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Published April 16, 2005 | Supplemental Material + Published
Journal Article Open

Cloud condensation nucleus activation properties of biogenic secondary organic aerosol


Organic aerosols in general and secondary organic aerosol (SOA) in particular are known to contribute significantly to the atmospheric population of cloud condensation nuclei (CCN). However, current knowledge is limited with respect to the nature of this contribution. This study presents a series of experiments wherein the potential for biogenically derived SOA to act as CCN is explored. Five compounds were studied: four monoterpenes (α-pinene, β-pinene, limonene, and Δ^3-carene) and one terpenoid alcohol (terpinene-4-ol). In each case the aerosol formation was driven by the reaction of ozone with the biogenic precursor. The SOA produced in each experiment was allowed to age for several hours, during which CCN concentrations were periodically measured at four supersaturations: S = 0.27%, 0.32%, 0.54%, and 0.80%. The calculated relationships between particle dry diameter and critical supersaturation were found to fall in the range of previously reported data for single-component organic aerosols; of the systems studied, α-pinene SOA was the least CCN active, while limonene SOA exhibited the strongest CCN activity. Interestingly, the inferred critical supersaturation of the SOA products was considerably more sensitive to particle diameter than was found in previous studies. Furthermore, the relationships between particle size and critical supersaturation for the monoterpene SOA shifted considerably over the course of the experiments, with the aerosol becoming less hygroscopic over time. These results are consistent with the progressive oligomerization of the SOA.

Additional Information

Copyright 2005 by the American Geophysical Union. Received 24 September 2004; revised 6 January 2005; accepted 26 January 2005; published 6 April 2005. This research was supported by the Office of Science (BER), U.S. Department of Energy, grant DE-FG02-01ER63099, and by U.S. Environmental Protection Agency grant RD-83107501-0. Although the research described in this article has been funded in part by the U.S. Environmental Protection Agency, it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the view of the Agency, and no official endorsements should be inferred. The authors would like to thank R. Bahreini for assistance with the aerosol calibration system.

Attached Files

Published - jgrd11867.pdf

Supplemental Material - jgrd11867-sup-0001-t01.txt

Supplemental Material - jgrd11867-sup-0002-t02.txt


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