A REVIEW
   James C. McFarlane and Benjamin J.  Mason
          Radiological Research Program
   Southwestern Radiological Health Laboratory

U. S.  Department of Health, Education, and Welfare
               Public Health Service
           Environmental  Health Service
                     July 1970
    This study performed under a Memorandum of
           Understanding (No. SF 54 373)
                      for the

                         LEGAL NOTICE

This report was prepared as an account of Government sponsored
work.  Neither the United States,  nor the Atomic Energy Commission,
nor any person acting on behalf of the Commission:

A.  makes any warranty or representation, expressed or implied,
with respect to the accuracy,  completeness, or usefulness of the in-
formation contained in this report, or that the use  of any information,
apparatus, method,  or process disclosed in this report may not in-
fringe  privately owned rights; or

B.  assumes any liabilities with respect to the use of, or for damages
resulting from the use of any information, apparatus, method,  or pro-
cess disclosed in this report.

As used in the above, "person  acting on behalf of the Commission"
includes any employee or contractor of the Commission,  or employee
of such contractor, to the extent that such employee or contractor of
the  Commission, or employee  of such contractor prepares, dissemi-
nates,  or  provides access  to,  any information pursuant to his employ-
ment or contract with the Commission, or his employment with such

                     A REVIEW
     James C. McFarlane and Benjamin J. Mason
          Radiological  Research Program
   Southwestern Radiological Health Laboratory

U. S. Department of Health, Education, and Welfare
              Pub Iic Health Service
           Environmental  Health Service
       Environmental Control Administration
          Bureau of Radiological Health
                    July 1970
    This study performed under a Memorandum of
          Understanding (No.  SF 54 373)
                     for the

                          TABLE OF CONTENTS

LIST OF FIGURES                                                   ii
LIST OF TABLES                             .                      111
I.   INTRODUCTION                                                  1
II.  DEPOSITION                                                    4
     B.  HUMIDITY                                                 12
     C.  SPECIES                                                  14
         1.  Plant growth habit.                                  14
         2.  Leaf morphology.                                     20
III.  ABSORPTION OF IODINE BY PLANTS                              22
      A.  ROOTS                                                   22
      B.  LEAVES                                                  24
IV.  HALF-LIFE OF IODINE ON VEGETATION                 .           25
     A.  GROWTH                                                   25
     B.  ABSORBED IODINE LOSS                                     26
     C.  ADSORBED IODI.NE LOSS                                     26
V.   SUMMARY AND CONCLUSIONS                                      29
BIBLIOGRAPHY                                                      31
APPENDICES                                                        42

                           LIST OF FIGURES

Figure 1.  Physical Form of 131I in Air at Various
           Distances from the Source.                              11
Figure 2.  Air Movement in Alfalfa Field.                          15
Figure 3.  Percent Water in an Alfalfa Stand
           Between Irrigations,                                   18
Figure 4.  Decay of 131I2 from Contaminated
           Alfalfa Plants.                                        28

                            LIST OF TABLES

Table 1.  Important Radioisotopes of Iodine
          Produced by Fission.                                     5
Table 2.  Variation in the Percent Water of Four
          Plant Species on Three Different Collections.            18
Table 3.  Distribution of 131I in Bean Plants Growing in
          Na131I Contaminated Hoagland's Solution.                 26

                        I.  INTRODUCTION

The discovery of atomic fission brought with it many important health
problems.  'One of these is the possible contamination of air,  water,
food, and forage with radioactive iodine.   Since radioibdine may reach
man in many ways, it is difficult to discuss all routes  in one review.
This report, which is primarily a review of the literature, up to
January 1969, discusses only one intermediate in the passage-of
radioiodine from the source to man*s food—the plant.
The two objectives of this report are:
    1.  To bring together in one document a summary of plant-iodine
    2.  To provide data to aid in the design of experiments to broaden
        our present understanding of the contamination of plants with
It seems logical to start the consideration of the iodine problem
with a brief look at the possible sources of radioiodine.  Quantities
of radioiodine may be released to the environment in several ways.
Among the most important of these are nuclear explosions (both atmos-
pheric and cratering devices), nuclear reactor operations, and reactor
accidents.  Under certain conditions, especially in nuclear facilities,
chronic contamination may exist.  In 1959, the National  Committee on
Radiation Protection (NCRPr84^ suggested that 9 .X 10"9  yCi/cc of air
was the maximum permissible concentration (MPC) of 131I  allowable in
a nuclear facility.  Although this level is very important in  con-
nection with industrial operations, it is generally of no direct
consequence to the public.
Most releases of radioibdine to the environment are of short duration
lasting from a few minutes to a few days.   Under these conditions one

critical pathway of radioibdine is the air-forage-cow-mi Ik-man route/  '
In 1964, the Federal Radiation Council (FRC) ^  ' recognized the thyroid
as the critical organ for the radionuclides of iodine.  Since milk is
one of the main vectors of radioidoine to the thyroid the FRC recommended
that children be considered the critical segment of the population.
The concern with milk as a route of 131-iodine to man is based on the
70 kg (fresh weight) of green alfalfa or grass per day,  Radioiodine
is therefore important, not because of the amount deposited on the
vegetation but rather because of the efficient passage of radioiodine
through this food chain and its ultimate concentration in a child's
Although milk is considered as the main source of contamination, other
sources should be investigated.  The following examples may best
illustrate the relationship of contamination by milk versus contami-^
nation from leafy vegetables.  During a period of atmospheric testing
(1962), contamination in the milkshed of Salt Lake City was from
300 to 2000 pCi/liter.  At the same time the concentration of leafy
lettuce reached 2800 pCi/kg fresh weight^  .  To receive the same
amount of activity as that received from one liter of milk, consump-
tion of approximately 700 grams of leafy lettuce (not head lettuce)
would have been required.  A large dinner salad contains approximately
100 grams of lettuce.  Since it is more probable that a person would
drink one liter of milk each day than eat seven large dinner salads,
milk is clearly a more important source of radioiodine contamination.
However, it is clear that green vegetables may become contaminated and,
therefore, cannot be neglected as a contributing source to man's total
radionuclide intake. ,Thompson    .  suggested that as much as
20 to 40 percent of the possible  131I contamination may be attributed
to products other than milk in some non-urban adult population.
The same principles of plant contamination still exist, whether plants
are eaten by man or by a cow.  There will certainly be differences in

the quantity of plant material consumed and the method of food prepa-
ration, but the physiological and morphological principles which
control the uptake and retention of iodine by plants will apply in
both food crops and forage plants.  The overall objective in studying
plant-iodine relationships is to allow predictions of possible
human ingestion of 131I.  Two main questions are of concern in this
    .1.  What is the rate of deposition?
        (To describe deposition, it is necessary to understand
        differences caused by species variation, environment,
        and the form of contamination.  To evaluate this, plant
        morphological and physiological factors which control
        the rate of deposition on and movement into the various
        parts of plants must be understood.)
    2.  How long does the contamination remain?
        (Variations caused by the chemical and physical states of
        fallout and also the effect of various environmental
        parameters such as wind, rain, temperature, and humidity
        on the loss of iodine from plants must be evaluated,
        Differences caused by plant morphology and physiological
        parameters such as foliar absorption and translocation
        must be considered in order to completely evaluate the
        radioiodine-plant relationship.  To be able to predict
        the transfer rates of iodine to cows, it is necessary to
        have some insight as to the chemcial .changes in the form
        of the iodine which occurs in or on plant surfaces.)

                           II.  DEPOSITION

The kinetics of iodine deposition on plants was first studied by
Chamberlain and Chadwick in 1953^  '.  In their research they
recognized the need to express the amount of plant contamination
in relationship to the radioactive cloud.  The term they defined (V )
was simply a ratio between the amount of activity deposited on a
horizontal surface per unit of time to the amount of activity in
a volume of contaminating air.
               „   .   .   .   deposited activity/cm -sec
               Vg  (cm/sec) =    activity/cm' of air	
The area of deposition in this equation is considered to be that area
of ground which may be completely or partially covered by vegetation.
The resulting units were the same as velocity (distance/time); there-
fore, the term was originally called "velocity of deposition."  Since
that time, the term deposition velocity has been used by many investi-
gators to describe the contamination of plants by iodine.  This
generalized equation is, however, useful  only to the extent that the
parameters which control the transfer of iodine from air to a surface
are understood.
The transfer of radioactive fallout from the air to the surface of
plants and soils is a complex phenomenon.  Although this phenomenon
is not well understood, it can best be studied by dividing it into
two fields on interest.  The first is the study of the contaminant
from the time it is produced until it reaches the location of deposi-
tion.  This area of study involves the fields of aerosol physics,
meteorology, and microclimatblogy.  The second area of interest 1s the
study of those plant factors which have a modifying effect on the
environment and thereby influence the rate of deposition.  An investi-
gation of these factors involves the study of plant morphology and

A.  Physics and Chemistry of Iodine Fallout.
    To understand iodine contamination of plants, it is important to
    first understand something about the manner in.which iodine is
    released and how it reacts in the atmosphere.  All  methods of iodine
    release to the atmosphere involve high temperatures (in nuclear
    detonations) or powerful solvents (in reactor fuel  reprocessing)
    and result in the evolution of isotopes of iodine as gasest43.
    Although the fission process produces some 131-iodine directly,
    the majority of the 131-iodine is derived from the precursors,
    131-antimony and 131-telluriunr '.  When fission products are
    released to the atmosphere, the ingrowth of 131-iodine into the
    cloud is rapid because the two precursors mentioned above have
half-lives of only 23- and 25- minutes respectively^  .   Other
isotopes of iodine are also produced in the fission chain'
An inspection of Table 1 shows that 132I through 135I are produced
in greater quantities than 131I.  A look at the half-lives
quickly shows why they are generally thought to be of secondary
importance in the contamination of milk.  Iodine-133 with a half-
life of nearly one day, is present in such large amounts that it
cannot be overlooked as a possible health hazard.  However, most
attention has been given to 131I since its half-life is longer
and, after a short time, it is the main isotope of iodine found
in fal]out.
Table |.  Important Radioisotopes of Iodine Produced by Fission.

 Nuclide                     Half-life           Fission Yield (%)
  131I                        8.05 days                2.9
  132I                        2.26 hours               4.4
  133I                       20.9 hours                6,5
  13l*I                          54 minutes             8.0
  issi	6.75 hours	6J	.
*Adapted from Bolles and Ballou, 1956;(7) Radiological Health Hand-
book, 1960 (30),

Hhen a nuclear cratering device is exploded, a cloud is created which
includes fission products, activation'products, and part of the inert
material surrounding the detonation site,  Partiiculate fallout is largely
the result of the attachment of radioactive hue!ides to small particles
of the inert or carrier material.  The attachment of any particular nuclide
is determined by physical and chemical properties of both the particle
and the contaminant.  Shleien     suggested that attachment of nuclides
to particles of different sizes may vary with respect to the half-lives
of their parents.  To visualize this it is necessary to consider two
    1.  Size fractionation (the size distribution of fallout particles
        diminishes as the time or distance from the detonation increases).
    2.  Radioactive decay (nuclides with short-lived precursors have
        a faster ingrowth rate than those having long-lived precursors).
These factors combined with the differences in the half-life of the
various radioisotopes of iodine (see Table 1) had an effect upon the
ratios of  133I to 131I in the fallout from a test conducted at the
Nevada Test Site.
In April 1966, the Atomic Energy Commission's (AEC) Project Pin Stripe
accidentally released a small amount of contamination from an under-
ground test.  An experiment (unpublished) conducted by this laboratory
showed that the ratio of 133T to 131I deposited on plants decreased as
the distance from the hot line Increased.  Since the half-lives of the
precursors of 133I are much shorter than those of 131I, it is under-
standable that the former was more plentiful in the region close to the
cloud center.
Radioactive fallout consists of a complex mixture of radioactive gases
and various sized particles.  The meteorological parameters that control
mixing, movement, and dispersion of a fallout-cloud determine when and
to what rate portions of th.e cloud reach the surface of the earth.  At
the surface, micrometeorological factors control the deposition of the
radioactive contamination.  The physics of the actual removal and retention
process of small particles and gases is complex and therefore not well

In 1966, Fisher^  ' reviewed the subjects of deposition of iodine vapors
and cQntam.inaitid aerosols on plants.  Hi suggested that the
atrodynamle factors whleh control deposition of both aerosols and vapors
at the air-ground interface are gravity, electrical forces.thermal
forces, Brownian motion* molecular diffusion-, and turbulence.  Describ-
ing the deposition of particles, Chamberlain^  ' considered the primary
transport mechanism in the turbulent boundary layer to be eddy diffusion
with molecular diffusion being effective over the last few millimeters.
Outside the boundary layer the particles are subject to the well known
Stokes' relation for terminal velocity and as a result possess a
constant downward velocity.  Considering the various parameters,
       / 00\
Fisherv  ' developed a model for the deposition of vapors and aerosols
on leaves.  Using this model,, he compared some of the reported values
to the theoretical predictions.  He found that he was only accurate
to within a factor of two for aerosols and a factor of three for vapors.
His model holds that increased wind speed causes a corresponding
increase in the deposition velocity and that an increase in particle
size from 0 to 20 ym causes an increase in deposition velocity from
0.25 to 3.0.
The difference between the observed deposition velocity and that
predicted by Fisher may possibly be explained by understanding more
about the morphology and physiology of the plant surface.  The velocity
of deposition and retention of particles on leaf surfaces is largely
dependent on the thickness of the boundary layer of air at the surface
            (3 17 22}
of the plantv '  *  '.  The thickness of this boundary layer is
influenced both by physical factors and plant factors,  Hhere the
boundary layer is thin, contaminants are deposited in greater abundance.
This could explain why iodine is often concentrated at the margins of
       (20 54}
1 eavesv  '  '.  High velocity wind reduces the boundary layer to a
very thin film next to the leaf surface.  In contrast, low velocity
winds allow the boundary layer to thicken.  The morphology of the leaf
surface also determines the shape and extent of the boundary layer,
Epidermal hairs act the same as a windbreak in reducing wind speed
close to the surface.  This reduction in speed causes the boundary
layer to thicken, i.e., a leaf which is covered with epidermal

hairs has a thicker boundary layer than a smooth leaf.   Thus, by
modifying the boundary layer, variations in morphology can be
responsible for variations in retention of airborne nuclides.  The
physiology of the plant effects the boundary layer by changing the
rate of gaseous exchange, by changing the relative humidity adjacent
to the leaf surface, and by positioning the leaf in different
attitudes with relationship to the environment.
The rate of settling the deposition of iodine depends on the physical
form of the contaminationv  '.  One of the limiting factors in our
understanding of the physical form of the deposition is the difficulty
incurred in sampling the atmosphere in a•meaningful way.
Particulate contaminants are generally classified by one of three
methods:  graded filter.casade impactor, or photographic methods,
Two types of filter systems are used for sizing particles.  One type
uses filters with several different pore sizes placed in series.
Microfilters are very efficient for this type of determination since
they are essentially 100 percent efficient for particles larger than
their pore size.  They are available in ten porosity grades from
0.01 to 5 ynr   .  Another system uses only one type filter and
measures the depth to which various sized particles penetrate into
this filter.  Silverman^   ' used a polyester filter to collect and
classify particles from 0.002 to 0.35 ym diameter.  One limitation
of both of these systems is the fact that the filter characteristics
change with time because of the particles which are collected on or
in the filter material.  A particle may only partially cover a pore;
therefore, limiting the size of the particle which will pass through
that pore.  Especially when the air has a high dust load, the
efficiency of the filter changes and thus particle sizing becomes
less accurate as the operation progresses.
Inertial particle or cascade collectors make use of the fact that
particles moving in  anairstream tend to follow along their original
direction when the airstream is deflected by an obstacle.  Impactors
collect the particle on the surface of the deflector.  Impingers use


the same principle but collect the particle in a liquid.   By having
a series of impactors with a different airspeed at each step in the
sampler, particles of different sizes will be collected,   Cascade
impactors are generally not efficient for parttcles less  than 1 ym.
The final method of measuring fallout particles is via microscopic
measurement.  Particles for these measurements are often  collected
on planar surfaces and sized visually by the aid of a photograph taken
through the use of either a light or an electron microscope.  Although
this is a very time-consuming and laborious task, there is one advantage
in this method over the previous two.  In deposition studies we are
interested in the distribution of deposited or settled particles rather
than the total in the air sample.  Since a planar collector resembles
the surface of a plant more than a higfuvoliime air sample, the ratio
of various~sized particles-on such a plate would be more  representa-
tive of the distribution on a plant surface.  (A plant is not, however,
simply a planar surface, therefore, some difficulties arise in inter-
preting this type of information.)
Detection of iodine gas is equally as difficult as detection of the
particulate materials and there is, perhaps, even more possibility of
error in this determination.  The most commonly used method of classi-
fying fallout into its two major fractions (particulate vs gas) is
done by collecting the particles on an inert prefilter and the gases,
which pass the prefilter, on activated charcoal.
Since activated charcoal is nearly 100 percent efficient  for the col-
lection of most of the gaseous iodines, the resolution of this system
is largely dependent upon the efficiency of the prefilter for removing
the particulate material from the air sampled.  Small particles are
perhaps the biggest source of error in this system.  To have a system
which collects  all submicroiTsized particles on the prefilter generally
                     i       •               ' •            ...
requires some type of graded filter system.  Without this there is a
good possibility that much of the activity seen on the charcoal filter
is in reality very small particles rather than gaseous iodine,
Other possible sources of error are related to the adsorption of gaseous
iodine onto the prefilter and also to the possible revolatilization of

some of the iodine from the charcoal during the period of time between
sampling and the time the filter is collected.
Kuhn^63' gives information on methods for analyzing air for very small
Keeping the above limitations of collection systems in mind, the follow-
ing material will examine the data in which particulate and gaseous
iodine has been investigated.
Eggleton, et al. ,  ' classified world-wide fallout from the Russian
atmospheric testing of 1961.  This study, which used filters to size
the fallout, covered a three-month period following the tests.  As
a prefilter they used a high-efficiency asbestos filter followed by
brass gauze for elemental iodine and charcoal-impregnated filter paper
for removal of certain other compounds of iodine.  This filter system
was backed by a one-inch bed of activated charcoal.  These authors
found that an average of 75 percent of the 131I contamination was in
particulate form.
Megaw^  ' contaminated the inside of a reactor shell with radioiodine
in order to study simulated conditions of a reactor rupture.  He found
that from 40 to 80 percent of the iodine released had become attached
to particulate material within the first hour.  A large amount had also
become attached to the containment vessel walls.  Much of the particulate
iodine can be accounted for by very small particles called Aitken
nuclei^  '.  These are particles of about 10 nanometers in diameter
which are formed in all combustion processes and are therefore generally
present in air.,  Aitken nuclei are so small that they are sometimes
thought to move in a manner similar to gases.  Even though this may be
partly true, there are some differences which should be recognized.
Under the  influence of gravity the Aitken nuclei has a settling velocity
which is different from that of a gas.  The important difference is the
fact that the Aitken nuclei consolidate to form larger particles as
they are carried from the point of release.  These particles and their
aggregates therefore do not respond to changes in meteorological
conditions in the same manner as a gas.

The studies of Perkins' nave $hown that a large and varying fraction

(from 10 to 90 percent) of the radioiodine in fallout is in the gaseous
form.  He tried to characterize the chemical form of the gaseous iodine

and found that very little, if any, exists in. the elemental or HI form.
However, the gaseous compounds of 131I in air were not identified.  Up
to 20 miles, there was an increase in the amount of particulate iodine

contamination in a cloud with increased distance from the release
(Figure 1).






10 J
                     5  10  15   20  25 30

                      Distance from source

Figure 1.  Physical Form of  131I in Air at Various Distances
           from the Source ^0).

Nishita^ has stated:
     "The chemical and physical properties of fallout depend on
     the energy yield of the nuclear device, the degree of inter-
     section of the fireball with the ground surface, the mineral
     composition of the ground surface, and the structural
     material surrounding the device.  Nuclear devices detonated
     on or near the surface of the ground have been found to
     yield predominantly siliceous fallout particles because
     of the incorporation of soil into the fireball.  Particles
     from detonations at higher elevation more nearly reflect
     the incorporation of the structural materials surrounding
     the device.  A large fraction (>50%) of the close-in fall-
     out from nuclear devices detonated on steel towers at.the
     Nevada Test Site was attracted to magnets and was red-
     brown in color suggesting the formation of magnetite.  By
     comparison, the devices that were not detonated on steel
     towers produced fewer magnetic particles (<10%).  Devices

         fired at the Pacific Proving  Ground  produced  fluffy  conglom*
         erates of CaCOs from coral and  crystalline  NaCl  particles
         from sea water,   Thus,  the chemical  composition  of fallout
         may vary considerably depending upon the  conditions  of
    It seems obvious that the ratio of gaseous to  particulate contamina-
    tion and the size distribution  of  particles  is dependent  on  the
    amount of particulate material  in  the cloud  and  the distance or
    time from release.   Shlelerr99' found that  airborne  fresh fission
    material occurred on larger particles and that the size of the
    contaminated particles decreased with time.  Most  of  the  older
    fission products were associated with particles  having diameters
    less than about 1.75 ym.
B.  Humidity.
    Humidity has been recognized as a  factor  which influences deposi-
    tion of iodine*   .   Cline and  Hungate*  ' observed that  moist
    leaves of a plant species accumulated up  to  2.2  times as  much
    i3i!2 as did dry leaves of equal area. The  same was  true with
    moist paper but there was only  a very slight increase in  accumula-
    tion noted for moist soil.  Barry  and Chamberlain     offered two
    possible explanations to account1for these observations.   "It may  be
    that humidity was responsible for  regulating the size of  the stomatal
    aperture.  Alternately, adsorption of iodine on  the external
    surface of the leaf may have been  in some way  facilitated by
    Conditions of high humidity."
    Let us consider transpiration,  not because of  any  suspected  rela-
    tionship with iodine diffusion, but  rather because it might  give
    us some information  on which to form a hypothesis. The rate of
    transpiration through open stomates  is regulated by the gradient
    between the vapor pressures  of  water inside  and  outside of a leaf.
    In the substomatal cavity the humidity remains very close to
    saturation.  The vapor pressure gradient  is  therefore determined
    by the temperature of both leaf and  air and  the  relative  humidity
    of the air.  When the gradient  decreases, the  rate of transpiration
    also decreases until  at 100  percent  relative humidity (RH)
    transpiration stops.

One would intuitively think that transpiration would also be
greatly influenced by the degree of stomate opening.  This is,
however, not the case.  Diffusion through the stomate is not
correlated to the area of the individual stomate but to the
circumference of the opening1   .  This means that small changes
in the amount of opening and closing are of little importance
in restricting diffusion.
With this in mind, let us consider how humidity might alter the
diffusion rate.  Atmospheric humidity does not directly affect
the degree of stomatal opening.  Under high atmospheric humidity
the gradient of pressure potentials between the atmosphere and
the substomatal cavity is decreased and the rate of transpiration
would therefore be suppressed.  This would cause a decrease in
the rate of water loss and could, under conditions of water
deficits, cause a decrease in plant water stress.  Under such
conditions greater tugor would result in the guard cells and
the stomatal aperture would open larger.  This effect would
only occur under special conditions and would not be a general
response to increased atmospheric humidity.  In addition to this,
it is not logical to presume that humidity may change the con-
centration of iodine in the air.  A more probable explanation
would be related to the chemical properties of iodine in a humid
environment and the physics of deposition and retention of particles
and vapors on a moist surface.
The importance of humidity in the deposition of iodine on plant
surfaces is still undefined.  There is no data available which
would allow a statistical evaluation of the effect of various
amounts of atmospheric moisture upon deposition.  The effect of
humidity on retention and absorption of foliar-applied iodine is
likewise not understood.  Since humidity has been documented as
one of the important factors in determining the rate of contamina-
tion, attention should be give to quantitating this effect.

The bas.is of plant classification'is the anatomy of the flower.
There are other differences, however, which are of greater con-
sequence in the contamination of plants by radioiodine.  Each
species of plant can also be characterized by leaf differences
such as size, shape, surface, number of leaves, and their orienta-
tion on the stem.  Plant leaves are special organs which function
mainly to absorp radiant energy and exchange gases with the
environment.  Both of these functions require leaves to present
a considerable surface to the atmosphere.  Herein lies the key
to the importance of plants in the passage of iodine to man.
Because of their large area and ability to exchange gases, leaves
are efficient collectors of radioactive fallout.  Let us there-
fore consider some of the differences in leaves as they relate
to the collection of radioiodine.
    1.  Plant growth habit.
        The fact that species differ in their collection ability
        for radionuclides is exemplified by the data of Gorhanr^
        and Davisv   .  These authors, working with 90Sr from
        fallout, showed that mosses and lichens accumulate far
        more of this radionuclide than do vascular plants.  This
        difference was considered to result from the differences
        in the growth habit of these plants.  Similar results
        can be expected with other radionuclides.
        Preliminary data obtained at this laboratory indicate that
        131-iodine from fallout is retained differently by
        different species of plants.  A dense stand of alfalfa
        retains more iodine than a more open stand of sudan grass.
        This again is considered to be a result of both growth
        habit and leaf morphology.

Natural desert vegetation such  as  sagebrush tends to have an open (less
leaf area per unit of space occupied  by  the plant) character, thus the
air is free to move through the plant and expose more of the leaf
surface area to the contaminant than  would be encountered in a dense
plant such as alfalfa.
An alfalfa field has only the top  few inches of the plants situated
in an area of great air movement.   The lower leaves are mostly
protected from wind and air movement.  Figure 2 shows the profile
of air movement in a stand of alfalfa growing on a research farm
managed by the Southwestern Radio!ogical Health Laboratory for the
U. S. Atomic Energy Commission. *   '   It is  obvious  that  the  lower
leaves are in a different environment, therefore, have a different
exposure to contamination than the upper leaves.
                        1  [      I   I   '   !  L-H
                                 I   I  TXT     I
                     0 10 20 30 40 50  60  70  80 90  100
                               Height  (cm)
Figure 2.  Air Movement in Alfalfa Field.

Cline, Wilson, and Hungate^  .' observed thait rye plants collected
gaseous iodtnemostly in the middle portion of the plant,  The top
collected 39 percent, the middle 49 percent, and the bottom 18 percent,
They also observed that tnts resulted from the seed heads causing the
tops of the plants to hang down so that the middle of the stem was
actually the highest and most exposed portion.  Barry and Chamberlain
observed that the smaller leaves at the top of the stem were often
associated with higher absorption than the lower leaves.  Bunchv  '
reported greater absorption of iodine on the upper parts of grass leaves.
From the above observations, it seems apparent that the amount of con-
tact with the contaminated air appears to be greatest at the top of
a plant and that this is the area of greatest contamination.
An important point to remember fn evaluating contamination of plants
by radioactive fallout (particularly iodine) is the method of
expression.  Since the leaf is the plant part in greatest contact
with the environment, it is the plant organ on which deposition is
ultimately dependent.  The number, size, and type of leaves presented
to a radioactive cloud are therefore the most important plant
factors in) determining the rate of accumulation or deposition.
Under laboratory conditions, Bunchv  ' showed that the deposition
velocity rises logarithmically with an increase in the density of
vegetation.  Gifford^  ' showed that vegetation, specifically sage-
brush and grass, collected more contamination per area of ground
cover than either bare soil or flat plate collectors.  Cline^  '
observed the deposition velocity on bare soil and found it to be
approximately half that found on living plants.  Plant cover presents
a larger collection area than a bare soil or a planar fallout
collector.  This difference could account for the difference in
observed deposition velocities between plants and soils.  By
reexamining the equation commonly used for deposition velocity, we
find that it is based upon the ground surface area.   The observations
cited above make it obvious that the rate of deposition on plants
should be based in some way upon the effecttve collection area of
the particular plant involved.  The leaf area of a plant is a


difficult parameter to obtain.  The effective collection area (includes
all epidermal surfaces of the leaf and stem, all protrusions, the
effective gas exchange area created by the stomates, and all surfaces
of bark and other dry material on the plant) is even more difficult to
measure than leaf area.  There must be, between the ultimate and the
obvious, some parameter which will allow us to gain a better under-
standing of the deposition of radioactivity upon plants.
Some authors have based contamination data on the fresh weight of the
sample.  It has been found in this laboratory that the fresh weight
of forage samples can vary as much as ten percent due to the time
between the collection and the weighing of the sample.  Placing the
samples in sealed plastic bags can certainly reduce the loss of moisture
but cannot eliminate it.
Other sources of variation in the moisture content of vegetation are
the time since the last irrigation or rainfall and the relative humidity
of the air.  Figure 3 shows the change in the percent moisture of an
alfalfa field between periods of irrigation.  If the loss of contamina-
tion from alfalfa were studied using for a basis of expression the fresh
weight of alfalfajan erroneous interpretation of the data could easily
result.  Also comparison between species can be confounded by differences
in their moisture percentages.  Table 2 shows the variation of the
moisture content of four species collected at the same site at the same
In order to overcome the above mentioned difficulties resulting from
the use of fresh weight measurements or those resulting from the use
of ground surface area, some authors have used the sample dry weight
as the basis for expressing vegetation contamination data.  This method
has the advantages of 1) reflecting the amount of material and 2) avoid-
ing the problems of moisture variation associated with fresh weight

The method used by this laboratory^   ' is to keep the sample in a sealed
plastic bag from collection until weighing.  If the sample cannot be
weighed immediately it is kept in an ice chest or refrigerator until


Table 2.  Variation in the Percent Water of Four Plant Species on Three
          Different Collections.(122)
27 March
22 April
4 June
Arar .
55.3 ± 4.1
62.0 ± 2.0
53.0 ± 2.0
Percent Water *
Epne"*" Orhy*
48.5 ± 5.0 16,0 ± 2.6
49,7 ± 1.5 41.7 ± 7,6
44.3 ± 1.1 51.7 ± 2.1
59.0 ± 5.2
63.3 ± 4.6
54.6 ± 1,6
* = Artemisia arbuscula  (black sagebrush)
J = Ephedra nevadensis (Mormon tea)
* = Orhyzopsis hymenoides (Indian rice grass)
  = Sitanion hystrix (squirrel tail grass)
cu  80..Irrigation
the time of weighing.  After weighing, the samples are counted then
returned to the principal investigator who is responsible for drying
the sample to a constant weight and reweighing the sample.   (It has
been found that drying at 75°C for 24 hours or longer will  provide
this condition.)
The two main disadvantages of the dry weight method are the
increased costs due to extra handling and failure of this method
to account for the dilution of the activity resulting from plant
growth during the time of an experiment or study.
At this time, basing data on a dry weight basis appears to be the
best available method.  The ideal however would be to have a
rapid means of measuring the actual surface area of the plant that
is exposed to the contamination:  Efforts are underway in this
laboratory to try to develop a suitable method to determine such
a measurement.
Also, It must be remembered that plants change in response to
climatic variation; therefore, the crown density, leaf morphology,
and physiology will not always remain constant.  Crown density, for
instance, may be much different on plants of the same species at
different locations, at different times of the year, or at different
periods of development.  Leaf morphology may change at different
sites or different seasons; i.e., some leaves shed epidermal hairs
or cur] in response to drought.  Likewise in an area of ample
moisture, leaves are generally larger and more succulent than in
arid regions.  Time of day, wind, and available water cause changes
in plant physiological functions.  Transpiration, gaseous exchange,
and leaf positioning are changed in response to the environment.
Because of these variables, contamination of plants will always
be a complex subject that will only be understood as each factor
is evaluated.

2.  Leaf morphology,
    The purpose of this paper Is not to review leaf morphology but
    simply make it clear that there are many differences in leaves,
    some of which may be very important in the collection and
    retention of radioibdine from fallout.  A review of the anatomy
    and morphology of leaves can be found in "Plant Anatomy" by
        /oc \
    Esau^   .   There  has been very little information reported con-
    cerning the effects of different leaf types in relationship to
    iodine contamination.  In 1963, Hungate, et al,»   ' reported
    on an experiment  where plants of different leaf characteristics
    had been contaminated by the effluent gases of a simulated
    reactor disaster.  Two of the species used in this field test
    were of extreme difference in leaf morphology.  The hairy leaves
    of geranium had no more iodine contamination per unit area of
    leaf surface than the smooth leaves of Peperomia.  Contrary to
    this, Romneyv    reported the results of Project Teapot where
    he observed that  hairy plants accumulated more fallout than
    smooth plants.
    Creosote bush, Larrea divaricata,  provides an example of another
    plant characteristic that effects  the retention of radionuclides.
    The* leaves of this species are covered with an exudate which gives
    the leaf a sticky surface.  This material acts as a trap for much
    of the particulate contamination which makes contact with the
    lea,f.  A comparison made in this laboratory revealed that the
    leaves of this plant are as sensitive a particle collector as
    are planchets which have been covered with an alkyd resin.
    The use of plants as an indicator  of the presence of radioactive
    contamination has an advantage.over planchets in that it is not
    necessary to pre-place the collector in the expected path of the
    contamination cloud.  Due to the stickiness of the leaves, the
    Southwestern Radiological Health Laboratory utilizes creosote
    bush, when available, to determine the location of the deposition


"hot line" which results from those tests conducted on the
United States Atomic Energy Commission** Nevada Test Site which
release radiation to the environment around the test area,  Samples
of vegetation are collected and counted for gamma activity.
Although some plant species have been regarded as better collectors
                                       (54  94)
of fallout than others and some authorsv . '  .   have reported
differences between species (casually observed) in their ability
to retain radioactivity, the effect of leaf morphology upon
collection or retention of fallout has not been evaluated con-
clusively.  This is an area of needed investigation.

A.  Roots
    Independent of the advent of nuclear weapons  and the threat of
    fallout contamination, "iodine in plants has been observed and
    reported (Orr, et al.£86\ 1948; Bohn^, 1917;  Campbell  and
    Youngv  ',1949; South Carolina Agricultural  Experiment
    Station^10^, 1929; Chilean Iodine Educational  Bureau,  Inc.^24',
    1948, (23h960; Vogel^115^, 1934; and Maihotra^66^,  1931).
    Selders^97;, 1954, was the first to report the  effect of  different
    substrate conditions on the uptake of iodine.   He experimented
    with plants both in soil  and in hydroponic cultures  and came to
    the following general conclusions:
    1.  The percent iodine in the plant tissue responded directly
        to the levels in the substrates.  At a level of six micro-
        grams of iodine (as KI) per gram of soil  the plant  concen-
        trations reached a maximum of aprroximately twelve  times
        that found in the substrate.
    2.  Iodine uptake increased by a factor of four when the  pH was
        changed from seven to four.  This was probably due  to the
        effect of the hydrogen ion upon the cell  membrane rather
        than any change in solubility or availability of iodine.
    3.  Th« four species tested absorbed iodine in  different  amounts.
        The order was bean>tomato>barley>Russian  thistle.
    4.  Iodine was only slightly translocated from  the site of
        original deposition.   Some iodine was lost  from  the roots,
        apparently, being translocated to the primary leaves  rather
        than to the culture solution,
Iodine is regarded as a physiologically non-essential element for
most plants.  It is possible  that iodine may partially substitute
for chlorine in some plant functions.  However, at  concentrations


above 1 yg/ml it produces toxic symptoms  in plants  and  therefore  interfers
with observations^  '.  llhler^11^'  found  that below toxic  levels  iodine
absorption and translocation were independent of both photoperiod and
transpiration.  In 1965, Uhler^^' reported on relationships  of  iodine
uptake and different metabolic inhibitors.   Iodine  uptake  was  found
to be independent of transpiration and followed a different pathway  than
cations under the same conditions.   Uptake  was also temperature dependent
and was decreased by metabolic inhibitors.   This evidence  suggests that
iodine absorption by roots is dependent on  a source of  energy  and is
therefore an active uptake process.
   The point of maximum uptake of iodine  in roots appears  to be within
a few millimeters of the root apex and is not enhanced  by  the  presence
of root hairs*44/.  jn the studies reported in this section, iodine
was present in the substrate in the iodide  form. Once  inside  of  the
plant, the majority of iodine remained in the iodide state. Of the
organic compounds of iodine which have been observed in plant  tissues,
three have been identified as ami no acids.   They are 3:5-di-iodotyrosine,
3:5:3-tri-iodothyronine and 3:5-di-iodothyronine^   .
Iodine contamination is not considered a  soil or root problem  because
of its short half-life.  However, it is soluble in  many forms, is
able to percolate into the soil, and (as  discussed  above)  is con-
centrated by plants when in the root substrate.  The limiting  factor
in this route of plant contamination is the reactivity  of  iodine  with
the organic and clay components of the soil^^ .  Iodine is mostly
held in the top few centimeters of the soil even against large amounts
of leaching water.  By the time radioiodine can reach the  root zone,
be absorbed into plants, and translocated to the leaves, it is of
little consequence as a radioactive element.

    The portion of iodine which reaches the edible portion of forage
    plants has had time to decay and much of the radioactivity is
    lost.  Soils contamination therefore is not considered to be a
    serious problem in the transport of radioiodine to man.
B.  Leaves
    Iodine from fallout has been observed to be absorbed into leaves.
    The extent of this absorption in comparison to that simply adsorbed
    to the surface is important because of the possibility of decon-
    taminating the plants by removing the latter in some cultural
    operation such as irrigating.  Hungate^  >55' and Selders^9°'
    followed the penetration of iodine from three different sources
    into leaf mesophyll.   They found that when leaves were exposed
    to elemental 131I, 35 to 40 percent penetrated to the mesophyll.
    When leaves were dipped in a solution of Na131I no penetration
    was observed.  Plants contaminated by the effluent from a
    simulated reactor accident had only 10 percent of the 131I in  the
    mesophyll of the leaf.
    One would expect that iodine in the form of a gas could enter
    plants via the stomates.  Meyer, et al., '"' listed the size of
    fully opened stomates of 14 different plant species.  Assuming
    an elliptical shape,  the calculated area of the stomate opening
    ranges from 17 to 294 square micrometers.   The size of gas mole-
    cules  is assumed to  be considerably smaller than this because
    gaseou^ water molecules, which are relatively complex, are known
    to readily pass through the stomate opening.  Aitken nuclei  and
    even larger particles up to perhaps 0.5 micrometer in diameter
    are also small enough to enter the stomate opening.

The motivating force behind most investigations of radioiodine has
been the desire to minimize the hazard of this pollutant (one of
the most prevalent in fresh fission fallout).  The degree of plant
contamination at the time of ingestion by cows is the primary factor
determining the amount of radioiodine which appears in milk.  The
amount of contamination a cow receives is determined by the amount
of deposition minus the amount lost before consumption.  An under-
standing of the loss of iodine from plants is therefore equally as
important as an understanding of its deposition.  Iodine-^ 131 decays
to 131Xe (stable) by both 3 and y emission with a radioactive half-
life of 8.05 days.  Activity is also lost by other processes.  The
effective half-life (T .-)  on plants is therefore defined as the
cumulative effect of both radioactive decay and all other loss pro-
cesses.  Reported values of T .... (Appendix B) range from 3.5 to
6.5 days.  Plants may lose contamination by three methods—dilution
by plant growth, loss of physiologically incorporated iodine, and
physical loss of surface-attached iodine.  For a review of effective
half-life of iodine on plants refer to Thompson^108'  and Chamberlain
and Chadwiek
A.  Growth
    Loss of contamination by growth is rather straightforward.   A
    given amount of contamination is simply diluted as  plants  increase
    in size and weight.  If contamination were expressed on the basis
    of ground covered by vegetation, this effect of dilution would be
    masked.  In some respects this masking may be desirable, but since
    a cow is interested in a quantity of feed and not on the area required
    to produce the feed, it seems only logical that data expression
    must be on a weight basis.   The effect of plant growth is  obviously
    most important during periods of rapid growth.

    As an example, consider an alfalfa field one week before cutting.
    Under good conditions, an alfalfa field may produce IJg to 2 tons
    per acre in a five-week period.   If the field were contaminated
    by 131-iodine and cut and fed one week later, the contamination
    would be decreased by 45 percent due to radioactive decay and
    another 20 percent due to dilution by plant growth.  It is
    obvious that under some curcumstances this type of loss may be
    of considerable importance.
B.  Absorbed Iodine Loss
    Translocation of iodine in plants away from the site of absorption
    has been studied by Fowden,  40'  Hungate et al.,    '  and Selders
    and Rediske, 97' and found to be very slow.   Experiments in this
    laboratory have shown that after 72 hours  in hydroponic cultures
    containing Na131I the distribution of 131I in bean plants is as
    shown in Table 3.
    Table 3.  Distribution of 131I in Bean Plants Growing in
              Na131I Contaminated Hoagland's Solution.
Stem .
' 2.1%'
    *Percent based on dry weight of tissue.
    Based on these observations  we would conclude  that  the transloca-
    tion of absorbed iodine is  very slow and that  it  is  only  of  minor
    importance in determining the effective  half-life of iodine  on
    Adsorbed Iodine Loss
    Chamberlain and Chadwickv  ' commented on five methods in which
    iodine may be lost from vegetation,  four of which describe
    adsorbed iodine loss.   Their conclusions are based  on reported
    literature and are as  follows:

    1.  Rain water is of secondary importance in washing iodine from
    2.  Volatilization has been reported as both important and
        unimportant as a mechanism of iodine loss from plants.  The
        importance of this is still uncertain.
    3.  Translocation to other parts of the plant is not rapid nor
        important as far as loss of iodine is concerned.
    4.  Dieback may cause some parts of the plant to escape sampling.
    5.  Plants may shed and regenerate parts of their cuticle.
There have been many differences in the reported half-lives of 131I
on vegetation  (Appendix B).  Some of these are undoubtedly a result
of differences in the mode of expressing results.  Other differences
may be due to environmental variables and the chemical or physical
form of the contamination.  There is no clear definition of the
relative .importance of the environment upon the loss of the contamina-
tion.  Different forms of iodine (particulate, gaseous, or liquid)
seem to be attached to or absorbed in plants with varying degrees of
affinity under different environmental conditions.  Therefore, it
seems logical that the loss of the iodine would also be dependent on
different forces.  Hhether these forces act cumulatively or indepen-
dently and what the major mechanism of loss is, remains a very complex
and challenging problem.  The full explanation for the relationship
between radioactive decay and effective half-life is, at this time,
not understood.
Straub^   ' reported that when cows were taken off 131I contaminated
feed the effective decay occurred in two phases.  The first portion
had a half-life of 16 hours to two days.  Later the effective half-
life leveled off to about seven days.  Experiments in this laboratory
with contaminated dry aerosols indicate the same type of decay scheme
in plants.  Immediately following contamination, 131I is lost from
plants rapidly.  The contamination is so loosely attached that it can
be blown off by wind or washed off by rain or irrigation.  After


a short period of time the contaminants become bound to the surface
and incorporated into the plant in such a way that they are dtslodged
only very slightly by changes in the environment.  A moderate amount
of experimentation in this lab indicates that the species of plant
and the physical and chemical form of the contaminant determines the
rate of fixation as well as the resultant loss rate.  We have observed
that this first period lasts from one to four days and has a T -* of
from one to three days.  After the end of the first phase, 131I is
lost from the plants much more slowly, i.e., T ^ * five to seven days,
Decay in this portion of the curve is more a result of plant growth
and radioactive decay of 131I than the loss of contaminant.  Figure 4
shows the decay of gaseous elemental 131I on alfalfa plants,
Figure 4.  Decay of 131I2  from Contaminated Alfalfa Plants,
           (Each point is the mean of four observations.)

                     V.  SUMMARY AND CONCLUSIONS

The term deposition velocity has been widely used to describe iodine
contamination of plants.  The physics of iodine transfer from air to
plants is a complex problem and involves both chemistry and physics
of the fallout, various forces which cause movement of the particles
in the atmosphere, and the behavior and extent of the boundary layer
which surrounds each leaf surface.  In 1966, Fisher^  ' developed a
model which can be used to predict the deposition velocity to within
a factor of three.  Increases in wind speed or particle size cause
a corresponding increase in deposition velocity.  It has been recog-
nized that different plant species collect contamination at different
rates.  These differences have not been clearly defined, but before
a complete understanding of deposition velocity can be attained,
differences in deposition on various species must be understood in
relationship to their physiology and leaf morphology.  Some of the
factors which should be evaluated are differences in deposition
under light and dark conditions, differences caused by variations
in leaf morphology, and differences caused by change in humidity.
Iodine is considered as a non-essential element for plant growth.
Absorption of iodine through the roots has been shown to be dependent
on the iodine concentration, pH, and plant species.  Although it
has not been documented, it appears that iodine absorption is by
an active uptake mechanism.  At levels above 1 yg/ml in a culture
solution, iodine was found to be toxic to plants.  After being
absorbed by a plant tissue, iodine is only very slowly translocated.
Contamination of plants through the roots by fallout iodine has been
shown to be of little importance in the total contamination of plants.
Foliar absorption, on the other hand, provides a route whereby iodine
can be fixed against most decontamination measures.  Foliar absorption
of iodine by plants is largely dependent on the chemical and physical
form of the contaminant.  Very small particles and gases can enter

the plant through the stomata.  Dissolved iodine enters through the
cuticle mainly in the areas of ectodesmata.  The rate of iodine
absorption by plants from different forms of contaminant is a field
which warrants added investigation,
The effective half-life of iodine on plant tissues includes both
radioactive decay and other loss processes.  Effective decay rates
have been reported from 3.5 to 6.3 days.  There are three methods of
loss which need to be considered in evaluating half-life data.
    1.  Apparent loss caused by dilution resulting from plant growth.
    2.  Loss from the exterior surface.  Suggested methods of loss
        are particle removal, volatilization, and cuticle flaking.
    3.  Loss from inside plants.  There is very little translocation
        of iodine but iodine can possibly, escape via transpiration
        or other gaseous exchanges.
The significance of these three routes has not been evaluated but
must be understood in order to accurately predict effective half-
lives.  Experiments done in this lab show that the effective decay
rate of iodine from plants occurs in two phases.  At first the loss
rate is rapid, presumably caused by the loss of surface contamination.
Later the loss rate is less with dilution by growth and loss of
absorbed iodine becoming the principal processes.
Various authors working with radioiodine have reported their results
on the basis of wet weight, dry weight, leaf area, and the total
ground area covered by plants.  This paper presents evidence to show
that areas of ground cover and wet weight are poor bases for data
expression.  Dry weight, although not perfect, is a much sounder basis
for expressing contamination data than either of the others.  Pre-
dictions of contamination cannot accurately be made until  we under-
stand the differences between species and these will never be
understood unless there is a standard method for data expression.

 1.  Adams, R. E., and W. E.  Browning, Jr.   Iodine vapor adsorption
     studies for the NS "Savannah" Project.   ORNL-3726 COak Ridge
     National Laboratory, Oak Ridge, Tenn.)

 2.  Agriculture Research Service, USDA.   Protection of food and
     agriculture against nuclear attack.   Agriculture Handbook No. 234.
     41 p. (1962)

 3.  Barry, P, J., and A, C.  Chamberlain.   Deposition of iodine onto
     plant leaves from air.  Health Physics  9:1149-1157. (1963)

 4.  Bartlett, B. 0., L. J. Middleton, G.  M.  Milbourne, H.  M.  Squire.
     The removal of fission products from  grass by rain, p.  51-53.
     Jin.ARCRL-5. (1961)

 5.  Batzel, R. E.  Distribution of radioactivity from a nuclear
     excavation, p. 3-18.  In UCRL 6249-T  (Lawrence Radiation  Laboratory,
     Livermore, Calif.)  (19FO)

 6.  Bohn, R. M.  The iodine content of food materials,  J.  Biol.
     Chem. 28(2):375-381. (1917)

 7.  Bolles, R. C., and N.  E. Ballou,   Calculated activities and
     abundancesof 235U fission products.   Research and Developemnt
     Report USNRDL-456. (1956)

 8.  Booker, D. V.  Physical  measurements  of activity in samples
     from Windscale.  AERE-HP/R-2607.  (1958)

 9.  Bostrom, R. G.  Iodine-131 in milk and  vegetables associated
     with July 1962 fallout in Utah.  Radio!.  Health Data 3(12):501-511.

10.  Broyer, T. C., A. B. Carlton, C.  M. Johnson, P. R. Stout.
     Chlorine—a micronutrient element for higher plants.
     Plant Phy. 29(6):526-532, (1954)

11.  Bruner, H. D.  Symposium on the biology of radioiodine, statement
     of the problem.  Health  Phy.  9:1083.  (1963)

Mote:  A number of books and papers which  contain useful information are
included, in addition to the references which are actually cited in  the

12.  Bucovac, M. J., S. H. Wittwer, H. B. Tukey.  Above ground plant
     parts as a pathway for entry of fission products into the food
     chain, p. 87-109.  ln_ E. B. Fowler (ed.), Radioactive Fallout
     Soils, Plants, Foods,'Man.  Elsevier Publ. Co., Amsterdam,
     London, New York.(1965)

13.  Bunch, D. F.  Controlled environmental radioiodine tests, Progress
     Report Number Two.  IDO-12053 (Sci. Envir; Sci. Services Admin.,
     Health, and Safety Div., Idaho Operations Office USAEC)

14.  Butler, G. W., and T. M. Johnson.  Factors influencing the iodine
     content of pasture herbage.  Nature 179:216-217.  (1957)

15.  Campbell, R. B. and G.  Young.  The iodine content of fruits and
     vegetables.  Can. J. Res. Sec F, 27(8):3pl-306. (1949)

16.  Chamberlain, A. C.  Aspects of the deposition of radioactive
     and other gases and particles.  Int. J. Air Pollution 3:63-88.

17.  Chamberlain, A. C.  Transport of particles across a boundary
     layer.  Great Britian Atomic Energy Research Establishment,
     Harwell, Berkshire, AERE-M-1122. (1962)

18.  Chamberlain, A. C.  Deposition, p. 125-132.  In I. A. Singer,
     M. E. Smith, E. W. Bierly (eds,), BNL 914 (C-"4?).  Conference on
     AEC Meteorological Activities. (May 19-22, 1964)

19.  Chamberlain, A. C.  Radioactive aerosols and vapours.  Contemp.
     Phys. 8(6):561-581. (1967)

20.  Chamberlain, A. C. and  R. C. Chadwick.  Deposition of airborne
     radioiodine vapour.  Nucleonics 8:22-25. (1953)

21.  Chamberlain, A. C, and  R. C. Chadwick.  Transport of iodine from
     atmosphere to ground.  AERE-R 4870. (1965)

22. .Chamberlain, A. C, and  H. J. Dunster.   Deposition of radioactivity
     in North-West England from the accident at Windscale.
     Nature 182(4336):629-630. (1958)

23.  Chilean Iodine Educational Bureau.  Iodine_and Plant Life.
     The Shenval Press, London, and Hertford. (1960)

24.  Chilean Nitrate Educational Bureau, Inc.  Bibliography of the
     literature on sodium and iodine in relation to plant and animal
     nutrition.  Chilean Nitrate Educational Bureau, Inc., 120 Broadway,
     New York, New York. (1948)

25.  Cline, J. F. and F. P. Hungate.   Effects of moisture and air
     temperature on deposition and retention of 131I2, p. 166-167.
     In Hanfprd Biology  Research Annual Report for 1964.  BNWL-122
     TTTanford. Laboratories, Richland, Wash.) (1966)

26,  C11ne, J. F., D, 0. Wilson, F. P. Hungate.  Deposition of 131I
     on vegetation.  HW-80500 (Hanford Laboratories, Richland, Wash.)

27.  Cline, J. F., D. 0. Wilson, F. P. Hungate.  Effect of physical
     and biological conditions on deposition and retention of 131I  on
     plants.  Health Physics 11:713-717. (1965)

28.  Cox, L. M. and L. Boersma.   Transpiration as a function of soil
     temperature and soil water stress.  Plant Physiol. 42:550-556.

29.  Davis, J. J., D. G. Watson, W. C. Hanson.  Some effects of environ-
     mental factors upon accumulation of worldwide fallout in natural
     populations, p. 35-38.  In V. Schults, A. W. Klement, Jr. (eds.)
     Radicacology.  Reinhold "Publ. Corp., New York, and A.I.B.S.,
     Washington, D. C. (1963)

30.  Division of Radiological Health.  Radiological Health Handbook.
     U. S. Dept. of Health, Education, and Welfare, PHS, Bureau of
     State Services, Division of Radiological Health, Washington 25,
     D. C. 468 p. (1960)

31.  Dunster, H. J., H. Howells, W. L. Templeton.  District surveys
     following the Windscale incident, October 1957.  Proc. Intern.
     Conf. on Peaceful Uses of Atomic Energy, Geneva, Switzerland.
     18:296-308. (1958)

32.  Edvarson, K., L. Ekman, A.  Eriksson, L. Fredriksson, U. Greitz.
     Studies on the relationship between 131I deposited on pasture
     and its concentration in milk, (Trans, from Swedish) p. la-13.
     In.NP-15568. (1965)

33.  Eggleton, A. E. J., D. H. Atkins, L. B. Cousins.  Chemical and
     physical nature of fallout 131I  and carrier-free  131I released
     in air.  Health Physics 9:1111.  (1963)

34.  Eisenbud, Mk and M. E. Wrenn.  Biological deposition of radio-
     iodine.  Health Physics 9:1133.  (1963)

35.  Eisenbud, M. and M. E. Wrenn. Short lived nuclides in the food
     chain and man, Sec F. p. 3-124a  and Sec A and B, p. 3-1 to 3-7.
     In, DA-49-146-XZ-153 (New York Univ. Medical  Center). (1966)

36.  Esau, Katherine.  Plant Anatomy.  John Wiley & Sons, Inc.
     New York, and Chapman & Hall, Ltd. London. 735 p. (1953)

37.  Federal Radiation Council Report No. .5,  Background material
     for'the developnient-of radiatton'protection standards.
     Federal Radiation Council, Washington, D, C.  (1964)

38.  Fisher, H. L.  Deposition velocities of aerosols and vapors
     on pasture grass.  In UCRL-14702 (Lawrence Rad,  Laboratory,
     Livermore, California! (1966)

39.  Fission Products Field Release Test-II, Convair, Fort Worth.
     Report NARF-60-IOT.  (1960)

40.  Fowden, L.  Radioactive iodine incorporation into organic
     compounds of various angiosperms.  Physiol, Planetarium
     12:657-664.  (1959)

41.  Fowler, E. B. (ed.).  Radioactive Fallout Soil,  Plants,
     Food, Man.  Elsevier Pub], Co., Amsterdam, London,
     New York.  336 p.  (1965)

42.  Franke, W.  Role of guard cells in foliar absorption.
     Nature 202:1236-1237.  (1964)

43.  French, ;N. R., K. H. Larson.   Environmental pathways of
     radioactive iodine from nuclear tests in arid regions,
     p. 5-19.   _In_ UCLA-499 (University of Calif., Los Angeles,
     School of Medicine)  (1961)

44.  Frere, M.;H., R. G. Menzel, K. H. Larson, and R. Overstreet.
     The behavior of radioactive fallout in soils and plants.
     National  Academy of Sciences, National Research  Council
     Publ. 1092 (1963)

45.  Garner, R. J.  An assessment of the quantities of fission
     products  likely to be found in milk in the event of aerial
     contamination of agricultural land.  Nature 186(4730):1063-1064.

46.  Gifford,  F. .A.- Jr., D.  H. Pack.   Surface deposition of
     airborne materfal.  Nuclear Safety 3(4):79.  (1962)

47. -Gorham, E.  A comparison of lower and higher plants as
     accumulators  of radioactive fallout.  Can. J. Bot. 37:327-329.
 -    (1959)

48.  Graham, .E. .R.  Plants as monitors of radioactive contamination
     at the environment of Los Alamos, New Mexico, p. 2-18.  In
     TID-4500  (22nd ed.) .(Los Alamos Sci. Lab. of Calif.,    "~
     Alamos, N. Mex.) (Also LAMS-2879, UC-41).  (1963)

49.  Hawley,.C. .A., Jr,,.C, .W..Sill,.G.. .L. Voelz,. and.N.,F,  Islttzer.
     Controlled Environmental Radioibdine test at the national  reactor
     testing station, :p, 61-63,  In IDO-12035 (USAEC, Oak Ridge Nat-
     tional Laboratory, Tenn.) (19F4)

50.  Healy, J. W., B. V. Anderson, H. V.  Clukey, J. K.  Soldat.   Pro-
     ceedings of the Second International Conference on the Peaceful
     Uses of Atomic Energy, Geneva, Vol.  18:309.  United Nations
     New York.  (1958)

51.  Hilsmeier, W. F.  Deposition calculation at Oak Ridge, pp. 144-145.
     In I. A. Singer, .M. E. Smith, & E. W. Bierly (eds.), BNL 914
     TT-42) Conference on AEC Meteorological Activities.   (May 19-22,

52.  Hsieh, J. J.  C.  Cuticular foliar sorotion of iodine, p. 147-149.
     JjrR. C. Thompson, E, G. Swezea (eds.), Pacific Northwest Labora-
     tory Annual Report for 1966 to the USAEC Division of Biology and
     Medicine.  BNWL-480 (Pacific Northwest Laboratory, Richland,
     Wash.) (1967)

53.  Hull, A. P.  Vegetation retention and vegetation--milk ratios of
     fallout 131I.  Health Physics 9:1173-1177.  (1963)

54.  Hungate, F. P., J. F. Cline, R. L. Uhler, A.-A. Selders.  Foliar
     sorption of I131 by plants.  Health  Physics 9:1159-1166.  (1963)

55..  Hungate, F. P., J. D. Steward, .R.  L. Uhler, J. F.  Cline.  Decon-
     tamination of plants exposed to a simulated reactor burn.
     HW-63173 (Hanford Laboratory, Hanford Atomic Products Operation,
     Richland, Wash.)  (1960)

56.  Islitzer, N.  F.  The role of meteorology following the nuclear
     accident in south-east Idaho.  U.  S. Weather Bureau  Report
     IDO-19310.  NRTS Idaho Falls, Idaho.  (1962)

57.  Islitzer, N.  F. Relation of deposition to meteorological
     variables, .p. 139-140. 'In_ I. A- Singer, ;M. E. Smith, &
     E. W. Bierly  (eds.), BNL 914 (C-42)  Conference on AEC Meteor-
     logical Activities.  (May 19-22, 1964)

58.  Jacobson, L., and R, Overstreet.  A  study of the mechanism of
     ion absorption by plant roots using  radioactive elements.
     Amer..J.Bot. 33:107-112,  (1946)

59.  Johnson, C. M.,.P.:R. Stout,J. .C. Broyer, .A. B. Carlton,  .
     Comparative chlorine requirements  of different plant species.
     Plant and Soil 8(4):337-353.  (1957)

60,  Jyung, .W, .H. and.S, .H. Wittwer,  Foliar absorption— an active
     uptake process.  Annual Review of Plant Physiology 10: 13-27, (1959)

61.  Koch, R. C. and B, Keisch.  Physical and chemical states of iodine
     in fallout.  -Status Report No, l,:p, 1-19.  JJTI NSEC-79-PT-1
     (Nuclear Sci. and Eng. Corp, , Pittsburgh, Penns.)  (1962)

62.  Kramer, Paul ;J.,  Transpiration and the water .economy of plants,
     p. 607-726.  In F. C. Steward (eds.), Plant Physio! bgy. Academic
     Press, New York" and London.  Vol. II.  (1959;

63.  Kuhn, W. E.  Fine particles characterization, Part I, p. 104.
     In W. E. Kuhn, Ultrafine Particles/  Wiley and Sons, Inc,
     New York, Sydney, and LomJoTn
64.  Larson, K. .H., J. W, Neel, H. A. Hawthorne, .H, M, Mork, R. H. Rowland,
     L. Baurmash, R. G. Lindberg, J. .H. Olafson, B. W. Kowalewsky,
     Distribution, Characteristics and biotic availability of fallout,
     Operation Plumb bob.  WT-1488 (Civil Effect Test Group, Univ. of
     Calif., Nuclear Lab., Los Angeles, Calif. ) 276 p. (1966)

65.  Lindberg R. G., E. ;M. Romney, J. H. Olafson, K. H, Larson,  The
     factors influencing the biological fate and persistence of fall-
     out, Operation Teapot.  WT-1177 (USAEC, Univ. of Calif. , Los
     Angeles, School of Medicine) 77 p. (1959)

66.  Malhotra, R. C. Permeability of iodine in some economic plants.
     Protoplasma 12:1-11.  (1931)

67.  Mamuro, T.,.K. Yoshikawa, T. Matsunami , A. Fujita.  Radionuclide
     fractionation in debris from a land surface burst.  (Trans, from
     Japanese) Health Physics 12:757-763.  (1966)

68.  Manzoor, E. R. and K. L. Babcock.   On the soil chemistry of
     radioiodine.  Soil Sci. 91(l):(no page given) (1961)

69.  Marter, W. L. Radioiodine release incident at the Savannah River
     Plant.   Health Physics 9:1105-1109.  (Also DPSPU-63-30-26B). (196 )

70,  Martin, W. E.  Loss of 131 I from a fallout contaminated vegetation.
     Health Physics 9:1141-1148.  (1963)

71.  Martini; W. ;E, -tosses ; of 90Srs '?9Sr,-and 131I from fallout contaminated
     plants.  Rad, Bot, 4(3);275^285.

72.  McConnon, ;D.  Radioiodine sampling with activated charcoal cartridges,
     p. 2-13.  In HW-77126 (Hanford Laboratory, Hanford Atomic Products
     Opera ti on ,~R"ich land, Wash,)  (1963)

73.,  Miaaw. W,;0, ind.R, C,  Chidwiek,   Harwell  Report,  'AERI^HP/M-114,

74.  'Megaw, .W. J, and.F..G.  May,   The  behaviour of iodine released
     in reactor containers.   Reactor Sci.  and Tech.  (J.  Nuclear
     Energy Parts A/B) 16:427-436.  (1962)

75.  Menzel, R.  G. Factors influencing the biological  availability
     of radionuclides for plants.  Fed, Proc. 22(6):1398-1401.   (1963)

76.  Meyer, B. S.,.D. B. Anderson, R.  H,  Bohning.  Introduction to
     Plant Physiology.  D. Van Nostrand Company, Inc.,  Princeton,
     New Jersey, Toronto, New York, London.  (1960)

77.-  Middleton,  L, J. and J. Sanderson.  The uptake of inorganic
     ions by plant leaves.  J. Exp. Bot.  16(47):197-215.   (1965)

78.  Middleton,  L. J. and J, M. Squire. •  The retention  of fission
     products on vegetation, p. 5051.'  \IrvARCRL-5.  (1961)

79.  Milbourn,.G. M. and R.  Taylor.  The  contamination  of grassland
     with radioactive strontium--!odine initial- retention and loss.
     Rad. Bot. 5:337-347.  (1965)

80.  Miller, C.  F.  Fallout nuclides solubility, foliage, contamina-
     tion, and plant part uptake contour  ratios.  SRI  Project No.
     IMU-4021 Office of Civil Defense, Dept. of Defense,  Washington,
     D. C. 29 p. (1963)

81.  Moorby, J., H. M. Squire.  The loss  of radioisotopes from the
     leaves of plants in dry conditions.   Rad.  Bot.  3:163-168.   (1963)

82.  Mork, H. M., K. H. Larson, B. W.  Kowalewsky, R. A.  Wood, D. E.
     Paglia, W.  A. Rhoads, R. B.  Guillou.   Characteristics of fallout
     from a deeply buried nuclear detonation from 7 to  70 miles
     from ground zero, Part.I. p. 10-64,  Part II. p. 66-84.   In
     Final Report UCLA School of Medicine Sedan 1966.   PNE-225 F
     (Univ. of Calif. School of Medicine  Laboratory of Nuclear
     Med. and Rad. Biology,  Los Angeles,  Calif.)  (1966)

83.  National Academy of Science.  The behavior of radioactive
     fallout in  soils and plants.  Nat. Res. Council Publ. 1092,
     21 p.  (1963)

84.  National Committee on Radiation Protection.  Maximum permissible
     body burdens and maximum permissible concentrations  of'radio-
     nucl ides in air and in  water for  occupational exposure.   Nat-
     ional Bureau of Standards Handbook 69.  95 p. (1959)

 85.   Nishita, .0,, :'E, ,M.  Romriey, ;K, .H,  Larson,--Uptake  of  radioactive
      fission products  by plants.  ,p, 55-81,  Jirv.E.  B,  Fowler  (ed,),
      Radioactive  Fallout Soils, Plants, Food  Man,  Elsevier  Publ,
      Co,,'Amsterdam, London,  New-York,   (1965)

 86.   Orr, J. B.,  F. C.  Kelley, G.  L. Stuar,  The  effect of  iodine
      manuring  on  iodine content of plants.   J. Agric,  Sci.  18:159

 87.   Ozanne, .P. G., J.  T,  Woolley,  T.  C.  Broyer.  Chlorine  and
      bromine in the nutrition of higher plants.   Australian J.
      of  Bio. Sci.  10(l):66-79,  (1957)

 88.   Pasquill, F,  Atmospheric Diffusion,  p. 231-240, 264, 267.
      London D. Van Nostrand Co., Ltd.  (1962)

 89.   Peirson,  D.  H., J.  R. Keane.   Characteristics  of  early fallout
      from Russian  nuclear explosions of 1961.  Nature  196:801-807,

 90.   Perkins,  R.  W.  Physical and  chemical form of  131I in  fallout.
      Health Physics 9:1113.   (1963)

 91.   Raynor, G. S.  The current status  of deposition research,
      p.  133-138.   In I.  A. Singer,  M.  E.  Smith, and E. .W. Bierly
      (eds.), BNL  9l4~ (C-42) Conference  on AEC meteorological
      activities,  (May  19-22,  1964)

 92.   Rickard,  W.  H.  Field observations  on fallout  accumulation by
      plants in natural  habitats.   J. of Range Management  18(3):
      112-114.  (1965)

 93.   Robinson, W. .0. and G. Edgington.  Minor elements in plants, and
      some accumulator plants.  Soil Sci. 60:15-28.  (1945)

94.   Romney, .E. M., R.:G. Lindberg, H. A. Hawthorne,.B. G.  Bystrom,
      K. H. Larson.  Contamination o'f plant foliage with radioactive
     fallout.   Ecology 44:343-349.   (1963)

95,  Sartor, .J. .D., W.  B, Lane,.J.  J,  Allen,   Uptake of radionuclides
     by plants.  Stanford Research Institute Project Nos,  MU»-5095
     and MU-5893.   (1966)

96.  Selders,.A. .A. and F..P,  Hungate,   The foliar sorption of iodine
     by plants, p, 4-11.  In_HW-44890 (Hanford Laboratory, Hanford
     Atomic Products Operation,  Richland, Wash.)   (1956)

 97.  Selders, .A. .A,  and.J,  H.  Redishke,   The uptake of iodine by
      higher plants,   HW-33'681  CHanford Laboratory,  Hanford Atomic
      Products Operations, Richland,  Wash,)   (1954)

 98.  Shleien, B.,.L.  Bernard,  A,  G.  Friend.   Autoradiographic
      examination of  airborne fallout for October-November.
      Radiological  Health Data  6:419-421.   (1965)

 99.  Shleien, ;B.,N.  A,  Gaeta, A.  G. Friend.  Determination of
      particle-size characteristic of old and fresh  airborne fall-
      out by graded filtration.  Health Physics 12:633-639.   (1966)

100.  Silverman, M. D. and W. E.  Browning, Jr.  Fibrous filters as
      particle-size analyzers.   Sci.  143(3606):572-573.  (1964)

101.  Simpson, C. L.   Deposition measurements at Hanford,  p.  141-143.
      In-I. A. Singer, M. E.  Smith, and E. W. Bierly (eds.),  BNL-914
      Conference on AEC meteorological activities.   (May 19-22, 1964)

102.  Soldat, J. K.  The relationship between I131 concentrations in
      various environmental  samples.   Health  Physics 9:1167-1171.

103.  South Carolina  Agricultural  Experiment  Station.   Iodine
      fertilization of plants.   South Carolina Experiment  Station
      (42nd Annual  Report for 1928-1929)

104.  Stewart, N. G.  and R.  N.  Crooks.  Long-Range travel  of the
      radioactive cloud from the accident at  Windscale.  Nature
      182(4636):627-628.   (1958)

105.  Straub, C. P.,  J. H. Fooks.   Cooperative field studies on
      environmental factors  influencing I131  levels  in milk.
      Health Physics  9:1187-1195.   (1963)

106.  Straub, C. P.,  J. H. Fooks.   Effect of  farm practices on
      radionuclides in milk.  Ohio Agr. Exp.  Sta. Spec, Report
      Ser. No. 1:108-120.  (1963)

107.  Thompson,  J,  C., Jr. Comparison of iodine-131  intake from
      milk and non-milk foods.   Health Physics 14(5):483-488.

108.  Thompson,  S,  .E,   Effective half-life of fallout radionuclides
      on plants  with  special  emphasis on iodine-131, ;p. 1-12,  In
      UCRL-12398 (Lawrence Rad. Lab,, Livermore, Caliv.)  (1965T

109.  Todd, F. A.  Protecting foods and water against radioactive
      contamination,  p. 235-256.   In  FAO,  IAEA, WHO  Seminar,
      Geneva 18022, (November 1963T" (1965)


110.  Tukey,,H,,B.,.S, .H,  Wittwer,.M,.J,  Bukovac,   Absorption.of
      radionuclides by above ground plant parts  and movement
      wlthtn the  plant,   Agr.  and Food  Chem,  9(2):106-113.   (1961)

111.  Turner,  F. :B.  Quantftative relationships  between fallout
      radioibdine on native vegetation  and in the  thyroids  of
      herbtvores.   Health Physics 9:12.  (1962)

112.  Turner, .F, .B,, W.  E. Martin,  Food-chain relationships of
      iodine-131  following two nuclear  tests  in  Nevada.  In
      Preliminary Report, Project Sedan.   PNE-236  p,   70 p. (1963)

113,  Uhler, R.  L.  Accumulation of iodine by intact barley plants,
      p. 181-185.   JjvH.  A. Kornberg,  E.  G.  Swezea (eds.),
      Hanford  Biology Research Annual Report  for 1964.  HW-80500
      (Hanford Laboratories, Rich!and,  Wash.)  (1964)

114.  Uhler, R.  L.  Absorption and translocation of RB  and I"  by
      intact pi ants j p.  163-165.  JjvR. E. Thompson,  S. W.  Wood
      (eds.),  Pacific Northwest Laboratory Annual  Report for 1964.
      BNWL-122 (Pacific Northwest Laboratory, Richland, Wash.)

115.  Vogel, F.   The effect of iodine on  different vegetables.
      Obst.  u  Gemuseb 80:19.  (1934)

116.  Wittwer,  S.  H.,.M.  J. Bukovac, W. H. Jyung,  Y.  Yamada,
      R. De, H.  P. Rasmussen,  S. N.  Haile Mariam,  S.  Kannan.
      Foliar absorption—penetration of the cuticular membrane
      and nutrient uptake by isolated leaf cells.   Dept.  of Hort.
      Mich.  State Univ.  14(1-2):105-120.   (1967)

117.  Wooley,  J.  T., T.  C. Broyer, G.'V.  Johnson.   Movement of
      chlorine  within plants.   Plant Phy. 33(l):l-7.   (January  1958)

118.  Yamagata,  N., K.  Iwashima.  Removal of  the radioactivities
      deposited on leafy  vegetables.  (Trans, from Japanese).
      UDC 614.73:613.262:641.6  (1963)

119.  Yamada,  Y.,  ;S.  H.  Wittwer,;M.;J.  Bukovac,   Penetration of
      organic  compounds  through isolated  cuticular membranes with
      special  reference  to I'*C urea1'2'3,'  Plant Phy. 40(1): 170-175.
      (January 1965)

120,  Zaduban,.M., M. Brutovskii,.G, Liptakova,.0,  Vinklerova.
      Determination of radioactive iodine in  plants,   (Trans, Czech.)
      Bipl., Acad. of Sci. Kosice, Czech, Biologica 21:578-588.


121,   Zaduban,.M.,  M,  Praslichka, :M,  Brutovskii, ,G,  Liptakova,
      0.  Vindlerova,   Relative and  absolute measurements  of activity
      in  solid and  liquid plant specimens,'  (Trans,  Czech,) Inst,
      of  Exper.  Biol,, Acad.  of Set., STI/PUB-137:69*79,   (1966)

122.   Unpublished data collected by Southwestern.Radiological Health
      Laboratory Personnel,   U, S,  Public Health  Service,   Las  Vegas,


APPENDIX A.  Deposition Velocity of 131I.                    43
APPENDIX B.  Effective Half-life of 131I.                    45
APPENDIX C.  Half-life of 131I on Vegetation Contaminated
             with Sedan Fallout.                             47
             C-l.  Groom Valley, Nevada                      47
             C-2.  Penoyer Valley, Nevada                    48
             C-3.  Railroad Valley, Nevada                   49
             C-4.  Currant, Nevada                           50

                                  APPENDIX A.   Deposition Velocity of 131I.
Dep. Vel.
V = cm/sec
1.53 ± 0.59
0.6 ± 0.22
1.91 ± 0.32
2.65 ± 0.50


Dry soil
of cover Wind RH
gm/m m/sec %
300W 15* 33
5.4* 34

46d 7.1*
129d ± 36
65d ± 15
129d + 19
75d ± 14

500W 4.20**
200W 3.72**
Temp Refer-
°C ence
17.8 3
9.3 3
104 .
10 20
18 20
No 131I was detected

Winds cale accident N
Windscale accident S

on samples

. England
. England
S.L. accident 1 KM from release
8.5 KM from releasee
67 KM from release
Grass in trays

Grass 13 cm high


                             APPENDIX A.  Deposition Velocity of 131I. (Continued)

± 0.21
± 0.19
± 0.27

± 2.80
10 y


of cove/

Wi nd RH Temp
m/sec • % °C
4.42** 20
3.10** 21
1.38** 16


Nearly dark
60-70 cm tall
60-70 cm tall
60-70 cm tall
60-70 cm tall
Zinc sulfide crystals
20.4 cm leaf blade (58% top,
29% bottom, 13% soil)
Strong inversion
Fluorescent particles
t = calculated Vq
± = 1 standard deviation
V = vapor
Sece = Seeale ceroeal (Rye grass)
Artr = Avtemesia tridentata (Big sagebrush)
Brte = Brorms teotorum (Cheat grass)
w = density based on vegetation wet weight
d = density based on vegetation dry weight
  *=wind measured at 4 m
 **rwind measured at 1 m
*** = height of measurement not indicated

                                    APPENDIX B.   Effective Half-life of 131I.








± 0
± P
± 0
± 0
± 0
± 0
± 0
± 0






grass &
Density of
Vegetation Method of
g/m2 Expression
46 Wet weight

300 Area


129d ±3.0 Area
6 ±1.4 Area
12 ± 1.8 Area
7 ±1.3 Area
Dry weight
Dry weight
Dry weight




CERT 1 wind 7.1 m/sec at 4 m 21.1°C
5.2%/day = rate of grass growth -
13 cm high

9.3°C 34% RH, wind

Based on five trial
Rain 65 mm on 18th
on T ff

Clipped 1.5 inches
Leaves only

Groom Valley 27 mi

5.4 m/sec CERT 7

day. No effect

from GZ
Penoyer Valley 44 mi from GZ
Railroad Valley 70
mi from GZ
Currant Valley 70 mi from GZ
Winds cale accident

                              APPENDIX B.   Effective  Half-life of 131I.  (Continued)

i i

IT 	 i ._ j j ~
Av desert
Density of
Vegetation Method of
g/m Expression


Russian series in 1961

Groom and Currant Valleys
All plants averaged—Groom, Currant,
Penoyer, Railroad Valleys
i - j. stcmuaru ueviauiun                                         fiio\
* = half-life was computed from data published by  Turner  & Martin   2Hsee Appendix C)
V = vapor
SD = Sedan debris
WF = World-wide fallout
Agde = Agropyron desertorum
Sece = Seoale oeTceal
Artr = Artemesia tridentata
Brte = Bromus tectorwn
Atco = Atriplex oonfertifolia
d = density based on dry weight
Area = ground covered by plant sample

           APPENDIX C.   Half-life of 131I  on Vegetation Contaminated with  Sedan  Fallout*.

Half-life was computed  for samples collected at each point even though  there  was  no  replication  in  the
sampling.  Variation between points was so great that grouping of points was  considered  invalid.  Half-
lives for each area were computed by taking the mean of all points and  compounding the errors.
C-l.  Groom Valley, Nevada
Point 2
Time- Days
T ff
9.3 ± 1.2

Activity (pCi/g of vegetation)
6.3 ± 0.6

7.5 ± 1.1

5.3 ± .7

7.1 ± .5


6.3 ± .8
fJote—Mean half-life 7.0 ± .3        /
*Adapted from Turner and Martin, 1963V112>
tOmitted from analysis

               APPENDIX C.   Half-life of 131I  on Vegetation Contaminated with  Sedan Fallout.

     C-2.  Penoyer Valley,  iNevada
Point 1
Time- Days

8.7 ± .8
4 5
Activity (pCi/g of

8,0 ± .6

8.0 ± .9
9.0 ± 1.0

8,0 ± 2.4

8.4 ± 1,0
     Note—Mean half-life 8.4 ± .5
     tOmitted from analysis
     *Adapted from Turner and Martin, 1963 ^   '

          APPENDIX  C.  Half-life of  131I on Vegetation Contaminated with Sedan Fallout/

C-3.  Railroad  Valley, Nevada
Point 2
T ff

5.3 ± .8

3 4
Activity (pCi/g of

6.8 ± .8

5.8 ± .9


7.9 ± .6

8,2 ± 1.4

 Note—Mean  half-life  6.8  ±  .4
 *Adapted from Turner  and  Martin.  1963.  (112)

               APPENDIX C.  Half-life of  i3ij on Vegetation Contaminated with Sedan Fallout.*

       C-4.  Currant, Nevada
31 ...
. 9.1 ± 1.8
(pCi/g of vegetation)
11.4 ± 1.4
7.6 ± 1.9
9.4 ± 1.2
      Note—Mean  half-life  9.4  ±  .8

      *Adapted  from  Turner  and  Martin  1963.  (112)


1  - 20  SWRHL, Las Vegas, Nevada
     21  Robert E.  Miller, Manager,  NVOO/AEC,  Las  Vegas,  Nevada
     22 .R. H. Thaigott, Test Manager, NVOO/AEC,  Las  Vegas,  Nevada
     23  Henry G.  Vermillion, NVOO/AEC, Las  Vegas, Nevada
     24  Chief, NOB/DASA, NVOO/AEC,  Las Vegas, Nevada
     25  Robert;R.  Loux,. NVOO/AEC,  Las Vegas,  Nevada
     26  D. .W. Hendricks, NVOO/AEC,  Las Vegas, Nevada
     27  Mail & Records, NVOO/AEC,  Las Vegas,  Nevada
     28  Martin.B.  Biles, DOS, USAEC,  Washington,  D.  C.
     29  Director,  DMA, USAEC, Washington,  D.  C.
     30  John S. Kelly, DPNE, USAEC, Washington,  D. C.
     31  Daniel ;W.  Wilson, Div. of  Biology  & Medicine,  USAEC,  Washington,  D.  C.
     32  Philip Allen, ARL/ESSA, NVOO/AEC,  Las Vegas, Nevada
     33  Gilbert Ferber, ARL/ESSA,  Silver Springs, Maryland
34 - 35  Charles L. Weaver, BRH, PHS,  Rockville,  Maryland
     36  J. C. Villforth, Director,  BRH, PHS,  Rockville,  Maryland
     37  John.G. Bailey, BRH, PHS,  Rockvilie,  Maryland
     38  Regional  Representative, BRH, PHS,  Region IX,  San Francisco,  Calif.
     39  Bernd Kahn, BRH, Chief of  Rad. Eng. Lab.,'Cincinnati, Ohio
     40  Northeastern Radiological  Health Laboratory, Winchester, Mass.
     41  Southeastern Radiological  Health Laboratory, Montgomery, Ala.
     42  W. C. King, LRL, Mercury,  Nevada
     43 ;D. Hamil,  Technical  Library,  AEC/NVOO, Las Vegas, Nevada
     44  Harry.L.  Reynolds, LRL, Livermore,  California
     45  Roger Batzel, LRL, Livermore, California
     46  Ed Fleming, LRL, Livermore, California
     47  Wm.  .E. Ogle, LASL, Los Alamos, New Mexico
     48  Harry.S.  Jordan, LASL, Los  Alamos,  New Mexico

     49  Arden Bicker, REECo,'Mercury, Nevada
     50  Clinton.S, Maupin, REECo, Mercury,  Nevada
     51  Byron Murphey, Sandta Corp.,  Albuquerque, New Mexico
     52  R. H. Wilson, University of Rochester, New York
     53  R. S, Davidson, Battelle Memorial  Institute,  Columbus,  Ohio
54 - 55  DTIE, USAEC, Oak Ridge, Tennessee
     56  Paul T.  Tueller, U.  of Nev.,  Reno,  Nevada
     57  Charles  Hanson, U. S. Fish &  Wildlife Service, Las  Vegas,  Nevada
     58  V. R. Bohman, U. of Nev.,.Reno, Nevada
     59  H. M. Kilpatrick, U,  of Nev., Reno, Nevada
     60  Director, Nevada Fish &-Game, Reno, Nevada
     61  CETO, Ecology Studies, Mercury, Nevada
     62  Dr. Arthur Wallace,  Lab. of Nuclear Med.  & Radiation Biology,
           U. of  Cal., Los Angeles, California  90007
     63  Dr. Wade Berry, Dept.  of Vegetable  Crops, U.  of Cal.,
           Riverside, California  92507
64 - 65  William  Link, BRH Library, Rockville, Maryland