that Sr-90 is depleted relative to Ce-l4u) (as it may be relative to Cs-137).
If the Sr-90 depletion is true for all samples, then the apparent time of
formation, again, is earlier and the percentage of October 16th Sr-90 is
smaller than shown in Table 1.
Another possible source of error in the treatment of the data may result
from errors in the radiochemical analysis.
A comparison of samples
between laboratories reveals good agreement in all isotopes except Zr-95 according to Dr. J. Harley.
However, the results derived from the Zr-95 are similar
to those derived from Sr-89 suggesting random rather than systematic errors in
the Zr-95.
Further it should be noted that a systematic error in the analysis
of Sr-89 or Sr-90 (the two isotopes common to both the U. S. fallout and
stratospheric samples); will affect the apparent ages and percentages of
October 18th Sr-90 in analogous fashions.
The sense of the difference in apparent age and fraction of October 18th
long-lived fission products between fallout and stratospheric samples noted
above was also reported in a recent U.N.S.C. meeting by the U. K. using air-
craft over Englend up to about 50,000 feet.
In this case gamma spectroscopy
rather than radiochemical analysis was employed and tropospheric samples were
also collected by aircraft.
The difference in age and proportions of October debris has an interesting implication in the likely location of exit of the Soviet October. 1958
debris from the stratosphere.
NAS
First, 1t appears that the Sr-90 in fallout or in the troposphere in the
first half of 1959 has a different proportion of Soviet October 1958 debris’
than appears in the stratosphere in the same latitudes as the fallout observations.
Thus, debris is entering the troposphere from a reservoir other
than directly over the 30-50°N latitude band.
Since most of the Sr-90 found
in fallout in the first half of 1959 originated in the Arctic and is not
found in the temperate latitude stratosphere, it is unlikely that it has
passed south of say, 50°N.
Its probable exit from the stratosphere is, there~-
fore, farther north than 50° N, or closer to its original latitude.
One reasonable interpretation of the fallout and stratospheric apparent
age determination indicates that debris initially in the Arctic leaves the
stratosphere in Arctic latitudes.
Since we have only looked at this compari-
son in the first half of 1959, the location of exit cannot be generalized to
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Fos. ROM TE COLLECTIONS
OF PME tacntvi3 OF THE
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