Mike shot. Comparison of counts of damaged and healthy leaves from Rigili plants showed no
al
marked differences between the two, indicating that most of the activity was on the surface
of the leaves.
Table 4.14 RADIOACTIVITY OF LAND PLANTS BY STATIONS*®
Preshot
Bi
Island
Postshot
Mean
nn
Max.
Min.
Japtan
Igurin
Rigili
0.014
0.28
0.58
14
22
17
0.074
«(3.7
8.6
Background
Background
Background
Bogombogo
0.12
22
«1.6
Background
Engebi
Aomon and Rojoa_
Runit
0.83
0.28
24
«(3.4
3001.3
0.092
Background
“Mean
0.24
16
100
1900
89
40
on
Max.
Min.
8
11
20
0.33
39
820
0.13
0.83
1.0
6
12
2
4000
370
60
280
4.9
20
* Measured in disintegrations per minute per gram (x 1000), wet sample.
4.6.2 Analysis by Species
Because of the incompleteness of the collections and the great variation within species, it
is not reasonable to attempt to determine whether significant differences in the amount of
activity exist between species. From the data available it appears that bunch grass, Lepturus
yvepens, had the highest activity of the plants collected at Rigili and Rojoa after the shot. On
the other hand, Mycena, a fungus, was among the highest at Rigill, but lowest at Igurin. Because of inconsistencies of this nature, conclusions as to species differences are not justifiable.
4.6.3
Analysis by Organs
No specific conclusions can be made regarding radioactivity in the organs of the land
plants collected before and after Mike shot because of the inconsistencies encountered. At
somecollecting areas the roots had the highest activity, at others the lowest. In general, the
leaves were highest. An insufficient number of flower and fruit samples was assayed from the
post-Mike series to warrant comparison.
4.6.4 Radiochemical Analyses
Radiochemical analyses of post-Mike soils from Rigili, Rojoa, and Runit and of post-Mike
I,
plants from Engebi were made in order to determine the identity and relative amounts of fis-
sion products present. By comparing the relative percentages of specific fission products in
plants with those found in the soil and knowing the solubility of these fission products in water,
it is possible to estimate which isotopes have entered the plant via the normal processes of
mineral absorption. The results (Table 4.15) are tabulated as percentage of total recovered
activity in the sample, although actual chemical yield was approximately 75 per cent of the
total radioactivity in the samples. If the percentages of the radioisotopes in plant and soll
samples are approximately the same, then it may be assumed that the radicactive material is
adsorbed onto the surfaces of the plants. The radiochemical analyses and the analytical procedures are described in Sec. 4.8 of this report. The radiochemical content of the soils from
the four islands is fairly uniform, with some exceptions noted in the Engebi soil. As in the
soil samples 80 to 85 per cent of the radioactivity in the land rlants from Engebi was found
in the highly insoluble fission products that are absorbed by the plants in minimal amounts
under normal conditions. The remaining portion cf the radioactivity is found in the more
48
. UNGLASSi o