Reactivity of E-butenedial with the major atmospheric oxidants

Abstract

The degradation reactions of E-butenedial with OH and NO3 radicals and Cl atoms were investigated using a relative rate method. The experiments were carried out at ∼298 ± 1 K and an atmospheric pressure of N2 or synthetic air as the bath gas. Three different sampling/detection methods have been used for the study with Cl, OH and NO3: (1) Solid-Phase Microextraction and Gas Chromatography with Flame Ionization Detection (SPME/GC-FID), (2) ‘in situ’ with long-path Fourier Transform Infrared Spectroscopy (FTIR), and (3) Tenax solid adsorbent and Gas Chromatography with Mass Spectrometry (Tenax/GC–MS) as the detection system. The measured rate coefficients for E-butenedial (cm3 molecule−1 s−1) are as follows: (1.35 ± 0.29) × 10−10 for the Cl atom, (3.45 ± 0.34) × 10−11 for the OH radical and (1.70 ± 0.83) × 10−15 for the NO3 radical. For the reaction of Cl and NO3 these are the first rate coefficient data to be reported and in the case of OH the literature value is confirmed. This study confirms that the chemical structure of the organic substances does not influence on the reactivity with Cl, has a significant effect for OH reactions and is very important for NO3 reactions. Calculated atmospheric lifetimes are in the order of days for Cl and NO3 reactions and hours for OH. In the case of Cl atoms, a lifetime of 20 h is estimated in the early morning hours in urban coastal air. These shorter lifetimes imply that the degradation reactions of E-butenedial are of great importance because their reaction products are secondary pollutants that are involved in processes such as the formation of photochemical smog or peroxyacyl nitrates (PANs).