UC San Diego

Aerosols impact climate directly by scattering and absorbing solar radiation or indirectly by influencing cloud properties and lifetime. Additionally, aerosols represent one of the most abundant surfaces available for heterogeneous reactions. Further, as aerosols react and age in the atmosphere, their interaction with solar radiation and water uptake can change. Sea spray aerosols (SSA) constitute one of the most abundant natural aerosols in the atmosphere. Understanding how oceanic biological processes affect SSA composition and heterogeneous chemistry remains an active area of research. To study SSA heterogeneous reaction processes, fundamental laboratory studies must be able to reproduce the full chemical complexity of SSA. In this dissertation, we discuss a novel approach to studying SSA chemistry in the laboratory. This approach entails inducing phytoplankton blooms in a laboratory microcosm experiment to study the impacts of natural microbial processes on the chemical composition of seawater and SSA. From these studies, the role of heterotrophic bacteria and their associated enzymes on the chemical composition of SSA are revealed. This dissertation investigates the impact of enzymes, active in both the seawater as well as in SSA, on aerosol physicochemical properties, including nitric acid heterogeneous reactivity that is important for global nitrogen cycle. Not only can enzymes affect the physicochemical properties of SSA, but they can transform the chemistry of the atmosphere upon coagulation with pre-existing ambient particles. Further, we discovered the roles of monovalent versus divalent cations in the morphology and heterogeneous reactivity lipopolysaccharide-containing SSA. The results uncover the bacterial produced chemicals, including hydrolytic enzymes and lipopolysaccharides, in controlling SSA composition and heterogeneous reactivity in the atmosphere.