Atmospheric pressure effects on²²²Rn transport across the Earth-air interface

Abstract

The effect of large-scale atmospheric pressure changes on the 222Rn flux across the soil-air interface is investigated. Field data collected during 1972 and 1973 show that pressure changes of 1–2% associated with the passage of frontal systems produce changes in the 222Rn flux from 20 to 60%, depending upon the rate of change of pressure and its duration. A simple model of molecular diffusion combined with pressure-induced transport in the soil has been confirmed by laboratory experiments using a vertical column of 226Ra-bearing sand. On the basis of this model, pressure changes of 10–20 mbar occurring over a period of 1–2 days produce Darcy velocities of the order of 10−4 cm s−1 near the surface of a soil having a permeability of 10−8 cm2. The corresponding variations in the 222Rn flux predicted by the model are in agreement with those observed from valley alluvium in central New Mexico.