Soot Particle Optical Properties: a Comparison between Numerical Calculations and Experimental Data Collected during the Boston College Experiment
Abstract
A black carbon instrument inter-comparison study was conducted in July 2008 at Boston College to measure the optical, physical and chemical properties of laboratory generated soot under controlled conditions [1]. The physical, chemical and optical properties were measured on size-selected particles for: 1. Nascent soot particles 2. Nascent- denuded soot particles 3. Soot particles coated with sulfuric acid or DOS (dioctyl sebacate) across a range of coating thicknesses 4. Coated and then denuded soot particles. Instruments involved in the inter-comparison study fell into two broad categories: a) mass-based instruments and b) optically-based instruments. During this experiment, 7 mass-based and 9 optically-based instruments were deployed. Absorption scattering and extinction measurements were carried out in combination with mass-based instruments in order to obtain absorption, scattering and extinction coefficients for coated and denuded soot particles as a function of their mass, size and coating thickness. Particle samples were also collected on nuclepore filters to perform Scanning Electron Microscopy (SEM) analysis. The images obtained with the SEM elucidated the changes in particle morphology upon coating and denuding. The images were also used to determine morphological parameters for single soot aggregates (e.g. monomers number and diameter) used in the numerical estimation of aerosol optical properties. With the data collected during the experiment, we carry out a comparative study of the optical properties of soot particles obtained experimentally with those calculated using the two most commonly used numerical approximations (Rayleigh-Debye-Gans (RDG) theory and Mie theory). Thus we validate the degree of agreement between theoretical models and experimental results. The laboratory optical, mass, size and morphological data can be used to elucidate the impact of these parameters on radiative forcing by atmospheric soot [2, 3]. References: 1. Cross, E. S., T. B. Onasch, et al. "Soot Particle Studies- Instrument Inter-Comparison- Project Overview." Aerosol Science and Technology 44(8): 592-611. 2. Flowers, B. A., M. K. Dubey, et al. (2010). "Correlations between aerosol optical properties and chemical composition in mixed carbonaceous aerosol: Observations on Jeju Island, Korea with a 3-laser photoacoustic spectrometer." Atmos. Chem. Phys. Under revision. 3. Jacobson, M. Z. (2001). "Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols." Nature 409(6821): 695-697.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A13C0235S
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles