The distribution of activity between particulate and dissolved material in the well water is
presented in Table 4.6. Much of the activity was associated with particles that could be filtered
out of the water. Individual isotope analysis (Table 4.5), as well as the beta to gammaratio of
Rongelap water samples (Table 4.7), indicates that the ratio of strontium to rare earth, at 2
months postdetonation, is much higher in the liquid phase than in the filtered solid particles.
This is largely the result of the higher solubility of strontium salts compared to the other
radioelements and its longer radiological half life. Sr®® is potentially the most hazardous
TABLE 4.6—Distribution of Activity Between Particulate and Dissolved Material
in Rongelap Well Water
(43 Days Postdetonation)
Beta activity
pe
Sample
(Sr® equivalent)
A. Gross assay
H,O + suspended matter
HNO,washofbottle
Total
B. Centrifugation of an aliquot
Supernatant
Precipitate
Total beta
activity, %
0.54
0.35
60.6
39.4
0.89
100.0
0.018
0.033
35.3
64.7
0.051
100.0
Supernatant
0.010
20.0
Matcrial filtered out
0.040
86.6
0.050
100.0
Background
0.045
Less than 10
90-100
0.045
100
Total
C. Filtration
1. Through fine frittered glass
Total
2. Through #42 Whatman paper
and fine frittered glass bed
Supernatant
Material filtered out
Total
fission product associated with ingestion of water or with food in this particular situation. This
would not be true for situations in which exposure to fallout occurred at later times than that
which occurred here; nor would it be correct when long periods of exposure are to be considered, as compared with the short exposure of the Marshallese.
There was less than 7 x 10~® ug/liter of fissile material found in the cistern water examined.
(c) Soil, Thatch, and Grass. The most representative samples of fallout material on the
contaminated islands were obtained from soil and roof thatch. A sample of soil taken at 25
days in the center of the village on Rongelap showedanactivity of approximately 0.13 uc/g.
The contamination was associated with very fine particulate matter and was uniformly distributed throughout the individual samples. Autoradiographs of the soil samples indicated that the
activity was associated chiefly with fallout particles ranging from 60 to 200 » in diameter. A
sample of earth was separated in a multiple sieve and the specific activity of the various frac-
tions determined in an ionization chamber. The bulk of the activity was associated with the
smaller earth-particle sizes (less than 400 1) in diameter, and the highest specific activity was
observed on the smallest earth-particle size (less than 200 ), Table 4.8.
45