06 Jan 2022
06 Jan 2022
Status: this preprint is currently under review for the journal ACP.

Chamber investigation of the formation and transformation of secondary organic aerosol in mixtures of biogenic and anthropogenic volatile organic compounds

Aristeidis Voliotis1,, Mao Du1,, Yu Wang1,, Yunqi Shao1,, M. Rami Alfarra1,2,a, Thomas J. Bannan1, Dawei Hu1, Kelly L. Pereira3, Jaqueline F. Hamilton3, Mattias Hallquist4, Thomas F. Mentel5, and Gordon McFiggans1 Aristeidis Voliotis et al.
  • 1Centre for Atmospheric Science, Department of Earth and Environmental Sciences, School of Natural Sciences, University of Manchester, Manchester, M13 9PL, UK
  • 2National Centre for Atmospheric Science (NCAS), University of Manchester, Manchester, M13 9PL, UK
  • 3Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, YO10 5DD, UK
  • 4Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, Gothenburg SE-412 96, Sweden
  • 5Institut für Energie und Klimaforschung, IEK-8, Forschungszentrum Jülich, Jülich, Germany
  • anow at: Environment & Sustainability Center, Qatar Environment & EnergyResearch Institute, Doha, Qatar
  • These authors contributed equally to this work.

Abstract. A comprehensive investigation of the photochemical secondary organic aerosol (SOA) formation and transformation in mixtures of anthropogenic (o-cresol) and biogenic (α-pinene and isoprene) volatile organic compound (VOC) precursors in the presence of NOx and inorganic seed particles was conducted. Initial iso-reactivity was used to enable direct comparison across systems, adjusting the initial reactivity of the systems towards the assumed dominant oxidant (OH). Comparing experiments conducted in single precursor systems at various initial reactivity levels (referenced to a nominal base case VOC reactivity) and their binary and ternary mixtures, we show that the molecular interactions from the mixing of the precursors can be investigated and discuss limitations in their interpretation. The observed average SOA yields in descending order were found for the α-pinene (32 ± 7 %), α-pinene/o-cresol (28 ± 9 %), α-pinene at ½ initial reactivity (21 ± 5 %), α-pinene/isoprene (16 ± 1 %), α-pinene at ⅓ initial reactivity (15 ± 4 %), o-cresol (13 ± 3 %), α-pinene/o-cresol/isoprene (11 ± 4%), o-cresol at ½ initial reactivity (11 ± 3 %), o-cresol/isoprene (6 ± 2 %) and isoprene systems (0 ± 0 %). We find a clear suppression of the SOA yield from α-pinene when it is mixed with isoprene, whilst the addition of isoprene to o-cresol may enhance the mixture’s SOA formation potential, however, the difference was too small to be unequivocal. The α-pinene/o-cresol system yield appeared to be increased compared to that calculated based on the additivity, whilst in the α-pinene/o-cresol/isoprene system the measured and predicted yield were comparable. However, in mixtures where more than one precursor contributes to the SOA mass it is unclear whether changes in the SOA formation potential are attributable to physical or chemical interactions, since the reference basis for the comparison is complex. Online and offline chemical composition and SOA particle volatility, water uptake and “phase” behaviour measurements that were used to interpret the SOA formation and behaviour are introduced and detailed elsewhere.

Aristeidis Voliotis 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-2021-1080', Anonymous Referee #1, 18 Feb 2022
  • RC2: 'Comment on acp-2021-1080', Anonymous Referee #2, 22 Feb 2022
  • RC3: 'Comment on acp-2021-1080', Anonymous Referee #3, 01 Mar 2022

Aristeidis Voliotis et al.

Aristeidis Voliotis et al.


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Short summary
Mixing experiments are crucial and highly beneficial for our understanding on atmospheric chemical interactions. However, the interpretation quickly becomes complex and both the experimental design and evaluation needs to be scrutinised carefully. Advanced online and offline compositional measurements can reveal substantial additional information to aid in the interpretation of yield data, including components uniquely found in mixtures and property changes in the SOA formed from mixtures of VOC.