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INTRODUCTION
To our knowledge the first measurements of vertical distribution of radon
in the troposphere were made in 1950 (1).
The samples taken in Ohio showed a
decrease in activity with altitude while the measurements made in California
over the ocean showed an increase with altitude.
The theoretical interpretation
of these results indicated that in the second case the air originated in Asia
and that the horizontal wind speed was greater at higher levels than near the
This explained the inverted concentration profile.
surface.
Between 1956 and
1958 several series of measurements were made in the USSR by Kirichenko (2) who
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used the profiles obtained in certain cases to deduce the variation of the
diffusion coefficient with altitude.
In the United States Wilkening in 1952 (3)
carried out several measurements above New Mexico, more recently this author has
used radon to study the levels above the mountains (4).
A theoretical study of
the vertical distribution of radon in the troposphere has been made by Jaconi (5)
and more recently by Bouville and Machta (6) who considered the time variations
of the diffusion profile.
A knowledge of the vertical distribution of radioactivity in the tropcsphere
is interesting for several reasons:
1.
The natural radioactivity contributes to atmospheric ionization and
therefore is of interest in atmospheric electricity.
2.
Radon is the parent of long lived radionuclides (lead-210 and polonium-
210) which are used as tracers for atmospheric physics (large scale air mass
movements, washout, etc.).
To interpret the variation in these nuclides and
to study their diffusion it is necessary to know their source, that is the
distribution of radon in the atmosphere.
3.
Radon is an interesting tracer, in particular for the study of
diffusion.
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