CAREER: Chemical Processing and Cloud Nucleation Activity of Soot Aerosol

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This proposal focuses on the interactions of soot particles with gas phase species and how this may alter their ability to act as ice and warm cloud nuclei. Using a diffusion chamber coupled with a chemical ion mass spectrometer, and a cloud condensation nuclei (CCN) counter, chemical aging of aerosols will be studied and ice nucleation observed under upper tropospheric conditions. Measurements of warm cloud condensation nuclei efficiency of aged soot will also be conducted. Questions to be addressed include:1. Do soot aerosols react with oxidizing agents, such as ozone, OH radicals, and NO2? Is oxidation a significant sink for tropospheric soot aerosol? What are the major gas phase products of the oxidation?2. What is the ice nucleation (IN) activity of soot aerosol? Is IN activity altered by oxidation reactions or by organic coatings? Is there a correlation between altered IN activity and increased CCN activity due to aging processes?In the educational component, high school students will measure precipitation in and near Houston, TX. Surface tension measurements of the precipitation samples will be made and used as an indication of pollutant levels as a function of locale. Undergraduates in a new atmospheric chemistry laboratory course will coordinate with the high school students to chemically characterize representative precipitation samples. Results will be used to identify compounds present in the urban environment that could act as ice nuclei or CCN, and to determine whether organic compounds present are surface active and therefore capable of altering cloud nucleation activity. Broader impacts also include teaching about air pollution and proper scientific methods to high school students who will be creating a location-specific data set of the volume and composition of precipitation in and around Houston. Graduate, undergraduate and high school students will work jointly on this project and publish the results. Data from this study will be put into formats useful for teaching about air quality issues at the high school level. The results will be disseminated broadly, including kickoff and summary lectures at the high schools.