Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation - Archive ouverte HAL
Journal Articles Journal of Physical Chemistry A Year : 2017

Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation

Chiara Giorio
Anne Monod
Helen Langley Dewitt
  • Function : Author
Arthur T Zielinski
  • Function : Author

Abstract

Aerosol-cloud interaction contributes to the largest uncertainties in the estimation and interpretation of the Earth's changing energy budget. The present study explores experimentally the impacts of water condensation-evaporation events, mimicking processes occurring in atmospheric clouds, on the molecular composition of secondary organic aerosol (SOA) from the photooxidation of methacrolein. A range of on-and off-line mass spectrometry techniques were used to obtain a detailed chemical characterization of SOA formed in control experiments in dry conditions, in triphasic experiments simulating gas-particle-cloud droplet interactions (starting from dry conditions and from 60% relative humidity (RH)), and in bulk aqueous-phase experiments. We observed that cloud events trigger fast SOA formation accompanied by evaporative losses. These evaporative losses decreased SOA concentration in the simulation chamber by 25−32% upon RH increase, while aqueous SOA was found to be metastable and slowly evaporated after cloud dissipation. In the simulation chamber, SOA composition measured with a high-resolution time-offlight aerosol mass spectrometer, did not change during cloud events compared with high RH conditions (RH > 80%). In all experiments, off-line mass spectrometry techniques emphasize the critical role of 2-methylglyceric acid as a major product of isoprene chemistry, as an important contributor to the total SOA mass (15−20%) and as a key building block of oligomers found in the particulate phase. Interestingly, the comparison between the series of oligomers obtained from experiments performed under different conditions show a markedly different reactivity. In particular, long reaction times at high RH seem to create the conditions for aqueous-phase processing to occur in a more efficient manner than during two relatively short cloud events.
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hal-04299684 , version 1 (22-11-2023)

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Chiara Giorio, Anne Monod, Lola Brégonzio-Rozier, Helen Langley Dewitt, Mathieu Cazaunau, et al.. Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation. Journal of Physical Chemistry A, 2017, 121 (40), pp.7641 - 7654. ⟨10.1021/acs.jpca.7b05933⟩. ⟨hal-04299684⟩
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