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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

Författare

  • G. Schkolnik
  • D. Chand
  • A. Hoffer
  • M. O. Andreae
  • C. Erlick
  • Erik Swietlicki
  • Y. Rudich

Summary, in English

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.

Avdelning/ar

Publiceringsår

2007

Språk

Engelska

Sidor

1107-1118

Publikation/Tidskrift/Serie

Atmospheric Environment

Volym

41

Issue

5

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Meteorology and Atmospheric Sciences

Nyckelord

  • aerosol optical properties
  • biomass burning
  • refractive index
  • organic carbon
  • elemental carbons

Status

Published

Forskningsgrupp

  • Aerosol, Nuclear Physics

ISBN/ISSN/Övrigt

  • ISSN: 1352-2310