sulfur hexafluroide as a greenhouse gas and its atmospheric journey
Carbon dioxide is heavier than air but is found in nearly equal proportions throughout the well-mixed portion of the atmosphere. Xenon is much heavier than air, almost as heavy as sulfur hexaflouride, but it too is found in nearly equal proportions throughout the well-mixed portion of the atmosphere.
Turbulence is what makes the well-mixed portion of the atmosphere be well-mixed. It is only in the uppermost layers of the atmosphere, where the air is very thin, that turbulence fails to keep things well-mixed. The turbopause, which marks the border between the well-mixed lower portions of the atmosphere and heterogenous upper portions of the atmosphere, is about 100 km above the surface. The stratosphere is only 10 to 50 km above the surface, so it is well within the well-mixed portion of the atmosphere.