A chemical kinetic model for reactive transformations of aerosol particles

Worsnop, Douglas R.; Morris, J.W.; Qiu, Shi; Davidovits, P.; Kolb, C. E.

doi:10.1029/2002gl015542

Cited by 140 publications

(253 citation statements)

References 17 publications

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“…that the surface is refreshed via mixing within the particle and/or OH can undergo substantial diffusion into the particle. However, a model based on reactive uptake of OH to a liquid particle, that includes the assumption that every OH colliding with the particle surface would encounter the initial particle component (Worsnop et al, 2002), does not reproduce the majority of our data well.…”

Section: Oxidation Of Pure Palmitic Acid Particlescontrasting

confidence: 44%

“…Schematic of the experimental set-up as those that are supercooled or structured (Hearn and Smith, 2005;Katrib et al, 2005;Knopf et al, 2005). Therefore, the reactive zone for OH oxidation, which is expected to be fast (Bertram et al, 2001;Molina et al, 2004;Lambe et al, 2007;George et al, 2007), may be confined to the particle surface or near-surface region (Hanson et al, 1994;Worsnop et al, 2002) leading to differences in the transformation rates between the surface and bulk (Maria et al, 2004). To our knowledge, this aspect has not been thoroughly examined by laboratory studies.…”

Section: Introductionmentioning

confidence: 98%

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Heterogeneous OH oxidation of palmitic acid in single component and internally mixed aerosol particles: vaporization and the role of particle phase

et al. 2008

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Abstract.We studied the OH oxidation of submicron aerosol particles consisting of pure palmitic acid (PA) or thin (near monolayer) coatings of PA on aqueous and effloresced inorganic salt particles. Experiments were performed as a function of particle size and OH exposure using a continuousflow photochemical reaction chamber coupled to a chemical ionization mass spectrometer (CIMS) system, for detection of gas and particle-bound organics, and a DMA/CPC for monitoring particle size distributions. The loss rate of PA observed for pure PA aerosols and PA on crystalline NaCl aerosols indicates that the OH oxidation of PA at the gas-aerosol interface is efficient. The pure PA oxidation data are well represented by a model consisting of four main processes: 1) surface-only reactions between OH and palmitic acid, 2) secondary reactions between palmitic acid and OH oxidation products, 3) volatilization of condensedphase mass, and 4) a surface renewal process. Using this model we infer a value of γ OH between 0.8 and 1. The oxidation of palmitic acid in thin film coatings of salt particles is also efficient, though the inferred γ OH is lower, ranging from ∼0.3 (+0.1/−0.05) for coatings on solid NaCl and ∼0.05 (±0.01) on aqueous NaCl particles. These results, together with simultaneous data on particle size change and volatilized oxidation products, provide support for the ideas that oxidative aging of aliphatic organic aerosol is a source of small oxidized volatile organic compounds (OVOCs), and that OH oxidation may initiate secondary condensed-phase reactions.

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Section: Oxidation Of Pure Palmitic Acid Particlescontrasting

confidence: 44%

Section: Introductionmentioning

confidence: 98%

Heterogeneous OH oxidation of palmitic acid in single component and internally mixed aerosol particles: vaporization and the role of particle phase

et al. 2008

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“…We postulate that the reacto-diffusion length L in a wellmixed particle is more appropriately defined as L= √ 2 D orgn ∆ t coll , where Dorgn is the onedimensional, radial self-diffusion coefficient of the organic component of the particle, and the time interval is determined by the reactive collision frequency of OH with the particle surface. This is distinct from several other definitions in the literature 22,24,61 in an important conceptual way. Relationships have been proposed that utilize the reaction rate constant between the gas molecule and the organic species in the aerosol, whether at the surface or in the bulk, to provide a fundamental clock in the coupled reaction-diffusion system.…”

Section: Discussionmentioning

confidence: 65%

Oxidation of a model alkane aerosol by OH radical: the emergent nature of reactive uptake

Houle

Hinsberg

Wilson

2015

Phys. Chem. Chem. Phys.

155

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An accurate description of the evolution of organic aerosol in the Earth's atmosphere is essential for climate models. However, the complexity of multiphase chemical and physical transformations has been challenging to describe at the level required to predict aerosol lifetimes and changes in chemical composition. In this work a model is presented that reproduces experimental data for the early stages of oxidative aging of squalane aerosol by hydroxyl radical (OH), a process governed by reactive uptake of gas phase species onto the particle surface. Simulations coupling free radical reactions and Fickian diffusion are used to elucidate how the measured uptake coefficient reflects the elementary steps of sticking of OH to the aerosol as a result of a gas-surface collision, followed by very rapid abstraction of hydrogen and subsequent free radical reactions. It is found that the uptake coefficient is not equivalent to a sticking coefficient or an accommodation coefficient: it is an intrinsically emergent process that depends upon particle size, viscosity, and OH concentration. An expression is derived to examine how these factors control reactive uptake over a broad range of atmospheric and laboratory conditions, and is shown to be consistent with simulation results. Well-mixed, liquid behavior is found to depend on the reaction conditions in addition to the nature of the organic species in the aerosol particle.

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“…The value of γ 0 calculated from experimental measurements using Eq. (1) was corrected for gas-phase diffusion by applying an empirical formulation by Fuchs and Sutugin (Fuchs and Sutugin, 1970;Worsnop et al, 2002 (Massman, 1998), which was calculated to be D OH =0.260 cm 2 s −1 for our flow conditions. This value is close to the experimental D OH value measured in dry air (Ivanov et al, 2007).…”

Section: Kinetic Studiesmentioning

confidence: 99%

Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: uptake kinetics, condensed-phase products, and particle size change

et al. 2007

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Abstract. The kinetics and reaction mechanism for the heterogeneous oxidation of saturated organic aerosols by gasphase OH radicals were investigated under NO x -free conditions. The reaction of 150 nm diameter Bis(2-ethylhexyl) sebacate (BES) particles with OH was studied as a proxy for chemical aging of atmospheric aerosols containing saturated organic matter. An aerosol reactor flow tube combined with an Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS) and scanning mobility particle sizer (SMPS) was used to study this system. Hydroxyl radicals were produced by 254 nm photolysis of O 3 in the presence of water vapour. The kinetics of the heterogeneous oxidation of the BES particles was studied by monitoring the loss of a mass fragment of BES with the ToF-AMS as a function of OH exposure. We measured an initial OH uptake coefficient of γ 0 =1.3 (±0.4), confirming that this reaction is highly efficient. The density of BES particles increased by up to 20% of the original BES particle density at the highest OH exposure studied, consistent with the particle becoming more oxidized. Electrospray ionization mass spectrometry analysis showed that the major particle-phase reaction products are multifunctional carbonyls and alcohols with higher molecular weights than the starting material. Volatilization of oxidation products accounted for a maximum of 17% decrease of the particle volume at the highest OH exposure studied. Tropospheric organic aerosols will become more oxidized from heterogeneous photochemical oxidation, which may affect not only their physical and chemical properties, but also their hygroscopicity and cloud nucleation activity.

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A chemical kinetic model for reactive transformations of aerosol particles

Cited by 140 publications

References 17 publications

Heterogeneous OH oxidation of palmitic acid in single component and internally mixed aerosol particles: vaporization and the role of particle phase

Heterogeneous OH oxidation of palmitic acid in single component and internally mixed aerosol particles: vaporization and the role of particle phase

Oxidation of a model alkane aerosol by OH radical: the emergent nature of reactive uptake

Heterogeneous oxidation of saturated organic aerosols by hydroxyl radicals: uptake kinetics, condensed-phase products, and particle size change

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