UC San Diego

Aerosols influence global climate directly by scattering and absorbing incoming solar radiation and indirectly by initiating cloud droplet and ice crystal formation; both particle size and chemical composition play a role in these impacts. Particle size and composition constantly evolve due to atmospheric processing. The physicochemical properties of marine aerosols, including sea spray and anthropogenic emissions, are of particular interest since oceans cover over 70% of the Earth's surface. This dissertation aims to probe the role of oceanic biological activity, anthropogenic emissions, and subsequent atmospheric processing on marine particle chemistry by measuring the size-resolved chemistry of individual ambient marine aerosols and laboratory-generated particles using aerosol time-of-flight mass spectrometry (ATOFMS). The impact of biological activity on the mixing-state of sea spray particles was examined by adding biologically- derived organic material and/or phytoplankton cells to seawater then generating particles through bubble bursting. Unique particles characterized by organics, Mg²⁺ and/or Ca²⁺ were detected during these experiments as well as in the ambient atmosphere during periods of elevated biological activity. Additionally, elemental sulfur ions were also detected in ambient marine particles in regions of elevated biological activity at night. These particles were successfully reproduced from bubble bursting experiments suggesting that these particles are directly ejected from the ocean. In addition to sea spray aerosol, the particle chemistry of marine aerosols from anthropogenic sources was also examined during shipboard measurements made during CalNex along the California coast. Soot was dominant in Southern California while organics characterized the particle chemistry in the Sacramento area highlighting regional differences in anthropogenic emissions in California. Further, measurements made at the Port of Los Angeles and those made on the Scripps Pier showed a decline in emissions from ships combusting residual fuel compared to earlier measurements; these results are in compliance with recent regulations requiring ships to combust low sulfur fuel when approaching the California coast. Finally, during the Study of Organic Aerosols in Riverside, CA (SOAR), the dimethyl sulfide (DMS) oxidation product methanesulfonic acid (MSA) was detected in anthropogenic particle types, and was elevated in vanadium-containing emissions characteristic of residual fuel combustion suggesting that anthropogenic particles can enhance the atmospheric processing of marine biogenic emissions