NORDIC RADIOECOLOGY THE TRANSFER OF RADIONUCLIDES THROUGH NORDIC ECOSYSTEMS TO MAN potx

NORDIC RADIOECOLOGY
THE TRANSFER
OF
RADIONUCLIDES THROUGH
NORDIC ECOSYSTEMS TO MAN
This Page Intentionally Left Blank
Studies in Environmental Science
62
NORDIC
RADIOECOLOGY
THE TRANSFER
OF
RADIONUCLIDES
THROUGH NORDIC ECOSYSTEMS
TO MAN
Edited
by
H.
Dahlgaard
Ris~ National Laboratory
Roskilde, Denmark
ELSEVIER
Amsterdam
-
Lausanne
-
New
York
-
Oxford

-
Shannon
-
Tokyo
1994
ELSEVIER SCIENCE
B.V
Sara Burgerhartstraat
25
P.O.
Box
21 1,1000
AE Amsterdam,The Netherlands
ISBN
1
0-444-8 16 17-8
0
1994
Elsevier Science
B.V.
All rights reserved.
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This book is printed on acid-free paper.
Printed in The Netherlands
V
PREFACE
The present book is the final milestone

in
the radioecology programme, RAD, carried out from
1990 to 1993 under the Nordic Committee for Nuclear Safety Research, NKS. This work was done
in
parallel to three other NKS programmes: Reactor safety (SIK), Waste and decommissioning
(KAN), and Emergency preparedness (BER). The NKS was established
in
1966 and was financed
by the Nordic Council of Ministers from 1977 to 1989. It is now a joint Nordic committee
financed by the Danish Emergency Management Agency, the Finnish Ministry of Trade and
Industry, Iceland's National Institute of Radiation Protection, the Norwegian Radiation Protection
Authority, and the Swedish Nuclear Power Inspectorate. The NKS is further co-sponsored by a
number of Finnish and Swedish companies working
in
the field of civil nuclear energy and
protection of the population.
The preparation of this book involved much painstaking effort by the authors, the participants
in the working groups and the four project leaders, Manuela Notter, Per Strand, Aino Rantavaara
and Elis
Holm.
I
would like here
to
express
my
gratitude for their contribution. The guidance and
inspiration given by the RAD reference group is furthermore acknowledged. Finally,
it
should be
mentioned that there would have been no Nordic collaboration on Nuclear Safety without the

energetic, persistent, diplomatic and occasionally maddening efforts of our travelling
"ambassador", Franz Marcus, executive secretary of the NKS from 1976
to
1994.
Henning Dahlgaard
Co-ordinator of the RAD programme
This Page Intentionally Left Blank
vii
CONTENTS
PREFACE
CONTRIBUTORS AND PARTICIPANTS
V
XI
Chapter
1
NORDIC RADIOECOLOGY
1990 -1993
1
1.1
The aims and justification of Nordic radioecology.
H.
Dahlgaard
3
1.2
General summary and conclusions.
H.
Dahlgaard,
M.
Notter,
J.

Brittain,
P. Strand, A. Rantavaara and
E.
Holm
7
Chapter
2
AQUATIC ECOSYSTEMS
21
2.1
Introduction to aquatic ecosystems.
M.
Notter, J. Brittain and
U.
Bergstrom
23
2.2
The characterization
of
radiocaesium transport and retention in Nordic
lakes. H.E. Bjernstad, J.E. Brittain,
R.
SaxBn
and B. Sundblad
29
2.3
The distribution and characterization of 137Cs
in
lake sediments.
A. Broberg

45

Vlll
2.4
Transport of 137Cs
in
large Finnish drainage basins.
R.
Saxtn
2.5
The role of lake-specific abiotic and biotic factors for the transfer of
radiocaesium fallout to fish.
T. Anderson and
M.
Meili
2.6
Models for predicting radiocaesium levels in lake water and fish.
U.
Bergstrom, B. Sundblad and
S.
Nordlinder
2.7
Radiocaesium
in
algae from Nordic coastal waters.
L.
Carlson and P. Snoeijs
2.8
Polonium-210 and radiocaesium
in

muscle tissue of fish from
different Nordic marine areas.
E.
Holm
2.9
Radiocaesium as ecological tracer
in
aquatic systems
-
a review.
M.
Meili
Chapter
3
AGRICULTURAL ECOSYSTEMS
3.1
Introduction to radioecology of the agricultural ecosystem.
P.
Strand
3.2
Direct contamination
-
seasonality.
A.
Aarkrog
3.3
Influence of physico-chemical forms
on
transfer.
D.H. Oughton and

B.
Salbu
3.4
Contamination of annual crops.
M.
Strandberg
3.5
Transfer of 137Cs to cows’ milk
in
the Nordic countries.
H.S. Hansen and LAndersson
3.6
Radiocaesium transfer
to
grazing sheep
in
Nordic environments.
K.
Hove,
H.
Lijnsjo et al.
63
79
93
105
119
127
141
143
149

1
65
185
197
211
ix
3.7
Dynamic model
for
the transfer
of
137Cs through the
soil-grass-lamb foodchain. S.P. Nielsen
3.8
Studies
on
countermeasures after radioactive depositions
in
Nordic agriculture.
K.
RosCn
229
239
Chapter
4
FOREST AND ALPINE ECOSYSTEMS
26
1
4.1
Introduction to terrestrial seminatural ecosystems. A. Rantavaara

263
4.2
The transfer of radiocaesium from soil to plants and fungi
in
seminatural ecosystems. R.A. Olsen
265
4.3
Radiocaesium
in
game animals
in
the Nordic countries.
K.J.
Johanson
287
4.4
Pathways
of
fallout radiocaesium via reindeer to man.
E.
Gaare and
H.
Staaland
303
4.5
The distribution of radioactive caesium
in
boreal forest ecosystems.
R.
Bergman

335
Chapter
5
METHODOLOGY, QUALITY ASSURANCE AND
DOSES
5.1
Introduction to intercalibration
/
analytical quality control
and doses.
E.
Holm
5.2
Intercomparison of large stationary air samplers.
I.
Vintersved
381
383
3 85
X
5.3
Intercalibration of whole-body counting systems.
T. Rahola,
R.
Falk and
M.
Tillander
5.4
Intercalibration of gamma-spectrometric equipment. E. Holm
5.5

Doses from the Chernobyl accident to the Nordic populations
via diet intake. A. Aarkrog
5.6
Internal radiation doses to the Nordic population based on
whole-body counting.
M.
Suomela and T. Rahola
DEFINITIONS, TERMS AND UNITS
INDEX
SPECIES INDEX
407
425
433
457
473
477
48
1
xi
CONTRIBUTORS
AND
PARTICIPANTS
Hannele
Aaltonen,
STUK, P.O.Box
14,
FIN
00881
Helsinki
Asker

Aarkrog,
ECO-Riss, Postboks
49,
DK
4000
Roskilde
Magne
Alpsten,
Institut for Radiofysik, Sahlgrenska Sjukhuset,
S
41345
Goteborg
Inger
Andersson,
Lantbruksuniversitetet, Box
59,
S
23053
Alnarp
Tord
Andersson,
Naturgeografisk avd., Umel Universitet,
S
90187
Umel
Ronny
Bergmann,
FOA-4,
S
90182

Umel
Ulla
Bergstrom,
Studsvik Eco
&
Safety,
S
61182
Nykoping
Torolf
Bertelsen,
Statens Strllevern, Postboks
55,
N
1345
0sterh
Helge E.
Bjernstad,
Agricultural University of Norway,
N
1432
AS-NLH
Inggard
Blakar,
Agricultural University
of
Norway,
N
1432
AS-NLH

John
Brittain,
Oslo
Universitet,
Sars
Gate
1,
N
0562
Oslo
Anders
Broberg,
Uppsala Universitet, Box
557,
S
75122
Uppsala
Lena
Carbon,
Avd. for Marinekologi, Box
124,
S
22100
Lund
Gordon
Christensen,
IFE, Postboks
40,
N
2007

Kjeller
Olof
Eriksson,
Lantbruksuniversitetet, Box
703 1,
S
75007
Uppsala
Ake
Eriksson,
Lantbruksuniversitetet, Box
7031,
S
75007
Uppsala
Sverker
Evans,
Statens Naturvbdsverk,
Box
1302,
S
17125
Solna
Rolf
Falk,
Swedish Radiation Protection Institute, Box
60204,
S
10401
Stockholm

Torbjorn
Forseth,
Institut for Naturforskning, Tungasletta
2,
N
7004
Trondheim
Lars
Foyen,
Havforskningsinstituttet,
Box
1870,
N
5024
Bergen
Torstein
Garmo,
Agricultural University of Norway,
N
1432
AS-NLH
Eldar
Gaare,
Norwegian Institute for Nature Research, Tungasletta
2,
N
7005
Trondheim
Eva
Hllkansson,

Institut for Radiofysik, Sahlgrenska Sjukhuset,
S
41345
Goteborg
Lars
EUkansson,
Uppsala Universitet, Viistra Agatan
24,
S
75220
Uppsala
Hanne
S.
Hansen,
Agricultural University of Norway,
N
1432
AS-NLH
Lars
Egil
Haugen,
Agricultural University of Norway,
N
1432
AS-NLH
Knut
Hove,
Agricultural University of Norway,
N
1432

AS-NLH
Erkki
nus,
STUK,
P.O.Box
14,
FIN
00881
Helsinki
Kki
Indridason,
Geislavarnir rikisins, Laugavegur
118d,
Is
150
Reykjavik
xii
Tim0
Jaakkola,
Radiokemiska institutionen, Pb 5, FIN 00014 Helsingfors Universitet
Hans Pauli
Joensen,
Academia Faroensis, Noatun, FR
100
Torshavn
Karl J.
Johanson,
Lantbruksuniversitetet, Box 7031,
S
75007

Uppsala
Bernt
Jones,
Lantbruksuniversitetet, Box 7038,
S
75007
Uppsala
Pekka
Kansanen,
Helsingin kaupungin ymp., Helsinginkatv. 24, FIN
00530
Helsinki
Riitta
Korhonen,
VlT/YDI, Pb 208, FIN 02151 Espoo
Vappu
Kossila,
Lantbrukets forskningscentral, FIN
3
1600 Jokioinen
Andrew
Liken,
Agricultural University of Norway, N 1432 AS-NLH
Hans
Liinsjo,
Lantbruksuniversitetet, Box 7031,
S
75007
Uppsala
Sigurdur

Magnusson,
Geislavarnir rikisins, Laugavegur 1
18d,
Is
150
Reykjavik
Soren
Mattsson,
Inst. for Radiofysik, Malmo Almanna Sjukhus,
S
21401Malmo
Marcus
Meili,
Uppsala Universitet, Box
557,
S
75122 Uppsala
Georg
NeumaM,
Lantbruksuniversitetet, Box 7031,
S
75007
Uppsala
Sven P.
Nielsen,
ECO-Riss, Postboks 49, DK 4000 Roskilde
Sture
Nordlinder,
Studsvik Eco
&

Safety,
S
61 182 Nykoping
Tuire
Nygren,
Vilt- och
Fiskeriforskningsinstitutet,
Tutkimuslaitos, FIN 82950 Kuikkalampi
Elisabet D.
Olafsdijttir,
Geislavarnir rikisins, Laugavegur 118d,
Is
150
Reykjavik
Rolf
A.
Olsen,
Agricultural University of Norway, N 1432 AS-NLH
Deborah H.
Oughton,
Agricultural University of Norway, N 1432 AS-NLH
Olli
Paakkola,
Torpantie 1 B, FIN 01650 Vanda
Arja
Paasikallio,
Lantbrukets forskningscentral, FIN 3 1600 Jokioinen
Sigurdur
E.
Piilsson,

Geislavarnir rikisins, Laugavegur 118d,
Is
150 Reykjavik
Tua
Rahola,
STUK, P.O.Box 14, FIN 00881 Helsinki
Hannu
Raitio,
Skogforskningsinstitutet,
FIN
39700
Parkano
Kristina
Rissanen,
STUK, Louhikkotie
28,
FIN
96500
Rovaniemi
Klas
Rosbn,
Lantbruksuniversitetet, Box 7031,
S
75007
Uppsala
Brit
Salbu,
Agricultural University of Norway,
N
1432 AS-NLH

Chr.
Samuekson,
Institutionen f. Radiofysik, Lasarettet,
S
22185 Lund
Ritva
Saxbn,
STUK, P.O.Box 14, FIN 00881 Helsinki
Tone
Selnaes,
IFE, Postboks 40,
N
2007 Kjeller
Pauli
Snoeijs,
Uppsala Universitet, Box 559,
S
75122 Uppsala
Riitta
Sormunen-Christian,
Lantbrukets forskningscentral, FIN
3
1600 Jokioinen
Hans
Staaland,
Agricultural University of Norway, N 1432 AS-NLH
Eiliv
Steinnes,
Universitetet, AVH, N
7055

Dragsvoll
Morten
Strandberg,
ECO-Riss, Postboks 49,
DK
4000 Roskilde
xiii
Bjorn
Sundblad,
Studsvik
Eco
&
Safety,
S
61182
Nykoping
Matti
Suomela,
STUK, P.O.Box
14,
FIN
00881
Helsinki
J6hann
Thorsson,
Agricultural Research Institute,
Is
112
Reykjavik
Michael

Tillander,
Helsinki Universitet, Radiokemiska inst., FIN
00014
Helsinki
Ole
Ugedal,
Finmark Distrikth0yskole, Follumsvei, N
9500
Alta
Finn
Ugletveit,
Statens Strilevern, Postboks
55,
N
1345
0sterh
Trygvi
Vestergaard,
Academia Faeroensis, Noatun, FR
100
Torshavn
Ingemar
Vintersved,
Forsvarets Forskningsanstalt,
S
17290
Sundbyberg
PROJECT LEADERS
Elis
Holm,

Institutionen f. Radiofysik, Lasarettet,
S
22185
Lund
Manuela
Notter,
Statens NaturvArdsverk, Box
1302,
S
17125
Solna
Per
Strand,
Statens Strhlevern, Postboks
55,
N
1345
0steris
Aino
Rantavaara,
STUK, P.O.Box
14,
FIN
00881
Helsinki
REFERENCE
GROUP
Asker
Aarkrog,
Rise National Laboratory, Postboks

49,
DK
4000
Roskilde
Henning
Dahlgaard,
Riss National Laboratory, Postboks
49,
DK
4000
Roskilde (Co-ordinator)
Sigurdur
Magnusson,
Geislavarnir rikisins, Laugavegur 118d.
Is
150
Reykjavik
Franz
Marcus,
NKS, Postboks
49,
DK
4000
Roskilde
Judith
Melin,
SSI,
Box
60204,
S

10401
Stockholm
Eiiiv
Steinnes,
Universitetet, AVH, N
7055
Dragsvoll
Matti
Suomela,
STUK, P.O.Box
14,
FIN
00881
Helsinki
Seppo
Vuori,
VTT/YDI, Pb
208,
FIN
02151
Espoo
Erik-Anders
Westerlund,
Statens StrAlevern, Postboks
55,
N
1345
0sterh (Chairman)
CO-ORDINATOR
Henning

Dahlgaard,
Rise National Laboratory, Postboks
49,
DK
4000
Roskilde
This Page Intentionally Left Blank
Chapter
1
NORDIC
RADIOECOLOGY
1990
-
1993
This Page Intentionally Left Blank
3
1.1.
THE AIMS
AND
JUSTIFICATION
OF
NORDIC RADIOECOLOGY
HEN"G
DAHLGAARD
Risar National Laboratory, DK-4000 Roskilde, Denmark.
SUMMARY
A description is given of the goals and background of the RAD programme described
in
this book.
The overall scientific aim of the Nordic Radioecology programme was

to
perform a quantitative,
comparative study of the pathways of Chernobyl-derived radiocaesium,
in
particular, through
different Nordic ecosystems. Furthermore, the programme was to help a new generation of
radioecologists become acquainted with different Nordic ecosystems and to foster Nordic contacts.
The relevance of a radioecology programme for nuclear accident preparedness is furthermore
stressed.
BACKGROUND
The word RADIOECOLOGY came into being
in
the 1950's when it became evident that man-made
radionuclides produced
in
atmospheric nuclear weapons tests had been spread globally and were
transferred through various ecosystems
to
man. From the very beginning the scientific study of
radioecology was developed
by
scientists with an interest
in
ecology and genetics. However,
physicists, analytical chemists and engineers played an essential role because accurate
measurements of the low levels
of
the relevant radionuclides
-
e.g.

%k,
'37Cs
and
239Pu
-
found
in
the environment, required the elaborate analytical procedures and advanced electronic equipment
that were gradually developed during the 1960's
-
the "Golden Age" of radioecology. At most
institutions radioecology became a branch of
health
physics ultimately aiming at studying and
reducing the radiation dose to man. Attempts were made at several institutions to incorporate the
field
in
general ecology and to utilize the radionuclides as global-scale tracers for, e.g., studies of
atmospheric pollutant transport and trace element turnover. However interest
in
radioecology
dwindled with the declining activity from atmospheric fallout, and by the mid-1980's work
in
radioecology had been reduced to a minimum,
or
was even non-existent
in
several countries.
Furthermore the integrity of radioecologists and health physicists had been challenged by
"environmentalist" groups fighting the peaceful utilization of nuclear energy

on
a non-scientific
basis. Several institutions thus reduced funding to radioecology to serve political ends.
When the accident at the Chernobyl nuclear power station happened in April 1986
4
radioecology was reinvented throughout Europe and surviving centres of study were given an
economic boost. At several places ecologists of different backgrounds introduced new and fruitful
concepts, using the Chernobyl radiocaesium for more than just radiation protection studies.
The Nordic countries, Denmark, Finland, Iceland, Norway and Sweden, have a long, historic
tradition of cultural and scientific collaboration. This has also applied
to
radioecology, where the
Nordic Committee for Nuclear Safety Research
(NKS),
financed by the Nordic Council of
Ministers, included this subject in their programmes from 1977
to
1985.
At
the beginning of 1986
-
a few months before the Chernobyl accident
-
general radioecology was removed
from
this
collaboration', and from 1990 the NKS financing was transferred from the Nordic Council of
Ministers
to
the national authorities responsible for nuclear safety and radiation protection in the

different countries. The Nordic radioecology programme RAD, which is the subject of the present
book, was run under the auspices
of
the new NKS from 1990 to 1993. Via the NKS, the RAD
programme has had funding of around 6 million Danish kroner
(-
1 million
US
$).
As
the contents
of the present book will show, this is only a minor part of the total costs of the work described
here. However, without the catalytic support provided by the NKS much
of
the present work
would not have taken place, and efforts in different Nordic countries would not have been co-
ordinated.
Plans for the Nordic Radioecology programme 1990-1993 were described in the Scandinavian
languages
in
a publication issued by the Nordic Council of Ministers (NKS, 1989).
THE
NORDIC RADIOECOLOGY PROGRAMME
The RAD programme consists of four projects. As the largest doses to man immediately after the
Chernobyl accident were derived from the consumption of terrestrial products and freshwater fish,
the programme included 2 projects on terrestrial radioecology: RAD-3, Agricultural ecosystems
(project leader: Per Strand) and RAD-4, Forest and alpine ecosystems (project leader: Aino
Rantavaara), and
one
on

aquatic radioecology: RAD-2, Aquatic ecosystems (project leader:
Manuela Notter) that mainly dealt with Nordic lakes. Finally, RAD-1 included training,
methodology, quality assurance and doses to the Nordic population (project leader: Elis Holm).
Results from the four projects are presented
in
detail
in
chapters
2-5,
and are summed up
in
the
following chapter 1.2.
~
I:
The AKTU program 1985
-
1989 did, however, include environmental radioactivity after
the Chernobyl accident (Tveten, editor).
5
AIMS
AND
JUSTIFICATION
After
the Chernobyl accident it became clear that the transfer of radionuclides via food to man
could result in significant internal radiation doses
to
the Nordic population after nuclear accidents.
In
the long term the most significant internal doses from Chernobyl were expected to be related

to the contamination of specially sensitive Nordic environments leading
to
a high transfer of
radiocaesium to man. It was considered important for the authorities to have access to up-to-date
knowledge of the spreading and turnover
of
radionuclides in different Nordic ecological systems
in
order
to
be able to decide on the relevant countermeasures. Furthermore, knowledge of the
contamination levels of agricultural products was necessary to assure exports and avoid
unnecessary
loss
of
resources.
There is an immense variation within the Nordic countries not only in the distribution of the
Chernobyl deposition, but also
in
the transfer of radiocaesium to man. The contamination of a
highly productive agricultural area is expected to give relatively small individual doses to a large
population during a short period, whereas the contamination of the lichen carpets utilized
as
winter-
grazing for reindeer,
or
of the abundant oligotrophic lakes, will give a larger individual dose to
a small population for many years.
The overall scientific aim of the Nordic Radioecology programme was
to

perform a
quantitative comparative study of the pathways of selected radionuclides through different Nordic
ecosystems. Moreover the programme aims at helping a new generation of radioecologists
to
become acquainted with different Nordic ecosystems and to foster Nordic contacts. The
RAD
programme has aimed at obtaining the widest possible coverage, i.e. the inclusion of
as
many
Nordic radioecological centres
as
possible. This is not cost-effective with respect
to
research
results, but it does promote Nordic radioecological contacts.
As
a consequence, the programme
is to a large extent based
on
nationally-funded programmes.
A
general goal for the entire programme
-
and a justification for the funding of the
programme
by
the nuclear safety authorities
-
is
its

benefits
in
respect
of
preparedness for nuclear
accidents. On first thoughts this goal may seem remote from a scientific field programme on the
cycling
of
caesium
in
the environment. However, one benefit
of
keeping radioecological centres
alive is that the necessary measuring equipment is ready for use, and that competent staff are
available
to
take suitable samples and carry out reliable radionuclide analyses
the
very day an
accident happens.
In
addition, knowledge of the pathways of radionuclides through ecosystems to
man will be available.
A
nuclear preparedness plan without working scientific projects is like an
airforce without trained fighter pilots.
Maybe
the
most
important justification

of
such programmes
is
not the production
of
final
reports, but rather the less definable benefits such as inspiration and collaboration based on the
6
close personal relations among individual scientists from different Nordic countries and institutions
having common interests.
A
further aspect of the personal contact between Nordic radioecologists
and radiation protection officials is that it will facilitate information exchange between the different
countries in any future nuclear emergency.
REFERENCES
NKS
(1989).
Plan for Nordisk Kjernesikkerhetsprogram
1990-1993.
Nordisk Md, Nordisk
Ministerriid, NU
19895
(in the Scandinavian languages).
Tveten,
U.
(editor). Environmental consequences
of
releases
from
nuclear accidents. Final report

of the NKA project
AKTU-200.
IFE,
P.O.
Box
40,
N
-
2007
Kjeller,
1990. 261
pp.
7
1.2.
GENERAL
SUMMARY
AND
CONCLUSIONS
HENNING DAHLGAARD', MANUELA NOTTER',
JOHN
E. BRITTAIN3, PER
STRAND4,
AINO RANTAVAARA'
AND
ELIS HOLM6
'Riss National Laboratory, DK
-
4000 Roskilde, Denmark.
2Swedish Environmental Protection Agency,
S

-
171
85
Solna, Sweden.
3Freshwater Ecology and Inland Fisheries Laboratory (LFI), University
of
Oslo,
Sars
gate
1,
0562
Oslo,
Norway.
4Norwegian Radiation Protection Authority, P.O.Box
55,
N
-
1340
0sterA.9,
Norway.
5Finnish Centre for Radiation and Nuclear Safety, P.O.Box 14, FIN
-
00881 Helsinki, Finland.
6Department of Radiation Physics, Lund University, Sweden.
INTRODUCTION
On
Monday, 28th April,
1986,
most Nordic radioecologists and health physicists realized the area
was being contaminated by debris from a serious nuclear accident. The cloud from Chernobyl had

already reached the Nordic countries
on
Sunday, 27th April, and contamination was to continue
during May. Figure 1.2.1 shows the resulting ground deposition of 137Cs
in
kBq
m-2
in
the Nordic
countries Denmark, Finland, Norway and Sweden. Off
the
map, the Chernobyl contamination
on
Iceland and Greenland was very low, whereas the deposition
on
the Faroe Islands was 0.6-4.5
kBq
137~~
m-2
The Nordic post-Chernobyl radioecology programme, RAD, consisted
of
four projects. The
main radionuclides chosen for study were the two radiocaesium nuclides, 137Cs and 134Cs, because
they appeared to be the most important contributors to doses to man after the Chernobyl accident,
and because they are relatively simple
to
measure. However, a few results for %rand 210Po were
also reported. The present chapter is intended to give an overview
of
the results from the RAD

programme.
RAD-1 (project leader Elis Holm) had a multiple purpose: methodology, training, quality
assurance and doses. Initially, a major task was
to
conduct a two-week post-graduate training
course
in
various aspects of radioecology. The course included 20 lectures by various Nordic
radioecologists. These are published elsewhere
(Holm,
editor). An exchange programme
permitting, preferentially, young scientists to stay for one or two weeks at another Nordic
laboratory, e.g. to adopt
a
new radiochemical method, was
also
conducted by RAD-1. Three
8
separate programmes on quality assurance were carried out. Of these, the intercomparison of nine
large, stationary air samplers and the intercalibration of
20
Nordic whole-body counting systems
are especially remarkable. Finally,
RAD-1
was responsible for dose assessments based partly on
the results produced in the three other
RAD
projects. The results from
RAD-1
are

given
in
chapter
5
and
in
Holm (editor).
RAD-2:
Aquatic ecosystems (project leader: Manuela Notter) mainly concerned Nordic lakes,
as the major problems
in
aquatic environments after the Chernobyl accident appeared
in
fresh-
water systems. However, two minor projects were run
in
the marine environment. The results from
RAD-2
are described in detail
in
chapter
2.
RAD-3:
Agricultural ecosystems (project leader: Per Strand) focused on various aspects of
Nordic agriculture
in
relation to nuclear contamination: annual crops, cows’ milk, grazing sheep
and on countermeasures.
RAD-3
also included a study of physico-chemical forms and

a
model
study. The results are given
in
chapter
3.
Finally
RAD-4:
Forest and alpine ecosystems (project leader: Aino Rantavaara) concerned
the natural terrestrial environment which, like the freshwater environment, appeared to surprise
the authorities with high and variable radionuclide levels after the Chernobyl accident. RAD-4
studied radiocaesium transfer from soil to plants and fungi, game animals, the reindeer foodchain
and boreal forests
in
general. The results are reported
in
chapter
4.
AQUATIC
ECOSYSTEMS
With respect to Nordic aquatic ecosystems, the main exposure pathway of
137Cs
to man after the
Chernobyl accident
has
been through the consumption of freshwater fish. Caesium accumulates
in
fish muscle due to its chemical similarity to potassium and the accumulation of 137Cs is
of
particular importance

in
the Nordic countries where ionic concentrations
in
freshwaters are
generally low. Chapter
2
identifies the important parameters determining radionuclide
concentrations in fish, thereby permitting the development and assessment
of
potential remedial
measures. Since the Chernobyl accident in 1986, there has been an intensive research effort
in
the
Nordic countries aimed at obtaining reliable input data for prediction models and determining the
important driving forces and parameters for such models.
Lakes received radionuclides from Chernobyl fallout via
two
sources: direct fallout on the
lake surface and leakage from
the
catchment. Chapter
2.2
describes fractionation techniques used
in
a study of the input of radiocaesium to three widely different Nordic lakes, Hillesjon
in
Sweden,
!&re Heimdalsvatn
in
Norway and Saarisjawi

in
Finland. Using hydrological data, the degree of
retention of
137Cs
in
these three lake systems was estimated. Transport of 137Cs
in
plant material
(Coarse Particulate Organic Material, CPOM) is considerable
in
Nordic lakes. Through its rapid
Figure
1.2.1.
Ground deposition
of
137Cs,
kBq
m-*,
in
Denmark, Finland, Norway and Sweden
resulting
from
the Chernobyl accident.
10
assimilation into the invertebrate foodchain, it is potentially a major source of
137Cs
for lake
ecosystems. CPOM transport is higher in mountain and forest lakes than in lowland lakes
in
agricultural areas. However,

in
all lakes almost all such plant material is retained
in
the lake. The
Nordic lakes studied differed
in
the concentration of 137Cs in the various molecular weight fractions
in
the water phase. Free ions may easily cross biological membranes and the low molecular weight
fraction is assumed to have a high degree of bioavailability. However, both organic and inorganic
substances in the water phase may affect the biological uptake of a given element.
In
fact, the low
molecular weight fraction showed
no
retention
in
the three study lakes and was exported
downstream. In contrast, half the colloidal (pseudocolloidal) fraction was retained during passage
through both &re Heimdalsvatn and Saarisjarvi.
In
Hillesjon, ten times more 137Cs flowed out
than flowed
in,
due to resuspension of 137Cs-ri~h sediments.
Although some of the radiocaesium
from
Chernobyl has been transported out of lakes
because
of

the high flows associated with the spring snowmelt at the time of deposition, most of
it still remains
in
lake sediments. Chapter
2.3
describes a study of the distribution, physico-
chemical
forms
and
concentration of radiocaesium
in
lake sediments.
In
1987,
137Cs was to a
large extent bound to chemically labile fractions, but it has subsequently been transformed to less
available fractions, thus reducing the tendency for resuspension. The horizontal distribution of
137Cs
in
the sediments is affected by the shape of the lake basin, steep-sloping bottoms tending to
focus the radiocaesium towards the deeper parts. The degree of bioturbation, diffusion and the rate
of
sedimentation determine the vertical distribution
of
137Cs
in
lake sediments. A strong tendency
for
resuspension was found
in

shallow lakes. Although this may transport 137Cs to deeper areas
where
it
is less available, it also increases its availability to the biota, delaying recovery
in
shallow
lakes.
The importance of leakage from catchment areas has been studied on a large scale
in
Finland,
where the whole country has been divided into seven different catchments, each with its own
characteristics with regard to fallout, soil type and topography (chapter
2.4).
However, during the
first year after the fallout the activity concentrations
in
lake waters and fish could be estimated
using simple relationships to the deposition.
In
subsequent years catchment characteristics played
an increasing role, leading to differences between lakes
in
the different catchment areas. For
example, a high incidence of bogs prolonged the decrease
of
137Cs in lake waters and
in
fish,
whereas a predominance of clay soils reduced the transfer
to

aquatic systems.
A
number of lake-specific factors, both abiotic and biotic, have been put forward as
determining the concentration of radiocaesium in fish. Chapter
2.5
describes a major study
encompassing a large number of Swedish lakes, and assesses the importance of a wide range of
such factors. The maximum activity concentration
in
fish was reached within three years
in
most