NANOMETER AND ULTRAFINE AEROSOLS FROM RADON RADIOLYSIS

The ability of ionizing radiation to produce condensation nuclei aeros ols in filtered air is well known. Recent studies have indicated that radiolysis results initially in the production of highly diffusive, na nometer-sized (< 2 nm) clusters. Aerosols in the 1-10 nm range are als o produced by other processes mostly involving nucleation, e.g. for pu rposes of materials synthesis. Radiolytic nuclei can be formed by the binary ion-induced nucleation of the precursor vapors, such as sulfuri c acid and water, ultrafine particles (> 5 nm) can then evolve by coag ulation and growth processes. The nanometer nuclei are, however, poorl y detected by condensation nuclei counters (CNCs) since CNC efficienci es drop sharply for particle sizes < 5 nm. In this work, the formation of: (1) PoO(x) molecular cluster aerosols from the decay of radon, an d (2) sulfuric acid nanometer nuclei and ultrafine aerosols from the r adiolytic oxidation of SO2 in radon-air mixtures, were studied through wire screen-based size distribution measurements of the Po-218 radioa ctivity associated with the aerosols. Comparisons with conventional di ffusion battery-CNC derived number size distributions are also present ed.