Thursday, May 7, 2015

Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures

Merete Bilde, Kelley Barsanti, Murray Booth, Christopher D. Cappa, Neil M. Donahue, Eva U. Emanuelsson, Gordon McFiggans, Ulrich K. Krieger, Claudia Marcolli, David Topping, Paul Ziemann, Mark Barley, Simon Clegg, Benjamin Dennis-Smither, Mattias Hallquist, Åsa M. Hallquist, Andrey Khlystov, Markku Kulmala, Ditte Mogensen, Carl J. Percival, Francis Pope, Jonathan P. Reid, M. A. V. Ribeiro da Silva, Thomas Rosenoern, Kent Salo, Vacharaporn Pia Soonsin, Taina Yli-Juuti, Nønne L. Prisle, Joakim Pagels, Juergen Rarey, Alessandro A. Zardini, and Ilona Riipinen

Aerosol particles are important constituents of the atmosphere. They impact modern society through their effects on visibility, human health, and global climate. Despite this great importance, they continue to represent a challenge to scientists due to their complexity. Atmospheric aerosols have both natural and anthropogenic sources and consist of both organic and inorganic molecules. Organic compounds constitute 20−90% of the atmospheric aerosol particle mass, depending on the location. The term primary aerosol particle is used to describe particles that are emitted directly into the atmosphere as particles. These primary particles are transformed in the atmosphere through the continuous exchange between the gas and particle phases via evaporation and condensation. Additionally, a large fraction of the organic particulate mass results from condensation of vapors that are produced by chemical reactions in the gas phase and is termed secondary organic aerosol (SOA). To predict the temporal and spatial distribution of aerosols, particularly SOA, it is necessary to understand the fundamental parameters that govern the distribution of organic compounds between the gas and particle phases. Key thermodynamic properties describing the equilibrium gas to particle partitioning of organic compounds are the saturation vapor pressures and the enthalpies of vaporization and sublimation.

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