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Proc Natl Acad Sci U S A

Title:		Integrating phase and composition of secondary organic aerosol from the ozonolysis of alpha-pinene
Author(s):		Kidd C; Perraud V; Wingen LM; Finlayson-Pitts BJ;
Address:		"Department of Chemistry, University of California, Irvine, CA 92697. Department of Chemistry, University of California, Irvine, CA 92697 bjfinlay@uci.edu"
Journal Title:		Proc Natl Acad Sci U S A
Year:		2014
Volume:		20140512
Issue:		21
Page Number:		7552 - 7557
DOI:		10.1073/pnas.1322558111
ISSN/ISBN:		1091-6490 (Electronic) 0027-8424 (Print) 0027-8424 (Linking)
Abstract:		"Airborne particles are important for public health, visibility, and climate. Predicting their concentrations, effects, and responses to control strategies requires accurate models of their formation and growth in air. This is challenging, as a large fraction is formed by complex reactions of volatile organic compounds, generating secondary organic aerosol (SOA), which grows to sizes important for visibility, climate, and deposition in the lung. Growth of SOA is particularly sensitive to the phase/viscosity of the particles and remains poorly understood. We report studies using a custom-designed impactor with a germanium crystal as the impaction surface to study SOA formed from the ozonolysis of alpha-pinene at relative humidities (RHs) up to 87% at 297 +/- 2 K (which corresponds to a maximum RH of 70-86% inside the impactor). The impaction patterns provide insight into changes in phase/viscosity as a function of RH. Attenuated total reflectance-Fourier transform infrared spectroscopy and aerosol mass spectrometry provide simultaneous information on composition changes with RH. The results show that as the RH at which the SOA is formed increases, there is a decrease in viscosity, accompanied by an increasing contribution from carboxylic acids and a decreasing contribution from higher molecular mass products. In contrast, SOA that is formed dry and subsequently humidified remains solid to high RH. The results of these studies have significant implications for modeling the growth, aging, and ultimately, lifetime of SOA in the atmosphere"
Keywords:		"Aerosols/*analysis Air Pollution/*analysis Atmosphere/*chemistry Bicyclic Monoterpenes Humidity *Models, Chemical Monoterpenes/*chemistry Ozone/*chemistry Phase Transition Temperature Viscosity SOA composition SOA viscosity aerosol phase oligomers particl;"
Notes:		"MedlineKidd, Carla Perraud, Veronique Wingen, Lisa M Finlayson-Pitts, Barbara J eng Research Support, U.S. Gov't, Non-P.H.S. 2014/05/14 Proc Natl Acad Sci U S A. 2014 May 27; 111(21):7552-7. doi: 10.1073/pnas.1322558111. Epub 2014 May 12"