AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Secondary Organic Material Formation from Isoprene Photooxidation Products Induced by Particle Phase Reactions
MIKINORI KUWATA, Yingjun Liu, Karena McKinney, Scot Martin, Harvard University
Abstract Number: 106 Working Group: Aerosol Chemistry
Abstract Particle phase reactions have been considered as one of the important mechanisms for secondary organic material (SOM) formation, especially for SOM forming from isoprene photooxidation products. However, elucidating the contributions of particle phase reactions to chemical composition and mass concentrations using traditional chamber experiment techniques has been difficult because condensational growth by saturated organic vapor also occurs. In the present study, a novel experimental setup was developed to exclusively investigate particle phase reactions.
Isoprene photooxidation products were continuously sampled from the Harvard Environmental Chamber (HEC). The concentration of isoprene in the HEC was controlled as sufficiently low to prevent particle formation in the HEC. The oxidation products were mixed with seed particles to induce SOM formation using another chemical reactor. SOM formation was monitored using both an aerosol mass spectrometer (AMS) and a scanning mobility particle sizer (SMPS), while reactive uptake of gaseous species was quantified using a proton transfer reaction mass spectrometer (PTR-MS).
Significant SOM formation was observed after mixing isoprene oxidation products with seed particles, depending on the type of seed particles. The AMS mass spectra were significantly different from those observed for previous isoprene photooxidation experiments. They were very similar to PMF factors found during atmospheric observations in tropical rain forests such as Borneo Island and the Amazon. Therefore, the present result strongly suggests the importance of particle phase reactions on SOM formation in actual atmospheric environments.