21 Feb 2023
 | 21 Feb 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Daytime Isoprene Nitrates Under Changing NOx and O3

Alfred W. Mayhew, Peter M. Edwards, and Jacqueline F. Hamilton

Abstract. Organonitrates are important species in the atmosphere due to their impacts on NOx, HOx, and O3 budgets, and their potential to contribute to secondary organic aerosol (SOA) mass. This work presents a steady-state modelling approach to assess the impacts of changes in NOx and O3 concentrations on the organonitrates produced from isoprene oxidation. The diverse formation pathways to isoprene organonitrates dictate the responses of different groups of organonitrates to changes in O3 and NOx. For example, organonitrates predominantly formed from the OH-initiated oxidation of isoprene favour formation under lower ozone and moderate NOx concentrations, whereas organonitrates formed via day-time NO3 oxidation show the highest formation under high O3 concentrations with little dependence on NOx concentrations. Investigating the response of total organonitrates reveals complex and non-linear behaviour with implications that could inform expectations of changes to organonitrate concentrations as efforts are made to reduce NOx and O3 concentrations, including a region of NOx-O3 space where total organonitrate concentration is relatively insensitive to changes in NOx and O3. These conclusions are further contextualised by estimating the volatility of the isoprene organonitrates revealing the potential for high concentrations of low volatility species under high ozone conditions.

Alfred W. Mayhew et al.

Status: open (until 04 Apr 2023)

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  • RC1: 'Comment on egusphere-2023-226', Anonymous Referee #1, 20 Mar 2023 reply

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 investigates modelled changes to day time isoprene nitrate concentrations resulting from changes in NOx and O3. The results highlight the complex, non-linear chemistry of this group of species under typical conditions for megacities such as Beijing, with many species showing increased concentrations when NOx is decreased and/or ozone is increased.