Gas-particle partitioning of semivolatile organic compounds (SOCs) on mixtures of aerosols

Exposure to atmospheric particulate matter, especially to fine particles less than 2.5 μm in size, has been associated with increased levels of morbidity and mortality, especially among the elderly and the sick. It has been hypothesized that the presence of organic compounds in the particle phase can exacerbate these effects. Predicting gas-particle partitioning, or the distribution of possibly hazardous semivolatile organic compounds between gas and particle phase in the atmosphere hence becomes critical. However, incomplete information about the composition, and mixing state of atmospheric aerosols has, thus far, prevented truly mechanistic prediction of gas-particle partitioning in the ambient atmosphere.; In this work, the gas-particle partitioning of mixtures of aerosols from two and three sources, organic and inorganic, primary and secondary in origin, is studied using smog chamber experiments to generate partitioning coefficient data for a set of diverse SOCs. The system is then modeled using thermodynamic gas-particle partitioning models. The models are successful in predicting gas-particle partitioning using a knowledge of the physical make-up, and chemical composition of the aerosol in the chamber. The calculations are sensitive to the mixing state of the aerosol. This sensitivity has important ramifications in predicting gas-particle partitioning in the ambient atmosphere. Some single aerosol source experiments are also carried out and the partitioning model's sensitivity to input parameter choices is tested using the generated experimental data in conjunction with preexisting smog chamber data. The calculation of partitioning coefficients requires the use of parameter estimation methods for various model inputs and a software toolkit incorporating many of these methods is also presented as part of this work. A kinetic adsorptive partitioning formulation modeling the reactions and partitioning of two siloxanes (possible replacements for chlorinated solvents) is successful in demonstrating the particle uptake of the reaction products.*; *This dissertation is a multimedia document (contains text and other applications not available in printed format).