This project involves laboratory experiments to better characterize the reactive chemistry of peroxy radicals in the atmosphere. Peroxy radicals are key intermediate species in the production of secondary organic aerosol and ozone, which are detrimental to human health and affect climate. A flow tube will be used in the laboratory to study peroxy radical reactions under many different environmental conditions. A better understanding of this chemistry has implications for modeling air quality and for informing policy decisions on mitigating air pollution levels that may be harmful to human health.
The objectives of this research are: (1) to determine the effects of molecular structure and degree of functionalization on isomerization rates and dimerization products of peroxy radicals (RO2); (2) to determine the organic nitrate yield and alkoxy radical fate of functionalized RO2 species; and (3) to determine the branching ratio of hydroperoxides (ROOH) and OH in RO2-HO2 reactions where the RO2 radical is functionalized. The first objective involves probing RO2 unimolecular reactions and RO2-RO2 reactivity and determining the relative importance of each process. The second objective includes probing RO2-NO reactivity and evaluating the relative rates between these reactions and the isomerization reactions described in the Objective 1. The third objective will help to assess the hypothesis that the yield of OH increases as the degree of functionalization increases in RO2- HO2 reactions. In clean environments, where bimolecular lifetimes are long, multiple isomerization reactions might lead to RO2 species that are very functionalized and more likely to yield OH when reacting with HO2 than to form peroxides. The results from these experiments will provide fundamental experimental data on isomerization rates and branching ratios of bimolecular reactions of RO2 necessary to understand atmospheric oxidation. The success of this research will lead to the improved modeling of oxidation processes, under the conditions of both “high†and “low" NOx environments, thereby helping to improve predictions of both air quality and climate change.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
