Chemical and Physical Properties of Surfactants in Seawater and Aerosol Particles and Their Influence on Particle Hygroscopic Growth

The size and composition of atmospheric aerosol particles modulate their interactions with solar radiation, and thus their influence on climate and visibility. The radiative effects of aerosol particles remain a large uncertainty in accurately modeling and predicting current and future climates. Recent work has demonstrated the presence of organic surfactant molecules in atmospheric aerosol particles, and their sources and transformations in the atmosphere are currently being studied. The role of the chemical and interfacial properties of surfactants and their overall influence on the hygroscopic growth of aerosol particles is still unknown. One major source of natural aerosol particles is sea spray emitted through wave-generated bubble bursting at the ocean surface. Sea spray aerosol particles are a significant fraction of particle mass and number in the atmosphere and contain a fraction of surfactant molecules. Surface-active organic compounds in the ocean are scavenged by rising bubbles and transported to the air-sea interface, referred to as the sea surface microlayer (SML). This layer is enriched in surfactant molecules, and current work is investigating the preferential enrichment of surfactants with specific properties. Here we show results from multiple studies in the Frossard Lab characterizing properties of surfactants in seawater, the SML, and atmospheric aerosol particles, as well as measurements of the influence of surfactants on the hygroscopic growth of model sea spray aerosol particles.