Collaborative Research: Quantifying Secondary Organic Aerosol Formation from the Reactive Uptake of Isoprene-derived Epoxides to Submicron Aerosol Particles

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In this project, funded by the Environmental Chemical Sciences program in the Division of Chemistry, Professor Joel A. Thornton of the University of Washington (UW) and Professors Jason D. Surratt and Avram Gold from the University of North Carolina (UNC) are studying a process by which emissions from terrestrial vegetation (e.g., deciduous trees) are converted to particulate matter (PM) mass in the atmosphere. PM is a major cause of reduced air quality, with negative impacts on human health, and also affects climate by scattering or absorbing sunlight or by altering the properties of clouds. Terrestrial vegetation emits large quantities (~500 teragrams C) of isoprene to the atmosphere each year. Once in the atmosphere, photochemical oxidation of isoprene leads to gas-phase epoxide intermediates. These epoxide byproducts are reactive in acidic solutions, and therefore uptake and reaction in atmospheric particles can produce soluble low-volatility organic compounds that remain in the particle phase thereby increasing PM. The broader impacts of this project include more accurate interpretations of PM source-apportionment and improved studies of aerosol-climate effects and air quality assessments. In addition, a key element of the project involves the training of highly skilled young scientists and engineers by involving undergraduate students, graduate students, and postdoctoral research fellows, and engaging the general public through a range of outreach activities. In this project, Professor Joel A. Thornton will lead a collaboration between UW and UNC to measure the key physico-chemical parameters governing reactivity, diffusion, and product formation of synthesized authentic standards of the predominant isoprene-derived epoxides in atmospherically realistic particles. The 100-500 nanometer sized particles will be mixtures of inorganic salts, liquid water, and organic matter, providing an advance over studies using bulk macroscopic solutions which cannot simulate the non-ideal, often super-saturated compositions of atmospheric particles, nor the morphologies of the reaction medium.