Atmospheric aerosols influence the climate via cloud droplet nucleation and can facilitate the long-range transport of harmful pollutants. The lifetime of such aerosols can therefore determine their environmental impact. Fatty acids are found in organic aerosol emissions with oleic acid, an unsaturated fatty acid, being a large contributor to cooking emissions. As a surfactant, oleic acid can self-organise into nanostructured lamellar bilayers with its sodium salt, and this self-organisation can influence reaction kinetics. We developed a kinetic multi-layer model-based description of decay data we obtained from laboratory experiments of the ozonolysis of coated films of this self-organised system, demonstrating a decreased diffusivity for both oleic acid and ozone due to lamellar bilayer formation. Diffusivity was further inhibited by a viscous oligomer product forming in the surface layers of the film. Our results indicate that nanostructure formation can increase the reactive half-life of oleic acid by an order of days at typical indoor and outdoor atmospheric ozone concentrations. We are now able to place nanostructure formation in an atmospherically meaningful and quantifiable context. These results have implications for the transport of harmful pollutants and the climate.
Bibliographical noteFunding Information:
Financial support. This research has been supported by the Natural Environment Research Council (grant nos. NE/L002566/1 and NE/T00732X/1).
Acknowledgements. Adam Milsom was funded by the NERC SCENARIO DTP (NE/L002566/1) and NERC grant (NE/T00732X/1) and was supported by the NERC CENTA DTP. This work was carried out with the support of the Diamond Light Source (DLS), instrument I22 (proposal SM21663). The authors are grateful to the Central Laser Facility for access to key equipment for the Raman work carried out simultaneously with the DLS beamtime experiments. Nick Terrill (DLS), Andy Smith (DLS) and Tim Snow (DLS) are acknowledged for their support during the beamtime. The computations described in this paper were performed using the University of Birmingham’s BlueBEAR HPC service, which provides a high-performance computing service to the university’s research community.
© 2022 Adam Milsom et al.
ASJC Scopus subject areas
- Atmospheric Science