Technical Note
ORP/LV-76-2
PARAMETERS FOR ESTIMATING
THE UPTAKE OF TRANSURANIC ELEMENTS
BY TERRESTRIAL PLANTS
MARCH 1976
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RADIATION PROGRAMS
LAS VEGAS FACILITY
LAS VEGAS, NEVADA 89114
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Technical Note
ORP/LV-76-2
PARAMETERS FOR ESTIMATING
THE UPTAKE OF TRANSURANIC ELEMENTS
BY TERRESTRIAL PLANTS
D. E. Bernhardt
G. G. Eadie
MARCH 1976
OFFICE OF RADIATION PROGRAMS--LAS VEGAS FACILITY
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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This report has been reviewed by the Office of Radiation
Programs - Las Vegas Facility, Environmental Protection Agency,
and approved for publication. Mention of trade names or
commercial products does not constitute endorsement or
recommendation for use.
11
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PREFACE
The Office of Radiation Programs of the U.S. Environmental
Protection Agency carries out a national program designed to
evaluate population exposure to ionizing and non-ionizing
radiation, and to promote development of controls necessary to
protect the public health and safety. This literature survey
was undertaken to assess the available information of parameters
for estimating the uptake of transuranic elements by terrestrial
plants. Readers of this report are encouraged to inform the
Office of Radiation Programs of any omissions or errors.
Comments or requests for further information are also invited.
Donald W. Hendricks
Director, Office of
Radiation Programs, LVF
111
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CONTENTS
Page
INTRODUCTION 1
SUMMARY AND CONCLUSIONS 2
DEPOSITION ON PLANT SURFACES 4
Consideration of Particle Size 5
Deposition Parameters 7
RADIONUCLIDE UPTAKE FROM SOIL BY PLANTS 12
COMBINATION OF DEPOSITION AND PLANT UPTAKE 19
REDISTRIBUTION OF ACTIVITY WITHIN PLANTS 21
REFERENCES 22
APPENDIX A
Parameters for Atlantic-Pacific Interoceanic Canal Model 28
LIST OF TABLES
Number Page
1 SUMMARY OF PLANT DEPOSITION AND RETENTION PARAMETERS 9
2 SUMMARY OF PLANT UPTAKE OF PLUTONIUM 13
3 PLUTONIUM IN VEGETATION AND SOIL 20
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INTRODUCTION
This report summarizes information from the literature
concerning parameters which can be used to estimate the transport
of transuranic elements through plants to man. The scope of the
report is limited to parameters for estimating the concentrations
of transuranics in terrestrial plants based on activity concen-
trations in soil and air.
There is only a limited amount of information specifically
concerning plant uptake of transuranics. In many instances it
has been necessary to use information based on other elements,
which interjects additional uncertainties due to the variance in
physical and chemical characteristics of these elements versus
the transuranics. Furthermore, most of the transuranic data
relates to plutonium; thus, this report focuses on plutonium.
Brown (1975) presents a bibliography of information concern-
ing plant uptake of americium. Americium has only received cur-
sory coverage in this review, although consideration has been
given to the differences between americium and plutonium in plant
uptake. Differences in the mobility and uptake of plutonium-238
and plutonium-239 are discussed. Papers concerning deposition
and retention of plutonium on reindeer lichens have been excluded.
Plant uptake results from root uptake and deposition of
contamination on above ground surface areas of the plant.
Although deposition or fallout on the plant may not actually be
taken into the plant tissue structure, Romney et al. (1975) and
Hanson (1975) note that it may be tightly bonded to the plant
microstructure and become essentially indistinguishable from
material in the plant tissue. Deposition on plant surfaces
occurs from both the initial contamination cloud and resuspension
of contaminated soil.
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SUMMARY AND CONCLUSIONS
The limited amount of available information is not adequate
to select precise parameters for estimating concentrations of
plutonium in vegetation due to root uptake and foliar deposition.
The existing data base is essentially non-existant for some
parameters, and shows significant variations for other para-
meters. Furthermore, much of the existing laboratory-generated
data is not directly applicable to the normal geographical and
climatological field conditions.
There is a significant variance in the estimates of the
particle size distribution for airborne plutonium. Estimates of
aerodynamic mean diameters appear to vary from sub-micrometer to
about 10 urn diameter particles. For given particle size distri-
butions, there are uncertainties in the deposition velocity,
vegetation interception factors, and retention parameters.
Furthermore, much of the experimental data appears to be for
particle-size distributions significantly larger than those
expected from normal nuclear reactor fuel cycle plant releases,
worldwide fallout, or resuspension. There is the additional
unknown feature in that specific plant deposition parameter work
has not been done with plutonium.
The plant deposition parameter information is summarized in
Table 1. These data imply a deposition interceptor factor
(F, pCi on vegetation per unit area subtended by the vegetation,
per pCi per unit area of ground) of about 0.2. Although the
measurement of this parameter is time dependent, the time after
deposition is generally not indicated in these studies. It
appears that the weathering half-life is short (hours to a day)
during the initial deposition period.
There is a significant range in the initial retention
estimates associated with the type of vegetation, and more
importantly, a variance associated with the time after deposition
when the measurement is made. The intervening wind and precipi-
tation conditions are also of prime importance.
It is suggested that the initial retention and weather half-
life data should be treated as sets for each individual study.
That is, the individual parameters should not be averaged between
studies without a detailed evaluation as to common situations
(e.g., time of measurements and climatology). Prudence appears
to indicate choice of a weathering half-life of about 30 days for
time periods of about a week after deposition. For small plants,
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not prone to trapping particles, a retention factor of about 20
to 30 percent appears reasonable, but there is considerable
uncertainty in the data.
Plant uptake parameters are summarized in Table 2. Hanson
(1975) estimates the plutonium uptake by plants to be about 10-1*.
Others generally categorize it as about 10-3to 10-6 which
includes most of the data in Table 2. Romney et al. (1970) and
Neubold (1963) present data that show a definite increase in
plant uptake with successive crops. Romney's et al. (1970) data
indicate about an order of magnitude increase, from 1.9 x 10-5 to
14 x 10-5 over a 5-year period. This increase is generally
related to microorganism activity in the soil (Au (1974) , and
Au and Beckert (1975)) and chelation by organics in the soil
(Romney et al. (1970)).
There is some indication that plutonium-238 is more mobile
than plutonium-239, but this has received only limited verifica-
tion. Cline (1967) reported that barley took up 50 times as much
americium-241 as plutonium-239. Romney et al. (1974 and 1975)
have also reported that americium-241 appeared to be more mobile
than plutonium.
Essentially all of the plutonium uptake studies are based on
laboratory experiments containing plutonium uniformly mixed
throughout the soil volume thereby increasing root contact.
Results therefore appear to be unrealistic for natural vegetation
where the deposited plutonium is largely limited to the upper
2 to 5 cm of soil, above the natural root mat. Therefore, the
laboratory results should be conservative for most natural plant
species growing in undisturbed or unplowed land; but, the uniform
distribution of the plutonium in the laboratory soil should be
representative of farm crops grown on plowed land.
Bloom et al, (1974) and Martin et al. (1974) report data
from Romney et al. (1974) indicating plant uptake from Nevada
Test Site field studies. A total plant uptake of about 0.3 is
inferred. They also estimate a total long-term uptake (20 years)
of about 0.3 by exponentially extrapolating Romney?s et al.
(1970) 5-year study to 20 years. Romney et al. (1974 and 1975)
qualify the 0.3 uptake as being from both root uptake and deposi-
tion and they emphasize that deposition is the primary contrib-
utor, probably by several orders of magnitude.
There appears to be general consensus that deposited
plutonium is not taken up (by foliar absorption) into the plant;
rather, it is generally immobile. This hypothesis is based on
limited information.
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DEPOSITION ON PLANT SURFACES
The following parameters are used in the deposition pathway:
- Deposition velocity: This may be given with respect to
the ground surface or for vegetation. If the deposition
velocity for the ground is used, the plant intercept area
or factor must be used.
- Plant interception factor (F): Witherspoon and Taylor
(1969) defined F=WC°/m,
where:
W is the biomass of foliage in grams (dry weight)
per square foot of soil surface area (g/ft2).
C° is the quantity of radionuclide initially
intercepted per gram dry weight of foliage
(yCi/g).
m is the quantity of radionuclide deposited per
ft2 of soil surface area.
Thus, F is the ratio of radioactivity deposited on the
foliage to the radioactivity deposited on the ground
area inhabited by the foliage. The ratio has no units.
The product of the deposition velocity for the ground
surface and F is the initial effective deposition
velocity for vegetation.
- The initial retention factor, (f), is the fraction of
radioactivity originally deposited that remains at some
time after deposition. This is usually given for one to
two weeks after deposition.
- The weathering or retention half-life (Tw) represents the
exponential decrease in the retention of deposited
activity after the initial one to two week period.
- The plant biomass of foliage (W) is given as grams dry
weight per square meter.
- The fraction of deposited activity that is actually taken
into the plant is denoted as (d).
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CONSIDERATION OF PARTICLE SIZE
The deposition velocity, plant interception factor, and
plant retention of deposited material are all a function of the
particle size distribution. The size distribution of airborne
particulates is related to the source of release. Particle size
distributions vary from the micrometer and sub-micrometer dia-
meter for nuclear fuel cycle plants and worldwide fallout to tens
of micrometers for near-in fallout and aged fallout in the soil.
High efficiency particulate air filters (HEPA) are used to
minimize releases from nuclear fuel cycle plants. HEPA filters
have removal efficiencies of 99.97 percent for 0.3 ym diameter
dioctyl phthalate smoke particles; thus, releases from most
nuclear installations are assumed to be in the sub-micrometer
size range (Burchstad (1967)). Moss et al. (1961) also report
mass median diameters of less than 1 ym for airborne plutonium in
working areas of a plutonium fabrication plant.
Klement (1965) indicates that particulates from nuclear
explosions are generally in the sub-micrometer range; but, they
may become attached to other material forming conglomerates of
10 ym or more (Gudiksen and Lynch (1975), and Nevissi and Schell
(1975)). Generally, worldwide fallout is classed in the microm-
eter to sub-micrometer diameter size.
The size distribution of resuspended material is dependent
on both its original size and composition, and on the material to
which it becomes conglomerated within the soil. Bretthauer
et al. (1974) analyzed particles from air samples at the Nevada
Test Site (NTS) and observed plutonium-bearing particles from
less than 0.5 to 17 ym in diameter. The composition of the
particles ranged from plutonium, uranium, and oxygen (several
micrometer) to silicate and organic particles (about 10 ym). The
geometric mean particle diameter was about 1.5 ym.
Volchok et al. (1972) report data from two studies of
airborne particulates around the Rocky Flats Plant in Colorado.
The initial study, based on particles on particulate filters,
indicated a mean diameter around 10 ym. This study was poten-
tially biased by the lack of analysis sensitivity for particles
below 0.5 ym. Results from six cyclone and elutricator samples
(run time of about 50 hours) indicated median diameters of about
5 ym.
Tamura (1974 and 1975) reports on the particle size
distribution of plutonium in NTS soils. One to ten percent of
the activity was found in the 0 to 5 ym diameter soil fraction;
whereas, about 60 percent (up to 90 percent for several samples)
of the activity was found in the less than 53 ym size. Romney
et al. (1975) indicate that the micro-structure of many species
of vegetation is adept at capturing particles of these size
ranges. The bond between the vegetation and these particles is
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apparently so tenacious as to make it almost impossible to
distinguish the material from that actually taken up into the
plant.
Bloom et al. (1974) assume a particle size of 10 ym for
plutonium in air, which leads to a value of about 5 cm/sec for
the deposition velocity. These values are used in their environ-
mental plutonium model.
Bagnold (1945) and Chepil (1945a,b,c,d) indicate that over
90 percent of the wind movement of soil is by surface creep and
saltation. These phenomena occur at heights below 1 meter above
the ground surface and are not observed on standard air samples.
Surface creep and saltation are connected with movement of soil
particles of tens to hundreds of micrometers in diameter. Thus,
they include movement of the soil size fraction that contains the
majority of plutonium (Tamura (1974 and 1975)). Furthermore,
vegetation can retain particles of this size class, (Romney
et al. (1975)).
In summary, various investigators recommend a range of
particle sizes for airborne plutonium. Particle material from
original source terms is generally in the micrometer to sub-
micrometer class. Plutonium in soil (limited data, mostly from
NTS) appears to be predominately associated with particles
between 20-50 pm in diameter (Tamura (1974 and 1975)). The
limited information from Bretthauer et al. (1974) and Volchok
et al. (1972) indicate that the mean diameter of resuspended
plutonium particles is less than 10 ym, probably around 5 um.
Much of the activity deposition on plants with foliage near the
ground, would appear to result from surface creep and saltation
associated with the larger diameter particles (10 to 100 urn)
versus resuspended material.
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DEPOSITION PARAMETERS
Witherspoon and Taylor (1969) present data for simulated
fallout on pine and oak trees, using cesium-134 as a tracer. The
initial fraction (F) of the simulant fallout (88 to 175 ym
diameter particles) intercepted and retained by foliage was
higher in the oak tree (0.35) than in the pine tree (0.24).
After 1 hour, the broad-leaved oak lost about 90.5 percent of the
initial deposition, while the pine loss was only about 10 percent,
corresponding to initial retention factors of 0.095 and 0.90,
respectively. Weathering half-lives (Tw) due to wind, rain, and
all other environmental factors were determined to be 25 and 21
days for the oak and pine trees, respectively, for the period
from 7 to 33 days after initial fallout deposition.
Witherspoon and Taylor (1970) present data for five crops
using simulated fallout with rubidium-86 as a tracer. Two sizes
of quartz particles (44 to 88 urn and 85 to 175 ym diameter) were
used on squash, soybean, sorghum, lespedeza, and peanuts. For
the size range 44 to 88 ym, the fraction of fallout initially
intercepted (F) ranged from 0.075 for the small-leaved lespedeza
to 1.248 for the squash. Interception factors (F) greater than
unity were obtained for squash and soybean plants. Such plants,
which have bush-like structures, have large exposed surface areas
available in many different interception planes. The average
fraction intercepted (F) for the smaller diameter particle size
range was 0.587, which was about 2.5 times greater than F for the
larger particle size range.
Fisher (1966) predicts a theoretical decrease in the deposi-
tion velocity on pasture grass with decreasing particle size in
the 20 to 0.1 ym range. It would appear that using Witherspoon
and Taylor's data for the 44 to 84 ym range would be conserva-
tive, but there is limited information on which to base this
hypothesis.
Witherspoon and Taylor (1970) also studied particle reten-
tion. Losses from plant foliage due to wind removal (during the
first 12 hours postdeposition) ranged from 3 to 35 percent
(average--21.1 percent) for the 44 to 88 ym particles. During
the same period, losses for the larger particle size ranged from
9.5 to 26 percent (average--15.8 percent). For the 12- to
36-hour period postdeposition, losses ranged from 1.2 to 33.5
percent (average--15.4 percent) for the smaller size simulant and
ranged from 7.7 to 34 percent (average--21.6 percent) for the
larger size simulant. Therefore, during the first 12 hours of
postdeposition, when the wind speed averaged 0.5 mph and there
was no rainfall, the plants lost an average of 18.5 percent of
the initial deposition. This corresponds to an average value of
the initial retention factor (f) of 0.815. Losses for the next
24 hours also averaged 18.5 percent. From 1.5 to 7 days post-
deposition, the plant retention dropped from 63 percent to
about 33 percent. This decrease was largely related to 0.25
7
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inches of rain on the sixth day. Retention dropped to 7.9 per-
cent of initial deposition during the second week, after a heavy
rainfall of 1.33 inches. Another intense rainfall caused a sharp
decrease in fallout retention to 3.3 percent, which slowly
decreased during the remainder of the experiment.
The weathering half-lives (Tu) for the 44-84 urn particles
were 26 days for the 14- to 28-day postdeposition period and 84
days for the 28- to 56-day postdeposition period. During the
entire 56-day study period, the weather half-lives (Too) ranged
from 2.09 to 272.8 days for the 44 to 88 urn particle size; and
1.33 to 56.5 days for the 88 to 175 ym particle size. This
experimental data indicates that large differences in initial
interception existed between plant species for different particle
size distributions, but that these differences become insignifi-
cant after about 1 week of exposure to environmental influences
such as wind and rain.
Witherspoon and Taylor (1970) report values for the activity
per dry gram of foliage, per activity per unit area of soil for
the five,crops. These values range from 0.01 to 0.2 ft2/g (10 to
200 cm2/g). The biomass values (W), in grams of dry foliage per
square meter of soil (dried at 100°C for 24 hours), ranged from
20 for lespedeza to 120 for soybeans. These data are for 6-week-
old plants at the time of deposition. The plants were planted
the last of May in the Oak Ridge, Tennessee, area. All of the
foregoing values are summarized in Table 1.
Concentrations of iodine-131 and strontium-89 on plants
contaminated by fallout from Project Sedan at the Nevada Test
Site were reported by Martin (1965). Examination of the fallout
deposited on foliage indicated that most of the activity was due
to particles less than 5 urn diameter, with virtually no retained
particles greater than 44 ym diameter. The observed effective
half-lives for iodine and strontium on the vegetation corres-
ponded to weathering half-lives (Taj) of 17 and 28 days.
Russell (1965) presents a review of interception and
retention of airborne material by vegetation. Based on data from
Milborn and Taylor (1965) concerning strontium-89, Russell con-
cludes that on the average nearly one-quarter of the deposited
fallout material is initially held on edible leaf tissues. An
equal quantity may be associated with the basal tissues. The
studies of Milbourn and Taylor also indicate that 50 percent of
the radioactivity present on the. edible herbage per unit area is
usually lost in about 14 days, the fraction of initially depos-
ited fission products lost from cabbage plants in a 28-day period
ranged from 0.83 for cesium-137 to 0.90 for ruthenium-106
(Middleton and Squire (1961)). Data were also presented which
indicated that washing cabbage leaves in water could remove from
10 to 36 percent of the deposited contamination (average of 24
percent). Middleton and Squire also concluded that the extent
of radionuclide absorbtion into leaves was of little importance
8
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TABLE 1. SUMMARY OF PLANT DEPOSITION AND RETENTION PARAMETERS
Reference
Wi
Wi
therspoon
therspoon
& Taylor
& Taylor
(1969)
(1969)
Plant
Interception
Factor F
0.35
0.24
Foliage
Biomass
(g,dry/m2)
Initial
Retention
Factor
0.095
0.90
Weathering
Half -Life
(Days)
25
21
Half-Life
Pertinent
Period (Days)
7 to 33
7 to 33
Comments
88 to
oak
88 to
pine
175 VITI
trees
175 urn
trees
particles,
particles,
Witherspoon & Taylor (1970)
Witherspoon & Taylor (1970)
Witherspoon & Taylor (1970)
Levin et al. (1970)
Levin et al. (1970)
Martin (1965)
Martin (1965)
Russell (1965)
Russell (1965)
Russell (1965)
Bloom et al. (1974)
Bloom et al. (1974)
Martin et al. (1974)
Milbourn & Taylor (1965)
0.075 to 1.2 20-120
20 lespedeza
120 soybeans
0.25 540 fruits
3500 leaves
5 cm2/g
0.14
5 cm2/g
0.14
2 wk
12 hr
1 wk
-OJ.5
^0.17
M3.10
26
14
17
28
30
30
14
14 to 28 44 to 88 ym particles,
6-wk old plants
Fallout, 1-131
Fallout, Sr-89
Cabbage, Cs-137
Cabbage, Ru-106
F factor divided by
biomass.
Assume biomass of
289g/m2
Project Sedan Sr-89
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compared to the retention of activity on the leaves.
Levin et al. (1970) discuss the choice of parameters for
dose model calculations for the proposed nuclear applications in
the construction of an interoceanic canal. The information they
present is oriented to South America and general fallout of mixed
fission products. Thus, the information has limited applica-
bility to conditions in the United States. A summary of their
parameters is given in Appendix A. Several of the more pertinent
values are:
--Fraction of the element in plant edibles which comes from
leaves (due to foliar deposition) of 0.05. This value
apparently relates to fruit type plants.
--W, biomass of plant edibles of 540 g/m2 (dry weight).
Biomass of plant leaves 3500 g/m2.
--Growth-rate coefficient for plant edibles of 0.05 day-1
or half-life of 14 days.
--Weathering elimination rate for plant leaves of 0.05
day-1 or 14-day half-life.
--F, Fraction of fallout intercepted by plant leaves of
0.25.
The weathering elimination rate (Aw) was estimated to be
0.05 day-1 based on a Tw of 14 days. The fraction of fallout
intercepted by plant leaves was 0.25. For most fission products
the fraction in the plant edibles which comes from leaf contami-
nation was estimated to be 0.001. The fraction in plant edibles
which comes from the root uptake of contaminants in soil was 1.0.
These values are estimates influenced by natural weathering
conditions and decontamination due to washing and food prepara-
tion.
Bloom et al. (1974) review the literature values to obtain
parameters for use in their transport model. Based on fission
product fallout data, they postulate the following half-lives:
Half-Life Time Increment
(Days) (Days)
1.4 0-5
20 5 -15
30 15 -30
130 30 -60
Bloom et al. (1974) note that such parameters as inter-
ception, retention, and retention half-life are dependent on the
time after deposition when these factors are measured. Given
this, they select an interception factor (units of cm2/g dry
weight) of 5 and a weathering half-life of 30 days. This
interception factor (in units of cm2/g) is equivalent to the
unit-less interception factor (F) divided by the plant biomass
10
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(W) in g/cm2. Bloom et al. (1974) refer to the studies by Miller
and Lee (1966) of interception factors (cm2/g) for fallout from a
volcano eruption. Values of the interception factor vary by a
factor of two (from 47 to 96 cm2/g) between low and high (greater
than 90 percent) relative humidity. Miller and Lee (1966) note
that these values were based on samples collected immediately
after deposition. Notation of time after deposition may explain
the discrepencies with nuclear fallout data reported by Martin
(1965). Martin (1965) reported values from 1.9 to 11.1, with an
average of 3.7 cm2/g. For relative comparison purposes, Bloom's
et al. (1974) .factor of 5 cm2/g can be converted to the unit-less
factor by assuming a biomass of 289 g/m2 (Martin et al. (1974)),
resulting in an F value of 0.14.
Martin et al. (1974) uses parameters similar to those of
Bloom et al. (1974). Several of the recommended parameters are:
interception factor of 5 cm2/g; weathering half-life of 30 days
(based on nonvolatile particulates on shrubs); and a desert plant
dilution growth rate of 36 g(dry)/m2-year. A biomass value of
289 g/m2 is referenced (Bamberg (1973)).
11
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RADIONUCLIDE UPTAKE FROM SOIL BY PLANTS
The uptake of radioactive material from soil by plants is
generally expressed as a discrimination factor pCi/g (dry weight)
of plant per pCi/g (dry weight) of soil. Variations of this
parameter include the discrimination factor between soil and the
roots or the edible fruits of the plant. The discrimination
factor is also given for uptake from hydroponic solutions. Table
2 summarizes the plant uptake of plutonium studies discussed
below.
The depth basis of the soil concentration presents an
inherent uncertainty in the discrimination factor. The majority
of fallout plutonium is normally found in the top two-to-five cm
of soil. Thus a 10-cm depth soil sample will only contain
essentially one-half the concentration of plutonium as a 5-cm
depth sample (i.e., the 10-cm sample is diluted with uncontamina-
ted dirt). It appears that most discrimination factors are based
on a 5-cm depth soil sample.
Several investigators have indicated an increase in the
discrimination factor with time (Romney et al. (1970); Price
(1973); Francis (1973)). The extent of and reasons for this
increase are uncertain. It is generally related to either the
chronological increase in depth penetration of plutonium in soil
and/or the increased availability of plutonium with time.
The increased penetration is related to alternate freezing -
thawing, and wetting - drying of the soil; earthworm activity;
agriculture practices; possibly changing plutonium
solubilization; and physical translocation downward through the
soil by the root hair system of plants (Wildung and Garland
(1974)). WHdung and Garland (1974) noted that plutonium from
surface soil was translocated down to the roots of barley. This
may have special health pathway implications for root crops
directly consumed by man.
Chronological increases in the bio-availability of plutonium
are related to the natural chelation of plutonium by decaying
roots (Romney et al. (1970)). Au (1974) and Au and Becker (1975)
indicate significant uptake of Pu02 by soil microorganisms,
specifically Aspergillus niger. Their experiments, conducted at
several values of soil acidity, indicate that microorganisms may
chronologically increase the bio-availability of Pu02 micro-
spheres.
12
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TABLE 2. SUMMARY OF PLANT UPTAKE OF PLUTONIUM
Reference
Discrimination Factor
(pCi/g dry plant: Time of
pCi/g dry soil) Measurement (Yrs)
Type Plant
Comments
Romney et al. (1970)
H
n
H
n
1.
4.
4.
7.
14
9x10"
1x10-
4x10"
1x10"
x 10"
s
5
5
5
5
1
2
3
4
5
Ladino
n
ii
n
i*
Clover
n
M
n
H
Pu-239
n
n
n
n
from
n
M
n
n
NTS
n
it
n
n
SOI
II
II
II
II
1
Garland et al. (1974)
Johnson et al. (1972)
Jacobson & Overstreet (1948)
Cline (1967)
Cline (1967)
II
Cline (1967)
Neubold (1963)
Nishita et al. (1965)
Rediske et al. (1955)
4.4xlO"5 <1
15 x 10"5 <1
1 x 10"7 1/3
200 (roots)
0.8 to 4x10 3Aerial portion: root
2xlO"6to 10"3
Av 6.4x10""
10"" 1/365
2 x 10"5 1/365
4.5xlO"6 1/365
0.4 (roots)
0.25 (roots)
0.2 (roots)
Am-241 50xPu-239
0.003 for Am
2 x 10""
1 x 10""
Factor 4 increase 2
10""
9 x 10""
Barley Pu(N03)4 100 uCi/g in soil, toxic effects
Barley Pu(N03)4 10 uCi/g in soil
Barley seeds
Barley roots, activity may not have been taken up
Used Pu02
Pu(N03)4
Barley Pu022+
Barley Pu"+
Barley Pu3+
Barley Pu022+
Barley Pu"+
Barley Pu022+
Barley
Alkaline Ephrata fine sandy loam
Pu acid soil
Pu alkaline soil
Ryegrass Pu in acid soil
Ladino clover Pu Fallout
Barley Pu"+
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Earth (1975), Raabe (1973), Hakonson and Johnson (1973), and
Patterson et al. (1974) report data inferring that plutonium-238
is more soluble than plutonium-239, and possibly more bio-
logically available. Raabe et al. (1973) report that the
dissolution rate for plutonium-238 dioxide monodispersed par-
ticles in an in vitro laboratory system was nearly two orders of
magnitude greater than for plutonium-239. Hakonson and Johnson
(1973) report changes in the plutonium-238 to plutonium-239 ratio
for the Trinity Site, New Mexico. Twenty-three years after the
nuclear detonation, the plutonium isotopic ratios varied from
0.05 for soil, 0.10 for plants, to I'.O for mammals. Brown and
McFarlane (1975) are conducting experiments with several plant
species and soils to determine uptakes for plutonium-238 and
plutonium-239.
Hanson (1975) notes that the increased availability of
plutonium-238 may result from the chelating action resulting from
more intimate contact of plant roots with the plutonium particles
(plutonium-238 versus plutonium-239); transport of plutonium by
individual cells; or a combination of such mechanisms by which
plutonium-238 may be absorbed differently than plutonium-239.
The higher specific activity of plutonium-238 versus plutonium-
239 is also potentially related to possibly different isotopic
effects.
Data indicating differences in the transfer or isotopic
ratios for plutonium-238 and plutonium-239 should be critically
evaluated. Plutonium-236, which is often used as an analytical
tracer may contain plutonium-238 as a contaminant. This error
can be corrected by analyzing tracer blanks. Furthermore,
sources of purer plutonium-236 are now available. An additional
problem results from the similarity of the americium-241 and
plutonium-238 alpha energies, 5.49 and 5.50 MeV, respectively.
Incomplete separation of americium in sample processing or delays
in counting after sample processing (i.e., amercium-241 ingrowth
from plutonium-241) can result in erroneously high indications of
plutonium-238 content. Generally, these pitfalls are not
present, but their potential must be recognized.
Plant uptake of plutonium from soil has been reviewed by
Bloom et al. (1974), Hakonson (1975), Hanson (1975), Price
(1973), and Francis (1973). The general consensus is that
short-term uptake is minimal, but that increased chronological
uptake due to natural chelation and other mechanisms presents an
uncertain picture and some cause for concern.
Romney et al. (1970) studied the transfer of plutonium-239
from soil to plants for ladino clover. These crops were grown
under glasshouse conditions on contaminated soil for five years.
Total crop yields increased each year. The plant-to-soil
discrimination factor for the first year was 1.9xlO-5 pCi/g of
dry plant per pCi/g of dry soil. The factor increased to 14x10-5
for the fifth year, for a five year average of 6.3x10-5. The
14
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soil was a one-to-one mixture of Yolo soil and soil from Area 11
of the Nevada Test Site contained in 60-liter containers (filled
volume 50 liters), with a surface area of 0.12 m2. The soil was
uniformly contaminated with a plutonium-239 concentration of
1.62x10-5 dis/min-g. Romney et al. speculated that some of the
yearly increase in plutonium uptake was related to increased
development in the root system. They maintained the root system
provided more intimate contact of the roots with plutonium.
Additional studies showed increased plant uptake of plutonium
from soils where DTPA chelating agent was added.
Garland et al. (1974) report results for barley and soybean
plants grown in soils containing Pu(N03)4. The split-root
technique was used to study the uptake and distribution of
plutonium in the plant tissue. The distribution of plutonium was
determined in the tops and roots of soybeans (Glycine max) after
50 days of growth, and barley (Hordeim vulgare) after 27 days of
growth. Slight increases in the total plant uptake were related
to increasing the volume of soil in the test plots for both
above-ground and root tissues of barley. But the height of the
soil column appeared to be a more important variable. Since the
plutonium was uniformly mixed in the soil column, increased
uptake from a taller soil column probably relates to the
increased contact between roots and soil.
Garland's et al. (1974) experiments were conducted with
concentrations of 10 and 100 yCi/g of plutonium-239. But the
elevated concentration of 100 yCi/g did not result in a marked
increase in uptake versus the 10 yCi/g soil. The respective plant
uptakes (dry weight, 60°C for 24 hours) for barley were 4.4xlO-5
and 15.5x10-5. The plants in the 100 yCi/g soil showed toxicity
symptoms until the root systems were established in the nutrient
solution below the soil. Plants grown in the two concentrations
were indistinguishable at the time of harvest. If the observed
toxicity is concentration dependent, Garland et al. (1974)
indicate that the previously reported results of Wildung and
Garland (1974), indicating an inverse relationship between uptake
and soil concentration, may have been due to toxic effects on the
roots.
Garland et al. (1974) reported that the distribution of
plutonium activity in the plant roots of barley averaged 17.1
percent and 4.79 percent (percent of total plant activity) for
two different plutonium activity soils (0.05 and 10 yg plutonium
per yg soil). Therefore, the average root content was 10.95
percent, with the remaining plant activity in the above-ground
parts of the plant (outer sheath, leaf blades and new growth).
Both the barley and soybean plant studies indicated that
plutonium, once in the plant, was rather mobile, with leaf tissue
containing 5 to 10 times the plutonium activity of that in the
stem tissue. After 100 days of growth, the barley seed had an
activity corresponding to a concentration factor of less than
IxlO-7 of the soil content.
15
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Johnson et al. (1972) reported the results of an experiment
to test the active transport of plutonium by plant roots. Barley
plants were grown in a nutrient media containing soluble
239Pu(N03) i». The barley plant roots were removed at various time
intervals, washed and analyzed for plutonium-239 content. A
tentative concentration factor from solution to roots of approxi-
mately 200 was observed. Although the roots were washed after
removal from the nutrient media, it is possible that much of the
plutonium was only associated with exterior surface contamination
of the roots and was not assimilated by the roots.
Johnson et al. (1972) conducted another experiment where
barley plants were allowed to mature and the root and aerial
portions were removed and separately analyzed. The ratio or
fraction of the concentration of plutonium in the aerial portion
of the plants, as compared to the root portion of the plants,
ranged from O.SxlO-3 to 4xlO-3 (average of 2xlO-3)for plants
grown in Pu02 solutions. The ratio for plants grown in Pu(N03)1,
solutions ranged from 2x10-6 to 1x10-3, with an average of
6.4x10-**. These ratios are similar to those reported by Romney
et al. (1970). This indicates that either the plutonium was not
taken up into the roots, or there is a significant discrimination
factor preventing the transfer of plutonium from roots to the
above-ground parts of the plant.
Menzel (1965) reviewed the literature concerning the soil-
plant relationships of radionuclides. This review was limited to
experiments where the radioactivity was in a soluble form when
added to the soil and where radionuclide concentrations were low
enough so that there were no toxic effects. In summary, Menzel
classed plutonium in the bottom of the lowest category (that is,
less than 0.01 (ratio of dry weights of plant and soil acti-
vity)).
Francis (1973) reviewed the mobility of plutonium in soil
and its uptake by plants. The following items are based on
Francis1 review:
1. Jacobson and Overstreet (1948) studied the trans-
location of plutonium in barley (one of the original
plutonium plant uptake studies of barley plants in
calcium-bentonite clay suspensions). Over a 24-hour
period, the fractional translocations to leaves, were
10-" for Pu022+, 2xlO-5 for Pu"+, and 4.5xlO-6for
Pu**•*-. The respective values for the roots were 0.4,
0.25, and 0.2.
Rediske et al. (1955) noted the discrimination factor
(ratio of dry weight of aerial portion of plants to
soil) increased from 10-1* to 10-3, with pH changes
of 7 to 4.
16
-------
2. Wilson and Cline C1966) studied the uptake of
plutonium-239 by barley from three soils. The soils
were Ephrata fine sandy loam, a slightly alkaline soil;
Milville silt loam, a calcareous soil; and Cinabar silt
loam, a moderately acid forest soil. Plutonium uptake
from the acid soil was more than three times greater
than from the calcareous soil. A 0.1N nitric acid
solution removed 0.64 percent of the plutonium,
approximately one-thousand times more than that taken
up by barley. This shows that common soil extracting
methods do not provide a reliable indication of
potential plant uptake.
3. Cline (1967) reported that the uptake of americium-241
into foliar portions of barley was fifty times that of
plutonium-239. The barley was grown in Hoagland's
nutrient solution.
4. Unpublished work of Buckholz et al. does not show a
chronological increase in the discrimination factor for
alfalfa after four years of growth. The study was
conducted in a plutonium contaminated soil associated
with the 1966 Palomares Spain accident. This is at
variance with the results of Romney et al. (1970).
Price (1973) reviewed several studies concerning plant and
animal uptake of plutonium. The following studies were not
reported by Francis (1973) :
1. Nishita et al. (1965) studied the uptake of fallout
plutonium in ladino clover (Trifolium respens L.~). The
discrimination factor was 10-H(yCi/g plant per yCi/g
soil, probably dry weights).
2. Rediske et al. (1955) noted that Pu1** becomes associ-
ated with root surfaces exposed to culture solutions.
The quality of sorption to root surfaces is linear with
respect to concentration of the solution, whereas, the
leaf concentrations had a curvilinear relationship.
The uptake into shoot tissues of tumbleweed from
solution cultures was slightly less than for beans,
barley, or tomatoes. The discrimination factor for
barley was 9x10-**, based on the Neubauer test. This
was considered to be an overestimate for what would be
expected under field conditions.
3. Cummings and Bankert (1971) used culture pots for
plutonium-238 uptake studies for nine soils. The
results for plutonium-238 were lower than those for
cerium-144 and promethium-147. The fractional uptake
(total activity in plants divided by total soil
activity) for plutonium varied from 7 to 280x10-8.
17
-------
4. Cline (1967) reports discrimination factors of 0.003
for americium-241 from alkaline (Ephrata lime sandy
loam) and acid (Cinabar silt loam) soils. The
plutonium factors were 2x10-1* (acid soil) and 1x10-**
(alkaline soil).
5. Neubold (1963) reported that although plutonium uptake
by perennial ryegrass (Folium perenne L.) was low, it
did increase over a 2-year study span,"Tor several
different soils. There was a 4-fold increase for an
acid soil.
Price (1973) indicates the following ranking for decreasing
uptake by plants from soil: curium, americium, and plutonium.
Neptunium uptake probably resembles that of plutonium.
Hakonson (1975) reviewed pathways for plutonium into terres-
trial plants and animals. Several investigators have noted higher
plutonium concentrations in native grasses than for forbs,
shrubs, or trees (e.g., Hakonson and Johnson (1973) and
Whicker et al. (1973)). This may be related to the morphological
structures of the plants and their ability to intercept and
entrap airborne material. Russell (1966) has noted that the
heads of grains serve as an excellent trapping device for depos-
ited material. On the other hand, the physical structure of root
systems of grasses and their position within the soil/plutonium
profile may be favorable for root uptake of plutonium by grasses.
Bloom et al. (1974) present an environmental transport model
with associated parameters. A soil to plant discrimination
factor of 0.313 (pCi/g of dry vegetation per pCi/g of wet soil)
is recommended. This factor is based on the indications of
increases of plant uptake with time (e.g., Martin's et al.
(1974) estimates from data from Romney et al. (1974)). The
Romney et al. (1974) values are based on results from the Nevada
Test Site, 20 years after deposition. Martin et al. (1974)
further justified the value of 0.313 by estimating the uptake at
20 years from Romney's et al. (1970) data. In essence, Martin
et al. (1974) exponentially extrapolated Romney's et al. (1970)
5-year study to 20 years.
Romney et al. (1974 and 1975) emphasize that the high dis-
crimination factors are not solely related to root uptake,
rather, they are a result of deposition with limited root uptake.
Romney et al. (1975) estimate the root uptake to be 10-3 to
10-". Thus, it appears Bloom's et al. (1974) and Martin's
et al. (1974) assumptions are in error.
18
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COMBINATION OF DEPOSITION AND PLANT UPTAKE
Romney et al. (1974 and 1975) reports data on the total
plutonium and americium-241 concentrations in vegetation for
several areas of the Nevada Test Site. These data are compared
on a pCi/g (dry and ashed) basis to soil concentrations. The
vegetation results are based on a sample of foliage, and exclude
the root mat. Romney et al. (1975) estimated that for Area 13
only 1/1600 of the plutonium-239 inventory was in the vegetation.
The ratio of foliage to soil values averaged about 0.08, and most
of the values (several hundred) fell within 0.02 to 0.16.
Romney et al. (1974) reported values for the total amount of
plutonium-239 on foliage versus the soil concentration. The pre-
liminary results for vegetation were based on the ashed weight.
The average values (pCi/g ashed vegetation per pCi/g dry soil)
were 1.0, 1.7, and 5.1 for Atriplex canescens, Atriplex confer-
tifolia, and Eurotia lanata, respectively.The average value was
2.24. Romney's plant-to-soil ratios are apparently all based on
the plutonium concentration in the top 5 cm of soil.
Colorado State University (1973) reported data on the
plutonium-239 inventory for the Rocky Flats, Colorado, area. The
data is based on plant distributions from the Pawnee National
Grassland. The soil accounted for 99.464 percent of the
plutonium-239 in the top 2 cm of soil. Standing vegetation
accounted for 0.058 percent, litter for 0.180 percent, and roots
(surface to two cm depth) accounted for 0.298 percent of the
total activity on the test plot. Considering the litter as part
of the standing vegetation, the foliage would then account for
0.238 percent of the total activity, comparable to the root
content of 0.298 percent. The total plant content would be 0.536
percent.
Whicker et al. (1973) reported plutonium concentrations for
various terrestrial ecosystems in the Rocky Flats environs. In
the top 3 cm of soil, fifty-nine percent of the plutonium-239 was
found in the soil fraction of less than 0.5 cm in diameter.
Additionally, 39 percent of the soil activity was found to be
below the 3 cm depth. Two-tenths percent was associated with the
surface litter and detritus, 1.3 percent with roots, and 0.06
percent with standing vegetation. Considering the litter as part
of the standing vegetation, the foliage would then account for
0.26 percent of the total activity, compared to the root content
of 1.3 percent. The total plant content is 1.56 percent, corres-
ponding to a concentration factor of 0.0156, due to both
19
-------
deposition and soil uptake. The root, foliage, and soil data
from Whicker (1973) are summarized in Table 3.
TABLE 3. PLUTONIUM IN VEGETATION AND SOIL
(Whicker (1973))
Plant
Western
Wheatgrass
Cheatgrass
Prickly
lettuce
Salsify
Biomass
Dry Weight
(g/m2)
32
10
2
9
Average Cone.
In Roots
(dpm/g)
247
294
157
13
Average Cone.
In Standing
Plant (dpm/g)
30
112
13
13
Average
Standing Veget.
Cone:
Soil cone.*
0.00125
0.0467
0.00542
0.00542
0.0015±0.02
* Vegetation concentration in dpm/g divided by average soil concentration of
2397 dpm/g. Based on soil sample of 0 to 3 cm depth and particles less
than 5 mm. Dry Weights.
Schultz et al. (1974) report a proposed study of plant
uptake of plutonium and americium. The study will include
several soils and several chemical forms of the elements.
Results have not yet been published.
20
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REDISTRIBUTION OF ACTIVITY WITHIN PLANTS
There appears to be very little absorption and redistribution
of deposited plutonium within plants. There is, however, only a
limited amount of published information.
Russell (1965) reviewed several studies concerning inter-
ception and retention of airborne material. He concluded that
the absorption of deposited material was of limited importance
compared to the retention of activity on foliar surfaces.
Aarkrog (1975) studied the uptake of deposited fission
products on wheat and barley crops. Radionuclides such as
strontium-90, ruthenium-103, and cerium-144 were generally
immobile. Whereas, zinc-65, iron-55, cesium-137, cobalt-60, and
manganese-54 were more readily translocated to the seeds.
Levin et al. (1970) estimate that only 0.1 percent of the
radioactivity in plant edibles comes from the leaves (for rela-
tively immobile elements). Essentially all of the activity in
the plant edibles is related to root uptake. The parameters
listed in Appendix A (Levin et al. (1970)) are for the inter-
oceanic canal project and are assumed to relate to fruits, nuts,
etc., -- not to leafy edibles.
21
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Witherspoon, J. P. and F. G. Taylor, Jr. (1970). Interception
and retention of a simulated fallout by agricultural plants.
Health Physics. 19:493-499
27
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Appendix A
Parameters for Atlantic-Pacific
Interoceanic Canal Model
(LEVIN et al., 1970)
K>
00
Parameter
FA
S01
f43
f42
fr
Parameter Definition
Average fallout concentration on a
watershed, uCi/cm2
Initial specific activity of the
radionuclide in the fallout, vCl/g
element
Fraction of the element in plant
edibles which comes from leaves
(dimensionless)
Fraction of the element in plant
edibles which comes from the soil
(dimensionless)
Ratio of runoff water to total
Values Used
-
0.05 (P&C)(a)
0.001 (P&C)
1.0 (P&C)
0.001 (P&C)
0.9 (P&C)
Remarks
These values are classified and thus are
not available
These values are classified and thus are
not available
For mobile elements H, P, I, and C
For all other elements than H,P, 1, and C
For all elements except carbon
For carbon
Infiltration is 10 percent of rainfall
References
-
Martin (1969)
Martin (1969)
Kazmaier (1569)
Kazmaier (1969)
Charnell eC al (1969)
Ratio of the amount of radionuclide
dissolved in surface water to the
total amount present on the soil
surface (dimensionless)
Average rainfall rate, cm/day
Unit rain, cm
Dry biomass of plant edibles, g
dry weight/cm^
Fraction of water in plant edibles,
g water/ g fresh weight
4.0 x 10'5 (P&C)
0.3 (P&C)
0.636 cm/day (P)
0.596 cm/day (C)
2.5 cm (P&C)
0.054 g/cm2 (P&C)
0-70 g/g (P&C)
For all elements except hydrogen; calcu-
lated from reference data(b)
For hydrogen; calculated from reference
(fc)
Estimated from mass rainfall curves
Estimated from rainfall curves
Defined by reference^0)
Calculated from reference
Estimated average water content from
reference data
Charnell et al (1969)
Charnell et al (1969)
Charnell et al (1969)
Charnell et al (1969)
Charneil et al (1969)
Transeau (1926)
Uu Leung and
Flores (1961)
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Appendix A (continued)
Parameter
Parameter Definition
Values Used
Remarks
References
10
F
Q
Density of water, g/cm3
Biological elimination rate coefficient
of element from freshwater fish, day"1
Biological elimination rate coefficient
of element from animals, day*1
Biological elimination rate coefficient
of element from marine fish, day"1
Growth-rate coefficient for plant
edibles, day"1
d C.
Weathering elimination rate coefficient
from plant leaves, day'1
Fraction of fallout intercepted by
plant leaves (dimensionless)
Biomass of plant leaves, g dry weight/
cm2
Average fallout concentration on the
marine fallout area,
1.0 g/cm3 (P&C)
0.055 day'1 (P&C)
0.1 day"1 (P&C)
0.02 day"1 (P&C)
0.05 day"1 (P&C)
0.05 day"1 (P&C)
0.25 (P&C)
0.35 g/cm2 (P&C)
Total amount of radionuclide initially
present in the canal channel and rubble,
Ratio of the amount of radionuclide
dissolved in the canal water to the total
amount present in the canal channel and rubble
(dimensionless)
4.0 x UT3 (P&C)
Listed in reference
Geometric mean calculated from reference
data by method outlined by Bloom et al
(1970)
Geometric mean calculated from reference
data
Estimated from turnover rates for
anchoveta
Arithmetic mean calculated from reference
data by method outlined by Bloom et al
(1970)
Calculated from reference
Weast and Selvy (1967)
Templeton et al (1969)
Brungs (1967)
Boroughs et al (1956)
Polikarnpov (1966 a&b)
Kevern (1966)
Wiser and Nelson (.1964)
Friend et al (1965)
GolUy et al (1969)
Lowman et al (1970)
Malavolta et al (1962)
Transeau (1926)
Jacob and von Uexkull
(1963)
Martin (1965)
Highest value selected from reference Nishita et al (1965)
data(8) Middleton (1960)
/t_ v
Calculated from reference
Transeau (1926)
0.3 (P&C)
These values are classified and thus are
not available
These values are classified and thus are
not available
For all elements except hydrogen^*)
For hydrogen
Essington (1969)
Essington (1969)
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Appendix A (continued)
Parameter
Parameter Definition
Values Used
Remarks
References
Net flow rate of water through the
canal channel, cm3/day
Horizontal extent of the marine fall-
out field in the direction perpen-
dicular to the current, cm
Estimated from reference data
2.83 x 1014 cm3/day (P)
3.62 x 1011 cm3/day (C) Estimated from reference data
1.85 x 10^ cm (P-Pacific side) Estimated from reference
1.20 x 10? cm (P-Atlantic side) Estimated from reference
1.11 x 10' cm (C-Pacific side) Estimated from reference
Horizontal extent of the marine fall- 1.11 x 10 cm (P-Pacific side) Estimated from reference
our field in the direction parallel
to the current, cm
Turbulent diffusivity in the verti-
cal direction, cm^/day
7.4 x 10 cm (P-Atlantic side) Estimated from reference
9.26 x 106cm (C-Pacific side) Estimated from reference dataU)
1.0 x 106 cm2/day (P&C) Estimated from reference
(a) P designates value used for Panama (Route 17). C designates value used for Colombia (Route 25).
(b) The quantity F was calculated as follows:
Fw =
1
Harleman (1967)
Harleman (1967)
Ferber (1968)
Ferber (1968)
Ferber (1968)
Ferber (1968)
Ferber (1968)
Ferber (1968)
Pritchard et al (1966)
V Volume of water in the canal
channel, cm3
V Speed of ocean current, cm/day
2.52 x 10° cmj (P)
2.19 x 1015 cm3 (C)
1.0 x 106 cm/day (P)
3.0 x 106 cm/day (C)
Estimated from reference data
Estimated from reference data
Estimated from reference data^ '
Estimated from reference data^ '
Harleman (1967)
Harleman (1967)
Lowman et al (1970)
Lowman et al (1970)
where a is the fractional soil porosity, 0.3
and KJJ is the distribution coefficient of the rainwater between the soil surface and surface water, 1 for hydrogen, ind 1.0 x 104 for
all other elements.
(c) If the interflow layer has a thickness of 7.5 cm (Odum, 1967) and a porosity of 33 percent, then the amount of rain required to saturate
this interflow layer is the unit rain (2.5 cm).
-------
Footnotes for Appendix A (continued)
(d) The quantity W, was calculated as follows:
rdry weight plant edible-, rHo. plants -
M4 L plant J x L 2 J
cm
r216g plant edible i rl.Q x 104 plants 2.471 x 10"6 acres -
W4 " L plant J X L acre x 2 J
cm
(e) Reference data described the growth of tropical plants. Pineapple, sugar cane, rice, and bananas were some of the foodstuffs for which
growth rate data were reported. _ ,„,
(f) The quantity k was calculated as follows: k - -_• -
where T is the environmental half- life of a radionuclide on leaves.
T was assumed to equal to 14 days for all radionuclides on fallout-contaminated plants in humid regions.
(g) The relative percentage of fallout intercepted by plants in the environs at NTS (Nishita ec al, 1965), from 8 percent to 15 percent at the
Maralinga Test Site for close-in and far-out fallout, respectively, (Nishita et al 1965), and up to 25 percent retention near NTS
(Middle ton, 1960).
(h) The quantity W-j was calculated as follows:
w3
V
,dry weight plant leaves %
"~ (
140 g
plant
leaves.
,no. plants t
I A v 2
cm
,1.0 x 10 plants
acre
>
2.47 x 10"6
cm
acre^
(i) The quantity Fc was calculated for all elements except hydrogen as follows: F = 100 Fw .
(j) This quantity is dependent upon the orientation of the fallout patterns over the marine fallout area. As no fallout is expected over the
Atlantic side of Route 25, no values are listed for the Atlantic side of Route 25.
(k) This quantity is the value used for both the Atlantic and Pacific sides of Route 17.
(1) This quantity is the value used for the Pacific side of Route 17.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
1. REPORT ..
ORP-LV-
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Technical Note: Parameters for Estimating
the Uptake of Transuranic Elements by
Terrestrial Plants
5. REPORT DATE
March 1976
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
D. E. Bernhardt and G. G. Eadie
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Office of Radiation Programs--Las Vegas Facilit
P.O. Box 15027
Las Vegas, Nevada 8.9114
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
same as above
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
IS. SUPPLEMENTARY NOTES
16. ABSTRACT
This report summarizes information from the literature concerning
parameters which can be used to estimate the transport of transuranic
elements through plants to man. Plant uptake results from root uptake
and deposition of contamination on above-ground surface areas of the
plant. Deposition on plant surfaces occurs from both the initial con-
tamination cloud and resuspension of contaminated soil. Generally,
a deposition interceptor factor (pCi on vegetation per unit area sub-
tended by the vegetation, per pCi per unit area of ground) of about
0.2 is indicated. A weathering half-life of about 30 days for time
periods of about a week after deposition is3suggested. Plant uptake
parameters generally range from 10" to 10" ; however, some data has
been extrapolated to estimate a long-term uptake (20 years) of 0.3.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Plutonium Isotopes
Plutonium Plant
Pathway
Plant Uptake Parame-
ters
Deposition on Plants
1802
1802
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
36
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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