Collaborative Research: Transmission Electron Microscope (TEM) Studies of Soot, Organic Matter, and Associated Aerosol Particles During CalNex

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New information about the role of aerosol particles in climate change and health will be provided by a three-pronged research program to a) obtain detailed information about aerosol particles, including metal-bearing nanoparticles, collected in the greater Los Angeles area during the California: Research at the Nexus of Air Quality and Climate Change (CalNex 2010) campaign; b) develop and apply new ways of characterizing organic matter (OM) within aerosol particles; and c) integrate those results into a global climate model. In part a) transmission electron microscope (TEM) measurements of the various types of aerosol particles during CalNex 2010 will provide data regarding shapes, structures, optical properties, intergrowths, and mixing states that are unavailable by other methods and will complement the information collected by other groups. The TEM results of part a) will be compared to those obtained using other aerosol measurement techniques. They will be compared to those of a prior study in and around Mexico City, thereby contributing to a synthesized overview of aerosol properties in megacities. Part b) will include determinations of i) OM functional groups and refractive indices using ultrahigh-resolution electron energy-loss spectroscopy with new aberration-corrected TEMs, ii) OM hygroscopicity using a unique environmental cell within a TEM, and iii) OM volatility using controlled step heating in the environmental cell. By comparing results from these emerging analytical techniques, it is anticipated that new microphysical and chemical information will be obtained about the semi-volatile and non-volatile fractions of airborne OM within individual particles. In part c), the results of parts a) and b) will be used to calculate optical properties of internally mixed soot and OM, which will then be incorporated into global climate models to evaluate their broad impact.The research will contribute to understanding two of the most important problems confronting humanity: anthropogenic global climate change and environmental pollution. Accurate prediction of climate change requires detailed understanding of the radiative-forcing properties of aerosol particles, for which these analyses will provide comprehensive and unique information. Determining the occurrences and compositions of metal-bearing airborne nanoparticles is important for understanding how they are transported from their industrial sources and how they might interact with lung and other tissue and thus affect health. This project will also contribute to training of a graduate student and postdoctoral researcher, including extensive mentoring activities and presentations at professional meetings. In addition, three-dimensional TEM images will provide young students with simple and intuitive pictures of what some of the particles humans inhale look like. Outreach will include science talks to school groups (including grade schools), presentations during annual Earth Day events, and interviews with U.S. and overseas news media.