Transfer of radiocaesium from liehen to reindeer
Birgitta Ähman,
Department of Clinical Nutrition, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Introduction
A f t e r the C h e r n o b y l accident i n april 1986 a
large part of the reindeer hearding area i n Sweden was contaminated w i t h radioactive caesium
' C s and
C s ) . Lichens - the m a i n w i n t e r
forage for reindeer - were heavily contaminated. Large intake of lichens i n the w i n t e r results
in high activity concentrations of radiocaesium
in reindeer i n contaminated areas.
son et al, 1987) an w i t h i n the range of the deposit per m (from map b y S G A B , 1986).
D u r i n g the late sixties, after the nuclear weapons tests, caribou i n A l a s k a had levels of radiocaesium i n muscle about one t h i r d of the levels i n d r y lichens ( L u i c k , 1974). L i d e n and
Gustafsson (1967) reported levels of
C s in
reindeer meat i n the years 1961-65 to be about
50 % of the content of
C s i n one m of l i chen carpet.
A c t i v i t y concentrations of
C s i n reindeer
meat f r o m five saami villages has been c o m pared to the levels i n lichens and to the deposit
of
C s per m g r o u n d surface i n these saami
villages (Table 1). T h e amount of
C s i n reindeer meat ( B q / k g ) i n the first w i n t e r after the
C h e r n o b y l accident was approximately at the
same level as the amount i n d r y lichens ( B q / k g
dry weight) i n J u n e - O c t o b e r 1986 (from E r i k s -
Factors that influence the biological halflife of
radiocaesium i n reindeer, e.g. total food intake,
metabolic activity and amount of potassium
and fibre i n the diet, should also affect the level
of radiocaesium i n the b o d y at a given daily i n take. T h e amount of lichens i n the diet w i l l
thus be an important factor, since lichens contain o n l y small amounts of potassium and protein. Jones et al. (1989) has calculated fractional
2
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2
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2
Table 1. Radiocaesium fallout (kBq C s / m ) , activity concentration of C s in lichens, Cladina arbuscula,
(kBq/kg d.w.) and in reindeer meat (kBq/kg) from five saami villages.
1 3 7
Sami village
kBq/m
May-Och
1986*
2
2
1 3 7
k B q / k g d.w.
i n lichens
(Cladina
arbuscula)
J u n e - O c t 1986**
k B q / k g i n reindeer meat
D e c 1986-Feb 1987
mean
range
no of ;
Sörkaitum
0- 2
1.1
0.7
(0.3-
1.6)
n =
453
Tässäsen
2- 3
1.1, 1.9, 2.0, 2.3
1.5
(0.7- 2.1)
n =
19
Mittädalen
2- 5
2.2, 6.1
3.0
(1.3-
n =
212
Gran
5-20
7.1, 8.8, 10.0
11.5
(3.7-18.5)
n
=
113
15, 26, 39, 44
26.6
(14.5-56.3)
n
=
156
Vilhelmina norra
20-60
''"SGAB 1986
Rangifer, Special Issue
N o . 4,1990
6.5)
''-'"Eriksson et al. 1987
67
transfer f r o m grazing plants to meat ( B q / k g i n
meat relative to intake, B q / d a y ) . T h e values
were 0.65 d / k g i n F e b r u a r y , w h e n the l i c h e n
intake was about 65 % of the total diet, and
0.24 - 0.36 d / k g i n J u l y - September, w h e n l i chen intake was 17 % or less.
b y measuring external, radiation, using a gamma
detector (GRS-500) ( A h m a n 1988). A f t e r 35
days the animals were slaughtered and the activ i t y concentration of
C s i n muscle was measured.
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Results
Material and methods
T o test the influence of relative intake of l i chens o n transfer of radiocaesium f r o m lichen
to reindeer, a feeding experiment w i t h six one
year o l d male reindeer was performed i n A p r i l
- M a y 1989. T h e animals were fed different
amounts of lichens; 73 %, 40 % or 12 % of l i chen d . m . i n the feed respectively (two animals
o n each treatment). B y using lichens w i t h different activitiy concentrations of
C s the daily
intake c o u l d be kept at the same level, 1.8
k B q / d a y , for all animals. In c o m b i n a t i o n w i t h
lichens the animals were fed pelleted reindeer
feed and some hay. T h e total d r y matter intake
was 1500 g/clay.
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D u r i n g the experiment the level of radiocaesiu m i n the bodies o f the reindeer was evaluated
137CS
kBq/kg
in meat
D u r i n g the 35 days of feeding the b o d y weights
of the animals increased w i t h 5 k g at an average
(from 46 k g at an average at the start of the experiment).
T h e t w o reindeer receiving 73 % of lichens i n
their diet reached activity concentrations of
C s i n muscle about 0.5 times the daily intake
of
C s (Figure 1). T h i s relation was somewhat
l o w e r , 0.35 at an average, for reindeer receiving
40 % or 12 % of lichens i n their diet.
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1 3 7
References
Eriksson, O., Johansson, L., Wickman, M . &.Nyleh, T. 1987. Radioaktivt cesium i renbetet. Provtagningar 1986-06-02 - 1986-10-30. - Meddelande
från Vdxtbiologiska institutionen, Uppsala. 1987:2.
20 pp.
Jones, B. E. V., Eriksson, O . & Nordkvist, M .
1989. Radiocesium in reindeer on natural pasture. The Science of the Total Environment, 85:207 - 212.
Liden, K. & Gustafsson, M . 1976. Relationships and
seasonal variation of C s in lichen, reindeer and
man in northern Sweden 1961-1965. - In: Åberg,
B. & Hungate, F. P., eds., Radioecological concentration processes. Oxford, pp. 193-208.
1 3 7
Luick, J. R. 1974. Nutrition and metabolism in reindeer and caibou in Alaska. - Progress report U.S.A.E.C. Contract AT(45-1}2229, July 1973 - December
1974, Institute of Arctic Biology, University of
Alaska, Fairbanks Alaska. 109 pp.
Figure 1. External radiation from live reindeer during
the experiment and activity concentrations
of C s at slaughter. The reindeer were fed
73 % ( • ), 40 % ( O ) and ( A ) of lichens
respectively. A l l reindeer received 1.8 kBq
of i C s / d a y .
1 3 7
37
68
SGAB, 1986. Cesium-137 markbelaggning over Sverige. (Cesium-137 kBg/m^ ground surface). Map
based on areal surveys May - Oct 1986. - Swedish
Geological C O , Uppsala, Sweden.
Åhman, G . 1988. The association between caesium
in reindeer meat and external radiation from live
reindeer. - Report from Dept. of Animal Nutrition
and Husbandry, Swedish University of Agricultural
Sciences, Uppsala, Sweden. 5 pp.
Rangifer, Special Issue
N o . 4,1990