UC San Diego

Aerosols are solid or liquid particles suspended in the air that can have far-reaching impacts on climate and human health. Aerosols impact climate through their radiative properties and their ability to seed cloud droplets or ice crystals. They also provide surfaces at which heterogeneous multiphase reactions can occur and serve as sinks for atmospheric sulfur, carbon and nitrogen. From a human health perspective, the physical and chemical properties of aerosols including their size, shape, and composition, can impact their transfer and deposition into the lungs. Smaller particles in particular can contain pollutants and pathogens and are able to travel deeper into the bronchioles to trigger irritation and infection. This body of work applies molecular dynamics simulations to understand aerosol systems, investigating their morphologies, impacts on climate, and ultimately their role in transporting the airborne SARS-CoV-2 virus. Molecular simulation and analysis methods are integrated with experiment to first probe surfactant interfaces with varying levels of chemical complexity, then to explore whole aerosol dynamics and phase within the context of understanding impacts of sea spray aerosols (SSA) on climate. This work shows that 1) surfactant charge modulates the surface activity of Burkholderia cepacia lipase at lipid monolayer interfaces; 2) calcium enhances polysaccharide adsorption to fatty acid monolayers; and 3) divalent cations induce morphological changes in LPS-containing aerosols, hindering the reactive uptake of atmospheric nitric acid. This dissertation also describes methods for building large-scale, intact SSA models with full chemical complexity and shows how organic components distribute throughout the aerosol, suggesting that SSA may adopt microemulsion-like morphologies. Finally, a workflow is developed to build ultra-large systems for the study of airborne disease, demonstrating the successful construction and simulation of 1) the SARS-CoV-2 wild type envelope, and 2) a billion-atom respiratory aerosol containing the full breadth of chemical complexity, including the first all-atom model of the Delta SARS-CoV-2 envelope and never-before-modeled pulmonary mucins. The latter project presents the first atomic-level views of the SARS-CoV-2 virus within a respiratory aerosol and represents a novel approach to investigating the infection mechanisms of airborne pathogens.