Particulate Sulfate Formation from Uptake of SO2 onto Organic Aerosol
Abstract
Particulate matter is dominated by sulfate and organic aerosol (OA). Secondary formation of these components are often studied and modeled separately, but the observed correlations between their concentrations suggest synergistic reactions. Previous laboratory studies show that secondary organic aerosol (SOA) yields are higher when formed in the presence of SO2, but the mechanisms by which SO2 reacts are not known. In this work, we conducted bulk solution experiments of S(IV) oxidation by organic peroxides to investigate the kinetics and mechanisms of sulfate formation, and chamber experiments of SO2 uptake onto peroxide-containing OA.
The bulk reaction rate constants of SO2 with commercially available organic peroxides (cumene hydroperoxide, benzoyl peroxide and 2-butanone hydroperoxide) are quantified as a function of pH, and are shown to be similar to that with H2O2. Using isotopically labeled reagents and ion-mobility mass spectrometry (IMS-TOF), we show that organosulfates are formed from ROOH + SO2 at a substantial yield of 40%. This mechanism is unique from previously proposed pathways for organosulfate formation, which require inorganic sulfate as a reactant. Further experiments are conducted in the aerosol phase by generating SOA in the flow tube and measuring SO2 uptake onto SOA in the chamber. The uptake coefficients are measured for different SOA containing different types and amounts of organic peroxides. The update coefficients increased with increasing relative humidity, and varied between the order of 10-2 for multifunctional organic peroxides and 10-4. Organosulfate speciation using IMS-TOF is examined and compared to the backbone of SOA precursors. Our results will inform atmospheric models for understanding the importance of SO2 uptake in the atmosphere.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A51B..03C
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES