Lame cumulée (m)Cumulated Infiltration (m)

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Evaluation of plant effects on the mobility of heavy metals in an ancient mine phytoremediation action.

The case of « The Avinières » at St Laurent le Minier (F)

Navel A., Spadini L., Gaudet J.P., Schneider J., Vince E., Sebastianutti S. and J.M.F. Martins

Univ. Grenoble France

L T H E

Photo : JC Cleyet-MAREL, LSTM

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Context : mining activity in France

Numerous active or abandoned mines

Orphan sites polluted with metals :

hot-spots of heavy metals (x100 to x1000 > norms)

Management of these sites by ADEME :

Reduction of the risk associated with metals (frequently close to rivers) through different approaches : Pollution control (excavation, extraction…), Confinement, Phytoremediation (Stabilization) …

These metals are toxic in the environment…

• Contamination of soils and the food chain.

… and for human health

• Bioaccumulation

• Toxic effects at short and/or long term.

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SYMETAL PROJECT : French ANR

Phytoremediation of the abandoned Zinc mine

of St Laurent le Minier.

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What is phytoremediation ?

Soil fixation

Retention in rhizosphere Transfer to leaves and stem

Transfer to groundwater

Phyto-extraction

Metal-rich

particles/debris can fly away

Phyto-stabilisation

Metal Example of natural vegetation

Petra Alba Zinc-Mine abandoned in the 16th century

Accelerating nature action…

!!! Risk evaluation

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200’000 tons of Zn ore extracted Mine closed in the 1950s

Health problems : Children victim of Saturnism (presence of Zn and Pb around houses).

Study site : Mine of the « Avinières »

Tailing pounds

Phytostabilization

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Study of the effect of phyto-stabilisation

on metals mobility (Zn, Pb et Cd)

Natural meteorological conditions

Optimization of the plant cover in small plots in real situation : Mycorhization and

nodulation (N fixation)

SYMETAL Project (ANR CESA) :

Mine tailings rhizo-stabilization by METALlicolous plants

associated to SYMbiotic micro-organisms.

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[Me]

(mg/kg)

Limit [Me]

(mg/kg soil)

Cd 745 2

Pb 39’305 100 Zn 129’032 300

7 pH,

Alcalinity (acid-base titrimetry) Anions (Ionic chromatography) Cations (ICP-OES)

COD (TOC analysor) MEB, …

Analyses:

Lysimeter set up

ISCO Collector 20 cm

30 cm

5 cm

23 cm

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The model plants : tolerant to metals

Anthyllis vulneraria

Conditions tested :

No plant 1 plant 2 plants 3 plants

Mesorhizobium Mycorhization

Control

Anthylis vulneraria Anthylis vulneraria Anthylis vulneraria

Festuca Festuca

Koeleria

+ Festuca sp. + Koeleria sp.

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RESULTS :

3 species Controls

1 species

2 species

Sampling pit

Controls

Anthyllis + Festuca + Koeleria 1P 2P 3P

Monitoring over 3 years (04/2012 to 04/2015)

+ biannual metal leaching experiments

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Plant cover installation and persistence

Anthyllis (1P)

Anthyllis + Festuca (2P)

Anthyllis + Festuca + Koeleria (3P)

09-2012

04-2013

09-2013

04-2014 09-2012

04-2013

09-2013

04-2014

09-2014 09-2014

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Lame cumulée (m)

0 0,02 0,04 0,06 0,08 0,1 0,12 0,14

0 200 400 600 800 1000

Temps (s)

Lame cumulée (m)

Essai 1 Essai 3 Calcul 1 essai 3 Calcul 2 essai 3

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Characterization of hydrodynamic parameters : Beerkan Test

(Comsol modeling)

Hydraulic conductivity of the undisturbed material : Ks = 1.1 10^-5 m s^-1

Time (s)

Cumulated Infiltration (m)

Time (s)

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0,0E+00 2,0E-05 4,0E-05 6,0E-05 8,0E-05 1,0E-04

0 5000 10000 15000 20000

Temps (sec) Vitesse d'infiltration (m.sec-1 )

0,0E+00 2,0E-05 4,0E-05 6,0E-05 8,0E-05 1,0E-04

0 5000 10000 15000 20000

Temps (sec)

0 5000 10000 15000 20000

Temps (sec) 0,0E+00

0 5000 10000 15000 20000

Temps (sec)

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Hydrodynamic parameters characterization : Beercan tests

1 Plant 2 Plants 3 Plants

09-2012 04-2013 09-2013 04-2014

Hydraulic conductivity is slightly higher in lysimeters / in situ

No significant evolution of Ks during the 2 years, whatever the number of plant species installed

Control

Disturbed material in lysimeters : Ks ≈ 2.0 10

^-5

m.s

^-1

Infiltration ≈ 0,5 m of water

Water velocity ( m/s)

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RESULTS :

2 years evolution of leachates composition

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6 6,5 7 7,5 8

2012 Sept

2013 April

2013 Sept

2014 April

pH

2012 Sept

2013 April

2013 Sept

2014 April

2014 Sept 2012

Sept

2013 April

2013 Sept

2014 April

2014 Sept 2012

Sept

2013 April

2013 Sept

2014 April

2014 Sept

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Control 1 Plant 2 Plants 3 Plants

Decrease of pH in all lysimeters :

Due to tailings mixing and oxidation, compost addition…

No significant effect of plant covers on pH

Temporal evolution of pH in lysimeters leachates

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0 1000 2000 3000 4000 Volume écoulé (mL)

0 5 10 15 20 25 30 35 40 45

0 1000 2000 3000 4000

Volume écoulé (mL) [NO3-] (mg.L-1)

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Temporal evolution of [NO

₃^-

] in lysimeter leachates

Detection of [NO₃^-] in all lysimeters : due to inital addidtion of compost + fertilizer

High [NO₃^-] in « 1 Plant » after the flowering (09-2013) :

oxydation of nitrogen fixed by Mesorhizobium > to plant consumption

Nitrogen consumption by Festuca and Koeleria species

04-2013 09-2013 04-2014

0 1000 2000 3000 4000

Volume écoulé (mL) 0

5 10 15 20 25 30 35 40 45

0 1000 2000 3000 4000

Volume écoulé (mL)

09-2013

[NO3] (mg/L)

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0 1000 2000 3000 Volume écoulé (mL)

0 1000 2000 3000

0 20 40 60 80

0 1000 2000 3000

[Zn2+] (mg.L-1)

Volume écoulé (mL) 0

0,5 1 1,5 2 2,5

0 1000 2000 3000

[Cd2+] (mg.L-1)

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Temporal evolution of [Cd] and [Zn] in lysimeter leachates

[Me] >>> to potability norms

Control : increase of [Cd²⁺] and [Zn²⁺] probably due to pH increase Beneficial plant effect on Cd and Zn mobilization

Initial [Me]

Zinc

Potability Lim.

Cadmium

04-2013 09-2013 04-2014 09-2014

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0 1000 2000 3000 Volume écoulé (mL)

0 1000 2000 3000

0,01 0,1 1 10

0 1000 2000 3000

[Pb2+] (mg.L-1)

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[Pb] highly > water potability limit (0,01mg/L)

No temporal evolution of [Pb] in all conditions (vegetated or not) No significant effect of the plant cover on Pb leaching

[Pb] Initial

Potability Lim.

Relates to a particle facilitated transport process of lead

Temporal evolution of [Pb] in lysimeter leachates

04-2013 09-2013 04-2014 09-2014

Pb, Fe, O, S, Zn

Fe, O

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CONCLUSIONS :

The study permitted to optimize conditions of ore residues phytostabilization !

pH modification in all situations: acidification due to compost addition … No significant modification of material hydrodynamic properties

Leached metal concentration are always >>> potability norms

No modification of Pb mobility.

Better cover installation when A. vulneraria is associated with other plants

3P > 2P > 1P (observed in ancient mines) Mutual benefits

Strong limitation of Cd and Zn mobility in the lysimeters with 2 or 3 species

Leached metal concentration remain > potability norms

Effect of plant cover installation on metals mobility :

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Mr Guy Delmot

LSTM

TransPore Group

L T H E

Pau (F)

Montpellier (F)