Condensation Of Organic Vapors Research Articles

A hypothesis for growth of fresh atmospheric nuclei

The formation of new atmospheric particles, roughly 1–2 nm in diameter, has drawn a lot of attention recently because of (1) their possibly negative effects on human health and (2) their potential to grow into cloud condensation nuclei, thus affecting cloud formation as well as the global radiation budget. At these small sizes, the Kelvin effect prevents condensation of any compound in sufficient abundance for producing substantial growth. But heterogeneous reactions may play a critical role in helping these nm‐sized nuclei cross the huge Kelvin‐effect barrier and facilitating further condensation of organic vapors. Its implications in the marine boundary layer and engine exhausts are discussed.

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.