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Accumulation and distribution of organic matter in sediments of salt-affected shallow lakes at Szeged, Hungary

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The primary aim of the research is to investigate the accumulation and distribution of organic material [OM] in saline shallow lacustrine sediments. This study focuses on the OM parameters of sediments at two areas with different hydrology, land use and vegetation cover. The study area is located at the Fehér Lake, Szeged (Hungary). The studied salt-affected lake system has been under intensive fish breeding from 1970. Sampling was made during the spring of 2007. In case of the profiles a 4 m deep 10 cm diameter sediment core was extracted. The OM data were measured with Rock-Eval pyrolysis , and the proportion of different OM groups was determined by the mathematical deconvolution of Rock-Eval pyrograms. It is showed that there are significant differences in OM distribution and characteristics if the different study sites are compared. In case of both profiles similar changes can be detected in the origin, quantitative and qualitative parameters of OM at depths of 15, 30, and 65-70 cm, which proves that the two sites belonged to the same depositional system, and similar changes affected them during sediment formation. Although both profiles have the same depositional environment, significant difference can be seen between the profiles. The profile 1. used to be located in coastal natural territory till 1970 and the profile 2. represents a constant water-irrigated fields. The fluctuation of F1+F2 and F3 values in Profile 1. suggests that the OM content of the marginal territory (both in its natural and present state) is determined by the alternation of dry and wet periods, sometimes with a high algae production in slack waters. Based on the quality parameters of OM, dry and wet accumulation periods can be separated , and signs of human influence can also be identified.
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Scientific Annals, School of Geology, Aristotle University of Thessaloniki
Proceedings of the XIX CBGA Congress, Thessaloniki, Greece
Special volume 100
39-45
Thessaloniki
2010
ACCUMULATION AND DISTRIBUTION OF ORGANIC MATTER IN
SEDIMENTS OF SALT-AFFECTED SHALLOW LAKES AT SZEGED,
HUNGARY
Bozsó G., Pál-Molnár E.,Nyilas T., Hetényi M.
Department of Mineralogy, Geochemistry and Petrology, Faculty of Science and Informatics, University of Szeged,
H-6722 Szeged, Hungary, bozso.gabor@geo.u-szeged.hu
Abstract: The primary aim of the research is to investigate the accumulation and distribution of organic
material [OM] in saline shallow lacustrine sediments. This study focuses on the OM parameters of se-
diments at two areas with different hydrology, land use and vegetation cover. The study area is located
at the Fehér Lake, Szeged (Hungary). The studied salt-affected lake system has been under intensive
fish breeding from 1970. Sampling was made during the spring of 2007. In case of the profiles a 4 m
deep 10 cm diameter sediment core was extracted. The OM data were measured with Rock-Eval pyroly-
sis, and the proportion of different OM groups was determined by the mathematical deconvolution of
Rock-Eval pyrograms. It is showed that there are significant differences in OM distribution and charac-
teristics if the different study sites are compared. In case of both profiles similar changes can be detected
in the origin, quantitative and qualitative parameters of OM at depths of 15, 30, and 65-70 cm, which
proves that the two sites belonged to the same depositional system, and similar changes affected them
during sediment formation. Although both profiles have the same depositional environment, significant
difference can be seen between the profiles. The profile 1. used to be located in coastal natural territory
till 1970 and the profile 2. represents a constant water-irrigated fields. The fluctuation of F1+F2 and F3
values in Profile 1. suggests that the OM content of the marginal territory (both in its natural and present
state) is determined by the alternation of dry and wet periods, sometimes with a high algae production in
slack waters. Based on the quality parameters of OM, dry and wet accumulation periods can be sepa-
rated, and signs of human influence can also be identified.
Key words: organic matter distribution, shallow lake, salt-affected sediment
1. Introduction
The quality and quantity of organic material [OM]
preserved in sediments provide trustable informa-
tion on the circumstances of accumulation, the
characteristics of natural and human sources, and
post-sedimentation processes influencing OM dis-
tribution (Meyers, 2003). While OM in marine se-
diments has implications on long term phenome-
non, the quantity, quality and distribution of OM in
the sediments of shallow lakes is primarily deter-
mined by short term and local processes. The pre-
servation and transformation of OM is highly in-
fluenced by actual hydrologic, climatic and geo-
chemical parameters (Ariztegui et al., 2001; Sebag
et al., 2006). Most of the researches focus on the
OM of marine and deep water lacustrine environ-
ments, the organic geochemistry of shallow, conti-
nental lakes is usually out of the scope of these
studies. On the other hand due to global climate
change, the area of shallow lakes and territories
with water-affected soils, usually both influenced
by salinization processes, is continuously increas-
ing (Das et al., 2008; Tóth et al., 2006). As a con-
sequence, the investigation of the organic geoche-
mistry of these territories is getting more and more
important. The extreme evaporation and hydrolog-
ical conditions on saline territories can considera-
bly affect geochemical processes (Bozsó et al.,
2008), and thus the accumulation and preservation
of OM.
An adequate analytical procedure for determining
the quantitative and qualitative parameters of OM,
influenced by the above processes, is Rock-Eval
pyrolysis (Disnar et al., 2003). By the mathematic
analysis of the measured pyrograms stable and un-
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
40
stable biopolymers (F1, F2), immature and mature
refractory geopolymers (F3, F4) can easily be se-
parated (Sebag et al., 2006), and accumulation
events can also be delineated and identified in the
sediment record (Hetényi et al. 2005).
The primary aims of the present research are to de-
termine the quantity of OM in sediments of shal-
low lakes affected by salinization, to identify the
origin of OM, to investigate the transformation
processes of bio and geopolymers, and finally on
the basis of the above data, to identify the deposi-
tional conditions.
2. Materials and methods
In accordance with the aims of the research the
sampling sites were chosen to be at Lake Fehér
near Szeged, Hungary (Fig. 1). The lake system
and its environment were formed by the fluvial and
aeolian accumulation processes of the Carpathian
Basin (Keveiné et al., 2000). The studied lake sys-
tem, with a catchment of 200 km2 and a net area of
14 km2, is affected by intensive fish breeding,
though some areas are still considered natural and
protected by the Kiskunság National Park.
Sampling was made during the spring of 2007 at
four different locations with different hydrogeolo-
gy and land use. Because of the lack of space only
two profiles are presented in this paper.
In case of the profiles a 4 m deep 10 cm diameter
sediment core was extracted. The cores were dis-
sected into 5 cm units and dried on room tempera-
ture for 3 weeks.
2.1. Description of sampled areas
Profile 1
Control site on a saline tussocky meadow. It is the
farthest from human activity. It is marshy, and in-
undated by water for 1-2 months during the spring
period. By the 1970s the territory was at the mar-
gin of the natural lake system, since then, for al-
most 40 years it has been a buffer zone for the arti-
ficially created lake system too (Keveiné et al.,
2000). However, conditions of hydrology and ve-
getation cover hardly changed.
Stratigraphy of profiles 1
The soil type along the profile is mostly sandy
loess (Fig. 1) (Molnár, 1996). The ratio of the sand
fraction (> 63 μm) is about 10 % in the whole
depth of the profile (Fig. 2). The ratio of the aleu-
Fig. 1. Geological map of the sampling area and the location of profiles
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
41
rite fraction (63-2 μm) is the highest in the profile
and with the exception of the upper 10 cm it is in-
creasing with depth. The ratio of the clay fraction
(< 2 μm) is the opposite of the aleurite fraction, it
is decreasing with depth. The horizon A (from 0
cm to 30 cm) of the profile contains over 3 % of
total organic carbon (TOC) that is decreasing to
0% at 100 cm. This level has a loose structure and
a light brownish black color. The accumulation of
salt can be founded in the depth of 50 cm. It is a
level of the horizon B, too. Under this layer the
carbonate starts to appear in the profile, it is indi-
cated by the yellowish grey color of the sediment,
too.
Profile 2
Directly affected by human activities. It is inun-
dated artificially each year by 1-1.5 m water from
April till October. During March-April 10-20 cm
high vegetation can develop. By the 1970s this
area was located in the central part of the natural
lake system. Following the earthworks of the
1970s it has been used for fish breeding (Keveiné
et al., 2000).
Stratigraphy of profiles 1
The soil type along the profile is mostly sandy in-
fusion loess (Fig. 1) (Molnár, 1996). The grain size
ratios show more difficult distribution than in the
case of profile 1 (Fig. 3). The ratio of the sand
fraction is higher than in the first case (20-30 %), it
is decreasing from the surface to 60 cm and it is
apparently increased in the level of 75-95 cm. The
distribution of aleurite (~ 50%) and clay (~ 20%)
fraction is quite uniform. The horizon A of the pro-
file is relatively thin (10 cm depth from the sur-
face) and contains only about 1 % of TOC. The
amount of TOC is 0% below the level of 100 cm.
This level has a loose structure and a light yello-
wish brown color. The boundaries of horizon B
and C are not distinguished because this profile
looks like disturbed by the water flow.
2.2. Analytical methods
Data of the Rock-Eval pyrolysis were measured
with Oil Show Analyzer: preheat for 4 minutes on
108 °C, programmed pyrolysis with a 25 °C/min
ramp rate till 600 °C. Subsequently, the samples
were oxidized in a constant airflow for 7 minutes
on 600 °C. The proportion of different OM groups
was determined by the mathematical deconvolu-
tion of Rock-Eval pyrograms (Disnar et al., 2003).
In order to determine more precisely the origin of
OM the Corg/N ratio (Meyers, 2003) was also
measured in 7 samples.
3. Results and discussion
Total organic content (TOC) was measured from
160 samples concerning the two profiles. Based on
the results, only the upper 100 cm section of both
profiles contained an appreciable amount of OM,
going deeper the concentration of OM was below
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
42
the detection limit. As a consequence, detailed
Rock-Eval analyses were only performed on the
upper 100 cm layer of the profiles.
Concerning both parameters the differences be-
tween the two sites are striking (Table 1). TOC
values varied between 0.2 and 2.0 % in the sam-
ples. These values are lower than usual OM con-
centrations measured in lake sediments (Das et al.,
2008). In Prof.1 TOC values are higher and show a
continuous decrease with depth (Fig. 4).
Nevertheless, the amount and distribution of TOC
measured in Prof.2 are very much different (Fig. 4).
Table 1. Average values of organic carbon contents, HI and the relative contribution of major classes in the profile 1
and profile 2.
Depth
(cm)
TOC (%)
HI
(mgHC/gsoil)
F1 (%)
F2 (%)
F3 (%)
Corg/N
Prof1
Prof2
Prof1
Prof2
Prof 1
Prof 2
Prof 1
Prof 2
Prof 1
Prof 2
Prof 1
Prof 2
0
2.00
1.34
135
115
2.71
1.78
40.26
36.38
57.03
61.85
5
2.10
1.13
135
80
4.05
4.10
35.79
39.73
60.16
56.17
10
1.82
1.02
117
52
1.32
0.00
41.96
43.28
56.72
56.72
19.30
15
1.09
0.83
67
49
0.00
1.51
53.63
39.42
46.37
59.07
16.10
20
1.03
0.89
64
58
1.74
3.30
49.13
38.91
49.13
57.79
25
0.92
0.46
58
73
0.00
1.16
48.36
36.29
51.64
62.55
15.30
10.70
30
0.82
0.58
57
84
2.49
0.82
38.91
37.16
58.60
62.02
35
0.73
0.79
60
78
3.05
0.87
50.61
36.29
46.34
62.84
40
0.80
0.84
50
55
0.39
0.00
49.25
35.66
50.36
64.34
45
0.67
0.43
46
79
3.62
2.70
44.43
35.28
51.95
62.02
50
0.59
0.58
45
70
2.92
5.88
37.83
35.58
59.26
58.54
16.90
55
0.62
0.63
48
53
2.70
1.43
60.11
36.08
37.19
62.50
60
0.53
0.58
116
67
22.52
0.89
25.85
40.72
51.62
58.40
65
0.39
1.19
56
105
3.43
3.07
36.47
31.77
60.10
65.16
70
0.35
1.37
45
91
1.69
3.12
35.35
30.52
62.96
66.36
13.30
75
0.29
1.13
51
74
1.76
0.00
36.36
33.97
61.88
66.03
8.80
80
0.32
0.99
43
68
4.03
0.00
37.81
36.00
58.17
64.00
85
0.24
0.87
79
71
8.04
0.00
47.50
35.21
44.46
64.79
90
0.21
0.75
69
67
0.00
0.00
5.78
37.85
94.22
62.15
95
0.20
0.60
64
60
3.97
0.00
28.35
32.43
67.68
67.57
Fig. 3. Grain size distribution of profile 2.
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
43
TOC values are lower, and their downward change
is uneven. From the surface till 60 cm with some
smaller exceptions a decreasing tendency can be
seen, but below 80 cm its value increases above
1 %. In both profiles the upper 15 cm has a higher
TOC, which can be explained by the introduction
of fish breeding in the 1970s. The distribution of
Hydrogen Index (HI) is similar to that of TOC in
both profiles, thus it is less even in case of the lake
profile. The proportional variation of bio and geo-
polymers also refers to diverse sedimentation and
transformation processes. Basically, the amount of
biopolymers (F1, F2) in the sediment is similar to
that of immature geopolymers (F3). However, the
values measured for inert geopolymers (F4) are
negligible compared to the previous three parame-
ters, thus values of polymers are represented on
ternary plots (Figs. 5). On the basis of ternary plots
representing the proportional distribution of bio
and geopolymers, it is obvious that the values in
Profile 1 can be classified into several groups (Fig.
5), while in Profile 2 they are almost entirely
homogenous. These distributions and the change of
F1+F2 and F3 with depth suggest that Profile 1.
was periodically inundated and then desiccated in
its natural state on the margin of the lake system.
Both in its natural and present situation Profile 2
has been the farthest from dryland environments,
therefore the accumulation and preservation of OM
was more even here. This is also reinforced by
Corg/N ratios. In Profile 1 values refer to low algae
(8.8) and much higher dry land (19.3) origin of
OM (Meyers, 2003), which can be another proof of
temporary water cover. On the contrary, in Profile
2 Corg/N values mostly sign a dry-land origin, i.e.
in the middle of the lake system sediments pre-
served the remainings of dry-land plants, trans-
ported there presumably by wind. Although the
amount and maturity of OM varied over time on
the basis of TOC and HI values, the dry-land
supply seems to be inevitable.
4. Conclusions
In our work we mainly aimed at the characteriza-
tion of OM accumulating in shallow saline lake
sediments with special hydrological conditions.
We also attempted to answer whether human activ-
ity can result in detectable changes in OM charac-
teristics. In general, the OM parameters measured
in the two geologically and pedologically similar
Fig. 4. TOC, HI, F1+F2, F3 values of the profiles.
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
44
profiles were very different, and values mainly de-
pend on hydrological conditions and the degree of
human influence. In both profiles the increased
TOC above 15 cm refers to human activity. Al-
though both profiles have the similar depositional
environment, significant difference can be seen be-
tween the profiles. The profile 1 used to be located
in coastal natural territory till 1970 and the profile
2 represents a constant water-irrigated fields. The
TOC distribution in profile 1 corresponds well to
the OM distribution in meadow soils (Dismar et al.,
2003): due to permanent vegetation cover and a
continuous OM supply, in the oxidative environ-
ment of the porous media the transformation of
OM is even. The fluctuation of F1+F2 and F3 val-
ues in Profile 1. suggests that the OM content of
the marginal territory (both in its natural and
present state) is determined by the alternation of
dry and wet periods, sometimes with a high algae
production in slack waters (It can be seen on the
increased HI in fig. 4). The variation of values in
case of profile 2 refers to periodical differences in
sedimentation conditions. These results are also
reinforced by Corg/N ratios. In profile 2 F1+F2, F3
values and Corg/N ratios suggest that OM has al-
ways had a dry-land origin, however in terms of
the quantity and maturity of OM well definable se-
dimentation cycles can be identified here as well.
In case of profile 2 the increased amounts of TOC
and HI in depth of ~30 cm and ~70 cm indicate the
water covered period and the high algae production.
In case of both profiles significant changes can be
detected in the origin, quantitative and qualitative
parameters of OM at depths of 15, 30 and 65-70
cm, which proves that the two sites belonged to the
same depositional system, and similar changes af-
fected them during sediment formation. Based on
the F1, F2 and F3 values, the OM in the sediment
of the study areas is primarily young and unaf-
fected by transformation processes. The downward
change of biopolymers (F1+F2) and immature
geopolymers (F3) is highly variable in case of the
meadow profile, while it is much more even in the
lacustrine profile.
Based on the data it can be assess that the lake se-
diments can preserve the small changes in the OM
accumulation. If the present results are compared
to pH values and mineral compositions (Bozsó et
al., 2008) then it turns clear that salinization
processes do not have fundamental influence on
the synsedimentary characteristics of OM, and pre-
servation is more directly determined by the actual
deposition and hydrological conditions.
Acknowledgements
The financial background of this work was ensured
by the Hungarian National Science Found (OTKA),
Grant No. T-48325.
References
Ariztegui D., Chondrogianni C., Lami A., Guilizzoni P.,
Lafargue E., 2001. Lacustrine organic matter and the
Holocene paleoenvironmental Record of lake Alba-
no (central Italy). J. of Paleolimnology 26, 283-292.
Bozsó G., Pál-Molnár E., Hetényi M., 2008. Relations
of pH and mineral composition in saltaffected lacu-
strine profiles. Cereal Research Communications 36,
1463-1466.
Fig. 5. Rates of F1, F2, F3, F4 fractions in the profiles.
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
45
Das B., Nordin R., Mazumder A., 2008. An alternative
approach to recontructing organic matter accumu-
lation with contrasting watershed disturban-ce histo-
ries from lake sediments. Environmental Pollution
155, 117-124.
Disnar J.R. Guillet B., Keravis D., Di-Giovanni C., Se-
bag D., 2003. Soil organic matter (SOM) chara-
cterization by Rock-Eval pyrolysis: scope and limi-
tations. Organic Geochemistry 34, 327-343
Hetényi M., Nyilas T., M-Tóth T., 2005. Stepwise
Rock-Eval pyrolysis as a tool for typing heteroge-
neous organic matter in soils. J. of Anal. Appl. Py-
rolysis 74, 45-54.
Keveiné B.I., Mucsi L., Tímár B., 2000. The changes of
state of the Fehér Lake at Szeged. In: Frisnyák, S.
(Ed.), The historical geography of the Hungarian
Great Plain. Nyíregyháza, pp. 5366. (in Hungarian
with English abstract).
Molnár B., 1996. The geological and hydrogeological
characteristic of Fehér-lake at Szeged, Hungary.
Hidrology Bulletin 76/5, 266-271. (in Hungarian
with English abstract).
Meyers P.A., 2003. Applications of organic geoche-
mistry to paleolimnological reconstructions: sum-
mary of examples from the Laurentian Great Lakes.
Organic Geochemistry 34, 261-290.
Sebag D., Disnar J.R., Guillet B., Di Giovanni C., Ver-
recchia, E.P., Durand, A., 2006. Monitoring organic
matter dynamics in soil profiles by Rock-Eval pyro-
lysis: bulk characterization and quanti-fication of
degradation. European Journal of Soil Science doi:
10.1111/j.1365-2389.2005.00745.x
Tóth T., Szendrei G., 2006. Types and distribution of
salt affected soils in Hungary, and the characteri-
zation of the processes of salt accumulation. Topo-
graphia Mineralogica Hungariae IX, 7-20.
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
46
Ψηφιακή Βιβλιοθήκη Θεόφραστος - Τμήμα Γεωλογίας. Α.Π.Θ.
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Application of Rock-Eval pyrolysis to soil organic matter (SOM) quantitation and characterization has been explored by the study of about 100 soil samples taken from a variety of soil profiles from different ecosystems at different latitudes. A straightforward illustration of these possibilities can be obtained from a Hydrogen Index (HI in mg hydrocarbons g−1 TOC) vs. Total Organic Carbon (TOC) diagram that effectively allows one to follow simultaneously the main qualitative (SOM hydrogen richness given by HI values) and quantitative (TOC) changes that affect SOM with increasing depth and humification, in the soil profiles. In addition, abnormally high Oxygen Index (OI in mg CO, CO2 or O2 g−1 TOC) values are fully diagnostic of extensive SOM alteration, as frequently observed in podzol B horizons. More detailed information on the heterogeneity of SOM and on its degree of evolution, can be gained from the shape of the pyrolysis S2 peak recorded in the course of programmed pyrolysis in an inert atmosphere (N2) and/or from its maximum temperature "Tpeak". All these parameters and others, all determined rapidly and automatically, are particularly useful to screen major SOM variations within large sets of samples
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A number of proxies, including carbon to nitrogen ratio (C:N) and stable isotopes (delta(13)C and delta(15)N), have been used to reconstruct organic matter (OM) profiles from lake sediments and these proxies individually or in combination cannot clearly discriminate different sources. Here we present an alternative approach to elucidate this problem from lake sediments as a function of watershed scale land use changes. Stable isotope signatures of defined OM sources from the study watersheds, Shawnigan Lake (SHL) and Elk Lake (ELL), were compared with sedimentary proxy records. Results from this study reveal that terrestrial inputs and catchment soil coinciding with the watershed disturbances histories probably contributed in recent trophic enrichment in SHL. In contrast, cultural eutrophication in ELL was partially a result of input from catchment soil (agricultural activities) with significant input from lake primary production as well. Results were consistent in both IsoSource (IsoSource version 1.2 is a Visual Basic program used for source separation, (http://www.epa.gov/wed/pages/models/isosource/isosource.htm) and discriminant analysis (statistical classification technique).
Relations of pH and mineral composition in saltaffected lacustrine profiles
  • G Bozsó
  • E Pál-Molnár
  • M Hetényi
Bozsó G., Pál-Molnár E., Hetényi M., 2008. Relations of pH and mineral composition in saltaffected lacustrine profiles. Cereal Research Communications 36, 1463-1466.
The historical geography of the Hungarian Great Plain
  • B I Keveiné
  • L Mucsi
  • B Tímár
Keveiné B.I., Mucsi L., Tímár B., 2000. The changes of state of the Fehér Lake at Szeged. In: Frisnyák, S. (Ed.), The historical geography of the Hungarian Great Plain. Nyíregyháza, pp. 53-66. (in Hungarian with English abstract).
The geological and hydrogeological characteristic of Fehér-lake at Szeged
  • B Molnár
Molnár B., 1996. The geological and hydrogeological characteristic of Fehér-lake at Szeged, Hungary. Hidrology Bulletin 76/5, 266-271. (in Hungarian with English abstract).
Types and distribution of salt affected soils in Hungary, and the characterization of the processes of salt accumulation
  • T Tóth
  • G Szendrei
Tóth T., Szendrei G., 2006. Types and distribution of salt affected soils in Hungary, and the characterization of the processes of salt accumulation. Topographia Mineralogica Hungariae IX, 7-20.