~~
have done so quite extensively in the North Temperate Zone and farther
north.
The observed fallout pattern might thus represent distribution
of tropospheric fallout.
Undoubtedly, an appreciable part of the fall-
out observed in the Northern Hemisphere is the result of this mechanism
of transport, but whether this mechaniam accounts for five or ten or
more me Sr-90/mi~ of the present average of 30 ma Sr-90/mi” in the USA
is at present uncertain.
The pot collections of the AEC Health and
Safety laboratory in New York City (15) show jumps in the amount of Sr-90
collected during the winters of 1954-55 and 1955-56.
There was a definite
inorease in the slope of this cumulative tabulation at the time of Operation
TEAPOT at the Nevada test site in the spring of 1955, butthe following
year the increase occurred prior to the beginning of Operation REDWING at