PhD Studentship: Impacts of Photoinitiated Chemical Processing on Climate Relevant Aerosol Properties

University of Bristol - School of Chemistry

The project:

Atmospheric aerosols impact health and climate. Accurately modelling aerosol number concentrations, size distributions and chemical composition is challenging but necessary to predict these impacts. Aerosols are complex mixtures of multiple functionalities and thousands of individual molecules. The identities and relative contributions of these molecules to aerosol mass are constantly changing based on atmospheric conditions, gas phase composition, condensational sink, and solar irradiation.

Gas phase photochemistry is central to our understanding of atmospheric reactivity. For example, the key atmospheric oxidants that drive atmospheric chemistry result from gas phase photochemistry. However, photochemistry in aerosols is largely unexplored, despite obvious interactions between aerosols and sunlight. Most studies have focused on bulk measurements and ignored the unique properties of aerosols, such as supersaturated solute states that are commonly accessed in aerosol, highly viscous phases that may reduce diffusion within an aerosol particle, and nanofocusing of light due to the curved particle surface.

The goal of this project is to develop a predictive framework to describe in a size and wavelength resolved manner the impacts of aerosol-light coupling on climate relevant aerosol physicochemical properties, such as particle size and refractive index.

The framework will be developed from detailed experiments on model aerosol and by coupling precisely measured changes in these properties using holographic optical trapping (HOT) to molecular measurements of aerosol chemical composition using mass spectrometry (MS). These experiments capitalise on instrumental developments pioneered at Bristol to precisely measure the size, refractive index, and surface and bulk properties of an individual particle. This approach allows a direct connection between chemistry occurring in a particle and its key physical properties.

Specific goals are to:

  1. Investigate in a size-resolved manner how photolysis of specific atmospherically significant chemical functionalities (eg nitrate, ketones) change the size, hygroscopicity, and phase of particles (HOT).
  2. Resolve the role of the particle-air interface (ie surfactants) in driving photochemistry (HOT).
  3. Test the scaling of light-particle interactions derived from HOT to more atmospherically-relevant sizes through aerosol chamber/MS studies.
  4. Collaborate with Biral (CASE partner) to explore adding additional functionality to their commercial optical tweezers instrument.

How to apply:

More information on the position can be found here: Please make an online application for this project at Please select Chemistry PhD on the Programme Choice page and enter details of the studentship when prompted in the Funding and Research Details sections of the form.

Candidate requirements:  MSc in chemistry, physics or related field; interests in analytical, physical or environmental chemistry

Funding: NERC GW4+ Doctoral Training Partnership

Contacts: Dr. Bryan R. Bzdek, School of Chemistry, University of Bristol;

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