Origins of aerosol sulfur size distributions in the Los Angeles basin

Abstract

Low pressure impactor measurements show two distinct types of fine particle sulfur size distributions in Los Angeles, California. These two types of aerosol sulfur have mass median diameters of 0.54 ± 0.07μm and 0.20 ± 0.02 μm, respectively. Factors which may account for the two distribution types, including effects of relative humidity, coagulation, fogs and formation mechanisms, are discussed. Calculations show the 0.5 μm sulfur is consistent with chemical reactions in the aerosol phase, whereas the 0.2 μm sulfur results from homogeneous gas phase SO 2 oxidation. While the growth of the total aerosol volume distribution is not too sensitive to the mechanism, the chemical species distribution strongly depends on the growth law, and can be used to establish its form.