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RESULTS AND DISCUSSION
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In Table 3,1 the relative contribution of the nuclides recovered from
plant, soil and water are recorded, The data from which these values
were computed are shown in Table A.2, Appendix, In most cases the
surn of the separate nuclides exceeded the gross beta activity, a result
expected from the self-absorption of radiations which were uncorrected
in the gross beta determinations, The notable exceptions were the leaves
of arrowroot, pandanus and coconut, where only 57 to 85 per cent of the
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gross beta activity was represented by the nuclides sought. Gammaemitters other than those anticipated were not in evidence, Unfortunately,
insufficient active samples precluded clarification of this discrepancy,
|
The primary contaminating isotope in coconuts, papaya fruit, panda
nus keys and arrowroot tubers was Cs37,_ Significant quantities of the
rare earth components (16 to 18 per cent) were recovered from papaya
and arrowroot tubers and only a small fraction from coconuts and panda nus keys. The Sr?’ concentration in these specimens was uniformly low,
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The nuclide composition of the leafy structures in the coconut palm
and the arrowroot plant differed markedly from the respective nut and
tuber, These structures accumulated the rare earth isotopes in exceedingly greater concentration than Cs'*?7, These relationships account for
the observed gross beta-to-gammaratio previously mentioned, Samples
containing a preponderance of the rare earth radicelements would be
expected to give a higher beta-to-gamma ratio than those composed
almost entirely of Cs1%7,
Table 3.1 shows further that plant leaves contained varying percent-
ages of Rules and that the concentration of this isotope’ represented only
a small fraction of the total activity.
In portulaca, a widely distributed plant, the nuclide composition was
49, 39 and 12 per cent Cs}3’, rare earths, and Sr?, respectively,
Despite the inactivity of the water samples, rare earth and Sr?
determinations were performed since self-absorption as well as the size
of aliquot used may have obscured the activity,
Cs!? and Ru!"* were not
determined because self-absorption does not play an important role in
the detection of these gamma-emitters, The results of these analyses
are shown in Tables 3.1 and A.2 With the exception of a sample of
cistern water which had a significant quantity of Sr’, the observed
activity was attributable to the rare earths,
With regard to soil, the average of two Sate assays gave 84 per
cent rare earths, 10 per cent Ru!
5 ‘per cent Sr? and less than 1 per
cent C337,
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