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Published January 15, 2007 | public
Journal Article

Evidence for Organosulfates in Secondary Organic Aerosol


Recent work has shown that particle-phase reactions contribute to the formation of secondary organic aerosol (SOA), with enhancements of SOA yields in the presence of acidic seed aerosol. In this study, the chemical composition of SOA from the photooxidations of α-pinene and isoprene, in the presence or absence of sulfate seed aerosol, is investigated through a series of controlled chamber experiments in two separate laboratories. By using electrospray ionization−mass spectrometry, sulfate esters in SOA produced in laboratory photooxidation experiments are identified for the first time. Sulfate esters are found to account for a larger fraction of the SOA mass when the acidity of seed aerosol is increased, a result consistent with aerosol acidity increasing SOA formation. Many of the isoprene and α-pinene sulfate esters identified in these chamber experiments are also found in ambient aerosol collected at several locations in the southeastern U.S. It is likely that this pathway is important for other biogenic terpenes, and may be important in the formation of humic-like substances (HULIS) in ambient aerosol.

Additional Information

© 2007 American Chemical Society. Received for review August 30, 2006. Revised manuscript received October 18, 2006. Accepted November 3, 2006. Research at Caltech was funded by the U.S. Environmental Protection Agency Science to Achieve Results (STAR) program grant no. RD-83107501-0, managed by EPA's Office of Research and Development (ORD), National Center for Environmental Research (NCER) and Cooperative Agreement CR-831194001, and by the U.S. Department of Energy, Biological, and Environmental Research Program DE-FG02-05ER63983. This article has been jointly developed and published by EPA and the California Institute of Technology. It was produced under Cooperative Agreement no. CR83194001 and is subject to 40 CFR 30.36. The article has been reviewed by EPA personnel under EPA scientific and technical peer review procedures and approved for joint publication based on its scientific merit, technical accuracy, or contribution to advancing public understanding of environmental protection. However, the Agency's decision to publish the article jointly with Caltech is intended to further the public purpose supported by Cooperative Agreement no. CR83194001 and not to establish an official EPA rule, regulation, guidance, or policy through the publication of this article. Further, EPA does not endorse any products or commerical services mentioned in this publication. J.D.S. was supported in part by the United States Environmental Protection Agency (EPA) under the Science to Achieve Results (STAR) Graduate Fellowship Program. Research at the University of Antwerp was supported by the Belgian Federal Science Policy Office and the Research Foundation-Flanders (FWO). The Electric Power Research Institute provided support for the SEARCH network. We thank Rafal Szmigielski for his discussions on sulfation reactions.

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