David S. Kosson 1 and Hans A. van der Sloot 2 1 Vanderbilt University 2 Hans van der Sloot Consultancy Laboratory-to-Field Relationships and Recommendations for Leaching Assessment Using the Leaching Environmental Assessment Framework (LEAF) May 29, 2014
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David S. Kosson1 and Hans A. van der Sloot2 1Vanderbilt University
2Hans van der Sloot Consultancy
Laboratory-to-Field Relationships and Recommendations for Leaching Assessment Using the Leaching Environmental Assessment Framework (LEAF)
May 29, 2014
A Decision Support System for Beneficial Use and Disposal Decisions in the United States and Internationally…
• Four leaching test methods
• Data management tools
• Geochemical speciation and mass transfer modeling
• Quality assurance/quality control for materials production
• Integrated leaching assessment approaches
… designed to identify characteristic leaching behaviors
for a wide range of materials and scenarios &
… provide a material & scenario-specific “source-term”. More information at http://www.vanderbilt.edu/leaching
Pilot Experiment Preparation A&G, Maasvlakte, The Netherlands
18
Pilot Experiment (front view)
Geotextile – provides
vertical drainage pathway
Soil Layer - provides
buffering against high pH
and metal binding
19 19
Weathered Stabilized Waste
pH Profile measured after 4-yrs of atmospheric exposure
Weathered layer • Carbonation effects
Neutralization to pH 8-9
CaOH2 converted to CaCO3
• Plant growth
-30
-25
-20
-15
-10
-5
0
8 9 10 11 12
pH
De
pth
(c
m)
20
pH Development in Solidified Waste
21
-60
-50
-40
-30
-20
-10
0
8 9 10 11 12
-60
-50
-40
-30
-20
-10
0
8 9 10 11 12 13pH
Dep
th (
cm
)
Covered Cell (4 yrs)
Exposed (1 week)
Exposed (4 months)
Exposed (1.3 yrs)
Exposed (4 yrs)
Integration of test results from lab, lysimeter, core sample leaching, field percolate and modelling
22
[Ba+2]
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1 2 3 4 5 6 7 8 9 10 11 12 13 14
[Ca+2]
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Co
nc
en
tra
tio
n (
mo
l/l)
[Mg+2]
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1 2 3 4 5 6 7 8 9 10 11 12 13 14
[Zn+2] 1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1 2 3 4 5 6 7 8 9 10 11 12 13 14
pH
Co
nc
en
tra
tio
n (
mo
l/l)
[MoO4-2]
1.0E-10
1.0E-09
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1 2 3 4 5 6 7 8 9 10 11 12 13 14
pH
[K+]
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
1 2 3 4 5 6 7 8 9 10 11 12 13 14
pH
Red dots: pH dependence test TS14429 fresh Blue square: percolation test TS14405 fresh Purple triangle: Aged core material exposed TS14429 Green diamond: Aged core material sealed TS 14429 Open triangle: Core samples EN 12457-2 Open diamond: Core samples EN 12457-2
Red line: model prediction fresh
Purple broken line: model exposed cell
Green dotted line: modeling sealed cell
22
January 27, 2014 LEAF Short Course 23
0.00001
0.0001
0.001
0.01
0.1
1
10
100
1000
1 3 5 7 9 11 13
Co
nce
ntr
ati
on
(m
g/L)
pH
pH dependent concentration of Pb
0.0001
0.001
0.01
0.1
1
10
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Co
nce
ntr
ati
on
(m
g/L)
14
Cu as function of pH
Cu(OH)2
Tenorite
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Co
nce
ntr
ati
on
(m
ol/
l)
pH
Partitioning liquid-solid, Cu
Free DOC-bound POM-bound
FeOxide Cu[OH]2[s]
0.00001
0.0001
0.001
0.01
0.1
1
10
100
1000
10000
1 2 3 4 5 6 7 8 9 10 11 12 13
Co
nce
ntr
ati
on
(m
g/L)
pH
Pb as function of pH
Pb(OH)21.0E-10
1.0E-09
1.0E-08
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Co
nce
ntr
ati
on
(m
ol/
l)
pH
Partitioning liquid-solid, Pb
Free DOC-bound POM-bound
FeOxide Corkite Pb[OH]2[C]
Pb2V2O7 Pb3[VO4]2 PbMoO4[c]
0.0001
0.001
0.01
0.1
1
10
100
1 3 5 7 9 11 13
Co
nce
ntr
ati
on
(m
g/L)
pH
pH dependent concentration of Cu
0.0001
1000
2 4 6 8 10 12 14
Co
nce
ntr
ati
on
(m
g/L)
pH
pH dependent concentration of ZnCore sample composite Cell B (4 yrs) Individual core sample Cell B (L/S=10; 4 yrs)
Core sample composite Cell C (covered; 4 yrs) Individual core sample Cell C (L/S=10; 4 yrs)
Leachate Cell B Leachate Cell C
Leachate Cell D Individual core sample Cell D (L/S=10; 4 yrs)
EPA-SX-BAG Porewater EPA Lab - All CFAs - 5th, 95th % EPA Lab - All CFAs - Median
Case 2 – Coal Fly Ash - Field Lysimeters
Compared large-scale lysimeters (7 years) to percolation column tests.
Results
Applicable field pH domain: 11 – 12.8
Percolation column testing can provide a good estimate of initial
leachate concentrations under field conditions.
Percolation column testing provides a good approximation of the
evolution of leaching profiles as a function of L/S that would be
expected under field conditions in the absence of preferential flow
and establishment of strong reducing conditions.
January 27, 2014 LEAF Short Course 26
Case 2 – Coal Fly Ash - Field Lysimeters
and Laboratory Column Testing
LEAF Short Course 27
0,001
0,01
0,1
1
0,001 0,01 0,1 1 10
Elu
ate
co
ncen
trati
on
(m
g/L
)
L/S (L/kg)
As
0,01
0,1
1
10
100
0,001 0,01 0,1 1 10
Elu
ate
co
ncen
trati
on
(m
g/L
)
L/S (L/kg)
Cr
0,01
0,1
1
10
100
0,001 0,01 0,1 1 10
Elu
ate
co
ncen
trati
on
(m
g/L
)
L/S (L/kg)
Mo
10
11
12
13
0,001 0,01 0,1 1 10
pH
L/S (L/kg)
pH
Lysimeter-4
Lysimeter-9
Lysimeter-14
Column-4
1
10
100
1000
10000
0,001 0,01 0,1 1 10
Elu
ate
co
ncen
trati
on
(m
g/L
)
L/S (L/kg)
Na
Lysimeter-4
Lysimeter-9
Lysimeter-14
Column-4
Case 3 – Fixated Scrubber Sludge Landfill
Compared field leaching, field pore water samples, and laboratory
leaching test results on landfill core samples, and on fresh “as
disposed” material
Results
Applicable field pH domain: 6 – 9.5
Carbonation during field aging can have a significant impact on the pH
dependent leaching behavior of periodic table Group II elements
(i.e., Ca, Sr) and some trace elements (i.e., arsenic).
Water samples (i.e., landfill porewater) are more susceptible to
carbonation because of air contact and low buffering capacity.
Higher concentrations of highly soluble species (i.e., K, Na, Cl) can be
anticipated in porewater compared to laboratory testing. Elevated
concentrations can be readily estimated based (L/S effect).
28
Case 3 – FSSL – Effect of L/S
LEAF Short Course 29
1
10
100
1000
0 2 4 6 8 10 12 14
Po
tassiu
m (
mg
/L)
pH
1
10
100
1000
10000
0 2 4 6 8 10 12 14
So
diu
m (
mg
/L)
pH
10
100
1000
10000
0.1 1 10
Po
tassiu
m (
mg
/L)
L/S (L/kg)
L/S=10 L/kg; Conc=40 mg/L
L/S=0.5 L/kg;Conc=20*40 mg/L=800 mg/L
10
100
1000
10000
0.1 1 10
So
diu
m (
mg
/L)
L/S (L/kg)
L/S=0.5 L/kg;Conc=20*30 mg/L=600 mg/L
L/S=10 L/kg; Conc=30 mg/L
Case 4 – Coal Fly Ash Road base and Embankment
Compared the results of field leaching over 2 years from a road base
and embankment to percolation column results.
Results
Combined use of pH dependent leaching and percolation column
leaching in combination with chemical speciation simulations to
understand field performance.
Reducing conditions and carbonation impact leaching of major species
(e.g., Ca, Sr) and oxyanions (e.g., Cr).
Percolation column testing provided a realistic estimate of the upper
bound concentration for leaching of COPCs.
An initial delay in the field before peak leaching concentrations were
observed was attributed to the mass transport delay and attenuation
associated with drainage materials
30
Case 4 – Coal Fly Ash Road base and Embankment
LEAF Short Course 31
Road Base
Embankment
Case 4 – CFA Road Base and Embankment
Effect of Redox Conditions
LEAF Short Course 32
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0.01 0.1 1 10 100
Ch
rom
ium
(m
ol/
L)
L/S (L/kg)
Coal Fly Ash; pH+pE=15
Percolation Column
[CrO4-2] (continuous)
[CrO4-2] (fraction average)
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0.01 0.1 1 10 100
Ch
rom
ium
(m
ol/
L)
L/S (L/kg)
Coal Fly Ash; pH+pE = 12.8
Percolation Column
[CrO4-2] (continuous)
[CrO4-2] (fraction average)
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0.01 0.1 1 10 100
Ch
rom
ium
(m
ol/
L)
L/S (L/kg)
Coal Fly Ash; pH+pE = 12
Coal fly ash NL (column)
[CrO4-2] (continuous)
[CrO4-2] (fraction average)
Embankment
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0.00 3.33 6.67 10.00 13.33
Ch
rom
ium
(m
ol/
L)
Depth (m)
Partitioning Profile; L/S=1.3, pH+pE=15
Free
POM-bound
FeOxide
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0.00 3.33 6.67 10.00 13.33
Ch
rom
ium
(m
ol/
L)
Depth (m)
Partitioning Profile; L/S=1.3, pH+pE=12.8
Free
POM-bound
FeOxide
Cr(OH)3 [A]
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
0.00 3.33 6.67 10.00 13.33
Ch
rom
ium
(m
ol/
L)
Depth (m)
Partioning Profile; L/S=1.3, pH+pE = 12
Free
POM-bound
FeOxide
Cr(OH)3 [A]
Conclusions
LEAF can be used to provide a reasonably conservative (upper-
bound) source-term for a wide range of materials in use and disposal
scenarios.
Interpretation of the leaching test results should be in the context of
the controlling physical and chemical mechanisms of the field
scenario.
Leaching test results should be evaluated with consideration of the
potential for changes in leaching conditions
• pE changes (oxidation of reduced materials, reduction of oxidized material)
• Carbonation
• DOC from external sources
Chemical speciation modeling can be used to consider field
conditions beyond the domain of laboratory test conditions.
33
Selecting Methods and Data Use
Acceptable
Impact?
Treatment
Option
Mgmt
Scenario
Fundamental leaching properties
Equilibrium data
Site information*
Assessment model
Fundamental leaching properties
Availability data, Equilibrium
data, Mass Transfer data
Site information*
Assessment model
Material
Yes
Release Estimate
Exit Yes No
Flow - around Percolation
* Site - specific information or Default scenarios
Acceptable
Impact?
Treatment
Option
Mgmt
Scenario
Fundamental leaching properties
Equilibrium data
Site information*
Assessment model
Fundamental leaching properties
Availability data, Equilibrium
data, Mass Transfer data
Site information*
Assessment model
Material
Yes
Release Estimate
Exit Yes No
Flow - around Percolation
Acceptable
Impact?
Treatment
Option
Mgmt
Scenario
Fundamental leaching properties
Availability, Equilibrium data,
Site information*
Assessment model
Fundamental leaching properties
Availability data, Equilibrium
data, Mass Transfer data
Site information*
Assessment model
Material Material
Yes
Release Estimate
Exit Yes No
Flow - around Percolation
* Site - specific information or Default scenarios
34
Conclusions
The leaching source term should be used in conjunction with
additional assessment steps that include consideration of
• the location that serves as the basis for exposure assessment
(e.g., point of compliance),
• dilution and attenuation from the point of release to the point of
compliance, and
• appropriate exposure scenarios or reference thresholds
(e.g., human health or ecological thresholds).
Field testing of new use or disposal scenarios or new classes of
materials to be used or disposed in new ways is very beneficial to
understanding the factors that control leaching for the specific
scenario.
LEAF Short Course 35
Conclusions
Individual sources of similar materials based on process origin and
leaching behavior can be grouped into material classes for
assessment purposes
Accumulation of LEAF testing data for a range of materials and over
time can provide useful estimates of uncertainty and variability
associated with material classes.
Creation of one or more databases containing leaching data used in
regulatory decision making and monitoring can facilitate efficient use
of leaching data in future assessments
• More robust assessments
• Reduced testing and evaluation costs
LEAF Short Course 36
Conclusions
Single point leaching tests and other common leaching assessment
approaches cannot provided needed insights into the expected
leaching performance of materials under the range of expected field
conditions.
The combination of results from pH-dependent leaching tests and
percolation column tests (or monolith leach tests) can be used to
provide reliably conservative estimates of field leachate
concentrations under both disposal and use scenarios.
LEAF Short Course 37
Vanderbilt University research team and collaborators:
D.S. Kosson (USA lead)1, A.C. Garrabrants1*, H.A. van der Sloot2 (EU Lead),
R. DeLapp1, D. DeLapp1, S. Sarkar1, K. Brown1, P. Seignette3,
O. Hjelmar4, J.C.L. Meeussen3
EPA development team and collaborators:
Susan Thorneloe5 (Lead), Mark Baldwin6, Richard Benware6,
Greg Helms6, Jason Mills6, Tim Taylor6, Peter Kariher7
1 Vanderbilt University, Nashville, TN *CH2M-Hill as of Jan. 2014 2 Hans van der Sloot Consultancy, Langedijk, The Netherlands 3 Energy Research Centre of The Netherlands, Petten, The Netherlands 4 DHI, Hørsolm, Denmark 5 U.S. EPA Office of Research and Development, RTP, NC 6 U.S. EPA Office of Resource Conservation & Recovery, Washington DC 7 ARCADIS-US, Inc., RTP, NC
Acknowledgements
38
Thank you
for your attention and invitation to
participate in this workshop!
Questions?
39
40
Additional Supporting Information
Method 1313 Overview
n chemical analyses
Ln LB LA
n samples
S2 Sn n B A
S1
0.01
0.1
1
10
100
1000
2 4 6 8 10 12 14 Leachate pH
Co
pp
er
[mg/
L]
Titration Curve and Liquid-solid Partitioning (LSP) Curve as Function of Eluate pH
41
Equilibrium Leaching Test
• Parallel batch as function of pH
Test Specifications
• 9 specified target pH values plus natural conditions
• Size-reduced material
• L/S = 10 mL/g-dry
• Dilute HNO3 or KOH
• Contact time based on particle size 18-72 hours
• Reported Data Equivalents of acid/base added
Eluate pH and conductivity
Eluate constituent concentrations
Equilibrium Leaching Test
• Percolation through loosely-packed material
Test Specifications
• 5-cm diameter x 30-cm high glass column
• Size-reduced material
• DI water or 1 mM CaCl2 (clays, organic materials)