Richard E. Cochran, Thilina Jayarathne, Elizabeth A. Stone, Vicki H. Grassian

Although theories have been developed that describe surface activity of organic molecules at the air-water interface, few if any studies have tested how surface activity impacts the selective transfer of molecules from solution phase into the aerosol phase during bubble bursting. The selective transfer of a series of organic compounds that differ in their solubility and surface activity across the water-air interface into the aerosol phase is quantified experimentally for the first time. Aerosols produced from solutions containing salts and a series of linear carboxlyates (LCs) and dicarboxylates (LDCs) were generated using a bubble bursting process. Surface activity of these molecules dominated the transport across the in-terface with enrichment factors of the more surface active C4-C8 LCs (55±8) being greater than C4-C8 LDCs (5±1). Trends in the estimated surface concentrations of LCs at the liquid-air interface agreed well with their relative concentrations in the aerosol phase. Along with LCs, calcium was selectively enriched with respect to other inorganic cations including sodium, potassium and magnesium, suggesting the selective interaction of carboxylates with calcium. Chloride and sulfate depletion was observed in aerosol size ranges where linear carboxylate enrichment was greatest.