Sedimentation Dynamics And Heavy Metal
Pollution History in Cruhlic Lake, Danube
Delta, Romania
Simon H. 1,*, Kelemen Sz.1, Gabor A.-I.1,2,
Preoteasa L.3, Begy R.-Cs.1,2
1Faculty
of Environmental Science and Engineering, Babeș-Bolyai University,
Cluj-Napoca, Cluj, 400294 Romania
2Interdisciplinary Research Institute on Bio-Nano-Sciences, Babeş-Bolyai
University, Cluj-Napoca, 400271 Romania
3Faculty of Geography, University of Bucharest, Bucharest, 010041 Romania
Outlines
• Aims and Scopes
• Why the 210Pb method?
• Brief description of the used measuring
methods
• Sampling site: Cruhlig Lake, Danube Delta
• Results and Discussion
• Conclusions
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Aims and Scopes
• To apply the 210Pb radiometric method on the danube
deltaic Cruhlig Lake
• To generate the geochronology of the the sediment layers
• To assess the sedimentation rates of the deltaic Cruhlic
Lake and to determine the dynamics of the sedimentation
processes involved in the evolution of the Danube Delta
• To reconstruct the history of heavy metal concentrations
in sediment layers
• To determine the effects of natural impacts and anthropic
interventions on the Danube Delta (IRON GATES, 1972)
Babes-Bolyai University, Faculty of Environmental Science and Engineering
The 210Pb dating method
• Is one of the most important means for dating recent sediments (0-150
years)
• Records stored in natural archives, such as lake sediments or peat bog
accumulation, are used in a wide range in environmental researches, for
example:
– The assessment of changing erosion rates in a catchment arising from
disturbances such as deforestation, changing agricultural practice;
– Determination of the history of changes in lake water quality associated with
problems such as eutrophication or “acidic rain”
– Monitoring atmospheric pollution by heavy metals, organic pollutants,
radioactive emissions from nuclear installations and other contaminants
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Models for
210Pb
assessment
CIC Model (Constant Initial Concentration)
• Constant erosion processes + water residence time → constant
sedimentation rate
• Assumption: Unsupported 210Pb has the same initial activity at the time of
deposition for each sediment layer
CS Model (Constant Sedimentation)
• Sedimentation fluxes known at the moment of deposition
• Constant sedimentation (Sediment flux/sediment 210Pb concentration ratio
constant)
CF:CS Model (Constant Flux, Constant Sedimentation)
• Assumption: constant sediment flux on surface, constant mass
accumulation
CRS Model (Constant Rate of Supply)
• Applied to non-constant sediment accumulation rates
• Assumption: deposition of unsupported 210Pb is constant
Babes-Bolyai University, Faculty of Environmental Science and Engineering
γ-spectrometry
• High
resolution
gamma
spectrometric
measurements
ORTEC GMX HPGe detector
(FWHM of 1.92 keV at 1.33 MeV
and a 0.5 mm Be window)
• The 46 keV gamma energy was
used for determining 210Pb
• 226Ra was determined by using
the 294 keV, 351 keV and 609
keV gamma energies, relative
method (IAEA-385)
Babes-Bolyai University, Faculty of Environmental Science and Engineering
α-spectrometry
• Total 210Pb content measured via 210Po
• 0.5g sediment added 0.3 ml 100 Bq/l
209Po (chemical yield)
• acidic digestion using 2x10 ml 65%
HNO3, 2 x 10 ml 35% HCl, 10 ml 6N HCl
and 10x3 ml 8:1 35% H2O2: 35% HCl)
• deposition on high nickel content
stainless steel discs (3 h at 85°C in a
drying oven),
• interferrents
(iron
ions)
being
eliminated by ascorbic acid.
• measured by an ORTEC SOLOIST
900mm2 PIPS detector, (resolution of
19 keV) and an ASPEC-92 data
acquisition system.
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Heavy metal concentrations
• Heavy metals were determined using an
Inductively Coupled Plasma Mass Spectrometer
(SCIEX Perkin-Elmer Elan DRC II)
• Analyses were made in triplicate and the mean
values are reported
• Samples with ion concentrations exceeding the
calibration range were diluted accordingly and reanalyzed
• The measured heavy metals being Li, Mg, Al, K,
Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg and Pb
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Sampling site: The Cruhlig Lake
•Marine part of the
Danube Delta
•South
to
the
Sf.
Gheorghe branch
•Formed 330-500 years
ago
•Access only through a
3.5 km channel
•5 cores taken with a
gravity corer during 2
sampling campaigns
•Cores
sub-sampled,
dried, homogenized
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Physical parameters
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Carbon content
Babes-Bolyai University, Faculty of Environmental Science and Engineering
226Ra
and 210Pb activity concentration
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Ages of the sediment layers
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Sedimentation rates
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Heavy metal concentrations CR2
Values of the marine substrate are exceeded
• 2x in case of Co;
•4x in case of Zn, Cd, As;
•10x in case of Hg, Cr , Pb ,
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Heavy metal concentrations CRII1 & CRII3
CRII1
CRII3
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Conclusions
•
•
•
•
•
•
•
210Pb
dating method was used to determine ages and
sedimentation rates of five sediment cores taken from the Cruhlig
Lake, Danube Delta, Romania.
impact of recent flooding events (1960-70, 1981-82, 1987-88 and
1995-2005) and the decreasing effect of the Iron Gates on the
incoming sediment quantity is visible
The locations of CRII1 and CRII2 today were situated in the middle
of the lake receiving 2.2 times more sediment than the CR1 and
CR2 sampling points situated near the edge of the lake
progression of the vegetation from both east and west, reaching
faster to the CR1 and CR2 sampling points (LOI measurements)
the central and the eastern part of the lake is more exposed to
sedimentation In the present moment
the path of the sediment deposition is in north-south direction,
producing a difference of 42% between the two shores
average sedimentation rates being 0.63 g/cm2y for CR2, 0.92
g/cm2y for CR1 and CRII3 and 1.13 g/cm2y for CRII1 and CRII2
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Conclusions – Effect of anthropic events
CR1
CR2
CRII1
CRII2
CRII3
Average
(g/cm2y)
(g/cm2y)
(g/cm2y)
(g/cm2y)
(g/cm2y)
(g/cm2y)
1940-1972
0.103
0.097
0.445
0.283
0.264
0.238
1972-1983
0.077
0.047
0.110
0.138
0.119
0.098
-25.24%
-51.48%
-75.25%
-51.25%
-54.92%
-58.74%
1972-1989
0.074
0.243
0.115
0.138
0.111
0.136
1989-2013
0.259
0.097
0.497
0.335
0.348
0.307
2.48x
-0.59x
3.32x
1.42x
2.13%
2.25x
Babes-Bolyai University, Faculty of Environmental Science and Engineering
Conclusions – Heavy metals
• although receiving the least amount of sediment in the
present, the CR2 core has been greatly exposed to
heavy metals in the 1985-1990 period and has larger
concentrations of contaminants toward the end of the
sediment core
• on average values being 1.92 times larger before 1989
• exception being Mn, Hg and Cu, metals having an
increasing tendency of 13.57%, 16.74% and 38.92%
• levels of heavy metals are higher in the 1960-70 period
in case of CRII1 and CRII3, showing a decreasing
tendency to the present
Thank you for your attention!
This work was supported by the Ministry of National Education, Romania, under the
grant 61/30.04.2013, PN-II-RU-TE-2012-3-0351 project.