Concentration factors and transport models for radionuclides in aquatic environments : a literature report


                                Ecological Research Series
              CONCENTRATION FACTORS  AND
                    TRANSPORT MODELS  FOR
RADIONUCLIDES IN AQUATIC ENVIRONMENTS
                          A Literature  Report
                     Environmental Monitoring and Support Laboratory
                            Office of Research and Development
                           U.S. Environmental Protection Agency
                                 Las Vegas, Nevada 89114

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                 RESEARCH  REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency,  have been grouped  into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:

     1.    Environmental Health Effects Research
     2.    Environmental Protection Technology
     3.    Ecological Research
     4.    Environmental Monitoring
     5.    Socioeconomic Environmental Studies

This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research  on the  effects  of pollution on  humans,  plant and animal
species, and materials.  Problems are assessed for their long- and short-term
influences. Investigations include formation, transport, and pathway studies to
determine the fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living organisms
in the aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.

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                                             EPA-600/3-76-054
                                             May  1976
   CONCENTRATION FACTORS AND TRANSPORT MODELS FOR
       RADIONUCLIDES IN AQUATIC ENVIRONMENTS
                A LITERATURE REPORT
                        By
                 Robert G. Patzer
Monitoring Systems Research and Development Division
  Environmental Monitoring and Support Laboratory
                Las Vegas, Nevada
  ENVIRONMENTAL MONITORING AND SUPPORT LABORATORY
       OFFICE OF RESEARCH AND DEVELOPMENT
      U.S. ENVIRONMENTAL PROTECTION AGENCY
            LAS VEGAS, NEVADA  89114

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                             DISCLAIMER
     This report has been reviewed by the Environmental Monitoring and
Support Laboratory-Las Vegas, U.S. Environmental Protection Agency, and
approved for publication.  Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
     Effective June 29, 1975, the National Environmental Research Center-
Las Vegas (NERC-LV) was designated the Environmental Monitoring and
Support Laboratory-Las Vegas (EMSL-LV).  This Laboratory is one of
three Environmental Monitoring and Support Laboratories of the Office
of Monitoring and Technical Support in the U.S. Environmental Protection
Agency's Office of Research and Development.
                                    ii

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                             ABSTRACT
     The relative risks to man. from radionuclides released to the environ-
ment depend heavily on their accumulation or concentration by aquatic
organisms.  The organisms which accumulate those radionuclides present
in the environment may be useful as indicators for environmental moni-
toring purposes.  In addition, these organisms may be directly in food
chain pathways to humans.
     Literature is reviewed and summarized in regard to biological concen-
tration of radionuclides in, freshwater and marine environments.  Concen-
tration factors for elements found in organisms are tabulated for plants,
invertebrates, and fish in marine and freshwater environs.  Literature is
also reviewed on models developed to calculate the possible radiation dose
delivered to humans from radionuclides released into aquatic environments.
The model approaches summarized range from simple generalized forms which,
at best, give order of magnitude estimates to detailed models for a specific
area which may be used to guide waste discharge practices.
                                 iii

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                        TABLE OF CONTENTS
                                                                  Page
Disclaimer                                                          ii
Abstract                                                          iii
List of Figures and Tables                                          vi
Acknowledgment                                                    vii
SECTIONS
  I.  Introduction                                                  1
 II.  Summary                                                       2
III.  Conclusions                                                   3
 IV.  Recommendations                                               5
  V.  Objectives and Approach                                       8
 VI.  Results                                                       12
        Concentration Factors                                       12
        Indicator Organisms                                         21
        Environmental Studies                                       24
        Radiation Pathway and Dose Models                           28
        Critical Pathway Approaches                                 31
        Specific Activity Approaches                                43
VII.  References                                                    50
                                 iv

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                    LIST OF FIGURES AND TABLES

 FIGURES                                                       Page

 1.  General Steps in Critical Pathways Evaluation for          33
     Aquatic Environments
 TABLES

 1.  Comparison of Critical Concentration Factors from          13
     Different Sources—Marine Plants

 2.  Comparison of Critical Concentration Factors from          14
     Different Sources—Marine Animals

 3.  Marine Plants—Critical Concentration Factors              15

 4.  Marine Invertebrates—Critical Concentration               15
     Factors

 5.  Marine Fish—Critical Concentration Factors                15

 6.  Freshwater Plants—Critical Concentration Factors          17

 7.  Freshwater Invertebrates—Critical Concentration           19
     Factors

 8.  Freshwater Fish—Critical Concentration Factors            20

 9.  Relative Abundance of Radionuclides in Four Species        24
     of Mollusca from the Same Environment

10.  Ranges of Element Concentration Factors in Marine          25
     Organisms

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                            ACKNOWLEDGMENT
     The technical assistance of Patricia L. Foster in summarizing
information from the literature and in preparing this paper is
greatly appreciated.
                                   vi

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                            SECTION I
                          INTRODUCTION
     The relative risks to man from radionuclides present in water
depend heavily on their accumulation or concentration by organisms
living in that water.  Organisms which accumulate those radionuclides
present in the environment may be useful as indicators for environ-
mental monitoring purposes.  In addition, these organisms may be
directly or indirectly in food chain pathways to humans.  The assess-
ment of the potential human effects resulting from radionuclide
releases to aquatic environments requires an understanding of the
fate of the radionuclides in various environments.  Of particular
interest is the tendency for many organisms to extract and accumu-
late trace materials from their environment.  This tendency is
commonly measured in terms of a concentration factor (CF).  The
CF is defined as the ratio of the concentration of an element in
an organism or its tissues to that found in ambient water.  While
this definition has some deficiencies, it provides a convenient
means to compare the relative accumulation of substances in various
organisms.  Given the CF and other related parameters, mathematical
models can be developed to provide estimates of the radiation dose
to humans from the consumption of foods derived directly or indirect-
ly from aquatic environments contaminated with radionuclides.

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                          SECTION II
                           SUMMARY
     Literature is reviewed and summarized in regard to biological
concentration of radionuclides in freshwater and marine environments.
Concentration factors for elements found in organisms are tabulated
for plants, invertebrates, and fish in marine and freshwater environs.
The range of concentration factors reported from environmental studies
is given, and potential sources for variability in concentration
factor determinations are discussed.  Elements for which no data
were found in the literature are identified.
     The potential for using producer, primary consumer and higher
order consumer organisms as biological indicators of environmental
pollutant levels is discussed.  Some research efforts in this area
have been reported; however, no reliable pattern has emerged upon
which to base a general monitoring program.
     Considerable effort has been expended toward developing methods
to calculate the possible radiation dose delivered to humans from
radionuclides released into aquatic environments.  Most of such
work involves the use of mathematical models in which specific environ-
mental information provides many of the required parameters.  While
many approaches are summarized in this report, most may be classed as
either critical pathway or specific activity methods.  The approaches
summarized range from simple generalized forms which, at best, give
order of magnitude estimates to detailed models for a specific area
which may be used to guide waste discharge practices.

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                              SECTION III
                              CONCLUSIONS
1.  Concentration. Factors
    Variability in the concentration factors reported for similar
organisms from different but similar environments appears to preclude
the use of general concentration factors to assess the current or
previous levels of radionuclides in any particular aquatic environment.
Although many freshwater and marine organisms accumulate or concentrate
radionuclides present in an aquatic environment, the concentration factors
reported in the literature indicate that local conditions strongly affect
concentration factors for organisms.  Even for a given area the concen-
tration factor for a given organism can be expected to vary with changing
local conditions; for example,  season, water temperature, and total
biomass present.
2.  Preliminary Estimates
    The unit-rad contamination factors, discussed under RECOMMENDATIONS,
page 5, are useful in making preliminary assessments of a situation.
Further assessment will require field studies to evaluate the situation
in aquatic environments where problems are anticipated.  Each body of
water has mixing characteristics which are unique in place and time.
Moreover, radionuclides introduced into and diluted within aquatic environ-
ments can remain in solution or suspension, precipitate and settle on the
bottom, or be reconcentrated by plants and animals.  The species and popu-
lation density of plant and animal life present in a body of water are
also unique in place and time.  In addition, the physical, chemical
and biological interactions of a radioisotope are influenced by the
presence or absence of other isotopes not only of that element but also
of other elements.
3.  Models for the Environment
    Monitoring networks for aquatic environments can provide specific
information required in models.  Large numbers of environmental models

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have been developed for use in calculating potential radiation doses to
humans following release of radionuclides to aquatic environments.  The
radiation exposure of humans through environmental pathways has been
studied extensively from almost the inception of the nuclear industry.
Even the simplest of these models requires considerable information
concerning the particular environment and population at risk in order to
complete a risk or radiation dose assessment.  Although simple or complex
models may be written in generalized forms, the input parameters are
specific for the environment of interest.  The number and degree of
complexity of models reported in the literature allow selection of a
model to use for making calculations based upon the amount of information
available on the environment of interest.  The more extensive the data
base, of course, the more reliable can be the information derived from the
models.
4.  Uses for Aquatic Organism Samples
    Aquatic organisms can provide valuable information on radionuclide
cycling in the environment.  Because aquatic organisms concentrate radio-
nuclides released to their environment to a considerable degree, even if
variable, they provide valuable environmental monitoring samples which
(1) indicate whether radioisotopes are concentrating within food chains
leading to man; (2) delineate the geographical areas involved in a potential
problem; (3) provide valuable information on whether additional control
measures are needed; and (4) demonstrate environmental benefits gained
when control measures are applied.

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                           SECTION IV
                         RECOMMENDATIONS
1.  Field Studies
     This program was limited to a general literature review for data
and models related to the behavior of radionuclides in aquatic environ-
ments.  It was not within the program scope to evaluate the accuracy or
reliability of information reported.  The wide range in concentration
factors found in the literature leads to the recommendation that,
initially, field studies be conducted to evaluate the situation in
each aquatic environment where problems are anticipated.  A sufficient
body of information exists to make preliminary evaluations of most
environments; however, data from detailed field studies would supple-
ment this information and, perhaps, provide a basis for recommending
that less detailed studies be required to adequately assess hazards
of radionuclides in other aquatic environments.
2.  Preliminary Evaluations
     It is recommended that the "unit-rad contamination factors"
as published in Lawrence Livermore Laboratory (LLL) reports be used
to make preliminary evaluations of radionuclide releases to aquatic
environments.  These factors are discussed under RESULTS.  Areas
where detailed field studies should be carried out can be selected
on the basis of the preliminary evaluations.  The LLL program is
a continuing effort and revised information is incorporated into
their system as more specific data become available.  The reports
contain a comprehensive listing of aquatic concentration factors and
population dose estimates.  The LLL program approaches environmental
contamination by radionuclides and the resultant radiation dose to
man from the standpoint of element specific activity—the biological-
exchangeable-pool-i-of-elements concept.  Using this approach, the
passage of a radionuclide through the biosphere is presumed to be
governed by the same factors that govern the distribution of the
related stable element isotopes within the biological exchangeable
pool.  It is assumed that the radionuclide is biologically no more

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available than the related stable isotopes within  the  environment.  This
approach should be valid for the types  of radionuclide releases  anticipated
in the nuclear industry—low-level wastes diluted  and  dispersed  in  large
bodies of air and water.
     The product of the LLL program is  a value for each isotope  called
the "unit-rad contamination in water  (F.)11 for both  freshwater and  sea
                                        f\
water.  This factor is defined as the initial concentration  of a radio-
isotope in water which would yield a 30-year integrated dose of  1 rad
to a specific designated tissue of the  standard man.   In most cases F.
                                                                     A
values for infants are also estimated.  The assumptions in the many
steps involved in reaching F  values are basically conservative  in
                            £\
nature, i.e., they are aimed toward obtaining F  values for  the  worst
                                               A
situation that could develop.
3.  Monitoring Network Design
     Although considerable information  is available  for making generalized
estimates of the radiation dose to people from radionuclides released  to
aquatic environments, information relevant to specific areas generally
has not been collated.  For example, seafood distribution and consump-
tion patterns for an area are generally available  through food distribu-
tors and dietary surveys, but have not  been collated for making  potential
radiation dose estimates.  Before such  information is  tabulated,  however,
a decision should be made on its desired accuracy  and  validity.   The
ultimate objective should be to obtain  radiation dose  estimates  with a
given degree of reliability.  In order  to obtain this  objective,  each
data base for model parameters has a defined degree  of reliability.
Such considerations are part of monitoring network design criteria  which
are being developed at the EPA's Environmental Monitoring and Support
Laboratory at Las Vegas.  At present design criteria are being developed
for air monitoring networks.  These efforts should be  extended to encompass
design criteria for gathering information needed to assess the potential
radiation dose to people from radionuclides released to aquatic  environ-
ments.

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4.  Emphasis for Future Investigations
     Some investigations on critical pathways indicate  that the biomass
and sediments may be neglected as  a depot of radioactivity in a fresh-
water aquatic system, although as  a rule of thumb it  can be assumed
that there is a thousandfold average concentration of all radionuclides
in the biomass and that the bottom sediment has an average concentration
a hundredfold greater than the water concentration.   Apparently, the
biomass and sediment have a small  potential for transferring radioisotopes
to people when compared with direct water intake.  This concept, which has
developed from tracer radioisotope studies in freshwater systems, has
important implications in assessing freshwater pollutants of many types.
The concept should be pursued in depth.  Perhaps priority attention
should be directed toward the oceans where the majority of all pollutants,
however released, will ultimately  reside.  Some pollutants in the oceans
will be returned to man through seafoods; however, the seafood yield of
the world's oceans has been decreasing annually for many years.  It
appears that more emphasis should  be placed on studying pollutant
effects in ocean environments.  Biological effects of released
radioisotopes on ocean biota are not expected to be observable
because of the low concentrations  expected.  However, radioisotopes
already in the environment and those to be released in the future can
provide valuable information" on the rates of pollutant transfer from
land sources to the ocean and on pollutant mixing patterns and fate
in the oceans.  Since man depends  on the oceans for most of his
oxygen, and, potentially, a large  portion of his food, he has a
vital stake in understanding and managing the productivity and
well-being of the seas.

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                             SECTION V
                      OBJECTIVES AND APPROACH
     The objectives of this project were to survey  literature  on
aquatic environments and:
     1.  Tabulate concentration factors for radioisotopes
         which may be released to the environment through
         man's activities and yield a significant radiation
         dose to man through aquatic pathways,,
     2.  Identify indicator organism groups with high concen-
         tration factors for potential use in monitoring and
         assessment efforts, and
     3.  Survey environmental models used for calculating the
         potential radiation dose to man through aquatic
         pathways.
     A concentration factor (CF) is defined as the ratio of the
concentration of an element in an organism or its tissues to that
found in ambient water.  In reviewing and evaluating the literature,
it was found that long-lived radioisotopes with CF's of about  10,000
or greater in biota were of primary importance for identifying
indicator organisms and for estimating potential radiation doses to
man.  A CF of 10,000 or more is herein defined as the critical CF,
and data on critical CF's are summarized in the following sections.
The value of 10,000 was selected to concisely summarize data which
are most pertinent to hazards assessment.   Data on CF values less
than 10,000 can be obtained from the referenced literature.  In
addition to isotopes with critical CF's, the CF's for several  elements
of current interest are included in the data summarized—even  though
the CF's are often relatively small.  However, small amounts of some
of these elements are considered to be much more dangerous to  man than
their CF's might appear to indicate.  Furthermore, their potential
biological effects on man warrant concern, vigilance and control.
These elements include plutonium, strontium, cesium, uranium,  and
iodine.  Since CF's for many isotopes were not identified in the

                                 8

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literature, and because the various isotopes of the same element
generally exhibit the same chemical characteristics, the CF for
one isotope is presumed to be applicable for other isotopes of
the same element.
     Indicator organisms may be useful in the following categories:
     1.  Alert.  Indicate that radioisotopes are concentrating
         within food chains which could lead to man.
     2.  Assess.  Evaluate the potential magnitude of intake by
         man and note trends in aquatic organism concentrations
         (increasing, decreasing, or stable).
     3.  Del-ineate.  Show the geographical area involved in the
         potential problem.
     4.  Control.  Decide whether control measures are needed and,
         if they are applied, demonstrate the environmental
         benefits gained.
     Many models have been reported in the literature for calculating
the potential radiation dose to man through aquatic pathways from
radionuclides released to the environment.  Several of these models
are described in this report.
     The approach was to survey literature on aquatic pathways and
to summarize CF's for elements within organisms which live in various
aquatic environments.  This information, together with information on
the radioisotopes released to the environment from nuclear activities,
gives a data base to identify which radioisotopes may be important
in various food chains leading to man, to identify indicator organisms
with potential value in monitoring and assessment efforts, and to
select appropriate models to make calculations of potential radiation
doses to man.  The type of data available on the environment in question
determines which type of model is appropriate.
     In addition to the critical CF criteria, the following guidelines
were formulated to focus the literature review on information relevant
to the objectives:

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1.  Primary attention is given to those radioisotopes which may
    yield a significant radiation dose to man through
    aquatic pathways.
2.  Long-term and low-level releases of radioisotopes to the
    environment are of primary interest.  Therefore, CF's
    for rathet stable release rates and water concentrations
    are applicable.  The nuclear industry guidelines for
    radioisotope discharges are of this nature.  Concentra-
    tion factors and environmental half-times for accidental
    releases (pulse labeling) are extremely dependent on
    local environmental conditions prevalent at the particu-
    lar time of release and are not amenable to generaliza-
    tion.  Therefore, time-dependent variables such as biolo-
    gical half-times and uptake rates are not identified in
    this report.
3.  Certain types of data necessary for hazards assessment are
    beyond the scope of this report.  The CF for a radioisotope
    bears little relationship to the potential hazard to man.
    Extensive data are available in the literature and in
    federal and international radiation standards on the
    relative hazards of radioisotopes based on decay emissions
    and energies, biological and physical half-lives, biological
    deposition sites, etc.  These data are given for soluble
    and insoluble forms of the isotopes and for various routes
    of exposure.  While such data may not be applicable for
    isotopes incorporated in unknown chemical forms in aquatic
    organisms, no attempt is made in this review to identify
    the chemical forms of radioisotopes within biota.  The
    published data on biological and physical parameters for
    isotopes are not rei.terated,
4.  While certain radioisotopes are considered more hazardous
    than others, none were excluded frorr a search for concentra-
    tion factors.  The exclusion from such a search may lead to
    unwelcome uncertainties in the assessment of a situation
                        10

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         involving a mixture of radionuclides.  In addition, it
         is difficult to predict the kinds and amounts of radio-
         nuclides to be released in the future from nuclear
         facilities, medical facilities, and various laboratories.
     This report serves to present reported information on parameters
needed to estimate radiation doses to man from various radionuclides
which may be discharged to a given sector of an aquatic environment.
Many parameters are extremely location-dependent and, therefore, are
part of this literature survey only in that they are identified and
evaluated in the dose computation models which are referenced.  These
parameters include such things as dilution factors, dispersal rates,
mixing depths, biota prevalence, the organisms and their tissues
directly consumed by man, and the indirect contributions from organisms
in food chains.
                                11

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                            SECTION VI
                              RESULTS
 CONCENTRATION  FACTORS
      The term  concentration factor  (CF) has been defined  (Thompson et al. ,
 1972)  as "the  ratio  of  the concentration  of an element  or radionuclide in
 an aquatic organism  or  its tissues  to that in the surrounding water  under
 equilibrium or steady-state conditions."  This definition does  not allow
 for the fact that  aquatic organisms normally  derive  their nutrients  from
 a variety of sources such as  food, water, and suspended or deposited
 sediments.   Polikarpov  et al.  (1966) noted this restriction in  part  by adding
 that "the capacity of an organism to accumulate radioactive substances is
 expressed by the ratio  of its  radioactivity to that  of  the aqueous medium
 or the preceding food link in which the radionuclide was  concentrated."

      This limitation is especially apparent with certain  benthic  organisms
 that live in bottom  sediments  and feed on debris (for example,  some
 mollusca).   Comparison  of the  trace element concentrations found  in  the
 tissues of  these organisms with  the concentrations found  in open  sea-
 water  is not a truly valid means to determine concentration factors.
 Yet, Lowman et al, (1971) describe many benthic organisms which are efficient
 accumulators of trace elements from water and are an important  fraction
 of the total biomass in marine areas of economic importance.

     Fewer  problems  are encountered in determining a CF for phytoplankton
 because there  are  no intervening trophic  levels between water and their
 nutrient source.   Data  on marine plants  (Thompson et al. , 1972) from the
 Lawrence Livermore Laboratory  (LLL, formerly  the Lawrence Radiation
 Laboratory)  do not distinguish between phytoplankton and  benthic  or
 macrophytic algae, nor  between zooplankton and macroinvertebrates.  This
 ambiguity could lead to misinterpretation of  what organisms are of most
 importance  in  a particular situation.  Table  1 is a  comparison  of CF data
from the LLL report to CF values  for benthic algae and phytoplankton
                                 12

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reported by  the  National Academy of Science/National  Research Council
(NAS/NRC, 1971).   In general, data from the latter report  indicate that
CF's for phytoplankton are higher (sometimes by 1 to  2  orders of magnitude)
than those for benthic algae.  Furthermore, the LLL average measured values
tend to be lower than the NAS/NRC phytoplankton data, indicating that
the LLL data are weighted towards benthic and/or macrophytic  algae.   On
the basis of NAS/NRC data for phytoplankton, the CF's for  aluminum,  cerium,
copper, silver,  and zinc appear to be 10,000 or greater—values  higher  than
the CF's listed  in the LLL report (see Table 1).

       TABLE 1.   COMPARISON OF CRITICAL CONCENTRATION FACTORS FROM
                  DIFFERENT SOURCES—MARINE PLANTS (VALUE LISTED  X
                  10  = CF)
Element
Sc
Mn
Fe
Y
Zr
P
Pb
Al
Ce
Cu
Ag
Zn
Pu
Thompson ei, al. (1972)
Marine Plants
Derived ^
100.0
20.0
50.0
10.0
10.0
2.8
1.0
0.6
5.0
1.0
0.2
1.0
0.35
Maximum ,, ,.
Measured
25.0
22.0
0.9
—
1.6-3.5
Average , .
Measured
5.5
0.73
3.0-4.0
5.0-10.0
0.6-0.7
—
0.9-3.0
NAS/NRC (1971)
Benthic
Algae
2.0
2.3
4.8
0.48
2.2
10.0
0.7
15.0
0.67
0.1
0.41
1.3
Phytoplankton
2.0
4.0
4.0-45.0
1.0
60.0
3.0-34.0
40.0
100.0
90.0
30.0
23.0
1.5-20.0
2.6
       Dash  (—)  indicates no data in reference cited.
       (a)r
       (b)
Derived on the basis of stable element concentrations.
Measured in radioisotope studies.
          Average of values from radioisotope studies.

      In Table 2 marine animal data are  listed  in a similar manner from the
 the above LLL and NAS/NRC reports.  Data  from  the former on marine inverte-
 brates (crustaceans and mollusca) can be  compared with values given for
 zooplankton, mollusc muscle and  crustacean muscle in the NAS/NRC report.
 The latter data indicate two additional elements  (ruthenium and aluminum)
with critical CF's which were not shown in the LLL data.
                                    13

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         TABLE 2.  COMPARISON OF CRITICAL  CONCENTRATION FACTORS FROM
                   DIFFERENT SOURCES—MARINE ANIMALS (VALUE LISTED X
                   103 = CF)
Element
P
Fe
Zn
Ge
Cd
Te
Hg
Sc
Mn
Ta
Tl
Po
Ru
Al
Thompson et al. (1972)
Marine Invertebrates
(a)
Derived v '
28.6
20.0
100.00
16.7
250.0
150.0
33.3
10.0
10.0
16.7
15.0
20.0
2.0
0.06
Average
Measured
30.0
—
50.0
—
—
—
—
—
0.4
—
—
3.0
0.1-1.0
_— .
NAS/NRC C197
Zooplankton
13.0
25.0
8.0
	
—
—
—
1.0
1.5
—
—
—
34.0
9.0
Mollusca
6.0
9.6
11.0
	
—
—
	
—
12.0
	
—
—
0.003
12.0
•>
Crustaceans
24.0
2.4
2.0
	
	
	
	
0.3
1.9
	
—
—
0.1
10.0
       Dash (—) indicates no data in reference cited.
       (a)r
       (b)
Derived on the basis of stable element  concentration.
Average of values  from radioisotope studies.
     Critical CF's  for marine organisms from the literature reviewed are
listed in Tables 3,  4, and  5; those for freshwater organisms are listed in
Tables 6, 7, and 8.  Although much data exists in the literature, very little
has come from environmental studies with radionuclides.  The most compre-
hensive list of CF's found  is contained in the LLL report  (Thompson.@t al.3
1972).  These data  resulted from a multi-year effort which is continuing
to update and extend the  data base.  This effort is part of a project which
has the objective of assessing the radiation dose to people from radio-
nuclides released to aquatic environments.  The dose model being developed
will be discussed later.

     Harrison (1967) suggests that there are two classes of analytical
techniques used to  determine CF's, a distinction which was also incorporated
into the LLL report by Thompson et al.  (1972).  These two classes are:
                                     14

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     1.   CF's obtained  from measurements  of stable element concentration
          in the organisms and water and
     2.   CF's obtained  from measurements  of the radionuclide content
          of the organisms and water.
Theoretically, the CF values obtained  by  these two methods should be
identical,  but in practice, both methods  are subject  to  sampling and
analytical  errors.  Jinks and Eisenbud (1972)  describe several sources of
variability in reported values for CF's,:
          TABLE 3.  MARINE PLANTS—CRITICAL CONCENTRATION FACTORS
                     (VALUE LISTED X 103 = CF)
Element
N
Sc
MH,
Fe
Y
Zr
In
La(e)
Hf
Tl
Bi
P
Pb
Pu
Sr
Cs
U
I
Chapman
at al. (1968)
10.0
10.0
10.0
50.0
10.0
10.0
100.0(d)
10.0
10.0
100.0
—
—
	
1.0
0.013
0.02
1.0
4.0
Thompson & t al. (1972)

Derived ^
10.0
100.0
20.0
50.0
10.0
10.0
—
—
—
—
—
	
0.35
0.013
0.02
0.067
4.0
Measured
_ _
—
5.5
0.73
—
—
--
—
—
—
—
	
1.0
0.01
0.05
—
1.0
For Contaminated Environment 1CJ
Minimum
__
—
5.5
	
—
—
—
—
—
—
0.21
	
0.77
0.009
0.01
—
—
Maximum
__
—
25.0
__
—
—
—
—
	
—
22.0
__
3.5
0.2
0.17
—
—
Average
	
—
—
	
._<_
—
—
—
	
—
4.0
5.0-10.0
3.0
0.025-0.04
0.04-0.07
—
1.0
        Dash (—) indicates no data in reference cited.
          Derived on the basis of stable element concentrations.
        (b)
        (c)
        (d)
        (e)
Measured in radioisotope studies.
Measurements made  in environmental studies.
No data available, estimate based on worst possible case.
For lanthanide series.
                                      15

-------
TABLE 4. MARINE INVERTEBRATES—CRITICAL CONCENTRATION
FACTORS (VALUE LISTED X 103 = CF)
Element
M
P
Fe
Zn
Ge
Cd
In
Sb
Te
Hg
Bl
Sc
Mn
Ta
Tl
Po
Pu
Sr
Cs
U
I
Chapman
BE al. (1968)
17.0
28.6
20.0
100.0
16.7
250.0
100.0
16.0
—
100.0
—
1.0
5.0
0.1
150.0
0.4
0.286
0.006
0.02
0.33
0.05
Thompson 3 t al. (1972)
Derived
-------
TABLE 6. FRESHWATER PLANTS—CRITICAL CONCENTRATION FACTORS
(VALUE LISTED X 103 = CF)
Element
N
P
Sc
Mn
Y
Zr
In
La(d)
Hf
Tl
Sb
Zn
Ru
Ce
Pu
Sr
Cs
U
I
Chapman
et al. (1168)
25.0
100.0
10.0
10.0
10.0
10.0
100.0
10.0
10.0
100.0
—
4.0
2.0
10.0
1.0
0.5
0.2
1.0
0.1
Thompson et al. (1972)

(al
Derived v '
12.5
10.0
10.0
10.0
5.0
1.0
__
5.0
1.0
__
1.5
1.0
0.2
5.0
0.35
0.5
0.08
1.0
0.04
Measured

500.0
—
10.0
—
—
__
—
—

—
20.0
2.0
4.0
—
0.5
0.5
0.0005
—
For Contaminated Environment (c)
Minimum

100.0
—

—
—
__
—
—

—
—
1.8
2.0
—
0.24-0.33
0.07-0.47
0.0004
—
Maximum
„
850.0
—

—
—
__
—
—

—
—
12.0
10.0
—
0.28-0.69
0.87-1.2
0.0007

Average
_.
270.0,
—
—
—
—

—
—

—
130.0