A field program study was conducted to determine the transport, dispersion, and transformation of sulphur and nitrogen oxides emitted from oil sands extraction plants in the Fort McMurray area. Measurements using the Intera/Alberta Research Council research aircraft were made under cold winter conditions during the months of March and December 1983 and warm summer conditions during June 1984. Sulphur dioxide emissions were detected as far as 90 km downwind from the source stack. Comparisons between the observed horizontal dispersion parameters and those of the Pasqui 11-Gifford stability classes show their rates of change with distance were similur, although observed values were slightly higher than predicted ones. The rate of transformation of so2 to SO2 was determined to be 0% to 2.81% h-l in the winter and 0% to 8.66% h-in the summer. Higher summer values are attributed to greater solar irradiance. Excess aerosol volume productions suggest that heterogeneous conversion may be appreciable under certain meteorological conditions and close to the emission source. The conversion rate of NO to NO2 varied considerably, hour to hour. Its range changed from 0.2% to 21.4% min The rate was positively correlated with turbulent mixing. The chemical reaction is controlled by the concentration of ozone entrained from the environment into the plume by turbulence. During cold winter conditions (below -25°C), ice crystals nucleated in the gaseous plume, grew to precipitation size. They were observed falling out of the plume to the earth's surface. This snow-out phenomenon was present only in the emission plume within about 10 km of the stack.