Sulfuric acid nucleation: power dependencies, variation with relative humidity, and effect of bases J. H. Zollner1, W. A. Glasoe1, B. Panta1, K. K. Carlson1, P. H. McMurry2, and D. R. Hanson1 1Department of Chemistry, Augsburg College, Minneapolis, MN 55454, USA 2Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
Abstract. Nucleation of particles composed of sulfuric acid, water, and nitrogen base
molecules was studied using a continuous flow reactor. The particles formed
from these vapors were detected with an ultrafine condensation particle
counter, while vapors of sulfuric acid and nitrogen bases were detected by
chemical ionization mass spectrometry. Variation of particle numbers with
sulfuric acid concentration yielded a power dependency on sulfuric acid of
5 ± 1 for relative humidities of 14–68% at 296 K; similar experiments
with varying water content yielded power dependencies on H2O of ~7.
The critical cluster contains about 5 H2SO4 molecules and a
new treatment of the power dependency for H2O suggests about 12 H2O
molecules for these conditions. Addition of 2-to-45 pptv of ammonia
or methyl amine resulted in up to millions of times more particles than in
the absence of these compounds. Particle detection capabilities, sulfuric
acid and nitrogen base detection, wall losses, and the extent of particle
growth are discussed. Results are compared to previous laboratory nucleation
studies and they are also discussed in terms of atmospheric nucleation scenarios.
Citation: Zollner, J. H., Glasoe, W. A., Panta, B., Carlson, K. K., McMurry, P. H., and Hanson, D. R.: Sulfuric acid nucleation: power dependencies, variation with relative humidity, and effect of bases, Atmos. Chem. Phys., 12, 4399-4411, doi:10.5194/acp-12-4399-2012, 2012.