Re: Naturally Occuring Radon Isotopes

[nta@ix.netcom.com (Robert Holloway)]

 The activity ratio of U-238 and Th-232 in the earth's crust is
about 1, on the average.  So the activity ratio of of Radon-222
to Rn-220 should also be roughly 1 near the earth's surface but 
increase with altitude due to the shorter half-life of Rn-220.

In 1963, Junge gave a similar estimate of the activity
ratio of Rn-222 to Rn-220 in air near the ground.  He suggested that 
the Rn-222 activity is not quite half of the Rn-220 activity.  With 
altitude, away from the supporting sources, the activity of Rn-222
becomes much greater than Rn-220. Local variations in the 
concentrations of uranium and thorium could also have an 
effect as has been mentioned previously. 


                               Robert Holloway
                               Nevada Technical Associates
                               http://www.ntanet.net/
                               email nta@Ix.netcom.com


You wrote: 
>
>Does anyone have figures for the natural ratio of atmospheric 
Radon-222 to Rn-
>220?  Thanks.
>
>bill
>bkolb@arinc.com
>
>
>