wt gd ag
ss di oo iN
.
Sink Binsiwtat deeltL
sedantsLaeali
Dac TORS CONTROLLING THE DISTRIBUTION
living organisms.
OF THE RARE EARTHS IN THE
f
methium-147, and yttrium-90, 91.
RONMENT AND IN LIVING ORGANISMS
PHYSICO-CHEMICAL FACTORS
RALPH PV. PALUMBO
The physical half-life in combination with fission yield affects the abundance of the rare earth
nuclides produced during nuclear detonations.
Thus
as shown in Table 1 cerium-141 and lanthanum-i40,
the rare earth daughter of barium-140, are present
for 4 relatively short time after fission, whereas
Laboratory of Rudietion Bielows, Cniversity of Washington,
Senttte, Foshington
Cel44-_pri44
INTRODUCTION
time.
The rare earths include the elements in the
and promethium-147 persist for some
The results of radiochemical analyses of
plankton samples illustrate the fact that the composition of rare earth nuclides changes with time.
eriguac table from lanthanum to lutetium (atomic
simi-
Plankton samples collected one week after a series
nad scandium (atomic number 21) usually are inYuded in a discussion of the rare earths. This
23 per cent Bal40-1a140 and no detectable Cel44Prl44. Samples collected at six weeks, however,
Pusbers S7 through 71) and, because of their
ro chemical behavior, yttrium (atomic number 39)
uted five per cent of the total activity (Lowman,
1960).
About a year after the 1954 test series
bere carths exist in aqueous solutions only as the
This constancy of oxidation state
M@rivaient ions.
“rises from the fact that beyond lanthanum added
Biectrons enter an inner shell (4f) where space
The filling of the 41
MPor 14d clectrons exists.
bhel! ieads to the rare earth series and causes the
Bnuseal properties of the members of this series
The availability of radiolanthaM@Moclicr, 1956).
@ides and recent improvements in lon exchange and
Bolvent extraction techniques have made feasible
She previously difficult separation of these eie-
A comprehensive review of
pents from one another.
he radiochemistry of the rare earths has been prepared recently by Stevenson and Nervik (1961).
Because of their special characteristics and their
bundance in radioactive fallout, these nuclides
Beserve detailed consideration from the standpoint
pf their distribution in the environment and their
aptake by living organisms.
f
There is little information regarding the
presence of the rare earth elements in nature.
of nuclear tests in 1958 in the Pacific contained
contained no Bal40-Lal40 while Cel44-prl44 contrib-
losviy knit group of elements, often referred to
g the tanthanides or lanthanons, received little
“mttention unti, radionuclides of the group became
Under normal conditions the
Mavailable for study.
In
Harley (1956) found that 80 to 90 per cent of the
radioactivity in the plankton was due to Cel44-
Pri44; no other rare earth nuclides were reported.
Table 1.
Percentage abundance and physical halflife of some rare earth fission products.
Percentage abundance at:
Nuclide
Lanthanum- 140
Cerium-141
Cerium-144
Praseodymium-—144
Promethium-147
¥ttrium-90
¥ttrium-91
Neodymium-147
Praseodymium-143
Samarium-151
10
days
30
days
12.0
6.3
12.5
11.2
2.0
2.0
3.4
4.8
10.0
7.6
4.1
11.2
1
year
26.5
26.5
5.7
1.8
3.9
10
years
15.8
21.8
2.5
Physical”
half-life
40.2 hours
33.1 days
285 days
17.3 minutes
2.64 years
64.2 hours
o7.5 days
11.1 days
13.8 days
approx. 93
years
lerom Hunter, H.F., and N. E. Bailou (1951).
Vinogradov'’s (1953) compilation of the chemical
FOomposition of marine organisms only a few data are
*From Strominger, D., J.M. Hollander, and G.T. Seaborg,
Aum, and yttrium have been found in the coralline
is a most important factor in determining their uptake and distribution in the environment.
When the
given for the rare earths.
Trace amounts of
praseodymium, neodymium, samarium, cerium, lanthaSlga, Lithothamnion.
Yttrium has been found in
Fadiolarians, globigerina silts and gorgonaceans
nd samarium has been found in two species of corIs.
In the land environment small amounts of
Fare carths have been found in soils and in crops
nd native plants (Robinson, 1943).
The rare earths occur usually in insoluble
gorm and thus are not readily available for uptake
my
living systems. The tactors which control the
T he
ue lides
the physico-chemical and the bio-
biological factors relate to the
The physical state of the rare earth nuclides
rare earth nuclides are formed in the high tem-
peratures associated with nuclear detonations,
they exist probably as oxides; and upon contact
with other matter and with the sea or with fresh
water, they retain their particulate nature, primarily as the hydroxides of the type R(OH)3.
Greendale and Ballou (1954) determined the physical states of various fission products following their vaporization in sea water and distilled
cerium and yttrium was in the particulate state
(Fable 2).
‘inability of the organisms to absorb
Table 2.
.
nutrients enter them.
yPibusFh need
steo-chemical factors govern the
disluce one 10 a¥atlability of the nuclides
and inBte
ve radivactive haif-life,
Element
the physical
Cerium
and the chemical behavior
of the element.
cor tags
;
:
FMEG
Soe : othe“er for ceS in
:
nature which will
be
ito
Aa though many rad
ioac tive lanthanid
eeOTrBe ;
es are
ts
othe Production
of nuclear energy, only
Pothesa
dats te ft ™
te bare
4
(1958).
water and found that the major portion of the
Soin the particulate state, and these facRe mene
in turn on the types
of organisms and
. eds by which
e
a
This discussion will be concern-
ed primarily with Ce144-pr144, janthanum-140, pro-
nave
in
been
stu
died in relation to
thei
the environment
and
their
Physical state of cerium and yttrium
following an underwater vaporization.
Solution
sea water
distilled water
Yttrium
a
fate tear
sea water
distilled water
Physical state (per cent)
ionic
colloidal
1
2.7
0
0
0.4
4
4
0.5
2
2.2
0.2
1.6
1.3
particulate
6.6
13
19
95
94
99.5
98
98
93
86
80
lprom: Greendale, A.E., and N.E. Ballou (1954).
533