Abstract
Abstract. In order to enlarge our understanding of biomass burning plume chemistry, the OH-radical-initiated oxidation of 3-penten-2-one (3P2), identified in biomass burning emissions, and 2-hydroxypropanal (2HPr) was investigated at 298 ± 3 K and 990 ± 15 mbar in two atmospheric simulation chambers using long-path FTIR spectroscopy. The rate coefficient of 3P2 + OH was determined to be (6.2 ± 1.0) × 10−11 cm3 molec.−1 s−1 and the molar first-generation yields for acetaldehyde, methyl glyoxal, 2HPr, and the sum of peroxyacetyl nitrate (PAN) and CO2, used to determine the CH3C(O) radical yield, were 0.39 ± 0.07, 0.32 ± 0.08, 0.68 ± 0.27, and 0.56 ± 0.14, respectively, under conditions where the 3P2-derived peroxy radicals react solely with NO. The 2HPr + OH reaction was investigated using 3P2 + OH as a source of the α-hydroxyaldehyde adjusting the experimental conditions to shift the reaction system towards secondary oxidation processes. The rate coefficient was estimated to be (2.2 ± 0.6) × 10−11 cm3 molec.−1 s−1. Employing a simple chemical mechanism to analyse the temporal behaviour of the experiments, the further oxidation of 2HPr was shown to form methyl glyoxal, acetaldehyde, and CO2 with estimated yields of 0.27 ± 0.08, 0.73 ± 0.08, and 0.73 ± 0.08, respectively.
Highlights
Unsaturated ketones are of increasing interest as more sources for their atmospheric burden are uncovered
They are potentially formed in the atmospheric oxidation of terpenes involving OH radicals or O3 molecules. 3-Buten-2one is the most famous representative formed through the gas-phase oxidation of the most abundantly emitted non-methane hydrocarbons (NMHC), namely isoprene (Calvert et al, 2000)
Photolysis and dark reactions between 3P2 and the radical source were found to be negligible under all experimental conditions
Summary
Unsaturated ketones are of increasing interest as more sources for their atmospheric burden are uncovered They are potentially formed in the atmospheric oxidation of terpenes involving OH radicals or O3 molecules. Hatch et al (2017) identified 3P2 among various oxygenated species in the gas-phase biomass burning emissions of Chinese rice straw, Indonesian peat, and boughs of ponderosa pine and black spruce during the FLAME-4 campaign. They identified 2-methylpenta-1,3-diene (Hatch et al, 2017), which potentially yields 3P2 in the further gasphase oxidation. All these findings pinpoint 3P2 as a likely constituent of most biomass burning (BB) plumes
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