304
FEELY AND BAZAN
CHANGES IN 9°Sr CONCENTRATIONS
The concentrations of nuclear debris in the stratosphere have
changed repeatedly during the course of the last three yearsin all
regions sampled. These changes have resulted from the injection of
new nuclear debris into the stratosphere at various times during 1961
and 1962, from the dilution of the new debris, from the movementof
debris from one region of the stratosphere to another, from radioactive
decay, and from fallout of debris into the troposphere and thence to the
ground.
In the northern hemisphere similar changes in concentration with
time generally seemed to occur at all altitudes, though there were some
differences between the trends at the higher and lower altitudes during
1962. This is evident from Fig. 2, in which are plotted the Sr concentrations found in the vicinity of Goodfellow Air Force Base, San
Angelo,
Tex., by balloon sampling at 65,000 to 70,000 ft and at about
105,000 ft. In general, during 1962 the Sr activities at 65,000 to
70,000 ft increased with time as debris first from the 1961 U.S.S.R.
tests, then from the 1962 United States tests, and finally from the 1962
U.S.S.R. tests reached 31°N. At 105,000 ft, however, no significant
change in *Sr concentrations was detected before early 1963. The
fission-product ratios in the new debris that reached San Angelo at
VW ETT TTT TTT TTT TT TT TTT TY TTT TTT TT
a
31°N
q
~ © 105,000 FT
A 70,000 FT
1. © 65,000 FT
“.
g
2
a
_
Tee
=
ES
i
=
=
a
=
=
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z
=
=
7
ef
-
-
>
>
107
Y
=
—_
3
<
3
4
4
&
—
10!
Lhptit trp tt leriprpi yi pip tippy pp ppp
JEFMAMJJASONDJFMAMJJASONDJFMAMJJASOND
1962
1963
1964
Fig. 2—-Trends in “Sr activity.