Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation

Giorio, Chiara and Monod, Anne and Brégonzio-Rozier, Lola and DeWitt, Helen Langley and Cazaunau, Mathieu and Temime-Roussel, Brice and Gratien, Aline and Michoud, Vincent and Pangui, Edouard and Ravier, Sylvain and Zielinski, Arthur T. and Tapparo, Andrea and Vermeylen, Reinhilde and Claeys, Magda and Voisin, Didier and Kalberer, Markus and Doussin, Jean-François. (2017) Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation. Journal of Physical Chemistry A, 121 (40). pp. 7641-7654.

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Official URL: https://edoc.unibas.ch/81351/

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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-of flight 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.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geowissenschaften > Atmospheric Sciences (Kalberer)
UniBasel Contributors:Kalberer, Markus
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:13 Apr 2021 09:14
Deposited On:13 Apr 2021 09:14

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