Chapter 5
RADIOLOGICAL INVESTIGATION
of the MARINE ENVIRONMENT
5.1 OBJECTIVES
A modest radiochemical program was established in order to obtain information concerning
the distribution of radioactive contamination of an in situ marine environment.
to be accomplished aboard ship.
This work was
The objectives of the program were to sample the air over the
sea surface, water from various depths, sediments from the ocean floor, and marine organisms
for (1) the deter mination of gross radioactivity and (2) an examination of chemical or nuclide
partition among the various phases of the hydrosphere from both Redwing and previous operations.
3.2 BACKGROUND
The oceanographic conditions and background radioactivity prior to Operation Redwing have
been described in Reference 2, which details the sampling techniques, shipboard operations,
instrumentation, and preliminary results.
The study of the fallout problems of the fission products may be carried out in specific detail
in the laboratory and in retrospect after a nuclear detonation has occurred; but in so doing,
localized andtransitory effects may be lost.
The possibility of studying the fallout conditions as
they occur is desirable in the ocean, where continuous changes take place.
The ultimate fate of
the fallout fission products is important with respect to the contamination of the ocean waters
and of food fish.
The manner in which the radioactive isotopes enter the food chain may be
studied by early sampling and analysis of water, particulate matter, and planktonic organisms.
Mixed zooplankton collected around Bikini Atoll between 29 May and 8 June 1956 displayed
levels of activity ranging from 10* 3 dis/min in the southeast to 2 x 10° B dis/min per wet gram
northwest of the atoll. At Zuni + 10 hours 1.2 x 10® 8 dis/min of fission products were detected
in gross zooplankton, with individual organisms displaying 10‘ and 10° 8 dis/min, corresponding
roughly to the surface area of the plankton. The inability to accurately determine milligram
weights aboard ship prevented correlation of activity with mass.
At H+ 16 hours, fallout occurred aboard the M/V Horizon, producing a gamma background
that prevented the use of gamma counting. The gamma energy spectrum of a l-gram drained
wet weight sample of mixed zooplankton collected at 11° 27’N, 164° 33’E on 7 June 1956 is shown
in Figure 5.10. The complexity of the spectrum and the high background shown by the lower
curve prevented any identification of the nuclides present by gamma counting alone. After 16
months’ decay, the gamma spectrum of this sample indicated the presence of Ce, Ru’ zr,
Ma* and Zn® as shown in Figure 3.11.
Between Shots Flathead, 12 June 1956, and Navajo, 11 July 1956, a hydrographic survey was
undertaken between 11° and 13°N and 163° and 165° 40’ E during which water and plankton were
Collected for radioassay.
The relative activity of gross plankton varied from 3 x10* (y/min)/gm
at 11°N 165°40’ E to a maximum of 5 x10°(y/min)/gm at 12°30’N 165°E with 1.5 x 105 (y/min)/gm
detected along the 163°E western boundary of the survey from 11°N to 13°N between 30 June and
T July 1956. Radiochemical analysis on 1 January 1957 showed almost constant ratios of Ce‘*!,
Celsr89 Ru!Ru’ and Zr, with traces of Mn*4 and Zn®® among eight samples. Eleven
Months after collection at 12°N 165°E, on 6 July 1956, Sample S-44 assayed 1,300 dis/min Ce'™*,
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