Preprints
https://doi.org/10.5194/egusphere-2023-1425
https://doi.org/10.5194/egusphere-2023-1425
24 Jul 2023
 | 24 Jul 2023

Impact of temperature on the role of Criegee intermediates andperoxy radicals in dimers formation from β-pinene ozonolysis

Yiwei Gong, Feng Jiang, Yanxia Li, Thomas Leisner, and Harald Saathoff

Abstract. Stabilized Criegee intermediates (SCIs) and organic peroxy radicals (RO2), as important reactive species in the atmosphere, are critical in oxidation processes and secondary organic aerosol (SOA) formation. However, the influence of temperature on these reactive intermediates and the corresponding reaction mechanisms in SOA formation are still not well defined. In this study, through utilizing SCIs scavengers and regulating [HO2]/[RO2] from ~0.3 to ~1.9, the roles of RO2 and SCIs in SOA formation were investigated at 298 K, 273 K, and 248 K, respectively, particularly for dimers formation in β-pinene ozonolysis. The SOA yield increased by 21 % from 298 K to 273 K, while further reducing the temperature to 248 K led to a decrease of 40 % in SOA yield. This cannot be explained by partitioning or wall losses and is attributed to the temperature impact on rate coefficients and product branching ratios of some specific reactions. Both changing [HO2]/[RO2] and scavenging SCIs significantly affect SOA yield and composition. SCIs reactions accounted for more than 40 % of dimers and SOA mass formation for all temperatures, and the dimers formed from the SCIs channel did not show obvious suppression at subzero temperature. Increasing [HO2]/[RO2] inhibited dimers and SOA formation with a higher sensitivity at lower temperatures. Compared to low [HO2]/[RO2] condition, the dimers abundance at high [HO2]/[RO2] decreased by about 31 % at 298 K and 70 % at 248 K. The correlation between dimers and [RO2]2 demonstrates that RO2 cross reactions cannot explain the impact of RO2 concentration on dimers formation at low temperatures. The specific impact of [HO2]/[RO2] on SCIs-controlled dimers at lower temperatures indicates the influence of changing [HO2]/[RO2] on dimers formed from the reaction of C9-SCIs and RO2 with a negative temperature dependence. The higher contribution of this SCIs reaction channel to dimers at lower temperatures is confirmed by chemical kinetic modeling. The dimers formed from C9-SCIs reaction with RO2 were estimated to decrease by 61 % at high [HO2]/[RO2] compared to low [HO2]/[RO2] at 248 K, providing explanations for the observed [HO2]/[RO2] impact. The high reactivity and substantial contribution to SOA of β-pinene-derived SCIs at lower temperatures observed in this study suggest that monoterpene-derived SCIs reactions should be accounted for in describing colder regions of the atmosphere.

Yiwei Gong et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1425', Anonymous Referee #1, 13 Aug 2023
  • RC2: 'Comment on egusphere-2023-1425', Anonymous Referee #2, 28 Aug 2023
  • RC3: 'Comment on egusphere-2023-1425', Anonymous Referee #3, 31 Aug 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1425', Anonymous Referee #1, 13 Aug 2023
  • RC2: 'Comment on egusphere-2023-1425', Anonymous Referee #2, 28 Aug 2023
  • RC3: 'Comment on egusphere-2023-1425', Anonymous Referee #3, 31 Aug 2023

Yiwei Gong et al.

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Short summary
This study investigates the role of the important atmospheric reactive intermediates in the formation of dimers and aerosol in monoterpene ozonolysis at different temperatures. Through conducting a series of chamber experiments and utilizing chemical kinetic and aerosol dynamic models, the SOA formation processes are better described, especially for colder regions. The results can be used to improve the chemical mechanism modeling of monoterpenes and SOA parameterization in transport models.