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Göran Frank

Director of graduate studies

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Comparison of observed and modeled hygroscopic behavior of atmospheric particles

Author

  • Olle H. Berg
  • Erik Swietlicki
  • Göran Frank
  • Bengt G. Martinsson
  • Sven Inge Cederfelt
  • Paolo Laj
  • Loretta Ricci
  • Axel Berner
  • Ulrike Dusek
  • Zsusanna Galambos
  • Nigatu S. Mesfin
  • Brett Yuskiewicz
  • Alfred Wiedensohler
  • Frank Stratmann
  • Douglas Orsini

Summary, in English

The hygroscopic behavior of sub-micrometer atmospheric aerosol particles was studied with a Tandem Differential Mobility Analyzer (TDMA) at a field site in the Po Valley, Italy. The measurements were done in a continental polluted aerosol during the CHEMDROP fog and haze field experiment at San Pietro di Capofiume in November 1994. In this study, hygroscopic diameter growth factors of individual particles were measured when taken from a dry state, to a relative humidity of 90 %. The aerosol consisted of two groups of particles with different hygroscopic properties, as also seen in an earlier field experiment at the same location in 1989 and at other continental sites. The present work is a closure study on the hygroscopic behavior of sub-micrometer aerosol particles and their mass. Ammonium sulfate was used to model the hygroscopic growth with a model based on thermodynamic data for non-ideal aqueous solutions at water vapor subsaturation. The study was made in two steps: The first step is a comparison between hygroscopic active aerosol volume fractions derived from TDMA measurements on individual particles integrated over the particle size distributions, and collected volume fractions of major ions sampled by size resolved cascade impactors. The model of hygroscopic growth was also used, in the second step, to calculate ambient sizes of individual aerosol particles. These sizes were then compared to the actual ambient sizes as measured by the Droplet Aerosol Analyzer. The result shows agreement, within the estimated errors, between the integrated hygroscopic active volume fractions and the collected volume fractions of inorganic salts, for five events out of six studied. A mass balance could also be obtained between the masses collected with the impactors and the integrated volume distributions, by attributing reasonable densities to the hygroscopically active and inactive fractions. The differences between the calculated and measured ambient sizes were within measurement errors, when Raoult's law was used to model the occasions with relative humidities larger than 95 %.

Department/s

  • Nuclear physics

Publishing year

1998-02-01

Language

English

Pages

47-64

Publication/Series

Contributions to Atmospheric Physics

Volume

71

Issue

1

Document type

Journal article review

Publisher

Deutsche Meteorologische Gesellschaft / Friedr. Vieweg & Sohn Verlagsgesellschaft mbh

Topic

  • Meteorology and Atmospheric Sciences

Status

Published

ISBN/ISSN/Other

  • ISSN: 0005-8173