Collaborative Research: Atmospheric Nanoparticle Growth from Nitrate (NO3) Radical Initiated Oxidation of Monoterpenes

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This project combines the results of laboratory studies with numerical modeling to investigate the growth of tiny nanoparticles in the atmosphere. It is important to understand the growth of these tiny particles because they can influence the formation and properties of cloud droplets. This research will lead to the development of a mechanistic model to better predict the influence of aerosol on climate and air quality. Laboratory experiments will be conducted to identify and quantify the gas- and particle-phase products of the reactions of NO3 radicals with three common monoterpenes: α-pinene, β-pinene, 3-carene, and an additional compound, α-thujene, which is structurally similar to α-pinene and should likewise form gas phase products that contribute minimally to nanoparticle growth. These experiments will be conducted for a range of NO3 concentrations, humidities, and temperatures. Computational chemistry studies will provide insight into possible reaction mechanisms and nanoparticle growth due to monoterpene oxidation by NO3 radicals.The three objectives of the project are: (1) Implement computational chemistry methods for elucidating reaction pathways and developing CIMS detection strategies; (2) Perform comparative laboratory studies of NO3 radical initiated oxidation of monoterpenes; and (3) Obtain chemical closure between gas phase precursors and nanoparticle physicochemical properties. The process-level model for nanoparticle growth, developed through this project, will be tested using experimentally measured growth rates. Nanoparticle growth is directly tied to the ability of these particles to influence cloud condensation nuclei populations and affect the formation and properties of cloud droplets. This collaborative project includes a "near-peer" program that pairs University of California at Irvine graduate students with Reed College undergraduates in order to facilitate scientific interactions and to prepare the undergraduates for graduate study.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.