UC San Diego

Atmospheric aerosols directly impact the Earth's climate by scattering and absorbing solar radiation and indirectly by altering the microphysical properties of clouds. Aerosols formed over the oceans, termed marine aerosols, consist of secondary marine aerosols (SMA) formed upon the oxidation of gas phase species and of primary sea spray aerosols (SSA) that are directly emitted from the surface of the ocean. The climate relevant properties of primary SSA are determined by their size and chemical composition, both of which are functions of the ocean's biological activity as well as atmospheric heterogeneous reactions with trace gas species and photochemical aging reactions. This dissertation investigates the impacts of each of these processes on the chemical complexity of SSA by conducting fundamental laboratory studies involving spectroscopic probing of various SSA systems ranging from simple, single component model systems to authentic SSA produced using an indoor ocean-atmosphere facility that replicates the chemical and biological complexity of the ocean and SSA. First, we identified the various chemical species found in SSA and linked their size and temporal changes to the biological activity of the ocean. Next, we used our improved understanding of the molecular speciation of SSA to look in-depth at the atmospheric reactions that alter the chemical and physical properties of SSA, including the heterogeneous reaction with gas phase nitric acid and OH radicals, as well as photosensitized reactions with chromophoric species. We found that the chemical complexity of SSA due to the organic and biological components alters their reactivity and introduces alternative pathways beyond those previously acknowledged. Finally, to aid in future experiments of photochemical aging reactions of SSA, we constructed and validated an LED incoherent broadband cavity enhanced absorption spectrometer (LED-IBCEAS) to detect various nitrogen oxides (e.g., NO2 and HONO). The findings presented in this dissertation improve our understanding of the various chemical and biological controls on the climate relevant properties of SSA, and can ultimately be used to improve the performance of regional and global climate models.