VARIATION OF RADIOACTIVITY IN SURFACE AIR
505
less than 5%. Soviet testing in 1961 accounted for more than 90% of the
137Cg in the spring of 1962, 25 to 30% in 1963, and less than 20% in
1964. Of the 1961 debris present in the spring of 1964, all is presumed
to be due to high-altitude shots. The Operation Dominic I series appeared to account for 5% or less of the total debris in both 1963 and
1964, Approximately 70% of the debris in 1963 and 75% in 1964is at-
tributed to the Soviet 1962 tests. The slow decrease in the concentra-
tion of "Cs in surface air from the Soviet 1962 tests in going from the
spring of 1963 to the spring of 1964 supports the contention that this
debris is contained well up in the stratosphere and will continue to be
the source of relatively high '*"Cs levels for the next few years.
In summary, a change in the time of the occurrence of tk
spring
maximum during 1961 through 1964 has been accompanied by changes
in the relative intensity of the maximums observed at Argonne and
at Chilton, England. The source of debris appears to be the sameat
both locations, and the change in amplitude is attributed to a change in
general atmospheric circulation patterns. The rather slow decrease in
intensity of the spring maximum between 1963 and 1964 points to a large
stratospheric source, one which may lead to substantial maximums for
the next few years.
REFERENCES
1. P, F. Gustafson, S.S. Brar, and U, C. Mishra, Determination of Airborne
Fission Product Radioactivity Using Gamma-Ray Spectrometry, Nature, 195:
557-559 (1962),
2, P, F, Gustafson, $8.8, Brar, and M, A. Kerrigan, Airborne Radioactivity Due
to Nuclear Weapons Tests, J. Geophys. Res., 67: 4641-4651 (1962).
3. R. S, Cambray, E. M, R. Fisher, G. S. Spicer, C. G. Wallace, and T. J.
Webber, Radioactive Fall-Out in Air and Rain Results to the Middie of 1963,
British Report AERE-R-4392, 1963.
4. L. B. Lockhart, Jr., R. L. Patterson, Jr., A. W. Saunders, Jr., and R. W.
Black, Fission Product Radioactivity in the Air Along the 80th Meridian
(West) During 1959, Report NRL-5528, Naval Research Laboratory, Aug, 15,
1960.
5. L. B. Lockhart, Jr., R, L. Patterson, Jr., A. W. Saunders, Jr., and R. W.
Black, Summary Report on Fission Product Radioactivity in the Air Along
the 80th Meridian (West) 1957-1962, Report NRL-6104, Naval Research
Laboratory, Apr. 2, 1964,
6. M. I. Kalkstein, Rhodium-102 High-Altitude Tracer Experiment, Science,
137: 645-652 (1962).
. L. P, Salter, High Altitude Balloon Sampling Program, in Fallout Program
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and Safety Laboratory, Oct. 1, 1963.
8. L. P, Salter, High Altitude Balloon Sampling Program, in Fallout Program
Quarterly Summary Report, USAEC Report HASL-149, pp. 54-99, Health and
Safety Laboratory, Oct. 1, 1964.
9, E. P, Hardy, Jr., J, Rivera, and R. Frankel, Global Atmospheric Radioactivity, May-June 1961, in Fallout Quarterly Summary Report, USAEC Report HASL-117, pp. 225-229, Health and Safety Laboratory, Dec. 30, 1961.