Emissions from the laboratory combustion of wildland fuels: Particle morphology and size

Chakrabarty, Rajan K.; Moosmüller, Hans; Garro, Mark A.; Arnott, W. P.; Walker, John S.; Susott, Ronald A.; Babbitt, Ronald E.; Wold, Cyle; Lincoln, Emily; Hao, Wei Min

doi:10.1029/2005jd006659

Cited by 208 publications

(267 citation statements)

References 45 publications

(86 reference statements)

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“…Pósfai et al (2003Pósfai et al ( , 2004 named this kind of particles as tar balls, a distinct carbonaceous particle type from soot. Tar balls originate from biomass burning, especially during smouldering burning conditions (Pósfai et al, 2003(Pósfai et al, , 2004Chakrabarty et al, 2006). The relative proportion of the tar balls remained quite low or moderate (1-4% tar balls) during the pollution episode compared with the proportion observed at some other sites (Pósfai et al, 2003;Pósfai et al, 2004;Hand et al, 2005).…”

Section: Tar Ballsmentioning

confidence: 99%

Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis

Niemi

Saarikoski

Tervahattu³

et al. 2006

Atmos. Chem. Phys.

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Abstract.Aerosol samples were collected at a rural background site in southern Finland in May 2004 during pollution episode (PM 1 ∼16 µg m −3 , backward air mass trajectories from south-east), intermediate period (PM 1 ∼5 µg m −3 , backtrajectories from north-east) and clean period (PM 1 ∼2 µg m −3 , backtrajectories from northwest/north). The elemental composition, morphology and mixing state of individual aerosol particles in three size fractions were studied using transmission electron microscopy (TEM) coupled with energy dispersive X-ray (EDX) microanalyses. The TEM/EDX results were complemented with the size-segregated bulk chemical measurements of selected ions and organic and elemental carbon. Many of the particles in PM 0.2−1 and PM 1−3.3 size fractions were strongly internally mixed with S, C and/or N. The major particle types in PM 0.2−1 samples were 1) soot and 2) (ammonium)sulphates and their mixtures with variable amounts of C, K, soot and/or other inclusions. Number proportions of those two particle groups in PM 0.2−1 samples were 0-12% and 83-97%, respectively. During the pollution episode, the proportion of Ca-rich particles was very high (26-48%) in the PM 1−3.3 and PM 3.3−11 samples, while the PM 0.2−1 and PM 1−3.3 samples contained elevated proportions of silicates (22-33%), metal oxides/hydroxides (1-9%) and tar balls (1-4%). These aerosols originated mainly from polluted areas of Eastern Europe, and some open biomass burning smoke was also brought by long-range transport. During the clean period, when air masses arrived from the Arctic Ocean, PM 1−3.3 samples contained mainly sea salt particles (67-89%) with a variable rate of Cl substitution (mainly by NO porous (sponge-like) Na-rich particles (35%) with abundant S, K and O. They might originate from the burning of wood pulp wastes of paper industry. The proportion of biological particles and C-rich fragments (probably also biological origin) were highest in the PM 3.3−11 samples (0-81% and 0-22%, respectively). The origin of different particle types and the effect of aging processes on particle composition and their hygroscopic and optical properties are discussed.

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Section: Tar Ballsmentioning

confidence: 99%

Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis

Niemi

Saarikoski

Tervahattu³

et al. 2006

Atmos. Chem. Phys.

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“…Aerosol size measuring instruments (such as Scanning Mobility Particle Size Spectrometer) have repeatedly shown that a lognormal size distribution is a good fit for realistic BC size distributions (Bond et al, 2002;Chakrabarty et al, 10 2006;Reddington et al, 2013;Wang et al, 2015), and it is also widely used in numerical calculations of BC radiative properties and forcing (Moffet and Prather, 2009;Chung et al, 2012;Li et a., 2016). Observations for BC have shown equivalent volume diameters from 0.01µm up to 1.0µm (Chakrabarty et al, 2006;Reddington et al, 2013;Wang et al, 2015). To describe a lognormal size distribution, a mean size and a standard deviation are needed.…”

Section: Bc Size Distributionmentioning

confidence: 99%

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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“…2. Soot carbon is composed of primary spherules with radii R p 0.025 µm that are aggregated with other spherules into large particles, and the resulting agglomerates look like chains of spheres with multiple branches (hence the term "chain aggregates;" Li et al, 2003a, b;Wentzel et al, 2003;Chakrabarty et al, 2006;Adachi et al, 2010;Wu et al, 2012;Chakrabarty et al, 2013). The absorption cross section for the aggregated particles can be reasonably modeled as a collection of the primary sC spheres, even though the agglomerates have complex shapes (Mulholland et al, 1994;Fuller, 1995;Farias et al, 1996;Fuller et al, 1999;Sorensen, 2001;Schnaiter et al, 2003;Chakrabarty et al, 2007;Liu et al, 2008;Chung et al, 2012a).…”

Section: Aae For Spectrally Invariant Kmentioning

confidence: 99%

Remote sensing of soot carbon – Part 2: Understanding the absorption Ångström exponent

et al. 2016

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Abstract. Recently, some authors have suggested that the absorption Ångström exponent (AAE) can be used to deduce the component aerosol absorption optical depths (AAODs) of carbonaceous aerosols in the AERONET database. This AAE approach presumes that AAE 1 for soot carbon, which contrasts the traditional small particle limit of AAE = 1 for soot carbon. Thus, we provide an overview of the AERONET retrieval, and we investigate how the microphysics of carbonaceous aerosols can be interpreted in the AERONET AAE product. We find that AAE 1 in the AERONET database requires large coarse mode fractions and/or imaginary refractive indices that increase with wavelength. Neither of these characteristics are consistent with the current definition of soot carbon, so we explore other possibilities for the cause of AAE 1. AAE is related to particle size, and coarse mode particles have a smaller AAE than fine mode particles for a given aerosol mixture of species. We also note that the mineral goethite has an imaginary refractive index that increases with wavelength, is very common in dust regions, and can easily contribute to AAE 1. We find that AAE 1 can not be caused by soot carbon, unless soot carbon has an imaginary refractive index that increases with wavelength throughout the visible and near-infrared spectrums. Finally, AAE is not a robust parameter for separating carbonaceous absorption from dust aerosol absorption in the AERONET database.

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Emissions from the laboratory combustion of wildland fuels: Particle morphology and size

Cited by 208 publications

References 45 publications

Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis

Changes in background aerosol composition in Finland during polluted and clean periods studied by TEM/EDX individual particle analysis

The Absorption Ångström Exponent of black carbon: from numerical aspects

Remote sensing of soot carbon – Part 2: Understanding the absorption Ångström exponent

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