Master of Science (MS)
Green leaf volatiles (GLVs) are a group of biogenic volatile organic compounds (BVOCs) released into the atmosphere by vegetation when plants undergo stress or mechanical damage. BVOCs produce secondary organic aerosol (SOA) in the gas phase; however, their oxidation as a source of SOA in the liquid phase has not been investigated. Once released into the atmosphere, water-soluble GLVs partition into atmospheric water phases such as fog, mist, dew or rain, where they are oxidized by hydroxyl radicals (ÿOH). Photochemical oxidation yields products that are higher in molecular weight, more polar, more oxygenated, and lower in vapor pressure. When the water droplets evaporate, the oxidation products are left behind as secondary organic aerosol. Methyl jasmonate (MeJa) and methyl salicylate, (MeSa), two GLVs typical of many plants, were reacted with hydroxyl radicals in the aqueous phase. The formed products were identified via high performance liquid chromatography paired with electrospray ionization mass spectrometry (HPLC-ESI/MS) and matched to potential reaction pathways for the oxidation of MeJa and MeSa with ÿOH. The oxidation products exhibit a higher molecular mass than the parent GLV compound due to dimerization and the addition of oxygen and hydroxyl groups. For MeJa, C13H20O4, C13H20O5, C13H22O5, C13H22O6 were found as oxidation products, whereas for MeSa, C8H8O4, C8H8O5, C16H14O6 were found. The estimated vapor pressures of these products are significantly (up to 5 orders of magnitude) less than those of the associated parent compounds and therefore, remain in the atmosphere as SOA after evaporation of the water droplet. The contribution of the identified oxidation products to SOA formation is estimated based on measured HPLC-ESI/MS response and compared to actual SOA mass yield measurements. Additionally, physico-chemical properties of the GLVs were measured, which give insight into GLV activity in the aqueous phase.
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Hansel, Amie Kathryn, "Reaction of green leaf volatiles as a source of secondary organic aerosols in fog droplets" (2013). LSU Master's Theses. 497.
Valsaraj, Kalliat T