Models for air-water gas transfer: an experimental investigation

The air-water transfer velocities for H₂, He and Xe have been measured simultaneously in laboratory-tank experiments. Using average values from the existing literature data for the molecular diffusivities of the gases, the transfer velocities are found to vary with the diffusivity raised to the power 0.57. This exponent is in reasonable agreement with the findings from other laboratories, as well as field studies, provided average diffusivities are used consistently. Although interpretation is limited by uncertainties in presently available diffusion coefficients, the results may be interpreted as supportive of both the surface-renewal and boundary-layer models of air-water gas exchange, but they provide little evidence for the appropriateness of the film model.