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Ludovic Lesven, Gabriel Billon and Jean-Claude Fischer
Lille, 28 March 2008
Spatial and Temporal Assessment of high Resolution Depth profiles Using novel Sampling Technologies
Vlaams Institute Voor de Zee Université des Sciences et Technologies de Lille Vrije Universiteit Brussel
Programme INTERREG III : STARDUST
Bilan Stardust 2 Main results for Stardust 2
FEDER
INTRODUCTION
Lille, 28 March 2008
Stardust Project has allowed to carry out different studies at water-sediment interface.
More particularly, behaviour of trace metals in relationship with sulphides have been followed in 3 sites: Spierre, Helkjin and Wervik.
In addition, the measurement of metallic fluxes (natural) at water-sediment interface have been realized.
Finally, new analytical tools have been developed:
Solid microelectrodes for trace metals analysis in natural media
DGT – AgI for in situ measurements of sulphides
DIAGENETIC PROCESSES
Lille, 28 March 2008
BOAT
Oxygen reduction: O2 H2O
Denitrification: NO3- N2
Reduction of manganese hydroxides: Mn(III, IV) Mn2+
Reduction of iron hydroxides: Fe(III) Fe2+
Sulfate reduction: SO42- S2- … MS with M= Fe, Pb, Zn, Cu, Cd…
Organic matter
Water
Sediment
?
CORE SAMPLING
Lille, 28 March 2008
Sed.
Wat.
Sed. Pore Wat.Susp. Mat. Wat.
Sequentialextraction
Filtration ina glove-box
ANALYSIS
-ICP-MS-ICP-AES
- Ionic chromatography- Potentiometry
Core 1
pH, Eh(by potentiometry)
O2 (by amperometry)
Core 2
Centrifugation
Cutting in a glove-box with N2
A lot of steps
Real concentration of element?
Sample conservation (oxygen)
NEW ANALYTICAL TOOLS
Lille, 28 March 2008
Analytical development
Solid microelectrodes: Au and Ag-Cu DGT – AgI
In situ measurementsLabile fraction
Good detection limitsCheap method
In situ samplingGood detection limits
High resolution profilesQuick screening for site rich in sulphides
Trace metals Dissolved sulphides
NEW ANALYTICAL TOOLS: solid microelectrodes
Lille, 28 March 2008
Connection
Surface of Ag-Cu/ Audisc after polishing
Coaxial cable
Epoxy glueconductive
No conductiveepoxy glue
Sealing of Ag-Cu/ Au wirein the tip
(furnaceat 500°C)
Ag-Cu/ Au wire830 80µm
1000µm80/ 25µm – Step 1: sandpaper– Step 2: diamond paste(1µm)
Polishing:
ConnectionConnection
Surface of Ag-Cu/ Audisc after polishing
Coaxial cableCoaxial cable
Epoxy glueconductiveEpoxy glueconductive
No conductiveepoxy glue
Sealing of Ag-Cu/ Au wirein the tip
(furnaceat 500°C)
Sealing of Ag-Cu/ Au wirein the tip
(furnaceat 500°C)
Ag-Cu/ Au wire830 80µm
1000µm1000µm80/ 25µm – Step 1: sandpaper– Step 2: diamond paste(1µm)
Polishing: – Step 1: sandpaper– Step 2: diamond paste(1µm)
Polishing:
Analytical development
Solid microelectrodes: Au and Ag-Cu
In situ measurementsLabile fraction
Good detection limitsCheap method
Trace metals
NEW ANALYTICAL TOOLS: solid microelectrodes
Lille, 28 March 2008
Electrode Diameter (µm)
Methods Deposition time (s)
Analytical window (V)
Metals (ppb)
Mn Zn Cd Pb Cu Hg
Ag-Cu 80 DPASV 600 -1.1 to -0.3 - 0.5 0.5 0.5 - -
Au 25 DPASV SWASV
120 -1.1 to 0.65 1 0.2 0.2 0.2 0.2 0.2
Applications:
Monitoring of trace metals in the water compartment
Metal profiles in the porewater sediments
Skogvold O., Mikkelsen O., Billon G., Garnier C., Lesven L., Barthe J.F. (2006). Electrochemical propertiesof silver-copper alloy microelectrodes for use in voltammetric field apparatus, Anal. Bioanal. Chem. ; 384(7-8):1567-77.
Garnier C., Lesven L., Billon G., Magnier A., Mikkelsen O., Pizeta I. (2006). Voltammetric procedure for trace metal analysis in pollutednatural waters using homemade bare gold-disk microelectrodes, Anal. Bioanal. Chem. ; 386(2):313-323.
NEW ANALYTICAL TOOLS: DGT - AgI
Lille, 28 March 2008
Analytical development
DGT – AgI
In situ samplingGood detection limits
High resolution profilesQuick screening for site rich in sulphides
Dissolved sulphides
NEW ANALYTICAL TOOLS: DGT - AgI
Lille, 28 March 2008
Sulphides (µmol/L)
-30
-25
-20
-15
-10
-5
0
5
0 5 10 15
Dep
th (cm
)
DGT - AgI
Core Sampling
Deployment
Calibration Scanning and treatment
Microprofiles of S-2
BEHAVIOUR OF METALS IN SEDIMENT: Sites
Lille, 28 March 2008
Wervik
Spierre
Helkjin
BEHAVIOUR OF METALS IN SEDIMENT: definitions
Lille, 28 March 2008
SO42-
SO32-
S2O32-
H2S, HS-,S2-
S0Organicsulphurs
Sulphuroxydation
Anabolicreduction
MineralizationSulphidesOxydation
Plants,Algae,Mushroom,Bacteria …
Thiobacillus,Sulfolobus…
Sulfato-reductive bacteria,Desulfovibrio …
Fe2+,Pb2+,Zn2+,Cd2+,…
AVS : mainly FeS, but also PbS, CdS…
CRS : mainly Fe2S (and S0 as well…)
DesulforomonasCatabolicreduction
Chlorobium …
SO42-
SO32-
S2O32-
H2S, HS-,S2-
S0Organicsulphurs
Sulphuroxydation
Anabolicreduction
MineralizationSulphidesOxydation
Plants,Algae,Mushroom,Bacteria …
Thiobacillus,Sulfolobus…
Sulfato-reductive bacteria,Desulfovibrio …
Fe2+,Pb2+,Zn2+,Cd2+,…
AVS : mainly FeS, but also PbS, CdS…
CRS : mainly Fe2S (and S0 as well…)
DesulforomonasCatabolicreduction
Chlorobium …
Sulphides cycle
BEHAVIOUR OF METALS IN SEDIMENT: definitions
Lille, 28 March 2008
AVS: Acid Volatile SulphidePredominantly FeS (troillite), not stable, easily oxidized
CRS: Chromium Reducible SulphidePredominantly FeS2 (pyrite), to a lesser extend S0
Toxicity index (TI): ratio of SEM (simultaneously extracted metals) in ppm/AVSWith SEM: Cd + (Co) + (Hg) + Ni + Pb + Zn
Log TI <0: metals only bound to sulphides with low bioavailability
Log TI >0: metals partly bound to labile forms such as carbonates
BEHAVIOUR OF METALS IN SEDIMENT: results
Lille, 28 March 2008
Potential (mV)
-30
-25
-20
-15
-10
-5
0
-450 -350 -250 -150 -50
Dep
th (
cm)
EspierreWervick
Alcalinity (mM/ L)
-30
-25
-20
-15
-10
-5
0
0 10 20 30
Depth
(cm
)
EspierreWervick
Very negative potential values: diagenetic processes
Active mineralization of the labile organic matter
BEHAVIOUR OF METALS IN SEDIMENT: results
Lille, 28 March 2008
Mn (µg/ L)
-16
-14
-12
-10
-8
-6
-4
-2
0
0 800 1600
Depth
(cm
)
EspierreWervick
Fe (µg/ L)
-16
-14
-12
-10
-8
-6
-4
-2
0
0 10000 20000 30000
Dep
th (
cm)
Espierre
Wervick
Sulfides (nM)
-30
-25
-20
-15
-10
-5
0
0 200 400 600 800 1000
Dep
th (
cm)
EspierreWervick
Sulfates (mg/ L)
-30
-25
-20
-15
-10
-5
0
0 50 100 150
Dep
th (
cm)
EspierreWervick
12
Fe(II) and Mn(II) concentrations are weak in the first centimetres in comparison to the Wervick site.
Sulphate reducing bacteria seem to be less active in the Wervick sediment, especially in the first centimetres.
BEHAVIOUR OF METALS IN SEDIMENT: results
Lille, 28 March 2008
AVS (mg/ L)
-30
-25
-20
-15
-10
-5
0
0 1000 2000 3000 4000
Depth
(cm
)
EspierreWervick
CRS (mg/ L)
-30
-25
-20
-15
-10
-5
00 500 1000 1500 2000
Depth
(cm
)
EspierreWervick
log SEM/ AVS
-30
-25
-20
-15
-10
-5
0
-2 -1 0 1
Depth
(cm
)
EspierreWervick
High values of AVS and CRS in Spierre site can explain the low values of iron and manganese at the same depth.
In Spierre sediment the toxicity index is always negative due to the high sulphide amounts.
AVS play an efficient role of trap for trace metals in Spierre sediment (in the first cm).
BEHAVIOUR OF METALS IN SEDIMENT: conclusions
Lille, 28 March 2008
Biogeochemical conditions in the Spierre river different from the 2 other sites:
Very high levels of AVS and CRS
Very low values of log SEM/AVS
Low concentrations of total (DET) and labile (DGT) metals in porewater, especially in upper layer
Remobilisation of trace metals from Spierre sediment to the water column is limited
L. Lesven, Y. Gao, G. Billon, M. Leermakers, J-C. Fischer and W. Baeyens, Influence of sulphides on trace metals mobility in river sediments (in preparation)
CONCLUSION AND PERSPECTIVES
Lille, 28 March 2008
New analytical tools:
DGT – AgI for sulphides Solid microelectrodes (Au and Ag-Cu) for trace metals in water column and sediment
Common sampling in the cross-border rivers (Lys and Escaut) between France and Belgium
Biogeochemistry in the sediments and characterization of the water-sediment interface Metallic fluxes study in the same sites
In perspective:
Continue the metallic fluxes determination (comparison incubation chambers and DGT) Evaluate the metallic bioaccumulation for aquatic organisms during anthropogenic remobilisation in polluted rivers Continue the analytical development (monitoring station, DGT…)