Atmospheric and deep seated sources of unsupported lead-210 in soil profiles and the use of lead-210 and polonium-210 as indicators of uranium mineralization at depth
Ageli, Hadi S.
Adams, John A. S.
Master of Arts
The increase of supported lead-21/polonium-21 with depth in soil profiles over buried uranium ore has been found to be a very cost effective method of uranium prospecting. Lead-21/polonium-21 soil profiles of the uppermost meter are superior to radon-222 track etch cups because the flux of radon-222 is highly variable from time to time depending on many factors, such as changes in wind velocity, pressure, and temperature. On the other hand, lead-21 has a half-life of 22.3 years and it is a time-integrated measurement of radon-222; the method integrates over six half-lives of lead-21 (about 133 years). At Felder Mine, Texas, the lead-21/polonium-21 soil profile increases with depth across a fault zone since the faulting facilitates the upward migration of radon-222. Reversed profiles have been observed where radon-222 accumulates under a semi-impermeable caliche layer. Also at Felder, polonium-21 from the radon-222 mobilized and released to the atmosphere during strip mining operations was detected where the soil had been removed.