RADON FLUXES FROM SOILS TO THE ATMOSPHERE MEASURED BY PB-210-RA-226 DISEQUILIBRIUM IN SOILS

Measurements of the activities of the parent (226Ra) and progeny (210Pb) of 222Rn in 119 core samples of North American soils reveal that the mean fraction of the 222Rn produced in the upper 50 cm that escapes to the atmosphere equals or exceeds 25%. The flux derived from the upper 50 cm is 0.48 atoms cm−2 s−1. Measurement of 210Pb–226Ra disequilibrium at greater depths in 12 cores indicates a mean depth of 222Rn escape of ∼218 cm, slightly greater than commonly reported values of ∼175 cm. Using these mean depths to extrapolate the flux measurements from the upper 50 cm yields a total radon flux of from 1.9 to 2.3 atoms cm−2 s−1. Copyright 1990 by the American Geophysical Union.