Acid-base chemical reaction model for nucleation rates in the polluted atmospheric boundary layer
Authors
Modi Chen — MSP Corporation
Mari Titcombe — University of Minnesota
Chongai Kuang — Brookhaven National Laboratory
Marc L. Fischer — Lawrence Berkeley National Laboratory
Fred Eisele — University Corporation for Atmospheric Research
David R. Hanson — Augsburg College
Peter H McMurry — University of Minnesota
Category
Aerosol Properties
Description
This poster summarizes our recent discoveries regarding the chemical and physical processes that determine boundary-layer nucleation rates. The new model for nucleation rates that we developed is based on measurements of neutral molecular clusters with the cluster chemical ionization mass spectrometer (Cluster CIMS) and measurements of number distributions down to 1 nm with a scanning mobility particle spectrometer that utilizes our new diethylene glycol condensation particle counter (the DEG SMPS). Together, these instruments allow measurements of the entire number distribution down to one molecule. In addition, the ambient pressure proton transfer mass spectrometer (AmPMS) provided critically important measurements of basic gases including ammonia and amines. The model is based on measurements carried out using these instrument systems in Atlanta (2009) and in laboratory chamber studies (2010).The model is the simplest model we could find that is consistent with our observations. It shows that a sequence of acid-base chemical reactions leads to the formation of stable clusters. This model leads to a simple analytic expression for nucleation rates that is in reasonable agreement with atmospheric observations.