Absorption amplification of black carbon internally mixed with secondary organic aerosol

Schnaiter, M.; Linke, Christian; Möhler, Ottmar; Naumann, K.‐H.; Saathoff, H.; Wagner, R. J.; Schurath, U.; Wehner, B.

doi:10.1029/2005jd006046

Cited by 415 publications

(438 citation statements)

References 30 publications

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“…5). These absorption coefficient amplification factors are comparable with previous laboratory and in-situ observational studies, which suggests a range of absorption enhancements from 1.05 to 3.50 due to BC mixing morphology (Bond et al, 2013;Shiraiwa et al, 2010;Schnaiter, 2005;Peng et al, 2016). Accordingly, shortwave heating rate also increased from about 0.15 K h -1 to over 0.22 K h -1 , which considerably accelerates 15 the warming effect induced by BC (Fig.…”

Section: Amplified Dome Effect By Mixing With Scattering Aerosolssupporting

confidence: 78%

Dome effect of black carbon and its key influencing factors: A one-dimensional modelling study

Wang¹,

Huang²,

Ding³

2017

Preprint

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Black carbon (BC) has been identified to play a critical role in aerosol-planet boundary layer (PBL) interaction and further deterioration of near-surface air pollution in megacities, which has been named as its "dome effect". However, the impacts of key factors that influence this effect, such as the vertical distribution and aging processes of BC, and also the underlying land surface, have not been quantitatively explored yet. Here, based on available in-situ measurements of meteorology and 15 atmospheric aerosols together with the meteorology-chemistry online coupled model, WRF-Chem, we conduct a set of parallel simulations to quantify the roles of these factors in influencing the BC's dome effect and surface haze pollution, and discuss the main implications of the results to air pollution mitigation in China. We found that the impact of BC on PBL is very sensitive to the altitude of aerosol layer. The upper level BC, especially those near the capping inversion, is more essential in suppressing the PBL height and weakening the turbulence mixing. The dome effect of BC tends to be significantly intensified 20 as BC aerosol mixed with scattering aerosols during winter haze events, resulting in a decrease of PBL height by more than 25%. In addition, the dome effect is more substantial (up to 15%) in rural areas than that in the urban areas with the same BC loading, indicating an unexpected regional impact of such kind of effect to air quality in countryside. This study suggests that China's regional air pollution would greatly benefit from BC emission reductions, especially those from the elevated sources from the chimneys and also the domestic combustions in rural areas, through weakening the aerosol-boundary layer 25 interactions that triggered by BC.

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Section: Amplified Dome Effect By Mixing With Scattering Aerosolssupporting

confidence: 78%

Dome effect of black carbon and its key influencing factors: A one-dimensional modelling study

Wang¹,

Huang²,

Ding³

2017

Preprint

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“…Theoretically, condensation reduces the diameter spread between big particles and small particles over time (Seinfeld and Pandis, 2016), on the contrary to the assumption by Lack and Cappa (2010). Schnaiter et al (2005) coated BC particles with secondary organic aerosol material in a lab, and found that the coating increases particle sizes, while reduces geometric standard deviation (see 20 Fig. 5 of their paper), as predicted by theoretical calculation of condensation process.…”

mentioning

confidence: 82%

“…To obtain a realistic relationship between core size and coating thickness, we choose to use the experiment results by Schnaiter et al (2005). They coated diesel soot particles by secondary organic compounds in a chamber, and Figure realistic one in present study to compute the AAE of Coated BC, and so further coating is not addressed here.…”

Section: Bc Geometrymentioning

confidence: 99%

“…Their work provided a meaningful experimental dataset to derive coating thickness of BC particles. Furthermore, Schnaiter et al (2005) also measured the absorption of coated BC particles at 450, 550 and 700 nm (see Fig. 9 of their paper), and from these three wavelengths we do see that coating does decrease BC AAE (from approximately 1.1 to 0.8), thereby undermining the AAE results in Lack and Cappa's (2010) study .…”

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confidence: 99%

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The Absorption Ångström Exponent of black carbon: from numerical aspects

Liu¹,

Chung²,

Yin³

2017

Preprint

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Abstract. The Absorption Ångström Exponent (AAE) is an important aerosol optical parameter used for aerosol 10 characterization and apportionment studies. The AAE of black carbon (BC) is widely accepted to be 1.0, although observational estimates give a quite wide range of 0.6~1.1. With considerable uncertainties related to observations, a numerical study is a powerful method, if not the only one, to provide a better and more accurate understanding on BC AAE.This study calculates BC AAE using realistic particle geometries based on fractal aggregate and an accurate numerical optical model (namely the Multiple-Sphere T-Matrix method). At odds with the expectations, BC AAE is not 1.0, even when 15 BC is assumed to have small sizes and a wavelength independent refractive index. With a wavelength independent refractive index, the AAE of fresh BC is approximately 1.05, and is quite insensitive to particle size distribution. BC AAE goes lower when BC particles are aged (compact structures or coated by other scattering materials). For coated BC, we prescribed the coating thickness distribution based on a published experimental study, where smaller BC cores were shown to develop thicker coating than bigger BC cores. Both Compact and Coated BC the AAE ranges, at realistic particle sizes. For both 20Compact and Coated BC, the AAE is highly sensitive to particle size distribution, ranging from approximately 0.8 to 1.0 for relatively large BC with wavelength-independent refractive index. When the refractive index is allowed to vary with wavelength, a feature with observational backing, the BC AAE shows a much wider range. We propose that the presented results herein serve as a comprehensive guide for the response of BC AAE to BC size, refractive index, and geometry.

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“…Amplification factors of MAE can reach to 1.8-2.1 when EC particles internally mixed with secondary organic aerosol (SOA) (Schnaiter et al 2005). However, the MAE of EC would decrease significantly when the size of the particle exceeds 150 nm (Bond and Bergstrom 2006).…”

Section: Impact Of Chemical Compositions On Mae Of Ecmentioning

confidence: 99%

Characteristics of Mass Absorption Efficiency of Elemental Carbon in Urban Chengdu, Southwest China: Implication for the Coating Effects on Aerosol Absorption

Tao

Zhang

et al. 2018

Aerosol Sci Eng

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To investigate the mass absorption efficiency (MAE) of elemental carbon (EC) at Chengdu in China's Sichuan Basin, daily PM 2.5 filter samples were collected during the typical month for each season in 2011. PM 2.5 samples were subject to chemical analysis for water-soluble inorganic ions, organic carbon and EC, as well as biomass burning organic tracer (i.e., levoglucosan). Additionally, PM 2.5 samples were further conducted for aerosol absorption coefficient (b ap ) measurement at the wavelengths of 370 and 880 nm. To evaluate the seasonal variations of MAEs of EC, linear regression analyses were applied to EC (determined by thermal method), black carbon (BC, determined by optical method) and b ap for four seasons. The average BC concentration was 10 µg m −3 when using the manufacturer's recommended value (16.6 m 2 g −1 at the wavelength of 880 nm), which was 1.4 times the mean EC concentration. The MAE of EC at 880 nm was estimated to be 6.1 m 2 g −1 in autumn, which was evidently lower than 6.7-6.9 m 2 g −1 in other seasons. The higher MAE in other seasons was likely due to more effective light absorption by internally mixed EC with both transparent coatings (e.g., sulfate and nitrate) and organic matters coatings.

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Absorption amplification of black carbon internally mixed with secondary organic aerosol

Cited by 415 publications

References 30 publications

Dome effect of black carbon and its key influencing factors: A one-dimensional modelling study

Dome effect of black carbon and its key influencing factors: A one-dimensional modelling study

The Absorption Ångström Exponent of black carbon: from numerical aspects

Characteristics of Mass Absorption Efficiency of Elemental Carbon in Urban Chengdu, Southwest China: Implication for the Coating Effects on Aerosol Absorption

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