1. Heterogeneous Reactions of α‑Pinene on Mineral Surfaces: Formation of Organonitrates and α‑Pinene Oxidation Products
- Author
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Hettiarachchi, Eshani and Grassian, Vicki H
- Subjects
Aerosols ,Air Pollutants ,Bicyclic Monoterpenes ,Kaolin ,Minerals ,Monoterpenes ,Nitrates ,Atomic ,Molecular ,Nuclear ,Particle and Plasma Physics ,Physical Chemistry (incl. Structural) ,Theoretical and Computational Chemistry - Abstract
Organonitrates (ON) are important components of secondary organic aerosols (SOAs). α-Pinene (C10H16), the most abundant monoterpene in the troposphere, is a precursor for the formation of several of these compounds. ON from α-pinene can be produced in the gas phase via photochemical processes and/or following reactions with oxidizers including hydroxyl radical and ozone. Gas-phase nitrogen oxides (NO2, NO3) are N sources for ON formation. Although gas-phase reactions of α-pinene that yield ON are fairly well understood, little is known about their formation through heterogeneous and multiphase pathways. In the current study, surface reactions of α-pinene with nitrogen oxides on hematite (α-Fe2O3) and kaolinite (SiO2Al2O3(OH)4) surfaces, common components of mineral dust, have been investigated. α-Pinene oxidizes upon adsorption on kaolinite, forming pinonaldehyde, which then dimerizes on the surface. Furthermore, α-pinene is shown to react with adsorbed nitrate species on these mineral surfaces producing multiple ON and other oxidation products. Additionally, gas-phase oxidation products of α-pinene on mineral surfaces are shown to more strongly adsorb on the surface compared to α-pinene. Overall, this study reveals the complexity of reactions of prevalent organic compounds such as α-pinene with adsorbed nitrate and nitrogen dioxide, revealing new heterogeneous reaction pathways for SOA formation that is mineralogy specific.
- Published
- 2022