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- Title
Chemistry and deposition in the Model of Atmospheric composition at Global and Regional scales using Inversion Techniques for Trace gas Emissions (MAGRITTEv1.0). Part A. Chemical mechanism.
- Authors
Müller, Jean-François; Stavrakou, Trissevgeni; Peeters, Jozef
- Abstract
A new chemical mechanism for the oxidation of biogenic volatile organic compounds (BVOCs) is presented and implemented in the Model of Atmospheric composition at Global and Regional scales using Inversion Techniques for Trace gas Emissions (MAGRITTE v1.0). With a total of 99 organic species and over 240 gas-phase reactions, 67 photodissociations and 7 heterogeneous reactions, the mechanism treats the chemical degradation of isoprene - its main focus - as well as acetaldehyde, acetone, methylbutenol and the family of monoterpenes. Regarding isoprene, the mechanism incorporates a state-of-the-art representation of its oxidation scheme accounting for all major advances put forward in recent theoretical and laboratory studies. The model and its chemical mechanism are evaluated against the suite of chemical measurements from the SEAC4RS (Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys) airborne campaign, demonstrating a good overall agreement for major isoprene oxidation products, although the aerosol hydrolysis of tertiary and non-tertiary nitrates remain poorly constrained. The comparisons for methylnitrate indicate a very low nitrate yield (< 3·10-4) in the CH3O2+NO reaction. The oxidation of isoprene, acetone and acetaldehyde by OH is shown to be a substantial source of enols and keto-enols, primarily through the photolysis of multifunctional carbonyls generated in their oxidation schemes. Oxidation of those enols by OH radicals constitutes a sizable source of carboxylic acids estimated at 8 Tg (HCOOH) yr-1 and 17 Tg(CH3COOH) yr-1, or ~25% of their global identified source. The ozonolysis of alkenes is found to be a smaller source of HCOOH (6 Tg HCOOH yr-1) than previously estimated, due to several factors including the strong deposition sink of hydroxymethylhydroperoxide (HMHP).
- Subjects
ATMOSPHERIC composition; TRACE gases; VOLATILE organic compounds
- Publication
Geoscientific Model Development Discussions, 2019, p1
- ISSN
1991-9611
- Publication type
Article
- DOI
10.5194/gmd-2018-316