The ion-aerosol balance equations have been solved for different mixing strengths and two types of ionization profile to get vertical profiles of atmospheric electric parameters close to the Earth's surface. The inclusion of surface radioactivity in the model causes the decrease in electric field to be more intense at lower levels than at higher levels, an increase in the asymptotic value of the field, and an increase in the space charge density gradient. When the mixing of atmosphere is very weak, a reverse electrode effect is observed under the condition of enhanced ionization due to trapped radon, with the decrease in ion densities above 1 m. However, with an increase in eddy diffusivity, the positive ion concentration decreases, and the negative ion concentration increases with increasing height above the diffusion layer. Further increase in eddy diffusivity causes the profiles to become almost similar to those for which the ionization is constant with height. Even with the inclusion of radon radioactivity, relatively higher diffusivity keeps the nature of the profile of the negative ions similar to that for the constant ionization case. On the contrary, there is a drastic change in the profile of positive ions because of the strong downward gradient of positive ions in the diffusion sublayer. The profile of positive ions is more sensitive to the radon radioactivity and that of negative ions to the strength of turbulence. Further, the asymptotic value of aerosol concentration is reached before that of small ions when mixing is very low. Our results are in reasonable agreement with the earlier theoretical and experimental studies. ¿ 2001 American Geophysical Union