1. 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, Romania 2Interdisciplinary Research Institute on Bio-Nano-Sciences, Babeş-Bolyai University, Cluj-Napoca, Romania 3Faculty of Geography, University of Bucharest, Bucharest, Romania

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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 re-analyzed
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

9. Sampling site: The Cruhlig Lake
Marine part of the Danube Delta
South to the Sf. Gheorghe branch
Formed 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

10. Physical parameters
Babes-Bolyai University, Faculty of Environmental Science and Engineering

11. Carbon content
Babes-Bolyai University, Faculty of Environmental Science and Engineering

12. 226Ra and 210Pb activity concentration
Babes-Bolyai University, Faculty of Environmental Science and Engineering

13. Ages of the sediment layers
Babes-Bolyai University, Faculty of Environmental Science and Engineering

14. Sedimentation rates
Babes-Bolyai University, Faculty of Environmental Science and Engineering

15. 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

16. Heavy metal concentrations CRII1 & CRII3
Babes-Bolyai University, Faculty of Environmental Science and Engineering

17. 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 ( , , and ) 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

18. Conclusions – Effect of anthropic events
CR1
(g/cm2y)
CR2
CRII1
CRII2
CRII3
Average
0.103
0.097
0.445
0.283
0.264
0.238
0.077
0.047
0.110
0.138
0.119
0.098
-25.24%
-51.48%
-75.25%
-51.25%
-54.92%
-58.74%
0.074
0.243
0.115
0.111
0.136
0.259
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

19. 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 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 period in case of CRII1 and CRII3, showing a decreasing tendency to the present

20. Thank you for your attention!
This work was supported by the Ministry of National Education, Romania, under the grant 61/ , PN-II-RU-TE project.