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

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. aerosols have both natural and anthropogenic sources and consist of both organic and inorganic molecules. Organic compounds constitute 20-90% of the atmospheric aerosol mass, depending on 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. Of the organic fraction of particulate mass, much results from condensation of vapors that are produced by chemical reactions 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 the gas-particle partitioning of organic compounds are the vapor pressures6 and the enthalpies of vaporization and sublimation.