MEASUREMENTS OF AIRBORNE RADIONUCLIDES
209
Table 2——RATIO OF 33py TO ics
IN GROUND-LEVEL AIR AT RICHLAND,
WASH., FROM APRIL 1962 THROUGH
JUNE 1964
Ratio, x 103
Month
January
February
March
April.
May
June
duly
August
September
October
November
December
1962
1963
1964
5.8
7.6
8.2
5.5
6.2
4.6
2.6
3.9
3.7
4.3
4.0
3.2
3.5
3.6
3.0
8.2
10.0
* 8.9
13.0
9.0
4.5
3.0
5.2
4.1
3.0
9.6
2.4
from air filters has shown that the ratio of *®Pu to **Pu is less than
0.02 at the present time.
It is both interesting and significant that the activation products
88y (105 days) and !4sbh (60 days) reached concentrations this year
(1964)
which are
comparable with those of last year, whereas the
fission product *Zr—*Nb (65 days) is lower by about a factor of 20.
Also, the fission product '87Cs (30 years) reached a concentration
comparable with that of last year, and !°*Ru (1 year) and '4Ce (285
days) reached a concentration about one-half that of last year. Since
there have been no nuclear detonations aboveground!” during 1963 and
through September 1964, all of these radionuclides entered the atmosphere prior to 1963, and their reservoir in the atmosphere has decreased with their respective half-lives since that time. These con-
centrations point to an obviously different source of ®y and 'Sb
relative to most of the *Zr—*%Nb and the other fission products. In
Fig. 7 the air concentrations of **y and ‘Sb have been corrected for
decay to the time of their probable injection into the atmosphere’ and
are compared with '*"Cs, The large increasein the fallout rates of *y
and }4Sb relative to '*"Cs clearly points to a different origin.
AIR PROFILES OF RADIONUCLIDES
During the 1962 nuclear-weapons testing period, a few sampling
flights were made. The flights were planned with the object of measuring air profiles under specific meteorological conditions, Air was
drawn by a vacuum pump through a membranefilter of 5p pore size