28 dis/min Sb'**, 300 dis/min Ru!**, 310 dis/min Zr®®, 26 dis/min Mn®*4, 330 dis/min Zn*
52 dis/min Co™ per gram.
‘
and
Barnacles collected tn the open ocean northwest of Bikini Atoll at 12° 27’N 165° 56.1’ Fr on
12 July 1956 after a nine-week period of growth during testing displayed 1,700 dis/min Ce!4
1,100 dis/min Sb'¥, 12,000 dis/min Ru’, 3,000 dis/min Ru, 1,000 dis/min Zr, 5,700 dis/
min Mn**, 3,000 dis/min Zn® and 160 dis/min Co™ per wet gram of body.
Tridacna clam livers collected in Bikini Lagoon during June 1956 and assayed 1 January 1957
showed cobalt contamination of the order of 50,000 dis/min Co® and 14,000 dis/min Co*? per
gram of the dry organ similar to the pre-Redwing specimens with the addition of only a few Per.
cent of Ru’? and Zr®®, On the other hand, a young, 3-inch tridacna clam collected off site ig
late July 1956 and assayed 6 March 1957 showed predominately recent 71-day 140 x 10° dis/min
Co®, 20x 10° dis/min Mn*4, 30x 10° dis/min Ru’, with Ce’44, Zr, and Zn® also present.
After completion of Redwing testing, a survey of plankton across the equatorial Pacific Showed
2,500 (dis/min)/gm at 11°N 160°E to 10 dis/min at 11°S 164°E. Figure 5.5 gives the total dis/
min of Ce!Ru!3) Rul 7) Mind! Zn85, Coe”, Coe’, and Co™ per gram drained plankton with
the percentage of Zn®® given in parenthesis.
Duplicate samples taken a month apart at 11°N 164°
E showed chiefly uranium fission products with 17 percent Zn®at first sampling and then the
nonfission products, cobalt, manganese, and zinc with 70 percent Zn* in the sample collected
3 September 1956. The Co® concentration in the Equapac plankton ranged from 1 to 4 percent.
One sample, rich in pteropods, from 11°N160°E assayed 16 percent Co and 22 percent Zn®,
Samples from the two adjacent stations assayed 90 percent and 83 percent Zn*®, and 1 percent
and 0.7 percent of Co®*, The cobalt concentration appears to be related to the pteropod population,
If this is true, then perhaps Co® could be used as a tracer for measuring the mass movementof
a pteropod colony, which may tend to retain the radioactive material within a given mass of water,
5.3 THEORY
A partition of chemical species should occur between the air and water interface of the oceans,
where solution and precipitation take place.
This process of separation continues to take place
in the water, wherein temperature, pressure, and pH effects comeinto action. A separation of
the more-soluble from the less-soluble compounds will tend to concentrate certain isotopes in
one phase or another. Biological fractionation and concentrations will occur through the specifie
ingestion and absorption of certain elements by marine bacteria and plankton. Specific radionuclides will be concentrated in such organs as the liver and skeleton of commercially important
food fish. An attempt was to be made to determine the distribution of the radioactivity among
the various marine phases.
5.4 OPERATIONS
5.4.1 Airborne Analysis. Airborne particulate.matter was sampled after each shot witha
vacuum pump and Millipore aerosol filters. A known rate of air volume was filtered fora
known period of time. In most instances, air was sampled for an hour at the rate of 20 liters/
min. During periods of high airborne activity, samples were taken for particulate size determination by filtering the air through a series of three graded filters, ranging from approximately
10 to 0.45 microns. These filters have not been calibrated and give only an approximate indication of the particle sizes retained. Decay curves were plotted for several of the samples to determine if any differentiation existed between various samples.
5.4.2
Water Analysis.
Water samples were obtained from the sea surface and from various
depths over varying times. Surface water was collected and stored in polyethylene bottles for
later analysis. Depth samples were taken with Nansen bottles. Whenever possible, samples
were worked up without storage to prevent any possible change or adsorption by the storage
container.
112