POLISH JOURNAL OF ECOLOGY
(Pol. J. Ecol.)
52
1
69–74
2004
Regular research paper
Krzysztof BANAÂ, Krzysztof GOS
University of Gdaƒsk, Laboratory of Freshwater Ecology, Al. Legionów 9,
80-441 Gdaƒsk, Poland, e-mail: [email protected]
EFFECT OF PEAT-BOG RECLAMATION ON THE
PHYSICO-CHEMICAL CHARACTERISTICS
OF THE GROUND WATER IN PEAT
ABSTRACT: The authors determined the
concentration of dissolved organic carbon
(DOC) and electrical conductivity, as well as the
colour and pH in the ground waters of 26 peatbogs in Pomerania (NW Poland). Three kinds of
peat-bogs have been taken into account – forestless sphagnum-cover bogs, bog coniferous forests
and birch swamps. The condition of bogs was
classified as good, moderate or poor as regards
their natural qualities. In good natural-status
peat-bogs the lowest amounts of DOC (about
30 mg C dm–3) and conductivity (<100 µS cm–1)
were found in the water of the peat of sphagnumcover bogs, higher levels were recorded in forest
peat-bog water (DOC – 50 mg C dm–3, conductivity – 100 µS cm–1). Drainage of all the kinds of
peat-bog under study leads to an increase in the
concentration of DOC (>70 mg C dm–3) and
conductivity (up to 90 µS cm–1 in degraded
sphagnum-cover bogs and 140–150 µS cm–1 in
degraded forest bogs); there also occurs an
increase in acidity (from pH 4.0–3.7 to 3.7–3.4)
and coloration (from 300 to 1000 mg Pt dm–3 in
forestless peat-bogs and from 600–800 to
1400–1600 mg Pt dm–3 in forest bogs).
KEY WORDS: peat-bogs, peat-bog reclamation, humic substances, peat-bog waters
1. INTRODUCTION
Peat-bog degradation, mainly as the
result of drainage, is a commonly known
process that concerns both the peat deposit
and the vegetation which develops on it. It
has, however, much wider impacts, because
of the carrying of water out of swamp areas.
In lakeland areas with a large number of
peat-bogs the water of many lakes is brown
in colour (L i l l i e and M a s o n 1983,
Wr i g h t 1983, G o r h a m et al. 1986,
O v e r t o n et al. 1986, R o g a l l a 1986,
Górniak 1996, BanaÊ and Gos 1998).
Numerous researchers indicate that peatbog water are responsible for the higher concentration of organic matter and the resulting colour (Engstrom 1987, Gorham et
al. 1986, Wojciechowski 1997).
The matter released during peat-bog
reclamation, primarily in the form of
humic substances, is transported along
ditches to lakes or rivers, which brings
about far reaching changes in the water and
sediments. Light intensity under water
then lowers, which affects the primary production of plankton and macrophytes
(E f f l e r et al. 1985, Wo j c i e c h o w s k i
1997, Bociàg 1998, Gos et al. 1998).
Recognition of the properties of the
waters deposited in the top layer of peat in
various kinds of peat-bogs, and of the
changes in these properties resulting from
peat-bog drainage is therefore of great practical importance, connected with the preservation of swamp and aquatic ecosystems.
This is the aim of the present research
which studies these relationships under the
local conditions of north-western Poland.
70
Krzysztof BanaÊ, Krzysztof Gos
2. STUDY AREA
Investigations were carried out in
three kinds of peat-bogs – forestless sphagnum-cover bogs, coniferous forests bog
and birch swamps.
Dominant in forestless sphagnumcover bogs are peat mosses, and their vegetation depends on the water content and
fertility of the substrate. Extremely oligotrophic, acidic peat-bogs that become partly dry in summer are characterized by the
presence of hummock peat mosses, Calluna
vulgaris, Eriophorum vaginatum and dispersed dwarfish Pinus sylvestris individuals.
Waterlogged sites on the peripheries of
dystrophic lakes, forest edges and in hollows between hummocks in raised bogs are
occupied by extremely hydrophilous
species of the genera Sphagnum, Carex and
by Eriophorum angustifolium.
Bog coniferous forests are characterized
by a well developed moss layer made up of
peat mosses with an addition of coniferousforest species. The species composition of
herbs and dwarf shrubs is similar to that of
hummocks on raised bogs; it is characteristic
for an abundant presence in bog coniferous
forests of Ledum palustre, and Vaccimium uliginosum. The canopy closure of the pine stand,
with an insignificant addition of birch, is
poor and the individual trees are low.
Coniferous forest bogs are forest raised bogs,
and their formation is often connected with
the reclamation of forestless raised bogs.
Birch swamp forests are made up of
Betula pubescens with an addition of B. verrucosa. It is a community with a rich herb
layer including ferns and club mosses,
occupying mesotrophic habitats. Because
they are shaded considerably, the habitats
lack dwarf shrubs of the family Ericaceae.
Dominant among the mosses are brown
mosses, mainly Polytrichum commune. Peat
mosses occur there in smaller numbers,
represented by shade-tolerating species.
Birch swamp forests are forest transition
bogs, formed by shallow terrain depressions, on bog coniferous forest edges and
in partly dry bog coniferous forest habitats.
3. MATERIAL AND METHODS
The studies were carried out in the
spring and summer of 1998 in Pomerania
(NW Poland). The existing natural-quality
state of the peat-bogs was assessed on the
basis of the degree of peat dryness, number
of draining ditches and physiognomy of
the plant communities. A 3-grade naturalquality state scale has been adopted:
1/ good, i.e. without signs of degradation in
vegetation and peat deposit, 2/ moderate,
i.e. with single draining ditches and first
signs of partial dryness of peat, and swamp
vegetation degeneration, 3/ poor, i.e. with
a strong vegetation degeneration, numerous draining ditches and peat-pits. Investigations were carried out in 6 sphagnumcover bogs, 12 bog pine forests and 8 birch
swamp forests, jointly in 57 variants differing in natural-quality state. From each
community three water samples were taken
from the peat at the depth of 0.5 m.
Concentration of dissolved organic
carbon (DOC) in the samples was determined by a spectroscopic method based
on the strong correlation between
absorbance and organic carbon content
(Moore 1985, 1987, Górniak 1995). For
filtered samples absorbance was measured
at 330 nm on a UV-VIS (SHIMADZU
UV-1202) spectrophotometer.
Peat-deposit water was used for the
measurement of: electrolytical conductivity by an LF-95/SET conductivity meter
with a 4-electrode TetraCon 96 system, and
water pH by a SET-1 pH-meter with a combined electrode of the EPH-11 type. Water
colour was determined in the laboratory,
according to Hermanowicz et al. (1999).
4. RESULTS
The water contained in the top peat
layer of forestless sphagnum-cover peatbogs is very acid (pH 3.64–4.56). Its pH is
highly negatively correlated with the concentration of DOC (r = –0.8) and conductivity (r = –0.94), while the concentration
of DOC is positively correlated with conductivity (r = 0.8). The physical and chemical characteristics of the sphagnumcover bog water have a wide range of variation, related to the wide microhabitat
variation of these peat-bogs.
For the water of good natural-quality
sphagnum-cover bogs a low DOC (30.6 mg
C dm–3) and conductivity (61 µS cm–1) are
found. In the water of moderate and poor
natural-quality peat-bogs much higher
DOC concentrations occur (47.1 and 65.1
71
The peat-bog reclamation and the ground water in peat
mg C dm–3). Increased concentrations of
organic carbon cause a lowering of the
water pH from 4.0 to 3.7 (Table 1, Fig. 1).
DOC [mgC dm–3]
75
60
45
30
15
22000
2 0
nd 18161040
uc
20
tiv 1 10080
ity
60
Co
3.5
[µ
3.7
4.5
4.3
.1
4
3.9
Sc
m–
4.7
pH
1
2
3
between pH and conductivity (r = –0.95),
and between pH and DOC (r = –0.93), as
well as a positive correlation between conductivity and DOC (r = 0.87).
In the process of bog coniferous forest
drainage, the direction of changes in the
physical and chemical traits of the water is
concordant with that seen in forestless
sphagnum-cover bogs. The water pH drops
from 3.6 to 3.5, conductivity rises from 102
to 141 µS cm–1, and so does DOC concentration from 53.8 to 74.9 mg C dm–3 (Table
1, Fig. 2), but the range of variation of
these characteristics is narrower than in
the case of sphagnum-cover bogs.
1
]
In bog coniferous forests the waters
contained in the top layer of peat are characterized by levels of conductivity which are
twice as high as in the sphagnum-cover
bogs (120.6 versus 67.3 µS cm–1). Water pH
is insignificantly lower, but the range of pH
variation is much narrower. The dark
brown coloration of the water
(colour > 1000 mg Pt dm–3) is the result
of a high DOC content (61.3 mg C dm–3).
As in the case of sphagnum-cover bogs,
there occurs a highly negative correlation
85
80
75
70
65
60
55
50
0
pH
Co 19 70
nd 1 0
.8
3
5
uc 1 0
3.7
tiv 13 0
1
ity 11
3.6
5
0
[µ
.
2
S c 9 70 .4 3
3
m–
1
3
]
DOC [mgC dm–3]
Fig. 1. Variation of the properties of the
ground waters of the forestless sphagnumcover bogs studied, differing in their naturalquality state.
Natural-quality state: 1 – good, 2 – moderate,
3 – poor.
Fig. 2. Variation of the properties of the
ground waters of the bog pine forests studied,
differing in their natural-quality state.
Natural-quality state: 1 – good, 2 – moderate,
3 – poor.
Table 1. Characteristics of the ground water of various kinds of peat-bogs in relationship to their
natural-quality state.
Natural
quality state
Number of
sample
good
moderate
poor
9
3
3
good
moderate
poor
10
10
4
good
moderate
poor
9
3
6
pH ± SD
Conduct. ± SD
cm–1
(µs
)
forestless sphagnum-cover bogs
3.97 ± 0.32
61.0 ± 29.5
3.78 ± 0.03
70.0 ± 4.0
3.71 ± 0.04
83.7 ± 5.9
bog pine forests
3.64 ± 0.08
102.9 ± 18.7
3.56 ± 0.13
130.2 ± 35.6
3.49 ± 0.08
140.9 ± 36.1
birch swamp forests
3.70 ± 0.17
107.0 ± 24.2
3.50 ± 0.05
142.0 ± 10.4
3.44 ± 0.08
154.9 ± 35.6
Colour ± SD
3
DOC ± SD
(mg Pt dm )
(mg C dm–3)
333 ± 135
660 ± 60
2533 ± 289
30.6 ± 12.3
47.1 ± 3.2
65.1 ± 2.8
709 ± 241
1041 ± 405
1675 ± 96
53.8 ± 6.9
63.4 ± 11.9
74.9 ± 3.9
814 ± 162
833 ± 76
1427 ± 360
58.1 ± 5.7
61.0 ± 6.7
73.0 ± 5.5
72
Krzysztof BanaÊ, Krzysztof Gos
The physical and chemical characteristics
of the water in birch swamp forests only
slightly differ from those found in bog
coniferous forests. Water pH is the same
(pH 3.6), slightly higher are conductivity
(129 versus 121 µS cm–1) and DOC concentrations (63.5 versus 61.3 mg C dm–3;
Table 1). Water pH is negatively correlated
with electrolytical conductivity (r = –0.93);
a similar though weaker relationship exists
between pH and DOC (r = –0.75), while
conductivity and DOC are correlated positively (r = 0.75).
Reclamation of birch swamp forests
leads to a lowering of the water pH (from
3.7 to 3.4) and a rise in conductivity (from
107 to 155 µS cm–1) and DOC concentration (from 58.1 to 73.0 mg C dm–3;
Table 1, Fig. 3).
DOC [mgC dm–3]
85
80
75
70
65
60
55
50
pH
Co 22000
4.1
nd 2 180
uc 160 0
3.9
tiv 14 0
1
7
.
ity 12 0
3
[µ 10 0
5
.
3
2
Sc 8 0
m – 6 3.3
1
3
]
Fig. 3. Variation of the properties of the
ground waters of the birch swamp forests
studied, differing in their natural-quality state.
Natural-quality state: 1 – good, 2 – moderate,
3 – poor.
5. DISCUSSION
The water deposited in the top peat
layer of forestless sphagnum-cover bogs
contains much less DOC, and its conductivity is considerably lower than in the
water of bog coniferous forests and birch
swamp forests. The near-surface peat of
forest peat-bogs is more decomposed than
that of forestless peat-bogs. As a result of
a partial drying of peat-bogs, peat decomposition increases, due to which the concentration of DOC in the water rises. The
waters of poor natural-quality sphagnumcover bogs are in this respect similar to
waters typical of bog coniferous forests,
but the content of inorganic substances
stays at a fairly low level. The cause of this
is the complex-forming tendency of DOC
(and humic substances) with inorganic
substances released by the muck-formation process. The complexing of metal ions
(D r i s c o l l et al. 1980, B u f f l e 1984,
Sposito 1986, Kinniburgh et al. 1996)
affects their circulation in ecosystems
(B e c k et al. 1974, S h o l ko v i t z and
Copland 1982, Driscoll et al. 1988).
Subject to neutralization are harmful compounds such as pesticides and herbicides.
On the other hand, microelements essential to organisms are made unavailable
(Jackson and Hecky 1980, Stewart and
Wetzel 1982, Guildford et al. 1987).
Organic carbon concentration in the water
from the peat of good natural-quality
sphagnum-cover bogs amounted to 30 mg
C dm–3. The result was identical with that
found by Oliver et al. (1983) in Ontario
and Nova Scotia in USA. According to
Górniak’s studies (1996), in the transition and raised-bogs of north-eastern
Poland DOC concentration attains the
level of 27.8 mg C dm–3.
In respect of DOC concentration in
the ground water, bog coniferous forests are
very similar to birch swamp forests, and
with the progressing drainage of both peatbog forest types the differences decrease
gradually. In all the habitats studied, partial
drying of bogs was followed by a strong coloration of the water, caused by its enrichment with dissolved organic matter. Large
amounts of the humic acids present cause
a decrease in the pH of the water which is
very acidic already. In Okefenokee swamp,
L obartini et al. (1991) found equally acid
(pH 3.8) and intensively coloured waters,
which were, however, less than half as concentrated in DOC (25.1 mg C dm–3).
Organogenic habitats are rich sources
of dissolved organic carbon and humic substances (McKnight et al. 1985,Urban
et al. 1987, 1989). The magnitude of outflow from them thus determines the
amount of DOC exported from them
(B r i n s o n 1976, M u l h o l l a n d and
Kuenzler 1979). Reclamation increases
the magnitude of the outflow, and due to
the changes that occur in the peat as
a result of drying, the water which flows
The peat-bog reclamation and the ground water in peat
out contains increasingly large amounts of
DOC. The action of such waters on lake
ecosystems may lead on to the transformation of the latter into humic water bodies.
6. CONCLUSION
Peat-bog drainage leads to increased
DOC and mineral salt concentrations, as
well as acidification and coloration of the
ground water present in the peat. The negative impact of the peat-bog waters carried
off on the surrounding aquatic ecosystems
increases with the progress of peat-bog
degradation.
ACKNOWLEDGMENTS: The research was
financially supported by the Polish State
Committee for Scientific Researches, under
Project 6PO4F 017 12. The senior author (KB)
is a scholar-ship-holder of FNP (Foundation
for Polish Science).
7. SUMMARY
The authors determined the concentration of
organic (DOC) and mineral substances, as well
as the colour and pH in the ground waters of 26
peat-bogs in Pomerania (NW Poland). Three
kinds of peat-bogs have been taken into account
– forestless sphagnum-cover bogs, bog coniferous forests and birch swamps. The research covered objects with a good, moderate or poor status as regards their natural qualities that endure.
In good natural-status peat-bogs the lowest
amounts of organic (about 30 mg C dm–3) and
inorganic (conductivity <100 µS cm–1) substances were found in the water of the peat of
sphagnum-cover bogs, higher levels were recorded
in forest peat-bog water (DOC – 50 mg C dm–3,
conductivity – 100 µS cm–1; Table 1).
For the water of good natural-quality sphagnum-cover bogs a low DOC and conductivity are
found. In the water of moderate and poor natural-quality peat-bogs much higher DOC concentrations occur. Increased concentrations of
organic carbon cause a lowering of the water pH
from 4.0 to 3.7 (Table 1, Fig. 1).
In the process of bog coniferous forest
drainage, the direction of changes in the physical
and chemical traits of the water is concordant
with that seen in forestless sphagnum-cover
bogs. The water pH drops from 3.6 to 3.5, conductivity rises, and so does DOC concentration
(Fig. 2), but the range of variation of these characteristics is narrower than in the case of sphagnum-cover bogs.
Reclamation of birch swamp forests leads to
73
a lowering of the water pH and a rise in conductivity and DOC concentration (Fig. 3).
The amount of inorganic and organic substances exported due to the drainage of peat-bogs
increases with the progress of peat-bog degradation. Waters flowing out of such bogs have an
increasingly negative impact on aquatic ecosystems, e.g. lakes into which they are conveyed.
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