-land a 70% rather than h0% efficiency for the gumasd film.
It is,
therefore, concluded that more than 10% comes down per year. Or.
Libby's more recent talks reflect this possibility. It would be
highly desirable to ascertain wheather the calculated removal of
10% per year very seriously tnderestinates the trus deposition,
onMt£795trontthequestion fthe Laatas
depceceang engcehs “ abbhatt 4
years following thermonuclear tests, thare are also problems
Wi
concerning the propriety of extrapolating the fractional removal
of the stratospheric debris inte the future.
It is implied that
the removal process 4s by diffusion and that the initial distribue
tion is not such that the first year or two would yield anomolous
results,
constant.
With time, it will becomes evident whether the 10% is
Already, however,there is data suggesting irregularities
i
in the stratospheric removal. During 1955, a large fraction of ths
Strontium-90 fallout occurred in a&Gevt 3 or 4 months in Kew York
=we ncbeenee,
City rather than being spread evenly over the year.
Lest one
wp 6
conclude that this is a seasonal effair, it may be noted that it__aa
did not take place in the same months of 195) or in 1956.
It is concluded that Libby's approach to the determination
ether_ons but that it would be no surprise to find the percentage
stratcspheric removal to befargreater than 10% and to vary from
year to year,
Rainfall
-
Before concluding it may be worthwhile to evaluate rore
carefully how rainfall rexoves the Strontiun-90 fran the atmosphere
in view of ths fact that it is attached to
small particles
-delayed-felieut. For particles whose clamsters exceed a few
ricrons, it has been demonstrated that inertia and interception by
falling rain are reasonably efficient scrubbing agents but that for
particles less then ong micron, ¢),5° gdype of collection efficiency
ae tn get
DoD
uasils
a
of the rate of removal from the stratosphere soBatten
Sea