UNATTACHED FRACTION AND SIZE DISTRIBUTION OF AEROSOL-ATTACHED RADON PROGENY IN THE OPEN-AIR

Unattached fractions of the radon progeny Po-218 and Pb-214, size dist ributions for both unattached Po-218 and Pb-214, and attached Pb-214 a nd Bi-214, along with condensation nuclei (aerosol-particle concentrat ions), were measured in the open air of the city of El-Minia, Egypt. T he measurements were performed with a wire-screen diffusion battery an d a low-pressure Berner cascade impactor using standard methodologies. The results for parameters of derived distributions demonstrate that the distributions for the former (unattached Po-218 and Pb-214) are ne arly similar. The diffusion equivalent diameters (d(f)) of Po-218 and Pb-214 were determined to be 1.4 and 1.55 nm with relative geometric s tandard deviations (sigma(g)) of 1.65 and 2.1, respectively. The latte r distributions (attached Pb-214 and Bi-214) are nearly identical. Mos t of the activities were associated with the aerosol particles of the accumulation mode. The mean activity median aerodynamic diameters (AMA D) of Pb-214 and Bi-214 have the same value of 380 nm but the relative geometric standard deviation of the log-normal distribution of Pb-214 shows a broader activity distribution than Bi-214 (sigma(g) = 2.2 for Pb-214 and sigma(g) = 2.05 for Bi-214).