Atmospheric processing of organic aerosols

Ellison, G. Barney; Tuck, A. F.; Vaida, Veronica

doi:10.1029/1999jd900073

Cited by 435 publications

(655 citation statements)

References 68 publications

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“…Application of reaction probability values to organic particles will then be dependent on the phase of the organic aerosols. Surface active materials that form condensed films on aerosol particles, forming micelie-like structures [Gill and Graedel, 1983;Ellison et al, 1999], will show only surface reactive uptake. Reactivity calculations for water soluble or liquid organics will require knowledge of additional solubility parameters in the bulk.…”

Section: Discussionmentioning

confidence: 99%

Reactive uptake of ozone by proxies for organic aerosols: Surface versus bulk processes

Moise¹,

Rudich²

2000

J. Geophys. Res.

128

215

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Abstract. Uptake measurements of ozone were conducted with two types of proxies for atmospheric organic aerosols: organic liquids and self-assembled organic monolayers. Alkanes and terminal alkenes were used. The monolayer surface was characterized, prior to and after reaction, using IR spectroscopy. Uptake experiments were conducted using a flow tube reactor coupled to a chemical ionization mass spectrometer. The reactive uptake coefficient, ¾, is shown to be due to reaction with the double bond. For the monolayers, ¾ is composed solely of a surface reactive component and is smaller by at least an order of magnitude than values obtained for a liquid of the same chain length. Uptake by the liquids is higher due to solubility and reaction in the bulk. The phase of the atmospheric organic aerosol will determine the appropriate use of a bulk or surface uptake probability in atmospheric models. Since the aerosol surface is processed and sites are consumed, ¾ is time variant. We define a parameter ¾' as the surface uptake probability per reactive site and determine its value as 9 x 10 -•9 cm: molecule '•. This enables the modeling of surface reactions as surface site concentrations diminish following interaction with the gaseous species.

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Section: Discussionmentioning

confidence: 99%

Reactive uptake of ozone by proxies for organic aerosols: Surface versus bulk processes

Moise¹,

Rudich²

2000

J. Geophys. Res.

128

215

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“…Photochemical enhancement of NO 3 À photolysis may also occur with other anions, including organics, 78 that are often present in particles or on snowpacks. 25,[79][80][81][82][83] The photolysis of nitrate has been proposed to be a major source of NO x in snowpacks, where surprisingly high levels of oxides of nitrogen and photochemical activity have been measured. [22][23][24][25]55,[84][85][86][87][88] Model studies of this process assume that the absorption cross sections and quantum yields measured for pure NaNO 3 can be applied to the atmosphere, including the air within the snowpack.…”

Section: Atmospheric Implicationsmentioning

confidence: 99%

Enhanced surface photochemistry in chloride–nitrate ion mixtures

Wingen

Moskun

Johnson

et al. 2008

Phys. Chem. Chem. Phys.

116

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Heterogeneous reactions of sea salt aerosol with various oxides of nitrogen lead to replacement of chloride ion by nitrate ion. Studies of the photochemistry of a model system were carried out using deliquesced mixtures of NaCl and NaNO 3 on a Teflon s substrate. Varying molar ratios of NaCl to NaNO 3 (1 : 9 Cl À : NO 3 À , 1 : 1 Cl À : NO 3 À , 3 : 1 Cl À : NO 3 À , 9 : 1 Cl À : NO 3 À) and NaNO 3 at the same total concentration were irradiated in air at 299 AE 3 K and at a relative humidity of 75 AE 8% using broadband UVB light (270-380 nm). Gaseous NO 2 production was measured as a function of time using a chemiluminescence NO y detector. Surprisingly, an enhanced yield of NO 2 was observed as the chloride to nitrate ratio increased. Molecular dynamics (MD) simulations show that as the Cl À : NO 3 À ratio increases, the nitrate ions are drawn closer to the interface due to the existence of a double layer of interfacial Cl À and subsurface Na + . This leads to a decreased solvent cage effect when the nitrate ion photodissociates to NO 2 +O À , increasing the effective quantum yield and hence the production of gaseous NO 2 . The implications of enhanced NO 2 and likely OH production as sea salt aerosols become processed in the atmosphere are discussed.

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“…8,9 Surface active molecules, such as fatty acids, may partition to the gas-aerosol interface of aqueous particles, lowering the surface tension and creating an organic surface layer. [16][17][18] However, fatty acids and fatty acid salts also exhibit complex phase behavior that depends on temperature, pH, and ionic content. [19][20][21] The formation of liquid crystal phases may be important for fatty acids in atmospheric aerosols, as well as separation into aqueous and oil-like phases, which could result in an organic surface coating.…”

Section: Introductionmentioning

confidence: 99%

The Oxidation of Oleate in Submicron Aqueous Salt Aerosols: Evidence of a Surface Process

2007

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We have studied the oxidation of submicron aqueous aerosols consisting of internal mixtures of sodium oleate (oleic acid proxy), sodium dodecyl sulfate, and inorganic salts by O 3 , NO 3 /N 2 O 5 , and OH. Experiments were performed using an aerosol flow tube and a continuous flow photochemical reaction chamber coupled to a chemical ionization mass spectrometer (CIMS). The CIMS was fitted with a heated inlet for volatilization and detection of organics in the particle phase simultaneously with the gas phase. A differential mobility analyzer/condensation particle counter was used for determining aerosol size distributions. The oxidation of oleate by O 3 follows Langmuir-Hinshelwood kinetics, with γ O 3 ≈ 10 -5 calculated from the observed loss rate of oleate in the particle phase. The best fit Langmuir-Hinshelwood parameters are k max I ) 0.05 ( 0.01 s -1 and K O 3 ) 4((3) × 10 -14 cm 3 molec -1 . These parameters showed no dependence on the ionic composition of the aerosols or on the presence of alkyl surfactants. Several ozone oxidation products were observed to be particle-bound at ambient temperature, including nonanoic acid. We observed efficient processing of oleate by OH (0.1 e γ OH e 1), and we suggest an upper bound of γ Ν 3 < 10 -3 . We conclude that for the aerosol compositions studied, oxidation occurs near the gas-aerosol interface and that the 1 e-fold lifetime of unsaturated organics at the aerosol surface is ∼10 min due to O 3 oxidation under atmospheric conditions. In the context of a Langmuir-Hinshelwood mechanism, different underlying aerosol compositions may extend the lifetime of oleic acid at the surface by reducing K O 3 .

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Atmospheric processing of organic aerosols

Cited by 435 publications

References 68 publications

Reactive uptake of ozone by proxies for organic aerosols: Surface versus bulk processes

Reactive uptake of ozone by proxies for organic aerosols: Surface versus bulk processes

Enhanced surface photochemistry in chloride–nitrate ion mixtures

The Oxidation of Oleate in Submicron Aqueous Salt Aerosols: Evidence of a Surface Process

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