10 Jan 2022
10 Jan 2022
Status: a revised version of this preprint was accepted for the journal ACP.

Observations of gas-phase products from the nitrate radical-initiated oxidation of four monoterpenes

Michelia Dam1, Danielle C. Draper1, Andrey Marsavin2, Juliane L. Fry2, and James N. Smith1 Michelia Dam et al.
  • 1Department of Chemistry, University of California, Irvine, USA
  • 2Chemistry Department & Environmental Studies Program, Reed College, Portland, USA

Abstract. Chemical ionization mass spectrometry with nitrate reagent ion (NO3 CIMS) was used to investigate the products of nitrate radical (NO3) initiated oxidation of four monoterpenes in laboratory chamber experiments. α-Pinene, β-pinene, Δ-3-carene, and α-thujene were studied. The major gas-phase species produced in each system were distinctly different, showing the effect of monoterpene structure on the oxidation mechanism and further elucidated the contributions of these species to particle formation and growth. By comparing groupings of products based on ratios of elements in the general formula CwHxNyOz, the relative importance of specific mechanistic pathways (fragmentation, termination, radical rearrangement) can be assessed for each system. Additionally, the measured time series of the highly oxidized reaction products provide insights into the ratio of relative production and loss rates of the high molecular weight products of the Δ-3-carene system. Measured effective O : C ratio of reaction products were anti-correlated to new particle formation intensity and number concentration for each system; however, monomer : dimer ratio of products was positively correlated. Gas phase yields of oxidation products measured by NO3 CIMS correlated with particle number concentrations for each monoterpene system, with the exception of α-thujene, which produced a considerable amount of low volatility products but no particles. Species-resolved wall loss was measured with NO3 CIMS and found to be highly variable among oxidized reaction products in our stainless steel chamber.

Michelia Dam et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-1020', Anonymous Referee #1, 01 Feb 2022
  • RC2: 'Comment on acp-2021-1020', Anonymous Referee #2, 08 Feb 2022
  • AC1: 'Comment on acp-2021-1020', James Smith, 12 Apr 2022

Michelia Dam et al.

Michelia Dam et al.


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Short summary
We performed chamber experiments to measure the composition of the gas phase reaction products of nitrate radical initiated oxidation of four monoterpenes. Total organic yield, effective oxygen-to-carbon ratio, and dimer-to-monomer ratio correlated with observed particle formation for the monoterpene systems with some exceptions. The d-carene system produced the most particles, followed by b-pinene, with the a-pinene and a-thujene systems producing no particles.