1 hp1: a coupled numerical code for variably saturated water flow, solute transport and...
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HP1: A coupled numerical code for variably saturated water flow, solute
transport and biogeochemical reactions in soils and sediments
D. Mallants, D. Jacques, J. Šimůnek, and
M.Th. van Genuchten
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HP1: HYDRUS1D-PHREEQC
Possibilities of the code
Benchmarking PCE-dissolution
Migration of decay chain of adsorbing contaminants during precipitation/evaporation
Illustration of ‘coupled’ effects TNT degradation under steady state flow
Cd leaching in an acid podzol: lysimeter experiments
Long-term transient flow and transport of major cations and heavy metals in a soil profile
U-transport in agricultural field soils
Outline
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HP1: HYDRUS1D-PHREEQC
Possibilities of the code
Benchmarking PCE-dissolution
Migration of decay chain of adsorbing contaminants during precipitation/evapotranspiration
Illustration of ‘coupled’ effects TNT degradation under steady state flow
Cd leaching in an acid podzol: lysimeter experiments
Long-term transient flow and transport of major cations and heavy metals in a soil profile
U-transport in agricultural field soils
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Simulation Tool
A Coupled Numerical Code forVariably Saturated Water Flow,
Solute Transport andBiogeochemistryin Soil Systems
Simulating water flow, transport and bio-geochemical reactions in environmental soil quality problems
Biogeochemical modelPHREEQC-2.4
Flow and transport modelHYDRUS-1D 2.0
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Coupling procedure
Coupling method: non-iterative sequential approach (weak coupling)
Within a single time step: First solve water flow equation (HYDRUS)
Second: solve heat transport equation Then solve convection-dispersion equation for
solute transport for element master/primary species (inert transport) (HYDRUS)
Finally solve for each element, calculate speciations, equilibrium reactions, kinetic reactions, … (PHREEQC)
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HP1: HYDRUS1D-PHREEQC
Possibilities of the code
Benchmarking PCE-dissolution
Migration of decay chain of adsorbing contaminants during precipitation/evapotranspiration
Illustration of ‘coupled’ effects TNT degradation under steady state flow
Cd leaching in an acid podzol: lysimeter experiments
Long term transient flow and transport of major cations and heavy metals in a soil profile
U-transport in agricultural field soils
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1D FE water flow in variably-saturated media 1D FE transport of multiple solutes by CDE 1D heat transport Mixed equilibrium / kinetic biogeochemical
reactions Aqueous speciation (reactions in pore-water) Cation exchange (on clay, organic matter, …) Surface complexation (e.g. iron oxyhydroxides) Mineral dissolution / precipitation Any kinetic reactions (oxidation/reduction,
(bio)degradation, dissolution/precipitation)
HP1 – model features
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HP1 examples
Transport of heavy metals (Zn2+, Pb2+, and Cd2+) subject to multiple cation exchange
Transport with mineral dissolution of amorphous SiO2 and gibbsite (Al(OH)3)
Heavy metal transport in a medium with a pH-dependent cation exchange complex
Infiltration of a hyperalkaline solution in a clay sample (kinetic precipitation-dissolution of kaolinite, illite, quartz, calcite, dolomite, gypsum, …)
Long-term transient flow and transport of major cations (Na+, K+, Ca2+, and Mg2+) and heavy metals (Cd2+, Zn2+, and Pb2+) in a soil profile.
Kinetic biodegradation of TNT (multiple degradation pathways)
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Cycling of radionuclides/metals in soil-plant systems Heterogeneous physical/chemical properties Water flow under rainfall - evapotranspiration
conditions Root growth and water uptake Microbiological growth Degradation of organic matter with
radionuclide/metal release Transport/adsorption/decay Uptake of radionuclides/metals by plants
Typical application and processes involved
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HP1: HYDRUS1D-PHREEQC
Possibilities of the code
Benchmarking PCE-dissolution under steady-state flow conditions
Migration of decay chain of adsorbing contaminants during precipitation/evapotranspiration
Illustration of ‘coupled’ effects TNT degradation under steady state flow
Cd leaching in an acid podzol: lysimeter experiments
Long-term transient flow and transport of major cations and heavy metals in a soil profile
U-transport in agricultural field soils
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Test I: PCE degradationPCE degradation pathway
(Schaerlaekens et al., Hydrological Processes,
1999) PCE, TCE: organic contaminant
Solvent, degreasing agent, dry-cleaning
VC: vinylchloride: carcinogenic
Perchloroethylene Trichloroethylene
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Test I: PCE degradation
Comparison with analytical solution
0 10 20 30D istance (m )
0
0.2
0.4
0.6
0.8
1
Co
nce
ntr
atio
n (
mo
le /
l)
Analytica l so lu tion(Sun et a l., 2004)
H P1
PC E
TC E
0 10 20 30D istance (m )
0
0.05
0.1
0.15
0.2
0.25
Co
nce
ntr
atio
n (
mo
le /
l) cis-DC E
trans-DCE
1,1-DCE
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Test II: Migration of decay chain species
Problem definition
Three contaminants (Cont_a, Cont_b, Cont_c) First-order degradation
Cont_a Cont_b Cont_c
Linear (Cont_a)/ nonlinear Freundlich (Cont_b, Cont_c) sorption
Homogeneous soil profile
(Soil covered with grass (rooting depth 20 cm))
Atmospheric boundary conditions (time dependent)
HP1 comparison with HYDRUS-1D
nF = 1 nF = 0.9 nF = 0.8
µ1= 0.005 d-1 µ2= 0.06 d-1 µ3= 0.02 d-1
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Test II: Migration decay chain species
Water flow boundary conditions
0 1 2 3T im e (d)
0
50
100
150
200
Cu
mu
lativ
e fl
ux
(cm
/ m
²)
P
T p
E p
T a
E a
P - E p
P - E a
(y)
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Test II: Migration decay chain speciesWater content profiles
0.05 0.1 0.15 0.2 0.25 0.3 0.35w ater content
-100
-80
-60
-40
-20
0
Dep
th (
cm)
H YD R U S-1D
H P1
225 d465 d
630 d
840 d
1096 d
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Test II: Migration decay chain speciesConcentration-depth profiles
0 0.5 1 1.5 2 2.5C onta (m ole / l)
-100
-80
-60
-40
-20
0
Dep
th (
cm)
225 d
465 d630 d
840 d
1096 d
0.00 0.02 0.04 0.06 0.08 0.10 0.12C ontb (m ole / l)
-100
-80
-60
-40
-20
0
Dep
th (
cm)
225 d
465 d
630 d
840 d
1096 d
H YD R U S-1D
H P1
BC: Step-function input for Cont_a (1 M) & Cont_b (0.1 M)Leaching
Breakthrough
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0 20 40 60 80 100D e p th (cm )
0
0.2
0.4
0.6
0.8
1
Co
nce
ntr
atio
n (
mo
l/l)
0 20 40 60 80 100D e p th (cm )
0
0.02
0.04
0.06
0.08
0.1
Co
nce
ntr
atio
n (
mo
l/l)
0 20 40 60 80 100D e p th (cm )
0
0.02
0.04
0.06
0.08
0.1
Co
nce
ntr
atio
n (
mo
l/l)
H YD R U S-1D
H P1
Conta
Contb
Contc
250 d500 d
1000 d
Test II: Migration decay chain species
Concentration-time profiles
Excellent agreement between HP1
and HYDRUS
Performance criterion for HP1
becomes more strict: Pe×Cr < 0.4
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HP1: HYDRUS1D-PHREEQC
Possibilities of the code
Benchmarking PCE-dissolution under steady-state flow conditions
Migration of decay chain of adsorbing contaminants during precipitation/evapotranspiration
Illustration of ‘coupled’ effects TNT degradation under steady-state flow
Cd leaching in an acid podzol: lysimeter experiments
Long-term transient flow and transport of major cations and heavy metals in a soil profile
U-transport in agricultural field soils
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Transport of TNT and its Daughter Products
•Soil profile: 100 cm, loam, Ks=1 cm/h, 10 days•TNT in top 5 cm of soil: 1 mg/kg (6.61e-6 mol)•TNT dissolution: rate = 4.1 mg/cm2/hour (1.8e-5 mol/cm2/hour)•Solid 2ADNT at equilibrium with solution, 2ADNT solubility = 2,8 g/L Sorption (instantaneous)
Adsorption coefficients Kd [L/kg]:•TNT 3•2ADNT 5•4ADNT 6•TAT 0
Degradation•TNT -> 66% is transformed in 2ADNT and 34% is to 4ADNT Transformation constants [1/hour]•TNT 0.01•2ADNT 0.006•4ADNT 0.04
4ADNTTNT TAT
2ADNT
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Transport of TNT and its Daughter Products
0
20
40
60
80
100
0.E+00 1.E-07 2.E-07 3.E-07 4.E-07
Concentration [mol/L]
Dep
th [c
m]
2 d
4
6
8
10
0
20
40
60
80
100
0.E+00 2.E-09 4.E-09 6.E-09 8.E-09 1.E-08 1.E-08
Concentration [mol/L]
Dep
th [c
m]
2 d
4
6
8
10
2ADNT
0
20
40
60
80
100
0.E+00 3.E-09 5.E-09
Concentration [mol/L]
Dep
th [c
m]
2 d
4
6
8
10
4ADNT
0
20
40
60
80
100
0.E+00 3.E-09 5.E-09
Concentration [mol/L]
Dep
th [c
m] 2 d
4 6 810
TAT
TNT
•This example indicates that ground water may be more vulnerable to leaching of TNT daughter products (notably TAT) than of the parent compound itself, and that monitoring for the daughter products may provide an early warning of possible TNT leaching.
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Cd leaching in acid podzol Introduction
Nothern region of Belgium: historical contamination of soils with Cd, Pb, Cu, Zn by atmospheric deposition originated from the non-ferro industry (historical contamination, beginning 20th century)
Risk of flooding with water containing increased salt concentrations
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Cd leaching in acid podzol Objectives
To describe the leaching of major cations, Zn and Cd from a lysimeter after application of an increased salt concentration (tracter test)
To assess the effect of increased salt concentrations (CaCl2) on Cd leaching using a new coupled reactive transport model HP1
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Cd leaching in acid podzol Problem definition (Seuntjens et al., 2000)
Podzol soil (Kempen) contaminated with heavy metals (Cd, Zn, Pb)
Lysimeter (80-cm-diameter, 100-cm-long)
Equipped with TDR probes Bottom: grid based wick sampler system Displacement exp.: boundary conditions
Time (d) CaCl2 (mol/l)
0-27.9 0.00527.9-28.9 0.05 (tracer)28.9-80 0.005
Bh2
A
E
C1
C2
CEC (meq/kg)
24.4
11.7
83.9
62.9
14.4
7.4
Bh1
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Cd leaching in acid podzol Leaching experiment set-up
Leachate collectors
TDR probes
Cable
tester
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Components in solution: H, Ca, Na, K, Mg, Al, Cl, Br, Cd, Zn
Speciation reactions in soil solution Complexation reactions of Zn, Cd with OH-,
Cl-:
Cd(OH)+, Cd(OH)2, Cd(OH)3-, Cd(OH)3
2-
Cd(Cl)+, Cd(Cl)2, Cd(Cl)3-, Cd(Cl)3
2-
Cd leaching in acid podzol Leaching experiment modelling (1)
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Ion exchange reactions (solid phase interaction) Half reactions (X-: exchange complex):
H+ + X- = HX Ca2+ + 2 X- = CaX2
H, Ca, Na, K, Mg, Cd, Zn Equilibrium constants are adapted to fit the
measurements (site-specific Log_K values)
Equilibrium with gibbsite (Al(OH)3)
Cd leaching in acid podzol Leaching experiment modelling (2)
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Cd leaching in acid podzol Multi-component modelling results (1)
0 20 40 60 80T im e (d)
3
4
5
6
pH
0 20 40 60 80T im e (d)
0
1
2
3
4
Al (
mm
ol/l
)
0 20 40 60 80T im e (d)
0
5
10
15
20
Cl (
mm
ol/l)
0 20 40 60 80T im e (d )
0
1
2
3
4
5
Ca (m
mol/l
)
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Cd leaching in acid podzol Multi-component modelling results (2)
0 20 40 60 80T im e (d)
0
0.25
0.5
0.75
1
Na
(m
mo
l/l)
0 20 40 60 80T im e (d)
0
0.1
0.2
0.3
K (
mm
ol/l
)
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Cd leaching in acid podzol Multi-component modelling results (3)
0 20 40 60 80T im e (d)
0x10 0
2x10 - 3
4x10 - 3
6x10 - 3
8x10 - 3
1x10 - 2
Cd
(m
mo
l/l)
0 20 40 60 80T im e (d)
0x10 0
1x10 - 1
2x10 - 1
3x10 - 1
Zn
(m
mo
l/l)
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Cd leaching in acid podzol Multi-component modelling results (4)
0 20 40 60 80T im e (d)
0x10 0
2x10 - 3
4x10 - 3
6x10 - 3
8x10 - 3
1x10 - 2
Cd
(m
mo
l/l)
0 20 40 60 80T im e (d )
0x10 0
1x10 0
2x10 0
3x10 0
4x10 0
Ca
(m
mo
l/l)
pulse 0.05 M CaC l2 - com plexation/com petition
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Cd leaching in acid podzol Cd remobilisation due to complex
formation
0 20 40 60 80T im e (d)
0x10 0
2x10 - 3
4x10 - 3
6x10 - 3
8x10 - 3
1x10 - 2
Cd
(m
mo
l/l)
0 20 40 60 80T im e (d )
0x10 0
1x10 0
2x10 0
3x10 0
4x10 0
Ca
(m
mo
l/l)
pulse 0.05 M CaC l2 - com plexation/com petition
0 20 40 60 80T im e (d )
0x10 0
2x10 - 3
4x10 - 3
6x10 - 3
8x10 - 3
1x10 - 2
Cd
(m
mo
l/l)
0 20 40 60 80T im e (d )
0x10 0
1x10 0
2x10 0
3x10 0
4x10 0
Ca
(m
mo
l/l)
pulse 0 .05 M CaC l2 - com plexation/com petition
pulse 0 .005 C aC l2 - less com plexation/com petition
0 20 40 60 80T im e (d)
0x10 0
2x10 - 3
4x10 - 3
6x10 - 3
8x10 - 3
1x10 - 2
Cd
(m
mo
l/l)
0 20 40 60 80T im e (d )
0x10 0
1x10 0
2x10 0
3x10 0
4x10 0
Ca
(m
mo
l/l)
pulse 0.05 M CaC l2 - com plexation/com petition
pulse 0.005 CaC l2 - less com plexation/com petition
pulse 0.05 CaBr2 - com petition (no com plexation)
CdCln
2-n
Complexation or competition?
Complexation!
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Cd leaching in acid podzol Conclusion
Increased Cd mobilization due to exchange Ca-Cd complexation with Cl- (most important)
Geochemical speciation models required (instead of e.g. Kd approach)
HP1: allows for transient flow conditions
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HP1: HYDRUS1D-PHREEQC
Possibilities of the code
Benchmarking PCE-dissolution
Migration of decay chain of adsorbing contaminants during precipitation/evapotranspiration
Illustration of ‘coupled’ effects TNT degradation under steady state flow
Cd leaching in an acid podzol: lysimeter experiments
Long term transient flow and transport of major cations and heavy metals in a soil profile
U-transport in agricultural field soils
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Geochemical transport under transient variably-saturated flow
Cycling of metals in soil-plant systems Heterogeneous physical/chemical properties Water flow under rainfall - evaporation
conditions Root growth and water uptake Metal transport/adsorption/speciation Uptake of metals by plants Degradation of organic matter with metal
release
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steady-state
actual surface flux
= P-ETact
potential surface flux
= P-ETpot
0 0 0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8T im e (year)
0
100
200
300
Cu
mu
lativ
e in
filtr
atio
n (
cm)
Long-term transient flow and transport Transient infiltration at surface
Bh1
AE
Bh2C1
C2
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Long-term transient flow and transport Effect of transient infiltration on Cd migration
Site 1
Site 2
Site 6
...
O rganic M atter
C ation E xchange
A queous S pecia tion
W ater Phase A ir P hase
HKHM g
C a
C d
HN aHH
C a
Zn
H
HHHHHHHHH
H +
H +
ZnC l2
H +
H +
H +
N a +
C d 2+
H +
B r -
O H -
H +
C l-
C dC l+
H +
N aO H
H +
H +
H +
H +
K +
H +
H +
Zn 2+
Geochemical Reactions: Multisite cation exchange
2 3 4 5 6p H
0
0.01
0.02
0.03
0.04
0.05
Ne
ga
tive
ch
arg
eo
rga
nic
ma
tte
r(m
eq
/g s
oil) A -horizon
E-horizon
Podzol soil
•Multi-site exchange complex
•CEC: organic matter
•CEC=f(pH)
•Complex formation: Cl-metals
•Variable infiltration
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Long-term transient flow and transport Cd mobility and bio-availability as function of
, pH, Cl- (1)
pH
1975 1976 1977 1978Time (year)
-6
-4
-2
0
De
pth
(c
m)
3
3.2
3.4
3.6
3.8
4
4.2
4.4
Time (year)
Water Content
1975 1976 1977 1978
-6
-4
-2
0
De
pth
(c
m)
0.02
0.06
0.1
0.14
0.18
0.22
0.26
Log(Aqueous Cd) (mmol/kg soil)
1975 1976 1977 1978
Time (year)
-6
-4
-2
0
De
pth
(c
m)
-6.6
-6.2
-5.8
-5.4
-5
-4.6
-4.2
-3.8Log(Cl) (mmol/kg soil)
1975 1976 1977 1978
Time (year)
-6
-4
-2
0
De
pth
(c
m)
-2.3
-2
-1.7
-1.4
-1.1
-0.8
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Long-term transient flow and transport Cd mobility and bio-availability as function of
, pH, Cl- (2)
Bh1Bh2
AE
C1
C2
0.2
0.24
0.28
0.32
0.36
0.4
Wa
ter
con
ten
t3
3.5
4
4.5
5
pH
pH
Water Content
1972 1974 1976 1978 1980 1982Time (year)
Cl
Aq
ue
ou
s C
d
Cd
Cl10-4
10-5
10-6
10-2
10-3
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Long-term transient flow and transportConclusions
Temporal variability of physical soil variables (θ) results in temporal variability in geochemical variables (pH, Cl-,…)
Applied to heavy metal mobility and bio-availability: Water content variations linearly related to pH
and inversely to Cl- variations pH inversely related to dissolved metal
concentration (multi-site cation exchange f(pH)) Cl- concentration linearly related to dissolved
metal concentration (complex formation)
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HP1: HYDRUS1D-PHREEQC
Possibilities of the code
Benchmarking PCE-dissolution under steady-state flow conditions
Migration of decay chain of adsorbing contaminants during precipitation/evapotranspiration
Illustration of ‘coupled’ effects TNT degradation under steady state flow
Cd leaching in an acid podzol
Long term transient flow and transport of major cations and heavy metals in a soil profile
U-transport in agricultural field soils
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Motivation: assessment of post-closure safety for surface repository Inherent uncertainties, especially for the long-
term Use of multiple lines of reasoning Complementary safety indicators for evaluating
and confirming safety: e.g., RN fluxes, U-concentration
Objective: estimate long-term U-leaching from agricultural soils, compare with U-fluxes from planned surface repository
Introduction / objectives (1)
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Introduction / objectives (2) Multiple lines of reasoning
[U]radwaste
[U]concrete, mine waste
U-flux from NF
U-flux from soil, host formation
Individual dose
Dose limit, dose constraint
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• Introduction
• A new biogeochemical transport code:HP1
• Problem statement: soil, geochemical reactions, BC/IC
• Simulation results
• U-fluxes from soil vs. surface repository
• Conclusions
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Problem statement (1)Multilayered soil profile
Dry Podzol,7 horizons All horizons characterized
Thickness Unsaturated hydraulic properties pH Organic matter content Fe2O3 content
A
E
Bh1Bh2
Bh/C
C 1
C 2
0
7
19
24
28
50
75
depth(cm )
Sim
ula
tion d
epth
: 1 m
0 0 . 4 0 . 8 1 . 2 1 . 6 2I r o n c o n t e n t ( % )
0 1 2 3 4 5Organic matter (%)Source: Seuntjens et al., 2001. J. Contam. Hydrol.
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Aqueous speciation reactions Chemical components: C, Ca, Cl, F, H, K, Mg,
N(5), Na, O(0), O(-2), P, S(6), U(6)
Multi-site cation exchange reactions Related to amount of organic matter Increases with increasing pH
Surface complexation reactions Specific binding to charged surfaces (FeOH) Related to amount of Fe-oxides
Problem statement (2)Geochemical equilibrium reactions
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Problem statement (3)Multi-site cation exchange reactions
Because more groups of humic and fulvic acids dissociate as pH ↑proton selectivity decreases when pH ↑
negative charge of organic matter ↑
Site 1
Site 2
Site 6
...
O rganic M atter
C ation E xchange
A queous S pecia tion
W ater Phase A ir P hase
HKHM g
C a
C d
HN aHH
C a
Zn
H
HHHHHHHHH
H +
H +
ZnC l2
H +
H +
H +
N a +
C d 2+
H +
B r -
O H -
H +
C l-
C dC l+
H +
N aO H
H +
H +
H +
H +
K +
H +
H +
Zn 2+
Log_K1 (HY)
Log_K2 (HY)
Log_K6 (HY)
...
UO22+
UO22+
UO2Cl+
UO2OH+
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Problem statement (4)pH-dependent negative charge
2 3 4 5 6p H
0
0.01
0.02
0.03
0.04
0.05
Ne
ga
tive
ch
arg
eo
rga
nic
ma
tte
r(m
eq
/ g
so
il) A -horizon
E-horizon
U-species accounted for:
• UO22+, UO2OH+, UO2Cl+, UO2F+, UO2H3PO4
2+, ...
Based on Appelo et al., 1998. Appl. Geoch.
adsorbs
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Problem statement (5)Surface complexation
• Surface complexation model 0.875 reactive sites/mol Fe (Waite et al., 1994. G.C. Acta) Surface complex: FeOUO2
+ (Dzombak & Morel, 1990) • Changing processes in U adsorption with
increasing pH
2 3 4 5 6pH
0
20
40
60
80
100
% U
(VI)
ads
orbe
d
Tota l
C EC
SC
Increased deprotonation
Increased U-sorption
U-species replaced
by other cations
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Initial condition No U initially present in soil profile (<> few 10 Bq/kg)
Boundary condition 200-year time series of synthetic meteorological data
to calculate preciptiation and potential evaporation Composition rain water from measurements P-fertilizer (Ca(H2PO4)2): ~3000 Bq 238U/kg
Applied each year on May 1 (1 g P/m2) 1.610-1 mol Ca(H2PO4)2 /m² in 1 cm of rain =>3.810-6 mol U /m2 in 1 cm of rain (~105 Bq/ha)
Problem statement (6)Initial and Boundary conditions
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• Introduction
• A new biogeochemical transport code:HP1
• Problem statement: soil, geochemical reactions, BC/IC
• Simulation results
• U-fluxes from soil vs. surface repository
• Conclusions
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0.0x10 0 8.0x10 - 4 1.6x10 - 3
C a (m o l / 1 0 0 0 cm ³ so il)
5 0
4 0
3 0
2 0
1 0
0
De
pth
(cm
)
0.0x10 0 1.0x10 - 3 2.0x10 - 3 3.0x10 - 3
P (m o l / 10 0 0 cm ³ so il)
5 0
4 0
3 0
2 0
1 0
0
De
pth
(cm
)
0.0x10 0 2.0x10 - 9 4.0x10 - 9
U (m o l / 1 0 0 0 cm ³ so il)
100
75
50
25
0
De
pth
(cm
)
100 year
150 year
200 year
(b) (d) (f)
Simulation results (1)Total Ca, P, and U depth profiles
Steady-state
Transient
• Ca, P, U accumulation in Bh-horizon (rich in o.m. & Fe-ox.)
• U-breakthrough after 100 y
• U moved faster under transient than under steady-state
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Simulation results (2)Transient flow conditions =>
transient geochemical conditions
150 151 152 153 154 155 156 157 158 159 160Tim e (ye a r)
3.4
3.6
3.8
4
4.2p
HS teady-state
A tm ospheric
5 cm depth
• Water content variations induce pH variations (dry soil => low pH)
• pH variations => variations in sorption potential (low pH => low sorption)
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Simulation results (3)∆pH results in time variations of
U-mobility
3.4 3.6 3.8 4 4.2p H
1x10 1
1x10 2
1x10 3
1x10 4
K =
ad
sorb
ed
U (
mo
l/l)
/ aq
ue
ou
s U
(m
ol /
l)
A tm osphericS teady-state 25 cm depth
5 cm depth
•At least one order of magnitude variation in K
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Simulation results (4)U-fluxes: steady-state vs. transient
0 50 100 150 200
1x10 - 6
1x10 - 3
1x10 0
1x10 3
1x10 6
U f
lux
(Bq
year
-1 h
a-1
)
0 50 100 150 200
1x10 - 6
1x10 - 3
1x10 0
1x10 3
1x10 6
U f
lux
(Bq
year
-1 h
a-1
)
0 50 100 150 200Tim e (ye a r)
1x10 - 6
1x10 - 3
1x10 0
1x10 3
1x10 6
U fl
ux
(Bq
ye
ar-
1 h
a-1
)
0 50 100 150 200
1x10 - 6
1x10 - 3
1x10 0
1x10 3
1x10 6
0 50 100 150 200T im e (year)
1x10 - 6
1x10 - 3
1x10 0
1x10 3
1x10 6
7 cm
19 cm
29 cm
50 cm
100 cm
▲ : steady-state
▬ : transient
Long-term U flux = U application rate:~105 Bq/ha/y
E-horizon
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• Introduction
• A new biogeochemical transport code:HP1
• Problem statement: soil, geochemical reactions, BC/IC
• Simulation results
• U-fluxes from soil vs. surface repository
• Conclusions
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Comparison of U-fluxes
Planned Belgian surface repository :
70 000 m3 LILW; ~71012 Bq long-lived alphas Flux from NF, optimistic scenario: ~3 Bq/ha/y 238U Flux from NF, realistic scenario: ~103 Bq/ha/y 238U
Fertilizer application: ~103 -104 Bq/ha/y 238U
(1) Drums & monolith
(2) Module
(3) Soil cover
(4) Drainage gallery
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• Introduction
• A new biogeochemical transport code:HP1
• Problem statement: soil, geochemical reactions, BC/IC
• Simulation results
• U-fluxes from soil vs. surface repository
• Conclusions
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Conclusions (1)
New biogeochemical transport code HP1 provides useful insight into complex U-migration processes
U migration under atmospheric boundary conditions faster than under steady-state flow conditions Due to changing flow and geochemical
conditions (∆ pH =>∆ sorption) Atmospheric boundary conditions
important when assessing U-flux to groundwater
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Conclusions (2)
Calculated U-fluxes from soil same order of magnitude as U-flux from surface repository
Limitations of the study No interactions U-nitrate CO2 transport not accounted for More typical agricultural soils Include plant uptake Need verification experiments ...
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Use of Geochemical Transport Models
Process Coupling and InteractionsTools for investigating the impacts of multiple coupled biogeochemical reactions in the presence of complex flow fields and spatial heterogeneity. Enable extrapolation to environmentally relevant temporal and spatial scales.
Interpretation of Laboratory and Field DataProvide a useful framework for interpreting experimental results. Serve as a tool for understanding qualitative and quantitative trends and relationships present in the data.
Sensitivity AnalysisPermit the systematic evaluation of the impact of model parameters (both reactive and hydrogeological), initial conditions, and boundary conditions upon the model output.
Integration and SynthesisTool for integrating all of the knowledge obtained from simulation, sensitivity analyses, and laboratory and field experimentation.
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Find out more about HP1!
www.sckcen.be/hp1