Heavy metals in mushrooms and their relationship with soil characteristics

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...

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Chemosphere, Vol.17, No.4, Printed in Great Britain




0045-6535/88 $3.00 Pergamon Press plc



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


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







of wild growing mushrooms with easily determinable

such as heavy-metal



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


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,


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


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,




(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


correction have been used. Organic-matter


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.


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


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).




n 19

Diever Steenwijk Havelte Dwingeloo Beverwijk Veluwe

54.8 3.5 3.3 9.5 2.4


35 Lunteren Hoge Veluwe Wageningen Arnhem


3.3 8 7 2 2




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


3.3 3.2 3.3 12.0 7.0

57.0 1.2 2.6 2.1 2.9



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


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.


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



14 s a m p l e s t h e r a n g e s ,


o f t h e mushroom c o n c e n t r a t i o n s


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




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


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


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



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


involutus and the lowest for Hy~rophoropsis aurantlaca (which has the highest value of 1233 mg/kg!).

Cr 1000





50O 2OO 1 O0

2O 50 ~ 10


5 2




T -j



0.1 0115

O.O2 1101 0.005 0,002


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


Cr Cu





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





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




1° 7




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


C 1.


.{ 10 .o





• °°%°. :



: °.




~ : : ..






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.



(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.


Cd mushr ( m g / k g d r y wt]

Cd mushr ( m g l k g d r y wt)





oo o 0.1


1 Cd soil ( m g / k 9 dry wt)


Cd soil ( m g / k g d r y wt)


Cd mushr ( m g / k g d r y wt)



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



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


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


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


(Cu, Pb, and Zn), none of the regression models

of the metal concentration

in the mushroom.


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





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


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


in the surroundings

reflected by the heavy-metal species characteristics


when the data are summarized

for each of

Veluwe, and Budel (table 2) the well-known

of Budel (Cd, Pb, Zn) and Beverwijk


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


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.


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


is found for Paxillus


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


This is illustrated



ratios for Cd. This is not confirmed

by our results as we find relatively high concentration



(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



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.


in the mushroom are hardly affected

by pH and

content of the soil. This was rather unexpected as these parameters

generally supposed


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.


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~


content it must be pointed out first that the

of the organic matter

content was determined


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.



that a relationship

with environmental

exist without being found in field studies due to too many interfering

in wild

These parameters



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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29 J u n e