During the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign, two NASA research aircraft, a DC-8 and a P- 3B, were outfitted with extensive trace gas (the DC-8) and aerosol (both aircraft) instrumentation. Each aircraft spent about a half hour sampling air around the oil sands mining and upgrading facilities near Ft. McMurray, Alberta, Canada. The DC-8 circled the area, while the P-3B flew directly over the upgrading plants, sampling close to the exhaust stacks, then headed downwind to monitor the aerosol as it aged. At short range, the plume from the oil sands is a complex mosaic of freshly nucleated ultrafine particles from a SO2- and NO2-rich plume, soot and possibly fly ash from indus- trial processes, and dust from dirt roads and mining opera- tions. Shortly downwind, organic aerosol appears in quanti- ties that rival SO4, either as volatile organic vapors condense or as they react with the H2SO4. The DC-8 pattern allowed us to integrate total flux from the oil sands facilities within about a factor of 2 uncertainty that spanned values consistent with 2008 estimates from reported SO2 and NO2 emissions, though there is no reason to expect one flyby to represent av- erage conditions. In contrast, CO fluxes exceeded reported regional emissions, due either to variability in production or sources missing from the emissions inventory. The conver- sion rate of SO2 to aerosol SO4 of ∼ 6 % per hour is con- sistent with earlier reports, though OH concentrations are in- sufficient to accomplish this. Other oxidation pathways must
be active. Altogether, organic aerosol and black carbon emis- sions from the oil sands operations are small compared with annual forest fire emissions in Canada. The oil sands do con- tribute significant sulfate and exceed fire production of SO2 by an order of magnitude.