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Characterization of secondary organic aerosol formed from pyruvic acid photolysis

by Severson, Rachel

Abstract

Pyruvic acid is ubiquitous in the atmosphere and currently used as a proxy for similar molecules in climate models. We produced secondary organic aerosol (SOA) from the aqueous photolysis of pyruvic acid, and aerosol yield and cloud condensation nuclei (CCN) activity was measured. Aqueous samples were atomized to obtain the volume of aerosol produced per volume of initial pyruvic acid (aerosol yield) and the hygroscopicity parameter (κ) was determined. At room temperature (21°C), unreacted pyruvic acid was atomized to yield ~ 4% aerosol with κ = 0.22. Significant formation of aerosol from unreacted volatile pyruvic acid implicates the potential involvement of self-oligomerization via hemiketal formation. After photolysis, a 0.1 M aqueous sample of pyruvic acid led to an increased aerosol yield of ~ 15%, and a decrease in κ to 0.13. This decrease in κ after photochemical aging is in contrast to conventional hypotheses regarding in-cloud SOA formation, which generally predict an increase in hygroscopicity. The potential roles of variable environmental conditions in SOA formation were also investigated. Pyruvic acid photolysis carried out at 15°C, pH 2 and 21°C, pH 7 gave a decrease in κ from 0.2 to 0.13, and from 0.22 to 0.12, respectively. At pH 7, photolysis resulted in a lesser increase in aerosol yield from ~ 6% to only 10%; aerosol yield increased in the 15°C condition from 5 to 18%. These results support the importance of further investigation of SOA formation and composition, and of the effects of fluctuating environmental conditions—these effects are not currently well understood, but are likely important on a global scale.

Note

The author has given permission for this work to be deposited in the Digital Archive of Colorado College.

Colorado College Honor Code upheld.

Includes bibliographical references.

Administrative Notes

The author has given permission for this work to be deposited in the Digital Archive of Colorado College.

Colorado College Honor Code upheld.

Copyright
Copyright restrictions apply.
Publisher
Colorado College
PID
coccc:11157
Digital Origin
born digital
Extent
78 pages : illustrations
Thesis
Senior Thesis -- Colorado College
Thesis Advisor
Sharon Neely Lee, Mari Drossman, Howard
Department/Program
Environmental Program
Degree Name
Bachelor of Arts
Degree Type
bachelor
Degree Grantor
Colorado College
Date Issued
2015-05