Preprints
https://doi.org/10.5194/acp-2022-333
https://doi.org/10.5194/acp-2022-333
 
18 May 2022
18 May 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Evaluation of Isoprene Nitrate Chemistry in Detailed Chemical Mechanisms

Alfred W. Mayhew1, Ben H. Lee2, Joel A. Thornton2, Thomas J. Bannan3, James Brean4, James R. Hopkins1,5, James D. Lee1,5, Beth S. Nelson1, Carl Percival3, Andrew R. Rickard1,5, Marvin D. Shaw1,5, Peter M. Edwards1, and Jaqueline F. Hamilton1 Alfred W. Mayhew et al.
  • 1Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, Heslington, York, UK
  • 2Department of Atmospheric Sciences, University of Washington Seattle, Washington 98195, USA
  • 3School of Earth and Environmental Sciences, University of Manchester, Manchester, UK
  • 4School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, U.K.
  • 5National Centre for Atmospheric Science, University of York, York, UK

Abstract. Isoprene nitrates are important chemical species in the atmosphere which contribute to the chemical cycles that form ozone and secondary organic aerosol (SOA) with implications for climate and air quality. Accurate chemical mechanisms are important for the prediction of the atmospheric chemistry of species such as isoprene nitrates in chemical models. In recent years, studies into the chemistry of isoprene nitrates have resulted in the development of a range of mechanisms available for use in the simulation of atmospheric isoprene oxidation. This work uses a 0-D chemical box-model to assess the ability of three chemically detailed mechanisms to predict the observed diurnal profiles of four groups of isoprene-derived nitrates in the summertime in the Chinese Megacity of Beijing. An analysis of modelled C5H9NO5 isomers, including isoprene hydroperoxy nitrate (IPN) species, highlights the significant contribution of non-IPN species to the C5H9NO5 measurement, including the potentially large contribution of nitrooxy hydroxyepoxide (INHE). The changing isomer distribution of isoprene hydroxy nitrates (IHN) derived from OH-initiated and NO3-initiated chemistry is discussed, as is the importance of up-to-date alkoxy radical chemistry for the accurate prediction of isoprene carbonyl nitrate (ICN) formation. All mechanisms reasonably reproduced C4H7NO5 as predominately formed from the major isoprene oxidation products, methyl vinyl ketone (MVK) and methacrolein (MACR). This work explores the current capability of existing chemical mechanisms to accurately represent isoprene nitrate chemistry in urban areas significantly impacted by anthropogenic and biogenic chemical interactions, suggests considerations to be taken when applying these mechanisms to ambient scenarios, and makes some proposals for the future development of isoprene mechanisms.

Alfred W. Mayhew et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Reviewer comment on "Evaluation of Isoprene Nitrate Chemistry in Detailed Chemical Mechanisms"', Anonymous Referee #1, 23 May 2022
  • RC2: 'Comment on acp-2022-333', Anonymous Referee #2, 15 Jun 2022
  • AC1: 'Response to Reviewers: acp-2022-333', Alfred Mayhew, 14 Sep 2022

Alfred W. Mayhew et al.

Alfred W. Mayhew et al.

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Short summary
Isoprene nitrates are chemical species commonly found in the atmosphere that are important for their impacts on air quality and climate. This paper compares 3 different representations of the chemistry of isoprene nitrates in computational models. We highlight that while all of the models generally represented isoprene nitrates well, there were cases where the choice of chemistry included in the models has significant impacts on the concentration and composition of the modelled nitrates.
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