summer radon

["Deborah P. Steva" <dps3c@kelvin.seas.virginia.edu>]

Dear Radsafe:

Radon concentrations(and daughter concentrtions) in OUTDOOR air
fluctuate hourly, dialy etc. but most noticably from winter to
summer.  What factor (s) are primarily responsible for the 
more significant seasonal fluctuations? From limited search of
literature - my first guess would be pressure differentials
(produced by temperature differences between soil and air)
pulling soil gas out of soil more in summer than winter?

Thanks

D. Steva