CAREER: Dynamics of Peroxy Radicals at Extended Lifetimes: A Key Missing Piece in the Canonical Mechanism

This CAREER project will provide new knowledge on the fate of peroxy radicals in the atmosphere. Experiments will be conducted in the NSF NCAR chamber facility to study the mechanisms and kinetics of peroxy radical reactions. As a result of worldwide reductions in nitric oxide emissions, the lifetimes of peroxy radicals is extended, creating a new regime for their fate. The new knowledge developed through this research will be critical for vast regions worldwide transitioning from polluted environments to a regime of limited nitric oxide influence. The overarching goal of the research is to gain a mechanistic understanding of the interconversion and ensuing isomerization of various peroxy radical (RO2) structural isomers at their extended lifetimes, and to evaluate the significance of this chemistry in driving the secondary organic aerosol (SOA) formation. The specific objectives of the project are to: (1) Characterize the range of RO2 lifetimes by creating a unique “intermediate- nitric oxide” regime in steady-state chamber experiments and box model simulations; (2) Estimate the rates of interconversion and ensuing isomerization of aromatic RO2 isomers by monitoring the characteristic product distributions across varying RO2 lifetimes; and (3) Pinpoint the dominant isomerization pathway of each aromatic RO2 isomer and identify the produced highly oxidized organic molecules (HOMs) that contribute to the SOA formation. The project is expected to support six undergraduate students as they prepare for graduate study in atmospheric science. Educational materials on air quality will also be developed for the local high schools. 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.