Using passive DGT samplers for integrative measurement of metals in groundwater of industrial sites S.MAGHE-CHAUVIN

Transcription

1 Using passive DGT samplers for integrative measurement of metals in groundwater of industrial sites S.MAGHE-CHAUVIN

2 What s a DGT? DGT (Diffusive Gradient in Thin films) Passive sampler Targets: labile solution species (available to biota) cationic metals (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn), oxyanions (P, As(V), Mo and V), some polar organic compounds (antibiotics, ). From DGT Research 2

3 What s a DGT?.45 µm filtration TOTAL metal Dissolved metal Dissolved INORGANIC metal Dissolved ORGANIC metal Labile metal Intersol 216 : DGT-H2O-STR 3

4 Project Goal of the project: to use DGT as monitoring tools on industrial sites 3 questions: Exposition time: how long it could be on contaminated sites? Using DGT in groundwater: a relevant tool for vertical stratification study? DGT and grab sampling: could DGT replace successfully frequent water samples? 4

5 Experimental site Two locations with Cd and Zn contamination : Downstream section of a dump with hydrometallurgical processing residues -> PzA; Downstream section of a sealed garbage dump (French : ISDD) -> PzB. Grab sample PzA PzB Borehole depth (m) ph Cadmium (μg/l) 3 42 <5 Zinc (μg/l) Lead (μg/l) <5 1 Manganese (μg/l)

6 Exposure time How long could a DGT stay in such contaminated water? 1) Speciation simulation 2) In situ saturation study with DGT 6

7 Exposure time - Simulation Speciation simulation using Vminteq 7

8 Exposure time - Simulation Speciation simulation using software -> Lead and Copper are more likely to be linked with organic matter : less labile PzA (C metals = mg/l) DGT simulated saturation.78 mm diffusive gel 6 hours 1.96 mm diffusive gel 12 hours PzB (C metals = µg/l) DGT simulated saturation.78 mm diffusive gel 14 days 1.96 mm diffusive gel More than 28 days 8

9 Exposure time In situ In situ DGT saturation test (1.96mm diffusive gel) in PzB for monitoring W (ng) Cadmium accumulated in DGT y =.241x R² = t (days) 6 W (ng) Nickel accumulated in DGT y = x R² = t (days) 7 W (ng) Cobalt accumulated in DGT y = 2.313x R² = W (ng) Zinc accumulated in DGT y = 18.27x R² = t (days) t (days) > NO SATURATION even during 28 days 9

10 Exposure time Conclusions : The more thicker the diffusive gel is, the longer the DGT could stay into polluted water. Contaminated water with several metals mg/l -> exposition time for a few hours (PzA) Contaminated waters µg/l -> exposition time for several weeks (PzB) 1

11 Project 3 questions: Exposition time: how long it could be on contaminated sites? Using DGT in groundwater: a relevant tool for vertical stratification study? DGT and grab sampling: could DGT replace successfully frequent water samples? 11

12 Depth (m) Stratification in groundwater Cd (mg/l) -1 Zn (mg/l) Pb (mg/l) -2 Water level (-2.58 m) -3 Water arrivals Borehole s end (-6.1 m) -7 Concentration of labile metals (C DGT in mg/l) 12

13 Depth (m) Depth (m) Stratification in groundwater Depth (m) Depth (m) Multiparameters probe ph Redox potential Conductivity (µs/cm) Temperature ( c)

14 Stratification in groundwater 14

15 Stratification in groundwater Conclusions : Cohence with vertical variations of ph and conductivity measured by multi parameters probe Relevant vertical profile of metals using DGTs Intersol 216 : DGT-H2O-STR 15

16 Project 3 questions: Exposition time: how long it could be on contaminated sites? Using DGT in groundwaters: a relevant tool for vertical stratification study? DGT and grab sampling: could DGT replace successfully frequent water sampler? 16

17 Comparison between DGT and water analysis DGTs and installation of an automatic sampler : water samples every 6 hours for 2 weeks during 6 months 17

18 Cd concentration (μg/l) Comparison DGT versus water analysis Pluviometry (mm) Cadmium evolution in a borehole /2/15 16/3/15 6/4/15 27/4/15 18/5/15 8/6/15 29/6/15 2/7/15 Labile Cd in water - DGT Dissolved Cd in water pluviometry 18

19 Zn concentration (μg/l) Comparison DGT versus water analysis Pluviometry (mm) Zinc evolution in a borehole /2/15 16/3/15 6/4/15 27/4/15 18/5/15 8/6/15 29/6/15 2/7/15 Labile Zn in water - DGT Dissolved zinc in water pluviometry 19

20 Pluviometry (mm) Comparaison DGT versus water analysis Water level in piezometer (m) 8 Pluviometry and water level in a borehole water level in Pz DGT position in Pz pluviometry per period daily pluviometry /24/215 2/21/215 3/21/215 4/18/215 5/16/215 6/13/215 7/11/215 8/8/215 9/5/215 2

21 Comparison DGT versus water analysis Conclusions : Global good correlation between labile metals concentration with DGT and dissolved metals by analysis Specific reaction during short rainfall: metals are dissolved but not labiles (hypothesis to be confirmed) Advantage of DGT: the LOQ is lower for DGT (integrative samplers) Intersol 216 : DGT-H2O-STR 21

22 Project Recall of the 3 questions: Exposition time: how long it could be on contaminated sites? > weeks in contaminated waters (µg/l) versus hours in very high contaminated water (mg/l) Using DGT in groundwater: a relevant tool for vertical stratification study? > Stratification study : good vertical correlation with multi parameters log 22

23 General Conclusions DGT and grab sampling: could DGT replace successfully frequent water samples? > DGT versus water analysis : coherent results between dissolved metals and labiles metals concentrations but maybe different reactions when short and intense rainfall. -> The DGT is a useful integrative sampler which can be used for vertical profile in underground water or monitoring even on contaminated sites! Intersol 216 DGT-H2O-STR 23

24 Questions Contact: MINELIS Ségolène MAGHE-CHAUVIN