sedimentation dynamics and heavy metal pollution history in cruhlic lake, danube delta, romania...

Sedimentation Dynamics And Heavy Metal Pollution History in Cruhlic Lake, Danube

Delta, RomaniaSimon 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

• 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)

Aims and Scopes


• 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

The 210Pb dating method


Models for 210Pb assessmentCIC 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 layerCS 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


• 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)

γ-spectrometry


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 re-analyzed

• The measured heavy metals being Li, Mg, Al, K, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Hg and Pb


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

Physical parameters


Carbon content


226Ra and 210Pb activity concentration


Ages of the sediment layers


Sedimentation rates


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 ,

Heavy metal concentrations CRII1 & CRII3


CRII1

CRII3

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


Conclusions – Effect of anthropic events

CR1

(g/cm2y)

CR2

(g/cm2y)

CRII1

(g/cm2y)

CRII2

(g/cm2y)

CRII3

(g/cm2y)

Average

(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


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.

sedimentation dynamics and heavy metal pollution history in cruhlic lake, danube delta, romania...

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