Organic coatings, such as fatty acid surfactants, on sea spray aerosol (SSA) can determine the lifetime, reactivity, and properties such as light scattering and ice nucleation of the aerosol in the atmosphere. Moreover, the protonation state of the surfactant can affect those properties. Studies have revealed that there is a difference between the surface and bulk pKa values for medium-and long-chain fatty acids. However, the effects of fatty acid concentration and salts on the surface pKa are not well understood. Although the bulk pKa changes little with acid concentration, surface pKa values are do depend on concentration due to the unique environment of the interface that can concentrate the fatty acid and can increase the intermolecular interaction. It is interesting to find that surface pKa decreases with decreasing concentration of the fatty acid. Furthermore, the change in surface pKa of various fatty acids at different concentrations of salt solutions has not been probed. These experiments with the addition of salts can mimic marine-relevant conditions. Overall, this study provides insights into the properties of sea spray aerosol while predicting its compositional and structural change due its environment.

Impact of concentration and the presence of salt on the surface pKa of fatty acids at the air-water interface

2019 Fall National Meeting

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