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Formation of highly hygroscopic soot aerosols upon internal mixing with sulfuric acid vapor

Khalizov, Alexei F.; Zhang, Renyi; Zhang, Dan; Xue, Huaxin; Pagels, Joakim LU and McMurry, Peter H. (2009) In Journal of Geophysical Research 114.
Abstract
The hygroscopic properties of submicron soot particles during internal mixing with gaseous sulfuric acid have been investigated using a combined tandem differential mobility analyzer (TDMA) and differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) technique. Fresh particles exhibit no change in mobility size and mass at subsaturated conditions, whereas particles exposed to gaseous sulfuric acid (10(9)-10(10) molecule cm(-3), 12 s contact time) experience significant mobility size and mass changes with increasing relative humidity (RH). The DMA-APM measurements reveal that particles of all sizes exposed to H2SO4 vapor gain mass with increasing RH because of absorption of water by sulfuric acid coating. However, on the... (More)
The hygroscopic properties of submicron soot particles during internal mixing with gaseous sulfuric acid have been investigated using a combined tandem differential mobility analyzer (TDMA) and differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) technique. Fresh particles exhibit no change in mobility size and mass at subsaturated conditions, whereas particles exposed to gaseous sulfuric acid (10(9)-10(10) molecule cm(-3), 12 s contact time) experience significant mobility size and mass changes with increasing relative humidity (RH). The DMA-APM measurements reveal that particles of all sizes exposed to H2SO4 vapor gain mass with increasing RH because of absorption of water by sulfuric acid coating. However, on the basis of mobility size measurements using TDMA, upon humidification H2SO4-coated soot agglomerates display distinct hygroscopic growth patterns depending on their initial size and the mass fraction of condensed sulfuric acid. While small particles experience an increase in their mobility sizes, larger particles exhibit a marked shrinkage due to compaction. We suggest that determination of the hygroscopic properties of soot particles using a TDMA alone can be inconclusive. Restructuring of the soot agglomerates and filling of the voids that accompany the condensation of water-soluble materials and subsequent water absorption lead to little or no observable changes in particle mobility size at subsaturated RH even for particles that contain aqueous coatings. Extrapolation of our experimental results to the urban atmosphere indicates that initially hydrophobic soot particles acquire sufficient sulfate coating to become efficient CCN (cloud condensation nuclei) within a time period ranging from a few hours to a few days, dependent on the ambient H2SO4 level. The results imply that internal mixing with sulfuric acid through H2SO4 vapor condensation likely represents a common aging process for a variety of atmospheric aerosols. The variations in the size and hygroscopicity of soot particles during atmospheric processing influence their optical properties, cloud-forming potential, and human health effects. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Geophysical Research
volume
114
publisher
American Geophysical Union
external identifiers
  • wos:000263950200001
  • scopus:65849256901
ISSN
2156-2202
DOI
10.1029/2008JD010595
language
English
LU publication?
yes
id
be32b370-8be2-4074-9128-7f3626ae8843 (old id 1370680)
date added to LUP
2009-05-08 14:10:00
date last changed
2017-10-08 03:42:49
@article{be32b370-8be2-4074-9128-7f3626ae8843,
  abstract     = {The hygroscopic properties of submicron soot particles during internal mixing with gaseous sulfuric acid have been investigated using a combined tandem differential mobility analyzer (TDMA) and differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) technique. Fresh particles exhibit no change in mobility size and mass at subsaturated conditions, whereas particles exposed to gaseous sulfuric acid (10(9)-10(10) molecule cm(-3), 12 s contact time) experience significant mobility size and mass changes with increasing relative humidity (RH). The DMA-APM measurements reveal that particles of all sizes exposed to H2SO4 vapor gain mass with increasing RH because of absorption of water by sulfuric acid coating. However, on the basis of mobility size measurements using TDMA, upon humidification H2SO4-coated soot agglomerates display distinct hygroscopic growth patterns depending on their initial size and the mass fraction of condensed sulfuric acid. While small particles experience an increase in their mobility sizes, larger particles exhibit a marked shrinkage due to compaction. We suggest that determination of the hygroscopic properties of soot particles using a TDMA alone can be inconclusive. Restructuring of the soot agglomerates and filling of the voids that accompany the condensation of water-soluble materials and subsequent water absorption lead to little or no observable changes in particle mobility size at subsaturated RH even for particles that contain aqueous coatings. Extrapolation of our experimental results to the urban atmosphere indicates that initially hydrophobic soot particles acquire sufficient sulfate coating to become efficient CCN (cloud condensation nuclei) within a time period ranging from a few hours to a few days, dependent on the ambient H2SO4 level. The results imply that internal mixing with sulfuric acid through H2SO4 vapor condensation likely represents a common aging process for a variety of atmospheric aerosols. The variations in the size and hygroscopicity of soot particles during atmospheric processing influence their optical properties, cloud-forming potential, and human health effects.},
  author       = {Khalizov, Alexei F. and Zhang, Renyi and Zhang, Dan and Xue, Huaxin and Pagels, Joakim and McMurry, Peter H.},
  issn         = {2156-2202},
  language     = {eng},
  publisher    = {American Geophysical Union},
  series       = {Journal of Geophysical Research},
  title        = {Formation of highly hygroscopic soot aerosols upon internal mixing with sulfuric acid vapor},
  url          = {http://dx.doi.org/10.1029/2008JD010595},
  volume       = {114},
  year         = {2009},
}