1454
PERSISTENCE OF TRITIUM AND #C IN THE PACIFIC PROVING GROUND
recent studies at the Chalk River Laboratories
of the Atomic Energy of Canada Limited,@”
concerned with dating tritium dispersal in
ground waterby tree-ring analysis, indicate that
part of the tissue-bound tritium of cellulose is
held as exchangeable hydroxyl ions. The effect
of these two processes on the tissue-bound
tritium data reported in this paper has not been
evaluated at this time.
The state of tritium in soil and geological
materials, especially those modificd and dis-
placed by a nuclear detonation, has not been
adequately described. According to RANKAMA
and Sanama,'") hydrogen is found in mineral
structures in the four following states: independent hydroxyls, structural water, hygroscopic
water and hydrides. Rock and soil materials
also contain interstitial water which is held by
capillary forces. Structural water and hygro-
scopic water, in addition to interstitial or
capillary water, are the most important to an
understanding of the problem considered. The
water usually most available to plants from the
soil is capillary and hygroscopic in form.
Hygroscopic water is generally assumed to be
available to plants to tensions of 31 atm (hygroscopic coefficient) and capillary wateris readily
available for absorption by roots. Structural
water cannot be removed without breaking
down the structure of the mineral, but there is
biological evidence in this paper and elsewhere
that structural water exchanges at some unknown
rate with the free capillary and hygroscopic
water of the soil or mineral materials.
The movement of tritiated water through
geological strata has been studied at the Idaho
Reactor Test site in connection with the
monitoring of waste disposal wells.2) An
attenuation of tritium concentrations in the
ground water was partially attributed to the
exchange of tritiated water, with water of
hydration or similarly bound water in the rock
strata. Ruyopes and Wirprnc*) conducted
experiments with exchange columnsof various
rock types and alluvial sediments, and passed
tritiated water through them. Even with small
columns, an attenuation oftritium concentration
occurred as the solution passed through the
columns.
The Eniwetok soil materials are composed
almost entirely of coral fragments and debris
(CaCO, and Ca(OH),). The work of Apany,
Fariow and ScHE."®) leads to the conclusion .
that these two compoundsare the sourceofthe ‘
high residual tritium and *4C in the soil samplg
from Eniwetok Atoll. Apams, FaRLow and
SCHELLstudied large particles formed in nuclea,
detonations at Eniwetok, Bikini, and the Nevaq,
Test Site.
Facts from the above data will help to inter.
pret the preliminary data in Tables 1-9. They
facts are:
(a) loosely-held tritiated water present in th
root zone of vascular plants enters and moig
within the plant along conventional physiolog.
ical pathways,
(b) various tissues of the plant exhibit ,
dynamic near-equilibrium relationship with the
tritium (THO)ofthe root zone,
(c) changes in the tritium concentration «
the available soil water will be reflected in,
short time in the loose-water tritium content:
someplant tissues, and
(d) tritium may become bound in falla
and substratum materials of the detonation s+ :
in a tightly-held hydrated or chemically bourc
state because of the fireball and post-detonaucr.
physicochemical phenomena.
Interpretation of results
The reproducibility of the data reported .;
at ¢
rele
wat
the
con
tran
valu
rium
the !
tree
is WI
the §
expe
Tr
the 3
the C
is no
moist
sidere
The
samp!
is tril.
menta
higher
in peri
to the
tinuum
af Mess
at earl
arc
cc
this paperis illustrated by the values in Table +
content
duplicated samples from the same specimen «-
compar
ereen le
These data were obtained from the analvsy
original sample.
The water samples sh-
excellent agreement and are both within tic-
prescribed errors. The wood samples, in genera
show good agreement except for the one sample
which showsanerror by a factor of 2. Since.
was not possible to obtain duplicate samples
every case, the data must be interpreted wic
this variation in mind.
The data in Tables |, 2 and 3 indicate thai. ;
most of the environments from which thesamp~ |
were obtained, a considerable source of trius7 |
exists in a boundstate within the soil materiae
andis slowly exchanging with the loose waters
the soil. As expected, an increased level «
tritium in the loose soil water produced a
increasedlevel oftritium in the loose waterofthe
leaves of plants growing on thatsoil. Theloo
water tritium ofMesserschmidia wood (3230 T.U
varying
12-l5 n
On E
water in
contentc
available
tritium |
4s much
‘urrent kc
Becaus
svatlable
sources be
the organ
to be anc
events she
above. T,
ieadily in
vid rapid!