DETERMINATION OF CURRENT AND HISTORIC LOADS OF
ATMOSPHERIC DEPOSITION IN THE CZECH REPUBLIC USING ANALYSES OF MOSS AND FOREST
FLOOR HUMUS
Julie Sucharová, Ivan Suchara* (*Research Institute of Ornamental Gardening, CZ 252 43 Průhonice, Czech Republic; suchara@vuoz.cz)
Abstract
The concentration of fourteen elements (Al, As, Cd.
Co, Cr, Cu, Fe, Hg, Mo, Ni, Pb, S, V, Zn) was measured in moss and forest floor
humus samples to determine the current and historic large-scale atmospheric
loads in the Czech Republic. Multielement analyses of moss and humus provide a
credible, quick and relatively cheap means of identifying the relative and
absolute actual loads and the relative historic atmospheric loads in large
territories. In order to test the biomonitoring techniques on a fine scale,
moss and humus matrices were taken in a dense grid of sampling points near the
city of Příbram - a multielemental source of pollution. The impacts of
mining and smelting polymetallic ores, recycling Pb wastes and mining uranium
ore were reliably determined, and historic and current contaminations of 36
elements in hot spots were located in the investigated landscape segment. The
obtained results justify us in recommending moss and humus biomonitoring for
wider use.
Introduction
Large-scale measuring of atmospheric
deposition levels at stations is a time-consuming and expensive activity.
Analyses of elements in widely used natural matrices may provide an alternative
way, as the element content in them correlates significantly with the local
atmospheric deposition level. We decided to use analyses of moss and forest
floor humus, for large-scale biomonitoring of current and historic atmospheric
loads throughout the Czech Republic (50˚N; 15˚E, abbreviated ´the CZ´
in the following text) and for a fine-scale biomonitoring in a landscape
segment near a local multielement pollution source.
a) Mosses –
bioindicators of current atmospheric deposition loads
Mosses
do not have genuine roots and the inflow of water and elements from the ground
substrate is slow enough to be negligible, mainly in a group of terrestrial
so-called ´feather mosses´. The surface of the above-ground parts of these
mosses adsorbs crucial if not entire amounts of nutrients from atmospheric
deposition. No wonder that the content of elements in mosses correlates
significantly with the current atmospheric deposition levels in a given area
(Rühling and Tyler 1970, 1971). It is even easy to calculate the absolute
atmospheric deposition levels of elements at a given place from the
concentration of elements in moss samples, moss production data and
coefficients of element uptake
b) Forest floor humus
– an indicator of historic loads
Analyses of individual layers of
known age cored from peat bogs, glacials or tills have been used for
determination of historic levels of element deposition (e.g., Steinnes 1997,
Weiss et al. 1997). Unfortunately, these materials are not distributed in
sufficient abundance for large-scale monitoring or screening in central Europe.
To solve this problem, we tested forest floor humus of coniferous forests as an
alternative matrix with a long memory. Exclusively the H horizon of forest
floor was used due to its microbiological resistance. The organic H and deeper
soil A horizon are mixed through natural or man-made processes. Hence selective
digestion of organic matter in humus samples was needed to eliminate geogenic
influence and to determine the retrospective atmospheric deposition loads.
Methodology
a) Moss monitoring
Moss
monitoring was carried out in the CZ (78,864 km2) in 1991 and 1995
in the framework of the European moss monitoring programmes (Rühling 1994,
Rühling and Steinnes 1998). In the latter monitoring programme, 196 moss
samples were taken in a grid of sampling points of 20x20 km and the methods
used followed the instructions of the international programmes. Preferably Pleurozium schreberi moss was taken. The
concentration of 14 elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mo, Ni, Pb, S, V,
Zn) in two-year-old moss segments (1994-1995) was measured by means of the
ICP-OES technique. Standard reference materials, moss laboratory standards and
recovery tests were used to check the digestion and analytical processes.
b) Humus monitoring
In
contrast to moss monitoring, there was no available standardised method for
taking and analysing forest floor humus for large scale monitoring. A technique
for sampling and analysing forest floor humus was therefore developed and
tested in the CZ in 1993-1995. Retrospective historic loads of the 14 elements were
determined throughout the CZ. About 200 samples of humic substances exclusively
from H horizons were taken in mull or moder forest floors of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) or mixed forest stands,
usually 60-90 years old, in 1995. The mineral (´ash´) content was controlled
through the loss-on-ignition technique and its content exceeding of 30% was
avoided in taken samples. Concentrations of 14 elements (see moss monitoring
above) in organic matter were measured in samples digested through HNO3
+ H2O2 using an ICP-OES instrument after centrifugation
off undissolved Si and Si-gel. Concentrations of elements were related to the
so-called ash-free samples. For more details see Sucharová and Suchara 1998c.
c) Fine-scale
monitoring
The
city of Příbram (49˚41´N; 14˚ 00´E), situated in a wooded
landscape, was chosen as a model of a multiple source of current and historic
air pollution. Polymetallic Ag, Pb, Zn ores with many minority elements were
extracted near the city and processed in a local smelting works as recently as
the 1970s. Now the smelter located close to the abandoned mine recycles Pb
wastes and metals from electronic components. From 1949-1992 uranium ore
(uraninite) was extracted from pits on the opposite side of the city.
In
1999, samples of coniferous forest floor humus and moss (Pleurozium schreberi) were taken along linear transects 15 km in
length running radially from the smelter chimney. The transects were 30º apart,
and the distance between the sampling points at the transects was 2000 m.
Analyses of 36 elements (see Table 2) were carried out by means of the ICP-MS
technique. The distribution of current and historic loads of these elements was
determined in classed post maps and isoline maps.
Results
a) Large-scale moss
monitoring
Selected characteristics of a set of analysed moss samples from the CZ are
shown in Table 1. Moss analyses showed very high current atmospheric deposition
loads of Al, As, Co, Cr, Hg, Mo, Ni, S, V and Zn in the lignite basin and its
surroundings in the northwestern part of the CZ. The chemical industry and
power plants are concentrated in this basin. This area is the Czech part of a
heavily polluted area known as the ´Black Triangle´. Very high deposition of
the above elements and Cd, Cu and Pb were found in the mountains on the
northern border of the CZ. Pollutants are transported to this area from distant
sources located in the Black Triangle. Very high current deposition levels of
Cd, Fe, Mo, Pb, S, and Zn were found in the black coal basins in the
northeastern part of the CZ, where coal processing, metallurgical engineering
and chemical industries are concentrated. 6.8%, 13.0%, 43.7% and 36.5%,
respectively, of the CZ territory suffered from very high, high, moderate and
small general atmospheric deposition loads weighted through the concentration
of all 14 elements in the moss samples. Analyses of samples taken at identical
places in 1991 and 1995 demonstrated a significant decrease in all measured
element deposition by between 16% (Cd) and 77% (As), due to the enormous
decrease in industrial production and the introduction of a desulphurization
programme for the power plants in the CZ in the 1990s. The average
concentrations of the elements in the moss samples were very close to the average
data published for Germany and Poland. Slightly lower concentrations (about
-20%) were found in Austria, but higher concentrations in Slovakia. Colour maps
of the distribution of current atmospheric deposition loads, and results with a
commentary, can be found in the latest Czech moss monitoring surveys (Sucharová
and Suchara 1998a, 1998b).
|
Ele- ment |
Moss |
Humus |
||||||||
|
Min. |
Max. |
Mean |
S.D. |
Median |
Min. |
Max |
Mean |
S.D. |
Mediam |
|
|
Al |
246 |
1633 |
625 |
269.855 |
548.093 |
3575 |
30075 |
9120 |
4168 |
8124 |
|
As |
0.150 |
2.796 |
0.648 |
0.469 |
0.503 |
5.49 |
167.0 |
23.8 |
17.79 |
19.20 |
|
Cd |
0.148 |
2.627 |
0.392 |
0.323 |
0.315 |
0.328 |
5.82 |
0.865 |
0.559 |
0.708 |
|
Co |
0.147 |
1.876 |
0.463 |
0.256 |
0.390 |
1.45 |
17.5 |
5.15 |
2.69 |
4.41 |
|
Cr |
0.586 |
59.337 |
1.937 |
2.135 |
1.386 |
7.48 |
94.5 |
26.5 |
13.28 |
23.40 |
|
Cu |
3.452 |
18.484 |
7.580 |
2.272 |
7.178 |
8.37 |
214 |
29.6 |
19.13 |
25.30 |
|
Fe |
135 |
5904 |
531 |
574.3 |
400 |
3043 |
36998 |
10874 |
5.738 |
9019 |
|
Hg |
0.029 |
0.177 |
0.072 |
0.027 |
0.064 |
0.329 |
2.26 |
0.676 |
0.205 |
0.656 |
|
Mo |
0.054 |
0.944 |
0.179 |
0.125 |
0.143 |
0.665 |
7.97 |
1.97 |
1.079 |
1.750 |
|
Ni |
0.825 |
15.634 |
2.354 |
1.474 |
1.944 |
6.26 |
52.6 |
18.8 |
8.11 |
17.20 |
|
Pb |
4.144 |
173.644 |
15.357 |
18.402 |
11.028 |
52.1 |
4872 |
185 |
348.4 |
141.00 |
|
S |
1048 |
2628 |
1594 |
313.5 |
1554 |
2259 |
4747 |
3045 |
417 |
2955 |
|
V |
0.580 |
7.844 |
2.427 |
1.394 |
2.001 |
9.86 |
125 |
37.5 |
19.30 |
33.20 |
|
Zn |
24.528 |
519.511 |
56.003 |
56.944 |
41.871 |
42.1 |
446 |
89.1 |
42.7 |
79.3 |
Table 1 Statistics
for a set of element concentrations (μg/g) in moss (n=192) and forest
floor humus samples (n=192) taken in the CZ in 1995.
b) Large-scale humus
monitoring
Basic statistics for humus analyses
can be found in Table 1. Humus analyses showed that the distribution of
historic (humus) and current (moss) loads had similar patterns in the CZ. The
reason for this is that industrial centres grew up at certain sites in the
second half of the 19th century, and industrial production has
continued mainly in these regions in the territory of the present-day CZ. Very
high levels of old contaminations were found for Cd, Co, Fe, Hg, Mo, Ni, Pb, V
and Zn mainly around the historic centres of the metallurgical and engineering
industries in Central Bohemian region. In the industrial lignite basin in the
northwestern cross-border area, very high historic loads of Al, As, Co, Cr, Cu,
Fe, Mo, Ni, S, and V were found. Large hot spots of high historic
contaminations of Cd, Cr, Cu, Fe, Mo, Pb, and Zn were identified in the
industrial region surrounding the black coal mines in the northeastern part of
the CZ. Generalised data showed that, respectively, very high, high, moderate
and low historic deposition loads related to all partial deposition loads of
individual elements were found, respectively, in 18%, 24% 30% and 28% of the CZ
territory. Relatively small atmospheric deposition loads have generally
affected the southern half of the CZ. Detailed interpretation of large scale
humus monitoring in the CZ was presented in the CZ national humus survey
(Sucharová and Suchara 1998c, Suchara and Sucharová 1999).
c) Fine-scale
monitoring of current and historic loads
Table 2 gives information about the
range of the absolute current (1998) atmospheric loads of the elements for the
city of Příbram and its surroundings determined by moss analyses. ´Typical
values´ of deposition are related to the average loads affecting the main of
the investigated landscape segment.
The results of principal component analysis showed four factors that may explain more than 70% of the individual element distribution in the analysed matrices. The following factors (pollution sources) were easily identified: the smelter works (chimney, slag piles and the area of the former polymetallic mine) for Ag, As, Bi, Cd, Cu, Fe, Hg, In, Ni, Pb, S, Sb, Se, Tl, Zn (old loads) and Ag, As, Cd, Cu, In, Ni, Pb, Sb, Se, Zn (current loads), former uranium mines for Al, Be, Cr, Cs, Ga, Li, Mn, Rb, Sc, Sr, Th, U, V (old loads) and Al, Be, Ce, Cr, Fe, Ga, La, Li, Nd, Pr, Sc, Th, U, V, Y (current loads), the heat-resistant steel foundry situated 15 km from the city of Příbram for Mo, and geogenic or anthropogenic factors for Tl, Ce, Co, La, Nd, Pr, and V patterns. Complete analytical and graphical results of fine-scale monitoring around the city of Příbram have been presented in a research report (Sucharová and Suchara 1999).
|
|
Ag |
Al |
As |
Bi |
Cd |
Ce |
|
Uptake coef. |
1.10 |
0.45 |
0.39 |
(0.77) |
0.72 |
0.46 |
|
Min.-Max. |
3.75-124.31 |
70807-223027 |
109.2-1409.1 |
3.07-14.74 |
41.21-1067.83 |
100.96-333.72 |
|
Typical |
4.7-7.0 |
143333-157667 |
132.3-198.5 |
8.4-9.2 |
107.5-125.4 |
182.3-196.3 |
|
|
Co |
Cr |
Cu |
Fe |
Ga |
La |
|
Uptake coef. |
0.45 |
0.60 |
0.46
(0.35-0.57) |
0.60 |
0.49 |
0.49 |
|
Min.-Max. |
45.87-286.67 |
120.4-365.5 |
3870-308478 |
43860-143835 |
29.22-95.04 |
43.18-152.96 |
|
Typical |
86.0-114.7 |
215.0-279.5 |
7010-9815 |
86000-107500 |
47.4-52.7 |
79.0-92.1 |
|
|
Li |
Mo |
Ni |
Pb |
S |
Sb |
|
Uptake coef. |
0.42 |
0.53 |
0.46 |
1.00 |
0.39 |
(1.05) |
|
Min.-Max. |
46.07-137.91 |
23.85-258.0 |
269.22-1318.04 |
869.5-127452.0 |
317208-539154 |
18.43-2899.43 |
|
Typical |
76.8-92.1 |
36.5-48.7 |
420,7-701.1 |
1935-2580 |
396923-463077 |
18.4-36.9 |
|
|
Th |
U |
V |
Y |
Zn |
*Ba,
Be, Cs, Hg In, Mn, Nd, Pr, Rb, Sc,
Se, Sr, Tl. |
|
Uptake coef. |
0.43 |
0.865 |
0.59 |
0.48 |
0.85 |
|
|
Min.-Max. |
6.0-39.6 |
3.58-71.88 |
218.64-1051.68 |
23.92-86.00 |
4598-36727 |
|
|
Typical |
21-27 |
6.0-7.5 |
328-437 |
37.6-48.4 |
7588-9106 |
|
|
*For
Ba, Be, Cs, Hg, In, Mn, Nd, Pr, Rb, Sc, Se, Sr and Tl the uptake coefficients
were not reliably known. |
||||||
Table 2 Absolute minimum, maximum and typical
values of atmospheric deposition loads (μg/m2/year) in the city
of Příbram and its surroundings assessed from moss analyses and uptake
coefficients used.
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