Influence of Dissolved Solutes and Surfactants on the Transfer Velocity of Carbon Dioxide Across the Air–Water Interface

The exchange of gases, such as carbon dioxide (CO₂), across the air-water interface is essential for supporting biogeochemical processes in water bodies. In this experimental study, we investigate how CO₂ flux depends on the concentrations of salt and surfactant in the water body. A stagnant film model is used to calculate the gas flux in terms of the transfer velocity. The dependence of the transfer velocity on the salt and surfactant concentrations is investigated. The model assumes that away from the interface, the water and air are well-mixed, and that the transport across a stagnant film is by diffusion. The thickness of the stagnant film depends on the state of mixing on both the air and water sides. The state of mixing of water in our experiments is varied by changing the speed of the magnetic stirrer and by a fan installed on the air side.