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Numerical scattering simulations for estimating soot aggregate morphology from nephelometer scattering measurements

Karlsson, Anders LU ; Török, Sandra LU ; Roth, Adrian LU and Bengtsson, Per Erik LU orcid (2022) In Journal of Aerosol Science 159.
Abstract

Nephelometers are regularly used for air quality monitoring through scattering measurements of aerosols in the atmosphere. Less attention has been paid to the potential of estimating soot morphological parameters from nephelometer measurements in combination with scattering theory. In this work, we perform a fundamental laboratory study where an Ecotech Aurora 3000 nephelometer is used for measuring the scattering properties of soot with different characteristics. The nephelometer monitors the forward and backward scattering at three wavelengths (450 nm, 525 nm, and 635 nm) to retrieve information on the ratio of forward and backward scattering intensities, as well as the scattering wavelength dependence. An inverse scattering method,... (More)

Nephelometers are regularly used for air quality monitoring through scattering measurements of aerosols in the atmosphere. Less attention has been paid to the potential of estimating soot morphological parameters from nephelometer measurements in combination with scattering theory. In this work, we perform a fundamental laboratory study where an Ecotech Aurora 3000 nephelometer is used for measuring the scattering properties of soot with different characteristics. The nephelometer monitors the forward and backward scattering at three wavelengths (450 nm, 525 nm, and 635 nm) to retrieve information on the ratio of forward and backward scattering intensities, as well as the scattering wavelength dependence. An inverse scattering method, based on the Rayleigh–Debye–Gans theory, for determination of the equivalent fractal dimension (Df) and radius of gyration (Rg) of soot particles from the experimental scattering data was developed. It is shown that the inverse method can estimate Rg and Df when Rg<185nm and from the wavelength dependence, information on the relative amount of organic soot could be obtained. For validation, estimated parameters are compared with the morphological parameters of soot sampled from the mini-CAST soot generator and evaluated using transmission electron microscopy (TEM). Uncertainties and limitations of the procedure are discussed.

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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Fractal parameters, Inverse scattering, Nephelometer, Soot
in
Journal of Aerosol Science
volume
159
article number
105828
publisher
Elsevier
external identifiers
  • scopus:85110622272
ISSN
0021-8502
DOI
10.1016/j.jaerosci.2021.105828
language
English
LU publication?
yes
id
0c6475ee-5cb7-47fc-8bab-e6b1ad4d8cc2
date added to LUP
2021-08-19 13:54:45
date last changed
2022-04-19 07:32:56
@article{0c6475ee-5cb7-47fc-8bab-e6b1ad4d8cc2,
  abstract     = {{<p>Nephelometers are regularly used for air quality monitoring through scattering measurements of aerosols in the atmosphere. Less attention has been paid to the potential of estimating soot morphological parameters from nephelometer measurements in combination with scattering theory. In this work, we perform a fundamental laboratory study where an Ecotech Aurora 3000 nephelometer is used for measuring the scattering properties of soot with different characteristics. The nephelometer monitors the forward and backward scattering at three wavelengths (450 nm, 525 nm, and 635 nm) to retrieve information on the ratio of forward and backward scattering intensities, as well as the scattering wavelength dependence. An inverse scattering method, based on the Rayleigh–Debye–Gans theory, for determination of the equivalent fractal dimension (D<sub>f</sub>) and radius of gyration (R<sub>g</sub>) of soot particles from the experimental scattering data was developed. It is shown that the inverse method can estimate R<sub>g</sub> and D<sub>f</sub> when R<sub>g</sub>&lt;185nm and from the wavelength dependence, information on the relative amount of organic soot could be obtained. For validation, estimated parameters are compared with the morphological parameters of soot sampled from the mini-CAST soot generator and evaluated using transmission electron microscopy (TEM). Uncertainties and limitations of the procedure are discussed.</p>}},
  author       = {{Karlsson, Anders and Török, Sandra and Roth, Adrian and Bengtsson, Per Erik}},
  issn         = {{0021-8502}},
  keywords     = {{Fractal parameters; Inverse scattering; Nephelometer; Soot}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Journal of Aerosol Science}},
  title        = {{Numerical scattering simulations for estimating soot aggregate morphology from nephelometer scattering measurements}},
  url          = {{http://dx.doi.org/10.1016/j.jaerosci.2021.105828}},
  doi          = {{10.1016/j.jaerosci.2021.105828}},
  volume       = {{159}},
  year         = {{2022}},
}