TABLE 4—Filter-Paper Collections Made at Washington, D. C.*
Bi fraction
Pb fraction
Date collected
Volume
processed
Mar. 1-31
Mar. 21-31
Mar. 21-Apr. 24
Mar. 31-Apr. 24
Apr. 3-15
2X 10?
5 X 108
2.5 10'f
2 « 10°
1.5 X 10°
(1960)
(fe)
B-achiuily
a-activily
B-activity
a-activity
1,960
960
90
410
2
4
2
8
4,770
2,040
1,210
8,510
5,610
4
112
34
274
128
(dpm)
(dpm)
Islands, Kodiak) showless activity, and
the collection made on a relatively
small land mass far removed from continental areas (Samoa) shows the least
activity.
All of the bismuth fractions
that were checked showed some
a-activity (Po?!).
Blower Collection
Air taken from outside was passed
through a 400 in? filter paper (Army
Chemical Corps Type 5) at about 2,000
ft?/min and vented in such a manner
that it was not drawn into the system
again.
At the end of the collection
period the filter paper was removed and
put into solution; the lead and bismuth
were separated in the same manner as
from thefloc.
these materials in the atmosphere.
It
Filter-paper
would be of interest to see how well
such a determination would agree with
the measured meanlifetime of about 15
days for RaD in the atmosphere as
determined from comparisons of the
short-lived radon decay products with
RaD in the air (1). No attempt is
made here to determine such a value
since the Po determination was not
made with sufficient accuracy.
The results suggest several generalizations:
1. High-capacity air filters and rainwater collections effectively provide
The remainder
2. The RaD activity collected by
rain varies widely at different places
(dpm)
(dpm)
¥* Activity not corrected for decay, absorption or backscattering.
+ Filter used as backing for Mar. 21-31 and Mar. 31-Apr. 24 collections.
of activity ; those on the coast (Panama)
or on largerislands (Hawaii, Philippine
Conclusions
The presence of RaD and Poin the
atmosphere suggests that a study of
the ratio of these activities can lead to
information relative to the lifetime of
Chemical procedure.
samples were dissolved by fuming with
hot nitric-sulfuric acid mixtures to
which a small quantity of hydrofluoric
large samples of airborne natural radioactive decay products.
of the procedure was the same as for
and at different times at any given
have been madesince the quantity of
collected with the character of the rain,
the seasons, or the quantity of dirt
present in the collection from rain.
acid had been added.
the rainwater samples.
Results. Results for the filter-paper
collections (Table 4) were similar to
those obtained with rain water. Only
rough estimates of the volumes of air
dust picked up by thefilter caused the
flow-rate to decrease continuously.
As considerable time elapsed between
the dates of collection at the various
sites and analysis at Washington, D. C.,
the RaD-RaE equilibrium had been
reestablished and RaE measurements
were essentially the measurements of
the RaD parent in the sample.
Printed in U.S.A,
place. On the basis of present information, there séems to be no simple
correlation of the quantity of activity
3. The average RaD activity varied
by a factor of 10 between island sites,
e.g., Samoa, and inland locations, e.g.,
Washington, D. C.
BIBLIO GRAPHY
I, I. H. Biifford, L. B. Lockhart, Jr.. H. B.
Rosenstock. On the natural radioactivity ip
the air, J. Geophys. Research ST, 499 (1952)
2. P. E, Damon, P. K. Kuroda, Nucireontica 11,
59 (1953)