A new aerosol flow system for photochemical and thermal studies of tropospheric aerosols
Authors
Alla Zelenyuk-Imre — Pacific Northwest National Laboratory
Lizabeth M Alexander — Pacific Northwest National Laboratory
Michael Ezell — University of California
Barbara J Finlayson-Pitts — University of California
Emily A. Bruns — University of California
Veronique Michele Lucie Perraud — University of California
Stanley N. Johnson — University of California
Yong Yu — California Air Resources Board
Donald Dabdub — University of California
Yan Li — University of California
Category
Instruments
Description
Photo of large-volume, slow-flow stainless-steel flow tube for aerosol studies
For studying the formation and photochemical/thermal reactions of aerosols relevant to the troposphere, a unique, high-volume, slow-flow, stainless steel aerosol flow system has been constructed and characterized experimentally. This apparatus fills a gap between high speed, short residence-time flow tubes and large, continuous flow chambers that have residence times of many hours or even days. The flow tube is equipped with ultraviolet lamps for photolysis and the residence time is of the order of an hour. Five sampling ports located along the length of the flow tube allow for time-resolved measurements of aerosol and gas-phase products. This system has many advantages, including a surface to volume ratio of 10 m-1 and total volume of 1.2 m3, sufficiently large flows to allow a number of analytical techniques to be applied simultaneously, ease of disassembly for cleaning and easily varied residence times. Analytical techniques applied to this system include analyzers for NOx and ozone, as well as GC-MS and PTR-MS for other gas-phase products; an integrating nephelometer for light scattering measurements; SMPS and APS for particle size distributions; integrated particle collection on filters and impactors, and real time particle mass spectrometry (AMS and SPLAT(II)). This system has been applied to photochemical studies of nitrite and nitrate aerosols as well as formation of secondary organic aerosol from alpha-pinene reactions (NOx photooxidation and ozonolysis). Selected results from these studies, including the effects of organic coatings on light scattering by particles, will be presented to demonstrate the capabilities of this new system.
