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…)