618
VOLCHOK
The only other changes of note that have been made in the program
are that a different type of filter paper is used, gamma instead of beta
counting is used for measuring gross-fission-product radioactivity, and
some additional nuclide analyses for special situations are made.
90Sr LEVELS IN 1963
In Fig. 2 we have copied NRL’s presentation of Sr concentrations
in ground-level air of the northern hemisphere along the 80th meridian
(west) and have added HASL’s 1963 data. It is quite clear that the concentrations at all sites were higher in 1963 than in any previous year.
The peak values in 1963 are clearly the highest of all years reported.
Generally, the spring peaks in 1963 are quite broad, especially in the
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Fig. 2—Concentrations of °Sr in the air at selected sites in the north-
ern hemisphere along the 80th meridian (west). 1957-1962, NRL data;
1963, HASL data.