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 and Ångstrom 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, and 0.03 m2/g, respectively. While agreeing with the common consensus that BC 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.

Brown carbon in atmospheric outflow from the Indo-Gangetic Plain: Mass absorption efficiency and temporal variability

“…Likewise, Hecobian et al, (2010) had reported a σ abs-BrC of ~ 0.60 and 0.58 m 2 g -1 for urban and rural sites, respectively (those characterized by high concentrations of levuglucosan). It is noteworthy that the mass absorption efficiency of BrC (σ abs-BrC ) documented for the IGPoutflow is consistent with that for biomass burning emissions reported in the literature [Hoffer et al, 2006;Lack et al, 2012;Yang et al, 2009]; as summarized in Table 1.…”

“…Los-Angeles, USA BBE 365 0.71 7.6 ± 0.5 Zhang et al, 2013 North America BBE 404 0.82 ± 0.43 - Lack et al, 2012 Beijing, China BBE 550 0.5 - Yang et al, 2009 Beijing, China BBE 365 1.8 ± 0.2 (summer) 7.5 ± 0.9 Cheng et al, 2011 Beijing, China BBE 365 0.7 ± 0.2 (Winter) 7.0 ± 0. Amazon basin BBE 350 -400 ~ 0.5 -1.5 ~ 6 -7 Hoffer et al, 2006…”

“…Among the carbonaceous species, two distinct forms of carbon [elemental or black carbon (EC or BC) and brown carbon (BrC)] are of particular interest due to their light absorbing properties. The EC absorbs solar radiation in the visible region [Bond, 2001;Bond et al, 2013], whereas BrC shows prominent absorption in the near UV-region [Alexander et al, 2008;Andreae and Gelencsér, 2006;Hecobian et al, 2010;Lack et al, 2012;Liu et al, 2014;Lukács et al, 2007;Yang et al, 2009]. However, real time data on absorption properties of BrC are rather limited.…”

Research progress of light-absorbing impurities in glaciers of the Tibetan Plateau and its surroundings

“…物质、生物质气溶胶等, 具有较弱的吸光性(MAC小 于1 m −2 g −1 , 550 nm) [3,15,16] . 与黑碳相比, 吸光性有机 碳能够强烈吸收近紫外太阳辐射, 进而引起辐射强 迫的改变, 增加碳质气溶胶的光吸收效率 [17,18] . 粉 尘 是 吸 光 性 杂 质 的 另 外 一 种 重 要 组 分 [19,20] , 主要源自沙漠干旱区以及土壤扬尘等 [21] .…”

“…粉 尘 是 吸 光 性 杂 质 的 另 外 一 种 重 要 组 分 [19,20] , 主要源自沙漠干旱区以及土壤扬尘等 [21] . 粉尘具有 较弱的吸光性(对亚洲粉尘而言MAC为0.009 m 2 g −1 , 550 nm)并呈深色(更易吸收短波辐射), 因全球大气 中粉尘载荷量巨大(~1800 Tg a −1 ), 所以由粉尘引起 的辐射强迫也较为显著 [17,22,23] . 沉降到冰川表面的吸光性杂质能够显著降低雪 冰反照率, 进而导致雪冰消融增强 [24~29] .…”