UC San Diego

Aerosols influence climate by directly scatter radiation and affecting cloud properties and lifetime. Biological aerosols (bioaerosols) act as cloud condensation nuclei and ice nucleating particles (INPs) and can impact human and ecosystem health. Oceans, which cover over 70% of the Earth’s surface, comprise an important source of bioaerosols emitted in both primary sea spray aerosol (SSA) particles and formed as secondary organic aerosols (SOA) from biogenic volatile organic compounds (VOCs). However, the influence of marine bioaerosols on clouds and climate remains an area of high uncertainty. In this dissertation, bioaerosols from marine environments were measured in laboratory-based systems and the ambient coastal environment to analyze their impact on cloud formation and on local communities. Studies on the ice nucleating ability of SSA showed supermicron-size SSA particles, rather than submicron, were the predominant source of INPs released from a marine environment. The size of these particles suggests these INPs represented bioaerosols, like marine bacteria, their fragments, or exudates. Bioaerosol emissions in SSA were measured with single-particle fluorescence spectrometry over the course of a mesocosm phytoplankton bloom and showed, for the first time, the fluorescence signature and size distribution of these particles in nascent SSA. To uncover how atmospheric oxidants impact the SSA fluorescence profile, an oxidative flow reactor was used to simulate days of atmospheric aging during a phytoplankton bloom study in an ocean-atmosphere system. This study revealed that aged SSA particles underwent chemical transformations from proteinaceous to humic-like particles, reflected in the loss of protein-like fluorescence and the production of humic-like fluorescence. Applying these online fluorescence methods to aerosols in an urban-coastal environment demonstrated the ability to distinguish and characterize marine and continental air masses. Lastly, we developed a novel system combining a sublimation-condensation flow tube with a matrix-assisted laser desorption ionization matrix and an aerosol time-of-flight mass spectrometer to identify sub-100 nm SOA produced from biogenic VOCs. By improving bioaerosol detection in marine environments and better understanding their ability to seed clouds, the findings from this work enable more accurate representations and parameterizations of marine emissions for global climate models.