An Investigation of the Gas-Phase Products of NO3 Radical Oxidation of Δ-3-Carene

Olivia Jenks,
ANYL 3rd year, de Gouw Group

"Organic aerosol can have an impact on the climate, visibility, and human health. Oxidation of biogenic volatile organic compounds forms secondary organic aerosol (SOA) by lowering the volatility of the molecule and partitioning to the particle phase. The NO3-initiated oxidation of Δ-3-carene is being studied because it connects the interaction of biogenic and anthropogenic emissions to form aerosol, and expands on previous work with ɑ- and β-pinene. In this work, I explore the first generation gas-phase products of the NO3-initiated oxidation of Δ-3-carene in a 8 m3 Teflon FEP chamber using a Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus PTR-ToF) and a high-resolution time-of-flight chemical-ionization mass spectrometer (HR ToF-CIMS) using iodide adducts. The mass spectra of reaction products show the presence of many of the expected products, including hydroxynitrates, dicarbonyls, hydroxycarbonyl nitrates, hydroxy dicarbonyls, and dicarbonyl hydroxynitrates, but also show significant fragmentation of the parent ions through loss of water and/or nitric acid. Parent and fragment ions are grouped together taking advantage of gas-wall interactions in Teflon tubing, which provide some simple “poor-person’s chromatography,” while transmitting all the species. Understanding the mechanism of the oxidation of Δ-3-carene by NO3 radicals allows for a better understanding of the fate of organic nitrate in the atmosphere, which will improve interpretation of field data and global chemical models."