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Processing of Soot by Controlled Sulphuric Acid and Water Condensation - Mass and Mobility Relationship

Pagels, Joakim LU ; Khalizov, Alexei F.; McMurry, Peter H. and Zhang, Renyi Y. (2009) In Aerosol Science and Technology 43(7). p.629-640
Abstract
The effects of atmospheric processing on soot particle morphology were studied in the laboratory using the Differential Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the DMA-DMA (Tandem DMA) techniques. To simulate atmospheric processing, combustion soot agglomerates were altered by sulphuric acid vapor condensation, relative humidity (RH) cycling, and evaporation of the sulphuric acid and water by heating. Primary investigated properties were particle mobility size and mass. Secondary properties, derived from these, include effective density, fractal dimension, dynamic shape factor, and the mass fraction of condensed material. A transformation of the soot particles to more compact forms occurs as sulphuric acid and water... (More)
The effects of atmospheric processing on soot particle morphology were studied in the laboratory using the Differential Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the DMA-DMA (Tandem DMA) techniques. To simulate atmospheric processing, combustion soot agglomerates were altered by sulphuric acid vapor condensation, relative humidity (RH) cycling, and evaporation of the sulphuric acid and water by heating. Primary investigated properties were particle mobility size and mass. Secondary properties, derived from these, include effective density, fractal dimension, dynamic shape factor, and the mass fraction of condensed material. A transformation of the soot particles to more compact forms occurs as sulphuric acid and water condense onto fresh soot. The particle mass increases and initially the mobility diameter decreases, indicating restructuring of the soot core, likely due to surface tension forces. For a given soot source and condensing liquid, the degree of compaction depends strongly on the mass (or volume) fraction of condensed material. For water and sulphuric acid condensing on combustion soot, a mass increase of 2-3 times is needed for a transformation to spherical particles. In the limit of spherical particles without voids, the effective density then approaches the inherent material density, the fractal dimension approaches 3 and the dynamic shape factor approaches 1. Our results indicate that under typical atmospheric conditions, soot particles will be fully transformed to spherical droplets on a time scale of several hours. It is expected that the morphology changes and addition of soluble material to soot strongly affect the optical and hygroscopic properties of soot. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Aerosol Science and Technology
volume
43
issue
7
pages
629 - 640
publisher
Taylor & Francis
external identifiers
  • wos:000265272400001
  • scopus:65849475477
ISSN
1521-7388
DOI
10.1080/02786820902810685
language
English
LU publication?
yes
id
6b1ee5c2-cb50-4820-a12e-99cd6a756aef (old id 1400461)
date added to LUP
2009-06-15 14:06:55
date last changed
2017-11-12 03:30:37
@article{6b1ee5c2-cb50-4820-a12e-99cd6a756aef,
  abstract     = {The effects of atmospheric processing on soot particle morphology were studied in the laboratory using the Differential Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the DMA-DMA (Tandem DMA) techniques. To simulate atmospheric processing, combustion soot agglomerates were altered by sulphuric acid vapor condensation, relative humidity (RH) cycling, and evaporation of the sulphuric acid and water by heating. Primary investigated properties were particle mobility size and mass. Secondary properties, derived from these, include effective density, fractal dimension, dynamic shape factor, and the mass fraction of condensed material. A transformation of the soot particles to more compact forms occurs as sulphuric acid and water condense onto fresh soot. The particle mass increases and initially the mobility diameter decreases, indicating restructuring of the soot core, likely due to surface tension forces. For a given soot source and condensing liquid, the degree of compaction depends strongly on the mass (or volume) fraction of condensed material. For water and sulphuric acid condensing on combustion soot, a mass increase of 2-3 times is needed for a transformation to spherical particles. In the limit of spherical particles without voids, the effective density then approaches the inherent material density, the fractal dimension approaches 3 and the dynamic shape factor approaches 1. Our results indicate that under typical atmospheric conditions, soot particles will be fully transformed to spherical droplets on a time scale of several hours. It is expected that the morphology changes and addition of soluble material to soot strongly affect the optical and hygroscopic properties of soot.},
  author       = {Pagels, Joakim and Khalizov, Alexei F. and McMurry, Peter H. and Zhang, Renyi Y.},
  issn         = {1521-7388},
  language     = {eng},
  number       = {7},
  pages        = {629--640},
  publisher    = {Taylor & Francis},
  series       = {Aerosol Science and Technology},
  title        = {Processing of Soot by Controlled Sulphuric Acid and Water Condensation - Mass and Mobility Relationship},
  url          = {http://dx.doi.org/10.1080/02786820902810685},
  volume       = {43},
  year         = {2009},
}