Condensation of Organic Vapors on an Externally Mixed Aerosol Population

The condensation of organic vapors on a nearly monodisperse exter nally mixed aerosol population was measured in order to test the hypothesis that organic species may preferentially condense on specific substrates. The organic species tested were glutaric acid, a typical secondary organic species, and DOP, a model organic for primary species. A series of organic and inorganic substrate pairs were investigated: NaCl, (NH₄)₂SO₄, glutaric acid, and adipic acid. The growth of these aerosol populations was measured using a Tandem Differential Mobility Analyzer and the results were analyzed using transition regime mass transfer theory. The results show that no detectable preferential condensation occurs for either species on any of the substrates studied. The implications of these results to SOA formation models are discussed.