Preprints
https://doi.org/10.5194/acp-2021-758
https://doi.org/10.5194/acp-2021-758

  14 Sep 2021

14 Sep 2021

Review status: this preprint is currently under review for the journal ACP.

Evaluation of the daytime tropospheric loss of 2-methylbutanal

María Asensio1,2, María Antiñolo1,2,a, Sergio Blázquez2, José Albaladejo1,2, and Elena Jiménez1,2 María Asensio et al.
  • 1Instituto de Investigación en Combustión y Contaminación Atmosférica, Universidad de Castilla-La Mancha, Camino de Moledores s/n, Ciudad Real, 13071, Spain
  • 2Departamento de Química Física, Universidad de Castilla-La Mancha, Avda. Camilo José Cela 1B, Ciudad Real, 13071, Spain
  • acurrently at: Escuela de Ingeniería Industrial y Aeroespacial. Universidad de Castilla-La Mancha. Avenida Carlos III s/n. Real Fábrica de Armas. 45071 Toledo, Spain

Abstract. Saturated aldehydes, e.g. 2-methylbutanal (2MB, CH3CH2CH(CH3)C(O)H), are emitted into the atmosphere by several biogenic sources. The first step in the daytime atmospheric degradation of 2MB involves gas-phase reactions initiated by hydroxyl (OH) radicals, chlorine (Cl) atoms and/or sunlight. In this work, we report the rate coefficients for the gas-phase reaction of 2MB with OH (kOH) and Cl (kCl) together with the photolysis rate coefficient (J) in the ultraviolet solar actinic region in Valencia (Spain) at different times of the day. The temperature dependence of kOH was described in the 263–353 K range by the following Arrhenius expression: kOH(T)=(8.88±0.41)×10-12 exp[(331±14)/T] cm3 molecule-1 s-1. At 298 K, the reported kOH and kCl are (2.68±0.07)×10-11 cm3 molecule-1 s-1 and (2.16±0.16)×10-11 cm3 molecule-1 s-1. Identification and quantification of the gaseous products of the Cl-reaction and those from the photodissociation of 2MB were carried out in a smog chamber by different techniques (Fourier transform infrared spectroscopy, proton transfer time-of-flight mass spectrometry, and gas chromatography coupled to mass spectrometry). The formation and size distribution of secondary organic aerosols formed in the Cl-reaction was monitored by a fast mobility particle sizer spectrometer. A discussion on the relative importance of the first step in the daytime atmospheric degradation of 2MB is presented together with the impact of the degradation products in marine atmospheres.

María Asensio et al.

Status: open (until 26 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

María Asensio et al.

María Asensio et al.

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Short summary
The diurnal atmospheric degradation of 2-methylbutanal, 2MB, emitted by sources like vegetation or poultry industry is evaluated in this work. Sunlight and oxidants like hydroxyl (OH) radicals and chlorine (Cl) atoms initiate this degradation. Measurements of how fast 2MB is degraded and what products are generated are presented. The lifetime of 2MB is around 1 h at noon, when the OH reaction dominates. Thus, 2MB will not be transported to long distances, affecting only local air quality.
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