Semivolatile polycyclic aromatic hydrocarbons: Particle/gas partitioning measurements and modelling

This thesis considers-aspects relating to the particle/gas partitioning of polycyclic aromatic hydrocarbons (PAHs) in the ambient atmosphere. An extensive data set collected by the Integrated Atmospheric Deposition Network (IADN) was examined for insights relating to partitioning. This data set showed features not observed in previous studies. In particular, relationships between partitioning and saturated vapour pressure were observed to be less uniform among PAH species than previously noted. Furthermore, a distinct seasonality in those relationships was observed.; Ambient measurements of semivolatile organic compounds can be subject to sampling artefacts caused by variations in atmospheric conditions over the times required to collect enough air to meet analytical requirements. One such artefact caused by temperature variations was examined with a mathematical model. Results of the model showed that twenty-four-hour sampling is best conducted with start and end times that coincide with the morning occurrence of daily average temperature.; With the greater understanding of the atmospheric variations in PAH partitioning derived from the IADN measurements, an effort to incorporate these substances in a regional air quality model was undertaken. An emissions inventory was prepared for Canada and the United States. Estimated emissions include sources not considered by the US EPA through its National Emissions Inventory. When sources missing from the NEI are considered, the agreement between the two inventories is reduced to a factor of 2.5. Environment Canada's regional air quality model (AURAMS) was adapted to include PAHs and the sorptive partitioning process to which they are subject. A pair of test simulations demonstrated that the model was functional. Results obtained using two different partitioning expressions agreed in terms of simulated PAH concentrations and partitioning coefficients, but less so between PAH particulate fractions. Results of the test simulations demonstrate that the model is ready for a full-scale evaluation though such work is outside the scope of this thesis.