Aerosol Science 35 (2004) 765 – 780 www.elsevier.com/locate/jaerosci Modeling reectance and transmittance of quartz-ÿber ÿlter samples containing elemental carbon particles: Implications for thermal/optical analysis L.-W. Antony Chen * , Judith C. Chow, John G. Watson, Hans Moosm  uller, W. Patrick Arnott Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512, USA Received 13 September 2003; received in revised form 24 December 2003; accepted 29 December 2003 Abstract A radiative transfer scheme that considers absorption, scattering, and distribution of light-absorbing ele- mental carbon (EC) particles collected on a quartz-ÿber ÿlter was developed to explain simultaneous ÿlter reectance and transmittance observations prior to and during thermal/optical analysis for carbonaceous aerosol. The model is applied to study ambient ÿlter samples from the United States and Hong Kong, China, and how they dier from each other and from reference carbon black samples. Most particles in ambient samples deposit into the top half of the ÿlter, resuspended carbon black particles are only found close to the ÿlter surface. Pyrolized/charred organic carbon (POC) generated during thermal analysis reduces ÿlter reectance and transmittance in a fashion that suggests a uniform distribution of POC throughout the ÿlter. When heated in oxygen, most EC evolves earlier than the within-ÿlter charring for certain ambient samples. This shows the dierent natures of EC, and also results in an inexact optical correction to separate organic and elemen- tal carbon by thermal analysis, especially when the POC/EC ratio is large. Particle absorption in the ÿlter is estimated for comparisons with the EC/POC measurements, suggesting a mass absorption eciency of ∼ 2:7 ± 0:2m 2 (gC) -1 for reference carbon black and ¿ 15 m 2 (gC) -1 for ambient EC, similar to previous estimates in the literature. ? 2004 Elsevier Ltd. All rights reserved. Keywords: Elemental carbon; Thermal/optical analysis; Filter radiative transfer; Pyrolysis 1. Introduction Carbonaceous material has been identiÿed as a major component of ambient ÿne aerosol from remote to urban environments and is involved in various aerosol health, visibility, and climate impacts * Corresponding author. Tel.: +1-775-674-7028; fax: +1-775-674-7009. E-mail address: antony@dri.edu (L.-W.A. Chen). 0021-8502/$ - see front matter ? 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaerosci.2003.12.005