This research will define the basic mechanisms by which surfactants in marine waters affect the rate of gas exchange at the air-sea interface. Surfactants reduce gas exchange by altering the hydrodynamic structure of near-surface turbulence, and not by the formation of a monomolecular barrier. Reductions in gas exchange up to 50% have been observed in a variety of samples from synthetic surfactants to phytoplankton exudates and this reduction occurs under turbulent flow conditions. This research is aimed at a two step examination of the chemical and surface properties of surfactants as they relate to gas exchange processes. First, an experimental model relating the gas exchange coefficient Kw to the surface dilational modulus , the Schmidt number Sc and the friction velocity U*w, will be explored in a laboratory wind-wave tank. Second, the surface and organic chemistry of marine phytoplankton exudates will be described in relationship to their retarding effect on gas exchange. The overall results should improve our understanding of how surfactants of biogenic origin influence physical processes such as gas exchange in the ocean.
