Friday, March 29, 2019 - 12:00pm
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100F Pierce, 29 Oxford St., Cambridge

Atmospheric & Environmental Chemistry Seminar

"Aqueous-Phase Chemistry of Secondary Organic Aerosol" with Qi Zhang, University of California, Davis.

Secondary organic aerosol (SOA) is abundant in the atmosphere, but the formation mechanisms and properties of SOA components, especially those formed through aqueous-phase reactions (i.e., aqSOA), remain poorly understood. As an effort to close this knowledge gap, we have performed laboratory and field studies to investigate the formation and photochemical aging of organic aerosol in atmospheric aqueous phases. We carried out ambient measurement studies in the San Joaquin Valley (SJV) of California during winter fog seasons and found evidence that aqueous reactions can be an important source of oxygenated and nitrogen-containing SOA. We also observed enrichments of light-absorbing compounds such as imidazole- or pyrazine-based compounds in fog waters, which were likely formed from the aqueous reactions of aldehydes with amino compounds. We then examined the evolution of fog water composition over the course of simulated sunlight illumination. Fog organics became increasingly more oxidized and showed an enhancement in N/C ratio during illumination, suggesting the incorporation of oxygen- and nitrogen-containing functional groups into the molecules. In the meantime, since the average molecular weight of fog organics appears to decrease during the reactions, fragmentation reactions also happened but did not lead to significant formation of VOCs.

Contact Name: 

Kelvin Bates

Research Areas: 

Harvard University
Center for the Environment

Address: 26 Oxford Street, 4th Floor, Cambridge
Phone: (617) 495-0368

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