GAS TRANSFER VELOCITIES FOR SF6 AND HE-3 IN A SMALL POND AT LOW WIND SPEEDS

Gas transfer velocities for two gases, SF6 (sulfur hexafluoride) and He-3, 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 He-3, we calculated the Schmidt number exponent to be 0.57+/-0.07.