MEASUREMENTSOF AIRBORNE RADIONUCLIDES
213
of the various radionuclides in these samples to their '*"Cs content are
plotted as a function of latitude. It is interesting that these ratios are
essentially constant with changing latitude for all the radionuclides
except ®8y, ‘sb, and Zr. These three radionuclides have short half-
lives compared with the others, and it might be expected that their
concentration would decrease with decreasing latitude since the most
recent high-yield nuclear shots were made at a high latitude, This is
generally true for *Zr—*Nb since it does decrease with decreasing
latitude. However, both **y and '4Sb show peak concentrations at about
41 and 63°N, and a definite lack of mixing relative to "Cs.
DEPOSITION AND PROPERTIES
OF AIRBORNE RADIONUCLIDES
It has been pointed out that a definite correlation exists between
the air concentrations of radionuclides and the seasonal precipitation
rate.'* This correlation appears to exist at our sampling location in
Richland, Wash., as shown in Fig, 11. Here the monthly precipitation
rate shows the typical inverse relation to the '*Cs content of the air.
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Fig. 11—Comparison of airborne '¥’Cs concentration with annual precipitation.