electrostatic forces between diffusing ions and charged aerosol particles. For the frequently occuring case of a symmetrically bipolar charged aerosol and ion diffusion it is furthermore shown that the attached activity is proportional to where x is dependent on the electrostatic charge and the radius of the aerosol particles. Applying this equation to the deposition of natural radioactivity on atmospheric aerosols and assuming that particle size-distribution can be roughly approximated by a law N (R)=const· R in the range 10 cm≦ R≦10 cm calculation shows that 90 to 95% of the total natural radioactivity should be attached to particles smaller than R=5·10 cm and as much as 50 to 75% to particles smaller than R=5·10 cm. It is concluded that the distribution of natural radioactivity on the different particle sizes in atmospheric and artificial aerosols is fundamentally dependent upon the diffusion process, including ionic diffusion. [ABSTRACT FROM AUTHOR]