Enhanced Uptake of PAHs by Organic-Coated Aqueous Surfaces

Mmereki, Baagi T.; Chaudhuri, Sri R.; Donaldson, D. J.

doi:10.1021/jp027361g

Cited by 59 publications

(95 citation statements)

References 33 publications

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“…This is an upper limit for the surface coverage in our experiments, as equilibrium conditions had not been reached after 15 min of deposition, at which time we still observed a linear increase in phenanthrene fluorescence at the air-ice interface. As discussed in Mmereki et al [35], this suggests that the experiments reported here were done in the unsaturated regime of phenanthrene surface coverage. On organic films [30], rates of anthracene ozonation are independent of surface coverage within a submonolayer regime.…”

Section: Ozonation Kinetics Of Phenanthrene On Water and Icesupporting

confidence: 52%

Heterogeneous ozonation kinetics of phenanthrene at the air–ice interface

Kahan

Donaldson

2008

Environ. Res. Lett.

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Phenanthrene ozonation kinetics were measured on ice at −30 and −10 • C, and on a water surface at 22 • C using glancing angle laser-induced fluorescence. A Langmuir-Hinshelwood type kinetic mechanism was observed on ice. The maximum ozonation rates were a factor of ten higher on ice than on water. No temperature dependence to the kinetics was observed between −30 and −10 • C, suggesting that the differences in the rates on ice and water are due to different physical properties at the two surfaces. Fluorescence spectra of phenanthrene show significant self-association on ice that is not observed on water, adding further evidence for the hypothesis that the quasi-liquid layer at the air-ice interface presents a very different environment to liquid water.

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Section: Ozonation Kinetics Of Phenanthrene On Water and Icesupporting

confidence: 52%

Heterogeneous ozonation kinetics of phenanthrene at the air–ice interface

Kahan

Donaldson

2008

Environ. Res. Lett.

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“…The simulations in which the impinging water molecules became entrained within the monolayer were extended for an additional 125 ps (to 200 ps), with no observable change in state. Studies have previously reported instances of organic films effectively acting as a solvent for other gas phase molecules [e.g., Mmereki et al, 2003]. The pair radial distribution functions between the oxygen atom of the entrained water molecule and atoms of the octanoic acid indicate that the water molecules preferentially lie near the hydrophilic head group of the amphiphile, which suggests an explanation for its apparent preference for adsorption rather than desorption (Figure 8).…”

Section: Takahama and Russell: Water Mass Accommodation On Films D022mentioning

confidence: 83%

A molecular dynamics study of water mass accommodation on condensed phase water coated by fatty acid monolayers

Takahama

Russell

2011

J. Geophys. Res.

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[1] As the water uptake by particles and clouds influences the radiative balance of the Earth, it is desirable to understand the mechanisms and parameters, which regulate water uptake in these colloidal particles. In this work, molecular dynamics simulations were used to simulate scattering or accommodation of water vapor molecules impinging on a slab of water and slabs of water coated by monomolecular amphiphile films: octanoic acid (C 8 ) at surface densities of 29 and 18 Å 2 per molecule and myristic acid (C 14 ) at 29 Å 2 per molecule. The mass accommodation coefficient of near unity on a pure water slab is in agreement with values estimated using similar scattering simulations using other potentials for water. The addition of surface-active organic molecules in quantities corresponding to less than 1% of mass in a typical cloud droplet are predicted to reduce this mass accommodation coefficient by 70-100% in similar types of scattering simulations. The mass accommodation coefficient decreased monotonically with projected surface coverage of the hydrocarbon backbones, although the accommodation mechanisms differed by packing density and type of organic molecule. The mechanisms of interaction of the impinging water vapor molecules with the simulated organic films are discussed in the context of their chemical characteristics and physical structures (e.g., fatty acid chain orientation).Citation: Takahama, S., and L. M. Russell (2011), A molecular dynamics study of water mass accommodation on condensed phase water coated by fatty acid monolayers,

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“…The film coating can also act as a barrier to water uptake by and evaporation of the droplet and can inhibit the transport of various atmospheric species from the gas to the aqueous phase [6][7][8][9][10][11][12][13]. Conversely, the film can act as a "2D solvent" for atmospheric species that would not normally partition to the aqueous phase, or can alter the solvation behaviour of those that would [14][15][16][17][18]. Very recently, Forestieri et al [19] studied the surface tension effects on sea spray aerosol mimics (oleic, palmitic, myristic acids, and their mixtures) using a surface film model to establish the properties that surface-active organic molecules must have to substantially impact on the aerosol's activation efficiency.…”

Section: Introductionmentioning

confidence: 99%

Night-Time Oxidation of a Monolayer Model for the Air–Water Interface of Marine Aerosols—A Study by Simultaneous Neutron Reflectometry and in Situ Infra-Red Reflection Absorption Spectroscopy (IRRAS)

et al. 2018

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This paper describes experiments on the ageing of a monolayer model for the air–water interface of marine aerosols composed of a typical glycolipid, galactocerebroside (GCB). Lipopolysaccharides have been observed in marine aerosols, and GCB is used as a proxy for these more complex lipopolysaccharides. GCB monolayers are investigated as pure films, as mixed films with palmitic acid, which is abundant in marine aerosols and forms a stable attractively mixed film with GCB, particularly with divalent salts present in the subphase, and as mixed films with palmitoleic acid, an unsaturated analogue of palmitic acid. Such mixed films are more realistic models of atmospheric aerosols than simpler single-component systems. Neutron reflectometry (NR) has been combined in situ with Fourier transform infra-red reflection absorption spectroscopy (IRRAS) in a pioneering analysis and reaction setup designed by us specifically to study mixed organic monolayers at the air–water interface. The two techniques in combination allow for more sophisticated observation of multi-component monolayers than has previously been possible. The structure at the air–water interface was also investigated by complementary Brewster angle microscopy (BAM). This study looks specifically at the oxidation of the organic films by nitrate radicals (NO3•), the key atmospheric oxidant present at night. We conclude that NO3• oxidation cannot fully remove a cerebroside monolayer from the surface on atmospherically relevant timescales, leaving its saturated tail at the interface. This is true for pure and salt water subphases, as well as for single- and two-component films. The behaviour of the unsaturated tail section of the molecule is more variable and is affected by interactions with co-deposited species. Most surprisingly, we found that the presence of CaCl2 in the subphase extends the lifetime of the unsaturated tail substantially—a new explanation for longer residence times of materials in the atmosphere compared to lifetimes based on laboratory studies of simplified model systems. It is thus likely that aerosols produced from the sea-surface microlayer at night will remain covered in surfactant molecules on atmospherically relevant timescales with impact on the droplet’s surface tension and on the transport of chemical species across the air–water interface.

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Enhanced Uptake of PAHs by Organic-Coated Aqueous Surfaces

Cited by 59 publications

References 33 publications

Heterogeneous ozonation kinetics of phenanthrene at the air–ice interface

Heterogeneous ozonation kinetics of phenanthrene at the air–ice interface

A molecular dynamics study of water mass accommodation on condensed phase water coated by fatty acid monolayers

Night-Time Oxidation of a Monolayer Model for the Air–Water Interface of Marine Aerosols—A Study by Simultaneous Neutron Reflectometry and in Situ Infra-Red Reflection Absorption Spectroscopy (IRRAS)

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