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of this element to form complex anions with the chlorine in the sea water, After
six montha, more than 99 per cent of these soluble elements had been carried off
to sea by the normal flushing processes occurring in the lagoon, Loss of strontium 91 by this process had the effect of diminishing the amount of its daughter,
53-day yttrium 91, which otherwise would have been 4 more eignificant contributor
to the present activity of the botton,
The radioactive materials carried down by the process just described are by
no means evenly or symmetrically distributed on the bottom; the detaile of the
distribution are so complex that only a rough, qualitative estimate of the total
radioactive material on the bottom has been possible, The greater part of the
material was deposited near the center of the target array, but patches of as
much as forty-fold higher activity per wit weight are found further out, and
the data suggested that the most active material waa deposited near the outer
edge of the colum,
Generally, the most active deposits are at the surface of
the bottom, but in some places rich deposits are overlaid by poorer ones,
At the present time worms and sea cucumbers are burrowing actively in and
eating the highly radioactive bottom mud, Most of this passes right through then,
and some of the feces are left on top, where bacteria compost them, returning most
of the active material to the mud,
However, some is left available to plante,
which grow on the altered material, These plants are eaten by amall fish, which
pase almdst all the radioactive material through the gut, Small fish with the
amall fraction of radioactive material they have retained in their tissues are
in turn eaten by large fish, which again eliminate most of the radioactivity,
carrying some of it to distant parts of the lagoon and even outside. Plants remote from the explosion center get traces of radioactive material in this way,
and the cycle is continued. The net tendency is to spread the material evenly
over the lagoon bottom and to carry a certain amomt of it out to sea.
It is time to consider the ultimate fate of the radioactive material now in
or on the lagoon bottom, Fission product attrition by decay is much faster than
by biological processes, Within a year, decay alone will have reduced the activity in total energy to 30 per cent of what it is now, and the flesh of the lagoon
fish will not, on the average, be as radioactive as normal human flesh. In five
years, only 4” per cent of the present activity will remain, and radioactivity of
the fish will be completely lost in the backgroud, In 10° years, less than 1 per
cent of the present Pission product activity will remain in Bikini dagoon, For
plutonium, attrition by biological processes, although probably less than 1 per
cent per year, no doubt will outstrip radioactive decay.
The present activity
from plutonium will remain substantially unchanged for many years, but the rate
of transfer to foods will be so slow as to constitute little hazard.
The idea that plants and animale may concentrate radioactive material has
. often been expressed. By way of definition, a radioactive material may be termed .
concentrated when the amount of radioactive energy per second per unit weight of
organic tissue exceeds the amount per unit weight of soil or water in the case of
& plant, or the average for food received in the case of a fish or other animal.
Concentrations of radioactivity by plants up to several hundred fold had definitely occurred in the first two weeks after test Baker, No fish collected at
that time exhibited any gross concentration, though the gills, livers and spleens
of some of the fish did show concentrations as high as a factor of 10 over the
stomach contents,
The plants collected in the lagoon a year later, after care-
ful washing with salt water to remove the silt, were in general much less radioactive than the coral rock on which they grew,
Exceptions to this statement oc-
curred chiefly in the case of Halimeda which exhibited counting ratea as high as
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