Saturated fatty acids comprise one of the most abundant and surface-active components of sea spray aerosol (SSA) during seasons of high biological productivity in the ocean. An organic film is formed on SSA surfaces, and particle aging in the marine boundary layer leads to changes in film morphology. Surface pressure – area isotherms and Brewster angle microscopy were used to investigate interfacial organization and morphology as a function of SSA aging. A fatty acid mixture composed of myristic acid (MA), palmitic acid (PA), and stearic acid (SA) at the molar ratio of 3 SA:4 PA:2 MA was used to model the dominant surfactant composition in fine SSA. An aqueous subphase of 0.4 M NaCl adjusted to pH 8.2, 5.6, and 2.0 was used to mimic the SSA aqueous core at various stages of particle aging. We show that the SSA proxy film differs in phase behavior and monolayer collapse from that of its individual fatty acid components. The proxy film exhibits intermediate rigidity at seawater pH and folds upon film compression, whereas at low pH the film becomes highly rigid and forms 3D nuclei upon monolayer collapse. Our results indicate that subphase composition and pH play a significant role in modulating SSA film morphology, which in turn impacts SSA reflectivity in the atmosphere.

Atmospheric aging increases rigidity in sea spray aerosol proxy films

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.