Rn gas is heavier than air, that is why people tend to monitor its level in the basement of their houses. Is it possible for Rn to leak upwards through the soil components?
I think you should rather say radon gas is denser than air . . . as to why it leaks upwards it is (a) not as dense as soil or water and (b) the process is probably more diffusion related, which will move gas molecules in any direction.
I think you should rather say radon gas is denser than air . . . as to why it leaks upwards it is (a) not as dense as soil or water and (b) the process is probably more diffusion related, which will move gas molecules in any direction.
Radon propagates by diffusion not only in soil but also in atmosphere.
Dear Dr. Dawood,
you are right as far as the gaseous element Rn is concerned. In nature Rn is not viewed under laboratory conditions but mostly in a fluid-gas regime. This regime is controlled by the porosity-permeability conditions of the host, be it a lithological unit at depth or the topsoil. Some sketches may display to you the migration and trapping of Rn in the subcrop and at outcrop and help you come to grips with this system.
Good Luck !
H.G.Dill
Rn atom settling velocity in air is very slow due to Brownian motion. Formulas are in every aerosol science textbook. The molecules in air at room temperatures move 100-500 m/s, hit each other ~10^9/s. That's why diffusion is so slow. Yet the lighter elements like H2 and He escape from earth atmosphere more readily than air, and than Rn certainly also. It is because being lighter they move faster, and are more likely, in the upper atmosphere, upon reaching the escape velocity over 10 km/h, to escape. And it is much less likely for Rn, so in this sense it stays at the bottom.
Advection is another mechanism, which carries Rn by earth gas, driven by pressure difference, and possibly some other mechanism, not understood yet. The advection is usually much faster than diffusion, which means that diffusion transport becomes negligible compared to advection.
At the equilibrium according to Boltzman‘s distribution, concentration of all atmospheric gases almost constant for 10-15 meters of high. You can find my calculation on this matter of common misconception in the paper
http://www.sid.ir/En/VEWSSID/J_pdf/92620080101.pdf
correction: the escape velocity is over 10 km/s, not km/hr. Sorry.
- Badges
- Science topic
- Similar topics
- Engineering
- Petroleum Engineering
- Gas