10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Formation of Secondary Aerosol and Growth of New Particles in the Ambient Atmosphere: An Experimental Study Using a Dual Smog Chamber System
SPIRO JORGA, Christos Kaltsonoudis, Spyros Pandis, Carnegie Mellon University
Abstract Number: 592 Working Group: Aerosol Transport and Transformation
Abstract Laboratory or field smog chamber experiments using as a starting point ambient air can improve our understanding of the evolution of atmospheric pollutants at timescales longer than those achieved by traditional laboratory experiments. Use of two identical smog chambers, with the first playing the role of the baseline chamber and the second the perturbation chamber (e.g. addition of oxidants) can assist in the interpretation of the results in such inherently complex chemical systems. The differences of the measurements in the two chambers can be used as the basis for the study of the corresponding chemical or physical processes.
In this work a set of two identical Teflon pillow-shaped smog chambers (1.5 m3 each) are used to study the production of secondary organic aerosol (SOA) and the evolution of the preexisting OA in an urban area (Pittsburgh, US). The two chambers are surrounded by UV lamps. The perturbation induced in one of the chambers is the addition of hydroxyl radicals (OH) formed from the photo-dissociation of HONO or H2O2. The aerosol composition in both chambers was continuously characterized using an aerosol mass spectrometer, while the concentration of organic gases using a proton transfer reaction mass spectrometer. Nucleation and growth of new particles was observed in the perturbation chamber in several experiments. At the same time, significant secondary organic aerosol production was observed much higher than what is expected from the oxidation of the present volatile organic compounds. The results of a series of experiments are analyzed to evaluate our understanding of the processing of this complex aerosol and its precursors under these controlled conditions. The implications for SOA and new particle formation are discussed.