Attribution of aerosol light absorption to black carbon, brown carbon, and dust in China – interpretations of atmospheric measurements during EAST-AIRE

Abstract

Abstract. Black carbon, brown carbon, and mineral dust are three of the most important light absorbing aerosols. Their optical properties differ greatly and are distinctive functions of the wavelength of light. Most optical instruments that quantify light absorption, however, are unable to distinguish one type of absorbing aerosol from another. It is thus instructive to separate total absorption from these different light absorbers to gain a better understanding of the optical characteristics of each aerosol type. During the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) campaign near Beijing, we measured light scattering using a nephelometer, and light absorption using an aethalometer and a particulate soot absorption photometer. We also measured the total mass concentrations of carbonaceous (elemental and organic carbon) and inorganic particulates, as well as aerosol number and mass distributions. We were able to identify periods during the campaign that were dominated by dust, biomass burning, fresh (industrial) chimney plumes, other coal burning pollution, and relatively clean (background) air for Northern China. Each of these air masses possessed distinct intensive optical properties, including the single scatter albedo andÅngstrom exponents. Based on the wavelength-dependence and particle size distribution, we apportioned total light absorption to black carbon, brown carbon, and dust; their mass absorption efficiencies at 550 nm were estimated to be 9.5, 0.5 (a lower limit value), and 0.03 m 2 /g, respectively. While agreeing with the common consensus that black carbon is the most important light absorber in the mid-visible, we demonstrated that brown carbon and dust could also cause significant absorption, especially at shorter wavelengths.

Measuring Organic Carbon and Black Carbon in Rainwater: Evaluation of Methods

“…Previous studies have reported visible light absorption by non-BC particles (Yang et al 2009;Doherty et al 2010;Lack et al 2013). Doherty et al (2010) estimated that between 20% and 50% of the light absorption by particles in snowpack is caused by organic ("brown") carbon and dust.…”

The "dual-spot" Aethalometer: an improved measurement of aerosol black carbon with real-time loading compensation

“…The BC mass concentration is calculated from the change in optical attenuation at 880 nm in the selected time interval using the mass absorption cross section 7.77 m 2 g −1 . At this wavelength, other aerosol particles (carbonaceous or mineral) absorb significantly less and absorption can be attributed to BC alone (Sandradewi et al, 2008a and b;Fialho et al, 2005;Yang et al, 2009;and references therein). Measurements at distinct spectral regions (370,470,520,590,660,880 and 950 nm) allow for spectral analysis of the data -the analysis of the dependence of absorption on the wavelength can be of importance for research on direct effects of aerosol BC, climate forcing (Bond et al, 2013;IPCC, 2013) or mineral dust detection (Collaud Coen et al, 2004), through the determination of the single scattering albedo dependence on the wavelength, or source apportionment (Sandradewi et al, 2008b).…”

Aerosol Optical Properties Observed at a Semi-Arid Rural Site in Northeastern China

“…To date, a large number of studies have focused on aerosol mass concentrations and their physical and chemical properties in various regions of China Yao et al, 2002;Cao et al, , 2004Dan et al, 2004;Guo et al, 2004;Sun et al, 2004;Yao et al, 2004;Cao et al, 2005;Duan et al, 2005;Xu et al, 2005;Yang et al, 2005;Wang et al, 2006;Meng et al, 2007;Zhang et al, 2008aZhang et al, , b, 2009Zhang et al, , 2010a. Yet, only limited in situ measurements have been conducted on aerosol optical properties despite their critical roles in aerosol radiative forcing and their potential impacts on climate and environment (Bergin et al, 2001;Xu et al, 2002Xu et al, , 2004Yan, 2006;Li et al, 2007;Andreae et al, 2008;Garland et al, 2008;Yan et al, 2008;Che et al, 2009;Garland et al, 2009;Yang et al, 2009;Fan et al, 2010;Ma et al, 2011). Few study also showed the relationship between aerosol chemical and optical properties (Cheng et al, 2008;Huang et al, 2010;Tao et al, 2012).…”

“…(4) and (5) to calculate σ ab . Yang et al (2009) reported values of α ab measured at a site (Xianghe) 70 km east of Beijing. The mean value of α ab during the whole experiment was 1.47.…”