TABLE 1
RADIOISOTOPES ABOVE 100, 000 FEET
Minimum
Isotope
Half-life
countable
Expected concentration (1961)
dpm
C-14
5670 years
0.5
Maximum
dpm /1000 SCF
500
(10 x background)
Minimum
dpm/1000 SCF
50
(background)
OCF needed for:
Maximum
Concen-
Minimum
Concen-
tration
tration
1
10
Remarks
CO, gas
or-90
28 years
i
500
10
2
100
Particulate
Cs-137
27 years
1
1000
20
1
50
Particulate
Pb-210
22 years
1
1
10°
Particulate
H-3
12 years
0.5
12 years
0.5
(as Ho)
H-3
(as Hy)
8
(105 T.U.)
6 x 104
0.01
103
0.08
60
(103 T.U.)
300
(2x 10° atoms/gm) (10° atoms/gm
6000
0,007
5
30
Na-22
2.6 years
Rh-102
1
210 days
1
S-35
87 days
Be-7
P-32
107}
-
Gas
(1.6 x 104 T.U.)
i074
104
1SCF = 6x105
to 3.x 1073 gm
15
Water Vapor
107
Particulate
1000
1
1
1000
Particulate
1
200
20
5
50
Particulate
53 days
10
2000
200
5
50
Particulate
14 days
1
20
2
50
500
Particulate
To obtain ambient volumes at:
105, 000 feet, multiply SCF by 100
160, 000 feet, multiply SCF by 1,000
220,000 feet, multiply SCF by 10, 000
The latest balloon stratospheric C-14 data (1960) which is available only from San Angelo, Texas, shows
a distribution similar to that at San Angelo in 1955, with some evidence that the peak concentration is below
90, 000 feet.
However, there may be a peak due to Teak and Orange above 90, 000 feet.
Because of the ambi-
guity in possible sources, it will be necessary to follow the existing distribution of C-14 in space and time to
study the role played by the atmosphere.
It does have the advantage of being a gaseous tracer and can be pre-
sumed to move with the air parcels.
Strontium-90.
A series of aircraft filtering flights were made in May and early June 1960 to collect radio-
activity on a world-wide basis at four latitudes and at altitudes from 15, 000 to over 65, 000 feet.
These data,
supplemented by balloon collections made at San Angelo, Texas, to 90,000 feet and by preliminary results of
surface air concentration measurements made by the Naval Research Laboratory, are shownin the figures.
The data are expressed in d/m/1000 scf on sampling day, unless otherwise indicated.
Values in italics refer to
observations reported as tropospheric.
The distribution of Sr-~90 is shown in Figure 2.
As can be seen, the lowest stratospheric concentrations
appear in equatorial regions, with somewhat higher values in the temperate and polar stratosphere.
It is some-
what surprising to see that the southern hemisphere stratospheric concentrations are the same or slightly higher
than the northern hemisphere values, despite the fact that almost all of the Sr-30 was injected north of the
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