Abstract Number: 314 Working Group: Urban Aerosols
Abstract The use of ambient air for studying atmospheric processes could help us bridge the gap between the idealized laboratory studies, using clean air as their starting point, and the actual atmosphere. Two identical smog chambers are used in these experiments with the first acting as a reference chamber and the second as the reaction chamber.
In this work, the dual smog chamber system was used to quantify the formation rates of secondary organic and inorganic aerosol in an urban environment (Pittsburgh, US). Ambient air was introduced in both chambers and HONO photolysis was used to produce hydroxyl radicals (OH) in the reaction chamber. The production rate of secondary organic aerosol (SOA) under typical noon-time OH concentrations ranged from 0.25-0.8 μg m-3 h-1. The production rate of sulfate was approximately 5 times less than that of the produced SOA. Nucleation and growth of new particles was observed in the reaction chamber. The produced SOA had similar composition with the preexisting oxygenated ambient OA. The reacted amounts of the measured volatile organic compounds were able to explain 5-50% of the formed SOA in the reaction chamber. Intermediate volatility organic compounds could be responsible for the rest.