<p>The biogenic oxygenated volatile compound 2-methylbutanal (2MB) is emitted into the low atmosphere from several natural sources such as microbiological processes, wildland fires, or emissions from vegetation<sup>1</sup>. Moreover, some industrial operations also generate 2MB<sup>2</sup>. During the day, the oxidation of 2MB can be initiated by sunlight, hydroxyl (OH) radicals or chlorine (Cl) atoms in marine atmospheres. Up to date, gas-phase kinetics of OH with 2MB has only been studied at room temperature<sup>3</sup>. The photolysis rate coefficients (<em>J</em>) of 2MB initiated by sunlight have also been reported<sup>4</sup>. However, there is no available data for the reaction of Cl atoms with 2MB and the photolysis products.</p><p>In this work, the photolysis rate coefficient (<em>J</em>) of 2MB has been measured using a solar simulator in a Pyrex cell coupled to a Fourier Transform Infrared (FTIR) spectrometer to monitor the loss of 2MB. Moreover, the gas-phase kinetics of the reaction of 2MB with Cl (<em>k</em><sub>Cl</sub>) and OH (<em>k</em><sub>OH</sub>) have been investigated to evaluate the contribution of these homogeneous degradation routes to the total loss of 2MB in the atmosphere. All the kinetic experiments were carried out under free-NO<sub>x</sub> conditions (simulating a clean atmosphere). Regarding the relative kinetic study on the Cl-reaction, an atmospheric simulation chamber coupled to a FTIR spectrometer was used at 298 K and 760 Torr <sup>5</sup> of air, whereas for the absolute kinetics of the OH-reaction, <em>k</em><sub>OH</sub> was determined as a function of temperature and pressure (T = 263-353 K and P = 50-600 Torr of helium) by using a pulsed laser photolysis-laser induced fluorescence system<sup>6</sup>. Finally, in addition to FTIR, gas chromatography coupled to mass spectrometry and proton transfer time-of-flight mass spectrometry were used to detect the gas-phase reaction products when 2MB was exposed to Cl and sunlight. The atmospheric implications will be discussed in terms of lifetimes and reactions products.</p><p><strong>REFERENCES:</strong> <strong>1</strong>. Szwajkowska-Michale, L., Busko, M., Lakomy, P., and Perkowski, J.: Determination of profiles of volatile metabolites produced by Trametes versicolor isolates antagonistic towards Armillaria spp. Sylwan. <strong>2018</strong>, 162, 499&#8211;508. <strong>2. </strong>Kolar, P.; Kastner, J. R. Low-Temperature Catalytic Oxidation of Aldehyde Mixtures Using Wood Fly Ash: Kinetics, Mechanism, and Effect of Ozone. Chemosphere. <strong>2010</strong>, 78 (9), 1110&#8211;1115. <strong>3. </strong>D&#8217;Anna, B.; Andresen, O.; Gefen, Z. and Nielsen, C.J.: Kinetic study of OH and NO<sub>3</sub> radical reactions with 14 aliphatic aldehydes. Phys.Chem.Chem.Phys. <strong>2001</strong>, 3, 3057-3063. <strong>4. </strong>Wenger, J.C.: Chamber Studies on the Photolysis of Aldehydes. Environmental Simulation Chambers: Application to Atmospheric Chemical Processes. <strong>2006. </strong>Nato Science Series: IV: Earth and Environmental Science, vol 62. Springer, Dordrecht. <strong>5. </strong>Anti&#241;olo, M.; Asensio, M.; Albadalejo, J. and Jim&#233;nez E.: Gas-Phase Reaction of trans-2-methyl-2-butenal with Cl: Kinetics, Gaseous Products, and SOA Formation. Atmosphere <strong>2020</strong>, 11 (7), 715. <strong>6. </strong>Bl&#225;zquez, S.; Anti&#241;olo, M.; Nielsen, O. J.; Albadalejo, J. and Jim&#233;nez, E.: Reaction kinetics of (CF<sub>3</sub>)<sub>2</sub>CFCN with OH radicals as a function of temperature (278-358 K): A good replacement for greenhouse SF<sub>6</sub>? Chem.Phys.Lett. <strong>2017</strong>, 687, 297-302.</p>
Evaluation of the daytime tropospheric loss of 2-methylbutanal