and plankton and to identify the principal radioisotopes in
the samples.
The USS Collett (DD730) was provided by the U. S.
Navy for the work and the survey included thirty-nine collecting
stations spaced on a fifty-mile grid (Fig. 1) in the area
bounded by 10°00'N and 13°20'N and 160°10'E and 166°00'E.
In
addition to the apove named radioisotopes, a neutron-induced
radioisotope,
tungsten-185, not previously found at the test
site by the present authors, was detected in high amounts in
some of the samples.
The gamma peak of wi85 was first observed
in gamma spectra made aboard the USS Collett on total plankton
samples; however,
the isotope was not positively identified
' until chemical separations were made.
In this paper the methods
used to establish the identity of the nuclides are described as
well as the pattern of distribution of the isotope in plankton
and other samples.
MATERIALS AND METHODS
The physical and chemical properties of w85 were used
to identify the isotope.
w85 decays principally by the
emission of a beta particle of an energy of approximately 0.43
MEV.
A gamma component (2.4 per cent) with an energy of 0.055
MEV is also emitted and can be readily identified in the gamma
spectra.