Tritium in Some Typical Ecosystems

TECHNICAL REPORTS SERIES No. 207

Tritium in Some Typical Ecosystems

H INTERNATIONAL ATOM IC ENERGY AGENCY , V I ENNA, 1981

TRITIUM IN SOME TYPICAL ECOSYSTEMS

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© IAEA, 1981

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Printed by the IAEA in Austria April 1981

TECHNICAL REPORTS SERIES No. 207

TRITIUM IN SOME TYPICAL ECOSYSTEMS

FINAL REPORT OF A FIVE-YEAR IAEA CO-ORDINATED RESEARCH PROGRAMME

ON THE ENVIRONMENTAL BEHAVIOUR OF TRITIUM

INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 1981

TRITIUM IN SOME TYPICAL ECOSYSTEMS IAEA, VIENNA, 1981

STI/DOC/10/207 ISBN 9 2 - 0 - 1 2 5 1 8 1 - 5

FOREWORD

Tritium is a radionuclide of great interest. Through the development of nuclear power it will be released in increasing quantities. Because of its radio-active half-life (12.26 years), its global distribution pattern and its direct incorporation into water and organic tissues, it is inserted in ecological cycles.

This report presents the data obtained in a co-ordinated research pro-gramme organized by the IAEA from 1973 to 1978. Eleven laboratories, working together during the five years, were involved in the study. The IAEA staff members P.J. West (1973-75) and L. Farges (1975-79) acted as the Scientific Secretaries of the programme. The report provides new specific information on tritium, supplementing that disseminated by the IAEA/NEA Symposium on the Behaviour of Tritium in the Environment held from 16 to 20 October 1978 in San Francisco.

At a consultants' meeting held in November 1970 to advise the IAEA on its programme in regard to the environmental aspects of tritium releases, the participants recommended that the Agency should encourage a co-ordinated research programme on this subject. Another meeting (April 1972) discussed the practical aspects of the programme and a technical visit was organized in the Philippines, Thailand, India, Greece and Mexico to consider the analytical problems. Standardized techniques were recommended, and the first results were presented in a co-ordination meeting at Livermore and Las Vegas, United States of America (December 1973). A revision of the plans was made in Mol, Belgium (April 1975), and the proposal to publish the results of the programme was made at the third co-ordination meeting in Helsinki and Kaamanen, Finland (June 1976).

A draft report was prepared by two consultants (R. Kirchmann, Belgium, and J.J. Koranda, United States of America) and discussed at the final meeting of the co-ordinated research programme held in Guanajuato, Mexico (October 1977). The report was completed during 1978-79, taking into account more recent data resulting from the programme.

It is hoped that the unique data produced by the various laboratories participating in the programme will allow the users (health physicists, radio-ecologists, radiobiologists and environmentalists) to predict the behaviour of tritium in the major terrestrial ecosystems of the world.

The IAEA gratefully acknowledges that the co-ordinated research pro-gramme which resulted in the preparation of this publication was partially funded by the United Nations Environment Programme (UNEP) under its Project No. 0102-74-002 with the IAEA.

CONTENTS

1. PURPOSE OF THE PROGRAMME 1

2. ORGANIZATION OF THE PROGRAMME 3

2.1. Role of participating laboratories 3 2.2. Methodology 4

3. EXECUTION OF THE PROGRAMME, RESULTS AND DISCUSSION 13

3.1. Transfer and incorporation of tritium in aquatic organisms 14 3.2. Soil studies 29 3.3. Terrestrial plants 40 3.4. Transfer and incorporation of tritium in mammals 55

" 3.5. Deposition on soils from tritiated atmospheric effluents 66

4. PREDICTIVE MODELS OF TRITIUM BEHAVIOUR 69

4.1. Movement of tritium in the environment 69 4.2. Tritiated water in soil 72 4.3. Compartmental model for tritium persistence in the soil-plant

system 74 4.4. Transport in plants 76

5. CONCLUSIONS AND NEEDS 79

5.1. Overall conclusions 79 5.2. Future needs 79

6. ANNEXES 81

6.1. List of laboratories and project titles 81 6.2. Tables 83 6.3. Scientific and common names of the investigated plants 96 6.4. Scientific and common names of the investigated animals 98 6.5. Glossary 98

7. BIBLIOGRAPHY AND REFERENCES 101

7.1. General '01 7.2. Aquatic • 1° 7.3. Soils 112 7.4. Plants 114 7.5. Terrestrial animals 115 7.6. Modelling H 6

1. PURPOSE OF THE PROGRAMME

There is considerable interest in the behaviour of radionuclides of global character that may be released to the environment through the development of nuclear power. Tritium is of particular interest as it is directly incorporated into water and organic tissues.

Although reviews of global distribution patterns of tritium have been reasonably well established by such programmes as the joint IAEA/WMO world monitoring project, there has been a most serious lack of knowledge in regard to local ecological cycling of tritium, such as rates of transfer from one compart-ment of the environment to another, and of incorporation into organic tissues. Indeed the Symposium on the Detection and Use of Tritium in the Physical and Biological Sciences (Vienna, 3—6 May 1961) was devoted in its first part to the use of tritium in hydrology, physics and chemistry, and in its second part to the biological applications of tritiated compounds and the radiation effects of tritium on living organisms. Ten years later, a few papers dealing with certain environmental aspects of tritium were presented at the Tritium Symposium held from 28 August to 3 September 1971 in Las Vegas, Nevada, United States of America. As stated in J.J. Koranda and J.R. Martin's paper, 'only a few ecological studies addressing themselves to the partitioning of a tritium pulse in an entire ecosystem have been conducted. Also, few crop plant studies of tritium uptake under field conditions have been conducted and these data are needed for critical evaluation of many nuclear projects and operations'.

The aim of the IAEA co-ordinated research programme was precisely to obtain information on the residence-time, pattern of movement and distribution of tritium in typical ecosystems in order to determine the persistence and biological significance of this radioisotope under various natural conditions.

It was expected that the critical phase of the research project would be carried out over a period of three years. In fact, the project lasted five years, during which studies were made concurrently in the following typical ecosystems: tropical rain forest, savannah or hot grassland, temperate grassland or woodland, prairie and tundra.

Both laboratory and field experiments have been carried out, and in the initial stage these were designed to determine the residence time of tritium in each phase of the ecosystem (e.g. soil-plant-atmosphere), and also transfer rates between the different compartments under various conditions.

1

2

As a later phase of the project, laboratory and field experiments were also conducted, where facilities were available, to investigate the rate and degree of incorporation from a water substrate into the organic components of tissue. In this connection, experiments on domestic animals and aquatic organisms, important source of human foods in certain parts of the world, have been performed.

2. ORGANIZATION OF THE PROGRAMME

2.1. ROLE OF PARTICIPATING LABORATORIES

In order to fulfil the aims of the programme — the formation of a general picture of the behaviour of tritium in the environment — the role of the laboratories was, using a common methodology, to carry out a variety of projects in widely varying biomes from tropical to arctic regions.

In Belgium, studies on terrestrial food chains dealt with deposition of tritiated water on crops and pasture, the transfer of tritium to the grazing animals (cows) and their products (milk). Investigation on tritium transfer from drinking water and feeds (hay, milk powder, potatoes) to animals (cows, calves, goats, pigs) were conducted in an experimental stable. Studies were made on the transfer of tritium in the major components of an aquatic environment receiving the discharges of liquid wastes released from complex nuclear installations. Some special aspects were also studied: incorporation of tritium in macromoleeules (proteins, nucleic acids) of plants and animals; cytogenetic study on ruminants after ingestion of various amounts of tritium.

In Finland, plots of pasture and forest were labelled by HTO in the form of a simulated single rain. Tritium penetration into soil and retention in the soil column as well as tritium activity present in volatile and non-volatile form in the vegetation growing on the plot were followed during four years. In a separate experiment, uptake of tritium from HTO and incorporation into DNA, free amino acids and the total organic matter of growing pea seedlings were determined after two and five weeks of growth in soil watered by THO.

In France, the purpose of the studies was to determine in mediterranean climate the relationship between the content of tritium in water and in different parts of three plants (grape vines, orange trees and olive trees). These tests were completed by injections of tritiated water into the trunks of trees. Other studies dealt with the effects of technological procedures on tritium levels in processed foods.

In the Federal Republic of Germany, within the framework of the com-prehensive measuring programme carried out in Karlsruhe, the contamination, as a consequence of the tritium releases of the Nuclear Research Center, was investigated in its immediate and more distant environment. These contaminations are mainly caused by the release of tritiated water vapour to the atmosphere via several exhaust stacks. Tritium concentration of precipitations, surface, ground and drinking water as well as in the tissue water of plants was measured.

In India, determination of mean residence times of tritium in a number of tropical trees was completed on the.basis of field experiments. A generalized • model for understanding the different incorporation modes of tritium (free water organic components) was investigated on the basis of experimental data. Uptake

3

4 ORGANIZATION OF THE PROGRAMME 4

and release patterns of tritium in a number of aquatic organisms were studied, and the tritium pathways in the organic fractions identified. Tracer applications of

In Mexico, studies on tritium persistence as free-water tritium and tissue-bound tritium in crops after an acute application were carried out. Tomatoes were sown on the same experimental plot. Free-water tritium as well as tissue-bound tritium was determined during the growth cycle of maize, bean, wheat and tomatoes. Organically bound tritium was also determined in corn fractions (fats, proteins and carbohydrates) and in wheat fractions (flour, germ and bran).

In the Netherlands, tritium metabolism in ruminants was studied in young calves and in adult, lactating cows. Tritium was administered as tritiated water and in organically bound form. Several biological parameters (transfer to milk, biological half-time) were determined.

In the Philippines, the residence time of tritium in soil and various commonly edible crops was determined using the freeze-drying technique. The excretion rate in some animals was also studied.

In Thailand, the behaviour of tritium as tritiated water was studied to determine the half residence time in soil and local vegetation. The experiment was conducted by spraying a known amount of tritiated water on the experimental plots. Soil and plant samples were collected and analysed for tritium concentra-tions.

In the United States of America, field experiments were conducted in a five-hectares field located at the Livermore Laboratory and at selected sites available through co-operative studies agreement in other climatic regions. Studies in the desert woodlands of South Nevada, in tropical trees on a rural atoll in the S.W. Pacific and on the arctic tundra of Northern Alaska were carried out. Two modes of exposure were used: THO vapour exposure and THO liquid exposure. Some of these experiments were accompanied by detailed micrometeorological measurements, and these data were compared with the radiotracer results to determine the real water and tritium flux in ecosystems. Rates of organic fixation of tritium by plants exposed singly and with multiple exposure were also determined. Several studies have also been conducted in Las Vegas to determine the biological half-life and appropriate concentration factors of tritium in animals after administration of HTO and the behaviour of HTO and HT in plants.

2.2. METHODOLOGY

2.2.1. Application of tritium

The manner of introduction of tritium into the test environment or population is determined by the form of tritium being used, and to some extent

ORGANIZATION OF THE PROGRAMME 5

by the kinds of organisms or plots being exposed. The forms of tritium generally used are:

(i) Gaseous or vapour (a) Elemental tritium gas (T2) (b) Tritiated methane gas (CH3T) (c) Tritiated water vapour (THO)

(ii) Liquid (a) Tritiated water (THO) (b) Organic compounds, tritiated (R-CH2T) (c) Tritiated inorganic compounds or solutions

In general the volatile nature of the gaseous forms of tritium, for either experimental or safety reasons, implied a closed system or 'glove box'-type of facility for exposure of the test populations. It is possible that uncontrolled field releases of elemental tritium gas could be made for experimental purposes, but this has not been done purposely to our knowledge. The difficulty with such exposure modes always resides in the inability of the experimenter to determine the actual exposure received by the organism or test plot. In an enclosed exposure facility, the actual air concentration may be determined easily by whole air samples or complexing a known volume of the air in a solution.

Application of liquid forms of tritium, usually THO, is preferably carried out during cool, calm weather, e.g. in the evening, in the form of simulated rain. Evaporation losses during application can thus be kept low.

Environmental studies of tritium in the neighbourhood of a nuclear installations from which accidental releases of tritiated water into soil and atmosphere have taken place have also been performed.

2.2.2. Sampling

Sampling of a test population or plot is usually part of the experimental protocol and may be accomplished in several ways, some of which are determined by the characteristics of the test organisms. The sampling mode should be designed to avoid any possible bias in the selection of samples. In field experi-ments, the usual source of bias lies in the edges of the experimental area where organisms may be subject to unintentional gradients of exposure or growth conditions. The experimental area therefore should be designed with this in mind, and adequate organisms and area provided to allow sampling well within the exposed area. For field-grown crop plants, at least 0.5 metres on all sides should be provided and more if possible.

In crops grown in rows or even in heterogeneous pasture vegetation, the experiment is usually found to yield data with lower variability if the sampling is carried out in an integrated mode. By 'grazing' a sample in this integrated

6 ORGANIZATION OF THE PROGRAMME 6

sampling method, it is possible to represent the status of the entire plot at each point in time, rather than by harvesting entirely the organisms in small sub-plots within the larger exposed area. There is apparently considerable variation in the behaviour of plants within small experimental areas and one should attempt to minimize this by population or integrated sampling rather than totally harvesting sub-plots.

Soil sampling of necessity is destructive although soil-water lysimeters can be designed and installed in experimental areas and will obtain adequate samples of the soil-water for tritium analyses. Soil cores are typically taken from field plots and interstitial water is extracted by vacuum or azeotropic distillation. These cores, if small enough, can also be taken in an integrated manner, several from the plot at each sampling time, and bulked or combined for analysis, or kept separate to determine horizontal variability within the plot. Cores used in this way should be as identical as possible.

Access tubes can be placed horizontally or vertically in the soil profile and the soil water can be distilled from the soil by pumping the air from the tube through a dry ice trap. This method gives only quantitative data on the soil-water tritium concentration whereas soil coring provides both water content and tritium concentration.

Samples of aqueous cultures or similar experimental media are usually obtained on a random 'grab' basis which is determined by the form of the culture. Planktonic algae and micro-organisms are usually pipetted from the basic culture medium whereas macroscopic organisms such as fishes, filamentous algae and larger invertebrates can be sampled by taking several sub-samples that are bulked for a single analysis. The dominant theme in all sampling of either laboratory or field experimental systems should be to obtain as representative a sample as possible from the system at each point in time. The system itself exerts a strong influence upon how difficult it is to obtain a representative aliquot of the sample population. One can readily see the difference in sampling efforts required for body-water studies of a water buffalo contrasted with those required to sample corn growing in a 5-h field.

2.2.3. Measurements

The tritium measurements involved Collection, processing and counting samples of different kinds such as soils, biological and plant tissues, tritiated compounds in different biochemical and inorganic forms or aqueous and gas phases.

The analytical procedures of the sample-dispensing techniques, although they varied from one laboratory to another, the general extraction procedures involved standard techniques of vacuum distillation, azeotropic distillation, wet and dry combustion, solubilization and.suspension counting. Depending upon the varied

ORGANIZATION OF THE PROGRAMME

TABLE I. STUDY No. 1: TOTAL TRITIUM

7

Country code Number of Concentration Counting error Replication Deviation from analyses (n) (Xj) (2 standard (2 standard grand average (%)

deviations) deviations)

B 1 7.840 n a / g 0.31 nCi/g as received as received

field conditions and special nature of samples a number of new techniques were evolved by the various laboratories.

In almost all the laboratories, liquid scintillation spectometers of various makes were used for tritium counting. The quenching corrections were effected by the internal spike method, channels ratio or automatic external standardization techniques. The total amount of samples and type of scintillator cocktails used varied widely. However, there was general statistical and counting accuracy agreement in aqueous and gas phase measurements.

In the case of organically bound tritium, because of the special nature of sample preparation and counting, it was felt necessary to initiate a reference intercomparison technique, detailed results of which are given in the next section.

2.2.4. Intercomparison studies

The aim of the programme was to obtain quantitative information on the residence time and pattern of movement of tritium in typical ecosystems. To determine the biological significance of tritium under various climatic conditions, comparisons of data were obtained from similar experiments in different ecosystems. It was recognized during the Second Co-ordination Meeting that some type of intercomparison study for measurement of organically bound tritium should be made. The U.S. Environmental Protection Agency's Environ-mental Monitoring and Support Laboratory, Las Vegas, Nevada, agreed to prepare alfalfa samples that were uniformly labelled with tritium.. This was accomplished by growing alfalfa plants in a special greenhouse in which tritiated water was the sole hydrogen source. Organically bound hydrogen was the result of all synthetic reactions since the plants were grown in a uniformly labelled environment in terms of soil-water, plant-water and atmospheric water vapour. Also important is the fact that this uniformly labelled environment was constant throughout the entire growth period. The plants were periodically harvested, dried, ground and thoroughly mixed. The ground alfalfa was hydrated, dried, and rehydrated


TABLE II. STUDY No. 1. ORGANICALLY BOUND TRITIUM

nCi/g water Country code Number of Concentration Counting error Replication Deviation from

analyses (n) (X|) (2 standard (2 standard grand average (%) deviations) deviations)

A 1 8.69 0.16 - + 5

B 8.49 8.55 8.58 8.53

4 Av. = 8.54 0.04 0.43 + 3

C 1 9.27 0.60 - + 12

D (re-run) 8.71 0.17 8.76 0.17 8.64 0.17

Av. = 8.70 - 0.06 + 5

E 1 6.76 0.31 - - 18

F - - - - -

G 1 8.41 0.16 - + 2

H

1 8.61 0.18 - + 4

7.83 8.18

8.41 6.70 7.66

5 Av. = 7.76 - 0.66 - 6

2n = N = 17

NOTE:

Grand average = [ S j l , X| ] ^ (N) = x = 8.28 nCi/g

/s,"(X i-Av.)2

T n - 1 Replication (2 standard deviations) = 2

Where X, = individual concentrations Av. = individual laboratory average n = number of analyses performed by laboratory

% Deviation from grand average = [(Av. — x) t x] x 100%

— = value not reported or unknown.


three times to equilibrate easily exchangeable bonding sites with hydrogen (i.e. RC-OT RC-OH). This resulted in a more stable sample. The first set of samples was distributed to each laboratory participating in the programme in March 1976. Each laboratory was requested to analyse the sample utilizing its own laboratory procedures for organically bound tritium, non-organically bound and total tritium concentrations.

At the third Co-ordination Meeting it was decided that a second set of samples should be sent to the laboratories participating in the programme. This second set of samples was sent to the participating laboratories in October 1976. This set of samples was produced under a different set of conditions in the special greenhouse than that of the first set. In addition, there was approximately a one-year time interval between preparation and analysis of the second set. The corresponding interval in the first set of samples was approximately two months.

2.2.4.1. Discussion

The original design of the studies called for ten laboratories to analyse three samples each at two levels of activity for organically bound (analysis 1), non-organically bound (analysis 2) and total tritium analyses (Table I). In both studies seven laboratories returned data for the first analysis. One laboratory returned data for analyses 2 and 3 for the first study and only analysis 2 for the second study. No data were reported for analysis 3 in the second study. In general, because of the small amount of data available, no definite statistical conclusions'could be made about these studies.

In the first study (Table II) the grand average calculated for organically bound tritium was 8.28 nCi/g dry weight. For study number two (Table III) the value was 3.09 nCi/g.1

A value of 1.14 nCi/g non-organically bound tritium was reported by one laboratory for the first study (Table IV). In the second study (Table V) one laboratory reported 0.99 nCi/g for that analysis. It is surprising to note that, although the concentration of tritium in the total sample varied by more than a factor of 2.5 for the two studies, the tritium concentration in the non-organic portion remained relatively constant.

Many of the laboratories reported only one replicate for the first study; therefore, the replication error and the deviation of the result from the grand average are not presented.

Although most laboratories reported more than one result from the second study, as well as more information on their actual procedures, missing data allows only the presentation of the same parameters given for the first study. Sample replication error was calculated where feasible. The organically bound tritium

1 1 Ci = 3.70 X 1010 Bq.

10

TABLE III.

ORGANIZATION OF THE PROGRAMME

STUDY No.2: ORGANICALLY BOUND TRITIUM

nCi/g dry weight -Country code Number of Concentration Counting error Replication Deviation from

analyses (n) (X;) (2 standard (2 standard grand average (%) deviations) deviations)

A 16 4.38 0.10 (reported) 16 3.27 - 0.08 (reported) 16 3.12 - 0.07 (reported)

48 Av. = 3.58 - - 16

B 3.30 3.31 3.26

3 Av. = 3.29 0.08 0.05 + 6

C 2.60 0.08 2.30 0.07 2.54 0.08 2.17 0.07

4 Av. = 2.40 0.41 - 2 2

D (re-run) 3.08 0.06 3.34 0.07 3.17 0.06

3 Av. = 3.20 - 0.26 + 4

E 10 2.56 0.04 0.15 10 3.25 0.11 0.39 10 2.54 0.05 0.20 10 2.97 0.04 0.15

40 Av. = 2.83 0.38 - 8

F - - - -

G 3.08 3.16 3.06 3.13 3.07 3.07 3.12 3.05

8 Av. = 3.09 - 0.04 0

H - - - -

I - - - -


TABLE III. STUDY No.2: ORGANICALLY BOUND TRITIUM (Cont.)

Country code Number of analyses (n)

Concentration ( X i )

nCi/g dry weight -Counting error (2 standard deviations)

Replication (2 standard deviations)

Deviation from grand average (%)

J 3 . 0 7 0 . 0 4

3 . 1 3 0 . 0 5

3 . 0 7 0 . 0 4

3 Av. = 3 . 0 9 0 . 0 3 - 0

K

9

3 . 2 8

3 . 2 6

3 . 2 9

3 . 2 7

3 . 1 7

3 . 3 5

3 . 4 6

3 . 4 6

2 . 9 0

3 . 1 4

Av. = 3 . 2 4 0 . 1 6 5

Grand average = 3.09 nCi/g

TABLE IV. STUDY No. 1: NON-ORGANICALLY BOUND TRITIUM

Country Number of Concentration code analyses (n) (X;)

Counting error Replication (2 standard (2 standard deviations) deviations)

Deviation from grand average (%)

1.140 nCi/g H 2 0

1.143 nCi/g H 2 0

Av. = 1.142 nCi/g H 2 0 0.040 nCi/g H 2 0 0.002 nCi/g H 2 0

results for the first study indicated a variation ranging from - 18% to + 12% deviation from the grand average. In the second study the range was - 22% to + 6%. The range of deviation from the grand average was about the same magnitude for both studies, even though the concentrations of tritium were different.

It was interesting to note that if a laboratory reported a value with a positive or negative deviation from the grand average in the first study it did not generally have the same positive or negative deviation in the second study. This

O R G A N I Z A T I O N O F THE PROGRAMME 12

TABLE V. STUDY No.2: NON-ORGANICALLY BOUND TRITIUM

nCi/g water Country code Number of Concentration Counting error Replication Deviation from

analyses (n) (Xi) (2 standard (2 standard grand average (%) deviations) deviations)

A 4 0.98

4 1.03

4 0.98

12 0.99 - 0.032 -

may indicate that the differences in the analyses were due to random rather than systematic errors.

In summary, the two studies were undertaken to determine the comparability of various laboratories to analyse organically bound tritium in vegetation. The studies show a variability among laboratories of approximately ± 20%. In an effort to measure the performance of the laboratories in these studies the requirements of the U.S. Environmental Protection Agency's Radiation Quality Assurance Program2 were employed. In the Tritium in Water Laboratory Inter-comparison Study of the Program a + 20% laboratory variability is expected for concentrations exceeding 4 nCi/litre. Since it is more difficult to analyse for tritium in vegetation than in water, the results from these intercomparison studies compare favourably with the EPA requirements.

2 EMSL-LV, U.S. EPA, Las Vegas, Nevada 89114, United Statesof America.

3. EXECUTION OF THE PROGRAMME, RESULTS AND DISCUSSION

The general methodology has been discussed in the preceding chapter; this chapter describes the actual methods used by the different laboratories involved in the programme.

The programme of research on tritium behaviour in the environment was executed in the co-operating laboratories with a variety of methods determined by the available resources and personnel, and to some extent by the environment in which the studies were being conducted. In general, the applica-tion of tritium in the experimental system and the analysis of tritium in the laboratory was quite similar. Tritium was introduced into the experimental area by a spraying device to create a uniform deposition of activity per unit area. Small pressurized tank sprayers or manual sprinklers were used on plots of areas of a few square metres. In Belgium, where larger areas were studied, irrigation-type sprinklers were used with good success. Sprinklers were also used in France where fruit trees were exposed.

Tritium was also injected into the stems of plants and trunks of trees to generate data on evapotranspiration rates, mean residence times, peak arrival times and biomass estimation. Also, in certain cases, the root-soil was irrigated with tritiated water.

Soil-water and plant-tissue-water were typically extracted by vacuum distil-lation, or freeze-drying (lyophilization). One or two laboratories used azeotropic distillation with benzene because it was more convenient in their location. The analysis of organically bound tritium was accomplished by a variety of combustion systems ranging from the conventional quartz tube furnace with flowing oxygen to the Schoniger closed-flask method. A semi-automated biological material oxidizer (ICN Tracerlab) and an automatic tritium oxidizer (Packard) were also used for organically bound tritium analyses.

Aquatic plants and animals were studied under natural environmental as well as in laboratory conditions. In the case of natural environmental conditions, plants and animals grown in contaminated water were periodically sampled for investigations on tritiated water and organically bound tritium content. Aquatic plants and animals reared in laboratory aquaria under controlled conditions were studied for uptake and release patterns of tritium.

Tritium in the distilled water or combustion water samples was assayed in all laboratories by liquid scintillation counting. This rapid and efficient method of tritium assay has made possible the types of ecological tracer studies described here. Without such a method it would be impossible to analyse the large number of samples typically generated in ecological experiments.

13

14 EXECUTION OF THE PROGRAMME

The data presented in the following sections were obtained primarily in experimental studies of tritium behaviour in natural ecological or agricultural conditions. Most of these experiments were conducted in the field under uncontrolled conditions and were affected by unmodified parameters of the climate. They truly represent real-world conditions and realistic behaviour of tritium under a wide range of environments. Although each co-operating laboratory did not set out to conduct a standardized experiment, during the course of this programme there is a considerable amount of continuity and relationship between these data produced independently in many parts of the world. The data may be directly compared in many cases and the tables in the Annexes will demonstrate this.

Tritium uptake patterns through foliage were investigated under controlled tritiated environment. Also the contamination of the environment by releases of tritiated water vapour and tritium-containing wastewater from nuclear facilities was investigated.

Various kinds of animals were studied in this programme to provide basic data on tritium oxide metabolism by the agricultural animal. Cows, goats, pigs, fishes and various invertebrates were studied as well as the conventional laboratory animals, rats, mice and rabbits. A water buffalo experiment was attempted in the Philippine Islands and a small foodfish, Tilapia mossambica, was studied in India.

3.1. TRANSFER AND INCORPORATION OF TRITIUM IN AQUATIC ORGANISMS

As aquatic ecosystems in certain parts of the world may be an important source of human foods, research projects concerned with aquatic organisms have been encouraged where marine- and freshwater laboratory facilities were available. Aquatic plants and animals reared in laboratory aquaria under controlled con-ditions were studied for uptake and release patterns of tritium; these laboratory experiments were conducted in Belgium, India and the United States of America.

The ecosystem study involves a small river in which the liquid wastes from a number of nuclear facilities, located in Mol (Belgium), are released. The tritium in effluents was in both water and organic forms. The whole aquatic environment has been prospected and samples have been collected and measured, especially for the tritium incorporated in the organic matter.


3.1.1. Studies performed under laboratory conditions

3.1.1.1. HTO exposure of freshwater plants

(a) Experimental conditions

In the Lawrence Livermore Laboratory, Harrison and co-workers [7.2.1]3

maintained cattails (Typha angustifolia L.) and filamentous algae (Pithophora sp.) in an experimental pool containing tritiated water (initial concentration 80 /uCi/ltr); the concentrations of tritium were determined for eight months in the pool water and in the water and organic matter of the tissues of the organisms.

In other participating laboratories, Scenedesmus obliquus [7.2.2., 7.2.3], Hydrilla verticillata[l.2.4] and Chlamydomonasreinhardi [7.2.5] were grown in their respective media with different tritium concentrations (range 0 . 0 5 - 5 0 /LiCi/ml); the exposure time of the algae in the active media varied from 12 days to 42 days in order to determine the period of time required for effective tritium transfer between the two main hydrogen pools of the system: plant-water and the organic fraction in the plant. The chemical procedure employed to study the distribution of tritium in different organic constituents of Scenedesmus has been described by Krishnamoorthy and co-workers [7.2.2].

(b) Results and discussion

(i) Tritium in the Free Tissue Water (TFWT)

The TFWT of he rhizomes and leaf bases of cattails reached 65 to 70% of the tritium concentration of the pool water during the eight months of the experiment, the lack of equilibrium being attributed to exchange with atmospheric water by the leaves. On the contrary, in the filamentous algae the TFWT concentration was approximately the same as that of the pool water, the value of the ratio being 1.02.

Similarly, in Scenedesmus experiments [7.2.2], the tritium specific activity (tritium/hydrogen) of TFWT was always close to that of environmental water, the values ranging between 0.94 to 1.09.

The rate of uptake and release of tritium for short intervals of time was also investigated [7.2.4]: Hydrilla verticillata reached an equilibrium concentration corresponding to 80% of the medium water concentration, when normalized for moisture content of the plant (0.76 w/w), within a period of one hour. The release pattern showed three components as per least-square fit; the mean residence time corresponding to TFWT phase was 0.36 h and the rate of uptake can be calculated as 0.028 ml/min per g.

3 The references will be found in Chapter 7, where the References and Bibliography

are listed under the headings: General, Aquatic, Soils, Plants, Terrestrial Animals, and Modelling.


TABLE VI. DISTRIBUTION OF TBT IN DIFFERENT ORGANIC FRACTIONS EXTRACTED FROM Scenedesmus [7.2.2]

Solvents Scenedesmus extraction

at room temp. (%)

Remarks

Lipid extraction 58.3 Mostly lipids pigments and

(acetone, CHC13 fatty acids

and CH3OH)

Ether ND Ether soluble substances

80% ethanol 1.1 Mostly free amino acids

and carbohydrate

6N HC1 34.0 Protein hydrolysate

Residue 6.6

(ii) Tissue-Bound- Tritium (TBT)

The specific activity of the organically bound tritium in cattail tissues was less than that of the pool water (40 to 65%); no strong relationship was apparent between the plant part and the level of TBT. The ratios of TBT to TFWT were also less than unity (0.62 to 0.99) except for the rhizomes where it was about unity. In the filamentous algae, the specific activity of the TBT was about the same as that of the water and the ratio of TBT to TFWT was essentially unity. Thus, the algae appeared to be in a steady state of uptake and loss of tritium with the water, which might be excepted in a short-lived simple organism [7.2.1 ]. Likewise the values of the ratio of the specific activity of TBT in Scenedesmus obliquus to the medium water were respectively 0.91 [7.2.3] and 0.67 [7.2.2] in algae exposed during 20 days to an active medium.

Data reported by Bonotto [7.2.5] demonstrate that when Chlamydomonas algae are cultured in the presence of tritiated water, the amount of 3H incorporated in the organic matter is related to its concentration in the culture medium, whereas the concentration factor (juCi/g dry weight: juCi/ml medium) remained constant around 0.40 for Scenedesmus and Chlamydomonas. The nature of the organic compounds into which 3H is incorporated in Chlamydo-monas remains to be studied.

The relative fractions of tritium incorporated in the three phases of the bound and free forms of tritium in the aquatic plant Hydrilla verticillata [7.2.4] were found to be 100:3.27:0.77. This shows that 3.27% of tritium is in the labile TBT form and 0.77% is in the non-labile TBT form; these values agree well with those obtained by Bruner [7.2.6],


0 . 5 -

/ . . o /

v> —-o

5 1 0 15 2 0

T i m e o f e x p o s u r e ( d a y s ) in t r i t i a t e d w a t e r

FIG.l. Incorporation of 3H in the dry matter of green algae, Ulva lactuca

(I Ci = 3.70X1010 Bq).

FIG.2. Penetration of3H in red algae, Porphyra sp., and incorporation in the dry matter (ICi = 3.70 X 10l° Bq).

The sequential solvent extraction procedure has been used to study the distribution of tissue-bound tritium in the various classes of organic constituents of the Scenedesmus obliquus cells. The results (Table VI) show all constituents to be significantly labelled. The relative specific activity ratio (RSA) calculated with respect to medium concentration indicates that greater proportions of hydrogen atoms were labelled in nucleic acids compared with lipid and protein fractions, the mean RSA values being respectively 1.13:0.56:044 [7.2.2 J.


3.1.1.2. HTO exposure of marine plants


Four species of marine algae have been used in the participating laboratory in Belgium: Acetabularia mediterranea, Dunaliella bioculata, Porphyra sp. and Ulva lactuca. The two first species were grown in the laboratory [7.2.7, 7.2.8]; the others, on the contrary, were harvested on the North Sea beaches and maintained in culture in the presence of chloramphenicol (10 Mg/ml) to avoid the growth of marine bacteria. The exposure time of these algae in the active media varied from two days to 27 days and the tritium concentration in seawater was about 0.03 juCi/ml.

DNA was prepared by phenol extraction as described by Heyn and co-workers [7.2.9] or by pronase treatment as reported by Lurquin and co-workers [7.2.10]; sepharose-sieved DNA has been analysed for its buoyant density by ultracentrifugation in CsCl gradient, in the presence of marker DNAs (Clostridium perfringens: p = 1.691 g / c m 3 ; Streptomyces coelicolor: p = 1.730 g/cm3). Tritiated DNA was precipitated with cold 5% TCA in the presence of 100 jug of serum bovine albumin, collected on Millipore filters and counted in a liquid scintillation counter.

The unicellular algae Chlamydomonas sp. were grown in tritiated seawater, previously filtered, autoclaved and slightly enriched in nutrients [7.2.2]. Experiments at the Bhabha Atomic Research Centre were carried out with varied tritium concentration in the medium from 0.6-4.1 juCi/ml of seawater. A sequential solvent extraction procedure has been used to study the distribution of tissue-bound tritium in the various organic fractions.


(i) Incorporation and distribution of tritium in algae

The uptake and incorporation of tritium in the green algae Ulva and in the red algae Porphyra are illustrated in Figs 1 and 2.

The rate of incorporation of TBT in the cell culture of Chlamydomonas sp. in relation to cell doubling is given in Table VII. The cultures had grown to a maximal bloom, attaining a cell-doubling factor of 7 - 8 within two weeks, and further additional culture time did not significantly increase the population size but the cells lost their mobility.and sank to the bottom of the flask. The TBT in the dry cells of Chlamydomonas sp. reached a level of 0.70 juCi/ml combustion water in a medium of 1.18 /nCi/ml seawater corresponding to an average of 63% of the medium concentration.

The lipid extraction procedure with acetone and CHC13- CH3OH mixtures removed about 40-45% of TBT; incorporation of tritium in the lipid fraction was an excellent index of fatty acid biosynthesis [7.2.11 ].


TABLE VII. RATE OF UPTAKE OF TBT IN Chlamydomonas Sp. CELLS [7.2.2]

Time of growth Cell doubling Activity in the cells

(days) factor (juCi/ml combustion water)

3 3.56 0.28

7 5.55 0.31

9 6.87 0.44

10 7.11 0.54

13 7.81 0.65

15 7.50 0.70

3 H concentration: 1.18 |tCi/ml seawater

FIG. 3. Acetabularia mediterranea, Molecular sieve chromatography on sepharose 4B of a crude extract (6.5 ml) of isolated chloroplasts. Column size: 2.5 X 36 cm; eluting solution: 2MNaCl; flow rate: 36 mljh; fraction size: 1.8 ml; room temperature: 22°C.


Another major fraction of TBT was obtained with 6N HC1 extraction which primarly consisted of protein hydrolysate [7.2.12], the amino acids obtained from the protein hydrolysate forming 70-80% of the total protein content of the algae. The appearance of tritium in the protein fraction reflected the extent of incorporation of tritium in the non-exchangeable protium of peptide amino acids, though proteins are known for their ability to acquire tritium by exchange with media protium [7.2.13].

The penetration and distribution of tritium in the different constituents of algae Acetabularia mediterranea and Acetabularia crenulata have been also studied [7.2.14]. The separation of the uptaken and incorporated radioactivity, carried out by conventional biochemical methods, has shown that an important part of tritium is present in the fraction including the small molecules (water, amino acids, ...); however, an appreciable part is recovered in the fractions formed by nucleic acids (DNA and RNA) and proteins. The amount of tritium incorporated by the algae increases as a function of the concentration of tritium in the seawater and the duration of exposure.

Purified chloroplasts of Acetabularia mediterranea were processed as reported previously [7.2.10] and their extract submitted to molecular sieving on a sepharose 4B column. Figure 3 shows that a distinct radioactive peak is eluted from the column in the fraction 21—26, and that it is followed by a second radio-active peak. In order to check the nature of the material present in the first radio-active peak, further experiments have been performed [7.2.5], and that the labelled materia] was indeed DNA was demonstrated by ultracentrifugation in a CsCl gradient, where it gave a single peak having a buoyant density of 1.703 g/cm3, which is characteristic of Acetabularia chloroplast DNA.

3.1.1.3. HTO exposure of freshwater animals


(i) Aquaria

The following fish species were studied in the various laboratories participating in the IAEA-Co-ordinated Research Programme: Carassius auratus (goldfish) and Salmo trutta forma fario ( t rou t ) , D e p a r t m e n t of Radiology (Mol); Gamusia affinis (mosquito fish), Poeciliopsis occidentalis (Gila topminnow), Salmo gairdnerii (trout) and Ictalurus lacustris (catfish) in the EPA Laboratory (Las Vegas); Tilapia mossambica in the Bhabha Atomic Research Centre Laboratory (India) [7.2.15]. Fishes were exposed in tritiated water from 10-30 days (Belgium) up to 32 days (India) and up to 203 days (USA); the animals were fed commercial food (Belgium, USA) or tritiated food (India, Belgium).

EXECUTION OF THE PROGRAMME 21

(ii) Outdoor pools

In the Lawrence Livermore Laboratory, a fibreglass pool [7.2.1 ] was filled with 2000 gallons4 of stream water and tritiated water added to a concentration of 80 /uCi/1; the pool was stocked with rhizomes of cattails, filamentous algae and mixed plankton obtained from a natural pond, several hundred freshwater clams (Anadonta nuttaliana Lea), 25 crayfish (Astacus sp.) and 25 goldfish (Carrassius auratus). Six plastic-lined pools [7.2.16], constructed at the EPA Experimental Farm on the Nevada Test Site, were filled with 3700 litres of tritiated water. Inorganic fertilizer and green algae were introduced. Windblown dirt, debris and hay from the farm entered the pools, and a variety of insect life was observed in the pools before mosquito fish (Gamusia affinis) were introduced. Four pools were stocked in mid-July and the fish harvested in mid-October.


It was observed [7.2.1, 7.2.15, 7.2.17] that the tritium in the Free Tissue Water (TFWT) remained close to the tritium concentration of the medium water; after one hour of exposure to tritiated water the TFWT concentration in Tilapia attains 70% of the medium concentration [7.2.15], Some fishes remaining at the end of the uptake experiment were returned to non-tritiated water for observation of their rates of loss of tritium. The biological half-life is found to be 48 ± 6 min in the Tilapia experiment; in goldfish and clams the rate of loss was very rapid and the curve is characterized by at least two components [7.2.1]: the short-lived component, which represents more than 95% of the tritium, had a half-life of about one day, and the long-lived component had a half-life of about 15 days.

(c) Tissue-Bound-Tritium (TBT)

The clams obtained tritium from the water as well as from their food, i.e. from the micro-organisms and the detritus in suspension in the water. The concentration of TBT changed with time and at different rates for different tissues [7.2.1 ]. It increased up to about day 90, when the maximum values were observed in most tissues. The concentrations were highest in the visceral mass and lowest in the calcareous tissue. Since the crayfish could be sampled only twice, at days 5 and 26, the maximum TBT values probably were not observed. They were highest in the digestive gland and lowest in the carapace. The TBT concentrations for crayfish muscle were about the same as for clam visceral mass.

4 1 gallon (US liquid) = 3.785 X 10"3 m3.


TABLE VIII. SPECIFIC ACTIVITY OF TRITIUM IN DRY TISSUE OF FISH GROWN IN AQUARIA OR IN OUTDOOR POOLS

Species Exposure conditions Specific activity ratio2 Ref. Species

Medium Days in THO Starved fish Fed fish

Ref. Species

Medium Days in THO Starved fish

3H-food Commercial food

Ref.

Tilapia Aquaria 30 0.025c 0.035" [7.2.15] mossambica

Carassius Aquaria 32 0 .13-0 .25 [7.2.17] auratus Pool 173-214 0.1 5C [7.2.1]

Salmo gairdnerifi

Dead eggs Aquaria 1 0.27 [7.2.16]

Dead fry Aquaria 32 0.39 [7.2.16]

Fish Aquaria 140 0.42 [7.2.16]

Salmo trutta forma fario

Adult Aquaria 5 0.1 5C [7.2.17]

Adult Aquaria 10 0.16C 0.1 5C [7.2.17]

Gamusia affinis

Young Aquaria 21 0.42 [7.2.16]

Young Pool U 0.36 [7.2.16]

Young Pool 39 0.56 [7.2.16]

Adult Aquaria 60 0.37 [7.2.16]

Adult Aquaria 203 0.52 [7.2.16]

Adult Pool 58 0.63 [7.2.16]

Adult Pool 93 0.88 [7.2.16]

Peociliopsis occidentalis

Young Aquaria 88 0.49 [7.2.16]

Young Aquaria 185 0.45 [7.2.16]

Adult Aquaria 79 0.56 [7.2.16]

Ictalurus lacustris

Dead eggs Aquaria 3 0.51 [7.2.16]

Small fish Aquaria 133 0.41 [7.2.16]

a b c

Tritium specific activity in dry tissue divided by that in medium water. Fertilized eggs placed in tritiated water when received. Edible part only (muscle).

EXECUTION OF THE PROGRAMME 23

(d) Specific activities

In Table VIII selected results are presented to show the ratio between the tritium specific activity in dried fish tissue and that in water in which the fishes were exposed and grown. A ratio greater than unity would indicate concentration of tritium within the organic constituents of fish relative to the water environ-ment. No ratio greater than unity was measured in the experiments reported. No significant differences are found in the specific activity ratios by feeding the Tilapia with tritiated food or starving them, probably because the maximum ratio attained is itself very low in both the cases. Moreover, no significant difference is observed between the values of the specific activity ratio in the trout muscle fed commercial or tritiated food: probably the intake was too low during the short exposure period. Results of experiments performed in the EPA Laboratory [7.2.16] show that the consumption of food grown in their tritiated environment increases the tritium specific activity in tissue of mosquito fish to levels about 50 to 90% higher than in fish grown in tritiated water and fed commercial foods.

Limited data are available on the loss of tissue-bound-tritium after transfer of fish to a less tritiated environment. It is clear, however, that a portion of tritium in tissue is not excreted rapidly [7.2.16]. This finding is commented on in the conclusions of the present report.

3.1.1.4. HTO exposure of marine animals

As little information was available on the rate of tritiation of body water in the marine organisms and its exchange to the organic form, investigations were initiated in three participating laboratories (Lawrence Livermore Laboratory, Bhabha Atomic Research Centre, Belgian Nuclear Centre) to study the rate of incorporation and loss of tritium in the body water and in the organic fraction of various marine invertebrates.


The clam Mya arenaria and the crab Cancer productus were obtained from San Francisco Bay, and the Japanese oyster Crassostrea gigas was obtained from Tomales Bay; these animals were placed in tritiated (126 nCi/ml) seawater in a fibreglass pool previously described [7.2.18], a dense resident population of Chlorella-like organisms being present in the water. Katelysia opima and Anadara granosa were collected near Bombay and transferred into glass aquaria filled with seawater, and the tritiated water was added to a concentration of 67.6 nCi/ml. The animals were given no food during the experimental period • [7.2.19, 7.2.20]. Crangon vulgaris, Asteria rubens and Mytilus edulis were obtained from the Belgian North Sea coast [7.2.21 ] and maintained in artificial


TABLE IX. TURNOVER CONSTANTS AND BIOLOGICAL HALF-TIMES FOR TRITIUM EXCHANGE IN TISSUES OF MARINE INVERTEBRATES3

K T1/2 Ref.

Mya arenaria (fed) Body, water hydrogen 0.33 h"1 2.1 h

Organic matter hydrogen

Rapidly exchangeable

Muscle 0.28 h'1 2.5 h

Viscera 0.29 h"1 2.5 h

Slowly exchangeable

Muscle 290 d [7.2.22]

Viscera 120 d [7.2.22]

Crassostrea gigas [7.2.18]

Body water hydrogen

Pooled (fed) 0.97 IT1 0.72 h

Pooled (no food) 0.52 h"1 1.34 h

Cancer productus (no food) [7.2.18]

Body water hydrogen 1.8 h_1 0.37 h

Katelysia opima (no food) [7.2.19]

Body water hydrogen 0.7 h"1 1.0 h

Organic matter hydrogen 0.24 d"1 2.9 d

Rapidly exchangeable

a Values determined during period of tritium loss.

seawater during the experimental period, the animals being fed with commercial food.


(i) Turnover of body water

The specific activity of tritium in the body water of clams that had been maintained in tritiated water for seven days decreased rapidly when they were removed to filtered, continuously flowing, tritium-free water. The loss curve had only one component; the rate constant was 0.33 h"1 and the biological half-time was 2.1 h (Table IX). These results indicate that the tissue-free water behaves as a single pool and that the turnover rate is very rapid [7.2.18]. In the oyster,


another filter feeder, the turnover rate of tissue-free water was measured for comparison with clams. As can be seen from Table IX, the turnover rate constants determined for pooled samples differed in the presence (0.97 h" 1) and absence (0.52 h~ ' ) of food organisms in the water. As a further basis for comparison, turnover rates were measured for the tissue-free water of the crab body fluid: the rate constants calculated were 1.8 h ' 1 during loss and the corresponding half-time was 0.37 h. Katelysia opima reached nearly 80% of the medium specific activity within an hour and body water tritium gradually increased further in 48 h to 88% and then followed the decrease in the medium during the remainder of the experiment. Equilibrated animals when transferred to the inactive medium released tritium quickly within a few hours; the loss curve had only one component. The rate constant was found to be 0.7 h _ ) and the biological half-time was 1 h (Table IX).

(ii) Turnover in organic material

Changes in specific activity were followed also in the rapidly and slowly exchangeable compartments of the organic material of muscle and visceral tissue of Mya arenaria (Table IX), these tissues being chosen for study because they usually differ considerably in their rates of hydrogen turnover. Muscle and viscera tissue were essentially the same in their rates of decrease in specific activity with time in the rapidly exchangeable compartments (Table IX). Hydrogen turnover was followed also in the slowly exchangeable compartment of the organic material of clam muscle and viscera: virtually no change was observed in this slowly exchangeable hydrogen compartment. This is consistent with the results of an earlier experiment [7.2.22]: the T was about 290 days for muscle and about 120 days for viscera (Table IX).

In Table X, data on the build-up of organic bound tritium in various marine invertebrates show that the level of tritium accumulation in the organic tissue is very low compared with body water concentration. The retention of tritium in the body tissue depends upon the chemical form and, in the present cases, the animals are fed with tritiated water.

3.1.1.5. Biological availability of tritium released in liquid effluents

Tritium in liquid effluents may have multiple origins and may prevail in different physico-chemical states. Certain organic tritium compounds may constitute a particular risk because of their preferential absorption by living organisms.

Algae (Scenedesmus obliquus), cultivated in effluents, allow the detection of such molecules [7.2.3] and consequently the evaluation of the importance of this contamination fraction. The culture of algae on effluents constitutes therefore a biological test.

to CTs

TABLE X. PERCENTAGE INCORPORATION OF TRITIUM IN ORGANIC MATTER OF VARIOUS MARINE INVERTEBRATES

Time of

exposure (d)

Mean moisture

content (%)

Activity (nCi 3H/g) Incorporation

(%)

Ref. Time of

exposure (d)

Mean moisture

content (%)

Seawater Wet matter Dry matter

Incorporation

(%)

Asteria rubens 2 64.3 29 10.7 0.22 0.7 [7.2.21]

Crangon vulgaris 10 80.3 33 17.7 0.80 0.9 [7.2.21]

Mytilus edulis Whole animal 44.4

Soft tissues 81.2 31.5 42.0 1.2 0.7 [7.2.21]

Shell 7.5

A nadara granosa Soft tissues

14

80.0 67.6 43.8 2.7 1.2 [7.2.19]

m X m o G H O 2 O •n H as m "O 73 O O 73 >

2 2 tn


TABLE XI. SPECIFIC ACTIVITY OF TRITIUM IN DRY TISSUE OF ALGAE (Scenedesmus obliquus) GROWN IN LIQUID EFFLUENTS a

RELEASED BY A RADIOCHEMICAL LABORATORY AND BY TWO DIFFERENT PWR NUCLEAR POWER PLANTS

Origin of effluent Initial 3H conc. 3H content in Specific activity

in culture combustion ratio

medium water of dry

(nCi/ml) tissue (/iCi/ml)

Radiochemical lab. 52 1.41 27.1

Radiochemical lab. 76.5 4.10 53.6

Radiochemical lab. 70.3 3.08 43.8

Nuclear power plant

SEMO 5.1 4.60 0.90

SENA 16.6 14.50 0.87

a The effluents were filtered on Millipore (0.45 fira) before mixing with culture medium.

Results of application of this method, on laboratory effluents originating from synthesis of labelled molecules and effluents released by nuclear power plants of PWR type, are presented in Table XI. In the case of effluents released by a radiochemical laboratory, the results showed that the tritium is preferentially incorporated in the organic matter of the algae but the percentage of 3H biologically available is lower than 1% of the total 3H present in these effluents. This small fraction is, however, important in the contamination of the food chain.

The values of the specific activity ratio are about one if the effluents released by the PWR nuclear power plants are considered; this means that there was no organic tritium biologically available present in these filtered effluents studied; however, some 3H was present in the insoluble organic fraction which contained more particularly micro-organisms.

A freshwater fish (Salmo trutta forma fario) has been also used as a biological test. The results showed that the values of the specific activity ratio (tritium specific activity in dry tissue divided by that in medium water) varied from 1.55 to 27.6, depending on the organs analysed, when the fish were grown (4 to 8 days) in water in which an effluent released by a radiochemical laboratory was added to a final concentration of 2.4 nCi/ml and 0.24 nCi/ml respectively in the two experiments. Results of experiments performed on the same fish species exposed [7.2.17] in tritiated water (1 /LiCi/ml) showed that the values of the specific activity ratio ranged from 0.03 to 0.19 for the various organs.


TABLE XII. SPECIFIC ACTIVITY (nCi 3H/gH) OBSERVED IN SAMPLES COLLECTED IN A RIVER AND A POND DOWNSTREAM OF A RADIOACTIVE DISCHARGE

A. RIVER

Water Aquatic plants Eggs (ducks)

Maximal Mean values Maximal Mean values Maximal Mean values

values values values

(combustion water)

3.15 1.12 35.8 10.8 60.6 8.3 ~

B. POND (No. 4)

Fish (dry matter) Fish

Maximal Mean values Maximal Mean values Maximal Mean

values values values values

(combustion water of

various organs) Free water tissue

0.50 0.24 5.73 2.21 0.67 0.50

3.1.2. Study of the tritium transfer in a natural environment

The ecosystem studied is a small watercourse that receives liquid effluents from complex nuclear facilities located in Mol (Belgium). Tritium in effluents was in water as well as in organic forms. The river feeds intermittently a series of ponds used for fish rearing. The ecosystem was investigated for about one year, the tritium concentration in water and sediment samples and in living organisms being determined. The emphasis was laid on measurement of the tritium incorporated in the organic matter, the specific activity of the combustion water being determined in each case.

Table XII presents some general values of specific activity observed in the samples collected in the river and in one of the ponds. When we look at these values it appears that those of the tritium incorporated in organic matter are higher than those of the river water by a factor as much as 20. This unexpected observation was in conflict with results from experiments in laboratory aquaria in which tritium was present as THO. Therefore one must look for biologically available tritiated compounds in the effluents released in the ecosystem under study. The presence of these compounds was experimentally proved later and

EXECUTION OF THE PROGRAMME 29 i

their biological availability evaluated. It would appear that the physico-chemical state of the tritium is a sensitive parameter of particular importance for predicting and evaluating population exposure [7.2.23].

3.2. SOIL STUDIES

3.2.1. General aspects of tritium behaviour in soil

The introduction of tritium into a soil typically occurs as a liquid in the form of precipitation or a liquid flow on to the soil, such as in irrigational water. Vaporous exchange of THO vapour in the air with surface soil-water is possible under certain conditions such as over a recently ploughed field where the surface soil-water is high [7.3.1].

The pulse of tritiated water at the surface of the soil will move through the soil profile as a stratum of labelled water. This has been demonstrated by several investigators [7.3.2—7.3.4],

The tritiated stratum of soil-water will move downward in the soil column, becoming increasingly blurred by diffusion and diluted by exchange with the unlabelled water originally in the soil. This pattern of tritiated soil-water movement has been observed in the soils of Puerto Rican rainforest [7.3.3, 7.3.5], a California cornfield [7.3.4], an abandoned cropfield in Illinois [7.3.3], a Nevada desert [7.2.7], and in northern and southern Finland [7.3.8].

The major factors affecting the fate of a given tritium pulse in the soil are:

(1) Soil-water diffusion (2) Evapotranspirational demand upon the soil-water (3) Gravitational movements in the soil pore space induced by precipitation

or irrigation after tritium exposure (4) Mechanical characteristics of the soil (5) Exchange with soil-water in capillary, hygroscopic and crystalline

compartments

The first four factors are the most important in determining the early behaviour of a given tritium pulse and the degree of exposure to vascular plants as the pulse traverses the root zone of the soil. Jordan and co-workers [7.3.9] studied the effects of tritium exchange with the various soil-water and hydrogen compartments, and concluded that the major effect of exchange was in the long-term behaviour of the tritium pulse.


The mechanical characteristics of the soil, namely the clay, silt and sand fractions, and the amounts of organic matter with its strong exchange capacity will also determine the behaviour of the tritium pulse. Loose, sandy and silty soils will permit a rapid movement of tritium to a depth below the zone affected by surface evaporation, placing it in the root zone of the vegetation. The permeability or draining rate of the soil is thus a major factor in the movement of tritium in the soil-water.

Most of the above-mentioned factors were operative in the experiments conducted in this programme. The heavy clayey soils of the tropical regions in India and the Philippines, the subtropical latisols of Mexico with high vegetative biomass are compared with the lighter soils of northeastern Europe, Finland, and the United States of America. The high rainfall of the tropics also contrasts strongly with the low precipitation observed in subarctic and arctic regions of Finland, northern Alaska, and the North American desert.

Soil tritium behaviour models have been presented by Sasscer and co-workers [7.3.10], and Jordan and co-workers [7.3.11]; and further discussed by Jordan and co-workers [7.3.9]. Previous models concerned with the behaviour of tritium pulses in the soil-plant-animal (man) ecosystems were given by Anspaugh and co-workers [7.3.13[ and Koranda and co-workers [7.3.1], A model concerned with the dose to man from an exposure to THO vapour was presented by Anspaugh and co-workers [7.3.13]. A general discussion of tritium in plants and soil was given by McFarlane and co-workers [7.3.14]. Soman and co-workers [7.3.15] have studied the behaviour of tritium in tropical soil-plant systems in India, and showed the relationship of tritium behaviour in the soil with that in the plant rooted in the soil. Detailed studies of this subject were also presented at a recent symposium on tritium behaviour in the environment [7.3.16].

Miettinen [7.3.8] gives five primary factors that determine the behaviour of tritium in the soil which are related to the factors previously discussed. These are:

(1) The THO pulse moves at a rate determined by subsequent water increments to the soil

(2) Movement of the tritium pulse is determined by the mechanical characteristics of the soil-bulk flow in pore spaces and diffusion in light-textured soils as an example

(3) The more discrete the tritium pulse is at late times, the longer the residence time of tritium in the soil

(4) Early behaviour of tritium is strongly influenced by evaporation and transpirational losses from the surface strata of the soil

(5) In dense, slow-draining soils, tritium may persist and be detected for several years; tritium from these deeper soil-water compartments may be drawn to surface layers by deep-rooted plants in the summer, or by cryo-pedological processes in the winter


3.2.2. Half-residence times of tritiated water in the soil under various climatic conditions

The half-residence times of tritiated water in soil as determined during the co-ordinated programme, and before that in the United States of America, are shown in Table XIII. The climatic conditions vary from tropical to arctic tundra.

Determination of the half-residence times has been based on the analysis of soil core samples taken at various times after the application of tritiated water on the soil surface. From the core samples the residual tritium has been calculated after determining their water content and the tritium concentration of the soil-water. The loss of tritium from the soil took place exponentially with time in all areas. The losses were most rapid immediately after the labelling when the tritium pulse was near the soil surface and became smaller as time passed. In many areas the half-residence time exhibited short- and long-term components. The values of various components are shown in Table XIII. For some areas only one component was observed: this might have been due to shortness of the test period. Also the very small amount of water which was used for the labelling and the fact that only a very short surface layer was analysed might have resulted in losses occuring with one rate only. For this reason these data are also included into Table XIII.

It should be noted that the half-residence times shown in the Table describe the reduction of tritium in the soil-water which is free and readily available to plants and can be extracted by the freeze-drying method. Some tritium was found to be bound so tenaciously in the soil, especially on clays, that it could not be extracted by freeze drying. This additional, bound tritium in the soil was found to give rise to the long components of the half-residence times, as will be discussed in connection with studies from the Nevada desert [7.3.21 ], California [7.3.4] and Southern Finland [7.3.34],

3.2.2.1. Studies in the agricultural environment

The short components of the half-residence time in the agricultural environ-ments (Table XIII) vary between 16 minutes and 14.4 days. If the two shortest components from California [7.3.4] and France [7.3.29] are left out of consideration, they vary in a much narrower range from 3.6 days to 14.4 days. The long components of the half-residence time vary from 85 days to 180 days.

The shortest half-residence time of 16 minutes was obtained in California after exposure of tritiated water vapour on a bare soil for a period of 50 minutes with a lucite chamber and then measuring the losses of tritium from the soil [7.3.4]. A rapid loss of tritium was due to the fact that the hottest part of the day occurred just after the exposure. Also the longer component had a small value of only 123 hours. The values are quite reasonable because the penetration

TABLE XIII. SOIL: UNIQUE EXPOSURE: LIQUID AND GAS

U) K>

Location Region and biome Soil type Tritium applied (mCi/m2)

Water applied (ltr/m2)

Annual precipitation (mm)

Irrigation (mm)

Depth of soil sampling (cm)

Length of test period

Half-residence time

Reference

Belgium Temperate agricultural Sandy soil 0.017-22 2.8 700 80 49 -85 d 12 h - 23 d [7.3.29]

Finland southern Subarctic agricultural Silt loam 3.9 6.7 650 15 37 d 12.3 d [7.3.33]

southern Coniferous forest Clayey silt loam 3.6 4.0 650 200 . 4 a 104-1280 d [7.3.34]

southern Coniferous forest Clay loam 6.0 7.1 650 200 2 a 5 - 6 3 - 2 0 4 d [7.3.34]

northern Arctic forest Sandy loam 4.8 7.1 450 180 2 a 6 - 9 0 - 2 0 4 d [7.3.34]

France Temperate Clay, calcareous 0.43 1 700-800 30 24 h 2 h [7.3.29]

Mediterranean 2.09 1 700-800 30 24 h 1 h 45 min [7.3.29]

Fruitgrowing 1.37 1 700-800 30 24 h 2 h 15 min [7.3.29]

1.85 0.5 700-800 30 24 h 1 h 50 min [7.3.29]

Mexico Temperate agricultural Sandy loam 19 3.3 530 1500 80 130 d 14-85 d [7.3.31]

Clayey vertisol 13-30 800 (total) 100 170 d 10-180 d [7.3.31]

Philippines Tropical agricultural Volcanic tuff, 20 2 2368 10 84 d 11.7 d [7.3.32]

clay 20 2 2368 10 84 d 14.4 d [7.3.32]

Thailand Tropical agricultural Clay loam 4.1 0.41 1100-1500 Daily 25 35 d 4 - 1 3 d [7.3.30]

m X m o c H O Z o Tl H SB W •o 90 O a 90 >

s s tn

Location Region and biome Soil type Tritium applied (mCi/m2)

Water applied (ltr/m2)

Annual precipitation (mm)

Irrigation Depth of soil sampling (cm)

Length of test period

Half-residence time

Reference

USA Hot temperature agricultural Silt clay 21 10-15

mm/d 95 1 a 3 .6-118 d [7.3.4]

Agricultural Silt clay 1 h vapour exposure

50 h 16 min—123 h [7.3.4]

Tropica] rainforest 13.6 1.1 2500 76 260 d 29 d [7.3.3]

Hot desert Silty sand alluvium

969 'shot tritium'

75 240 4 a 400 d [7.3.21]

Tundra Peaty 5.0 1.0 17 40 d 34.5 d [7.3.36]

M X cn o c JH O 2 O •n H a rn "0 7) O O SO •

3 s m

U)


of tritium into the soil from a short duration vapour exposure was evidently limited only to its surface.

Another short half-residence time was obtained in France under temperate Mediterranean climate after spraying tritiated water over fruit trees [7.3.29 J. In these experiments the short half-residence times were due to the small amounts of tritiated water (0.5-1 mm) which were used for the labellings performed under warm air conditions. Although the amount of labelling water was small, some of it penetrated to a depth of 30 cm in the soil where the moisture was below the field capacity and where the water permeability was moderate.

The other half-residence times from agricultural fields are from hot or temperate climates in California, Mexico, the Philippines, Thailand and from the cold area of southern Finland. The half-residence time obtained in Finland during a warm summer is within the range of the half-residence times from hot or temperate climates.

In the California valley the short component of the half-residence time became 3.6 days in the soil of growing rapidly transpiring young corn, which was irrigated daily after the labelling [7.3.4], Because the irrigation rate was only slightly above that estimated to be needed for evapotranspiration, there was only a small amount of excess soil-water to move the tritium pulse deeper into the soil. Thus a broad peak occurred at the 10-cm depth throughout most of the growing season and most of the applied tritium was lost during that time. From the curve, where the tritium remainders in the soil are performed as a function of time from the labelling, it can be seen that the long component (T1/2 = 118 days) is responsible only for 1% or smaller losses. Koranda and co-workers [7.3.4] have concluded that the short component is tentatively attributed to bulk water movement while the longer component is very likely due to tritium retained in more stationary water such as chemically bound water.

In Thailand the short and longer component of the half-residence time had values of 4 and 13 days respectively [7.3.30], These values were obtained in the soil growing vegetation under hot air conditions. During the whole test period no rainfall was received but the soil was irrigated daily. The short component is the same as that reported from California from the same kind of environmental conditions. The small value of the longer component in this area is mainly due to the fact that only the 25-cm surface layer of the soil was analysed. The depth profiles showed that after 10 days the maximum of the tritium pulse had already penetrated to a depth of 20 cm from the soil surface.

In Mexico the experiments were conducted in two areas where the type of soils and also the climates were different [7.3.31 ]. In Chapingo, the mean depth of the soil that covered the bedrock was only 80 cm and the soil was sandy loam with good permeability. In this area the half-residence time had values of 14 days and 85 days. In the other experimental area, in Salamanca, the soil was clayey


vertisol with low permeability. Here the half-residence time had values of 10 days and 180 days. In Salamanca the soil was irrigated but not in Chapingo. The values obtained are in good agreement with each other because the short com-ponent became longer in Chapingo where temperatures and evaporation are lower but rainfall rates and relative humidities higher than in Salamanca. The long component had a longer value in clayed soil in Salamanca than in sandy loam soil in Chapingo. These values are also in good agreement with each other. It was observed in both areas in Mexico that a small amount of tritium was quickly transported to a depth of 80—100 cm, the main portion of tritium being in the first 50-cm layer.

In the Philippines the experiments were carried out during the hot summer months and also in the cooler period at the end of the year [7.3.32], The half-residence times from the two tests became 11.7 days and 14.4 days, the longer value being from the cooler period. Both half-residence times have been calculated only for the first 10-cm surface layer. A lot of rain occurred during both experiments which was one reason why the half-residence times became longer in the Philippines than in California or Thailand.

In Finland the experiments in vegetation and corn growing soil were carried out in the summer of 1972, which was one of the warmest summers for many years [7.3.33]. The mean temperature during the course of the experiment was 20°C. The soil was not irrigated after the labelling but had 104 mm of precipitation during the experiment. The first rains (17.3 mm of total) occurred after two days from the labelling and stopped the rapid loss of tritium from the soil which had begun immediately after the labelling. These rains increased the water content of the surface soil twofold. The loss of tritium from the soil (15-cm layer) occurred with a half-residence time of 12.3 days. No longer component could be observed during the test period. On the basis of the depth profiles it could be estimated that about 10% of the applied tritium was lost through the drainage under the 15-cm surface layer.

3.2.2.2. Studies under natural ecological conditions

The short components of the half-residence time in natural environments vary between 5 days and 104 days, and longer components from 63 days to 1280 days. From these values the exceptional high values have been obtained in Finland in the experiments carried out in the clayey soil and begun just before the cold season [7.3.33], Also in the dry and hot desert environment, in Nevada, the half-residence time became long [7.3.21 ]. Under other conditions the differences are much smaller, the short components being between some days and some tens of days and longer components being hundreds of days. No great difference between the half-residence times obtained either in agricultural or in

3 6 EXECUTION OF THE PROGRAMME

natural environments can be observed. Perhaps half-residence times are a little shorter in agricultural than in forest soils.

In the Nevada desert the tritium in the soil originated from the Sedan detonation of the Plowshare programme in July 1962 [7.3.21 ]. Thus the tritium in the Sedan area has not entered the soil after the surface application of tritiated water, as in other experiments. Residual tritium in the soil was determined from the soil surface to a depth of 1.8 or 2.4 m at 47 stations in the ejecta field. More than 1000 individual soil samples were collected during the five-year period from May 1966 to February 1970. The reduction of tritium in the dry desert soil during that period took place slowly with a half-residence time of 400 days. The major losses were due to evapotranspiration but little if any losses were due to groundwater recharge. The distribution of tritium with depth at various distances from the crater lip was similar in all stations. The bulk layer was believed to be eluated to that depth by rainfall since shot time. During the study period the peak moved downward. The annual precipitation was only 75 mm in this area, and the soil was sandy with a small amount of clay. Separate exchange experiments were conducted to show if the freeze-drying method removed all the available tritium from the Sedan soil samples. An amount of 33% additional tritium was observed to be released from the soil samples.

In a tropical rainforest the half-residence time of tritium in the soil was found to be 29 days [7.3.3]. The experiments were performed in a montane forest in Puerto Rico, where the annual rainfall exceeds 2.5 m. In the tropical rainforest the dominating parameters which affected the reduction of tritium from the soil were the rainfall rate and the water permeability of the soil. In this area tritium was lost also through lateral flow. The average flux of water for the first 13 days was found to be 1.08 cm daily over the entire soil.

In Finland long-term tritium experiments were carried out in forest areas in the southern and northern part of the country which have considerable differences in their climates [7.3.34]. The length of the winter season, when the soil-waters are frozen, is in the south 120 days and in the north 200 days. The active growing season is in the south 180 days and in the north 100 days.

Very different half-residence times were obtained in southern Finland in two labelling experiments which were begun under various climatic conditions. In the first experiment, which began under wet air conditions in the late summer of 1972, the short and long components had values of 104 days and 1280 days respectively. In the second experiment, the labelling was performed in the middle of the unusually warm summer of 1973, the half-residence time having three components with half-times of 5, 63 and 204 days. Also in the north, where the experiment began in the summer of 1973, three components were observed with half-times of 6, 90 and 204 days. Although the half-residence times from the two experiments in the south differ considerably from each other, the remainders of tritium in the soil after one or two years from the labellings differ


only by 3%. The observed differences are mainly due to the fact that labellings were performed at various seasons under various climatic conditions.

The first labelling was done on a wet soil at the end of August during which month the rains (196.4 mm total) amounted to more than twice the long-term average. The day of labelling was rainy and it was followed by five rainy days during which 35.6 mm of rain fell. No losses of tritium occurred during the labelling and the tritium pulse was shown to move slowly downward in the clayey soil. The evapotranspiration losses of tritium remained slight during the autumn because of rains and because the cold season stopped evaporation already in October. Later the formation of the soil frost stopped the downward movement of the tritium pulse. For these reasons the reduction of tritium from the soil started slowly (T1/2 = 104 days) and continued at the same rate in the following spring and summer, which was exceptionally warm. In midsummer the tritium pulse was shown to move upward causing new maximum concentrations in the surface soil-water and also in all plant species analysed. About 94% of the applied activity was lost during the first component. The longer component of the half-residence time was visible after the autumn of 1973 and had higher values with the increase in the test period. It had half-times of 580, 930 and 1280 days after the 2, 3 and 4 years test periods respectively. The increase in the half-residence time with the increasing test period was supposed to be due to the fact that the clay soil had retained some tritium in a stationary or bound phase at the beginning of the experiment and later this tritium was released gradually back to the free soil-water thus adding to the tritium content of the soil-water at the time when only a small amount of the applied tritium was left in the soil. When soil samples from various years were combusted after oven-drying at first at 105°C, a large amount of tritium was found in the combustion water in all samples. Another fact that showed that some tritium had been bound in an immovable phase in clay minerals is that the tritium pulse remained at the same level in the soil during the autumn of 1974 when unusually heavy rains occurred, and then the groundwater was raised partly to the level of the tritium pulse in this area. Only a small reduction in the amount of tritium was observed after these rains. Also the waters formed from the snow melting in the various springs could not push the tritium pulse to the groundwater table, but they caused lateral drainage through which process some tritium was lost from the labelled area. It seemed that the exchange processes would happen slowly in this area where the soil temperatures are low and where the soil-waters are frozen during the winter. Another thing which had caused the half-residence times to increase with the increasing test period wast the fact that the tritium pulse was with the passage of time at a deeper and deeper soil stratum from where losses occurred increasingly slowly. Bogen and Welford [7.3.35] have obtained 3.5 years of half-residence time for the bound tritium in soil on the basis of fall-out tritium determinations in the years 1963—70 in Oklahoma. Their half-residence time


agrees with the 1280 days value from Finland if the latter represents only the bound tritium.

The second labelling in southern Finland was carried out in the middle of the summer of 1973 under warm and dry air conditions on a clay soil. The first rains occurred 11 days after the labelling. The loss of tritium from the soil occurred rapidly with a half-time of 5 days during the first days since the labelling and then continued with a half-time of 63 days up to the winter. During these two components 87% of the applied activity was lost. The third component had a half-time of 210 days and it dominated during the next two years when the soil was sampled. After the second autumn from the labelling the remainders of the tritium in the soil were 3.4% and after the third autumn 1.5%. For the first area the corresponding percentages were 6.1 and 4.5. This shows that the difference between two areas is about 3% for both years although the half-residence times differ considerably from each other. This means that in addition to the half-residence time one should know how long tritium or its various components have dominated in making comparisons between areas. The 3% difference between two areas is mainly due to the higher losses through transpira-tion in the second area where there were some big trees whereas in the first area only small trees were grown. On both areas in southern Finland the tritiated water pulse was pushed only little downward when the snows melted in the spring and rose up in the midsummers at the time of evaporation. New maximums were then observed in the plant tissue waters.

In northern Finland the labelling was carried out in the middle of July 1973 at the time of the best growing season. An exceptionally warm week (mean temperature 20°C) had followed the labelling. Only 0.9 mm of rain fell during the two weeks after the labelling. During these weeks the reduction of tritium from the soil was rapid (T1/2 = 6 days) but became slower (T1/2 = 91 days) when the weather became rainy. During the first two components 89% of the applied tritium was lost. The soil frost was formed already in September and the soil was not free from frost until the following June. During the summer of 1974 the losses of tritium remained slight because the tritium pulse was pushed to deeper soil layers at first by the waters from the earlier winter snows and later by the summer rains which were unusually heavy. The half-residence time had a high value of 780 days because the tritium pulse only moved downward in the unsaturated zone but had not yet reached the groundwater table. In the summer of 1975 the tritiated water pulse was pushed partly to the groundwater table after the snow melted and therefore only a little tritium was found in the soil near the groundwater level. The half-residence time was only 204 days near the when it was calculated after two years test period; it was 780 days one year earlier. In the following summer (1976) no tritium was found in the soil when it was analysed from the surface to the groundwater level.


The discontinuous elimination observed in this area is understandable because the two summers were climatically different, and because the sandy loam soil was permeable to water and thus allowed the tritium pulse to percolate to the groundwater. In the clay soils in the south the downward movement of the tritium pulse was very slow and practically no tritium was lost there by that process. Also in the north the losses of tritium by groundwater recharge remained a few per cent of the applied tritium. The upward movement of the tritium pulse was observed also in the north during the summer of 1975 at the time of highest evaporation.

The comparison of the areas in southern and northern Finland shows that tritium was lost more quickly from the soil in the north than in the south in the early period of the experiment and also in the late period, although the warm season is much shorter in the north. The reason for this is the difference in soil characteristics. At the beginning of the experiment the losses became higher in the north than in the south because the labelling was done in much drier soil in the north than in the south and because the sandy loam soil in the north did not bind so much tritium unavailable to plants as did the clayey soil in the south. For these reasons, and also for the 24 hours duration of the daylight in the north, the tritium activities of the plants reached higher values in the north than in the south after the labelling. Already in the following summer the tissue water tritium concentrations of the plants became higher in the south than in the north and remained so until the end of the experiment.

In Alaska the residence time of tritium was determined in a much more arctic environment than northern Finland [7.3.36]. Experiments were performed in the soil of a littoral tundra in the Barrow area. The experimental area was on a wet meadow where the permafrost extended to about 20 cm from the soil surface. The reduction of tritium from the soil occurred with a half-residence time of 34.5 days. The losses of tritium were due to evapotranspiration and also to the interflow of water inside the soil. According to the tritium experiment, between 4.6—5.6 mm of water daily was lost through these processes. At the same time open-pan evaporation reached 3.0 mm daily. These two values are in agreement with each other because the open-pan measurements do not contain the interflow. The half-residence time obtained in Alaska is also in agreement with values obtained under various conditions in Finland and in Sweden. The temperatures of the soil and air were much lower in Alaska than in Scandinavia in the early period of the experiment.

3.2.3. Conclusions

Most of the tritiated water deposited on the soil surface during the growing season is lost rapidly by evapotranspiration with a half-residence time ranging from some days to some tens of days in very different climatic areas. Much


shorter half-residence times may be obtained under hot and dry conditions where tritiated water is lost rapidly by direct evaporation. A minor portion of the tritiated water is lost more slowly with a half-residence time of one order of magnitude higher than the short component. This long-term retention of tritium in the soil is very dependent on the soil characteristics, which affect the association of tritium with the soil matrix and its minerals, and on the rate of water movement in the soil, and also on the climatic conditions. Very long half-residence times have been obtained in clay-containing soils both in hot and dry desert conditions where water movement occurs slowly by diffusion, and also under cold climatic conditions where the formation of the soil frost stops the water movement for a long period of the year.

The tritium concentrations in the vegetation are very sensitively dependent on the tritium concentration of the soil-water which is available for plant transpiration. The differences observed between plant tritium concentrations from various environments cannot be explained conclusively if the tritium concentrations of the soil-waters are not known. For instance, after an accidental release of tritium into the environment different tritium concentrations may be observed in plants depending much on the type of the soil in which they are growing and on the time elapsed from the release.

The determination of the residence times of tritium in the soil has proved to be difficult experimental work. Very different half-residence times may be obtained even in the same climatic area if other conditions are changing. The irregular soil matrix produces the uneven penetration of tritiated water in the soil so that big differences may be observed between the tritium contents of the cores sampled at various points in the labelled area. The distribution of tritium with depth is most uneven just after the labelling when most of the activity is near the soil surface, becoming more even with time and with depth. This has caused scatter in the experimental data and also in the calculated half-residence times. However, it may be stated that half-residence times determined under various uncontrolled environments in different climates are in good agreement with each other, and the deviating values may be explained on the basis of the prevailing conditions.

3.3. TERRESTRIAL PLANTS

3.3.1, Uptake, residence time The plants on which experiments were carried out varied widely in their

botanical characteristics, size, life-times and uses. The nature of the environment in which they were grown varied from tropical climate to Mediterranean, temperate and tundra regions. As it is impossible to control the conditions which


govern the growth of trees and plants, especially in the case of long periods of study extending over years, there is often a tremendous variation in the results obtained.

The experiments varied widely and modes of exposure were:

(a) Uptake of tritium through roots from soil irrigated or sprayed depending upon the methodology followed. In the case of small plants cultivated over a few square metres of soil, the activity of THO sprayed was a few mCi. In the case of larger trees where root soil was irrigated, the concentrations varied depending upon the type of soil permeability, size of the plant and environmental meteoro-logical parameters. Mostly the activities were a few mCi. In certain areas such as Mexico and Finland, the residual tritium in the soil provided the source of tritium uptake for some of the species investigated. (b) Comparatively larger plants, trees, etc., were also investigated after injecting a few mCi of tritium into the stem of the plants. In these cases the entire activity reaches the transpirational stream and it was possible to derive quite accurate evapotranspiration rates and the first component of the free water tritium. In India, the United States of America and France such experiments were conducted on a large number of trees, and different parameters governing biomass, peak arrival time of activity, transpiration rates, etc., have been derived on the basis of tracer kinetics in addition to mean residence and half residence time values for tritium. (c) Certain plant foliages were exposed to active vapour (in the THO or HT form) under controlled conditions. The duration of exposure was varied and the effects were found to be quite significant from the point of view of fixation of organically bound tritium. A number of parameters governing these experiments are change-able and the effects of such changes were investigated. In the Federal Republic of Germany and in India, plants grown in their natural environment were studied for their uptake through foliage under uncontrolled conditions. In addition plants grown on tritium-contaminated soil and environment were also studied.

Because of the wide scope of the studies conducted, the half residence times observed varied considerably from season to season, place to place and species to species. However, it was clear that there are three major components for the half residence times. These correspond to:

(a) The evapotranspiration of water through the soil-plant domain, (b) The tissue-bound water or cell water and other easily exchangeable tritium

in the organic form of the tissues, and (c) The organically bound tritium of the tissue which is not easily exchangeable.

The last component is very long and the incorporation fractions low. Because of the interference of the second component, quite often it is not possible to resolve


TABLE XIV. TRITIUM PERSISTENCE IN SUCCULENT PLANTS2

Tritium peak conc. Mean residence times

Species TFWT TBT TFWT TBT

(luCi/ml) (MCi/g) (d) (d)

Opuntia sp. 2.66 0.27 72 300

Euphorbia trigone

1.15 0.03 82 458

Euphorbia mili

Mem 1.55 0.03 115 189

Leaf 1.29 0.11 69 160

aSingle injection of 2 mCi, peak arrival time 70—80 days.

the two components of short duration. A number of laboratories obtained the resolutions on the basis of computer analysis of the results. In many cases only one consolidated half time for the first two components is given because of the widespread results, analytically separated on the basis of experiments.

There was a seasonal variation in the short-term components. Further, depending upon the irrigation of root soil, and changes in air humidity and temperature values, the half residence time corresponding to the evapotranspiration phenomena of the soil-plant domain was found to vary. It was also found in India, France and the United States of America that the technique of sampling the respired water by using sample bags tied around the foliage gave a different half-life value in many cases. This is due to the fact that the environment around the bag, when such samplings are done, changes considerably and hence effectively varies the transpiration rates.

In Belgium, in spray experiments on rye grass plots and pastures, the summer and winter results varied considerably, mainly because of the change in the water cycling parameters of the system.

The half residence time values as observed under the conditions existing in Finland were mainly on the basis of following up the tritium activity-time profile over long periods, the uptake being from the residual tritium in the soil. Hence these are 'apparent' values and do not necessarily reflect the botanical water turnover rates in the system corresponding to the biological half-life of animals.

In France the Mediterranean climate is characterized by summer droughts and winter rains. There is a wide variation in the environmental temperature and wind


conditions. It was found that there is a definite dependence of half residence times on the evapotranspiration rates as reported earlier in the work done in the United States of America and in India. This confirms the general dependence of half residence time on the evapotranspiration rates as mentioned earlier.

3.3.1.1. Succulent plants

Succulent plants are of a different class from aquatic plants in view of their adaptability to the adverse conditions of water availability. Experiments were conducted under water stress conditions to determine the mean residence times for TFWT and TBT, and the results are presented in Table XIV. The stem of Opuntia sp. has shown significant incorporation of TBT, 10% of TFWT on a dry weight basis compared with the stem of the other two plants. The leaves of £ mill, however, have shown the same level of TBT as the stem of Opuntia. This indicates that the function of photosynthesis is carried out in such plants by the stem where the leaves are absent. The large residence times for TFWT (72 — 115 d) facilitate the synthesis of bound tritium to a greater extent. The residence times for TBT are also long, ranging from six to twelve months. The transpiration rates calculated from the tritium tracer kinetics [7.4.1, 7.4.2] are of the order of 0.001 ml per gram wet weight daily for all the three plants, which is nearly hundred times less than that for flowering plants [7.4.3] and trees [7.4.4].

3.3.1.2. Vegetables

(a) Soil spray

The mean residence times for radish, R. sativus, and the medicinal plant P. fraternus are about two days whereas the leafy vegetable A. viridis has considerable shorter residence time, 0.1 d (Table XV). The residence time for radish obtained by Yuthamanop [7.4.5] is somewhat higher (13.5 d). This may be due to the different exposure conditions and seasonal influences. Similarly tomato, L. esculentum, has been studied both under tropical and temperate environmental conditions. The residence times in the tropical climate range from 4 to 14 days. The large residence time of 60 days observed under the Mexican temperate climate is due to the organic-bound tritium arising from the slow uptake of residual soil-water activity (0.3-0.4 nCi/g soil) [7.4.6]. In general, mean residence times for vegetables and fruit-yielding plants vary from 2 to 18 days. The mean residence time for sweet potato, E. batatas, (18 d) is found to be higher compared with all other species studied in the Philippines [7.4.7]. All the vegetables, tomato, radish, sweet potato and Chinese cabbage, studied under


Thailand climatic conditions [7.4.5], are also about 10 days. The fast component residence times of TFWT for most of the garden vegetations are seen to be about 10—12 days.

(b) Foliar uptake

Concentration factors5 of 0.10 (stem) and 0.45 (leaves) are obtained in the vapour phase exposures of mirchi, C. frutescens (Table XVI). The lower concen-tration factors of 0.04 obtained for lettuce and cabbage seedlings are probably due to the small pore openings of the shoots in contrast to the larger pore openings in the leaves of mirchi under active transpirational conditions. Koranda and Martin [7.4.8] reported concentration factors varying from 0.17-0.49 for eight different plants. McFarlane [7.4.9] observed a concentration factor of 0.34 for HTO absorption whereas HT absorption has been found to give 0.84 in the leaves of lettuce plants. The high value in the case of HT absorption is the possible result of a larger influx of the HT molecules into the leaves and its subsequent oxidation to HTO.

The mean residence times for the TFWT component in these experiments have been found to be much shorter: 0.09 days in comparison with the fast component residence times under soil irrigation conditions. Though there is a possibility of more than one component for TFWT, components of significantly different residence times could not be ascertained in the present experiments. Koranda and Martin [7.4.8] have observed a 270-h component which is attributed to the metabolism of TBT. In foliar absorptions, 3 -4% TBT levels have been obtained for an exposure time of 2 h. The behaviour of tritium is qualitatively similar for vapour or liquid phase exposures with the major part of tritium being associated with short TFWT residence time and a small percentage with long residence time which might be attributed to organic fraction.

3.3.1.3. Trees

The uptake, retention and release patterns of tritium injected into the stem of large plants and trees are investigated and the results are represented in Table XVII. Parameters governing the biomass, peak arrival times and evapo-transpiration rates have also been derived for some of these trees on the basis of tracer kinetics [7.4.10]. Under Indian tropical conditions, badam, mango, sapota, ashok, norfolk pine, banana, coconut, arecanut palm and casuarina show fast component turnover times of 0 .3-3.0 days. Under Finland conditions [7.4.11], mean residence times of 9—23 days are reported for pine, blueberry, cowberry,

5 The concentration factor is defined as the ratio of /LiCi/mi of TFWT to /iCi/ml of

water in air.


TABLE XV. TRITIUM RESIDENCE TIMES IN VEGETABLES USING SOIL SPRAY

Mean residence times (d)

Species Remarks Country Species

I II III

Remarks Country

Tomato, Licopersicum 60 Roots & Mexico

esculentum stem

25

18

Leaf

Fruit

Mexico

Mexico

3.9 Fruit Philippines

12.5 28 Leaf Thailand

14.0 31 Fruit Thailand

Radish, Raphanus 2.2 Stem India

sativus 2.9

13.5 30

Roots India

Thailand

Maithichi bhaji,

Amaranthus viridus 0.1 10 Whole India

Medicinal plant, 1.7 14 Leaf India

Phyllanthus 2.1 13 Stem India

fraternus 7.7 Roots India

Beans, Phaseolus vulgaris

3.0 17 23 Mexico

Mung beans, 15.0 Roots & Philippines

Phaseolus auredes - stem

roxb. 10.0 Leaf Philippines

Soyabeans,

Glyciae Max L. 17.0 Philippines

Sweet potato, 7.3 Thailand

Ipomaea batatas L. 18.0 Philippines

Chinese cabbage 7.5 Philippines

Brassica compestris 8.0 Thailand

Cowpea, Vigria sinesis savi L.

11.5 17 Thailand

birch and spruce. In France [7.4.12], during the warm dry season, fast component residence times of 1 —2 days are observed for apple tree and grape leaves. Citrus fruits and grapes indicate long components of 1 - 4 months and this suggests the water-retaining capacity of these fruits. The results presented above can be under-stood in terms of the different evapotranspiration conditions present in the various countries. The general conclusion that arises from this study is that the mean residence times for the fast components of larger trees are a few days.


TABLE XVI. TRITIUM RETENTION IN VEGETABLES BY FOLIAR ABSORPTION

Species

Mean residence times (h) Concentration

Country Species

I II III factor

Country

Mirchi, Capsicum frutescens L.

Leaf

Stem

0.95

0.95

— — 0.45

0.10

India

Lettuce, Lactuca sativa L.

Shoots 0.70 - - 0.04 India

Cabbage, Brassica oleracea L.

Shoots 0.70 - - 0.04 India

Burclover,

Medicago hispida 0.90 17 270 0.27 USA

3.3.1.4. Food grains

Mexico [7.4.13], the Philippines [7.4.7] and the United States of America [7.4.8] have reported tritium turnover rates in food grain plants: maize, wheat and rice. The results tabulated in Table XVIII show the existence of multiple components. The mean residence time for the first component is found to be about 10 days, about the same as that for other terrestrial plants. The mean residence times for the third component of maize and wheat are representative of tissue-bound tritium.

3.3.2. Metabolism 3.3.2.1. Incorporation

The study of tritium turnover in the water compartment indicates the incorporation of a definite fraction in the organic constituents and this varies in different plant systems. The levels of incorporation of TBT in plants are presented in Table XIX. The relatively lower percentage fixations in terrestrial plants is possibly due to the semi-chronic conditions or single exposure used. Higher


TABLE XVII. TRITIUM TURNOVERS IN TREES

Species Mean residence times (d)

Remarks Country Species

I 11 HI

Country

Badam, Terminalia catappa

0.3 0.8 12 -26 Injection irrigation

India

Mango, Mangifera indica

0.6 1.7 5 - 7 Injection irrigation

India

Sapota, Achras sapota 3.2 — Injection irrigation

India

Ashok, Saraca indica 1.6 18 Injection irrigation

India

Norfolk pine, Arcaria bidwilli

0.4 ! -'. 18 Injection irrigation

India

Banana, Musa indica 0.4 — 14 Injection irrigation

India

Coconut palm, Cocas nucifera

1.4 — — Injection irrigation

India

Arecanut palm, Areca catechu

1.3 - 14 Injection irrigation

India

Casuarina, Casuarina equisetifolia

2.2 — Injection irrigation

India

Pine, Pinus sylvestris 23.0 - - Spray Finland

Cowberry, Vaccinium vitis idaea

10.0 - - Spray Finland

Blueberry, Vaccinium myrtillus

9.0 300 - Spray Finland

Birch, Betula verrucose

9.0 12.0

40 80

— Spray Spray

Finland Finland

Spruce, Picea excelsa

17.0 37.0 _ -

Spray Spray

Finland Finland

Orange, Citrus sinensis Leaf Fruit

- 50 120

- Spray Spray

France France

Vineyard, Vitis vinifera Leaf Fruit

2.0 12.0

- - Spray Spray

France France

Olive, Olea europaea 8.0 - - Spray France

Apple, Pyrus malus 1.0 - - Spray France

Spruce, Picea abtes 4.0 — — Uncontrolled vapour

Fed.Rep.of Germany

Hornbeam, Carpinus betulus

2.0 — — Uncontrolled vapour

Fed.Rep.of Germany

Pine, Pinus sylvestris 4.0 6.0 - -

Vapour Vapour

Fed.Rep.of Germany


TABLE XVIII. TRITIUM RESIDENCE TIMES IN FOOD GRAINS USING THE SPRAY METHOD

Species

Mean residence times (d) Activity

sprayed

(mCi/m2)

Country Species

I II III

Activity

sprayed

(mCi/m2)

Country

Maize, Zea mays (H-309)

4.5 45 87 13 Mexico

Maize, Zea mays 5.1 - - 5 Philippines

Maize, Zea mays 7.4 - - 20 USA

Rice, Oryza sativa 13.0 - - 5 Philippines

Wheat, Triticum vulgarae

6.0 31 40 30 Mexico

specific activity ratios could be obtained by maintaining constant specific activity in the soil-water [7.4.14],

Wheat and maize seeds have shown an even distribution of tritium in the structural parts [7.4.6] (Table XX), and 90% of their tritium content has been found to be organic. The remaining 10% (TFWT) is commensurate with the water content of these seeds.

3.3.2.2. Biochemical distribution

An attempt is made to study the distribution of the organic bound tritium in the various biochemical constituents. A study conducted on maize [7.4.13] indicates 68% fixation in carbohydrates compared with the total organic bound tritium (Table XXI). These results further indicate non-homogeneity in the different biochemical constituents and preferential incorporation in fats and proteins. Kahma and co-workers [7.4.11] observed a low relative specific activity ratio (0.37) in the nucleic acid fraction of the pea seedlings. Most of the organic bound tritium incorporated in Acetabularia sp. is methanol extractable and hence is probably the lipid fraction [7.4.61.

3.3.3. Accumulation of elemental tritium: Conversion of HT to HTO by soil and plants

The results of the studies with HT carried out in the United States of America indicated that the presence of potted plants substantially facilitated the conversion

E X E C U T I O N O F T H E P R O G R A M M E

TABLE XIX. TBT INCORPORATION IN DIFFERENT PLANTS

49

Species Component RSAa Experimental

conditions

Algae, Chlamydemonas sp. Whole 0.62 Immersion

Algae, Scenedesmus obliquus Whole 0.60 Immersion

Cactus, Opuntia sp. Stem 0.16 Injection

Cactus, Euphorbia trigona Stem 0.04 Injection

Cactus, Euphorbia mili Stem

Leaf

0.03

0.13

Injection

Injection

Flowering plant,

Tabernaemontana divaricata Leaf 0.04 Irrigation

Radish, Raphanus sativus Root & stem 0.06 Irrigation

Medicinal plant,

Phyllanthus fraternus Whole 0.10b Irrigation

Badam, Terminalia catappa Leaf 0.001 Injection -

Norfolk pine, Arcaria bidwilli Leaf 0.05 Injection

Mango, Mangifera indica Leaf 0.08 Injection

Mirchi, Capsicum frutescens Leaf 0.04 Vapour phase

Lettuce, Lactuca sativa Shoots 0.04 Vapour phase

Cabbage, Brassica oleracea Shoots 0.04 Vapour phase

3 RSA = relative specific activity ratio, /iCi/ml combustion water to that of ;uCi/ml TFWT

(both peak concentrations). b Four times irrigation.

of HT to HTO (Table XXII). Lettuce plants appeared to have been contaminated by the foliar absorption of tritiated water vapour. Although the site of the conversion reaction was not identified, high concentrations of HTO in the soil suggest that the soil or soil micro-organisms may have been involved. Conversion half-times calculated from the injection rates range from 19 to 23 hours. It is clear from these values and from the observed elevated HTO concentration in the chamber water vapour only a short period after the start of the treatment that the release of elemental tritium into the environment may present a local contamination threat.


TABLE XX. DISTRIBUTION OF TBT IN DIFFERENT STRUCTURAL PARTS OF FOOD GRAINS

Species Parts

Activity

Country Species Parts

(%) pCi/g

Country

Maize, Zea mays Endosperm 31.6 47.5 Mexico

Germ 39.5 59.3

Seed coat 28.9 43.4

Wheat, Triticum Flour 28.6 340 Mexico

vulgarae Bran 40.3 480

Germ 31.1 370

TABLE XXL BIOCHEMICAL DISTRIBUTION OF TBT IN MAIZE - SINGLE EXPOSURE

Fraction

Activity

Fraction

(pCi/g)

Dry matter 89.5 64.3 ± 13.6

Tissue water 10.5 7.4 ± 0.9

Fat 6.1 87.2 ± 3.2-

Proteins 9.3 63.2 ± 10.0

Carbohydrates 68.3 39.2 ± 10.7

Fibre 3.5 38.2 ± 8.7

Residue 2.3 -

3.3.4. Effects on plants of tritium incorporation The effects on plants of tritium incorporation can be caused by the mass

difference, the beta particle emission, or the properties of the decay product, helium-3, which differ vastly from the properties of hydrogen.

Deuterium is the ideal tool to study the role of mass difference because it differs from protium and tritium only in mass and is not radioactive. As far back


TABLE XXII. RATES OF TRITIUM CONVERSION IN THE PRESENCE OF POTTED PLANTS IN AN ENVIRONMENTAL GROWTH CHAMBER2 -

Country

HT treatment

period

(d)

HT —> HTO conversion rate

Country

HT treatment

period

(d) per minute

(nCi/min)

per pot

(nCi/min per pot)

per g fresh .wt

(nCi/min per g)

USA 1 - 6 13.3 0.53 4.43 X lOT2

(Las Vegas) 6-11 13.7 0.72 0.38 X 10~2

11-17 11.3 0.81 0.28 X 10~2

a Conditions in the environmental chamber: Temperature, 20° ± 5°C; Relative humidity,

75 + 5%; HT concentration, 5 nCi/1; Soil, vermiculite + peat (1 : 1); Plant, lettuce

(Lactuca sativa).

Note: This reaction was subsequently studied further and found to be facilitated by soil

micro-organisms.

as 1937 deuterium was reported as retarding respiration in yeast [7.4.15]. Germination of seeds and spores and the growth of Chlorella were shown to be inhibited in proportion to the concentration of D 2 0 in the culture solution by Crumley and Meyer [7.4.16] and Moses and co-workers [7.4.17]. Weinberger and Porter [7.4.18] observed Chlorella cell enlargement in the presence of D 2 0, and additional evidence by Bennett and co-workers [7.4.19] pointed out that this can occur in the absence of cell division. They concluded that D 2 0 was only inhibiting the cell division process. They also observed that cells could be acclimated to D 2 0 by gradually increasing its concentration in the culture medium. Blake and co-workers [7.4.20] suggested that the effect of deuterium on embryo development was ameliorated by the presence of large hydrogen-containing food reserves in the seed. The same researchers [7.4.21] later separated the embryos from various seeds and showed that D 2 0 inhibited all species in the same manner.

Biological effects caused by deuterated water molecules are probably associated with a change in the average free energy of metabolic water. Calcu-lations of water potentials from the vapour pressures reported by Jones [7.4.22] give the values listed in Table XXIII. It is obvious that putting tissue into pure D 2 0 would cause a tremendous osmotic shock; for instance, at 25°C it would be comparable to immersing the tissue sample into a solution more concentrated than 7M NaCl. Since the water potential 0 t w ) equals the sum of the component


TABLE XXIII. WATER POTENTIAL OF D 2 0 AT VARIOUS TEMPERATURES

Temperature

(°C) 10 20 30 40 50 60

Water potentials3

in atmospheres - 193 - 181 - 166

.

- 151

. .

- 137 - 124

a Water potential calculated from the relationship >i>w = (RT(ne/e0)/Vw, where R = 0.082055

(litre •atm)-deg"1-mole"1, T is temperature in degrees K, e is the vapour pressure, e0 is the vapour

pressure of pure free water at T, and Vw is the partial molal volume.

potentials, the potentials of mixtures of D 2 0 ( o r HTO) with water are proportional to the abundance of D 2 0 (or HTO)

where ^ and represent the water potentials and and a2 represent the fractional portion of the solution volume represented by H 2 0 and D 2 0 (or HTO) respectively.

When HTO is added to H 2 0 , it is clear that the water potential of the solution is

^w = ^HTO a

since by definition

^H2o = 0

Thus, when evaluating experiments conducted with high levels of D 2 0 (or HTO), considerable attention should be given to the water potential gradient imposed by the treatment. Unfortunately, this aspect has generally been over-looked. The available literature indicates that at concentrations of D 2 0 less than 1%, effects are not generally evident. This seems to support the idea expressed above and may mean that insults do not take place, or on the contrary may mean that our detection systems are not sensitive enough to observe their manifestations.

In contrast to most deuterium studies, the concentrations of tritium found in the environment, and in most experiments, are such a small fraction of the total water content that the contribution of tritium to altering the average molecular free energy is generally insignificant and can be ignored. For example, it can be


shown by using the specific activity of tritium (Ci/g), Avogadro's number (molecules/mole), and the molecular weights of HTO and H 2 0 (g/mole) that a solution of 1 microcurie per millilitre GuCi/ml) (which is much higher than environmental levels, but representative of some experimental concentrations) contributes only one molecule per 1.83 X 10" molecules of H 2 0. Thus the significant effects of tritium on biological systems are probably not due to mass differences, but rather to the beta radiation resulting from decay and/or to the decay product.

The effect of ionizing radiation (X-rays) on bean roots has been one of the classical demonstrations of radiation effects. Many outstanding works on this subject were written by Gray, Thoday, Read, and Scholes in the British Journal of Radiology from 1942 to 1952. Their work showed that the apical meristem of the root was radiosensitive and was therefore a good system to study relative biological effectiveness. Spaulding and co-workers [7.4.23] repeated Gray's techniques and compared the effects of X-rays with the damage found in plants exposed to beta radiation from HTO. They immersed bean roots in HTO and calculated the dose from diffusion time and the specific activity of the treatment solution. Exposure times were from 1 to 4 hours and no consideration was given to residual tritium which became part of the organic molecules. Their calculations showed a relative biological effectiveness of 1.0 + 0.06 according to the equation:

^ ^ ^ _ effect of beta dose effect of X-ray dose

They concluded that in their system beta radiation derived from the decay of tritium in the plant water had the same effect both quantitatively and qualitatively as 175 kilovolts peak X-rays applied externally.

In the process of preparing tracers by exposing soybeans to carbon-14-labelled carbon dioxide and HTO, Chorney and co-workers [7.4.24] observed effects on the growth rate and gross morphology of the soybean plants. Somatic aberrations caused by tritium resulted in characteristic bulbous enlargements at the nodes and below the .terminal influorescence, and the leaves were mottled as in other radiation treatments. These observations were the same as in other radiation treatments, and were assigned to a calculated accumulated dose of 1000 rads which resulted from growing the plants in culture solution containing 37.5 nCi/ml of tritium. The differences in growth rates between the treated plants and the controls were reported, but these data are of a questionable value since in the hermetically sealed growth chambers the carbon dioxide (C02) concentrations were allowed to fluctuate between 50 and 1000 parts per million (ppm) whereas the control plants were grown in atmospheric levels of C0 2 . Seeds from the plants exposed to tritium contained 17.6 juCi of tritium per gram and, when stored for 44 days and then germinated, a pigment abnormality was observed in the primary leaves.


-The continued culturing (18 months) of alfalfa plants in a closed environmental simulator containing 300 nanocuries per millilitre (nCi/ml) of tritium as HTO revealed neither detectable morphological damage nor alteration of any physio-logical parameter of the plants [7.4.25]. However, using an extremely sensitive indicator of somatic alteration, Vig and McFarlane [7.4.26] have shown genetic effects in soybean plants when the seeds were germinated in water containing as little as 10 nCi/ml of tritium.

When a beta particle leaves an atom, a resilient energy is imposed on the atom, called recoil energy. In the decay of 32P this energy is sufficient to cause bond breakage. In tritium decay, the maximum recoil energy is too small to have much effect on chemical bonds [7.4.27],

The decay product of tritium is helium-3 which is a noble gas with vastly different chemical properties from its parent. The replacement of the newly formed helium with stable hydrogen has been thought to occur with sufficient ease to cause little or no effect. This logic has led to the assignment of all damage caused by tritium in biological systems, whether somatic or genetic, to the effect of the radiated 3 megaelectron volts beta particle. One experiment which argues against this rationale was conducted by Funk and Person [7.4.28]. They showed that decay of tritium in the 5 position of cytosine resulted in a specific mutation. This specificity argues in favour of assigning the effect to transmutation of tritium to helium which causes interruption of the coding sequence at a particular point. When helium is formed, it immediately leaves the site formerly occupied by the tritium atom, and the atom formerly bound to the tritium atom becomes a free radical. Free radicals are usually highly reactive, unstable species that can stabilize by combining with another free radical or by intramolecular rearrangement. This is often accompanied by the elimination of an atom or molecular fragment, and the formation of a double bond in the parent molecule. Therefore, it should be remembered that the possibilities of damage other than direct radiation damage have largely been ruled out by hypothesis and not by test.

Radiation doses from environmental tritium are very low. The Federal Radiation Council cites 170 millirems yearly as the recommended maximum dose from all sources except medical radiation and natural background for the human population. This conservative figure is designed to be below the dose that could cause any damage to man. Using a quality factor of 1.0, the recommended maximum dose from tritium to man would be 170 millirads if tritium were the only source of radiation. Near the Humbolt Bay Pacific Gas and Electric nuclear power reactor, plant samples were collected which contained up to 3.8 nanocuries per litre of tritium in the extractable plant water. If this were a chronic contami-nation level, the plant would have an absorbed dose of 0.00044 millirads yearly. Compared with the 170 millirads suggested as safe for man, this seems to be an insignificant dose. Compared with the 1000 rads used by Spaulding and co-workers [7.4.23] in their experiments, even the highest doses that were observed in


plants near that reactor were miniscule. This is not an endorsement of the hypo-thesis that no effects would occur, but, if present, it is probable that they would not be observed because of their infrequence.

3.4. TRANSFER AND INCORPORATION OF TRITIUM IN MAMMALS

Knowledge of the pattern of movement, metabolism and incorporation of tritium in mammalian species is of importance in order to be able to answer questions concerning radiobiological and health hazard problems, and also because of the importance of certain mammalian species as a source of human food. For these reasons, research projects designed to obtain information on transfer para-meters in mammals have been included in the programme. These projects have been carried out in Belgium, the Netherlands, the Philippines and the United States of America.

Tritium metabolism has been investigated in small laboratory and in domestic animals. The former group has the advantage of experimental simplicity and is particularly suitable for investigations on the incorporation of tritium in important biological molecules. The experiments involving domestic animals have produced information on the tritium content of such important food items as meat and milk, and on the incorporation of .tritium into the organic constituents of these products. Furthermore, in one study, a small rodent (kangaroo rat, Dipodomys deserti) which had been living for several generations in a natural environment in which tritium levels were relatively high, was taken to the laboratory for detailed study of metabolism and distribution of tritium in the animal organism.

The studies mentioned above can be divided roughly into experiments in which tritium was administered as tritiated water (THO), and experiments in which organically bound tritium was ingested by the animals. The experimental results of some of these studies have been published during the time that the co-ordinated research programme has been in operation. It is the purpose of this section to review and discuss the main results, supplemented with unpublished results of more recent experiments, and to relate these to data obtained elsewhere.

3.4.1. Metabolism of tritium, administered as THO 3.4.1.1. Biological half-life of tritium


Single doses of tritium may be administered either orally or parenterally. This means ingestion via drinking water in the former case, and intravenous, intra-muscular or intraperitoneal application in the latter. Single dose experiments have been carried out on domestic animals in all participating laboratories.


TABLE XXIV. BIOLOGICAL HALF-LIFE OF TRITIUM IN BODY WATER AFTER ADMINISTRATION OF THO

Species

Biological half-life (days)

Species

1st component 2nd component

Mouse 1.1

Kangaroo rat 13.4 + 0.7; 13.2 ± 1.3 114 ± 50

Goat (lactating) 4.1 + 0.1 ( 2.9- 5.3)

Goat (non-lactating) 8.3 + 0.5 ( 6.7-10.4)

Miniature goat (non-lactating) 4.3 ± 0.2

Pig 3.8-4.3

Cow (lactating) 3.1; 3.3; 3.5; 4.0 33

Cow (non-lactating) 4.0 ±0.2 40

Chicken 4.6

Continuous administration of THO is limited under most experimental conditions to the oral route. It is essential that the specific activity of the drinking water remains constant during the course of the experimental period to ensure that equilibrium conditions between intake and excretion are reached. This condition requires special experimental precautions in the case of lactating dairy cows which have a water consumption of about 40 litres daily while the duration of the experiment is thirty days or more. Such investigations have been performed in Belgium, the Netherlands and the United States of America on both laboratory and domestic animals.


Table XXIV summarizes the values of the biological half-life of tritium in the body water of a variety of species, obtained in different studies. The values for a second, long half-life component, have been derived from long-term intake experiments.

The data in Table XXIV are in good agreement with results published in the literature. Richmond and co-workers [7.5.1 ] give values of 1.13 ± 0.14 days for mice and of 11.82 ± 2.96 days for kangaroo rats. Cunningham [7.5.2] found a half-life of 3.3 days in pigs with free access to water and of 6.3 days in pigs with


D a y s

FIG.4. The evolution of 3H activity in milk and in milk constituents after continuous administration of THO for 41 days to a lactating cow.

restricted water intake. This shows that the availability of water may influence water turnover. Another factor which may have an effect is the ambient tempera-ture. Variations in ambient temperature are often seasonal, and seasonal changes in the biological half-life of tritium have been reported for animals [7.5.3] and man [7.5.4], An average value of 3.54 ± 0.10 days (range 3.0-3.9 days) for lactating dairy cows and of 3.4 ±0.18 days (range 2.8-4.1 days) for bulls of between 1 and 1.5 years old has been reported [7.5.5]. It appears from these data that lactation does not influence water turnover in the cow. The results presented in Table XXIV suggest that lactation in goats brings about a shortening of the residence time of tritium in the body water. The physiological effect of lactation on water metabolism would be an increase in the turnover rate of water for a body water pool of the same size, and consequently a shorter biological half-life.


Apparently, lactation has different consequences on water metabolism in the cow and in the goat, both ruminant animals. More detailed investigations are necessary to provide quantitative information on this interesting subject.

Another point of interest is the correlation between water turnover and body weight. Richmond and co-workers [7.5.1] have shown that a log-log correlation between these two parameters exists in the mouse, rat, rabbit, man and horse. This work was extended by Yousef [7.5.6] to some other species including small and large mammals living in the desert. Only the kangaroo rat is exceptional. Its unique water metabolism has been the subject of many investigations. The dairy cow occupies a special place, having a water turnover comparable with that of a rabbit. This cannot be ascribed to the physiological effects of being a ruminant animal since the correlation between body weight and water turnover does hold for goat, sheep, reindeer and other ruminants.

A slower component has been established for the kangoroo rat [7.5.7], and for the lactating [7.5.8] and non-lactating dairy cow, as shown in Table XXIV. Both values have been derived from continuous administration experiments. Figure 4 shows the evolution of tritium activity in milk of a lactating cow which had been ingesting tritiated water for nearly 6 weeks, quite long enough for equilibrium conditions between intake and secretion into milk water to occur. After discontinuing the administration of tritiated water, a biological half-time of 4 days of tritium in milk water was found. The slower component represents less than 1% of the tritium activity at equilibrium, and is of limited importance for the total body dose from tritium. A similar situation exists in the kangaroo rat [7.5.7] and in man [7.5.9].

The possibility of an isotope effect occurring in the passage of tritium across body membranes has been examined by various authors. In the case of tritiated water, the lung has been found to be the only site where discrimination is significant, the specific activity in the expired air being less than in the body water. In mice and kangaroo rats, the specific activity in the expired air was found to be 0.65 and 0.44 respectively of the mean tissue water specific activity [7.5.10], In our own experiments on lactating cows, calves and pigs, differences in specific activity of tritium in its passage in liquid form through the body have not been observed.

3.4.1.2. Incorporation of tritium in organic constituents


These have been identical with those described for the determination of the biological half-life. Both single and continuous dose studies on small laboratory and domestic animals have been carried out.


The radiochemical analysis of organically bound tritium (OBT) after administration of tritiated water requires special attention because of the high tritium activity of the water fraction relative to that in the OBT fraction. There-fore, complete evacuation of THO, for example by drying under vacuum conditions, is essential. Combustion of the sample is another critical step. It has been carried out originally by the oxygen flask combustion technique, first introduced by Schoniger. The availability of automatic sample oxidizers has facilitated greatly this part of the analysis. Nevertheless, we feel that adoption of a standard proce-dure of proven reliability is essential in order to obtain reproducible analytical results.


(i) Incorporation in organic matter

A cow that had been given orally a large single dose of tritiated water had to be killed three weeks afterwards. Tritium activities were determined in the tissue-free water (TFWT) and in the dry tissue solids, the OBT fraction. The ratio of the specific activities of these two fractions varied from 0.19 (intestinal wall) to 0.63 (liver), with intermediate values for muscle (0.33) and kidneys (0.44). The organic milk constituents (casein, lactose, milk fat) also contained tritium, and the highest values were found from 12 to 24 hours after ingestion of THO. Expressed as a percentage of the ingested tritium, secreted per litre of milk, the transfer coefficient for milk water is about 0.2% when milk activity is at a maximum and two to three orders of magnitude smaller for the organic constituents. In mice, killed 50 days after an acute exposure, the highest tritium levels were observed in brain tissue, followed by muscle, kidney and liver [7.5.10], Radwan and co-workers [7.5.11 ] determined 3H activity in various rat tissues at different inter-vals after a single subcutaneous dose of THO. Maximum incorporation was found between days 4 and 7 after dosing, with the lowest levels in muscle and the highest activity in liver. Species differences and time-dependent factors may influence tritium incorporation into tissues after an acute exposure.

Conditions of chronic intake of tritiated water are more likely to occur under practical circumstances, and therefore studies involving continuous administration are of greater interest. In mice, kept on THO 40 -147 days, the specific activity (SA) of the OBT fraction from liver and testis was 0.25 and 0.40 respectively of the SA of tissue water [7.5.12]. The higher ratio for testis could not be explained. Liver DNA was shown in this study to contain tritium in all four bases. A mean value of 0.25 for the OBT/TFWT specific activity was also found in 11 organs of a baby goat whose mother had been ingesting daily tritiated water (46.8 jitCi/ltr) during the 124-day gestation period [7.5.13]. Similar values have been obtained for organs of calves after chronic ingestion of THO. The mean value is 0.20, the


TABLE XXV. AVERAGE TRANSFER COEFFICIENTS FOR MILK AND MILK CONSTITUENTS, EXPRESSED AS PERCENTAGE OF THE DAILY TRITIUM INTAKE, SECRETED IN ONE LITRE OF MILK, AFTER CONTINUOUS INGESTION OF THO

Product Milk

THO

Dry

matter

Milk

fat Lactose Casein Albumin Total

Transfer coeff. (%) 1.50 0.067 0.026 0.029 0.011 0.002 1.57

TABLE XXVI. RATIO OF THE SPECIFIC ACTIVITIES (pCi3H/gH) OF SOME ORGANIC MILK COMPONENTS AND OF MILK WATER IN A LACTATING COW AFTER CONTINUOUS DAILY INGESTION OF THO

Component Total dry matter Lactose Milk fat Casein Albumin

SA Component

SA Milk H20 0.49 0.60 0.40 0.30 0.32

TABLE XXVII. DISTRIBUTION OF TRITIUM IN ORGANIC FRACTION OF CALF ORGANS (%o OF TOTAL ACTIVITY INGESTED)

Organs 3H administered in Organs

Water Milk powder

Kidney 0.033 0.62

Spleen 0.020 0.33

Brain 0.023 0.34

Lungs 0.051 0.78

Muscles 2.46 35.6

Tongue 0.030 0.43

Heart 0.046 0.90

Liver 0.14 3.44

Sum 2.803 42.44


Days

FIG.5. Tritium activity in various milk fractions (milk H^O, total dry matter, milk fat, casein and lactose) after administration of organically bound tritium (tritiated hay) to two lactating cows.

range 0.19—0.25 in five organs. The same organs of pigs show lower values (mean: 0.13, range: 0.10—0.15) [7.5.14]. There is no apparent reason for these differences. It may be that equilibrium conditions between intake and excretion were not obtained in the experiments with pigs. These studies show reasonably good agreement with earlier experiments [7.5.15].

The incorporation of tritium into the organic constituents of cow's milk is of special interest because of the importance of milk for the contamination of the food chain. Table XXV shows the transfer of tritium into various milk components at equilibrium after continuous ingestion of THO by a lactating cow, expressed as the percentage of ingested tritium secreted per litre of milk. It


TABLE XXVIII. TRITIUM-INDUCED CHROMOSOMAL ABERRATIONS IN RUMINANTS

Animal

Tritium Aberrations observed

Percentage of

abnormal cells

Animal Source

Activity

ingested

(MCi)

Chro

matid

gap

Chro

matid

bre

ak

1 Is

o-chro

matid

gap

Chro

mosom

ial

fragm

ent

Percentage of

abnormal cells

Cow No. 1

Calf No.l

Goat No.l

Hay, grass,

water

In utero +

milk

Water

465 741

? + 15.2

21 400

1

7

1

- 2

2 1.5%

4.0%

0.5%

Cow No.2

Goat No.2

Control

Control

0

0

2

3

-

-

1.0%

1.5%

follows from Table XXV that the overall transfer for milk is a little over 1.5% of the daily ingested tritium per litre. Milk dry matter, which constitutes about 13% of milk, contains only 4% of the tritium activity. Calculation of the ratio of the specific activities of milk constituents, and of ingested water and feed (Table XXVI) indicates the measure of incorporation of tritium into organic material. Consider-able differences between the various organic milk components can be noted in this respect, the difference between the values for lactose (0.60) and for the two milk proteins, casein (0.30) and albumin (0.32), being particularly noteworthy. Glucose is the only precursor of lactose, and in ruminant animals it is newly formed from propionic acid. This may explain why more than half the hydrogen of lactose originates from water.

(ii) Biological half-life

After discontinuing the daily intake of THO by the lactating cow, tritium activity in the milk water decreases with a half-life of 4 days (Fig. 4), which is in close agreement with the values observed after a single dose. A similar value can be determined for the organic milk constituents over the period of three weeks following the end of THO administration, as represented in Fig. 4. This


TABLE XXIX. TRITIUM RELEASES FROM THE KARLSRUHE NUCLEAR RESEARCH CENTER VIA EFFLUENT AIR AND WATER FOR THE PERIOD 1969-76

Pathway

Tritium release (Ci)

Pathway

1969 1970 1971 1972 1973 1974 1975 1976

Exhaust air

Liquid effluents

1600

440

2100

602

1900

735

1200

2226

1900

1580

1600

770

1600

2821

1200

4024

is what one would expect since the organically bound tritium will be derived entirely from tritium in the body water pool. The milk proteins are behaving somewhat differently in that a slower component becomes visible after about ten days. Analyses are in progress to clarify this point. Kistner [7.5.16] has reported different half-lives for whole milk (5 days) and dry matter (7 days) after a daily intake of THO for 40 days. This is an observation which needs to be verified since there is no obvious physiological reason for the differences in half-life observed. Most of the organic material in milk is newly synthesized by the mammary epithelial cells from blood precursors. These precursors originate for the greater part from the animal's feed, and presumably would not contain any tritium before being taken up by the animal.

In mice longer biological half-times of 11 days [7.5.10] and of 90 days and longer [7.5.15] have been reported. These were interpreted as representing excretion of tritium incorporated into organic tissue components.

3.4.2. Metabolism of tritium administered as organically bound tritium (OBT)

3.4.2.1. Incorporation of tritium in organic matter


As has been discussed in the preceding section, administration of THO leads to tritiation of organic components in animal tissues and organs, and in animal products such as milk. Thus, when considering the question of how much tritium becomes incorporated after ingestion of organically bound tritium by an animal, e.g. through its feed, it is necessary that no THO reaches the animal or, if it does, that the amount of it be known. In the latter case, it is preferable that the amount of THO is small relative to the organically bound tritium. Another point to remember is that a relatively substantial amount of homogeneously tritiated feed


TABLE XXX. TRITIUM RELEASES BY THE KARLSRUHE NUCLEAR RESEARCH CENTER IN 1975 AND 1976

Emitter

Height of

emission

Tritium release

(Ci)

(m) 1975 1976

FR 2 (44 MW(th), 99 285 170

D20-moderated) 99 285 170

MZFR (200 MW(th), 99.5 765 703

D20-moderated) 99.5 765 703

WAK (Reprocessing plant,

40 t/a throughput, 60 1000a 1000a

3 X 104 MW d/t)

FERAB (incineration

facility for solid 70 467 213

radioactive wastes)

Decontamination plant 1 Q 53 73 for liquid wastes

1 7 53 73

Sewage treatment plant

(a) Evaporation ~ 2 ~ 2b ~ 3b

(b) Liquid effluents - 2821 4024

Several minor emitters ~ 10 5 20

a Authorized value. b Estimate based on an average evaporation rate of 1 mm/d for 800 m2 of uncovered surface.

should be available for equilibrium conditions to be reached. Obviously, these kinds of investigations are not easily realized experimentally. A few studies, partly of a preliminary character, have been carried out within the framework of the IAEA's Co-ordinated Research Programme. These are briefly discussed below.


Two calves were fed tritiated milk powder for 28 days after which they were killed. Various organs and tissues were analysed for tritium content, and the results are shown in Table XXVII. Similar data from calves that had been ingesting THO for periods of between 4 to 6 weeks are given also for comparison. The much higher incorporation of 3H into eight organs and tissues after ingestion of


OBT in the feed is obvious: on the average, fifteen times more tritium has been incorporated, representing 4.1% of the ingested tritium. Pigs fed tritiated milk powder incorporated 4.2% of the ingested tritium in a slightly different set of organs, and nearly 11% after feeding on tritiated potatoes [7.5.14]. This would appear to illustrate clearly the importance of the tritiated 'precursor'.

Figure 5 shows incorporation of 3H in various milk components after feeding tritiated hay to two lactating cows for eight days. Although equilibrium conditions were almost certainly not reached in so short a period of time, the following conclusions may be drawn. Firstly, that milk fat and casein contain fifteen and ten times more 3H on a weight basis than milk water, whereas lactose has a surprisingly low tritium content. Secondly, the half-life of tritium in milk fat, casein and milk dry matter is about two days for the first week after stopping the feeding of tritiated hay. For milk water, a value of four days is found. After about two weeks, a slower component of eight to ten days for the decrease of tritium activity in milk fat appears. No data are available for the other milk components.

The results reported here for the incorporation of tritium, taken up as OBT, clearly are of a preliminary character. Plans are being made to continue this line of research where extension of existing knowledge is desirable.

3.4.3. Incorporation of 3H in the nucleic acids of animals

The analysis of the organic matter of pigs receiving a single intrapectoral injection of 39.3 mCi THO showed that in liver the radioactivity was found in the different fractions isolated using the technique of Schmidt-Tannhauser.

With regard to the essential biological properties of the DNA, it was very important to know whether tritium was really associated with the DNA and in what proportion.

The liver DNA of pigs ingesting daily 28.4 /uCi THO during 27 days was prepared by gel filtration and the DNA-containing fraction analysed by centri-fugation in CsCl gradient. In one case, the radioactivity is carried by molecules having a density different from that of DNA, in the other case no radioactivity higher than the normal background has been observed.

Results of preparation and analyses of the liver DNA from pigs having ingested tritiated potatoes show that no radioactivity higher than the background is in the DNA-containing fractions after molecular normal sieving on sepharose 4B nor after ultracentrifugation in CsCl gradient. The same results were obtained from analysis of DNA spleen (actively dividing organ) of pigs having ingested tritiated powder milk.


3.4.4. Cytogenetic

The aim of this study, performed in the Genetic Laboratory of the Belgian Nuclear Centre, was to determine if tritium ingested under various forms (tritiated water, grass, hay and milk) could induce chromosomal aberrations in ruminants.

Two cows, one calf and two goats were observed. The nature and amount of tritium ingested are shown in Table XXVIII.

For the study of the chromosomes, two blood samples of each animal (0.4 ml of blood heparinized) were incubated at 37° C during 4 5 j hours in 5 ml of medium F-10.6 The cells were then incubated for a further 1\ hours in the presence of colchicin. For each animal, 200 metaphases were chosen and structure aberrations of the chromosomal or chromatidal type counted.

The dose to tritium ingested as drinking water by cow No.l equals an exposure of 50 mrem daily during one month and the tritium ingested by goat No.l an exposure of 15 mrem daily during A\ months. Our results show clearly that ingestion of tritium as tritiated water (goat No. l ) and as hay or grass (cow No.l) , in amounts 100 to 1000 times higher than after ingestion of drinking water or forage contaminated by radioactive effluents released by nuclear facilities, do not increase the level of chromosomal aberrations in the lymphocytes of ruminants.

3.5. DEPOSITION ON SOILS FROM TRITIATED ATMOSPHERIC EFFLUENTS

Several thousands curies of tritium are released every year from the Karlsruhe Nuclear Research Center via the effluent air and water. It is therefore obvious that the consequences of these releases should be investigated in a comprehensive monitoring programme. This programme extends beyond the immediate and more distant environment of the Karlsruhe Nuclear Research Center.

Tritium is released to the atmosphere mainly through several exhaust stacks and is almost exclusively in the form of tritiated water vapour. The various forms of tritium gas released have not been detected and are estimated to be insignificant. In the effluent water, tritium from all sources at the Nuclear Research Center is discharged via the sewage treatment plant.

Table XXIX is a survey of the tritium releases via effluent air and water from 1969 to 1976. Table XXX is a break down of releases from the emitters of the Nuclear Research Center and indicates the heights of the sources above the ground.

Precipitation samples are of special interest because their tritium concen-tration together with the amount of precipitation govern the tritium activity fed into the soil and, consequently, have an impact on all the other media. The mean

6 HAM, R.G., Exp. Cell. Res. 29 (1963) 515.


values of surface load at the four collecting stations located on the site of the Karlsruhe Nuclear Research Center clearly exceeded the values for the more distant environment. This is due to the tritium emissions from the Nuclear Research Center.

Establishing the difference of surface load values applicable on the site and outside the Nuclear Research Center gives a mean surface load of about 0.3 Ci/km2 from releases. The major part of the surface load is caused by fall-out.

If the calculations are based on a mean surface load of 0.3 Ci/km2 from releases, a total load of about 1 Ci is obtained for an area of 1 km radius around the Nuclear Research Center. This means that the portion of 5 X 10"4 of tritium released to the atmosphere is dispersed by precipitation in this area. It is not possible to detect a surface load from releases at a greater distance from the Nuclear Research Center because the variations as a function of time and location of surface load from fall-out are greater than the small influence expected to be exerted by the Nuclear Research Center in this more distant area. The situation will be unaltered unless the measuring accuracy can be substantially improved.

4. PREDICTIVE MODELS OF TRITIUM BEHAVIOUR

4.1. MOVEMENT OF TRITIUM IN THE ENVIRONMENT

Tritium released into the environment enters the water cycle and thus is dispersed worldwide. Figures 6 and 7 present a simplified model of the transport of tritium in the environment.

4.1.1. Air path The diffusion of tritium in the atmosphere can be described with sufficient

accuracy by familiar dispersion formulae. The equation for ground level air concentration values C (Ci/m3) is

C = Q(jroyo zu)-1 exp[ - (y 2 / 2a 2 + h2 /2a2)] (1)

where:

Q is the source strength (Ci/s) u is the average wind speed (m/s) h is the height (m) of the source above ground. y is the lateral (cross wind) distance (m) from the plume axis

The horizontal and vertical dispersion parameters a y and a z , respectively, are functions of the downwind distance.

Equation (1) is valid for release periods of one half to one hour and can be verified in the experiment. At the Karlsruhe Nuclear Research Center diffusion experiments have been performed to determine the parameters a y and CTz. Initially, tritiated water vapour was used as a tracer. At present, non-radioactive organic compounds are used as tracers. One result of previous experiments was that the tracer substances used did not differ in their atmospheric diffusion behaviour, which confirms the applicability only postulated originally in Eq.(l) to the dispersion of tritiated water vapour in the atmosphere. A significant result is the shifting towards the source of the position of the radial concentration maximum as well as the increase in the amount of this maximum relative to the values expected on the basis of the diagnosed Pasquill diffusion categories. Another result was the finding that a y and az depend on the surface roughness caused by buildings and vegetation.

However, the impact on the environment from tritium releases is not so much determined by temporary dispersion conditions, but rather by the long-term diffusion factor. The latter can be calculated for the respective

6 9

70 PREDICTIVE MODELS

GASEOUS

TRITIUM

EFFLUENTS

TRITIUM

EMITTERS LIQUID

EFFLUENTS evaporation

" - " - T - - - - - - - G R O U N D W A T E R ~ ^ JT _ r _ 1

FIG.6. Simplified model of transport of tritium in the environment.

weather conditions from temporary dispersion factors, taking into account the meteorological data applicable to the area concerned. The experimental verification of the long-term diffusion factor, based on available tritium measurements, is not possible because the prevailing conditions are not well defined.

4.1.2. Water path

Tritium released via the waste water may result in a radiation impact on persons in several ways. The paths to be considered for drinking water and breathing air are:

seeping into the groundwater from leakages in sewage treatment plants and in the sewer system as well as seeping from surface waters;

evaporation on uncovered water surfaces while contaminating the environment via the air path.

With respect to the influence of temperature, wind speed and the difference between the saturation pressure and pressure prevailing of the water vapour in the air, the determination of the momentary evaporation rate is the most difficult problem. The diffusion via the air path has been treated in Section 4.1.1.

By contrast, it is hardly possible to estimate with an acceptable accuracy the radiation impact from seeping. Experimental investigations are necessary in each individual case. Generally, leakages occurring in sewer systems are not adequately taken into account. However, if such systems carry tritium-bearing liquid effluents, contaminations are measurable. Tritium which has reached the


Liquid Fall-out of Gaseous Effluents Nuclear Tests Effluents

FIG. 7. Scheme of tritium transport in the environment.

groundwater is diluted at a very slow rate only. Periods of months and years must be expected. Also the groundwater flow velocity is low (order of magnitude 1 m daily) so that the diffusion of a possible contamination is very slow or the contamination is deluted after a relatively long period only.

Surface water contaminated with tritium may entail radiation exposure also via the food chain on different exposure paths. The following paths are the most important to be taken into consideration:

Drinking water of cattle - milk or meat Fodder crops — milk or meat Irrigation — vegetables A useful estimate of radiation exposure for all exposure paths combined

is obtained if one assumes that all the water taken up has the mean tritium concentration C of the sewer system. The following formula applies for the radiation exposure D:

( r e m ml \ ( 2 )

In Eq.(2) the quality factor (QF) was set at 1.7.

4.1.3. Behaviour of tritium in the air/water interface

It is a general observation that when tritiated water is exposed to the atmosphere, the tritium specific activity in the water phase decreases gradually.


In order to explain this phenomenon, a mathematical model is developed taking into account the natural evaporation and condensation processes taking place at the surface of the water layer. The model indicates that the decrease in specific activity of tritium in water is dependent on the depth of the water column, humidity and the temperature of air and water. Laboratory and field experiments were carried out to test the applicability of the model and a close agreement is found between the values predicted by the model and the observations [7.6.21 ].

4.2. TRITIATED WATER IN SOIL

Water in soil can be regarded as segmented into different compartments, e.g. free water, capillary water, etc. The vertical movement of a lens of tritiated water, and the broadening that occurs with time, depend on a complicated relationship between environmental conditions and various water compartments. Each compartment has its special set of characteristics which determine water movement through and water behaviour in it. In the simplest case, unobstructed water percolation is possible primarily through the soil free space. Movement rates of this 'free water' are governed by soil texture and structure. In many soils, free water is also distributed throughout the soil by passage through fractures, holes caused by insects, worms, reptiles, and mammal activities, and through lumens created by decayed plant or animal tissues. The rapid dispersion of tritiated water through voids and irregularities in the soil structure is often responsible for great and inconsistent variations in a contamination depth profile. Investigations regarding this fast irregular dispersion of tritiated water have been conducted by various authors: Dixon and Peterson [7.6.1], Jordan and co-workers [7.6.2], and Sasscer and co-workers [7.6.3]. A correction for the water movement model of Sasscer and co-workers [7.6.4] was derived by Jordan and co-workers [7.6.5],

Water held as a thin layer on the surface of soil particles and in capillaries formed between soil particles and in decaying organic material is termed capillary water and, as such, constitutes a discrete compartment. Capillary water can move via mass flow whenever a water potential difference occurs in the capillary system as well as via molecular diffusion. Both modes of movement cause a broadening of the contaminated water lens. Molecular diffusion is non-directional and its extent depends primarily on the mean free path length and on the temperature. Most studies on the diffusive movement of water in soil systems have focused on vertical movements, since horizontal diffusion within a uniformly contaminated area is of no real consequence in terms of water availability. Yet horizontal movement may also be responsible for loss of tritium from a contaminated site to uncontaminated areas.


The sites of exchangeable cations on clay and organic matter can be classified as a separate compartment for the residence of tritium. Movement rates into and out of this compartment depend on the number of exchange sites, on the types and numbers of cations present, and on the soil-water content. The exchange of tritium in the free and capillary water compartments with the cation exchange compartment is relatively rapid; therefore, exchange reactions are usually not important for the distribution pattern of tritium in soil. However, under a combination of certain conditions, e.g. when the tritium lens resides in the root zone, the soil is relatively dry and transpiration demands are high, this compartment can become significant. When Jordan and co-workers [7.6.5] tested a water movement model, corrections based on tritium exchange with this compartment were required to fit their experimental data to the theoretical model. This was especially apparent towards the end of the growing season.

Tritium may also become an integral part of the clay micelle and reside in the form of hydroxyl groups attached mainly to aluminium and magnesium atoms. These hydroxyl groups exchange slowly with water from other soil compartments. This slow exchange rate renders the effect of this compartment on movement of tritiated water through soil and its availability to plants rather unimportant. Exchange in this compartment may be a useful tool in clay mineralogy and in geophysical studies since it allows the identification of specific reactions and may be useful in identifying certain time-dependent interactions. There have been studies regarding the possibility of isotopic fractionation in the exchange of tritium and deuterium with the clay water compartment. Stewart [7.6.6] reported fractionation ratios as high as 3 : 1 for a type of kaolinite clay, but in more recent studies he was unable to repeat these observations [7.6.7] and instead showed that the highest ratios were near one. Additional discussion of exchange in this compartment can be found in clay mineralogy texts and specifically in articles by Rabinowitz and co-workers [7.6.8], Helevy [7.6.9], Corey [7.6.10], and Coleman and McAuliffe [7.6.11].

Soils contain varying amounts of organic material (humus), most of which is derived from cellulose via degradation processes. This organic material contains exchangeable hydrogen which is bound to oxygen (and to a much smaller degree, to nitrogen). The amount of exchangeable hydrogen in this compartment depends on the amount of organic material present, on its degradation mode and on soil pH. These hydrogens exchange rapidly with HTO, thus slowing the downward movement of a tritiated water lens. However, soils high in organic material generally occur in areas where precipitation and percolation rates are high. Although in principle the interaction of tritiated water with the soil organics compartment has an effect on tritium movement in soil, it is relatively small in most natural systems, due either to low organic


content or high percolation rates. However, additional information is desirable to clarify more fully the significance of this soil compartment to tritium movement in soil.

In addition to the effects of the various soil compartments on movement of tritiated water in soils, other factors can have a marked influence. When tritiated water is applied to a soil surface, a rapid initial evaporation loss will occur under most circumstances. The extent of this loss depends on a number of factors such as climatic parameters, soil composition and texture, and type and extent of plant cover.

Water loss via plant root absorption and transpiration is of great importance in most terrestrial ecosystems. Plants with a shallow root system such as many vegetables and cereals absorb all of their water from the upper few centimetres of the soil, whereas other plants with tap roots may absorb water at depths of 10 to 15 m. Thus, movement of a water lens to a metre below the surface may make this body of water unavailable to some species, but optimize absorption for others. Diversity in rooting patterns also results from differences in plant age, vigour, soil type and climate, and on the number and kinds of plants competing for space, water and nutrients. This great diversity makes it difficult to predict the importance of plant transpiration on the fate of a pulse of tritiated water. Although generalizations are possible and valuable each situation must be evaluated individually.

4.3. COMPARTMENTAL MODEL FOR TRITIUM PERSISTENCE IN THE SOIL-PLANT SYSTEM

Tritium is dispersed in the biosphere through its natural and artificial introduction into natural systems and becomes incorporated in different ecological compartments. Depending on the aim and scope of the applications, different modes of tritium transfer pathways and rates of incorporation in different ecological systems have been proposed. On the basis of a series of experiments conducted on a number of tropical trees, a compartmental model for tritium persistence in soil-plant systems has been attempted using the BESM-6 computer. The compartments are the tissue-free-water-tritium phase, the tissue-bound-tritium phase (labile component) and the non-labile component of tissue-bound-tritium, on the basis of two short-term and one long-term mean residence time values.

The experimental techniques consist of the introduction of tritium into soil-plant systems and analysis of the leaf samples (as well as flowers and fruit samples in certain cases) for tritium content at different time intervals.

Methods of calculation of transpiration rates in trees were based on the specific activity-time profile of the leaves, obtained after a single stem-injection


using tritiated water. The calculation of dry biomass has also been made possible from the tracer experiments taking into account the moisture content and peak arrival time for tritium. However, it has been established by many workers that this simplified form of mathematical analysis of the tracer kinetics is not suitable as a generalized function to explain the phenomenon of tritium persistence in the environment.

It is possible to resolve short-term and long-term components of tritium releases on the basis of the equation

At = A 0 e~ X t (3)

where A0 and At are the tritium activity values at the initial time and after t hours, and X(h -1) is the rate constant governing the release process. The TFWT and TBT fractions are independently fitted into two components, and the corresponding mean residence time values (1/X) are calculated for a set of trees.

However there are three compartments (TFWT, TBT-labile and TBT-non-labile) which are interdependent and not independent, as detailed in the following exponential polynomial:

A t = A 1 e ~ x ' t + + A s e " ^ 1 (4)

where At is the tritium activity at any time t after injection; X1; X2 and X3

are the rate constants governing the release patterns of TFWT, TBT-labile and TBT-non-labile fractions; and A l5 A2 and A3 are the coefficients for the three terms.

Data processing can be handled on the basis of a single exponential model with the experimental values obtained. The values are tested for a least-square fit for a linear function in a semi-log plot activity time curve, from whose slope and intercept the half residence time and mean residence time can be obtained. The values obtained on the basis of TFWT experiments and TBT experiments are handled independently.

Equation (4) can be used for resolving the curve into two short-term and one long-term component. The interdependence of TFWT and TBT-labile fractions is highly pronounced as both are short-term components, and the contribution to these values from the TBT-non-labile fraction is quite negligible.

The raw experimental data needs some processing before it is tested for Eq.(3), since it is possible to fit the curve with values obtained at equal intervals of time. In experiments where such values are not available, it is possible (and necessary) to generate interpolated data for the same. The basic assumption in such a programme is that the profile is linear in a semi-log plot (i.e. governed by a single exponential model) between the neighbouring points in time. From


the immediately preceding and following experimental points, the values for the interpolated co-ordinates can be generated, after determining the slope and intercept of the line joining the two neighbouring points in the activity/ time profile.

Computer analysis of the above data on the basis of Eq.3 yields two short-term components and a third long-term component.

4.4. TRANSPORT IN PLANTS

Plant-water relations have been the subject of extensive investigations and elaborate mathematical models have been developed to describe both water stress and water movement in plants [7.6.22]. Under mass flow conditions (i.e. transpirational water movement through the xylem), HTO moves at the same rate as H 2 0 . In diffusional flow (i.e. evaporation or intracellular movement), HTO moves at a slower rate than H 2 0 because of its larger mass. As previously indicated, these differences are so slight and water movement in plants so dependent on mass flow, that diffusional differences are inconsequential and are generally considered unimportant in describing tritium movement in plants and soil. Therefore, the net movement of tritiated water can best be described by systems developed to identify and define water movement.

4.4.1. Estimation of biomass

The basic aspects of tracer theory first described by Steward [7.6.12] and Hamilton [7.6.13] and later expanded by Bergner [7.6.14-7.6.17], Zierler [7.6.18], Ljunggren [7.6.19], and Orr and Gillespie [7.6.20] are pertinent to the analysis of these tritium tracer data. The well-developed theory of tracer dynamics in flowing systems permits determination of pool sizes, flow rates and perhaps other kinetic relationships such as sub-pools and their turnover rates. The form of the flow equation is

where M is the total activity of tracer (dis/min), F is the flow rate of the system (ml-h_ 1) and f(t) is the activity of the tracer at the point of exit from the system at any time after labelling.

Since the total activity in the system (M) is fixed by the experimenter, and the activity/time relationship is determined in the experiment, flow rates

oo

(5)

o


can be easily obtained from this simple equation. Equation [5] is the basic Steward-Hamilton relationship that has been used widely to determine flow rates in circulatory systems of mammals and rates of turnover in various bodies of water.

It is also possible to determine biomass from the same data set using relationships described by Zierler [7.6.18], who derived an expression for estimating pool size in flowing systems. The method of biomass determination is to estimate the water pool (V) of the organism or population (as in grassland) by tracer methods, and then convert this to green biomass by a simple water content measurement. Since the water content is obtained during the analysis of samples collected in the tracer experiment, all the required data are available.

Zierler's equation is:

C = F X Tm (6)

where C is the pool size (ml), F is the flow rate ( m l h - 1 ) , and Tm is the mean time of the tracer in the pool V.

The mean time (T m ) of the tracer in the pool is derived from the specific activity time curve and is equal to:

Equation (6) may be used to determine grassland transpiration because the pool size can be measured conveniently by total harvest and drying of a unit area of vegetation, and the mean time (T m ) is obtained from the tracer experiment data. If all the standing green biomass per unit area is harvested in the tracer experiment, the required data to calculate transpiration in grassland by the following equation is available:

where F is the flow rate of transpiration from grass stand (ml h"1 -m'2) , Vs is the grassland water pool (ml m~2), and T m is the mean time of water in the pool (h).

It is not necessary in grassland experiments (as it would be in a tree experiment) to know precisely the total activity in the system at T0, and therefore sampling is designed to provide an accurate measurement of the mean time of the tracer in the pool. Isotope mass effects are small and are not expected to alter kinetic relationships at the level of these experiments.


ETp = a Ep [l + X ( 0 )]

tip tiji (on)

FIG. 8. Tritium residence half times in transpiration water (vine, apple tree) and ET,

4.4.2. Tritium's residence half times in the transpiration water and potential evapo-transpiration

The losses of tritium in plants by transpiration are dependent on the physical and biological phenomena which regulate their requirement of water.

In a mediterranean climate, during seven days from April to September 1976, after tritium-water injection in apple and vine trunks, a good correlation has been found between the residence half time (T 1 / 2) of 3H in the transpiration water and the potential evapo-transpiration (ET p) (Fig.8).

Using this factor it is possible to assess the global requirements of water of the growing plant in a given location during a given period. This is therefore an important climatic characteristic: T1 /2 = - 7 . 7 ETp +44.3 (r = —0.89) with T1/2 in hours and ETp in millimetres (piche).

The knowledge of this factor during a given period and the particular circumstances in the region concerned might enable a forecast to be made of the residence half time of 3H in the transpiration water of plants.

a = Shelter coefficient Ep = Piche evaporation (mm) 0 = Tx + 3 Tn

4

Tx = Maximum temperature Tn = Minimum temperature

5. CONCLUSIONS AND NEEDS

5.1. OVERALL CONCLUSIONS

The data produced by the various laboratories participating in the programme are unique because the investigations have been carried out in a co-ordinated manner from the early stage of planning.

The results presented allow the user to predict the behaviour of tritium, released as tritiated water, in the major terrestrial ecosystems of the world; the results of a few investigations on aquatic organisms are also reported.

The experimental results on the behaviour of tritium released in elemental or organic forms stresses the importance of the chemical form of tritium released on its subsequent environmental behaviour.

Some mathematical modelling on the tritium transfer has been also tentatively carried out, showing the benefit of a close co-operation between the scientists engaged in field studies and the modellers.

5.2. FUTURE NEEDS

By the turn of this century, tritium may be a radionuclide of deep concern in the environment. In developed countries, new types of reactors (HTR-fusion) and in developing countries, research and power reactors (PWR) will be operated. High tritium activities will be handled which cannot be done without losses contaminating the environment. Field studies have to be undertaken on residence times of tritium to obtain more data in different types of ecosystems. The elements of human diet have to be systematically investigated.

Residence time has to be measured in the various soil components (sand, clay, loam and organic matter) including the influence of microscopic flora and fauna.

Studies on the relationship between the residence time of TBT and the growth cycle and the size of plants should also be performed; the correlation between evapo-transpiration and residence times has to be investigated under various climatic conditions. This could lead to a better water management for food crops. With respect to plant physiology, the manner in which HTO in the air humidity reaches plants needs to be investigated.

Studies on TFWT in plants and trees have to be continued under high precipitation conditions (monsoon) as well as penetration into soil under varied soil compositions. Mathematical models have to be developed to understand the pathways of TFWT and TBT for varying environmental conditions. Five structures arising from variation in transpirational rates during a day have also to be considered for these models.

79

80 CONCLUSIONS AND NEEDS

A particular emphasis needs to be given to aquatic systems. Baseline levels in the environment have to be determined, especially in the

neighbourhood of nuclear sites. A good knowledge of the baseline levels and the pathways is necessary to implement a proper monitoring of nuclear facilities.

More fundamental studies are also required on the biological availability of tritium present in the various compartments of the environment: sediments, soils, plants, animals.

Investigations on the chemical forms of tritium released in liquid and gaseous effluents should be followed by research on the response of living organisms by exposing them to the different forms of released tritium (element, THO). The study of the kinetics of incorporation of tritium in the organic pool of living organisms and its possible isotopic effects merit special attention, particularly the kinetics of tritium in gaseous form (HT).

A specific emphasis should be given to the distribution of tritium in erythro-cytes and plasma of blood, milk and its constituents. This might be of use in evaluating by microdosimetric principles the dose levels received by all populations.

Tritium distribution in various items of human food need further study at different stages of growth of plants. Preliminary studies indicated a significant incorporation of tritium in protein carbohydrate and fat fractions of TBT compartments.

Emphasis should be laid on the incorporation in macromolecules such as nucleic acids and proteins. Little is known so far on the behaviour in the food chain of various labelled biomolecules. Thymidine may be incorporated directly into desoxy ribonucleic acid-forming chromosomes. Therefore, tritiated thymidine is hundreds of times more dangerous than tritiated water (based on activity).

6. ANNEXES

6.1. LIST OF LABORATORIES AND PROJECT TITLES

Country

Belgium

Finland

France

Germany,

Federal

Republic of

India

Mexico

Laboratory

Centre d'etude de l'energie

nucleaire,

Boeretang 200, B-2400 Mol

Department of Radiochemistry,

University of Helsinki,

Unioninkatu 35,

SF 00170 Helsinki 17

Section de radioecologie,

SERE - CEA, .

Centre d'etudes nucleaires

de Cadarache, B.P.I,

F-13115 St. Paul-lez-Durance

Gesellschaft fur Kernforschung mbH,

Abteilung Strahlenschutz und

Sicherheit,

Postfach 3640, D-7500 Karlsruhe

Health Physics Division,

Bhabha Atomic Research Centre,

Trombay, Bombay 400 085

Instituto Nacional de Energia

Nuclear,

Gerencia de Seguridad y

Salvaguardias,

Departamento de Radiactividad

Ambiental,

Avenida Insurgentes Sur 1079,

Apartado Postal 27-190,

Mexico 18, D.F.

Project title

Transfer of tritium in food

chains

(R. Kirchmann)

Tritium experiments in arctic

and subarctic ecosystems

(J.K. Miettinen)

Transfer of tritium in

cultivated vegetation in

mediterranean temperate

regions

(A. Grauby)

Investigation of tritium level

in the environment of the

Karlsruhe Nuclear Research

Center

(L.A. Konig)

Residence-time of tritium in

soils and plants

(S.D. Soman)

The cycling of tritium in

typical cultivation in the

Valley of Mexico

(J. Raul Ortiz Magana)

Netherlands Laboratory of Animal Physiology,

Agricultural University,

Haarweg 10, Wageningen

Transfer of tritium in

ruminants

(J. van den Hoek)

81

82 ANNEXES

Philippines

Thailand

Komisyon Ng Lakas,

Atomica Ng Filipinas,

Don Mariano Marcos Avenue,

Diliman, Quezon City

Office of Atomic Energy for Peace,

Vibhavadi Rangsit Rd,

Bangkhen, Bangkok-9

Behaviour of tritium in

various ecosystems

(N. Bustamente-Juan)

The cycling of tritium in

different types of ecosystems

(A. Yuthamanop)

United States Lawrence Livermore Laboratory,

of America University of California,

P.O. Box 808,

Livermore, CA 94550'

Movement of tritium in

ecological systems

(J.J. Koranda)

Environmental Protection Agency,

Environmental Monitoring and

Support Laboratory,

Box 15027,

Las Vegas, NV 89114

Behaviour of tritium in

biological systems

(G.B. Morgan)

International Atomic Energy Agency

The Scientific Secretaries of the co-ordinated research programme were:

P.J. West

L.F. Farges

1973-75

1975-78

ANNEXES 8 3

6.2. TABLES

The following tables (Tables A to H) give more information on the conditions of the

experiments conducted in the participating laboratories. They include also miscellaneous

results that could be of interest for radiological calculations.

TABLE A. PLANTS. DESCRIPTION OF THE ENVIRONMENT AND VEGETATION

Country Environment Vegetation type Mode of exposure

Belgium

Finland

France

Germany,

Federal

Republic of

India

Mexico

Philippines

Thailand

Temperate,

agricultural

Arctic-boreal,

native forest

Mediterranean,

agricultural

Temperate

Tropical, agricultural

and native plants

Temperate,

agricultural

Tropical,

agricultural

United States

of America

Tropical,

agricultural

Temperate and

arctic, native and

agricultural plants

Pasture, rye-grass,

sugar beet, potato,

clover, barley

Birch-pine,

birch shrubs

Apple, olive, citrus

trees, grapes

Grass, pines, spruces,

oaks, hornbeam

Garden species, native

trees, vegetables,

desert plants

Corn, beans, wheat,

tomato

Corn, tomato, rice,

cabbage, egg-plant,

mung bean, soyabean,

sweet potato

Garden plants,

coriander, Chinese

cabbage, corn, sweet

potato, common kale,

radish, cowpea

Grasses and sedges,

corn, native herbs,

trees

Spraying, hydroponic

culture

Spraying

Spraying, injection

Vapour

(uncontrolled)

Spraying, injection,

vapour (controlled)

Spraying,

residual tritium

Spraying

Spraying

Spraying, injection,

vapour exchange

8 4 ANNEXES

TABLE B. PLANTS: SPECIES AND EXPOSURE DETAILS - HTO EXPOSURE MODES

Country Common name Scientific name Mode of

exposure Concentration

Belgium Rye grass Lolium italicum Spray 1 mCi/m2

Potato Solanum tuberosum Spray 1 mCi/m2

Pea Pisum sativum Spray 1 mCi/m2

Barley Hordeum vulgare Spray 1 mCi/m2

Carrot Daucus carota Spray 1 mCi/m2

Pasture Spray 1 mCi/m2

Finland Spruce tree Picea excelsa Spray 3.6-6.0 mCi/m2

Pines Pinus sylvestris Spray 3.6-6.0 mCi/m2

Cowberry Vaccinium vitis idaea Spray 3.6-6.0 mCi/m2

Blueberry Vaccinium myrtillus Spray 3.6-6.0 mCi/m2

Birch Betula verrucosa Spray 3.6—6.0 mCi/m2 .

Grass Carex and various Spray 3.6-6.0 mCi/m2

France Grapevine Vitis vinifera Injection 2.35 mCi

Apple Prunus malus Injection 8.9 mCi

Grapevine Vitis vinifera Spray 2.09 mCi/m2

Olive tree Olea europaea Spray 1.37-1.87 mCi/m2

Orange tree Citrus sinensis Spray 0.43 mCi/m2

Germany, Pines Pinus sylvestris Vapour Varying concentration

Federal Spruce Picea abies Vapour 0.3-450 pCi/ml

Republic of (uncontrolled)

Hornbeam Carpinus betulus Vapour

(uncontrolled)

Oak Quercus robur Vapour

(uncontrolled)

India Badam tree Terminalia catappa Injection &

irrigation

1.17-5.0 mCi/m2

Mango tree Mangifera indica Injection &

irrigation

3-20 mCi/m2

Sapota tree Achras sapota Injection &

irrigation

—

Ashoka tree Saraca indica Injection &

irrigation

1.0 mCi

Cardina sebastina Injection &

irrigation

1.5-5.0 mCi

Bunya bunya Araucaria bidwilli Injection &

irrigation

1.5 m a

Arrant Gardenia florida Injection &

irrigation

2.5 mCi

ANNEXES 85

TABLE B (continued)

Country Common name Scientific name Mode of Concentration exposure

India Banana plant

(continued)

Coconut palm

Brab tree (Tad)

Casuarina

Mexico

Philippines

Bastard cedar

(Bakayan)

Arecanut palm

Cactus

Succulent sp.

Susuru

Mathachi Bhaji

Radish

P. Niruri

Mirchi

Grass

Maize var. H-20

Maize var. H-309

Beans var.

Canaris 107

Beans var.

Canario

Wheat var.

Pelon INEN

Tomato var.

Guafillo

Soyabean

Mung bean

Sweet potato

Musa indica K. Schum (var. sapientum)

Cocos nucifere

Borassus flabellifer

Casuarina equisetifolia

Melia azedarach

Areca catechu

Opuntia polyacantha

Euphorbia mili

Euphorbia trigona

Amaranthus viridis L.

Raphanus sativus L.

Phyllanthus fraternus

Capsicum fructescens

Zea mays L.

Zea mays L.

Phaseolus vulgaris

Phaseolus vulgaris

Triticum vulgare

Lycopersicon esculentum

Injection & irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Injection &

irrigation

Vapour

(controlled)

Spray

Spray

Spray

Spray

Spray

Residual tritium

1 -6 mCi

5.0 mCi

7.5 mCi

2.5 mCi

1.0 mCi

2.0 mCi

2.0 mCi

2.0 mCi

2.0 mCi

2.0 mCi

2.0 mCi

2.0 mCi

40 ftCi/ml

(liquid phase)

12 mCi/m2

19 mCi/m2

13 mCi/m2

19 mCi/m2

13 mCi/m2

30 mCi/m2

0.3-0.4 X 10"6

mCi/g (soil)

Glyciae max L. Spray

Phaseolus aurens roxb Spray

Ipomoea batatas L. Spray

1 mCi/m

1 mCi/m2

1 mCi/m2

86

TABLE G (continued)

ANNEXES

Country Common name Scientific name Mode of

exposure Concentration

Philippines Rice

(continued) Egg-plant

Bird rape

Tomato

Maize

Thailand Coriander

Chinese cabbage Brassica chinensis

Oryza sativa Spray

Solarium melongena L. Spray

Brassica Spray

campesiris L.

Lycopersicon Spray

esculentum Zea mays L. Spray

Coriandrum sativum Spray

Sweet corn

(maize)

Sweet potato

Tomato

Common kale

Radish

Cowpea

Shallot

United States Bur clover

of America

Corn (maize)

(Tropical tree)

(Tropical tree)

(Tundra)

Pea

Alfalfa

Ti (HT) exposure

Zea mays L.

Impomoea batatas

Lycopersicum esculentum L.

Brassica oleracea L.

(var. acephala DC)

Raphanus sativus L.

(var. radicula Pers)

Vigna sinensis Savi

Spray

Spray

Spray

Spray

Spray

Spray

Spray

Allium ascelanicum L. Spray

Lettuce

Medicago hispida

Zea mays L.

Dacryodes excelsa Sloanea berteriana

Pisium sativum L.

Medicago sativa

Lactuca sativa var. Grand Rapids

Vapour and

irrigation

Irrigation

Injection

Injection

Vapour and

immersion

Irrigation

Hydroponic

Immersion

100 mCi/m2

10 mCi/m2

20 mCi/m2

5 mCi/m2

10 mCi/m2

6.07 mCi/m2

8.00 mCi/m2

6.3 mCi/m2

4.1 mCi/m2

11.9 mCi/m2

15.7 mCi/m2

17.0 mCi/m2

9.0 mCi/m2

7.5 mCi/m2

8.7 piCi/ltr air

78.5 juCi/ml

5nCi/ltr air

ANNEXES 87

TABLE C. PLANTS: MEAN RESIDENCE TIMES - UNIQUE EXPOSURE

Mean residence time

Country Species (days) Remarks

1 II III

Belgium

India

Rye grass 1

Pasture 5

Rye grass 45

Solanium 45

tuberosum (tuber)

Pisum sativum (leaves) 25

(roots) 42

Hordeum vulgare (leaves) 38

Daucus carota (leaves) 17.6

(roots) 52

Beta vulgaris (leaves) 50

(roots) 38

Gardenia 2.5

florida L. (leaf)

Gardenia florida L. (flower)

Melia azedarach L. 1.2

Borassus 2.2

flabellifer L.

Cordia sebestena L. 0.4 1 0 - 1 1 16-27

Summer

Winter

OBT

OBT

OBT

OBT

OBT

OBT

OBT

OBT

OBT

Post-monsoon

period, both

irrigation and up-

take from nature

Post-monsoon

period, both

irrigation and up-

take from nature

Both stem injection

and root-soil

irrigation

Pre-monsoon root-

soil irrigated and

stem injection

Soil and stem over

two years; six

different occasions,

(pre-monsoon

periods)

88 ANNEXES

TABLE G (continued)

Mean residence time

Country Species (days) Remarks

I II III

India Terminalia catappa 0.5

(continued)

Areca catechu 1.33

Philippines Solanum 2.42

melongena 2.53

3.27

6.57

50.78

Lycopersicon 3.88

esculentum Mill 4.73

6.76

Thailand Brassica oleracea 11.5

(var. acephala DC)

Coriandrum 7.5

sativum

Zea mays L. 9.0

United States P. thunbergii 1.23(h)

of America Avena sativa 0.92(h)

Bur clover (liquid) 9.9

Dacryodes excelsa 7.6±0.4

Sloanea berteriana 2.7±0.13

26 - All seasons, all

modes

14.2 — Three different trees

of the same age

— - Roots

— — Stem

— — Leaves

— - Fruit

— — Fruit (two

components)

— - Fruit

— — Leaves

— — Stem

16.5

77

97

11

3.9

TABLED. PLANTS: BIOCHEMICAL DATA

Location Species Culture medium Methanol

Fractions (mCi/fraction)

TCA NaOH Technique

Belgium Acetabularia crenulata

Sea water

(1 AiCi 3H/ml) 180 3.0 11.0 Van Parys

Acetabularia mediterranea

Sea water

(1 /nCi 3H/ml) 186.4 0.9 0.9 Van Parys

Finland Pisum sativum L.

Tissue water

Dry matter

DNA

Free amino acids

Soil-

watering THO

(78.5 fiCi/ml)

TFWT

THO in soil

0.7

OBT

THO in soil

0.27

0.37

0.37

Heyn and

co-workers

India

TCA

(10%)

RSA'

Ethanol

(80%) +

Ethanol-

ether

1 in fractions

TCA (5%)

(DNA, RNA

& bases)

NaOH (2%)

(protein)

Scenedesmus obliquus

Fresh water

(0.6-4.1 juCi/ml) -

0.49 -

0.62

0.99 -

1.26

0.43 -

0.45 Schneider

a RSA - relative specific activity ratio: dis/min per g of H in cell constituents

dis/min per g of H in medium

90 ANNEXES

TABLE E. ANIMALS: SPECIES AND EXPOSURE

Country Environment Animal Mode of exposure

Belgium Temperate Pigs, goats, cows Injection, ingestion

Philippines Tropical Philippine tropical goat

water buffalo

Ingestion

Ingestion

United States

of America

(Las Vegas —

Livermore)

Temperate Cow, rat, rabbit, chicken Injection, ingestion

TABLE F. ANIMALS: EXPOSURE DETAILS

Organism Species and

number

Form

of 3H

Mode of

administration3

(S- C)

Dosage

Animal Pigs (3) THO Injection-S 39.3 mCi

(terrestrial) Pigs (3) THO Ingestion-C 568—766.8 pCi

Pigs (3) OBT Ingestion-C 21-154.5 pCi

Calves (3) THO Ingestion-C 25.6-40.4 mCi

Calves (2) OBT Ingestion-C 482 MCi

Cows (1) THO Injection-S 250 mCi

Cows (12) THO Ingestion-S 65-200 mCi

Cows (4) THO Ingestion-C 220-525 mCi

Cows (1) THO+OBT Ingestion-C 5.6 mCi THO—21 mCi OBT

Cows (2) OBT Ingestion-C (9 d) 615.7-654.1 iiC i

Water buffalo (1) THO Injection-S 10 mCi

Goats (1) THO Ingestion-S 5 mCi

Goats (4) THO Ingestion-C 46.4 juCi/1.

Mice THO Ingestion-S 100 nCi/g body wt

Mice THO Ingestion-C 94 + 4.8 nCi/ml

Kangaroo rats THO Ingestion-S 100 j/Ci/g body wt

Chickens (50) THO Ingestion-S 25 MCi

a S = Single dose

C = Continuous dose.

ANNEXES 9 1

TABLE G. ANIMALS: MEAN RESIDENCE TIMES

J. SINGLE EXPOSURE (THO) (a) Ingestion

Tissue or Tl/2 a Transferb OBT

Location Species product lst 2nd (%) TFWT

Belgium and Cow, lactating Milk (H2 O) 3 d 2.10"1

Netherlands Milk (fat) 3.7 d 2.10"3

Milk (casein) 4 d 4.10"4

Milk (dry matter) 3.5 d 7.10-3

(23 days after Muscle 0.30

ingestion) Intestine 0.19

Liver 0.63

Kidneys 0.44

Philippines Water buffalo Blood serum

Goat Urine 122 h

United States Cow, lactating Milk (whole) 3.0 d 11.1 d

of America Milk (water) 2.9±0.1 d 44±4 d (Las Vegas)

Milk (water) (Las Vegas)

Milk (protein) 2.1 + 0.6 d >50 d

Milk (fat) 3.3±0.4 d 61±43d

Cow, steer Blood serum 4.0±0.2 d 40+10 d

Goat Faeces 130 h

Blood serum

Milk

Water

Miniature (dry) 4.3±0.2 d

Mixed breed (lactating) 2.9±0.1 d; 5.3±0.2 d

Toggenburg (dry) 6.7+0.3 d; 10.4±0.7 d

92

TABLE G (continued)

ANNEXES

(b) Injection

Tissue or „ Transfer Location Species , t T,,, F product 12 (%)

Belgium Pig Urine 3.8-4.3 d

Belgium and Cow Milk (H20) 3 d 2.10"'

Netherlands Milk (fat) 3 d 2.10'3

Milk (casein) 3.5 d 3.10"4

Milk (lactose) 3.0 d 4.10"3

Milk (dry matter) 3.5 d 6.10"3

United States Chicken Muscle 4.6+0.3 d

of America

(Las Vegas) Blood serum

Egg yolk

4.6±0.3 d

3.1 ±0.1 d

Egg white 3.4±0.1 d 1.7 X 1

ANNEXES 93

TABLE B (continued)

2. CHRONIC EXPOSURE (THO) (a) Drinking water

Tissue or T1/2a Transfer6 TFWTf OBTg

Location Species ' iai\ product lst 2nd THO THO

Belgium Pig

Calf

Belgium and

Netherlands

United States

of America

Mice

Kidney 0.85 0.14

Lungs 0.87 0.13

Muscle - 0.10

Liver 0.81 0.15

TGI - 0.15

Kidney 0.97 0.20

Lungs 0.99 0.24

Muscle 0.97 0.27

Liver - 0.17

Brain 0.97 -

Spleen 0.98 -

Thymus 0.99 -

Gastro-intestinal 0.99 0.20

tract

Milk (whole) 1.62

Milk (THO) 3.3-4 d 11—12 d 1.55 0.98

Milk (dry matter) 4.5 d 0.067 0.49

Milk (fat) 4.5 d 0.026 0.40

Milk (lactose) 4.5 d 0.029 0.60

Milk (casein) 5.0 d 0.011 0.30

Milk (albumin) 5.0 d 0.0016 0.32

Urine 1.00 Faeces 0.96

OBTc

TFWT

Liver 0.252

Testes 0.448

Intestinal

0.278

9 4 ANNEXES

TABLE G (continued)

(b) Ingestion of organically bound 3H in food

Location Species Tissue or

product

T a 1 1 / 2

1 st 2nri

Transfer*1 TFWT

(%)

OBTJ

Belgium Pig

Calf

Belgium and Cow

Netherlands

Kidney

Lungs

Muscles

Liver

TGI

Kidney

Lungs

Muscle

Liver

TGI

H-organic H-organic

0.08

0.08

0.09

0.06

0.07

0.07

0.07

0.08

0.08

0.08

0.20

0.15

0.08

0.31

0.17

0.32

0.21

0.16

0.44

0.31

Milk (whole) 1.00 Milk (water) ~ 4 d 0.56

Milk (dry matter) ~ 2 d ~ 7 d 0.44

Milk (fat) ~2 d ~5 H 0.33

Milk (casein) ~ 2 d ~7 d

Milk (albumin) ~ 2 d ~ 7 d

Milk (lactose) ~ 4 d

Milk (water) ~ 5 d 0.03k

Milk (dry matter) ~ 2 d 0.3 l k

Milk (fat) ~ 2 d 0.45k

Milk (casein) ~ 2 d 0.40k

Milk (albumin) ~ 2 d 0.36k

Milk (lactose) 0.08k

ANNEXES 9 5

TABLE B (continued)

(c) Environment

Tissue or Tj/2a OBTc

Location Species product 1st 2nd TFWT

United States Kangaroo Body water 13.3+0.3 d 114±50

of America rats Brain 50+9 d 1.26+0.10

Muscle 41±8 d 1.58±0.10

Lung 31±5 d 1.58±0.10

Heart 29±3 d 1.63±0.09

Kidney 27±3 d 1.34±0.08

Liver 23±2d 1.43±0.08

a The notation 1st and 2nd refers to the two components into which the half time of tritium

can be divided. b The transfer coefficient is defined as the percentage of ingested tritium which, for a

particular milk constituent, is secreted in one litre of milk on the day of maximum activity. c - Organic bound tritium to tissue free water tritium. d Percentage of ingested tritium contained in each egg. e The transfer coefficient is defined as the percentage of the daily tritium intake, which for a

particular milk constituent is secreted in one litre of milk. f Tissue free water tritium to drinking water activity. 8 Organic bound tritium to drinking water activity. h The transfer coefficient is defined as the percentage of the daily tritium intake which, for

a particular milk constituent, is secreted in one litre of milk under equilibrium conditions. 1 Tissue free water tritium to organic bound tritium in food. J Organic bound tritium in tissue to organic bound tritium in food. k Data derived from an experiment in which equilibrium conditions were not reached.

96 ANNEXES

TABLE H. ANIMALS: BIOCHEMICAL DATA

Distribution (%) of 3H in various fractions

Treatment isolated from pig's liver (Schmidt-Tannhauser) Location Species . . . . (Total activity)

Ac. sol. Lipids RNA DNA Proteins

Belgium Pigs Injection

(7 weeks 39.3 mCi THO 29.0 9.6 34.3 17.7 9.5

old) Ingestion

766.8 ^Ci THO 55.2 5.1 32.2 5.5 2.0

Ingestion 21 nCi 3H potatoes 38.4 12.0 43.2 2.5 3.9

Ingestion

154 MCi 3I

powder milk

154 MCi 3H 26.8 20.8 7.9 18.1 26.4

6.3. SCIENTIFIC AND COMMON NAMES OF THE INVESTIGATED PLANTS

Acetabulars crenulata Species of unicellular marine green alga

Acetabularia mediterranea Species of unicellular marine green alga

Achras sapota Sapota tree or sapodilla

Allium ascalanicum Shallot

Amaranthus viridis Pigweed or green calalu

Araucaria bidwilli Bunya bunya

Areca catechu Arecanut palm or betel nut palm

Avena sativa Oat

Beta vulgaris Sugar beet

Betula verrucosa Silver birch

Borassus flabellifer RonieT palm, palmyra palm, brad tree

Brassica campestris Bird rape

Brassica chinensis Chinese cabbage

Brassica oleracea (var. acephala DC) Common kale

Capsicum fructescens Pepper, bush red

Carpinus betulus Hornbeam

Casuarina equisetifolia Horsetail tree or casuarina

744 ANNEXES

Chlamydomonas sp.

Citrus sinensis

Cocos nucifere

Cordia sebestena

Coriandrum sativum

Dacryodes excelsa

Daucus carota

Euphorbia mili

Euphorbia trigona

Gardenia florida

Glyciae max

Hordeum vulgare

Ipomoea batatas

Lactuca sativa (var. Grand Rapids)

Lolium italicum

Lycopersicon esculentum

Malus pumila

Mangifera indica

Medicago hispida

Medicago sativa

Melia azedarach

Musa indica K. Schum (var. sapientum)

Olea europaea

Opuntia polyacantha

Oryza sativa

Phaseolus aureus

Phaseolus vulgaris

Phyllanthus fraternus

Picea abies

Picea excelsa

Pinus sylvestris

Pinus thunbergii

Pisum sativum

Quercus robur

Raphanus sativus (var. radicula pers)

Saraca indica

Scenedesmus obliquus

Species of blue green-alga

Orange tree

Coconut palm

Aloe wood

Coriander

Tropical rain-forest tree

Carrot

Succulent species

Susuru

Arrant

Soyabean

Barley

Sweet potato

Lettuce

Rye grass

Tomato var. Guafillo

Apple

Mango tree

Bur clover

Alfalfa

Chinaberry tree, bastard cedar

Banana

Olive tree

Cactus

Rice

Mung bean

Bean var. Canaris 107 and Canario

Spruce

Spruce tree

Pine

Black pine

Pea

Oak

Radish

Ashoka tree

Species of freshwater green alga

98 ANNEXES

Sloanea berteriana

Solarium melongena

Solarium tuberosum

Terminalia catappa

Triticum vulgare

Typha angustifolia

Vaccinium myrtillus

Vaccinium vitis-idaea

Vigna sinensis

Vitis vinifera

Zea mays

Zea saccharata

Tropical rain-forest tree

Egg-plant

Potato

Badam tree or indian almond

Wheat var. Pelon IN EN

Reed mace

Blueberry

Cowberry

Cowpea

Grapevine

Maize

Sweet corn

6.4. SCIENTIFIC AND COMMON NAMES OF THE INVESTIGATED ANIMALS

Anadara granosa

Anodonta muttaulana lea

Asterias rubens

Cancer productus

Carassius auratus

Crangon vulgaris

Crassostrea gigas

Katelysia opima

Mya arenaria

Mytilus edulis

Tilapia mossambica

Bivalve mollusc

Freshwater mussel

Starfish

Crab

Goldfish

Shrimp

Japanese oyster

Indian clam

Soft-shell clam

Edible seawater mussel

Mouthbreeder (teleostean fish)

6.5. GLOSSARY

ACTIVITY: The amount of a radioactive substance expressed as the number of disintegrations taking place per unit of time (or as curies).

AZEOTROPIC: A solution of two or more liquids, the composition of which does not change upon distillation.

ANNEXES 99

BIOLOGICAL HALF TIME:

BIOMASS:

CHROMATID:

CHROMOSOME:

CHROMOSOMAL ABERRATIONS

COLCHICIN:

CURIE (Ci):

CYTOGENETICAL:

DNA:

ECOSYSTEM:

GLOVE BOX:

LABELLED MOLECULE: LEUCOCYTES:

LIQUID SCINTILLATION SPECTROMETER:

LYSIMETER:

METAPHASE:

NUCLIDE:

The period of time during which a given biological organism physiologically eliminates half the amount of a given substance that has been introduced into it.

A measure of the quantity of organisms.

One of the two strands which result from duplication of a chromosome during mitosis.

Thread-shaped body, consisting largely of DNA and proteins, numbers of which are in the nucleus of every animal or plant cell.

Anomalies of chromosomes.

Drug (an alkaloid) which prevents mitosis (process of cell division) proceeding beyond the metaphase.

Radioactivity unit equivalent to the amount of matter in which 3.7 X 1010 atoms disintegrate per second (1 Ci = 3.70 X 101 0Bq).

Term related to cytogenetics, science that links the study of the visible appearance of the chromosomes with genetics.

Deoxyribonucleic acid, an essential constituent of chromosomes.

A community of organisms, interacting with one another, plus the environment in which they live and with which they also interact, e.g. a pond, a forest.

A dust-tight box fitted with windows and gloves in which manipulations with hazardous alpha- or beta-active material may be carried out.

An isotope that is mixed with or fixed to the tracee in order to follow its translocation or identify its location. White blood cells.

A method of counting radiation, especially beta particles of low energy, by mixing the sample with an organic solvent containing an organic scintillator (i.e. an organic compound that transforms part of the energy dissipated into a flash of light). The light flashes emitted are registered by photomultiplier tubes.

Apparatus for measuring the percolation rate.

Stage of cell division characterized by arranging all the chromosomes on the equator of a spindle.

Any given atomic species characterized by the number of protons, Z, in the nucleus, the number of neutrons, N, in the nucleus, and the energy state of the nucleus (in the case of an isomer).

100

RADIONUCLIDE:

REM:

RESIDENCE HALF TIME:

RNA:

TRACEE:

TRITIATED COMPOUNDS

TRITIUM:

XYLEM:

ANNEXES

Radioactive nuclide, i.e. unstable (excited) nuclide.

The unit of 'dose equivalent' received by man and other mammals exposed to ionizing radiation. The dose in rem for any given type of radiation is obtained by multiplying the dose in rads by the quality factor (QF) for that particular type of radiation. (In special cases other modifying factors must be applied.)

The period of time during which a given compartment of an ecosystem eliminates half the amount of a given substance that has been introduced into it.

Ribonucleic acid, a molecule consisting of a large number of nucleotides attached together to form a long strand one nucleotide thick. Each nucleotide is formed from sugar (with five carbon atoms), phosphoric acid and a nitrogen-containing base (purine or pyrimidine).

The test object, element or compound that the investigator is endeavouring to trace.

Compounds containing tritium.

Radioactive isotope of hydrogen with mass 3 (3H).

Woody vascular tissue that conducts water and mineral salts taken in by roots throughout the plant, and provides it with mechanical support.

7. BIBLIOGRAPHY AND REFERENCES

Sub-section 7.1. General is purely a bibliography. The remaining sub-sections (7.2. — 7.6.) can be treated as a reading list since not all these numbered references are mentioned in the text.

7.1. GENERAL ANSPAUGH, L.R., KORANDA, J.J., ROBISON, W.L., Environmental Aspects of Natural Gas Stimulation Experiments with Nuclear Devices, 3rd National Symposium on Radioecology, Oak Ridge, 10 May 1971, California University, Lawrence Radiation Laboratory, Rep. UCRL-73429 (1971).

ANSPAUGH, L.R., PHELPS, P.L., KENNEDY, N.C., BOOTH, H.G., "Wind-driven redistribution of surface-deposited radioactivity", Environmental Behaviour of Radionuclides released in the Nuclear Industry (Proc. Symp. Aix-en-Provence, 1973), IAEA, Vienna (1973) 167.

ANSPAUGH, L.R., PHELPS, P.L., GUDIKSEN, C.L., HUCKABAY, G.W., In-Situ Measurement of Radionuclides in the Environment with a Ge(Li) Spectrometer, 2nd Conf. on Natural Radiation Environment, Houston, Texas, 7 Aug. 1972, California University, Lawrence Livermore Laboratory, Rep. UCRL-73904 (1973).

ARONOFF, S., CHOI, I.C., Specific activity of photosynthetic sugars in soybean leaves equi-librated with tritiated water, Arch. Biochem. Biophys. 102 (1963) 159.

AMERICAN ASSOCIATION OF CEREAL CHEMISTS, Approved Methods (AACC), Method 2621 1 (1962).

ASSOCIATION OF AGRICULTURAL CHEMISTS, Official Method of Analysis (AOAC), 10th Edn (HORWITZ, W., Ed.), Methods 13.006, 13.020, 13.028, 13.067 (1965).

BANTUGAN, G.A., BUSTAMANTE-JUAN, N., Behaviour of 3H in various ecosystems, 1st IAEA Research Co-ordination Meeting on the Environmental Behaviour of Tritium, Livermore, 1973.

BIGELEISEN, J., The validity of the use of tracers to follow chemical reactions, Science 110 (1949) 14.

BLACK, C.A., Soil-Plant Relationships, John Wiley, New York, London, Sydney (1968).

BOKHOVEN, C., THEEUWEN, H.H.J., Deuterium content of some natural organic substances, Proc. K. Ned. Akad. Wet., Ser. B 59 (1956) 78.

BONOTTO, S., KIRCHMANN, R., "Incorporation of 3H from tritiated water in the unicellular algae Acetabularia mediterrannea and Chlamydomonas reinhardi", 12th Int. Botanical Congress, Leningrad, Abstracts 1 (1975) 35.

BONOTTO, S., BOSSUS, A., NUYTS, G., KIRCHMANN, R., CANTILLON, G., DECLERCK, R., Etude de l'impact des decharges radioactives par le 3H, le I34Cs et le 60Co, Rapport d'avance-ment CEN/SCK, Ministere Sante Publique (1976) 45.

101

102 BIBLIOGRAPHY AND REFERENCES

BONOTTO, S., KIRCHMANN, R., FHLLUGA, B., NUYTS, G., BOSSUS, A., FAGNIART, E., Marine algae, a useful tool for research on the radioactive pollution of the sea, G. Bot. Ital. 111 6 ( 1 9 7 7 ) 351.

BROWN, K.W., Tritium in plants grown in Haines Pond, U.S. Environmental Protection Agency, National Environmental Research Center, Las Vegas, Nevada (unpublished, 1971).

BUSTAMANTE-JUAN, N., MANALASTAS, H.C., BANTUGAN, G.H., Behaviour of 3H in various ecosystems, 3rd IAEA Research Co-ordination Meeting on the Environmental Behaviour of Tritium, Helsinki, Finland, 1976.

CHARLES, P., REMY, J., VAN BRUWAENE, R., KIRCHMAN, R., Etude du DNA extrait d'organes d'animaux artificiellement contamines par du tritium sous forme organique, Arch. Int. Physiol. Biochim. 84 2 (1976).

CHARLES, P., Isolation and gradient analysis of DNA, presented at the 2nd IAEA Research Co-ordination Meeting on the Environmental Behaviour of Tritium, Mol, 15 — 18 Apr.1975.

CHARLES, P., "Isolation, preparation and characterization of deoxyribonucleic acids", Uptake of Informative Molecules by Living Cells, NATO Summer School, Mol, 1971 (LEDOUX, L., Ed.), North-Holland, Amsterdam (1972).

CLEGG, B., KORANDA, J., HADLEY, G., A System for Correlating Tritium Oxide Transport in Vegetation with Micrometeorological Variables" (Proc. Symp. San Francisco, 1971), California University, Lawrence Radiation Laboratory, Rep. UCRL-73373 (1971).

CLINE, J.F., Absorption and metabolism of tritium oxide and tritium gas by bean plants, Plant Physiol. 28 (1953) 717.

COHEN, L.K., KNEIP, T.J., "Environmental tritium studies at a PWR power plant", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 623.

COWSER, K.E., BOEGLY, W.J., JACOBS, D.G., 85Kr and Tritium in an Expanding World Nuclear Power Industry, Health Physics Division, Annual Progress Report for period ending 31 July 1966, Oak Ridge National Laboratory, Oak Ridge, USAEC Rep. ORNL-4007 (1966).

DELMAS, J., Transfert du tritium dans quelques arbres fruitiers cultives sous climat tempere de type mediterraneen, Radioecology progress report, Section de Radioecologie, C.E.N, de Cadarache (1977).

EISENBERG, D., KAUZMANN, W., The Structure and Properties of Water, OUP, New York and Oxford (1969).

ELWOOD, J.W., Ecological aspects of tritium behaviour in the environment, Nucl. Saf. 12 (1971) 326.

FRIEDMAN, A.S., WHITE, D., JOHNSTON, H.L., Critical constants, boiling points, triple points constants and vapor pressures of the six isotopic hydrogen molecules, based on a simple mass relationship, J. Chem. Phys. 19 1 (1951) 126.

GRIFFITHS, M.H., MALLINSON, A., A furncae for combustion of biological material contain-ing tritium and carbon-14 labeled compounds, Anal. Biochem. 22 (1968) 465.

HARRISON, F.L., KORANDA, J.J., TUCKER, J.S., "Tritiation of aquatic animals in an experimental marine pool", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 363.


HATCH, F.T., MAZRIMAS, J.A., KORANDA, J.J., MARTIN, J.R., Ecology and radiation exposure of kangaroo rats living in a tritiated environment, Radiat. Res. 44 1 (1970) 97.

HATCH, F.T., MAZRIMAS, J.A., Tritiation of animals from tritiated water, Radiat. Res. SO 2 (1972) 339.

HEYN, R.F., HERMANS, A.K., SCHILPEROORT, R.A., Rapid and efficient isolation of highly polymerized plant DNA, Plant Sci. Lett. 2 (1974) 73.

HOLLEMAN, A.F., WIBERG, E., Lehrbuch der Anorganischen Chemie, Walter De Gruyter, Berlin (.1971) 912.

IYENGAR, T.S., SADARANGANI, S.H., VAZE, P.K., SOMAN, S.D., Tritium transfer pathways in the aquatic plant Hydrilla verticellata, Curr. Sci. 45 24 (1976) 847.

IYENGAR, T.S., SADARANGANI, S.H., VAZE, P.K., SOMAN, S.D., Compartmental model for tritium persistence in the soil-plant system, Int. J. Appl. Radiat. Isot. 28 (1977) 481.

JACOBS, D.C., Sources of Tritium and its Behavior upon Release to the Environment, Critical Review Series, USAEC Rep. TID-24635 (1968).

JORDAN, C.F., KORANDA, J.J., KLINE, J.R., MARTIN, J.R., Tritium movement in a tropical ecosystem, Bioscience 20 (1970) 807.

KAHMA, K., MORSKY, P., HANN1NEN, V., KURONEN, P., SALONEN, L., MIETTINEN, J.K., Incorporation of tritium from tritiated water into DNA and free amino acids of pea plant, 3rd IAEA Research Co-ordination Meeting on the Environmental Behaviour of Tritium, Helsinki, Finland, 1976.

KIEFER, H., KONIG, L.A., WINTER, M., Study of propagation of atmospheric pollutants with aid of tritium, Kerntechnik 12 (1970) 212.

KIRCHMANN, R., LAFONTAINE, A., van den HOEK, J., KOCH, G., Transfert et repartition du tritium dans les constituants principaux du lait de vaches alimentees avec de l'eau contaminee, C.R. Seances Soc. Biol. Fil. 163 (1969) 1459.

KIRCHMANN, R., van den HOEK, J., LAFONTAINE, A., <« Transfert et incorporation du tritium dans les constituants de l'herbe et du lait, en conditions naturelless., 2nd Congr. IRPA, Brighton, 1970, Abstract 194.

KIRCHMANN, R., van den HOEK, J., KOCH, G., ADAM, V., "Studies on the food chain contamination by tritium", Working Group on Environmental Pollution, ESNA Meeting, Mol, 1971, Abstract 4.

KIRCHMANN, R., van den HOEK, J., KOCH, G., ADAM, V., "Studies on the food chain contamination by tritium", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 341.

KIRCHMANN, R., van den HOEK, J., LAFONTAINE, A., Transfert et incorporation du tritium dans les constituants de l'herbe et du lait en conditions naturelles, Health Phys. 21 (1971) 61.

KIRCHMANN, R., BONOTTO, S., "Penetration and incorporation of tritium in freshwater plants and in marine algae", 2nd Symp. on Acetabularia, Wilhelmshaven, 1972, Abstract: Protoplasma 75, 479.

KIRCHMANN, R., van den HOEK, J., Le tritium dans la biosphere et son transfert dans la chaine alimentaire, J. Beige Radiol. 55 2 (1972) 233,

1 0 4 BIBLIOGRAPHY AND REFERENCES

KIRCHMANN, R., van den HOEK, J., ADAM, V., "Source and transfer in a terrestrial food chain of tritium in the biosphere", ESNA meeting, Ispra, Italy, 1972, Abstracts, p. 100.

KIRCHMANN, R., BITTEL, R., FAGNIART, E., van GELDER-BONNIJNS, G., KOCH, G., "Transfer of tritium from radioactive waste to aquatic organisms, under natural conditions", Working Group on Environmental Pollution, ESNA meeting, Leuven, Belgium, 1973, Abstracts, p.31.

KIRCHMANN, R., van GELDER-BONNIJNS, G., CANTILLON, G., Surveillance radiologique des sites d'implantation des centrales nucleaires, Rapports d'avancement 1969—76, Groupe Mixte C.E.N./S.C.K. - Ministere Sante Publique.

KIRCHMANN, R., REMY, J., CHARLES, P., KOCH, G„ van den HOEK, J., <« Distribution et incorporation du tritium dans les organes de ruminants*-, Environmental Behaviour of Radio-nuclides released in the Nuclear Industry (Proc. Symp. Aix-en-Provence, 1973), IAEA, Vienna (1973) 385.

KIRCHMANN, R., Information on a recent meeting on a research programme on tritium co-ordinated by the IAEA: Results obtained in Belgium, Working Group on Environmental Pollution, ESNA meeting, Grenoble, 1974, Abstracts, p.23.

KIRCHMANN, R., Transfert dans le cycle biologique du tritium des rejets, J. Beige Radiol. 58 2 (1975) 115.

KIRCHMANN, R., PIRON, C., FAGNIART, E., MEURICE, M„ Etude de ^incorporation, chez l'algue Scenedesmus, du tritium organique des effluents, Contrat d'etude avec l'lnstitut d'hygiene et d'epidemiologie (M.S.P.), 6 4 2 / 2 1 0 - 0 / 1 9 7 5 .

KIRCHMANN, R., GRAUBY, A., DELMAS, J., ATHALYE, V., KOCH, G., "Evaluation of the dose to man in relation to the behavior of tritium from irrigation water in agricultural crops", 4th Congr. IRPA, Paris, 1977, 2, IRPA, Fontenay-aux-Roses, France (1977) 625.

KIRCHMANN, R., ATHALYE, V.V., FAGNIART, E„ "Studies on the uptake of tritium by several crops, under temperate climatic conditions", ESNA Meeting, Uppsala, Sweden, 1977, Abstracts.

KIRCHMANN, R., Le cheminement du tritium des rejets»>, Seminaire de Radioecologie, L'impact des installations nucleaires sur l'environnement, Cadarache, France, 31 Jan.— 4 Feb. 1977.

KLINE, J.R., STEWART, M.L., Tritium uptake and loss in grass vegetation which has been exposed to an atmospheric source of tritiated water, Health Phys. 26 (1974) 567.

KNOCHE, H.W., BELL, R.M., Tritium assay by combustion with a novel oxygen train and liquid scintillation techniques, Anal. Biochem. 12 (1965)49.

KONIG, L.A., WINTER, M., „tjber die Tritiumkontamination der Umwelt", Radioecology applied to the Protection of Man and his Environment (Proc. Symp. Rome, 1971), Commission of the European Communities, Rep. EUR 4800 (1972) 623.

KONIG, L.A., WINTER, M., Graphische Auswertung von Experimenten zur Bestimmung der atmospharischen Ausbreitung mit tritiiertem Wasserdampf als Tracer, Kernforschungszentrum Karlsruhe, Rep. KFK 1667 (1972).

KONIG, L.A., WINTER, M., "Investigation of the tritium level in the environment of the Karlsruhe Nuclear Research Center", 3rd Congr. IRPA, Washington, DC, 1973, Rep. CONF-730907-P1 (1974) 400.


KONIG, L.A., NESTER, K., SCHUTTELKOPF, H., WINTER, M., "Experiments conducted at the Karlsruhe Nuclear Research Center to determine diffusion in the atmosphere by means of various tracers", Physical Behaviour of Radioactive Contaminants in the Atmosphere (Proc. Symp. Vienna, 1973), IAEA, Vienna (1973) 67.

KONIG, L.A., WINTER, M., SCHULER, H., "Messung der Tritiumkontamination der Umwelt", Contribution to the 2nd Semi-annual Report for 1973 of the Nuclear Safety Project, Kernforschungszentrum Karlsruhe, Rep. KFK 1908 (1974).

KONIG, L.A., WINTER, M., Umweltbelastung durch Tritium, KFK Nachr.6 3 (1974) 33.

KONIG, L.A., WINTER, M., SCHULER, H., TACHLINSKI, W., Investigation of the Tritium Level in the Environment of the Karlsruhe Nuclear Research Center, Kernforschungszentrum Karlsruhe, Rep. KFK-Ext. 20/76-1 (1976).

KONIG, L.A., WINTER, M., TACHLINSKI, W., "Relationships existing between tritium releases from different sources and the contamination of air, water and plants", 4th Int. Congr. IRPA, Paris, 1977, IRPA, Fontenay-aux-Roses, France (1977).

KONIG, L.A., et al., WINTER, M., et al., Contributions to the annual reports of the Health Physics Division, Kernforschungszentrum Karlsruhe (KIEFER, H., KOELZER, W., Eds): 1969: KFK 1158(1970); 1970: KFK 1365 (1971); 1971: KFK 1565 (1972); 1972: KFK 1818 (1973); 1973: KFK 1973 (1974); 1974: KFK 2155 (1975); 1975: KFK 2266 (1976); 1976: KFK 2433 (1977).

KONIG, L.A., WINTER, M., SCHULER, H., Tritium in Niederschlagen, Oberflachen-, Grund-und Trinkwasser — Ergebnisse eines Messprogrammes mit Schwerpunkt in Raum Nordbaden in den Jahren 1971 bis 1974, Kernforschungszentrum Karlsruhe, Rep. KFK 2382 (Nov.1976).

KONIG, L.A., WINTER, M., SCHULER, H., Tritium in Niederschlagen, Oberflachen-, Grund-und Trinkwasser — Ergebnisse eines Messprogrammes mit Schwerpunkt im Raum Nordbaden in den Jahren 1975 und 1976, Kernforschungszentrum Karlsruhe, Rep. KFK 2520 (Nov. 1977).

KONIG, L.A., WINTER, M., Tritium in Water and Plants - Summary Report of Results obtained in a Measuring Program of Several Years Duration, Kernforschungszentrum Karlsruhe, Rep. KFK 2521 (Oct. 1977).

KORANDA, J.J., Residual Tritium at Sedan Crater (2nd. National Symposium on Radioecology, Ann Arbor, Michigan, 1967), California University, Lawrence Radiation Laboratory, Rep. UCRL-70292 (1967).

KORANDA, J.J., MARTIN, J.R., WIKKERINK, R.W., Leaching of Radionuclides at Sedan Crater, California University, Lawrence Radiation Laboratory Rep. UCRL-70630 (1968).

KORANDA, J.J., MARTIN, J.R., The Persistence of Radionuclides at Sites of Nuclear Detonations, California University, Lawrence Radiation Laboratory Rep. UCRL-71867 (1969).

KORANDA, J.J., PHELPS, P.L., ANSPAUGH, L.R., HOLLADAY, G„ Sampling and Analytical Systems for Measurement of Environmental Radioactivity, California University, Lawrence Radiation Laboratory Rep. UCRL-72987 (1971).

KORANDA, J.J., MARTIN, J.R., ANSPAUGH, L.R., The Significance of Tritium Releases to the Environment (Nuclear Science Symposium, San Francisco, 1971), California University, Lawrence Radiation Laboratory, Rep. UCRL-73546 (1971).

KORANDA, J.J., MARTIN, J.R., "The movement of tritium in ecological systems", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 430.


KRISHNAMOORTHY, T.M., SOMAN, S.D., Gel counting of 14C and 3H, Curr. Sci. 43 22 (1974) 703.

KRISHNAMOORTHY, T.M., SOMAN, S.D., Uptake of tritium by the marine bivalve, Katelysia Opima, Indian J. Mar. Sci. 4 (1975) 47.

KRISHNAMOORTHY, T.M., COGATE, S.S., SOMAN, S.D., Uptake of tritium from HTO exposure in fresh water fish, Tilapia Mossambica, Indian J. Exp. Biol. 15 7 (1977) 570.

KRISHNAMOORTHY, T.M., SOMAN, S.D., Incorporation of tritium from HTO exposure in the chemical constituents of algal cells, Indian J. Biochem. Biophys. (1977).

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(35) BOGEN, D.C., WELFORD, C.A., 'Fallout tritium' distribution in the environment, Health Phys. 30 (1976) 203.

(36) KORANDA, J.J., CLEGG, B.R., STUART, M., THOMPSON, S., Radiotracer Measure-ment of Transpiration in Tundra Vegetation, Barrow, Alaska, California University, Lawrence Livermore Laboratory, Rep. UCRL-78619 (1976).


7.4. PLANTS (1) KLINE, J.R., MARTIN, J.R., JORDAN, C.F., KORANDA, J.J., Transpiration in

Tropical Trees measured using Tritiated Water, California University, Lawrence Radiation Laboratory, Rep. UCRI^72036 (1970).

(2) GOGATE, S.S., KRISHNAMOORTHY, T.M., SOMAN, S.D., Indian J. Exp. Biol. 33 (1975) 264.

(3) MARTIN, J.R., JORDAN, C.F., KORANDA, J.J., KLINE, J.R., Radioecological Studies of Tritium Movement in a Tropical Rain Forest, California University, Lawrence Radiation Laboratory, Rep. UCRL-72256 (1970).

(4) GOGATE, S.S., KRISHNAMOORTHY, T.M., SOMAN, S.D., Indian J. Exp. Biol. 15 5 (1977)404.

(5) YUTHAMANOP, A., Progress Report from Thailand, Third IAEA Research Co-ordination Meeting on the Behaviour of Tritium in the Environment, Helsinki, Finland, 1976.

(6) INTERNATIONAL ATOMIC ENERGY AGENCY, The Behaviour of Tritium in the Environment, Preliminary consolidated report of the Co-ordinated Research programme, 1977.

(7) BUSTAMENTE-JUAN, N.B., MANALASTAS, H.C., BANTUGAN, G.H., Progress Report from the Philippines, 3rd IAEA Research Co-ordination Meeting on the Behaviour of Tritium in the Environment, Helsinki, Finland, 1976.

(8) KORANDA, J.J., MARTIN, J.R., "The movement of tritium in ecological systems", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973)430.

(9) McFARLANE, J.C., Tritium Accumulation in Lettuce fumigated with Elemental Tritium, U.S. Environmental Protection Agency, Rep. 600/3-76-006 (1976).

(10) SOMAN, S.D., IYENGAR, T.S., SADARANGANI, S.H., VAZE, P.K., "Tritium behaviour patterns in some plant systems in a tropical environment", Isotope Ratios as Pollutant Source and Behaviour Indicators (Proc. Symp. Vienna, 1974), IAEA, Vienna (1975) 195.

(11) KAHMA, K„ MORSKY, P., HANNINEN, V., KURONEN, P., SALONEN, L„ MIETTINEN, J.K., Progress Report from Finland, 3rd IAEA Research Co-ordination Meeting on the Behaviour of Tritium in the Environment, Helsinki, Finland, 1976.

(12) DELMAS, J., GRAUBY, A., KIRCHMANN, R„ BLONDEL, L., BENARD, P., FADY, C., Progress Report from France, 3rd IAEA Research Co-ordination Meeting on the Behaviour of Tritium in the Environment, Helsinki, Finland, 1976.

(13) ARCHUNDIA, C., ORTIZ MAGANA, J.R., Progress Report from Mexico, 3rd IAEA Research Co-ordination Meeting on the Behaviour of Tritium in the Environment, Helsinki, Finland, 1976.

(14) KIRCHMANN, R., Progress Report from Belgium, 3rd IAEA Research Co-ordination Meeting on the Behaviour of Tritium in the Environment, Helsinki, Finland, 1976.

(15) TAYLOR, G.W., HARVEY, E.N., Respiration of yeast in water containing deuterium oxide, Proc. Soc. Exp. Biol. Med. 3 1 (1937) 954.

(16) CRUMLEY, A.H., MEYER, S.L., Effects of deuterium oxide on germination, J. Tenn. Acad. Sci. 25 3 (1950).

(17) MOSES, V., HOLM-HANSEN, O., Response of Chlorella to a deuterium environment, Biochim. Biophys. Acta. 28 (1958) 62.

(18) WEINBERGER, D., PORTER, J.W., Metabolism of hydrogen isotopes by rapidly growing Chlorella pyrenoidosa cells, Arch. Biochem. Biophys. 5 0 (1954) 160.


(19) ^BENNETT, E.L., CALVIN, M„ HOLM-HANSEN, O., HUGHES, A.M., LONBERG-HOLM, K.K., MOSES, V., TOLBERT, B.M., Effect of Deuterium Oxide (Heavy Water) on Biological Systems, California University, Berkeley Radiation Labora-tory, Rep. UCRL 3981 (1958).

(20) BLAKE, M.I., CRANE, F.A., UPHOUS, R.H., KATZ, J.J., Effect of heavy water on the germination of a number of species of seeds, Planta 78 (1968) 35.

(21) CRANE, F.A., BLAKE, M.I., UPHOUS, R.A., KATZ, J.J., The effects of deuterium replacement on seed development: Influence on excised embryos, J. Bot. 47 (1969) 1465.

(22) JONES, W.M., Vapor pressures of tritium oxide and deuterium oxide: Interpretation of the isotope effect, J. Chem. Phys. 48 (1968) 207.

(23) SPAULDING, J.F., LANGHAM, W„ ANDERSON, E.C., The relative biological effective-ness of tritium with the broad bean root (Vicia faba) as a test system, Radiat. Res. 4 (1956) 221.

(24) CHORNEY, W„ SCULLY, N.J., DUTTON, J.J., Radiation effects of carbon-14 and tritium on growth of soybeans, Radiat. Bot. 5 (1965) 257.

(25) McFARLANE, J.C., unpublished data, 1975. (26) VIG, B.K., McFARLANE, J.C., Somatic crossing over in Glycine Max L. (Merrill):

Sensitivity to and saturation of the system at low levels of tritium emitted beta-radiation, Theor. Appl. Genet. 46 (1975) 331.

(27) WOODWARD, H.Q., The Biological Effects of Tritium, Health and Safety Laboratory, USAEC New York Operations Office, Rep. HASL-229, New York (1970).

(28) FUNK, F., PERSON, S., Cytosine to thymine transitions from decay of cytosine-5 3H in bacteriophage, S13, Science 166 (1969) 1629.

7.5. TERRESTRIAL ANIMALS (1) RICHMOND, C.R., LANGHAM, W.H., TRUJILLO, T.T., Comparative metabolism of

tritiated water by mammals, J. Cell. Comp. Physiol. 59 (1962) 45. (2) CUNNINGHAM, H.M., Use of tritiated water to determine the effect of water restriction

on the insensible water loss of pigs, J. Anim. Sci. 27 (1968) 412. (3) LONGHURST, W.M., BAKER, N.F., CONOLLY, G.E., FISK, R.A., Total body water

and water turnover in sheep and deer, Am. J. Vet. Res. 31 (1970) 673. (4) SADARANGANI, S.H., SAHASRUBUDHE, S.G., SOMAN, S.D., "Tritium excretion in

man under tropical conditions", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds.), Messenger Graphics, Las Vegas (1973) 327.

(5) BLACK, A.L., BAKER, N.F., BARTLEY, J.C., CHAPMAN, T.E., PHILLIPS, R.W., Water turnover in cattle, Science 144 (1964) 876.

(6) YOUSEF, M.K., "Tritiated water turnover rate in desert mammals", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 333.

(7) MARTIN, J.R., KORANDA, J.J., Biological half-life studies of tritium in chronically exposed kangaroo rats, Radiat. Res. 5 0 ( 1 9 7 2 ) 4 2 6 .

(8) POTTER, G.D., VATTUONE, G.M., McINTYRE, D.R., Metabolism of tritiated water in the dairy cow, Health Phys. 22 (1971) 405.

(9) SNYDER, W.S., FISH, B.R., BERNARD, S.R., FORD, M.R., MUIR, J.R., Urinary excretion of tritium following exposure of man to HTO - A two exponential model, Phys. Med. Biol. 13 (1968) 547.

1 1 6 BIBLIOGRAPHY AND REFERENCES

(10) PINSON, E.A., LANGHAM, W.H., Physiology and toxicology of tritium in man, Appl. Physiol. 1 0 ( 1 9 5 7 ) 108.

(11) RADWAN, I., PIETRZAK-FLIS, Z., JAWOROWSKI, Z., Tritium retention in rat after administration of various doses of tritiated water, Curr. Top. Radiat. Res. 12 (1977) 278.

(12) HATCH, F.T., MAZRIMAN, J.A., Tritiation of animals from tritiated water, Radiat. Res. 50(1972) 339.

(13) KIRCHMANN, R., van den HOEK, J., unpublished results. (14) KIRCHMANN, R., CHARLES, P., van BRUWAENE, R., REMY, J., KOCH, G.,

van den HOEK, J., Distribution of tritium in the different organs of calves and pigs after ingestion of various tritiated feeds, Curr. Top. Radiat. Res. 12 (1977) 291.

(15) THOMPSON, R.C., BALLOU, J.E., The predominantly nondynamic states of body constituents in the rat, J. Biol. Chem. 223 (1956) 795.

(16) KISTNER, G.N., "Tritium excretion via cow's milk after continuous intake of tritiated water", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 349.

7.6. MODELLING (1) DIXON, R.M., PETERSON, A.E., Water infiltration control: a channel system concept,

Soil Sci. Soc. Am., Proc. 35 6 (1971) 968. (2) JORDAN, C.F., KLINE, J.R., SASSCER, D.S., "Tritium movement in an old-field

ecosystem determined experimentally", Radionuclides in Ecosystems (Proc. Third National Symposium on Radioecology, NELSON, D.J., Ed.), U.S. Atomic Energy Commission, CONF-710501-P1 (1971) 199.

(3) SASSCER, D.S., JORDAN, C.F., KLINE, J., "Dynamic model of water movement in soil under various climatological conditions", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 485.

(4) SASSCER, D.S., JORDAN, C.F., KLINE, J.R., "Mathematical model of tritiated and stable water movement in an old-field ecosystem", Radionuclides in Ecosystems (Proc. Third National Symposium on Radioecology, NELSON, D.J., Ed.), U.S. Atomic Energy Commission, CONF-710501-P1 (1971) 915.

(5) JORDAN, C.F., STEWART, M.L., KLINE, J.R., Tritium movement in soils: The importance of exchange and high initial dispersion, Health Phys. 27 (1974) 37.

(6) STEWART, G.L., "Fractionation of tritium and deuterium in soil water", Isotope Tech-niques in the Hydrologie Cycle (STOUT, G.E., Ed.), Geophysical Monographs No. 11, The U.S. Geophysical Union, Washington, DC (1967) 159.

(7) STEWART, G.L., "The behaviour of tritium in the soil", Tritium (MOGHISSI, A. A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 462.

(8) RABINOWITZ, D.D., HOLMES, C.R., GROSS, G.W., "Forced exchange of tritiated water with clay", Tritium (MOGHISSI, A.A., CARTER, M.W., Eds), Messenger Graphics, Las Vegas (1973) 471.

(9) HALEVY, E., The exchangeability of hydroxyl groups in kaolinite, Geochim. Cosmochim. Acta. 28 (1964) 1139.

(10) COREY, J.C., HORTON, J.H., Movement of water tagged with 2H, 3H and 1 8 0 through acidic kaolinitic soil, Soil Sci. Soc. Am., Proc. 32 (1968) 471.

(11) COLEMAN, N.T., McAULIFFE, C., "H-ion catalysis by clays", Proc. 3rd National Conference on Clays and Clay Minerals (MILLIGAN, W.D., Ed.), National Academy of Sciences - National Research Council, Washington, DC, Publication 395 (1955) 282.


(12) STEWART, G.N., Researches on the circulation time and on the influences which affect it, J. Physiol. (London) 22 (1897) 159.

(13) HAMILTON, W.F., The physiology of the cardiac output, Circulation 8 (1953) 527. (14) BERGNER, P.-E.E., Tracer dynamics: I. A tentative approach and definition of funda-

mental concepts, J. Theor. Biol. 2 (1961) 120. (15) BERGNER, P.-E.E., Tracer dynamics and determination of pool sizes and turnover factors

in metabolic systems, J. Theor. Biol. 6 (1964) 137. (16) BERGNER, P.-E.E., Exchangeable mass: Determination without assumption of isotopic

equilibrium, Science 150 (1965) 1048. (17) BERGNER, P.-E.E., Tracer theory: A review, Isot. Radiat. Technol. 3 (1966) 245. (18) ZIERLER, K.L., "Basic aspects of kinetic theory as applied to tracer distribution studies",

Dynamic Clinical Studies with Radioisotopes (Proc. Symp. Oak Ridge Inst. Nuclear Studies), Oak Ridge (1964) 55.

(19) LJUNGGREN, K., A review of the use of radioisotope tracers for evaluating parameters pertaining to the flow of materials in plant and natural systems, Isot. Radiat. Technol. 5 1 (1967) 3.

(20) ORR, J.S., GILLESPIE, F.C., Occupancy principle for radioactive tracers in steady state biological systems, Science 162(1968) 138.

(21) SARMA, T.P., KRISHNAMOORTHY, T.M., SOMAN, S.D., Behaviour of tritium in air-water interactions, Indian J. Pure Appl. Phys. 14 (1976) 982.

(22) SLATYER, R.O., Plant Water Relationships, Academic Press, London and New York (1967).

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Tritium in Some Typical Ecosystems

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