Night-time oxidation at the air–water interface: co-surfactant effects in binary mixtures

Sebastiani, Federica; Campbell, Richard A.; Pfrang, Christian

doi:10.1039/d2ea00056c

Cited by 4 publications

(4 citation statements)

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“…Most literature studies on oleic acid oxidation have focused on pure liquid oleic acid in its native form either as particles, deposited films, or monolayers, ,− occasionally mixed with cosurfactants . Our work represents a new avenue, focusing on how the surfactant itself is organized and how this self-organization could impact the key aerosol processes of water uptake and chemical reaction outdoors and indoors.…”

Section: Summary and Future Workmentioning

confidence: 99%

“…This meant that our oxidation experiments involved ozone concentrations orders of magnitude greater than typical ambient values (ppm vs ppb levels) to measure kinetics in these lower-reactivity systems. Future work should look at longer-term aging and the inclusion of other atmospheric oxidants such as OH and NO 3 radicals at atmospherically relevant concentrations. , Oxidation by species such as chlorine, derived from cleaning products, would be of indoor air quality relevance. Linking experiments and mechanistic models with larger-scale atmospheric models . Kinetic multilayer modeling has helped us describe the impact of surfactant self-organization on processes at the aerosol and film levels.…”

Section: Summary and Future Workmentioning

confidence: 99%

“…Future work should look at longer-term aging and the inclusion of other atmospheric oxidants such as OH and NO 3 radicals at atmospherically relevant concentrations. 66 , 69 Oxidation by species such as chlorine, derived from cleaning products, would be of indoor air quality relevance. Linking experiments and mechanistic models with larger-scale atmospheric models .…”

Section: Summary and Future Workmentioning

confidence: 99%

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Molecular Self-Organization in Surfactant Atmospheric Aerosol Proxies

Milsom,

Squires,

Ward

et al. 2023

Acc. Chem. Res.

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Conspectus Aerosols are ubiquitous in the atmosphere. Outdoors, they take part in the climate system via cloud droplet formation, and they contribute to indoor and outdoor air pollution, impacting human health and man-made environmental change. In the indoor environment, aerosols are formed by common activities such as cooking and cleaning. People can spend up to ca . 90% of their time indoors, especially in the western world. Therefore, there is a need to understand how indoor aerosols are processed in addition to outdoor aerosols. Surfactants make significant contributions to aerosol emissions, with sources ranging from cooking to sea spray. These molecules alter the cloud droplet formation potential by changing the surface tension of aqueous droplets and thus increasing their ability to grow. They can also coat solid surfaces such as windows (“window grime”) and dust particles. Such surface films are more important indoors due to the higher surface-to-volume ratio compared to the outdoor environment, increasing the likelihood of surface film–pollutant interactions. A common cooking and marine emission, oleic acid, is known to self-organize into a range of 3-D nanostructures. These nanostructures are highly viscous and as such can impact the kinetics of aerosol and film aging (i.e., water uptake and oxidation). There is still a discrepancy between the longer atmospheric lifetime of oleic acid compared with laboratory experiment-based predictions. We have created a body of experimental and modeling work focusing on the novel proposition of surfactant self-organization in the atmosphere. Self-organized proxies were studied as nanometer-to-micrometer films, levitated droplets, and bulk mixtures. This access to a wide range of geometries and scales has resulted in the following main conclusions: (i) an atmospherically abundant surfactant can self-organize into a range of viscous nanostructures in the presence of other compounds commonly encountered in atmospheric aerosols; (ii) surfactant self-organization significantly reduces the reactivity of the organic phase, increasing the chemical lifetime of these surfactant molecules and other particle constituents; (iii) while self-assembly was found over a wide range of conditions and compositions, the specific, observed nanostructure is highly sensitive to mixture composition; and (iv) a “crust” of product material forms on the surface of reacting particles and films, limiting the diffusion of reactive gases to the particle or film bulk and subsequent reactivity. These findings suggest that hazardous, reactive materials may be protected in aerosol matrixes underneath a highly viscous shell, thus extending the atmospheric residence times of otherwise short-lived species.

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Section: Summary and Future Workmentioning

confidence: 99%

Section: Summary and Future Workmentioning

confidence: 99%

Section: Summary and Future Workmentioning

confidence: 99%

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Molecular Self-Organization in Surfactant Atmospheric Aerosol Proxies

Milsom,

Squires,

Ward

et al. 2023

Acc. Chem. Res.

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“…Of particular interest are double bonds present on the surface of aerosols, as these are highly reactive towards atmospheric radicals, such as O 3 , OH and NO 3 . 6,12,16,[18][19][20][21][22][23][24][25] The oxidation of groups on the surface of aerosols alters their properties, both as participants in further chemical reactions and as cloud condensation nuclei (CCN).…”

Section: Introductionmentioning

confidence: 99%

Surface functionality of sub- to full-monolayer organic coverage of water aerosols determined by molecular dynamics simulations

Stewart

Paterson

Greaves

2023

Environ. Sci.: Atmos.

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Technical note: In situ measurements and modelling of the oxidation kinetics in films of a cooking aerosol proxy using a quartz crystal microbalance with dissipation monitoring (QCM-D)

Milsom,

Qi,

Mishra

et al. 2023

Atmos. Chem. Phys.

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Abstract. Aerosols and films are found in indoor and outdoor environments. How they interact with pollutants, such as ozone, has a direct impact on our environment via cloud droplet formation and the chemical persistence of toxic aerosol constituents. The chemical reactivity of aerosol emissions is typically measured spectroscopically or by techniques such as mass spectrometry, directly monitoring the amount of material during a chemical reaction. We present a study which indirectly measures oxidation kinetics in a common cooking aerosol proxy using a low-cost quartz crystal microbalance with dissipation monitoring (QCM-D). We validated this approach by comparison with kinetics measured both spectroscopically and with high-intensity synchrotron radiation. Using microscopy, we found that the film morphology changed and film rigidity increased during oxidation. There was evidence of surface crust formation on oxidised particles, though this was not consistent for all experiments. Crucially, our kinetic modelling of these experimental data confirmed that the oleic acid decay rate is in line with previous literature determinations, which demonstrates that performing such experiments on a QCM-D does not alter the underlying mechanism. There is clear potential to take this robust and low-cost but sensitive method to the field for in situ monitoring of reactions outdoors and indoors.

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Night-time oxidation at the air–water interface: co-surfactant effects in binary mixtures

Abstract: The ageing of organic-coated aqueous aerosols at night is investigated by reacting NO3 with binary surfactant mixtures floating on water. The surfactants are oleic acid (OA), methyl oleate (MO) and...

Cited by 4 publications

References 94 publications

Molecular Self-Organization in Surfactant Atmospheric Aerosol Proxies

Molecular Self-Organization in Surfactant Atmospheric Aerosol Proxies

Surface functionality of sub- to full-monolayer organic coverage of water aerosols determined by molecular dynamics simulations

Technical note: In situ measurements and modelling of the oxidation kinetics in films of a cooking aerosol proxy using a quartz crystal microbalance with dissipation monitoring (QCM-D)

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