China's 6th test in June 1967, but this did not closely match the
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Pu-239 increase either in magnitude or timing.
Further, in the mid
latitudes in 1968, and in all latitudes in 1969, increases in the
Pu-238/Pu-239 occurred.
On balance, we do not feel that the data support major tropospheric injections of Pu-239 to account for the anomalous Pu-239/Sr-90
ratios in the Northern Hemisphere.
There is, however, a good deal of
evidence of global, or at least hemispheric distribution of material
emanating from limited sources at the earth's surface.
As examples:
lead, identifiable as originating in urban environments has been found
in both the Arctic and Antarctic
(12); dust,
derived from the arid
regions Of West Africa, has been traced westward across the Atlantic
Ocean to Barbados
Antarctic fauna
(13);
(14),
and pesticide residues found in organs of
also must have been transported in the tropos-
phere many thousands of miles.
Thus there is not sufficient evidence
5.
Fractionation in the troposphere.
j th. tess,
This fifth possible explana-
tion for the observed anomalies in the Pu-239/Sr-90 ratios offers
much to the imagination, but there is little if any real positive
evidence.
Negatively, it can be demonstrated from Figure 3,
that
this had never happened to any observable extent in the preceeding
two years.
Also,
it seems reasonable to assume that if the surface
+
SAE CRMs ope ReteHEMER Ineer « 2 eh an iscinenn™
CRO On na ees
at this time to fule out this possibility.
I - 21