A Thermodynamic Approach Using Group Contribution Methods to Model the Partitioning of Semivolatile Organic Compounds on Atmospheric Particulate Matter

Abstract

Atmospheric particulate matter is a complex mixture consisting of organic and inorganic chemicals. Their sources include various combustion processes, aerosolized dusts and soils, and chemical reactions which produce secondary aerosols. The partitioning of semivolatile toxic organic compounds (SOCs) between particulate matter and the gas phase is strongly influenced by temperature, water concentration, chemical composition of the particulate matter, and the organic fraction of the particulate matter. Many investigations have recently suggested that a considerable portion of the gas−particle (G/P) partitioning in the ambient atmosphere takes place between the liquid phase of organic aerosols and the surrounding gas phase. It has been shown that the equilibrium G/P partitioning constant, Kp, of an SOC partitioning to a given particle's liquid medium is inversely related to both the activity coefficient iγom and its saturated subcooled liquid vapor pressure, . Hence, in principal, the Kp of any SOC can be es...