Sea Spray Aerosol Chemistry Clarified

Airborne particles called aerosols play an important role in climate by seeding clouds and reflecting or absorbing sunlight, depending on their composition. Aerosols created by breaking waves have been particularly difficult to study under controlled conditions. Andrew P. Ault, now at the University of Michigan, Ann Arbor, presented work done with Vicki H. Grassian at the University of Iowa on such particles created using a laboratory wave channel developed by Timothy H. Bertram and Kimberly A. Prather at the University of California, San Diego. Studying aerosols created from seawater pumped in from the ocean, Ault and colleagues looked at particles composed of inorganic salts and organic material (Environ. Sci. Technol. 2013, DOI: 10.1021/es400416g). They found that when the particles react with nitric acid, as they would in the atmosphere, nitrate replaces chloride and the distribution of other particle components changes. Magnesium and calcium move from the surface to the interior of the aerosol particles, and a denser organic layer forms on the surface. Such changes would modify how the particles affect atmospheric chemistry and climate. For example, composition changes could alter how aerosols absorb water and seed clouds, although the exact details remain to be determined, Grassian said.