RUI: Mechanistic and Kinetic Studies of the Atmospheric Chemistry of Isoprene and its First-Generation Products

California State University-Fresno Foundation, Fresno CA

Investigators

Abstract

Isoprene is a biogenic volatile organic compound with the largest global emissions flux of any hydrocarbon. It thus has a major impact on the composition and chemical behavior of the troposphere. While the atmospheric reactions of isoprene have been extensively studied, the reaction mechanism is complex and standards for many of the multi-functional compounds that are expected to be important reaction products are not available. Consequently, some important aspects of isoprene chemistry are still poorly understood. These include the formation and reaction of hydroxyl hydroperoxides from the reaction of hydroxyl (OH) radicals with isoprene under low nitrogen oxide (NOx) conditions, and the chemistry of isoprene nitrates generated by the reaction between nitrate radicals and isoprene. These reactions are likely to have a substantial impact on hydrogen oxide radical and NOx levels, and on the formation of secondary organic aerosol. Synthetic organic chemistry will be combined with gas phase kinetic and mechanistic studies to elucidate key pathways in the atmospheric chemistry of isoprene and some of its first generation products. The strategy will be first to synthesize target reaction products (hydroperoxides, carbonyl nitrates and hydroxynitrates). The kinetics and mechanisms of their reactions with atmospheric oxidants will then be investigated in both static photochemical reactors and within a flow tube, followed by product characterization and yields from the reaction of isoprene with OH and nitrate radical. The project will enhance teaching and training of undergraduate and graduate students, providing opportunities to four undergraduate students each year. It will be especially effective in enhancing participation in science by underrepresented groups. It will continue a productive partnership between Fresno State and the National Center for Atmospheric Research (NCAR), which will facilitate the development of the students as independent scientists. The project will also support outreach efforts at Fresno State to both increase the number and diversity of students entering STEM fields, and to increase community awareness of air quality and climate change issues. The project will include scientist participation in workshops focused on providing local earth science teachers with tools necessary to understand and communicate climate science to their elementary and high school students. Scientist lectures will be teleconferenced to remote sites, and the project contribution to the workshops will include imparting knowledge about connections between observations and models, as well as assisting teachers in understanding the limitations and strengths of models in predicting climate.