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Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 27 Mar 2019

Submitted as: research article | 27 Mar 2019

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Chemistry and Physics (ACP).

Observations of Highly Oxidised Molecules and Particle Nucleation in the Atmosphere of Beijing

James Brean1, Roy M. Harrison1,3, Zongbo Shi1, David C. S. Beddows1, W. Joe F. Acton2, and C. Nicholas Hewitt2 James Brean et al.
  • 1Division of Environmental Health and Risk Management, School of Geography, Earth and Environmental Sciences University of Birmingham Edgbaston, Birmingham B15 2TT, UK
  • 2Lancaster Environment Centre Lancaster University, Lancaster LA1 4YQ, UK
  • 3Department of Environmental Sciences/Center of Excellence in Environmental Studies, King Abdulaziz University, P.O. Box 80203, Jeddah, 21589, Saudi Arabia

Abstract. Particle nucleation is one of the main sources of atmospheric particulate matter by number, with new particles having great relevance for human health and climate. Highly oxidised multifunctional organic molecules (HOMs) have been recently identified as key constituents in the growth, and, sometimes, in initial formation of new particles. While there have been many studies of HOMs in atmospheric chambers, flow tubes and clean environments, analyses of data from polluted environments are scarce. Here, measurements of HOMs and particle size distributions down to small molecular clusters are presented alongside VOC and trace gas data from a campaign in Beijing. Many gas phase HOMs have been characterised and their temporal trends and behaviours analysed in the context of new particle formation. The HOMs identified have a comparable degree of oxidation to those seen in other, cleaner, environments, likely due to an interplay between the higher temperatures facilitating rapid hydrogen abstractions and the higher concentrations of NOx and other RO2. terminators ending the autoxidation sequence more rapidly. Our data indicate that alkylbenzenes, monoterpenes, and isoprene are important precursor VOCs for HOMs in Beijing. Many of the C5 and C10 compounds derived from isoprene and monoterpenes have a slightly greater degree of average oxidation state of carbon compared to those from other precursors. Most HOMs except for large dimers have daytime peak concentrations, indicating the importance of OH. chemistry in the formation of HOMs, as O3 is lower on the days with higher HOM concentrations; similarly, VOC concentrations are lower on the days with higher HOM concentrations. The daytime peaks of HOMs coincide with the growth of freshly formed new particles, and their initial formation coincides with the peak in sulphuric acid vapours, suggesting that the nucleation process is sulphuric acid-dependent, with HOMs contributing to subsequent particle growth.

James Brean et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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James Brean et al.
Data sets

HOMS measured by APi-ToF in Beijing J. Brean, R. M. Harrison, Z. Shi, D. C. S. Beddows, W. J. Action, and C. N. Hewitt

James Brean et al.
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Short summary
Measurements of highly oxidised molecules measured during a summer campaign in Beijing are presented. These molecules represent an intermediary between gas phase chemicals from which they are formed and airborne particles which form from them. Conclusions are drawn as to the factors affecting the formation of new particles within the Beijing atmosphere.
Measurements of highly oxidised molecules measured during a summer campaign in Beijing are...