Aerosol that is formed either in the airways or from the ocean surface can have significant impacts
on climate, the environment, and human health. As the risk of respiratory pandemics and extreme
weather escalates due to persistent deforestation and climate change, driven by overconsumption
of meat and dairy products and unabated fossil fuel burning, the role of aerosol science becomes
crucial in mitigating the consequences.
One understudied aspect of physical aerosol science are the factors affecting the electric charge.
The electrostatic force on an aerosol affects dynamics, agglomeration, hygroscopicity, and
deposition, potentially impacting the viability of pathogens within. The ‘charge state’ indicates
excess charges on a particle’s surface and the fraction of particles with each charge state are
collectively referred to as the ‘electric charge distribution’.
Factors influencing electric charge distribution include particle size, shape, composition, salt
concentration, fluid pH, and generation method. One main aim of this study is to quantify their
impact on the charge of dried particles. Size and salt concentration were most impactful. Measured
charge distributions of synthetic lung fluids and artificial seawater show aerosol size, salt
concentrations, and protein presence significantly affect charge distribution.
Tyler Johnson’s 2020 method of measuring electric charge distributions classifies aerosols by
aerodynamic diameter, followed by electric mobility diameter classification. Another aim of this
study is to reduce the measurement time. A refined technique developed in this thesis uses
continuous voltage scanning that reduces measurement time by 80 %, allowing the charge
distributions of shorter-lived aerosol to be measured with 45-second scans.
Another aim is to investigate the charge distribution for non-neutralised aerosols, potentially
cutting electrostatic classifier costs and increasing usability in broader contexts. We find that non-
neutralised aerosol generated by a Collison and an Atomiser are similar across all salts and
solutions tested, which means size distributions may be measured without a neutraliser.
The final aim is to test the current theory of droplet collision dynamics against data for droplets
ten times smaller than previously measured. We find that the current theories fit the data well.