Gas transfer velocities for SF₆ and ³He in a small pond at low wind speeds

Gas transfer velocities for two gases, SF₆ (sulfur hexafluoride) and ³He, were determined in a small pond by injecting a mixture of these gases into the water and monitoring the decline of their concentrations over the next eight days. For wind speeds between 1.5–2.5 m s⁻¹, no variations of gas transfer velocity with wind speed could be resolved with our data. Gas transfer velocities at wind speeds greater than 3 m s⁻¹ were substantially larger and consistent with other lake tracer experiments. From the ratio of gas transfer velocities for SF₆ and ³He we calculated the Schmidt number exponent to be 0.57±0.07.