Files
Abstract
Natural marine surfactants produced by microorganisms affect interfacial properties which directly influences the production and fate of sea spray aerosol in the atmosphere. These surfactants alter the surface tension at the ocean-air interface which influences aerosol production and gas exchange rates. Once emitted in sea spray aerosol particles, surfactants also influence particle interfacial tension which can affect particle growth rate and ability to form cloud droplets. While previous studies have investigated these environmental effects and made broad quantifications of marine surfactants, there has previously been little work to identify natural surfactants found in marine water and aerosol particle samples. The research performed for this dissertation focused on optimizing methods for the extraction and analyzing characterization of marine surfactants using solid phase extraction (SPE) and high-resolution mass spectrometry. A unique SPE method was developed using two SPE cartridges (C18 and graphitized carbon) of different sorbent materials to extract anionic, cationic, and nonionic surfactants at extraction efficiencies of 85%, 75%, and 60%, respectively. This SPE method greatly improved the extraction efficiency of cationic surfactants which may have been underrepresented in previous research. These methods were then applied to collected ambient estuarine water and aerosol samples to isolate, identify, and characterize the various classes of environmental surfactants found in the Skidaway Island estuary and Delaware Bay. Organic molecules identified in the estuarine water mass spectra grouped largely into low oxygen-to-carbon and high hydrogen-to-carbon which are characteristic molecular features of surfactants. Fatty acid surfactants, such as oleic acid, were identified in Delaware Bay water samples from marine influenced regions and non-surfactant organic molecules like sucrose were identified in regions more strongly influenced by terrestrial sources. In extracted ambient aerosol samples collected on Skidaway Island, GA, fatty acids were identified with differing chain lengths depending on wind direction and the resulting air masses at the sampling site. Altogether these studies allowed for the development and application of new analytical methods to efficiently extract surfactants from both marine water and aerosol particle samples and furthered the previously limited analysis of environmental surfactants through chemical characterization with mass spectrometry.