THE EFFECT OF BUBBLE-MEDIATED GAS TRANSFER ON PURPOSEFUL DUAL-GASEOUSTRACER EXPERIMENTS

For air-water gas exchange across unbroken surfaces, the only gas-depe ndent parameter affecting the transfer velocity is the molecular diffu sivity of the transferring species. in contrast, bubble-mediated trans fer processes can cause the transfer velocity to depend on both molecu lar diffusivity and aqueous-phase solubility. This can complicate the analysis of data from dual gaseous tracer gas transfer experiments. Bu bble effects also complicate the estimation of transfer velocities for other gases from the transfer velocity calculated using the dual-trac er data. Herein a method for incorporating the effects of bubble-media ted gas transfer processes on the transfer velocity is presented. This new procedure is used to analyze the data from two recent dual-tracer gas transfer experiments. Transfer velocities that include the effect of bubbles are calculated using the data from two previous oceanic du al-gaseous tracer experiments. Comparing these transfer velocities wit h transfer velocities calculated by neglecting the effect of bubbles s hows that bubble-mediated transfer increased the transfer velocity of helium 3 by 5% at a wind speed of 10.6 m s(-1). However, when using th e transfer velocities for helium 3 to calculate transfer velocities fo r carbon dioxide under the same conditions, including the effect of bu bbles decreases the transfer velocity of carbon dioxide by 18%. This s hows that bubble-mediated transfer does not have a large effect on the analysis of dual-tracer data, but it is important in relating transfe r velocities determined using helium 3 and sulfur hexafluoride to tran sfer velocities of more soluble gases at wind speeds above 10 m s(-1).