HR: 1330h
AN: A12B-0087    [PDF]
TI: Simultaneous Measurement of Size, Composition, Hygroscopicity, and Density of Single Ambient Particles
AU: * Zelenyuk, A
EM: alla.zelenyuk@pnl.gov
AF: PNNL, EMSL, Richland, wa 99352 United States
AU: Imre, D g
EM: dan.imre@pnl.gov
AF: PNNL, EMSL, Richland, wa 99352 United States
AU: Han, J
EM: hohan@bnl.gov
AF: BNL, Bldg 815, upton, ny 11973 United States
AU: Oatis, S
EM: SOatis@southampton.liu.edu
AF: South Hampton U, Long island, South Hampton, ny 11772 United States
AB: The holly grail in aerosol climate interaction is a roadmap that takes one from emissions of aerosol and aerosol precursors through aerosol transformations, to optical and cloud effects and finally to climate impacts. A critical element on this path must be the behavior of aerosol as a function of atmospheric relative humidity, which in turn requires an understanding of the correlation between aerosol composition and hygroscopicity. For single component particles this problem is tractable and reasonably understood. But, the vast majority of particles in the real atmosphere are internal mixtures of hygroscopic salts, organic acids and or bases, long chain hydrocarbons, soot, mineral dust and the list go on. Hundreds of organic compounds with highly varying hygroscopicities can be found in single particles. It would be unrealistic to expect global climate models to include and track each of these compounds. A similar problem faces the experimental world, where measuring the size, detailed molecular composition and hygroscopicity of individual particles although, in principle possible, is impractical. Single particle mass spectroscopy can be used to classify particles as organics mixed with sulfate, for example. Or in some cases pinpoint the class of some of the organics found in the mixture. But it cannot yield a quantitative measure of relative amounts. In an attempt to address this issue we have developed the method to measure simultaneously hygroscopicity, size, and composition of individual ambient particles. However, the data from Long Island NY, where the vast majority of particles were internally mixed sulfate with organics, the correlation between composition and hygroscopicity was rather weak. This is due to the fact that single-laser single particle mass spectra cannot quantitatively measure the ratio of organics to sulfates. In contrast, we found a very clear correlation between hygroscopicity and particle density for a given class of particles. In this case the density of the sulfate containing class is more quantitative measure of the ratio of organic to sulfate, which in turn determines particle hygroscopicity. Because the measurement of particle density, size and composition is much easier than measuring hygroscopicity, if general relationships between hygroscopicity and density for specific particle classes can be found, the measurement burden is significantly reduced. We will present results on particle density, hygroscopicity, size and composition measurements using a DMA and discuss a DMA-free second-generation system.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting