Acid–base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer

Publication Type

Conference Paper

Date Published



Measurements of aerosol number distributions down to one molecule have provided information that we’ve used to develop a new approach for modeling atmospheric nucleation rates. Measurements were carried out with the Cluster Chemical Ionization Mass Spectrometer (Cluster CIMS), the scanning mobility spectrometer using a diethylene glycol condensation particle counter as detector (DEG SMPS), and an ambient pressure proton transfer mass spectrometer for ammonia and amines (AmPMS). The model explains nucleation as a result of cluster evolution due to a sequence of acid-base reactions. We conclude that the smallest stable cluster contains four sulfuric acid molecules. The model leads to a simple analytic expression for nucleation rates that is reasonably consistent (i.e., ± 10x) with atmospheric observations. The model predicts that nucleation rates are equal to a prefactor, P<1, times the sulfuric acid vapor collision rate, (i.e., J=P⋅0.5⋅k11 ∗[H2SO4]2).

Conference Name

Nucleation and Atmospheric Aerosols: 19th International Conference

Year of Publication



AIP Publishing LLC

Conference Location

Fort Collins, CO