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and hovizontaiiy and leak. down uniformly over the world at a
vate of about 16% per year (this would correspond to a mean
cesidence time of six years) into the troposphere where it is
removed in about one month by normal weather processes and by
impinging on the curface of trees, grass and other features of the
eacth.
Its main time is spent in the top 30,000 feet of the
troposphere for it spends only about three days on the average
in the bottom 10,000 feet.
In this lower layer the possibility
of being brought down by rainfall and surface impact is at a
maximum.
We have considerable evidence which is in the forma-
tive stages and we can expect that during the next weeks and
mor.ths, the pasticular type of measurements diuplayed in Table II
which bear on the fate of the Russian October 1958 debris wili
be most revealing.
These data, tosether with measurements on
tue chodium-102 and the tritium from the hizh ctratosphere
August shots over Johnson Island vchould very nearly settle most
of the major points about the stratospheric mixing mechanism.
Til.
THE ASSIMILATION INTC THE BIOSPHERE
The great question arises as to whether and at what rate
the faliout is taken into the biosphere.
During Operation
Hardtack, a considerable effort was made to introduce tonnages
of silica sand into the firing bares on the thought chat
strontium-90 might thus be incorporated into glass-type