Formation of atmospheric ultrafine particles and ions from trace gases

Abstract

Firstly, the importance of ultrafine particles in the atmospheric aerosol is reviewed. Based on conventional nucleation theory, it is shown that water vapor alone cannot initiate the formation of such particles. We consider a mixture of water vapor and sulfuric acid and, pursuant to a discussion of theoretical results obtained by various writers, we consider the case under atmospheric conditions. We demonstrate that this leads to orders of magnitude which compare with the results of simulation experiments now under way. Secondly, we study the mobility spectrum of atmospheric ions, based on mobility mass correlations, and we demonstrate that Thomson's conventional theory, calling upon only the presence of water vapor in the atmosphere, does not allow for the interpretation of the atmospheric ions' mobility spectrum observed in our experiment. This spectrum is qualitatively interpreted by generalizing the theory of Thomson and by introducing in it the simultaneous presence of water vapor and sulfuric acid.