Application of Langmuir Monolayers in the Investigation of Surface Properties of Sea Spray Aerosols

Aqueous aerosols coated by surface-active organics, such as sea spray aerosol (SSA) , commonly possess inverse micelle structure with an aqueous core coated by a hydrophobic organic monolayer. The surface organization and chemical composition of organic films of SSAs have important influence on their physical, chemical and optical properties. Langmuir monolayers are monomolecular layers formed by the diffusion of longchain surface-active organics with low volatility, such as fatty acids, fatty alcohols and phospholipids at the airwater interface. With Langmuir trough, the changes in surface pressure (pi) along with decreasing molecular area (A) of single and mixed component monolayers at the air-water interface can be obtained. In addition, pi-A isotherms provide information about the interfacial behavior of corresponding monolayers above an aqueous surface. Understanding the interfacial properties of monolayers will enable the prediction of the fate and behaviors of surfactants in the real-world SSA. This paper reviews the commonly used interfacial characterization techniques of atmospheric aerosols, established models for SSA based on Langmuir monolayer, and the implications of organic films on atmospheric behavior of SSA. Although the physical properties and morphological changes of SSA-related monolayers have been studied in depth, little attention has been paid to the interfacial changes induced by environmental factors such as reactive gases, irradiation and bioactive substances. These knowledge gaps shed light on future laboratory simulation and model research of SSA.