Enrichment of saccharides in sea spray aerosol

Ocean wave breaking produces tiny particles suspended in the air, called sea spray aerosol (SSA). Since oceans cover more than 70% of the earth’s surface, SSA represents one of the largest natural aerosol sources. SSA affects global climate through processes by influencing cloud and ice formation, although the extent of their impact on climate remains an active area of research. To understand the climate-relevant properties of aerosols requires understanding of its chemical and physical properties. The focus of this thesis is to characterize the chemical composition of SSA and the chemical and biological factors that influence it through controlled laboratory experiments with varying degrees of chemical complexity. Among organic matter transferred to SSA are saccharides (a.k.a. carbohydrates, or sugars), which comprise a significant portion of SSA mass and are among the most enriched molecules. Model systems revealed that small saccharides consisting of 1 – 6 connected units were not enriched, whereas a polysaccharide consisting of >1,600 connected units enriched in aerosol up to 1.7 times, indicating that polysaccharides more likely to interact with the air-water interface are enriched more than small saccharides. The enrichment of the polysaccharide was increased up to 2.5 and 5.8 times after addition of calcium and protein, respectively, indicating the importance of interactions with other chemicals on the enrichment of saccharides. During a phytoplankton bloom occurring in natural seawater in the laboratory, saccharide enrichments increased up to 38 – 930,000 times indicating the importance of marine microbes on the enrichment of saccharides. Further, heterotrophic bacteria increased the enrichment of glucose-containing saccharides that they preferentially modify while using as a food source; whereas the enrichments of other saccharides, such as xylose, remained consistent likely because they are not a preferential food source and are modified more slowly. These studies expand the knowledge of how and to what extent saccharides enrich in SSA. This thesis demonstrates that after SSA is emitted, heterogeneous oxidation alters its composition by increasing organic carbon mass, particularly in particles less than 250 nm in diameter. Additionally, this thesis advances understanding of the organic volume fraction of SSA and progress toward size separating organic matter that nucleates ice in seawater. This knowledge provides insight into chemical changes in SSA that can impact the Earth’s climate.