The impact of viscous self-assembled phase formation on the ageing and atmospheric lifetimes of organic aerosol proxies

Milsom, Adam ORCID: 0000-0003-3875-9015 (2022). The impact of viscous self-assembled phase formation on the ageing and atmospheric lifetimes of organic aerosol proxies. University of Birmingham. Ph.D.

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Abstract

Atmospheric aerosols are key components of the atmosphere. They nucleate cloud droplets and facilitate the transport of particle-bound components around the atmosphere. This has an impact on the climate and air quality. The phase state of atmospheric aerosols can affect their ability to form cloud droplets and their atmospheric lifetime. Organic compounds are found in aerosol emissions. Some of these compounds, such as fatty acids, are surface active and can affect the cloud formation potential of an aerosol particle. Specifically, oleic acid is an unsaturated fatty acid found as a major component of cooking emissions. Recently, a study on an oleic acid aerosol proxy has shown that the formation of viscous 3-D self-assembled nanostructures is possible, affecting oleic acid reactivity.

This thesis takes this novel concept of nanostructure formation in atmospheric aerosol proxies and aims to explore what the potential atmospheric impact could be. This was done by applying X-ray scattering techniques to levitated droplets and surface coatings of the fatty acid aerosol proxy. Development of a method for determining reaction kinetics from these measurements is presented along with a first quantification of the effect of self-assembly on reaction kinetics, later being extended to different nanostructures. Experiments on reactivity and water uptake described here probe the proxy from nanometre-scale films to micrometre-scale droplets and bulk mixtures, demonstrating the versatility of the range of experimental techniques used to probe the proxy. The atmospheric implications of nanostructure formation are discussed via numerical modelling and observations from experiments on these proxies, highlighting the potential impact on aerosol atmospheric lifetime and implications for the atmosphere.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):