Towards a Molecular Understanding of Atmospheric Nucleation: Reactions of Amines with Sulfuric Acid Clusters

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Several new instruments will be used to explore the hypothesis that the high aerosol nucleation rates observed in the atmospheric boundary layer are primarily due to the reaction of amines with sulfuric acid molecular clusters. The cluster chemical ionization mass spectrometer (Cluster CIMS) measures the concentrations and masses of neutral molecular clusters produced by nucleation. The diethylene glycol condensation particle counter (DEG CPC), when used as the detector for an aerosol mobility spectrometer, allows measurements of particle mobility distributions down to 1 nanometer size. Parallel measurements with the Cluster CIMS allow definition of the complete spectrum of sizes down to one molecule. The ambient pressure proton transfer mass spectrometer (AmpMS) allows real-time measurements of amines. Computational chemistry will complement laboratory nucleation experiments and measurements in the atmosphere of Pittsburgh, PA by helping to elucidate processes that occur during chemical ionization in the Cluster CIMS as well as the thermodynamic and kinetic processes responsible for the formation of stable nuclei in the atmosphere.The formation of new particles by nucleation in the atmosphere affects concentrations of cloud nuclei and, therefore, the earth's albedo. Uncertainties in the cloud albedo effect are the largest source of uncertainty in climate models. Accounting for new particle production is one source of this uncertainty. This project will support two graduate students and a post-doctoral scholar as well as offer research experience opportunities to undergraduate students. Outreach activities will include presentations to and laboratory exercises with Minnesota school students, involvement in science camp efforts in collaboration with the Department of Chemistry's chapter of Women in Science and Engineering, and efforts to increase awareness of the health impacts of wood smoke emissions from cook stoves in developing countries.