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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-1095
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
05 Dec 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
The atmospheric impacts of monoterpene ozonolysis on global stabilised Criegee intermediate budgets and SO2 oxidation: experiment, theory and modelling
Mike J. Newland1,3, Andrew R. Rickard2,3, Tomás Sherwen3, Mathew J. Evans2,3, Luc Vereecken4,5, Amalia Muñoz6, Milagros Ródenas6, and William J. Bloss1 1University of Birmingham, School of Geography, Earth and Environmental Sciences, Birmingham, UK
2National Centre for Atmospheric Science (NCAS), University of York, York, UK
3Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, UK
4Max Planck Institute for Chemistry, Atmospheric Sciences, Hahn-Meitner-Weg 1, Mainz, Germany
5Institute for Energy and Climate Research, Forschungszentrum Jülich, Germany
6Fundación CEAM, EUPHORE Laboratories, Avda/Charles R. Darwin 14 . Parque Tecnologico, Valencia, Spain
Abstract. The gas-phase reaction of alkenes with ozone is known to produce stabilised Criegee intermediates (SCIs). These biradical/zwitterionic species have the potential to act as atmospheric oxidants for trace pollutants such as SO2, enhancing the formation of sulfate aerosol with impacts on air quality and health, radiative transfer and climate. However, the importance of this chemistry is uncertain as a consequence of limited understanding of the abundance and atmospheric fate of SCIs. In this work we apply experimental, theoretical and numerical modelling methods to quantify the atmospheric impacts, abundance, and fate, of the structurally diverse SCIs derived from the ozonolysis of monoterpenes, the second most abundant group of unsaturated hydrocarbons in the atmosphere. We have investigated the removal of SO2 by SCI formed from the ozonolysis of three monoterpenes (-pinene, -pinene and limonene) in the presence of varying amounts of water vapour in large-scale simulation chamber experiments. The SO2 removal displays a clear dependence on water vapour concentration, but this dependence is not linear across the range of [H2O] explored. At low [H2O] a strong dependence of SO2 removal on [H2O] is observed, while at higher [H2O] this dependence becomes much weaker. This is interpreted as being caused by the production of a variety of structurally (and hence chemically) different SCI in each of the systems studied, each displaying different rates of reaction with water and of unimolecular rearrangement/decomposition. The determined rate constants, k(SCI+H2O), for those SCI that react primarily with H2O range from 4–310 × 10−15 cm3 s−1. For those SCI that predominantly react unimolecularly, determined rates range from 130–240 s−1. These values are in line with previous results for the (analogous) stereo-specific SCI system of syn/anti-CH3CHOO. The experimental results are interpreted through theoretical studies of the SCI unimolecular reactions and bimolecular reactions with H2O, characterised for -pinene and -pinene at the M06-2X/aug-cc-pVTZ level of theory. The theoretically derived rates agree with the experimental results within the uncertainties. A global modelling study, applying the experimental results within the GEOS-Chem chemical transport model, suggests that > 98 % of the total monoterpene derived global SCI burden is comprised of SCI whose structure determines that they react slowly with water, and whose atmospheric fate is dominated by unimolecular reactions. Seasonally averaged boundary layer concentrations of monoterpene-derived SCI reach up to 1.2 × 104 cm−3 in regions of elevated monoterpene emissions in the tropics. Reactions of monoterpene derived SCI with SO2 account for < 1 % globally but may account for up to 50 % of the gas-phase SO2 removal over areas of tropical forests, with significant localised impacts on the formation of sulfate aerosol, and hence the lifetime and distribution of SO2.

Citation: Newland, M. J., Rickard, A. R., Sherwen, T., Evans, M. J., Vereecken, L., Muñoz, A., Ródenas, M., and Bloss, W. J.: The atmospheric impacts of monoterpene ozonolysis on global stabilised Criegee intermediate budgets and SO2 oxidation: experiment, theory and modelling, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-1095, in review, 2017.
Mike J. Newland et al.
Mike J. Newland et al.
Mike J. Newland et al.

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Short summary
Stabilised Criegee intermediates (SCI) are formed in the reaction of alkenes with ozone, both ubiquitous throughout the troposphere. We determine the fate and global distribution of SCI from monoterpene (major biogenic emission) ozonolysis. One major fate of SCI is reaction with H2O, but for a fraction of SCI, unimolecular reactions dominate. Concentrations of such SCI are high enough regionally to play a key role in the conversion of sulfur dioxide to aerosol, affecting air quality and climate.
Stabilised Criegee intermediates (SCI) are formed in the reaction of alkenes with ozone, both...
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