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Published August 1, 2007 | public
Journal Article

Effect of Acidity on Secondary Organic Aerosol Formation from Isoprene


The effect of particle-phase acidity on secondary organic aerosol (SOA) formation from isoprene is investigated in a laboratory chamber study, in which the acidity of the inorganic seed aerosol was controlled systematically. The observed enhancement in SOA mass concentration is closely correlated to increasing aerosol acidity (R² = 0.979). Direct chemical evidence for acid-catalyzed particle-phase reactions was obtained from the SOA chemical analyses. Aerosol mass concentrations for the 2-methyltetrols, as well as the newly identified sulfate esters, both of which serve as tracers for isoprene SOA in ambient aerosols, increased significantly with enhanced aerosol acidity. Aerosol acidities, as measured in nmol of H⁺ m⁻³, employed in the present study are in the same range as those observed in tropospheric aerosol collected from the eastern U.S.

Additional Information

© 2007 American Chemical Society. Received 18 February 2007. Date accepted 8 May 2007. Published online 28 June 2007. Published in print 1 August 2007. Research at Caltech was funded by the U.S. EPA Science to Achieve Results (STAR) program Grant RD-83107501-0, managed by the EPA's Office of Research and Development (ORD), National Center for Environmental Research (NCER), and Cooperative Agreement CR-831194001, and funded by the U.S. Department of Energy, Biological, and Environmental Research Program DE-FG02-05ER63983. This article has been jointly developed and published by the EPA and Caltech. It was produced under Cooperative Agreement 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 CR83194001 and not to establish an official EPA rule, regulation, guidance, or policy through the publication of this article. The U.S. EPA through its ORD also funded research described here under Contract EP-D-05-065 to Alion Science and Technology. Further, the EPA does not endorse any products or commercial services mentioned in this publication. J.D.S. was supported in part by the U.S. EPA under the STAR Graduate Fellowship Program.

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