RUI: Laboratory Studies of Particle Nucleation--Homogeneous Nucleation Involving Sulfuric Acid (H2SO4), Water (H2O), and Ammonia (NH3) Vapors

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The investigator will measure the rate of nucleation of new particles in flow reactor experiments. The formation rate of new particles will be measured as a function of sulfuric acid concentration, temperature, relative humidity and ammonia concentration. The researchers plan to deploy as sources of sulfuric acid both the vapor over the bulk liquid and in situ oxidation of sulfur dioxide via hydroxyl radical generated photolytically. Measurements in the binary system to higher relative humidities and to lower temperatures are needed as a baseline for understanding nucleation within the flow reactor and for evaluating theoretical models. The photolytic system will allow for an extended source of sulfuric acid that balances its loss to the wall, facilitating the analysis and interpretation of nucleation results. For example, it will allow for a controllable exposure to a particle growth agent so that particles can be efficiently detected by the particle detector. The extended source will also allow for exploration of nucleation at low sulfuric acid concentrations. Finally, verification is needed of recent work using a photolytic source that showed enhancements in the nucleation rate of factors of 105 or more over bulk source nucleation rates. This work will contribute to understanding nucleation in the atmosphere and how it influences the concentration of cloud condensation nuclei whose role in climate processes is believed to be large but is still quite uncertain. Understanding the formation of atmospheric particles is also important as inhaled particulate matter is a health hazard. Flow reactor experimental methods for measuring particle formation and growth will be further developed. Results for nucleation rates in the sulfuric acid, water, and ammonia systems will be synthesized and a comprehensive picture of laboratory work will be developed. This will aid interpretation of field data and evaluating mechanisms of nucleation.The project will enhance the research and the educational culture at Augsburg College by offering a research opportunity for undergraduates interested in the environmental sciences. The work is timely and important, which will foster a dedication to the work and fuel the student's imagination. The project will enhance undergraduate training by providing: (a) a high quality work experience where basic laboratory skills will be developed, (b) enhance motivation by obtaining research results that can affect our understanding of global warming processes, and (c) provide opportunities for presenting results at local and national meetings. This project will foster the continuation of the partnership between a private liberal arts college and a public research university, thereby expanding learning and training opportunities for Augsburg College's student population. It is expected that women and persons from underrepresented groups will continue to be the majority of the undergraduate students in the PI's lab. Dissemination of results will include presentations at local and national scientific meetings and manuscript publications.