Stabilising inorganic contaminants in soils: Considerations for the use of smart additives

Transcription

1 STARNET Conference Cambridge, England UK Stabilising inorganic contaminants in soils: Considerations for the use of smart additives H. Weigand, C. Gemeinhardt & C. Marb Funded by

2 Background Contaminant stabilisation Technology (market actors) Treatment of contaminated soils in the framework of economic, ecologic & regulatory interests Compliance with standards (regulators) R&D-Project: Methods and evaluation criteria

3 Attributes of smart additives Promote formation of stable contaminant pools Avoid competitive release/secondary contamination Reduce contaminant bioavailability Effective in the per mil to lower percent range React fast relative to pore water residence times Conserve soil hydraulic properties

4 Physico-chemical and biological tests Additive testing with spiked solutions Sequential extractions contaminant binding form analysis Batch equilibrium experiments with stabilised/original soil Bioavailabilty/growths inhibition tests Column experiments, lab- (V ~ 2 L) & pilot-scale (V ~ 2. L) Monitored field trials

5 Suitability of additive Contaminant removal from spiked solution by natural Zeolite Solid phase concentration [meq/kg] Copper measured Langmuir isotherm Lead measured Langmuir isotherm Zinc measured Langmuir isotherm Solution concentration [meq/l] Solution concentration [meq/l] Solution concentration [meq/l]

6 Introduction Methods/Evaluation Accessibility of contaminant pools Binding form analysis by sequential extraction Mn-oxides Organic matter Amorphous Fe-oxides Crystalline Fe-oxides Residual Zinc fraction [%] Zn-contamination? As-contamination Arsenic fraction [%] Mobile Exchangeable

7 Applicability to mixed contamination (I) Batch-equilibrium test, L/S 1: Firing range soil + Fe-rich additives (DeFerrisation Sludge, Goethite) 8 Lead Copper Antimony None 2% 5% 8% 2% 5% 8% None 2% 5% 8% 2% 5% 8% None 2% 5% 8% 2% 5% 8% Solution concentration [mg/l] DFS Goethite DFS Goethite DFS Goethite

8 Applicability to mixed contamination (II) Batch-equilibrium test, L/S 1: Firing range soil + P-fertiliser additives (DiAmmonium Phosphate, Triple Super Phosphate) Solution concentration [mg/l] Lead Copper Antimony None.5% 1.% 2.%.5% 1.% 2.% None.5% 1.% 2.%.5% 1.% 2.% None.5% 1.% 2.%.5% 1.% 2.% DAP TSP DAP TSP DAP TSP

9 Applicability to mixed contamination (III) Additive-induced modification of solution chemistry: Indirect copper mobilisation 9 4 ph DOC ph of batch extract [ ] DOC concentration [mg/l] ph DOC Cu 5.5% 1.% 2.%.5% 1.% 2.% None DAP TSP

10 Response of biota Growth inhibition of Lemna minor by batch extracts of stabilised smelter soil 6 Lemna frond area [mm²] Control solution Zeolite fine Zeolite coarse Goethite Original soil Potassium dihydrogen phosphate Iron(II)sulphate Phosphoric acid Additive Σ Cd, Zn, Pb [mg/l] Zeolite fine.28 Zeolite coarse.25 Goethite.3 Untreated.31 KH2PO 4.18 FeSO Day Day 4 Day 7 H3PO

11 Effectivity: (Transient) flow conditions FeSO 4 -treated Emerald Green site: Stabilisation vs. mobilisation 6 1 Arsenic [mg/l] Untreated Treated 2 nd irrigation period Cobalt, Nickel [mg/l] Untreated Co Treated Co Untreated Ni Treated Ni 2 nd irrigation period Pore volumes exchanged [ ] Pore volumes exchanged [ ]

12 Introduction Methods/Evaluation Contaminant pools Shift of As binding form pattern induced by FeSO 4 -treatment 4 3 Before treatment After treatment Arsenic fraction [%] 1 Mobile Exchangeable Mn-oxides Organic matter Amorphous Fe-oxides Crystalline Fe-oxides Residual

13 Soil hydraulic properties Dispersivity: tracer breakthrough 1. Dimensionless tracer concentration Untreated observed Untreated fit Treated observed Treated fit + saturated conductivity + soil water retention curve Time [min]

14 Conclusions Screening for non-target componds: Adverse side effects Binding form pattern: Pre- and post-treatment benchmark Bioassays: Combined effects of contaminant and additive Transport studies: Applicabilty under dynamic conditions Identifying smart additives requires array of tests