Development of a detailed chemical mechanism (MCMv3.1) for the atmospheric oxidation of aromatic hydrocarbons

Abstract

Abstract. The Master Chemical Mechanism has been updated from MCMv3 to MCMv3.1 in order to take into account recent improvements in the understanding of aromatic photo-oxidation. Newly available kinetic and product data from the literature have been incorporated into the mechanism. In particular, the degradation mechanisms for hydroxyarenes have been revised following the observation of high yields of ring-retained products, and product studies of aromatic oxidation under relatively low NO x conditions have provided new information on the branching ratios to first generation products. Experiments have been carried out at the European Photoreactor (EUPHORE) to investigate key subsets of the toluene system. These results have been used to test our understanding of toluene oxidation, and, where possible, refine the degradation mechanisms. The evaluation of MCMv3 and MCMv3.1 using data on benzene, toluene, p-xylene and 1,3,5-trimethylbenzene photosmog systems is described in a companion paper, and significant model shortcomings are identified. Ideas for additional modifications to the mechanisms, and for future experiments to further our knowledge of the details of aromatic photo-oxidation are discussed.

General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) – integrating aerosol research from nano to global scales

“…Across a broad range of organic vapour and OA mass initialisations, the first four of the above metrics are predicted to fall in a relatively narrow range using the best available property estimation techniques. These metrics have been compared from absorptive partitioning predictions and literature-reported field measurements using output from the near-explicit MCM model (Bloss et al, 2005;Jenkin et al, 2003). Further comparison of this range with ambient measurements emerging from EUCAARI can be used to evaluate limitations with the equilibrium approach and discrepancies used to provide guidance for use of models incorporating the partitioning module developed.…”

Chemical aging of <i>m</i>-xylene secondary organic aerosol: laboratory chamber study

“…Products through three generations of oxidation are included. Primary oxidation products are those suggested by Birdsall et al (2010) and Zhao et al (2005) with product yields and further oxidative pathways as derived from the MCM (Jenkin et al, 2003;Bloss et al, 2005). Values of rate constants are listed in Table 3, and compounds represented in the model are given in Table 4.…”

Megacities and Atmospheric Pollution

“…326,327 The process of aromatic HC oxidation is becoming better understood, 328 -333 leading to MCM updates that have been evaluated against simulation chamber measurements. 296,334,335 The MM5 336,337 and CALMET 338 meteorological models generate three-dimensional wind fields from basic physics and from observations. CALMET is best suited to areas without complex terrain and with dense meteorological measurement networks.…”