30 May 2022
30 May 2022
Status: this preprint is currently under review for the journal ACP.

The influence of the addition of a reactive low SOA yield VOC on the volatility of particles formed from photo-oxidation of anthropogenic – biogenic mixtures

Aristeidis Voliotis1, Mao Du1, Yu Wang1, Yunqi Shao1, Thomas J. Bannan1, Michael Flynn1, Spyros N. Pandis2,3, Carl J. Percival4, M. Rami Alfarra1,5, and Gordon McFiggans1 Aristeidis Voliotis et al.
  • 1Centre for Atmospheric Science, Department of Earth and Environmental Science, School of Natural Sciences, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom
  • 2Department of Chemical Engineering, University of Patras, Patras, Greece
  • 3Institute of Chemical Engineering Sciences, FORTH, Patras, Greece
  • 4NASA Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
  • 5National Centre for Atmospheric Science, Department of Earth and Environmental Science, School of Natural Sciences, The University of Manchester, Oxford Road, M13 9PL, Manchester, United Kingdom

Abstract. In this study, we investigate the influence of isoprene on the volatility of secondary organic aerosol (SOA) formed during the photo-oxidation of mixtures of anthropogenic and biogenic precursors. The SOA particle volatility was quantified using two independent experimental techniques (use of a thermal denuder and FIGAERO-CIMS) in mixtures of α-pinene/isoprene, o-cresol/isoprene and α-pinene/o-cresol/isoprene. Single-precursor experiments at various initial concentrations and results from previous α-pinene/o-cresol experiments were used as reference. The oxidation of isoprene did not result in the formation of detectable SOA mass in single-precursor experiments, however isoprene-derived products appeared in mixed systems, likely due to the increase in the total absorptive mass. Addition of isoprene resulted in mixture-dependent influence on the SOA particle volatility. Isoprene made no major change to the volatility of α-pinene SOA particles though changes in the SOA particle composition were observed, with volatility predicted reasonably based on the additivity. Isoprene addition increased o-cresol SOA particle volatility by ~5/15 % of the total mass/signal, respectively, indicating a potential to increase the overall volatility that cannot be predicted based on the additivity. The addition of isoprene to the α-pinene/o-cresol system (i.e., α-pinene/o-cresol/isoprene) resulted in slightly less-volatile particles than those measured in the α-pinene/o-cresol systems. The measured volatility in the α-pinene/o-cresol/isoprene system had ~6 % higher LVOC mass/signal compared to that predicted assuming additivity with a correspondingly lower SVOC fraction. This suggests that any effects that could increase the SOA volatility from the addition of isoprene are likely outweighed from the formation of lower volatility compounds in more complex anthropogenic-biogenic precursor mixtures. Detailed chemical composition measurements support the measured volatility distribution changes and showed an abundance of unique-to-the-mixture products appearing in all the mixed systems accounting for around 30−40 % of the total particle phase signal. Our results demonstrate that the SOA particle volatility and its prediction can be affected by the interactions of the oxidised products in mixed precursor systems and further mechanistic understanding is required to improve their representation in chemical transport models.

Aristeidis Voliotis et al.

Status: open (until 11 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-312', Anonymous Referee #2, 20 Jun 2022 reply
  • RC2: 'Comment on acp-2022-312', Anonymous Referee #1, 28 Jun 2022 reply

Aristeidis Voliotis et al.

Aristeidis Voliotis et al.


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Short summary
The addition of a low-yield precursor to the reactive mixture of aVOC and bVOC can increase or decrease the SOA volatility that is system-dependent. Therefore, the SOA volatility of the mixtures cannot always be predicted based on the additivity. In complex mixtures the formation of lower volatility products likely outweighs the formation of products with higher volatility. The unique products of each mixture are contributing significantly to the signal, suggesting interactions can be important.