Structural variations in individual carbonaceous particles from an urban aerosol

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

doi:10.1021/es00034a014

Cited by 109 publications

(75 citation statements)

References 33 publications

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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: 92%

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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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Section: Introductionmentioning

confidence: 92%

“…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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“…A total of 114 points were analyzed by using EELS at 10 nm intervals. The π* and σ * intensities were obtained by using the same method as Katrinak et al (1992). We used intensities at 184.5, 294.5/σ *, and 402.5 eV in the EELS spectra for determining the relative abundances of S, K, and N, respectively.…”

Section: Particle Size Measurementsmentioning

confidence: 99%

Internally mixed soot, sulfates, and organic matter in aerosol particles from Mexico City

2008

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Abstract. Soot particles, which are aggregated carbonaceous spherules with graphitic structures, are major aerosol constituents that result from burning of fossil fuel, biofuel, and biomass. Their properties commonly change through reaction with other particles or gases, resulting in complex internal mixtures. Using a transmission electron microscope (TEM) for both imaging and chemical analysis, we measured ∼8000 particles (25 samples) with aerodynamic diameters from 0.05 to 0.3 µm that were collected in March 2006 from aircraft over Mexico City (MC) and adjacent areas. Most particles are coated, consist of aggregates, or both. For example, almost all analyzed particles contain S and 70% also contain K, suggesting coagulation and condensation of sulfates and particles derived from biomass and biofuel burning. In the MC plumes, over half of all particles contained soot coated by organic matter and sulfates. The median value of the soot volume fraction in such coated particles is about 15%. In contrast to the assumptions used in many climate models, the soot particles did not become compact even when coated. Moreover, about 80% by volume of the particles consisting of organic matter with sulfate also contained soot, indicating the important role of soot in the formation of secondary aerosol particles. Coatings on soot particles can amplify their light absorption, and coagulation with sulfates changes their hygroscopic properties, resulting in shorter lifetimes. Through changes in their optical and hygroscopic properties, internally mixed soot particles have a greater effect on the regional climate of MC than uncoated soot particles.

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“…Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) yield detailed images of the physical structure of individual particles van Poppel et al, 2005;Hopkins et al, 2008). Electron microscopy with energy dispersive X-ray (EDX) microanalysis or electron energy loss spectroscopy (EELS) yields spatially resolved chemical composition of individual particles Katrinak et al, 1992). One general limitation of EDX is that quantitative analysis of low-Z elements (carbon, nitrogen, and oxygen) is not always possible and requires time-intensive Monte-Carlo calculations (Ro et al, 2003(Ro et al, , 2004.…”

Section: R C Moffet Et Al: Microscopic Characterization Of Carbonamentioning

confidence: 99%

Microscopic characterization of carbonaceous aerosol particle aging in the outflow from Mexico City

et al. 2010

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Abstract. This study was part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) field campaign conducted in Mexico City metropolitan area during spring 2006. The physical and chemical transformations of particles aged in the outflow from Mexico City were investigated for the transport event of 22 March 2006. A detailed chemical analysis of individual particles was performed using a combination of complementary microscopy and micro-spectroscopy techniques. The applied techniques included scanning transmission X-ray microscopy (STXM) coupled with near edge X-ray absorption fine structure spectroscopy (NEXAFS) and computer controlled scanning electron microscopy with an energy dispersive X-ray analyzer (CCSEM/EDX). As the aerosol plume evolves from the city center, the organic mass per particle increases and the fraction of carbon-carbon double bonds (associated with elemental carbon) decreases. Organic functional groups enhanced with particle age include: carboxylic acids, alkyl groups, and oxygen bonded alkyl groups. At the city center (T0) the most prevalent aerosol type contained inorganic species (composed of sulfur, nitrogen, oxygen, and potassium) coated with organic material. At the T1 and T2 sites, located northeast of T0 (∼29 km and ∼65 km, respectively), the fraction of homogenously mixed organic particles increased in both Correspondence to: M. K. Gilles (mkgilles@lbl.gov) size and number. These observations illustrate the evolution of the physical mixing state and organic bonding in individual particles in a photochemically active environment.

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Structural variations in individual carbonaceous particles from an urban aerosol

Cited by 109 publications

References 33 publications

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

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

Internally mixed soot, sulfates, and organic matter in aerosol particles from Mexico City

Microscopic characterization of carbonaceous aerosol particle aging in the outflow from Mexico City

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