The ocean is a major source of atmospheric aerosol by mass and emits sea spray aerosol (SSA) by breaking waves at the ocean surface. Molecular composition of SSA can be impacted by physical conditions of aerosol generation such as wind speed. To test this hypothesis, SSA were collected at different wind speeds ranging from ~7 to ~15 m s^-1 using the Scripps Ocean-Atmosphere Research Simulator (SOARS) during the Characterizing Atmosphere–Ocean parameters of SOARS (CHAOS) campaign. Bulk and molecular analyses were applied to the collected SSA, with organic carbon analyzed by thermal-optical techniques, inorganic ions measured by high performance ion-exchange chromatography with conductivity detection, and trace elements analyzed by inductively coupled plasma mass spectrometry (ICP-MS). According to the preliminary findings it is observed that organic carbon and inorganic ion composition of SSA varies as a function of wind speed. Enrichment factors will be used to examine the extent to which these SSA components are enriched relative to seawater, and the dependence of this enrichment on windspeed. Future analyses will include measurement of organic species using liquid chromatography (LC) coupled to mass spectrometry (MS) by qualitative and quantitative methods. Functional group analysis will be used to examine organosulfates that fragment to the bisulfate anion (m/z 97, HSO₄^-) and sulfate ion radical (m/z 96, SO₄^.-), organonitrates that fragment to the nitrate anion (m/z 62, NO₃^-), and carboxylic acids that fragment to propenoate anion (m/z 71, C₃H₃O₂^-) or benzoate anion (m/z 121, C₇H₅O₂^-) and neutral loss of carbon dioxide (Δ44, CO₂). The targeted analysis of individual molecules in the positive mode will be conducted to identify alkyl amines. Identification of molecular formulas and evaluation of molecular structure will be carried out using an ultra-high resolution tandem MS. Findings of this study will support to explore how chemical changes upon different wind speeds influence the structure and properties of SSA.

Grant Deane

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