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Heavy metals in mushrooms and their relationship with soil characteristics
Chemosphere, Vol.17, No.4, Printed in Great Britain
pp
789-799,
1988
0045-6535/88 $3.00 Pergamon Press plc
+
HEAVY METALS IN MUSHROOMS AND THEIR RELATIONSHIP WITH SOIL CHARACTERISTICS
C.H. Gast , E. Jansen, J. Bierling, L. Haanstra Research Institute for Nature Management P.O. Box 9201, 6800 HB Arnhem, The Netherlands
Abstract Contents of Cd, Cu, Pb and Zn have been determined in wild growing mushrooms in polluted and unpolluted regions. Cd can be accumulated to high concentration ratios whereas Pb is excluded from the mushrooms. Concentration of Cu and Zn within the mushroom seems to be regulated. No relation with pH and organic matter content of the soil could be observed.
Introduction In a large number of publications data are given about the contents of heavy metals in mushrooms,
in cultivated and in wild growing mushrooms as well (I-20). Compared to green
plants, mushrooms can build up large concentrations of some heavy metals such as Cd and Hg (i, 2, 3, 7, I0, II, 15, 17, 19). As these metals are well-known for their toxicity at low concentrations,
a great deal of effort has been made to evaluate the possible danger to
human health from the ingestion of mushrooms. A review of this work is given by Seeger (25). Furthermore, mushrooms have been used as bioindicators
to investigate the
distribution of heavy metals from sources of contamination (I, 9, 14, 15, 19). Some work has been performed to study the relationship between the heavy-metal
content
in the mushroom and different parameters of the soil (i, 2, II, 17, 19). Brunnert and Zadrazil
(21-24) investigated
the uptake of Cd and Hg in experimental systems. Tyler (17)
has shown for two species that some metals are systematically accumulated while others are excluded from the mushroom. As higher fungi are engaged with the cycling of nutrients in soll by means of their mycelium,
they also are engaged with the cycling of heavy metals. Our first aim was to
study whether wild growing mushrooms are suitable bioindicators for heavy-metal pollution in soil. For this investigation, and relatively unpolluted
mushrooms and accessory soil were collected in polluted
regions to obtain an extended range of concentrations of heavy
metals. Our second aim was to investigate whether accumulation and exclusion patterns found by Tyler are applicable to more species and to a more extended range of concentrations. collected
For this the research was focused on six species of mushroom that could be
in satisfying numbers. The third aim was to study the relationship of
789
.OO
790
heavy-metal
contents
characteristics
of wild growing mushrooms with easily determinable
such as heavy-metal
concentration,
soil
pq, and organic-matter content.
Materials and methods In 1982, 1983, and 1984, we collected species
together with accessory
and adjacent parts of Belgium. the surroundings unpolluted
125 mushroom samples of 21 different,
soil samples
Two of these are affected by local pollution sources (in
of Budel and Beverwijk)
whereas the other two constitute a relatively
area (Veluwe en Drenthe).
Among the 21 different mushroom species, sites: Amanita muscaria
six were collected each at about
(L. ex Fr.) Hooker, Amanita rubescens
Suillus luteus (L. ex Ft.) S.F. Gray, Paxillus involutus aurantiaca
wild growing
(0-5 cm) in four regions in The Netherlands
(Wulf ex Fr.) R. Mre, and Lepista nebularis
have been washed with demineralized
(Pets. ex Fr.) S.F. Gray,
(Batsch) Fr., Hygrophoropsis
(Ft.) Harmaja. The mushroom samples
water, dried at 50 ° C overnight
automatic morter with achate beaker and pistle.
These samples generally
and crushed in an
Soils were sampled by taking 5 to i0 cores
(diameter of 8 cm) as close as possible to the sampled mushrooms, of mycelium.
15 different
avoiding visible clumbs
contained the first 5 cm directly under the
vegetation or the litter layer. For mushroom species with their mycellum growing mainly in the litter layer (Hygrophoropsis included
aurantiaca
and Lepista nebularis),
this layer was also
in the soll sample. Soil samples were dried at 50 ° C overnight,
sieved by hand in
order to remove stones and larger pieces of wood and ground using a cross-beater mill with a 1-mm sieve. Digestion of the mushroom samples was performed using concentrated for 2-5 g sample) water was added,
water.
Determinations atomic absorption
to a volume of i00 ml with demineralized
of heavy-metal spectrometry
to a
Soil samples have been extracted with 9%
acid (40 ml for 5 g soil) at i00 ° C for three hours. After cooling,
digests were brought
atomisation.
20 ml demineralized
the digest was again heated at 70° C for two hours and brought
volume of 200 ml with demineralized hydrochloric
nitric acid (16 ml
and heating at 70 ° C for three hours. After cooling,
concentrations
the
water.
(Cd, Cu, Pb, Zn) have been performed with
(Pye Unicam SP 190 and IL Video 12) using flame
For the determination
of Pb and Cd, deuterium
and Smith-Hieftje
background
correction have been used. Organic-matter
content
850 ° C. No corrections
in tne soil samples has been determined
as loss on ignition at
have been made as clay soils were not included
in the
investigation. Determination
of pH has been performed
linear regression analysis,
using a soil suspension
the statistical
in IM-KCI. For (multiple)
program package GENSTAT
(26) was used.
Results
Contents of Cd, Cu, Pb and Zn The result of sampling
in polluted
in a wide range of concentrations
and relatively unpolluted found in mushrooms
regions as well is reflected
and accessory
soil samples.
In table i, a summary is given of the contents of Cd, Cu, Pb, and Zn by means of the
791
minimum, maximum and median values. Median values are used instead of averages as, for the wide ranges found, median values give a better estimate of the most frequent concentrations.
Table i. Summary of Cd, Cu, Pb, and Zn concentrations (mg/kg dry matter) for 125 samples of mushrooms and accessory soils and summary of pH values and organic-matter contents (OM in g/kg dry matter) of the soll samples. Mushrooms .
.
.
.
.
.
.
.
min. 0.I 6.6
Cd Cu Pb Zn pH OM
.
.
.
.
.
Soil .
.
.
max. 88.4 286 412 1233 -
.
.
.
.
.
.
.
.
.
.
.
med. 5.8 58 6.0 175 -
.
.
.
.
.
.
.
.
.
.
.
mln. <0.05 1.0 7.0 4.0 2.44 12
.
.
.
.
.
max. 28.4 189 720 1183 6.65 760
med. 0.9 17.9 105 116 3.94 144
The median values of Cd and Cu concentrations in the mushrooms are high compared to the soil concentrations.
For Pb the opposite is the case, while for Zn the median values are
about equal. The majority of the samples (121 out of 125) have been collected from four regions in The Netherlands and adjacent parts of Belgium. Three of these regions can be subdivided into a number of smaller areas. In table 2, these regions and areas are listed together with the median values of the concentrations of Cd, Cu, Pb, and Zn in the mushrooms.
Table 2. Median values of Cd, Cu, Pb, and Zn (in mg/kg dry matter) for mushrooms collected in different regions (B=Belgium).
region
subregion
Drenthe
n 19
Diever Steenwijk Havelte Dwingeloo Beverwijk Veluwe
54.8 3.5 3.3 9.5 2.4
5.9
35 Lunteren Hoge Veluwe Wageningen Arnhem
Budel
3.3 8 7 2 2
Ii
3.3
177
114 I.I 3.7 1.9 7.8
8.5 60.0 66.5 51.7 55.3 71.0 54.5
188 199 148 131 136
3.3 70.1 57.8 36.0 76.8
55.0 9.6 6.0 14.6 19.6 13.5 13.7
Zn
3.3 3.2 3.3 12.0 7.0
57.0 1.2 2.6 2.1 2.9
13.4
Pb
65.9 66.9 27.7 17.5 128
2.5 4 6 9 16
56 Maarheeze 7 Lommel (B) 4 Budel 24 Weerterbergen 14 Overpelt (B) 3 Tungelerwallen 4
median Cu
Cd
117 149 149 99 215
5.2 10.2 8.1 8.6 15.1 64.6
243 268 257 158 262 125
Elevated levels of Cd, Pb, and Zn are found in the southern part of The Netherlands (around Budel) where the influence of zinc smelters is well known. For copper, the median values in this region are in agreement with the values found in Drenthe and the Veluwe.
792
However, elevated
levels of copper are found around BeverwiJk which is expected
to be due
to the influence of a nearby steel factory.
C o n t e n t s and a c c u m u l a t i o n i n d i f f e r e n t For s i x s p e c i e s
with at
least
species
14 s a m p l e s t h e r a n g e s ,
deviations
o f t h e mushroom c o n c e n t r a t i o n s
classified
as saprophytic
or mycorrhiza forming types.
b o t h t y p e s w h i c h c a n n o t be d e t e r m i n e d Cd c o n c e n t r a t i o n s has a consistently
median values,
are given in table
heavily
Paxillus
tnvolutus
on t h e c o n t r a r y ,
can b e l o n g t o
of Cd ( m e d i a n :
F o r example Amanita m u s c a r i a
2 7 . 9 m g / k g ) and Amanita r u b e s c e n s a l s o h a s a
h i g h m e d i a n v a l u e o f 16.2 mg/kg a l t h o u g h t h e r a n g e i s more e x t e n d e d . involutus
t h e Cd c o n c e n t r a t i o n s
are rather
For P a x i l l u s
low ( m e d i a n :
1.2 m g / k g ) .
Table 3. Summary of Cd, Cu, Pb and Zn concentrations (in mg/kg dry matter) of mushrooms (m = mycorrhiza forming, s= saprophytic). species type n Cd minimum maximum median average stand, dev. Cu minimum maximum median average stand, dev. Pb mi--nlmum maximum median average stand, dev. Zn mi---nimum maximum median average stand, dev.
A.musc. m 19
A.rube. m 14
S.lute. m 14
12.8 47.8 27.9 28.3 8.7
3.7 46.0 16.2 20.9 15.8
0.6 13.0 5.8 5.4 3.9
36.7 77.0 52.5 52.8 10.5
40.7 83.0 62.0 63.7 12.3
1.4 20.1 6.0 7.2 5.9
173 394 291 279 66
99 272 176 182 55
and s t a n d a r d
can be
in the field.
depend on t h e t y p e o f s p e c i e s .
high level
averages,
3. The s p e c i e s
H.aura. s 16
L.nebu. s 15
0.2 7.4 1.2 1.9 2.1
2.4 20.7 10.2 I0.i 5.4
1.8 66.0 7.6 16.6 23.8
18.0 63.0 27.1 30.6 12.8
60.0 108 83.0 84.3 13.1
18.2 33.0 25.5 26.2 4.1
60.6 242 128 132 53.3
1.9 11.8 3.8 5.2 2.9
6.2 412 15.1 40.9 99
3.2 120 9.4 17.5 28.7
68 600 127 177 141
P.invo. m2-s 17
154 330 232 237 54
The median values for Cu are less divergent
74 1233 101 234 322
for six species
89 154 108 ii0 16
compared to Cd. The highest values are
found for Lepista nebularis which also shows the largest range. The lowest values are found for Hy~rophoropsls Concentrations
aurantlaca.
of Pb are generally
low except for two samples (both from nearly the same
spot in the region of Budel) with concentrations 120 mg/kg (Leplsta nebularis).
of 412 (Hygrophoropsis
from the overal median of 6.0 (table I) and the median values species not influenced
aurantiaca)
and
These are exceptionally high values as can be concluded
by these outliers.
(table 3) of the four
Also for Zn, some exceptionally
tions of more than I000 mg/kg are found in the mushroom.
high concentra-
Generally the ranges for Zn vary
by a factor 2-3. The highest median values are found for Amanlta muscarla and Paxillus
793
involutus and the lowest for Hy~rophoropsis aurantlaca (which has the highest value of 1233 mg/kg!).
Cr 1000
Cu
Cd
Zn
Pb
50O 2OO 1 O0
2O 50 ~ 10
I
5 2
1
I I
I
T -j
Q2
H
0.1 0115
O.O2 1101 0.005 0,002
I
Fig. i.
one sample
Histograms of the concentration ratio ( C ) of Cd, Cu, Zn and Pb for all samples r investigated. Concentration ratios are indicated on the vertical axis. The blocksize of one sample is indicated separately.
At each collection site of a mushroom sample, also a soil sample was taken. Therefore, a concentration ratio (Cr) can be calculated as the metal concentration in the mushroom divided by the metal concentration of the soil. The concentration ratios of all samples investigated are presented in fig. 1 in the form of a histogram on a logarithmic scale. As was found already from the data in table I, it can be seen clearly that accumulation is found for Cd and Cu, whereas Pb shows a definite exclusion pattern and Zn has an intermediate position. Cd shows the highest concentration ratios but the pattern is quite similar to Cu when the highest values are excluded. In figure 2a, b, and c the concentration ratios for slx species are shown separately. Generally the same trends as in flg. I are found. Paxillus involutus shows a clearly different behaviour with low C r values for Cd and somewhat higher C r values for Cu and Zn.
Relationships wlth soll characteristics The relationship between the metal concentration in the mushroom and that in the soil can be visualized in different ways. The concentration ratio gives an idea of the accumulation and exclusion patterns as shown above. Anether way is by representing the data in a logarithmic plot of the concentration ratio versus the metal concentration in the soil. When the concentration
ratio has a constant value, this plot must show a simple horizontal
line. For none of the six mushroom species and heavy metals investigated such a relationship was found. Assuming that the concentration
in the mushroom has a constant
value it can be derived easily that the logarithm of the concentration ratio must decrease linearly when plotted versus the logarithm of the soil concentration. plot is given for Zn where the data of all samples are included.
In fig. 3 such a
794
Cr Cu
Cd
1000
Zn
Pb
500 200 100 50 2O 10 5 2 1 05 02 0.1 O05 Q02 G01 0005 ~002
one sample
[]
Amanita muscarJa
[]
Amanita rubescens
Cr Cd
Cu
Zn
Pb
1000
500 200 100 2O 10 5 2 115 02 0.1 1105 0O2 001 0.005
[]
Suillus luteus
[]
Paxillus involutus
Cr 1000 soo -~ 200 100 50 20
Cu
Cd
]
1° 7
Zn
Pb
~
S 1 115Q20.1QO5002.
[]
Fig. 2.
Hygrophoropsis aurantiaca
[]
Lepista nebularis
Concentration ratios for Cd, Cu, Zn, and Pb of the samples of: 2A) Amanlta muscarla and Amanlta rubescens 2B) ~fi-rII-usute~nd P a x - ~ i n v o l u t u s 2C) ~ o r ' o - p s l s auranta-~nd Leplsta nebularls
795
C 1.
50-
.{ 10 .o
5
°.'.
~
..°
•
•
• °°%°. :
"..
:-
: °.
0..=
•
®
...;
~ : : ..
10
,
l
100
1000
Zn soil ( r n g / k g d r y w t )
Fig. 3.
Relationship between the concentration ratio (Cr) and the soll concentration of Zn for all samples investigated.
A remarkable narrow zone is found indicating a trend of constant zinc concentrations in the mushroom irrespective of the soil concentration.
In case of copper, this trend is also
found although less pronounced compared to zinc. For Cd and Pb, the data points in this type of plot are very scattered when all data are included. A third way of considering the data of the metal concentrations
in mushroom and soil is
a plot of the metal concentration in the soil versus the metal concentration in the mushroom. For Cd remarkable differences the data for Amanita muscaria
between species are observed (fig. 4a, b, c). From
(fig. 4c) a regression line can be calculated with a small,
but significant slope (0.i). However, since this value is so small it seems best to conclude that Amanlta muscaria shows a constant, high level of cadmium which is hardly influenced by the soll concentration.
The results for Amanita rubescens (fig. 4a) are
scattered and difficult to interpret,
but resemble those of A. muscaria.
involutus
Paxillus
(fig. 4b), Hygrophoropsis aurantiaca (fig, 4b), Suillus luteus (fig. 4a) and
Lepista nebularis
(fig. 4c) show an increasing Cd concentration in the mushroom with
increasing soil concentrations.
The data for Lepista nebularis increase sharply at soll
concentrations above 3 mg/kg to mushroom concentrations of about 60 mg/kg. In the case of Zn and Cu, these plots show the expected trend of constant metal concentrations in the mushrooms. This concentration level varies for different species as can also be seen from the average and median values and the standard deviations in table 3. The data for Pb are very scattered and no trends can be discovered.
796
Cd mushr ( m g / k g d r y wt]
Cd mushr ( m g l k g d r y wt)
A
100-
B
100.
oo o 0.1
1
1 Cd soil ( m g / k 9 dry wt)
10
Cd soil ( m g / k g d r y wt)
10
Cd mushr ( m g / k g d r y wt)
C
tO0
o o o
Fig. 4 Relationship between Cd concentrations in the soll and in the mushroom for six species. A solid llne indicates that the slope is significantly different from zero (P>0.01). 4A) Amanlta rubescens (4) and Suillus luteus (A) 4B) Paxillus involutus (o) and Hygrop~oropsis aurantiaca (e) 4C) Amanlta muscarla (o) and Leplsta nebularls (m)
o
o o
o
O.T
Cd soil (mglkg dry wt)
Besides by the various
plots described above,
the relationships
between the metal concen-
tration in the mushroom and the three soll parameters have been investigated the six species mentioned analysis explain
above by (multiple)
linear regression analysis.
it was found that pH and organic matter content as single parameters the variation
of the metal concentration
in the soll proves to be a significant the graphical parameters
representations.
in the mushroom.
for each of
From this do not
The metal concentration
parameter only for Cd, as was expected already from
A multiple linear regression model including all three soil
gives somewhat better results compared to the single parameter model (table 4).
For five species out of six this model accounts Cd concentration
in the mushroom.
when using the multiple
There
is a remarkable
the variation
of the
increase for Amanita rubescens
linear regression model. 0nly in case of Amanlta muscarla,
model does not fit. For the other metals used explains
for 70-80% of the total variability
this
(Cu, Pb, and Zn), none of the regression models
of the metal concentration
in the mushroom.
797
Table 4. Percentage variability of the Cd concentration in the mushroom accounted for by (multiple) linear regression models (A : pH; B : organic matter; C : Cd concentration of the soil; D : pH, organic matter and Cd concentration of the soil).
Amanita muscaria Amanita rubescens Suillus luteus Paxillus involutus Hygrophoropsis aurant. Leplsta nebularls
A
B
C
D
2 3 16 0 0 0
8 0 0 0 19 0
36 20 72 62 83 73
29 78 70 80 82 80
Discussion The results found in our work do not give an explicit answer on the question whether mushrooms
can be used as blolndlcators
figs. 2, 3, and 4 give the impression contamination
pollution.
The data presented
in for
with Cu, Pb, and Zn, while for Cd it depends on the species. Amanita
muscaria for example is not useful irrespective
for heavy-metal
that mushrooms are not suitable as blolndicators
because this species contains high Cd concentrations
of the soll concentration.
the four regions Drenthe, contamination
Beverwijk,
in the surroundings
reflected by the heavy-metal species characteristics
However,
when the data are summarized
for each of
Veluwe, and Budel (table 2) the well-known
of Budel (Cd, Pb, Zn) and Beverwijk
concentrations
in the mushrooms.
and local circumstances
(Cu, Pb) is
Probably the differences
found in one area are put together. When three of the four regions are divided areas and consequently concentrations
as bioindicators from different
the number of samples decreases,
become visible
(table 2). Therefore,
for heavy-metal
in
are averaged when a number of species
large differences
in smaller
in heavy-metal
we conclude that mushrooms
pollution only if sufficient
can be used
(20-40) samples are taken
places in an area large enough to provide samples of at least 8-10 species
in suitable amounts. The levels of metal concentration as reported elsewhere
more or less narrow range, indicating concentrations
in the mushrooms
(1-20). The concentrations
are of the same order of magnitude,
of Cu and Zn in the mushrooms
are in a
that mushrooms are able to regulate their
within certain limits. As Cu and Zn are essential
elements probably the
cell membrane has a transport and/or regulation system for them. On the other hand Cd and Pb are not essential mlcroelements is very effectively involutus.
excluded,
and the differences
Cd is accumulated
in uptake are remarkable:
up to very high levels except
Our results with the four metals Investigated
(16) with Collybla peronata
and exclusion.
The overall data
behaviour
is found for Paxillus
involutus
of Cd occurs with this species. Tyler reports a deviating behaviour
Amanita rubescens
having relatively low concentration
No difference must be concluded
between saprophytic
~nd mycorrhizal
that the accumulation
species.
This is illustrated
as
for
ratios for Cd. This is not confirmed
by our results as we find relatively high concentration
individual
rubescens.
(fig. 2) show the same trends of accumulation
In the case of Cd, a deviating
no accumulation
do agree with the work of Tyler
(Bolt. ex Fr.) Sing. and Amanlta
(fig. I) and the data for the six species
where Pb
for Paxillus
ratios for this species.
forming species was observed.
of Cd depends only on the characteristics by the deviating
behaviour of Paxillus
So it of
involutus
798
which can only be explained
by assuming an exclusion mechanism
Our final conclusion with respect to the accumulation
by Tyler is that, at least for the four metals investigated species also at an extended The heavy-metal organic-matter
for Cd in this species.
and exclusion patterns reported here~ it is valid for most
range of concentrations.
concentrations
in the mushroom are hardly affected
by pH and
content of the soil. This was rather unexpected as these parameters
generally supposed
are
to influence mobility and availability
of heavy metals in the soil. It
can be due to the low pH values of all soils investigated
that in this pH range no effect
on the solubility and consequently observed.
Considering
on the uptake of heavy metals by mushrooms
the organic-matter
composition of the organic matter differs
strongly between
litter, fermentation,
and mineral layers of the soil. The influence on mobility and availability depends on certain humic fractions total organic-matter composition~
was
content it must be pointed out first that the
of the organic matter
content was determined
humus,
of heavy metals
(27). The fact that only the
without further information on the
probably made that no effect was found of the organic matter content on the
uptake of heavy metals by mushrooms. Brunnert and Zadrazil
(24) concluded
from experimental
uptake studies that cadmium and
zinc compete for being resorbed by the fruiting bodies. However,
Seeger (25) concluded
from other work that there is no correlation between cadmium and zinc contents growing mushrooms, contradictory
while also our data do not provide such a correlation.
findings
illustrate
that a relationship
with environmental
exist without being found in field studies due to too many interfering
in wild
These parameters
can
factors.
Acknowledgements We would like to thank Mr. E. Koopman for his contribution to the heavy-metal analysis and Dr. P. Doelman, Dr. H.J.P. Eijsackers and Dr. R.A. Prins for their helpful comments in this project.
References I. 2. 3. 4. 5. 6. 7. 8. 9. I0. II. 12. 13. 14. 15. 16. 17. 18.
P. Stegnar, L. Kosta, A.R. Byrne and V. Ravnlk (1973), Chemosphere 2, 57-63 T. Stijve and R. Roschnik (1974), Tray. chim. aliment, hyg., 65, 209-220 R. Seeger (1976), Z. Lebensm. Unters.-Forsch. 160, 303-312 R. Seeger, E. Meyer and S. Sch~nhut (1976), Z. Lebensm. Unters.-Forsch. 162, 7-10 T. Stijve and R. Besson (1976), Chemosphere ~, 1 5 1 - 1 5 8 T. Stijve (1977), Z. Lebensm. Unters.-Forsch. 164, 201-203 H-U. Meisch, J.A. Schmltt and W. Reinle (1977), Z. Naturforsch., 32c, 172-181 J.A. Schmitt, H-U. Meisch and W. Reinle (1977), Z. Naturforsch., 32c, 712-723 M. Enke, H. Matschiner and M.K. Aehtzehn (1977), Die Nahrung, 21, 331-334 R.O. Allen and E. Steinnes (1978), Chemosphere 4, 371-378 J. Fleckensteln (1979), Mitteilgn, Dtsch. Boden~undl. Gesellsch., 29, 451-456 K. Minagawa, T. Sasaki, Y. Taklzawa, R. Tamura, T. Oskina (1980), Bull. Environm. Cont. and Tox., 25, 382-388 A.R. Byrne, V. Ravnik and L. Kosta (1976), Science of the Tot. Environm. 6, 65-78 M. Lodenius, T. Kuusl, K. Laaksovlrta, H. Liukkonen-LilJa and S. Piepponen (1981), Ann. Bot. Fennici 18, 183-186 T. Kuusl, K. Laaksovirta, H. Liukkonen-Lilja, M. Lodenius and S. Piepponen (1981), Z. Lebensm. Unters.-Forsch., 173, 261-267 G. Tyler (1982), Trans. Br. Mycol. Soc., 79, 239-245 G. Tyler (1982), Chemosphere II, 1141-114-6H. Liukkonen, T. Kuusl, K. Laa-ksovirta, M. Lodenius and S. Piepponen (1983), Z. Lebensm. Unters.-Forsch., 176, 120-123
799
19. 20. 21. 22. 23. 24. 25. 26.
R. Bargagll and F. Baldi (1984), Chemosphere 13, 1059-1071 G. Santoprete and G. Innocenti (1984), Micologia Italiana 13, 11-28 H. Brunnert and F. Zadrazil (1980), Eur. J. Appl. Microbio~?. Biotechnol. i0, 145-154 H. Brunnert and F. Zadrazil (1981), Eur. J. Appl. Microbiol. Biotechnol. 12, 179-182 H. Brunnert and F. Zadrazil (1983), Eur. J. Appl. Microbiol. Biotechnol. 17, 358-364 H. Brunnert and F. Zadrazil (1985), Angew. Botanik 59, 469-477 R. Seeger (1982), Dtsch. Apoth. Ztg. 122, 1835-1844 N. Alvey, N. Galway and P. Lane (1982), An introduction to GENSTAT~ Academic Press, London 27. K.A. Daum & L.W. Newland (1982), Complexing effects on behaviour of some metals. In: O. Hutzinger (ed.), The handbook of environmental chemistry, volume 2, part B, Springer Verlag, New York, p. 129. (Received
in Germany
29 J u n e
1987)
pp
789-799,
1988
0045-6535/88 $3.00 Pergamon Press plc
+
HEAVY METALS IN MUSHROOMS AND THEIR RELATIONSHIP WITH SOIL CHARACTERISTICS
C.H. Gast , E. Jansen, J. Bierling, L. Haanstra Research Institute for Nature Management P.O. Box 9201, 6800 HB Arnhem, The Netherlands
Abstract Contents of Cd, Cu, Pb and Zn have been determined in wild growing mushrooms in polluted and unpolluted regions. Cd can be accumulated to high concentration ratios whereas Pb is excluded from the mushrooms. Concentration of Cu and Zn within the mushroom seems to be regulated. No relation with pH and organic matter content of the soil could be observed.
Introduction In a large number of publications data are given about the contents of heavy metals in mushrooms,
in cultivated and in wild growing mushrooms as well (I-20). Compared to green
plants, mushrooms can build up large concentrations of some heavy metals such as Cd and Hg (i, 2, 3, 7, I0, II, 15, 17, 19). As these metals are well-known for their toxicity at low concentrations,
a great deal of effort has been made to evaluate the possible danger to
human health from the ingestion of mushrooms. A review of this work is given by Seeger (25). Furthermore, mushrooms have been used as bioindicators
to investigate the
distribution of heavy metals from sources of contamination (I, 9, 14, 15, 19). Some work has been performed to study the relationship between the heavy-metal
content
in the mushroom and different parameters of the soil (i, 2, II, 17, 19). Brunnert and Zadrazil
(21-24) investigated
the uptake of Cd and Hg in experimental systems. Tyler (17)
has shown for two species that some metals are systematically accumulated while others are excluded from the mushroom. As higher fungi are engaged with the cycling of nutrients in soll by means of their mycelium,
they also are engaged with the cycling of heavy metals. Our first aim was to
study whether wild growing mushrooms are suitable bioindicators for heavy-metal pollution in soil. For this investigation, and relatively unpolluted
mushrooms and accessory soil were collected in polluted
regions to obtain an extended range of concentrations of heavy
metals. Our second aim was to investigate whether accumulation and exclusion patterns found by Tyler are applicable to more species and to a more extended range of concentrations. collected
For this the research was focused on six species of mushroom that could be
in satisfying numbers. The third aim was to study the relationship of
789
.OO
790
heavy-metal
contents
characteristics
of wild growing mushrooms with easily determinable
such as heavy-metal
concentration,
soil
pq, and organic-matter content.
Materials and methods In 1982, 1983, and 1984, we collected species
together with accessory
and adjacent parts of Belgium. the surroundings unpolluted
125 mushroom samples of 21 different,
soil samples
Two of these are affected by local pollution sources (in
of Budel and Beverwijk)
whereas the other two constitute a relatively
area (Veluwe en Drenthe).
Among the 21 different mushroom species, sites: Amanita muscaria
six were collected each at about
(L. ex Fr.) Hooker, Amanita rubescens
Suillus luteus (L. ex Ft.) S.F. Gray, Paxillus involutus aurantiaca
wild growing
(0-5 cm) in four regions in The Netherlands
(Wulf ex Fr.) R. Mre, and Lepista nebularis
have been washed with demineralized
(Pets. ex Fr.) S.F. Gray,
(Batsch) Fr., Hygrophoropsis
(Ft.) Harmaja. The mushroom samples
water, dried at 50 ° C overnight
automatic morter with achate beaker and pistle.
These samples generally
and crushed in an
Soils were sampled by taking 5 to i0 cores
(diameter of 8 cm) as close as possible to the sampled mushrooms, of mycelium.
15 different
avoiding visible clumbs
contained the first 5 cm directly under the
vegetation or the litter layer. For mushroom species with their mycellum growing mainly in the litter layer (Hygrophoropsis included
aurantiaca
and Lepista nebularis),
this layer was also
in the soll sample. Soil samples were dried at 50 ° C overnight,
sieved by hand in
order to remove stones and larger pieces of wood and ground using a cross-beater mill with a 1-mm sieve. Digestion of the mushroom samples was performed using concentrated for 2-5 g sample) water was added,
water.
Determinations atomic absorption
to a volume of i00 ml with demineralized
of heavy-metal spectrometry
to a
Soil samples have been extracted with 9%
acid (40 ml for 5 g soil) at i00 ° C for three hours. After cooling,
digests were brought
atomisation.
20 ml demineralized
the digest was again heated at 70° C for two hours and brought
volume of 200 ml with demineralized hydrochloric
nitric acid (16 ml
and heating at 70 ° C for three hours. After cooling,
concentrations
the
water.
(Cd, Cu, Pb, Zn) have been performed with
(Pye Unicam SP 190 and IL Video 12) using flame
For the determination
of Pb and Cd, deuterium
and Smith-Hieftje
background
correction have been used. Organic-matter
content
850 ° C. No corrections
in tne soil samples has been determined
as loss on ignition at
have been made as clay soils were not included
in the
investigation. Determination
of pH has been performed
linear regression analysis,
using a soil suspension
the statistical
in IM-KCI. For (multiple)
program package GENSTAT
(26) was used.
Results
Contents of Cd, Cu, Pb and Zn The result of sampling
in polluted
in a wide range of concentrations
and relatively unpolluted found in mushrooms
regions as well is reflected
and accessory
soil samples.
In table i, a summary is given of the contents of Cd, Cu, Pb, and Zn by means of the
791
minimum, maximum and median values. Median values are used instead of averages as, for the wide ranges found, median values give a better estimate of the most frequent concentrations.
Table i. Summary of Cd, Cu, Pb, and Zn concentrations (mg/kg dry matter) for 125 samples of mushrooms and accessory soils and summary of pH values and organic-matter contents (OM in g/kg dry matter) of the soll samples. Mushrooms .
.
.
.
.
.
.
.
min. 0.I 6.6
Cd Cu Pb Zn pH OM
.
.
.
.
.
Soil .
.
.
max. 88.4 286 412 1233 -
.
.
.
.
.
.
.
.
.
.
.
med. 5.8 58 6.0 175 -
.
.
.
.
.
.
.
.
.
.
.
mln. <0.05 1.0 7.0 4.0 2.44 12
.
.
.
.
.
max. 28.4 189 720 1183 6.65 760
med. 0.9 17.9 105 116 3.94 144
The median values of Cd and Cu concentrations in the mushrooms are high compared to the soil concentrations.
For Pb the opposite is the case, while for Zn the median values are
about equal. The majority of the samples (121 out of 125) have been collected from four regions in The Netherlands and adjacent parts of Belgium. Three of these regions can be subdivided into a number of smaller areas. In table 2, these regions and areas are listed together with the median values of the concentrations of Cd, Cu, Pb, and Zn in the mushrooms.
Table 2. Median values of Cd, Cu, Pb, and Zn (in mg/kg dry matter) for mushrooms collected in different regions (B=Belgium).
region
subregion
Drenthe
n 19
Diever Steenwijk Havelte Dwingeloo Beverwijk Veluwe
54.8 3.5 3.3 9.5 2.4
5.9
35 Lunteren Hoge Veluwe Wageningen Arnhem
Budel
3.3 8 7 2 2
Ii
3.3
177
114 I.I 3.7 1.9 7.8
8.5 60.0 66.5 51.7 55.3 71.0 54.5
188 199 148 131 136
3.3 70.1 57.8 36.0 76.8
55.0 9.6 6.0 14.6 19.6 13.5 13.7
Zn
3.3 3.2 3.3 12.0 7.0
57.0 1.2 2.6 2.1 2.9
13.4
Pb
65.9 66.9 27.7 17.5 128
2.5 4 6 9 16
56 Maarheeze 7 Lommel (B) 4 Budel 24 Weerterbergen 14 Overpelt (B) 3 Tungelerwallen 4
median Cu
Cd
117 149 149 99 215
5.2 10.2 8.1 8.6 15.1 64.6
243 268 257 158 262 125
Elevated levels of Cd, Pb, and Zn are found in the southern part of The Netherlands (around Budel) where the influence of zinc smelters is well known. For copper, the median values in this region are in agreement with the values found in Drenthe and the Veluwe.
792
However, elevated
levels of copper are found around BeverwiJk which is expected
to be due
to the influence of a nearby steel factory.
C o n t e n t s and a c c u m u l a t i o n i n d i f f e r e n t For s i x s p e c i e s
with at
least
species
14 s a m p l e s t h e r a n g e s ,
deviations
o f t h e mushroom c o n c e n t r a t i o n s
classified
as saprophytic
or mycorrhiza forming types.
b o t h t y p e s w h i c h c a n n o t be d e t e r m i n e d Cd c o n c e n t r a t i o n s has a consistently
median values,
are given in table
heavily
Paxillus
tnvolutus
on t h e c o n t r a r y ,
can b e l o n g t o
of Cd ( m e d i a n :
F o r example Amanita m u s c a r i a
2 7 . 9 m g / k g ) and Amanita r u b e s c e n s a l s o h a s a
h i g h m e d i a n v a l u e o f 16.2 mg/kg a l t h o u g h t h e r a n g e i s more e x t e n d e d . involutus
t h e Cd c o n c e n t r a t i o n s
are rather
For P a x i l l u s
low ( m e d i a n :
1.2 m g / k g ) .
Table 3. Summary of Cd, Cu, Pb and Zn concentrations (in mg/kg dry matter) of mushrooms (m = mycorrhiza forming, s= saprophytic). species type n Cd minimum maximum median average stand, dev. Cu minimum maximum median average stand, dev. Pb mi--nlmum maximum median average stand, dev. Zn mi---nimum maximum median average stand, dev.
A.musc. m 19
A.rube. m 14
S.lute. m 14
12.8 47.8 27.9 28.3 8.7
3.7 46.0 16.2 20.9 15.8
0.6 13.0 5.8 5.4 3.9
36.7 77.0 52.5 52.8 10.5
40.7 83.0 62.0 63.7 12.3
1.4 20.1 6.0 7.2 5.9
173 394 291 279 66
99 272 176 182 55
and s t a n d a r d
can be
in the field.
depend on t h e t y p e o f s p e c i e s .
high level
averages,
3. The s p e c i e s
H.aura. s 16
L.nebu. s 15
0.2 7.4 1.2 1.9 2.1
2.4 20.7 10.2 I0.i 5.4
1.8 66.0 7.6 16.6 23.8
18.0 63.0 27.1 30.6 12.8
60.0 108 83.0 84.3 13.1
18.2 33.0 25.5 26.2 4.1
60.6 242 128 132 53.3
1.9 11.8 3.8 5.2 2.9
6.2 412 15.1 40.9 99
3.2 120 9.4 17.5 28.7
68 600 127 177 141
P.invo. m2-s 17
154 330 232 237 54
The median values for Cu are less divergent
74 1233 101 234 322
for six species
89 154 108 ii0 16
compared to Cd. The highest values are
found for Lepista nebularis which also shows the largest range. The lowest values are found for Hy~rophoropsls Concentrations
aurantlaca.
of Pb are generally
low except for two samples (both from nearly the same
spot in the region of Budel) with concentrations 120 mg/kg (Leplsta nebularis).
of 412 (Hygrophoropsis
from the overal median of 6.0 (table I) and the median values species not influenced
aurantiaca)
and
These are exceptionally high values as can be concluded
by these outliers.
(table 3) of the four
Also for Zn, some exceptionally
tions of more than I000 mg/kg are found in the mushroom.
high concentra-
Generally the ranges for Zn vary
by a factor 2-3. The highest median values are found for Amanlta muscarla and Paxillus
793
involutus and the lowest for Hy~rophoropsis aurantlaca (which has the highest value of 1233 mg/kg!).
Cr 1000
Cu
Cd
Zn
Pb
50O 2OO 1 O0
2O 50 ~ 10
I
5 2
1
I I
I
T -j
Q2
H
0.1 0115
O.O2 1101 0.005 0,002
I
Fig. i.
one sample
Histograms of the concentration ratio ( C ) of Cd, Cu, Zn and Pb for all samples r investigated. Concentration ratios are indicated on the vertical axis. The blocksize of one sample is indicated separately.
At each collection site of a mushroom sample, also a soil sample was taken. Therefore, a concentration ratio (Cr) can be calculated as the metal concentration in the mushroom divided by the metal concentration of the soil. The concentration ratios of all samples investigated are presented in fig. 1 in the form of a histogram on a logarithmic scale. As was found already from the data in table I, it can be seen clearly that accumulation is found for Cd and Cu, whereas Pb shows a definite exclusion pattern and Zn has an intermediate position. Cd shows the highest concentration ratios but the pattern is quite similar to Cu when the highest values are excluded. In figure 2a, b, and c the concentration ratios for slx species are shown separately. Generally the same trends as in flg. I are found. Paxillus involutus shows a clearly different behaviour with low C r values for Cd and somewhat higher C r values for Cu and Zn.
Relationships wlth soll characteristics The relationship between the metal concentration in the mushroom and that in the soil can be visualized in different ways. The concentration ratio gives an idea of the accumulation and exclusion patterns as shown above. Anether way is by representing the data in a logarithmic plot of the concentration ratio versus the metal concentration in the soil. When the concentration
ratio has a constant value, this plot must show a simple horizontal
line. For none of the six mushroom species and heavy metals investigated such a relationship was found. Assuming that the concentration
in the mushroom has a constant
value it can be derived easily that the logarithm of the concentration ratio must decrease linearly when plotted versus the logarithm of the soil concentration. plot is given for Zn where the data of all samples are included.
In fig. 3 such a
794
Cr Cu
Cd
1000
Zn
Pb
500 200 100 50 2O 10 5 2 1 05 02 0.1 O05 Q02 G01 0005 ~002
one sample
[]
Amanita muscarJa
[]
Amanita rubescens
Cr Cd
Cu
Zn
Pb
1000
500 200 100 2O 10 5 2 115 02 0.1 1105 0O2 001 0.005
[]
Suillus luteus
[]
Paxillus involutus
Cr 1000 soo -~ 200 100 50 20
Cu
Cd
]
1° 7
Zn
Pb
~
S 1 115Q20.1QO5002.
[]
Fig. 2.
Hygrophoropsis aurantiaca
[]
Lepista nebularis
Concentration ratios for Cd, Cu, Zn, and Pb of the samples of: 2A) Amanlta muscarla and Amanlta rubescens 2B) ~fi-rII-usute~nd P a x - ~ i n v o l u t u s 2C) ~ o r ' o - p s l s auranta-~nd Leplsta nebularls
795
C 1.
50-
.{ 10 .o
5
°.'.
~
..°
•
•
• °°%°. :
"..
:-
: °.
0..=
•
®
...;
~ : : ..
10
,
l
100
1000
Zn soil ( r n g / k g d r y w t )
Fig. 3.
Relationship between the concentration ratio (Cr) and the soll concentration of Zn for all samples investigated.
A remarkable narrow zone is found indicating a trend of constant zinc concentrations in the mushroom irrespective of the soil concentration.
In case of copper, this trend is also
found although less pronounced compared to zinc. For Cd and Pb, the data points in this type of plot are very scattered when all data are included. A third way of considering the data of the metal concentrations
in mushroom and soil is
a plot of the metal concentration in the soil versus the metal concentration in the mushroom. For Cd remarkable differences the data for Amanita muscaria
between species are observed (fig. 4a, b, c). From
(fig. 4c) a regression line can be calculated with a small,
but significant slope (0.i). However, since this value is so small it seems best to conclude that Amanlta muscaria shows a constant, high level of cadmium which is hardly influenced by the soll concentration.
The results for Amanita rubescens (fig. 4a) are
scattered and difficult to interpret,
but resemble those of A. muscaria.
involutus
Paxillus
(fig. 4b), Hygrophoropsis aurantiaca (fig, 4b), Suillus luteus (fig. 4a) and
Lepista nebularis
(fig. 4c) show an increasing Cd concentration in the mushroom with
increasing soil concentrations.
The data for Lepista nebularis increase sharply at soll
concentrations above 3 mg/kg to mushroom concentrations of about 60 mg/kg. In the case of Zn and Cu, these plots show the expected trend of constant metal concentrations in the mushrooms. This concentration level varies for different species as can also be seen from the average and median values and the standard deviations in table 3. The data for Pb are very scattered and no trends can be discovered.
796
Cd mushr ( m g / k g d r y wt]
Cd mushr ( m g l k g d r y wt)
A
100-
B
100.
oo o 0.1
1
1 Cd soil ( m g / k 9 dry wt)
10
Cd soil ( m g / k g d r y wt)
10
Cd mushr ( m g / k g d r y wt)
C
tO0
o o o
Fig. 4 Relationship between Cd concentrations in the soll and in the mushroom for six species. A solid llne indicates that the slope is significantly different from zero (P>0.01). 4A) Amanlta rubescens (4) and Suillus luteus (A) 4B) Paxillus involutus (o) and Hygrop~oropsis aurantiaca (e) 4C) Amanlta muscarla (o) and Leplsta nebularls (m)
o
o o
o
O.T
Cd soil (mglkg dry wt)
Besides by the various
plots described above,
the relationships
between the metal concen-
tration in the mushroom and the three soll parameters have been investigated the six species mentioned analysis explain
above by (multiple)
linear regression analysis.
it was found that pH and organic matter content as single parameters the variation
of the metal concentration
in the soll proves to be a significant the graphical parameters
representations.
in the mushroom.
for each of
From this do not
The metal concentration
parameter only for Cd, as was expected already from
A multiple linear regression model including all three soil
gives somewhat better results compared to the single parameter model (table 4).
For five species out of six this model accounts Cd concentration
in the mushroom.
when using the multiple
There
is a remarkable
the variation
of the
increase for Amanita rubescens
linear regression model. 0nly in case of Amanlta muscarla,
model does not fit. For the other metals used explains
for 70-80% of the total variability
this
(Cu, Pb, and Zn), none of the regression models
of the metal concentration
in the mushroom.
797
Table 4. Percentage variability of the Cd concentration in the mushroom accounted for by (multiple) linear regression models (A : pH; B : organic matter; C : Cd concentration of the soil; D : pH, organic matter and Cd concentration of the soil).
Amanita muscaria Amanita rubescens Suillus luteus Paxillus involutus Hygrophoropsis aurant. Leplsta nebularls
A
B
C
D
2 3 16 0 0 0
8 0 0 0 19 0
36 20 72 62 83 73
29 78 70 80 82 80
Discussion The results found in our work do not give an explicit answer on the question whether mushrooms
can be used as blolndlcators
figs. 2, 3, and 4 give the impression contamination
pollution.
The data presented
in for
with Cu, Pb, and Zn, while for Cd it depends on the species. Amanita
muscaria for example is not useful irrespective
for heavy-metal
that mushrooms are not suitable as blolndicators
because this species contains high Cd concentrations
of the soll concentration.
the four regions Drenthe, contamination
Beverwijk,
in the surroundings
reflected by the heavy-metal species characteristics
However,
when the data are summarized
for each of
Veluwe, and Budel (table 2) the well-known
of Budel (Cd, Pb, Zn) and Beverwijk
concentrations
in the mushrooms.
and local circumstances
(Cu, Pb) is
Probably the differences
found in one area are put together. When three of the four regions are divided areas and consequently concentrations
as bioindicators from different
the number of samples decreases,
become visible
(table 2). Therefore,
for heavy-metal
in
are averaged when a number of species
large differences
in smaller
in heavy-metal
we conclude that mushrooms
pollution only if sufficient
can be used
(20-40) samples are taken
places in an area large enough to provide samples of at least 8-10 species
in suitable amounts. The levels of metal concentration as reported elsewhere
more or less narrow range, indicating concentrations
in the mushrooms
(1-20). The concentrations
are of the same order of magnitude,
of Cu and Zn in the mushrooms
are in a
that mushrooms are able to regulate their
within certain limits. As Cu and Zn are essential
elements probably the
cell membrane has a transport and/or regulation system for them. On the other hand Cd and Pb are not essential mlcroelements is very effectively involutus.
excluded,
and the differences
Cd is accumulated
in uptake are remarkable:
up to very high levels except
Our results with the four metals Investigated
(16) with Collybla peronata
and exclusion.
The overall data
behaviour
is found for Paxillus
involutus
of Cd occurs with this species. Tyler reports a deviating behaviour
Amanita rubescens
having relatively low concentration
No difference must be concluded
between saprophytic
~nd mycorrhizal
that the accumulation
species.
This is illustrated
as
for
ratios for Cd. This is not confirmed
by our results as we find relatively high concentration
individual
rubescens.
(fig. 2) show the same trends of accumulation
In the case of Cd, a deviating
no accumulation
do agree with the work of Tyler
(Bolt. ex Fr.) Sing. and Amanlta
(fig. I) and the data for the six species
where Pb
for Paxillus
ratios for this species.
forming species was observed.
of Cd depends only on the characteristics by the deviating
behaviour of Paxillus
So it of
involutus
798
which can only be explained
by assuming an exclusion mechanism
Our final conclusion with respect to the accumulation
by Tyler is that, at least for the four metals investigated species also at an extended The heavy-metal organic-matter
for Cd in this species.
and exclusion patterns reported here~ it is valid for most
range of concentrations.
concentrations
in the mushroom are hardly affected
by pH and
content of the soil. This was rather unexpected as these parameters
generally supposed
are
to influence mobility and availability
of heavy metals in the soil. It
can be due to the low pH values of all soils investigated
that in this pH range no effect
on the solubility and consequently observed.
Considering
on the uptake of heavy metals by mushrooms
the organic-matter
composition of the organic matter differs
strongly between
litter, fermentation,
and mineral layers of the soil. The influence on mobility and availability depends on certain humic fractions total organic-matter composition~
was
content it must be pointed out first that the
of the organic matter
content was determined
humus,
of heavy metals
(27). The fact that only the
without further information on the
probably made that no effect was found of the organic matter content on the
uptake of heavy metals by mushrooms. Brunnert and Zadrazil
(24) concluded
from experimental
uptake studies that cadmium and
zinc compete for being resorbed by the fruiting bodies. However,
Seeger (25) concluded
from other work that there is no correlation between cadmium and zinc contents growing mushrooms, contradictory
while also our data do not provide such a correlation.
findings
illustrate
that a relationship
with environmental
exist without being found in field studies due to too many interfering
in wild
These parameters
can
factors.
Acknowledgements We would like to thank Mr. E. Koopman for his contribution to the heavy-metal analysis and Dr. P. Doelman, Dr. H.J.P. Eijsackers and Dr. R.A. Prins for their helpful comments in this project.
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799
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R. Bargagll and F. Baldi (1984), Chemosphere 13, 1059-1071 G. Santoprete and G. Innocenti (1984), Micologia Italiana 13, 11-28 H. Brunnert and F. Zadrazil (1980), Eur. J. Appl. Microbio~?. Biotechnol. i0, 145-154 H. Brunnert and F. Zadrazil (1981), Eur. J. Appl. Microbiol. Biotechnol. 12, 179-182 H. Brunnert and F. Zadrazil (1983), Eur. J. Appl. Microbiol. Biotechnol. 17, 358-364 H. Brunnert and F. Zadrazil (1985), Angew. Botanik 59, 469-477 R. Seeger (1982), Dtsch. Apoth. Ztg. 122, 1835-1844 N. Alvey, N. Galway and P. Lane (1982), An introduction to GENSTAT~ Academic Press, London 27. K.A. Daum & L.W. Newland (1982), Complexing effects on behaviour of some metals. In: O. Hutzinger (ed.), The handbook of environmental chemistry, volume 2, part B, Springer Verlag, New York, p. 129. (Received
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29 J u n e
1987)