Fractal parameters of individual soot particles determined using electron tomography: Implications for optical properties

Kouji Adachi, Serena H. Chung, Heiner Friedrich, P R Buseck

Research output: Contribution to journalArticle

79 Citations (Scopus)

Abstract

The morphologies of soot particles are both complex and important. They influence soot atmospheric lifetimes, global distributions, and climate impacts. Particles can have complex geometries with overlapping projecting parts and pores that are difficult to infer from the conventional techniques used to study them. We used electron tomography with a transmission electron microscope (TEM) to determine three-dimensional (3D) properties such as fractal dimension (Df), radius of gyration (Rg), volume (V), surface area (As), and structural coefficient (ka) for individual soot particles from the ambient air of an Asian dust (AD) episode and from a U.S. traffic source. The respective median values of Df are 2.4 and 2.2, of Rg are 274 and 251 nm, of As/V are 9.2 and 13.7 × 107 m-1, and of ka are 0.67 and 0.71. The corresponding parameters, when calculated from 2D projections such as TEM images, are considerably less precise and commonly erroneous. Unlike other methods that have been used to derive fractal parameters, our method is applicable to particles of any Df. Using the 3D data, we estimate that mass-normalized scattering cross sections of our AD and traffic soot particles are respectively about 15 and 30 times greater than those of unaggregated spheres, which is the shape assumed in global models to estimate radiative forcing. Accurate 3D information can be used to compute more precise optical properties, which are important for estimating and direct radiative forcing and improving our understanding of the climate impact of soot.

Original languageEnglish (US)
Article numberD14202
JournalJournal of Geophysical Research: Atmospheres
Volume112
Issue number14
DOIs
StatePublished - Jul 27 2007

Fingerprint

Soot
soot
optical property
Fractals
tomography
Tomography
fractals
Optical properties
optical properties
electron
Electrons
radiative forcing
gyration
climate effect
electrons
traffic
Particles (particulate matter)
climate
Dust
Electron microscopes

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography

Cite this

Fractal parameters of individual soot particles determined using electron tomography : Implications for optical properties. / Adachi, Kouji; Chung, Serena H.; Friedrich, Heiner; Buseck, P R.

In: Journal of Geophysical Research: Atmospheres, Vol. 112, No. 14, D14202, 27.07.2007.

Research output: Contribution to journalArticle

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