22 Feb 2022
22 Feb 2022
Status: this preprint is currently under review for the journal ACP.

Chemical composition of secondary organic aerosol particles formed from mixtures of anthropogenic and biogenic precursors

Yunqi Shao1, Aristeidis Voliotis1, Mao Du1, Yu Wang1, Kelly Pereira3,a, Jacqueline Hamilton3, M. Rami Alfarra1,2,b, and Gordon McFiggans1 Yunqi Shao et al.
  • 1School of Earth and Environmental Science, University of Manchester, Manchester, M13, 9PL, UK
  • 2National Centre for Atmospheric Science
  • 3Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, YO105DD, UK
  • anow at: Department of Life and Environmental Sciences, Bournemouth University, Dorset, BH12 5BB, UK
  • bnow at: Environment & Sustainability Center, Qatar Environment & Energy Research Institute, Doha, Qatar

Abstract. A series of experiments were designed and conducted in the Manchester Aerosol Chamber (MAC) to study the photooxidation of single and mixed biogenic (isoprene and α-pinene) and anthropogenic (o-cresol) precursors in the presence of NOx and ammonium sulphate seed particles. Several online techniques (HR-TOF-AMS, Semi-Continuous GC-MS, NOx and O3 analyser) were coupled to the MAC to monitor the gas and particle mass concentrations. Secondary Organic Aerosol (SOA) particles were collected onto a quartz fibre filter at the end of each experiment and analysed using liquid chromatography ultra-high resolution mass spectrometry (LC-Orbitrap MS). The SOA particle chemical composition in single and mixed precursor systems was investigated using non-targeted accurate mass analysis of measurements in both negative and positive ionization modes, significantly reducing data complexity and analysis time, providing an more complete assessment of the chemical composition. This non-targeted analysis is not widely used in environmental science and never previously in atmospheric simulation chamber studies. Products from α-pinene were found to dominate the binary mixed α-pinene / isoprene system in terms of signal contributed and the number of particle components detected. Isoprene photooxidation was found to generate negligible SOA particle mass under the investigated experimental conditions and isoprene-derived products made a negligible contribution to particle composition in the α-pinene / isoprene system. No compounds uniquely found in this system contributed sufficiently to be reliably considered as a tracer compound for the mixture. Methyl-nitrocatechol isomers (C7H7NO4) and methyl-nitrophenol (C7H7NO3) from o-cresol oxidation made dominant contributions to the SOA particle composition in both the o-cresol / isoprene and o-cresol / α-pinene binary systems in negative ionization mode. In contrast, interactions in the oxidation mechanisms led to the formation of compounds uniquely found in the mixed o-cresol containing binary systems in positive ionization mode. C9H11NO and C8H8O10 made large signal contributions in the o-cresol / isoprene binary system. The SOA molecular composition in the o-cresol / α-pinene system in positive ionization mode is mainly driven by the large molecular weight compounds (e.g. C20H31NO4, and C20H30O3) uniquely found in the mixture. The SOA particle chemical composition formed in the ternary system is more complex. The molecular composition and signal abundance are both markedly similar to those in the single α-pinene system in positive ionization mode, with major contributions from o-cresol products in negative ionization mode.

Yunqi Shao 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-2022-127', Anonymous Referee #1, 14 Mar 2022
    • AC1: 'Reply on RC1', Yunqi Shao, 27 May 2022
    • AC3: 'Reply on RC1', Yunqi Shao, 27 May 2022
  • RC2: 'Comment on acp-2022-127', Anonymous Referee #2, 01 Apr 2022
    • AC2: 'Reply on RC2', Yunqi Shao, 27 May 2022
    • AC4: 'Reply on RC2', Yunqi Shao, 27 May 2022

Yunqi Shao et al.


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Short summary
This study explored the chemical properties of secondary organic aerosol (SOA) that formed from photooxidation of single and mixed biogenic and anthropogenic precursors. We showed that the SOA chemical properties in mixed vapour system are mainly affected by the higher yield precursor’s oxidation products, and products from cross-product formation. This study also identifies the potential tracer compounds in mixed vapour system that might use in SOA source attribution in future ambient studies.