Fractal geometry of carbonaceous aggregates from an urban aerosol

Katrinak, Karen A.; Rez, Peter; Perkes, Paul R.; Buseck, Peter R.

doi:10.1021/es00040a013

Cited by 172 publications

(94 citation statements)

References 33 publications

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“…For example, using TEM we found that in polluted air from Mexico City, ns-soot occurred in 62% of all particles with aerodynamic diameters between 50 and 300 nm (Adachi and Buseck 2008), and similar abundances were observed in Phoenix (Katrinak et al 1993), Los Angeles (Adachi and Buseck 2013), and China (Li et al 2010). In relatively clean air in Mexico and in the remote marine troposphere above the Southern Ocean, ns-soot occurred in 35% and between 10% and 45% of analyzed accumulation-mode particles, respectively (P osfai et al 1999;Adachi and Buseck 2008).…”

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confidence: 66%

“…Geometric sizes or equivalent diameters can be determined for the aggregate particles. The easiest way to determine values is directly from TEM images (Katrinak et al 1993;Adachi and Buseck 2008;Adachi et al 2010). If desired, far more accurate three-dimensional (3D) values can be obtained using electron tomography (e.g., 138 § 50 nm in volumeequivalent diameter for ns-soot particles from Mexico City; Adachi et al 2010).…”

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confidence: 99%

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Ns-Soot: A Material-Based Term for Strongly Light-Absorbing Carbonaceous Particles

Buseck

Adachi

Gelencsér

et al. 2014

Aerosol Science and Technology

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103

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The climate-change and environmental literature, including that on aerosols, is replete with mention of black carbon (BC) and soot. The terms are used interchangeably in much of the literature, although BC and soot commonly have operational and source-based definitions, respectively, and reliable reference samples and aerosol standards do not exist for either one. The uncertainty about their exact chemical nature and properties can be decreased by materials-based measurement techniques and terminology. Here, we discuss ambiguities in common uses of BC and soot and propose the term ns-soot, where "ns" refers to carbon nanospheres, for a characteristic constituent of BC and soot. Based on its composition, morphology, and structure, we define ns-soot as particles that consist of nanospheres, typically with diameters <100 nm, that possess distinct structures of concentrically wrapped, graphene-like layers of carbon and with grape-like (aciniform) morphologies. We additionally propose that, because of their importance for climate modeling and health issues, distinctions are made among bare, coated, and embedded ns-soot particles.

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confidence: 66%

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confidence: 99%

Ns-Soot: A Material-Based Term for Strongly Light-Absorbing Carbonaceous Particles

Buseck

Adachi

Gelencsér

et al. 2014

Aerosol Science and Technology

Self Cite

103

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“…However, many studies have suggested that internally mixed LAC is usually coated with a shell of less absorbing component to form a core-shell structure rather than "well mixed". Images obtained from TEM supported that LAC particles could become coated once emitted (Katrinak et al, 1992(Katrinak et al, , 1993Martins et al, 1998). Volatility tandem DMA (differential mobility analyzer) measurements showed that the majority of particles are comprised of a non-volatile core and a volatile outer layer during heavily polluted days ).…”

Section: Introductionmentioning

confidence: 90%

“…The mixing state of soot particles was observed by Katrinak et al (1992Katrinak et al ( , 1993 and Clarke et al (2004) with the TEM. A Single-particle soot photometer can be used to distinguish the coated soot particles (Schwarz et al, 2008) by measuring the incandescence and scattering at infrared wavelengths of single particles.…”

Section: Introductionmentioning

confidence: 99%

A new method to determine the mixing state of light absorbing carbonaceous using the measured aerosol optical properties and number size distributions

Zhao

Müller

et al. 2012

Atmos. Chem. Phys.

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Abstract. In this paper, the mixing state of light absorbing carbonaceous (LAC) was investigated with a two-parameter aerosol optical model and in situ aerosol measurements at a regional site in the North China Plain (NCP). A closure study between the hemispheric backscattering fraction (HBF) measured by an integrating nephelometer and that calculated with a modified Mie model was conducted. A new method was proposed to retrieve the ratio of the externally mixed LAC mass to the total mass of LAC (r ext-LAC ) based on the assumption that the ambient aerosol particles were externally mixed and consisted of a pure LAC material and a core-shell morphology in which the core is LAC and the shell is a less absorbing material. A Monte Carlo simulation was applied to estimate the overall influences of input parameters of the algorithm to the retrieved r ext-LAC . The diurnal variation of r ext-LAC was analyzed and the PartMC-MOSAIC model was used to simulate the variation of the aerosol mixing state. Results show that, for internally mixed particles, the assumption of core-shell mixture is more appropriate than that of homogenous mixture which has been widely used in aerosol optical calculations. A significant diurnal pattern of the retrieved r ext-LAC was found, with high values during the daytime and low values at night. The consistency between the retrieved r ext-LAC and the model results indicates that the diurnal variation of LAC mixing state is mainly caused by the diurnal evolution of the mixing layer.

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“…Soot agglomerates are a type of nonspherical particles that are often found in the ambient aerosol (Katrinak et al, 1993). TiO 2 and Ag particles in industrial applications also have agglomerate morphologies (Pratsinis, 1998;Ku and Maynard, 2006).…”

Section: Introductionmentioning

confidence: 99%

Estimates of Non-Ideal Effects on the Friction Coefficient of Agglomerates

Shin

Mulholland

Kim

et al. 2011

Aerosol Air Qual. Res.

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There are several characteristics of silver agglomerates that are not incorporated in existing models for agglomerate dynamics. These characteristics include particle alignment in the electric field, necking between particles, polydispersity of the primary particles, and variable primary sphere size. Estimates of these features on the agglomerate dynamics were computed as perturbations to the Chan-Dahneke agglomerate model. The variable primary sphere size effect results in the largest change from the idealized model with about a 10% increase in scaling exponents for both friction coefficientnumber of primary particles (η) and mass-mobility diameter (D fm ). The second largest change is a 4% decrease in the exponent η and a 4% increase in the exponent (D fm ) from the alignment in the electric field. The effects of necking between particles and polydispersity of the primary particles are negligible for the two exponents. The combined effect, excluding the variable primary particle size, results in a 17.5% decrease in the dynamic shape factor for agglomerates with a 300 nm mobility diameter. Adjusting the model by this amount provides a significant improvement in the agreement between the model and silver agglomerate measurements for the dynamic shape factor. Experimentally the number of primary spheres is determined from the mass of the agglomerate assuming a constant primary sphere diameter. The predicted apparent exponent η based on a 10% variability in the primary sphere size is about a 5% less than the apparent exponent assuming a constant primary sphere size. This is a significant effect relative to the observed 15% decrease in η (Shin et al., 2009a) as the agglomerate size increases from the free molecular regime into the transition regime.

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Fractal geometry of carbonaceous aggregates from an urban aerosol

Cited by 172 publications

References 33 publications

Ns-Soot: A Material-Based Term for Strongly Light-Absorbing Carbonaceous Particles

Ns-Soot: A Material-Based Term for Strongly Light-Absorbing Carbonaceous Particles

A new method to determine the mixing state of light absorbing carbonaceous using the measured aerosol optical properties and number size distributions

Estimates of Non-Ideal Effects on the Friction Coefficient of Agglomerates

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