Lipid monolayers are known surfactants present at the air/sea water interface of the sea surface microlayer (SSML) and sea spray aerosol (SSA). However, little is known about the stability of these lipid monolayers at the air/water interface under different environmental conditions and in the presence of a chemically complex subphase that contains complex light absorbing species and/or biological components. In this research, we have investigated lipid monolayers and their stability at the air/sea water interface. Specific studies include: (1) the stability of palmitic acid (PA) monolayer on salt water interfaces in the presence of simulated solar light with and without a photosensitizer and; (2) the dynamics and impact of lipase embedded within negatively charged, neutral or zwitterionic lipids. By using surface sensitive techniques such as a Langmuir trough for relaxation curves and Infrared Reflectance Absorbance Spectroscopy (IRRAS), we have elucidated that PA monolayers in salt solutions become less stable in the presence of light and a photosensitizer. Upon interaction with lipase, negatively charged, neutral and zwitterionic lipid monolayers became disordered as demonstrated by IRRAS measurements and all-atom molecular dynamic simulations. Furthermore, lipase is shown to interact differently depending on the charge of the lipid monolayer; while lipase is squeezed out of the negatively charged lipid monolayers, it remains stable in the zwitterionic lipid monolayers even at high surface pressures and large lipase concentrations. Overall, these studies provide insights into environmental factors such as sunlight and the presence of chemically complex subphases on lipid monolayers at the air/sea water interface that can have important atmospheric implications such as changing SSA reactivity, hygroscopicity and aerosol lifetimes. Furthermore, these detailed measurements coupled with simulations provides insights on the interactions, structure and dynamics of these important interfaces present in the environment.

Stability of lipid monolayers at the air/sea water interface

2019 Fall National Meeting

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