Strong spectral dependence of light absorption by organic carbon particles formed by propane combustion

Abstract

Abstract. We have measured the extinction and absorption cross sections of carbon particles emitted by a propane diffusion flame both in an aerosol chamber and on size-segregated samples deposited on optical windows. The absorption cross section, the single scattering albedo, and the Ångström exponent show drastic dependencies both on the C/O ratio and on the particle size. This is interpretated as being due to the appearance of nucleation modes of smaller organic particles at higher C/O ratios, which were detected by SMPS measurements and partially by TEM analysis. The spectral range of the validity of the absorption power-law (Ångström exponent) model is investigated by vacuum ultraviolet extinction measurements. These measurements give also indications for a preferentially aromatic nature of the OC component of the flame products.

Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols

“…Our AEA of kerosene is comparable the value of 1.01 measured by Schnaiter et al (2006) for a propane diffusion flame at C/O = 0.29. Ajtai et al (2010) presented a higher value of 1.24 for spectral range 266-1064 nm with the same C/O ratio but slightly different burner type than Schnaiter et al (2006) by measuring the slope of the log-log plot, as applied in our study. The data shows a curvature of the incense absorption coefficients as a function of wavelength, resulting in a larger AEA for shorter wavelengths than for longer ones.…”

“…Similarly, AES is 1.88 for kerosene soot and 2.0 for incense aerosols, indicating larger aerosol size for kerosene soot aerosol than for incense aerosol. AES of kerosene is very close to the value of 1.70 reported by Schnaiter et al (2006). Figure 2b compares SSA for kerosene soot and incense burning aerosols.…”

Black carbon or brown carbon? The nature of light-absorbing carbonaceous aerosols

“…When absorption is stronger at shorter wavelengths, i.e., the particles appear brownish or yellow,Å will be significantly greater than unity. Values of 2.0 and more were found in aerosol collected near a lignite combustion plant (Bond et al, 1999b), in biomass smoke (Kirchstetter et al, 2004;Schmid et al, 2005;Schnaiter et al, 2005b), environmental tobacco smoke (Lawless et al, 2004), rural aerosol (Lindberg et al, 1993), and in particles produced by oxygen-deficient combustion of propane (Schnaiter et al, 2006). The highest values ofÅ are found for the yellowish to brownish products of pure smoldering combustion, e.g., tobacco smoke (3.5, Lawless et al, 2004) or water-soluble HULIS from biomass burning (6-7, Hoffer et al, 2005).…”

Truncation and Angular-Scattering Corrections for Absorbing Aerosol in the TSI 3563 Nephelometer

“…For example, Bond et al (1999), Weingartner et al (2003), and Sheridan (2005) have used the difference method as a reference value of absorption when calibrating filter-based measurements. Schnaiter et al (2006) used it to measure absorption by coated black carbon, since the response of a filter-based absorption measurement to mixed aerosol is not well known.…”