AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Nucleation of Sulfuric Acid Particles with Various Atmospherically Relevant Bases
COTY JEN, Ryan Bachman, Jun Zhao, Peter H. McMurry, David Hanson, University of Minnesota
Abstract Number: 29 Working Group: Aerosol Chemistry
Abstract Atmospheric nucleation is the formation of stable aerosol particles from trace precursor gases and accounts for up to half the global cloud condensation nuclei. Thus, accurate predictions of global climatic cooling by aerosols and clouds require understanding the chemical processes that lead to nucleation. Atmospheric nucleation typically correlates with sulfuric acid concentrations, but clusters formed from water and sulfuric acid alone are unstable and require stabilizing compounds to reduce cluster evaporation rates and form stable particles. Here, we present evidence from flow reactor studies on the ability of various basic gases to react with and stabilize sulfuric acid clusters that ultimately form particles. We show which basic gases produce the most particles given equivalent sulfuric acid and base concentration. In addition, we show that the ratio of base to sulfuric acid concentration ([B]/[A]) is a useful parameter to compare the relative importance of acid and base uptake rates. At low [B]/[A], sulfuric acid has a higher collision rate than the base molecules; in this regime, the ability of a base molecule to stabilize sulfuric acid cluster limits the particle formation rates. Our experiments primarily operate in this low [B]/[A] and give us the sensitivity to determine the relative stability of clusters formed from sulfuric acid and various base molecules. At high [B]/[A], growth rates are limited by sulfuric acid collision rates and evaporation is unimportant, at least for most amines.