Role of Oxidative Conditions on the Formation of Aerosol and Organic Nitrates from the Reactions of Monoterpenes with NO3 and OH radicals

DeVault, Marla P

Graduate Thesis Or Dissertation

Role of Oxidative Conditions on the Formation of Aerosol and Organic Nitrates from the Reactions of Monoterpenes with NO3 and OH radicals Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/1j92g897h

Abstract

Monoterpenes are widely emitted biogenic volatile organic compounds, which react quickly in the atmosphere and the oxidized products of which can partition into secondary organic aerosol (SOA). Understanding the types of products that are formed, how they might react in the particle-phase, and the effect of oxidative conditions on these factors is key for improving atmospheric models. This thesis presents three studies of monoterpene oxidation, with an emphasis on the role of organic nitrates in SOA. First, the products for Δ-3-carene are outlined in detail from NO₃ radical oxidation in a regime where self- and cross-reactions of alkylperoxy radicals (RO₂) are the primary fate of RO₂’s. These products include a small amount of an ROOR gas- and particle-phase dimer, but the majority of the products contributing to SOA are acetal and hemiacetal dimers. Then, this work is expanded to two other cyclic monoterpenes (α-pinene and limonene) and an acyclic ocimene. When compared to previous work with α-pinene, it is clear that acetal and hemiacetal dimers and trimers dominate the SOA of cyclic monoterpenes. This is not the case for linear ocimene, which shows a small degree of oligomerization in the particle-phase. Finally, these five monoterpenes are then oxidized by OH radicals in the presence of NOx, another way to form organic nitrates in the atmosphere. The SOA collected from these reactions have a similar degree of nitrate retention but little to no oligomerization. In addition, the SOA is shown to hydrolyze during analysis, which has implications for the atmospheric conditions under which the organic nitrates will last. Together, these works provide insight into monoterpene derived organic nitrates and their fates.

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