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John E. Pearson and Harry Moses


Studies of concentrations of radon-222 in the atmosphere have been made from the surface of the earth to 16 meters elevation for eight periods of approximately 24 hours each. These studies provide over 650 individual determinations of radon concentration measured during a wide variety of meteorological conditions, from clear days with high radiation and relatively weak winds to cloudy days of low radiation and relatively high winds. Information presented indicates general features of radon concentration: 1) highest concentrations near the soil, the source, 2) maximum concentrations at night with the maximum near the soil occurring about 3 hours before the maximum at 16 meters, 3) minimum values at all levels near midday, 4) almost constant concentration with elevation, indicating good mixing during morning hours, and 5) the increase of concentration at ground level ahead of those aloft with the approach of evening.

Average 24-hour exposure at human breathing level, between 1 and 4 meters, varies between 0.259 and 0.301 picocuries per liter at the Argonne National Laboratory site.

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John E. Pearson, Donald H. Rimbey, and Gary E. Jones


The transfer of various gases through the soil-atmosphere interface is of interest to agronomists, meteorologists, biologists and many others. Such gases include carbon dioxide, water vapor and radon. A system applicable to measurements of the emanation of gases has been developed and used to investigate the emanation of radon-222. The instrumentation was designed so that the variation of soil gas emanation with time, wind speed, soil moisture, soil type, and geographical location could be studied. The system has measured a net transport through the earth-atmosphere interface of 1.1±0.6 atoms of radon-222 per square centimeter per second (mean of 27 means, eight samples each, ± standard deviation of 27 means). For a set of eight samples collected on a given site, the coefficient of variation was 0.3 to 0.4. The analysis of a single sample provided the amount of radon-222 collected with an error of about 5 per cent.

The system is completely portable, including the power supply, and can be carried from a vehicle by two men. It was designed to minimize disturbance of the site at all times, providing air flow and pressure within the collecting apparatus comparable to those in nature during sampling. Sampling sites can be chosen as desired, and all equipment can be removed from the site when sampling is completed. During a sampling trip to the Rocky Mountains, the equipment was transported 3000 miles without any breakage. Throughout an experiment on the diurnal variation of radon emanation, two duplicate systems were operated 12 hours each without difficulty.

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