Dependence of the Transfer Velocity of Carbon Dioxide on the Salt and Surfactant Concentrations in Waterbodies

The exchange of gases, such as carbon dioxide (CO₂) and oxygen, across the air-water interface is essential to supporting biogeochemical processes that occur in water bodies. In this experimental study, we investigate the dependence of the flux of CO₂ on the salt and surfactant concentrations of the water body. The results are described using the stagnant film model in which the gas flux is defined in terms of the transfer velocity and the difference in the gas concentration between the atmosphere and the water body. The model assumes that away from the interface, the water and air are well mixed, and the transport within the film occurs by diffusion. The thickness of the stagnant film depends on the state of mixing in the water body. The state of mixing in our experiments is varied by changing the speed of a magnetic stirrer. The dependence of the transfer velocity on the salt and surfactant concentrations is investigated.