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Constraining the density and complex refractive index of elemental and organic carbon in biomass burning aerosol using optical and chemical measurements

Schkolnik, G.; Chand, D.; Hoffer, A.; Andreae, M. O.; Erlick, C.; Swietlicki, Erik LU and Rudich, Y. (2007) In Atmospheric Environment 41(5). p.1107-1118
Abstract
The role of biomass burning aerosols in the climate system is still poorly quantified, in part due to uncertainties regarding the optical properties of elemental and organic carbon (EC and OC, respectively), the main constituents of pyrogenic aerosols. In this study, we utilize comprehensive physical and chemical field measurements of biomass burning aerosols in Brazil to constrain the densities and refractive indices (RI) of EC and OC in these particles, by comparing their optically and chemically derived RI. The optically derived effective RI are retrieved from the measured absorption and scattering coefficients using a Mie scattering algorithm, and serve as a reference dataset, while the chemically derived effective RI are calculated... (More)
The role of biomass burning aerosols in the climate system is still poorly quantified, in part due to uncertainties regarding the optical properties of elemental and organic carbon (EC and OC, respectively), the main constituents of pyrogenic aerosols. In this study, we utilize comprehensive physical and chemical field measurements of biomass burning aerosols in Brazil to constrain the densities and refractive indices (RI) of EC and OC in these particles, by comparing their optically and chemically derived RI. The optically derived effective RI are retrieved from the measured absorption and scattering coefficients using a Mie scattering algorithm, and serve as a reference dataset, while the chemically derived effective RI are calculated from the measured chemical composition using electromagnetic mixing rules. The results are discussed in light of the observed combustion conditions, and in an effort to derive conclusions as to the chemical and optical properties of the usually less well-characterized components of biomass burning aerosols, namely, elemental carbon and organic matter. The best agreement between the optically and chemically derived RI was achieved by assigning a density of rho(EC) = 1.8 g cm(-3) and refractive index RIEC = 1.87 - 0.22i to the EC component, and rho = 0.9 g cm(-3) and RI = 1.4 - 0i to the unidentified organic matter fraction of the particles. These parameters suggest low graphitization levels for the EC, and a dominant proportion of aliphatic compounds in the unidentified organic matter. Combining the density and RI of the unidentified organic matter with the properties of the chemically characterized organic fraction yields rho = 1.1 g cm(-3) and RI = 1.3 - 0i for the total aerosol OC. (c) 2006 Elsevier Ltd. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
aerosol optical properties, biomass burning, refractive index, organic carbon, elemental carbons
in
Atmospheric Environment
volume
41
issue
5
pages
1107 - 1118
publisher
Elsevier
external identifiers
  • wos:000244329800017
  • scopus:33845618672
ISSN
1352-2310
DOI
10.1016/j.atmosenv.2006.09.035
language
English
LU publication?
yes
id
da0f6523-5638-402f-b724-a2d6c2b1f9d9 (old id 674351)
date added to LUP
2007-12-18 08:52:30
date last changed
2017-07-09 04:24:32
@article{da0f6523-5638-402f-b724-a2d6c2b1f9d9,
  abstract     = {The role of biomass burning aerosols in the climate system is still poorly quantified, in part due to uncertainties regarding the optical properties of elemental and organic carbon (EC and OC, respectively), the main constituents of pyrogenic aerosols. In this study, we utilize comprehensive physical and chemical field measurements of biomass burning aerosols in Brazil to constrain the densities and refractive indices (RI) of EC and OC in these particles, by comparing their optically and chemically derived RI. The optically derived effective RI are retrieved from the measured absorption and scattering coefficients using a Mie scattering algorithm, and serve as a reference dataset, while the chemically derived effective RI are calculated from the measured chemical composition using electromagnetic mixing rules. The results are discussed in light of the observed combustion conditions, and in an effort to derive conclusions as to the chemical and optical properties of the usually less well-characterized components of biomass burning aerosols, namely, elemental carbon and organic matter. The best agreement between the optically and chemically derived RI was achieved by assigning a density of rho(EC) = 1.8 g cm(-3) and refractive index RIEC = 1.87 - 0.22i to the EC component, and rho = 0.9 g cm(-3) and RI = 1.4 - 0i to the unidentified organic matter fraction of the particles. These parameters suggest low graphitization levels for the EC, and a dominant proportion of aliphatic compounds in the unidentified organic matter. Combining the density and RI of the unidentified organic matter with the properties of the chemically characterized organic fraction yields rho = 1.1 g cm(-3) and RI = 1.3 - 0i for the total aerosol OC. (c) 2006 Elsevier Ltd. All rights reserved.},
  author       = {Schkolnik, G. and Chand, D. and Hoffer, A. and Andreae, M. O. and Erlick, C. and Swietlicki, Erik and Rudich, Y.},
  issn         = {1352-2310},
  keyword      = {aerosol optical properties,biomass burning,refractive index,organic carbon,elemental carbons},
  language     = {eng},
  number       = {5},
  pages        = {1107--1118},
  publisher    = {Elsevier},
  series       = {Atmospheric Environment},
  title        = {Constraining the density and complex refractive index of elemental and organic carbon in biomass burning aerosol using optical and chemical measurements},
  url          = {http://dx.doi.org/10.1016/j.atmosenv.2006.09.035},
  volume       = {41},
  year         = {2007},
}