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Use of Polytrichum formosum (moss) as a passive biomonitor for heavy metal pollution (cadmium, copper, lead and zinc)
The Science of the Total Environment, 86 (1989)289-294 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
USE OF POLYTRICHUM
FORMOSUM
289
(MOSS) AS A P A S S I V E
BIOMONITOR FOR HEAVY METAL POLLUTION (CADMIUM, C O P P E R , L E A D AND ZINC)
BERND MARKERT and VERA WECKERT Department of Systems Research, University of Osnabri~ck, 4500 Osnabrt~ck (F.R.G.) (Received March 5th, 1989; accepted April 28th, 1989)
ABSTRACT
After sampling over regular intervals from 1985to 1987the heavy metals Cd, Cu, Pb and Zn were quantitatively determinedby atomic emission spectrometry/inductivelycoupled plasma in aboveground parts of the moss Polytrichum formosum (Hedw.). All metals present a typical summerwinter oscillation (seasonal variation), which is much greater than the "inter-stand" variation of Polytrichum formosum within the forest ecosystem under investigation. To obtain comparable results on a regional or global scale it is suggested to collect all samples of Polytrichurn formosum for biomonitoring purposes in the last week of September.
MOSSES AS INDICATORS OF HEAVY METAL POLLUTION After a quantitative assessment of worldwide contamination of air, water and soils by trace metals (Nriagu and Pacyna, 1988) a significant contamination of freshwater resources and an accelerating accumulation of toxic metals in the h u m a n food chain was observed. The steadily increasing pollution of the environment, caused by inorganic and organic substances introduced by man, requires pe r m a ne nt global monitoring of the enrichment of potential pollutants and the reporting of adverse biological effects on ecosystems (Goodmann and Roberts, 1971; Little and Martin, 1974; Manning and Feder, 1980; Lieth and Markert, 1985; Wolff and Peel, 1985; M a r k e r t and Lieth, 1987; Nriagu and Pacyna, 1988). Analysis of trace metal status in ice or peat cores (Lee and Tallis, 1973; B out r on and Lorius, 1979; Wolff and Peel, 1985) can only be used for demonstrating the increase in heavy metal concentrations during the last centuries. F o r monitoring the heavy metal status of our environment, mosses are of special interest (Yeaple, 1972; M anni ng and Feder, 1980; Steubing and Jaeger, 1982). Mosses comprise the simplest forms of terrestrial plants and differ from other plants in t h a t the dominant phase of the life cycle is represented by the gametophyte generation. Consequently, the evolution of structural complexity has been partly limited by the dependence of sexual reproduction in free water for the dispersal of the motile antherozoids (Streeter, 1970). Mosses are also
0048-9697/89/$03.50
© 1989 Elsevier Science Publishers B.V.
290 characterized by having excellent accumulation properties for heavy metals. With regard to our previous work (Markert, 1987; Markert and Jayasekera, 1987; Lieth and Markert, 1988a, b; Markert and Weckert, 1989), we have undertaken a long-term investigation of Polytrichum formosum (Hedw.) to provide an insight into the heavy metal distribution in the plant over a 2 year period and to establish baseline values in order to use Polytrichum formosum as an indicator for heavy metal pollution. To obtain comparable results it is essential to observe the natural fluctuations of the elemental composition of the moss to obtain a suitable sampling period. Analytical data for mosses growing in a highly polluted area should be compared with those from mosses growing in relatively unpolluted areas (Markert and Lieth, 1987). For quantification of the results obtained from moss analysis, the data should finally be compared with data from air dust analysis. After this procedure, it can be decided if Polytrichum formosum is suitable as a passive biomonitor. In this article, only the first step, the observation of the natural fluctuations of heavy metals within Polytrichum formosum, is reported. REPRESENTATIVE SAMPLINGAND EXPERIMENTALDESIGN The moss samples have been taken at weekly intervals since autumn 1985. In this report we discuss the analyses for the first 2 years of the investigation. The sampling area is located in a 30-40-year-old spruce forest (Hoerner Bruch near Osnabr~ck, F.R.G.) on sandy loam soil. All samples were taken from one stand of Polytrichum formosum approximately 1 m in diameter. On each sampling date, about 50 plants were taken distributed over the whole crosssection. Only above-ground parts were taken for analysis. The collectors wore plastic gloves to avoid contamination. To inVestigate the biological variation of elemental concentrations in the whole spruce forest (inter-stand variation), 50 plants of nine different stands of Polytrichum formosum were taken from an area of 1 km 2 and were analyzed separately. All plants were collected in plastic bags and brought immediately to the laboratory to avoid contamination. The unwashed samples were dried under reduced pressure (15 Torr) for 48 h at 50°C. Pre-dried sample (0.200 + 0.001 g) was weighed into a clean test tube and 4 ml nitric acid (AR 70% w/w) was added. The tubes were left for 3 days at room temperature and shaken occasionally. After heating at 50°C overnight, 1.0 ml perchloric acid (AR 60% w/w) was added to the cooled samples. The test tubes were placed in an aluminium heating block and the temperature program described by Thompson and Wood (1982) was activated. When the cycle was complete, the residue of each tube was dried. After cooling, 2.0 ml hydrochloric acid (5 M A R ) was added to each tube. The tubes were left for 1 h at 60°C. After cooling again, 8.0ml distilled water was added and each was mixed using a vortex mixer. After decanting into polystyrene tubes, solutions were equilibrated at 20°C and elements determined by an atomic emission spectrometer with an inductively coupled plasma (Applied Research Laboratory, ARL 34000 C). A description of the spectrometer and the standard conditions are
291
given by Thompson et al. (1987). Quality control was assured by analysis of duplicate samples, blanks and standard reference materials after Thompson and Walsh (1983). The results obtained from the analysis of three plant reference materials are given in Table 1. SEASONAL FLUCTUATION OF HEAVY METALS
Figure 1 presents the concentrations of Cd and Pb from autumn 1985 to autumn 1987. The two elements are not essential for plants and are toxic in high concentrations. For lead we found a typical summer-winter oscillation (Markert and Weckert, 1989). Polytrichumformosurn possesses a differentiated internal conducting system so that water uptake and transport is comparable to that of higher plants. The presence of a cuticle-like layer impedes the uptake of water via the leaf. A decrease in the concentration of Pb in the spring is related to the higher productivity of Polytrichum formosum during this period, accompanied by dilution of the organism by growth (Callaghan et al., 1978). An increase in the Pb concentration from the end of September to the middle of February is explained by lower biomass productivity compared with the spring months and a higher transpiration rate. The concentration maximum for Pb was lower in the years 1986/1987 than in the years 1985/1986. Compared with TABLE 1 A n a l y t i c a l r e s u l t s for p l a n t r e f e r e n c e m a t e r i a l s Standard a
Element
Test tube
Test tube
x
Reference value
Deviation from r e f e r e n c e value
(%)
N B S 1572
H R M 12
H R M 14
Cd Cu Pb Zn
No. 5037 ND b 14.73 12.02 27.46
No. 5081 ND 14.79 11.98 26.44
14.76 12.00 26.95
16.5 13.3 29
10.55 9.75 7.07
Cd Cu Pb Zn
No. 5001 ND 10.35 5.77 48.60
No. 5032 ND 10.31 8.73 52.14
10.33 7.25 50.37
9.60 8.10 52.00
7.59 10.45 3.13
Cd Cu Pb Zn
No. 5012 0.20 6.7 8.31 35.14
No. 5058 0.20 7.16 8.88 34.90
0.20 6.93 8.59 35.02
0.18 6.30 9.00 35.00
11.1 9.97 4.51 0.06
(0.03) c
a N B S 1572 = C i t r u s Leaves; H R M 12 a n d H R M 14 = i n - h o u s e s t a n d a r d s . b N o t detected. e( ) = N o t certified.
292 Cd (mMIk9)
Pb
{mM/kQ) Pb
0,4S
o.o'~
.---
0.45
0,4
0.4
0.35
0.35
i
0.3 0.25 O.2
......ill
0.15
i\.
,...
........
\
°"" °'"'" i
i
~
i
2
i
3.
1085
4
o--o
0.035 0.03
0.25
0.025
0.2
0.02 0.015
.>.
o,oi
0.05
0.005 IJIIF
i
1
Cd
0.045
'
,°-° "~...'; " ooo,
i
2
1986
.
°--o
0.3
0.1
v\
"'."\ ,,:,"~..'(: i ............ .,A.
A
4
.
Pb
0.04
0.15
0.1 0.06
C0 (mMIKg)
Pb
(mMIk 0)
*~3,serH
3
ABCOE
198~"
Fig. 1. Concentrations of Pb and Cd in Polytrichumformosum (above-ground parts) collected from autumn 1985 to autumn 1987. 1-4 indicate the first (second, third, fourth) quarter of the year (left). 1-9 indicate the biological inter-stand variations of element concentrations between different stands of Polytrichum forrnosum in the same forest. A-E indicate the analytical variance (right) (Markert and Weckert, 1989).
the distribution pattern of Pb, Cd shows smaller variations during the growing season. The distribution pattern of two essential elements (Cu and Zn) is presented in Fig. 2. Considering the Cu and Zn distribution over 2 years they are very similar to the distribution patterns of Pb and Cd, respectively. Copper exhibits large fluctuations during the growing season, with the highest concentration Zn
Cu Cu
(mMIkg)
*--,
(mMIkg)
0.55 O:S 0.45
0.4 0.38
;,."
•
0.3
I/
o"
...°.o,~,
.
~'~,/ ..... y
5.0 4.5
4.0
0.48
4.0
3.5
0.4
3.5
3.0
0,35
3.0
2.5
0.3
2.5
2.0
0.25
2.0
I.o
°:.~o,,/\o
(mMIk 9)
O.S
1.5
0,2 %
0,15
e--o
Z, o--o
4.5
1,5
0.2
Cu
0.55
i.,.l,,,"
0.25
Zn
Cu I (mM/kg) ;
5.0
o 1.0
O.lS o-o~0 o
o.5
0.! I 4. 1985
I 1
I 2
I 0
1986
& 4
I
I
1
2
0.5
o.~
~ 3
' ........ ,2~,sl,,,
,,toe
1987
Fig. 2. Concentrations of Cu and Zn in Polytrichumformosum (above-ground parts) collected from autumn 1985 to autumn 1987. 1-4 indicate the first (second, third, fourth) quarter of the year (left). 1-9 indicate the biological inter-stand variations of element concentrations between different stands of Polytrichurn forrnosum in the same forest. A-E indicate the analytical variance (right) (Markert and Weckert, 1989).
293 p e a k in winter; Zn exhibits small v a r i a t i o n s over a 1 y e a r period. In addition, the i n t e r - s t a n d v a r i a t i o n s i l l u s t r a t e d in Figs 1 a n d 2 are m u c h smaller t h a n the s e a s o n a l v a r i a t i o n s in m e t a l c o n t e n t s of Polytrichum forrnosum. C o n s i d e r i n g the s e a s o n a l v a r i a t i o n s in e l e m e n t c o n c e n t r a t i o n s of the moss u n d e r i n v e s t i g a t i o n , we s u g g e s t c o l l e c t i o n of all samples for b i o m o n i t o r i n g p u r p o s e s d u r i n g the last week of S e p t e m b e r in o r d e r to o b t a i n c o m p a r a b l e results from different s t a n d s of Polytrichum formosum. ACKNOWLEDGEMENTS We t h a n k Dr K.G. B e r n h a r d t ( U n i v e r s i t y of Osnabrfick) for classification of the mosses, the staff of the Applied G e o c h e m i s t r y R e s e a r c h Group, U n i v e r s i t y of L o n d o n (Head: Prof. Dr I. T h o r n t o n ) , for t h e i r a s s i s t a n c e d u r i n g c h e m i c a l analyses, M r Kies a n d M r S t a e n n e r ( U n i v e r s i t y of Osnabriick) for p r e p a r i n g the figures, Prof. Dr H. L i e t h a n d Dr R. E n g e l k e ( U n i v e r s i t y of Osnabrfick) for fruitful discussions d u r i n g p r e p a r a t i o n of the m a n u s c r i p t , and the Gesamtv e r b a n d of the G e r m a n R u h r k o h l e AG, Essen, for t h e i r financial support.
REFERENCES Boutron, C. and C. Lorius, 1979. Trace metals in Antarctic snows since 1914. Nature, 277: 551-554. Callaghan, T.V., N.J. Collins and C.H. Callaghan, 1978. Photosynthesis, growth and reproduction of Hylocomium splendens and Polytrichumcommunein Swedish Lapland. Oikos, 31: 73-88. Goodmann, G.T. and T.M. Roberts, 1971. Plants and soils as indicators of metals in the air. Nature, 231: 287-292. Lee, J.A. and J.H. Tallis, 1973. Regional and historical aspects of lead pollution in Britain, Nature, 245: 216-218. Lieth, H. and B. Markert, 1985. Concentration cadasters of chemical elements in contrasting ecosystems. Naturwissenschaften, 72: 322-324. Lieth, H. and B. Markert, 1988a. Establishment of element concentration cadasters in different vegetation zones of the world. Biol. Int., 16: 7-11. Lieth, H. and B. Markert, 1988b. Aufstellung und Auswertung oekosystemarer Element-Konzentrations-Kataster. Springer, Berlin, Heidelberg, New York, 213 pp. Little, P. and M.H. Martin, 1974. Biological monitoring of heavy metal pollution. Environ. Pollut., 6: 1-19. Manning, W.J. and W.A. Feder, 1980. Biomonitoring Air Pollution with Plants. Applied Science Publishers, London, 142 pp. Markert, B., 1987. The pattern of distribution of lanthanide elements in soils and plants. Phytochemistry, 26: 3167-3170. Markert, B. and R. Jayasekera, 1987. Elemental composition of different plant species. J. Plant Nutr., 10: 783-794. Markert, B. and H. Lieth, 1987. Element concentration cadasters in a Swedish biotope. Reference standard for inorganic environmental chemistry. Fresenius Z. Anal. Chem., 326: 716-718. Markert, B. and V. Weckert, 1989. Oscillations of element concentrations during the growing season of Polytrichum forrnosum (Hedw.). Water, Air Soil Pollut., 43: 177-189. Nriagu, J.O. and J.M. Pacyna, 1988. Quantitative assessment of worldwide contamination of air, water and soils by trace metals. Nature, 333: 134-139. Steubing, L. and H. J. Jaeger (Eds), 1982. Monitoring of Air Pollutants by Plants; Methods and Problems. W. Junk, The Hague, Boston, London, 161 pp.
294 Streeter, D.T., 1970. Bryophyte ecology. Sci. Prog. (Oxford), 58: 419-434. Thompson, M. and S. Wood, 1982. Atomic absorption methods in applied geochemistry. In: J.E. Cantle (Ed.), Techniques and Instrumentation in Analytical Chemistry. No. 5, Atomic Absorption Spectrophotochemistry. Elsevier, Amsterdam, pp. 261-284. Thompson, M. and J.N. Walsh, 1983. A Handbook of Inductively Coupled Plasma Spectrometry. Blackie, Glasgow, London, 273 pp. Thompson, M., M.H. Ramsay, B.J. Coles and Chong Ming Du, 1987. Correction of matrix effects in inductively coupled plasma spectrometry by interactive power adjustment. J. Anal. At. Spectrom., 2: 185-188. Wolff, E.W. and D.A. Peel, 1985. The record of global pollution in polar snow and ice. Nature, 313: 535-540. Yeaple, D.S., 1972. Mercury in Bryophytes (Moss). Nature, 235: 229-230.
USE OF POLYTRICHUM
FORMOSUM
289
(MOSS) AS A P A S S I V E
BIOMONITOR FOR HEAVY METAL POLLUTION (CADMIUM, C O P P E R , L E A D AND ZINC)
BERND MARKERT and VERA WECKERT Department of Systems Research, University of Osnabri~ck, 4500 Osnabrt~ck (F.R.G.) (Received March 5th, 1989; accepted April 28th, 1989)
ABSTRACT
After sampling over regular intervals from 1985to 1987the heavy metals Cd, Cu, Pb and Zn were quantitatively determinedby atomic emission spectrometry/inductivelycoupled plasma in aboveground parts of the moss Polytrichum formosum (Hedw.). All metals present a typical summerwinter oscillation (seasonal variation), which is much greater than the "inter-stand" variation of Polytrichum formosum within the forest ecosystem under investigation. To obtain comparable results on a regional or global scale it is suggested to collect all samples of Polytrichurn formosum for biomonitoring purposes in the last week of September.
MOSSES AS INDICATORS OF HEAVY METAL POLLUTION After a quantitative assessment of worldwide contamination of air, water and soils by trace metals (Nriagu and Pacyna, 1988) a significant contamination of freshwater resources and an accelerating accumulation of toxic metals in the h u m a n food chain was observed. The steadily increasing pollution of the environment, caused by inorganic and organic substances introduced by man, requires pe r m a ne nt global monitoring of the enrichment of potential pollutants and the reporting of adverse biological effects on ecosystems (Goodmann and Roberts, 1971; Little and Martin, 1974; Manning and Feder, 1980; Lieth and Markert, 1985; Wolff and Peel, 1985; M a r k e r t and Lieth, 1987; Nriagu and Pacyna, 1988). Analysis of trace metal status in ice or peat cores (Lee and Tallis, 1973; B out r on and Lorius, 1979; Wolff and Peel, 1985) can only be used for demonstrating the increase in heavy metal concentrations during the last centuries. F o r monitoring the heavy metal status of our environment, mosses are of special interest (Yeaple, 1972; M anni ng and Feder, 1980; Steubing and Jaeger, 1982). Mosses comprise the simplest forms of terrestrial plants and differ from other plants in t h a t the dominant phase of the life cycle is represented by the gametophyte generation. Consequently, the evolution of structural complexity has been partly limited by the dependence of sexual reproduction in free water for the dispersal of the motile antherozoids (Streeter, 1970). Mosses are also
0048-9697/89/$03.50
© 1989 Elsevier Science Publishers B.V.
290 characterized by having excellent accumulation properties for heavy metals. With regard to our previous work (Markert, 1987; Markert and Jayasekera, 1987; Lieth and Markert, 1988a, b; Markert and Weckert, 1989), we have undertaken a long-term investigation of Polytrichum formosum (Hedw.) to provide an insight into the heavy metal distribution in the plant over a 2 year period and to establish baseline values in order to use Polytrichum formosum as an indicator for heavy metal pollution. To obtain comparable results it is essential to observe the natural fluctuations of the elemental composition of the moss to obtain a suitable sampling period. Analytical data for mosses growing in a highly polluted area should be compared with those from mosses growing in relatively unpolluted areas (Markert and Lieth, 1987). For quantification of the results obtained from moss analysis, the data should finally be compared with data from air dust analysis. After this procedure, it can be decided if Polytrichum formosum is suitable as a passive biomonitor. In this article, only the first step, the observation of the natural fluctuations of heavy metals within Polytrichum formosum, is reported. REPRESENTATIVE SAMPLINGAND EXPERIMENTALDESIGN The moss samples have been taken at weekly intervals since autumn 1985. In this report we discuss the analyses for the first 2 years of the investigation. The sampling area is located in a 30-40-year-old spruce forest (Hoerner Bruch near Osnabr~ck, F.R.G.) on sandy loam soil. All samples were taken from one stand of Polytrichum formosum approximately 1 m in diameter. On each sampling date, about 50 plants were taken distributed over the whole crosssection. Only above-ground parts were taken for analysis. The collectors wore plastic gloves to avoid contamination. To inVestigate the biological variation of elemental concentrations in the whole spruce forest (inter-stand variation), 50 plants of nine different stands of Polytrichum formosum were taken from an area of 1 km 2 and were analyzed separately. All plants were collected in plastic bags and brought immediately to the laboratory to avoid contamination. The unwashed samples were dried under reduced pressure (15 Torr) for 48 h at 50°C. Pre-dried sample (0.200 + 0.001 g) was weighed into a clean test tube and 4 ml nitric acid (AR 70% w/w) was added. The tubes were left for 3 days at room temperature and shaken occasionally. After heating at 50°C overnight, 1.0 ml perchloric acid (AR 60% w/w) was added to the cooled samples. The test tubes were placed in an aluminium heating block and the temperature program described by Thompson and Wood (1982) was activated. When the cycle was complete, the residue of each tube was dried. After cooling, 2.0 ml hydrochloric acid (5 M A R ) was added to each tube. The tubes were left for 1 h at 60°C. After cooling again, 8.0ml distilled water was added and each was mixed using a vortex mixer. After decanting into polystyrene tubes, solutions were equilibrated at 20°C and elements determined by an atomic emission spectrometer with an inductively coupled plasma (Applied Research Laboratory, ARL 34000 C). A description of the spectrometer and the standard conditions are
291
given by Thompson et al. (1987). Quality control was assured by analysis of duplicate samples, blanks and standard reference materials after Thompson and Walsh (1983). The results obtained from the analysis of three plant reference materials are given in Table 1. SEASONAL FLUCTUATION OF HEAVY METALS
Figure 1 presents the concentrations of Cd and Pb from autumn 1985 to autumn 1987. The two elements are not essential for plants and are toxic in high concentrations. For lead we found a typical summer-winter oscillation (Markert and Weckert, 1989). Polytrichumformosurn possesses a differentiated internal conducting system so that water uptake and transport is comparable to that of higher plants. The presence of a cuticle-like layer impedes the uptake of water via the leaf. A decrease in the concentration of Pb in the spring is related to the higher productivity of Polytrichum formosum during this period, accompanied by dilution of the organism by growth (Callaghan et al., 1978). An increase in the Pb concentration from the end of September to the middle of February is explained by lower biomass productivity compared with the spring months and a higher transpiration rate. The concentration maximum for Pb was lower in the years 1986/1987 than in the years 1985/1986. Compared with TABLE 1 A n a l y t i c a l r e s u l t s for p l a n t r e f e r e n c e m a t e r i a l s Standard a
Element
Test tube
Test tube
x
Reference value
Deviation from r e f e r e n c e value
(%)
N B S 1572
H R M 12
H R M 14
Cd Cu Pb Zn
No. 5037 ND b 14.73 12.02 27.46
No. 5081 ND 14.79 11.98 26.44
14.76 12.00 26.95
16.5 13.3 29
10.55 9.75 7.07
Cd Cu Pb Zn
No. 5001 ND 10.35 5.77 48.60
No. 5032 ND 10.31 8.73 52.14
10.33 7.25 50.37
9.60 8.10 52.00
7.59 10.45 3.13
Cd Cu Pb Zn
No. 5012 0.20 6.7 8.31 35.14
No. 5058 0.20 7.16 8.88 34.90
0.20 6.93 8.59 35.02
0.18 6.30 9.00 35.00
11.1 9.97 4.51 0.06
(0.03) c
a N B S 1572 = C i t r u s Leaves; H R M 12 a n d H R M 14 = i n - h o u s e s t a n d a r d s . b N o t detected. e( ) = N o t certified.
292 Cd (mMIk9)
Pb
{mM/kQ) Pb
0,4S
o.o'~
.---
0.45
0,4
0.4
0.35
0.35
i
0.3 0.25 O.2
......ill
0.15
i\.
,...
........
\
°"" °'"'" i
i
~
i
2
i
3.
1085
4
o--o
0.035 0.03
0.25
0.025
0.2
0.02 0.015
.>.
o,oi
0.05
0.005 IJIIF
i
1
Cd
0.045
'
,°-° "~...'; " ooo,
i
2
1986
.
°--o
0.3
0.1
v\
"'."\ ,,:,"~..'(: i ............ .,A.
A
4
.
Pb
0.04
0.15
0.1 0.06
C0 (mMIKg)
Pb
(mMIk 0)
*~3,serH
3
ABCOE
198~"
Fig. 1. Concentrations of Pb and Cd in Polytrichumformosum (above-ground parts) collected from autumn 1985 to autumn 1987. 1-4 indicate the first (second, third, fourth) quarter of the year (left). 1-9 indicate the biological inter-stand variations of element concentrations between different stands of Polytrichum forrnosum in the same forest. A-E indicate the analytical variance (right) (Markert and Weckert, 1989).
the distribution pattern of Pb, Cd shows smaller variations during the growing season. The distribution pattern of two essential elements (Cu and Zn) is presented in Fig. 2. Considering the Cu and Zn distribution over 2 years they are very similar to the distribution patterns of Pb and Cd, respectively. Copper exhibits large fluctuations during the growing season, with the highest concentration Zn
Cu Cu
(mMIkg)
*--,
(mMIkg)
0.55 O:S 0.45
0.4 0.38
;,."
•
0.3
I/
o"
...°.o,~,
.
~'~,/ ..... y
5.0 4.5
4.0
0.48
4.0
3.5
0.4
3.5
3.0
0,35
3.0
2.5
0.3
2.5
2.0
0.25
2.0
I.o
°:.~o,,/\o
(mMIk 9)
O.S
1.5
0,2 %
0,15
e--o
Z, o--o
4.5
1,5
0.2
Cu
0.55
i.,.l,,,"
0.25
Zn
Cu I (mM/kg) ;
5.0
o 1.0
O.lS o-o~0 o
o.5
0.! I 4. 1985
I 1
I 2
I 0
1986
& 4
I
I
1
2
0.5
o.~
~ 3
' ........ ,2~,sl,,,
,,toe
1987
Fig. 2. Concentrations of Cu and Zn in Polytrichumformosum (above-ground parts) collected from autumn 1985 to autumn 1987. 1-4 indicate the first (second, third, fourth) quarter of the year (left). 1-9 indicate the biological inter-stand variations of element concentrations between different stands of Polytrichurn forrnosum in the same forest. A-E indicate the analytical variance (right) (Markert and Weckert, 1989).
293 p e a k in winter; Zn exhibits small v a r i a t i o n s over a 1 y e a r period. In addition, the i n t e r - s t a n d v a r i a t i o n s i l l u s t r a t e d in Figs 1 a n d 2 are m u c h smaller t h a n the s e a s o n a l v a r i a t i o n s in m e t a l c o n t e n t s of Polytrichum forrnosum. C o n s i d e r i n g the s e a s o n a l v a r i a t i o n s in e l e m e n t c o n c e n t r a t i o n s of the moss u n d e r i n v e s t i g a t i o n , we s u g g e s t c o l l e c t i o n of all samples for b i o m o n i t o r i n g p u r p o s e s d u r i n g the last week of S e p t e m b e r in o r d e r to o b t a i n c o m p a r a b l e results from different s t a n d s of Polytrichum formosum. ACKNOWLEDGEMENTS We t h a n k Dr K.G. B e r n h a r d t ( U n i v e r s i t y of Osnabrfick) for classification of the mosses, the staff of the Applied G e o c h e m i s t r y R e s e a r c h Group, U n i v e r s i t y of L o n d o n (Head: Prof. Dr I. T h o r n t o n ) , for t h e i r a s s i s t a n c e d u r i n g c h e m i c a l analyses, M r Kies a n d M r S t a e n n e r ( U n i v e r s i t y of Osnabriick) for p r e p a r i n g the figures, Prof. Dr H. L i e t h a n d Dr R. E n g e l k e ( U n i v e r s i t y of Osnabrfick) for fruitful discussions d u r i n g p r e p a r a t i o n of the m a n u s c r i p t , and the Gesamtv e r b a n d of the G e r m a n R u h r k o h l e AG, Essen, for t h e i r financial support.
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