Fullerenes and Soot Formation— New Pathways to Large Particles in Flames

Homann, K. H.

doi:10.1002/(sici)1521-3773(19981002)37:18<2434::aid-anie2434>3.0.co;2-l

Cited by 289 publications

(143 citation statements)

References 36 publications

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“…BaP readily adsorbs onto soot particles and can be regarded as a proxy for the wider class of polycyclic aromatic compounds, but also for soot due to its structural similarities of the surface . Soot can be pictured as agglomerate of graphene layers, while BaP (C 20 H 12 ) represents a single graphene layer consisting of five six-membered aromatic rings (Homann, 1998;Pöschl et al, 2001). Here, BaP provides consumable reactive sites for adsorption processes and surface reactions.…”

Section: Representation Of Sootmentioning

confidence: 99%

Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O3, NO2, and H2O on soot coated with benzo[a]pyrene

2009

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Abstract. This study assesses in detail the effects of heterogeneous chemistry on the particle surface and gas-phase composition by modeling the reversible co-adsorption of O 3 , NO 2 , and H 2 O on soot coated with benzo[a]pyrene (BaP) for an urban plume scenario over a period of five days. By coupling the Pöschl-Rudich-Ammann (PRA) kinetic framework for aerosols ) to a box model version of the gas phase mechanism RADM2, we are able to track individual concentrations of gas-phase and surface species over the course of several days. The flux-based PRA formulation takes into account changes in the uptake kinetics due to changes in the chemical gas-phase and particle surface compositions. This dynamic uptake coefficient approach is employed for the first time in a broader atmospheric context of an urban plume scenario. Our model scenarios include one to three adsorbents and three to five coupled surface reactions. The results show a variation of the O 3 and NO 2 uptake coefficients of more than five orders of magnitude over the course of the simulation time and a decrease in the uptake coefficients in the various scenarios by more than three orders of magnitude within the first six hours. Thereafter, periodic peaks of the uptake coefficients follow the diurnal cycle of gas-phase O 3 -NO x reactions. Physisorption of water vapor reduces the half-life of the coating substance BaP by up to a factor of seven by permanently occupying ∼75% of the soot surface. Soot emissions modeled by replenishing reactive surface sites lead to maximum gas-phase O 3 depletions Correspondence to: D. A. Knopf (daniel.knopf@stonybrook.edu) of 41 ppbv and 7.8 ppbv for an hourly and six-hourly replenishment cycle, respectively. This conceptual study highlights the interdependence of co-adsorbing species and their nonlinear gas-phase feedback. It yields further insight into the atmospheric importance of the chemical oxidation of particles and emphasizes the necessity to implement detailed heterogeneous kinetics in future modeling studies.

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Section: Representation Of Sootmentioning

confidence: 99%

Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O3, NO2, and H2O on soot coated with benzo[a]pyrene

2009

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“…Moreover, PAH as well as its oxygenated or nitrated derivatives are well defined model substances for the molecular structure of soot, which is the black solid product of incomplete combustion or pyrolysis of organic matter (Homann, 1998;Messerer et al, 2005;Pöschl, 2005;Sadezky et al, 2005). Soot contributes to regional and global climate change because of its role in direct, indirect and semi-direct radiative forcing (Hansen et al, 1997;Ackerman et al, 2000;Jacobson, 2000).…”

Section: Introductionmentioning

confidence: 99%

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3

2009

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Abstract. We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl-Rudich-Ammann, 2007) for aerosol and cloud surface chemistry and gas-particle interactions.For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentrationand time-dependence of the heterogeneous reaction between PAHs and O 3 can be efficiently described with a LangmuirHinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O 3 vary over three orders of magnitude (K ads,O3 ≈ 10 −15 -10 −13 cm 3 ), and the second-order rate coefficients for the surface layer reaction of O 3 with different PAH vary over two orders of magnitude (k SLR,PAH,O3 ≈ 10 −18 -10 −17 cm 2 s −1 ). The available data indicate that the Langmuir adsorption constants for NO 2 are similar to those of O 3 , while those of H 2 O are several orders of magnitude smaller (K ads,H2O ≈ 10 −18 -10 −17 cm 3 ). The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO 2 and O 3 and physisorption of H 2 O. Note, however, that the exact reaction mechanisms, rate limiting steps and possible intermediates still remain to be resolved (e.g., surface diffusion and formation of O atoms or O − 3 ions at the surface).Correspondence to: M. Shiraiwa (m.shiraiwa@mpic.de)The K2-SURF model enables the calculation of ozone uptake coefficients, γ O3 , and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of γ O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, γ O3 of PAH-coated aerosol particles are expected to be in the range of 10 −6 -10 −5 .At ambient temperatures, NO 2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O 3 . The accelerating effect can be attributed to highly reactive NO 3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O 3 -NO 2 and PAH-NO 3 surface layer reactions are in the range of 10 −17 -10 −16 cm 2 s −1 and 10 −15 -10 −12 cm 2 s −1 , respectively.The chemical half-life of PAHs is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions wit...

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“…In practice, however, 656 N. P. IVLEVA ET AL. there is no sharp cut but a continuous decrease of thermochemical refractiveness and specific optical absorption going from graphite-like structures to nonrefractive and colorless organic compounds, respectively (Pöschl 2003(Pöschl , 2005. Both, BC and EC, comprise the carbon content of the graphite-like material usually contained in soot (technically defined as the black product of incomplete hydrocarbon combustion or pyrolysis) and other combustion aerosol particles, which can be pictured as more or less disordered stacks of graphene layers or large polycyclic aromatics (Homann 1998;Sadezky et al 2005). Depending on the applied optical or thermochemical methods (absorption wavelength, temperature gradient, etc.…”

Section: Introductionmentioning

confidence: 99%

Raman Microspectroscopic Analysis of Size-Resolved Atmospheric Aerosol Particle Samples Collected with an ELPI: Soot, Humic-Like Substances, and Inorganic Compounds

Ivleva

McKeon

Nießner

et al. 2007

Aerosol Science and Technology

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Raman microspectroscopy and mapping have been applied for the analysis of soot, humic-like substances (HULIS) and inorganic compounds in size resolved samples of air particulate matter collected with an electrical low pressure impactor (ELPI). Using several reference materials, we found that spectral parameters determined by curve fitting with five bands (G, D1-D4) enable a discrimination of soot and HULIS and provide information about the relative abundance and structural order of graphite-like carbon. In particular, the D1 band width exhibited a near-linear negative correlation with the ratio of apparent elemental carbon to total carbon in different types of soot.The ELPI samples of sub-micrometer atmospheric particles exhibited essentially the same Raman spectra and parameters as standard diesel soot. In winter samples this was also the case for larger particles with aerodynamic diameters up to 4 μm. Spring and autumn samples, however, exhibited increased D1 band widths and D3 band intensities, indicating a high prevalence of HULIS in the size range of 2-4 μm. In addition, various nitrates and sulfates (mostly NaNO 3 and (NH 4 ) 2 SO 4 ; some NH 4 NO 3 , Ca(NO 3 ) 2 , Na 2 SO 4 , and CaSO 4 ) and small amounts of CaCO 3 were detected. Different single-and multi-component spectra indicated the presence of externally and internally mixed particles. The relative abundance of different chemical components in different particle size ranges was quantified in mapping experiments (0-55% NaNO 3 , 1-15% (NH 4 ) 2 SO 4 , 10-45% soot/HULIS, 30-60% highly fluorescent organics). Overall, the results of this study demonstrate that Raman microspectroscopy and mapping can provide qualitative and quantitative information about the composition of ELPI aerosol samples.

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Fullerenes and Soot Formation— New Pathways to Large Particles in Flames

Cited by 289 publications

References 36 publications

Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O<sub>3</sub>, NO<sub>2</sub>, and H<sub>2</sub>O on soot coated with benzo[a]pyrene

Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O<sub>3</sub>, NO<sub>2</sub>, and H<sub>2</sub>O on soot coated with benzo[a]pyrene

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O<sub>3</sub>, NO<sub>2</sub>, H<sub>2</sub>O, OH and NO<sub>3</sub>

Raman Microspectroscopic Analysis of Size-Resolved Atmospheric Aerosol Particle Samples Collected with an ELPI: Soot, Humic-Like Substances, and Inorganic Compounds

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Fullerenes and Soot Formation— New Pathways to Large Particles in Flames

Cited by 289 publications

References 36 publications

Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O&lt;sub&gt;3&lt;/sub&gt;, NO&lt;sub&gt;2&lt;/sub&gt;, and H&lt;sub&gt;2&lt;/sub&gt;O on soot coated with benzo[a]pyrene

Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O&lt;sub&gt;3&lt;/sub&gt;, NO&lt;sub&gt;2&lt;/sub&gt;, and H&lt;sub&gt;2&lt;/sub&gt;O on soot coated with benzo[a]pyrene

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O&lt;sub&gt;3&lt;/sub&gt;, NO&lt;sub&gt;2&lt;/sub&gt;, H&lt;sub&gt;2&lt;/sub&gt;O, OH and NO&lt;sub&gt;3&lt;/sub&gt;

Raman Microspectroscopic Analysis of Size-Resolved Atmospheric Aerosol Particle Samples Collected with an ELPI: Soot, Humic-Like Substances, and Inorganic Compounds

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Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O<sub>3</sub>, NO<sub>2</sub>, and H<sub>2</sub>O on soot coated with benzo[a]pyrene

Detailed heterogeneous chemistry in an urban plume box model: reversible co-adsorption of O<sub>3</sub>, NO<sub>2</sub>, and H<sub>2</sub>O on soot coated with benzo[a]pyrene

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O<sub>3</sub>, NO<sub>2</sub>, H<sub>2</sub>O, OH and NO<sub>3</sub>