Abstract View
Accurate Representations of the Microphysical Processes of Aerosols and Droplets from Exhalation Events and the Impact on the Sedimentation Distance
JIM WALKER, Justice Archer, Florence Gregson, Bryan R. Bzdek, Jonathan P. Reid, University of Bristol
Abstract Number: 238
Working Group: The Role of Aerosol Science in the Understanding of the Spread and Control of COVID-19 and Other Infectious Diseases
Abstract
The role of droplets and aerosols in the spread of respiratory viruses such as SARS-CoV-2 is well established, contaminating surfaces and sometimes leading even to an opportunistic airborne mode of transmission. Large droplets and small respiable aerosol particles span a continuum in size from 100s nanometres to 100s of micrometres, and are generated from coughs, sneezes, speaking and even breathing. On expiration, a competition between evaporation, sedimentation and forward momentum, governs the sedimentation of large droplets, while small aerosol particles remain airborne for many hours. We will report measurements of the hygroscopic response of surrogate respiratory fluids, including an examination of kinetically impaired moisture loss, crystallization, and the temperature dependence of evaporation rates. With these improved models of the aerosol microphysics, we then examine the impact on sedimentation distances using a model that captures the transport of the aerosol and droplets, including air buoyancy, and evaporative mass and heat transfer. We will report on the differences observed when accurately representing the kinetics of moisture content of the aerosols and droplets composed of respiatory fluids rather than their often used treatment as aqueous sodium chloride or water droplets. The impact of phase behaviour on drying kinetics will be reviewed along with the dramatic sensitivities to environmental relative humidity and temperature. Consequences for physical distancing guidelines will be considered.