Article ID Journal Published Year Pages File Type
1888418 Radiation Measurements 2013 18 Pages PDF
Abstract

Long-term continuous in-situ radon field monitoring was carried out in the southern region of Israel, at the Amram Mountain research tunnel in Elat and in shallow boreholes in the Gevanim valley in Makhtesh Ramon.This work shows that long-term radon monitoring based on simultaneous alpha and gamma measurement enables to differentiate between the impact of ambient temperature and pressure on radon transportation within porous media both in sites isolated from outer meteorological influence as in the Amram tunnel and in sites open to the influence of environmental conditions as in the Gevanim boreholes array.It was found that if the monitoring site is a closed measuring space with undisturbed environmental conditions, the radon in the air space will reach equilibrium with the radon in the rock. Then the radon time series as measured by both gamma and alpha detectors exhibit the same temporal variations. The results in this case indicate that the diurnal, intra-seasonal and seasonal variations in the radon concentration are clearly associated with the ambient temperature gradient outside the rock air interface, 100 m above the tunnel.In shallow, open boreholes, no equilibrium between the radon within the porous media and the radon in the open borehole air is necessarily established and the results of radon monitoring are different. Gamma detectors that measure the changes in radon concentrations in the porous rock indicated a clear correlation between radon concentrations and the daily variations of external surface temperature, from about 1 m up to 85 m.Yet the alpha detectors that measure the changes in radon concentrations in very shallow borehole air (about 1 m) reveal a clear anti-correlation with atmospheric pressure waves at semi-daily, daily, and intra-seasonal time scales. At depths of several tens of meters, outer pressure waves induce anti-correlated radon variations lasting the same time, but destroy the ordered radon daily periodicity in the measuring air space, although almost not disturbing the daily radon variation within the surrounding porous media.

► The impact of ambient temperature and pressure on subsurface Rn-222 is presented. ► The research was done in open boreholes and close tunnel in the Israeli south desert. ► Rn-222 was measured concurrent by alpha in subsurface air and gamma from solid media. ► It was found that Rn move in air of open boreholes or tunnels, is driven by pressure. ► Rn move in porous media down to 100 m is driven by the surface temperature gradient.

Related Topics
Physical Sciences and Engineering Physics and Astronomy Radiation
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