a.
from which samples were combined for analysis.
Five plankton samples were analysed in detail for their
radioisotopic content eleven months after the date of collection.
These included
sample No.
I
II
Stations
7, 8, 9
13,14,15
IiI
43,44,45,46
IV
50,51,52,53
Vv
57,58,59
The samples were filtered through No. 1 Whatman filter
papers and the plankton and filtrate fractions dried separately.
Gamma spectra were made from both fractions.
The
plankton samples were then wet ashed with concentrated
nitric acid and hydrogen peroxide and converted to the
chloride form by evaporating the sample to partial dryness
repeatedly with hydrochloric acid.
dissolved in 0.2 N HCl,
filtered,
The moist salts were
and the filtrate passed
through a cation-exchange column (5 mm x 100 mm) of Dowex 50
(13, 24, 12, 16).
Two hundred and fifty mgm or less of the sample in 0.2 N
HC1 solution were passed through the column at & rate of 0.2 0.5 ml per minute, then the resin was washed with 50 ml of
0.2 N HCl.
The eluate from the sample and the subsequent
hydrochloric acid wash contained those tons not adsorbed to
the resin, i.e. the anions.
These included Zr95-Nb?> and/or