D.S. Kosson1, A.C. Garrabrants1, Hans van der Sloot2, Susan Thorneloe3, Richard Benware4, Greg Helms4, and Mark Baldwin4

1 Vanderbilt University, Nashville, TN2 van der Sloot Consultancy, Langedijk, the Netherlands3 U.S. EPA Office of Research and Development, RTP, NC

4 U.S. EPA Office of Resource Conservation & Recovery, Washington DC

19 June 2012

The Leaching Environmental Assessment Framework as a Tool for Risk‐informed, Science‐based Regulation

Introduction to Leaching Assessment

Overview of LEAF• Leaching Tests• Data Management

Overview of Interlaboratory Validation

Applicability to DOE Challenges

Conclusions

Presentation Outline

2

1960s-1990sProtection from hazardous wastes; waste minimization/conservation.

• Classification of “hazardous” waste (RCRA Subtitle C/D landfills)• Acceptance criteria for disposal of treated wastes (Universal Treatment Standards)• Best demonstrated available treatment (BDAT)

1990s – presentMove toward integrated materials management; balancing overall environmental performance with materials costs and long-term liability

• Global economic policy (resource costs, international trade)• Risk-informed waste management practices• Changing definition of waste materials (e.g., Dutch Building Materials Decree; U.S.

definition of solid waste)• Applications for waste delisting and alternative measures of treatment effectiveness • Re-use of waste materials (mine reclamation, alternative construction materials)

Materials Testing – Historically

3

Process by which constituents of a solid material are released into a contacting water phase

What is Leaching?

Percolation Release Water passes thru material Equilibrium High concentration

Mass Transfer Release Water flows around material Diffusion to material surface Lower concentration

4

Leaching - Controlling Factors

Physical Factors Particle size Rate of mass

transport

Site Conditions Flow rate of leachant Temperature Bed porosity Fill geometry Permeability Hydrological conditions

Chemical Factors Equilibrium/kinetic control pH Liquid-solid ratio Complexation Redox Sorption Biological activity

Trace elements

Soluble salts

TOC (at high pH) DOC

H+

CO2

O2

Erosion

ReleaseMechanisms

Wash OffDissolutionDiffusion

5

Total ContentTotal Content Does Not Correlate to Leaching

10-1

100

101

102

103

104

105

As

[µg/

L] -

Max

. Elu

ate

Con

cent

ratio

n

10-1 100 101 102 103

As - Total By Digestion [µg/g]

As

Fly Ash SDA Gypsum Scrubber Sludge Blended CCRs

Same total content with different eluateconcentrations

Same eluateconcentration with different total contents

6

Many Leaching Scenarios …

coastal protection

construction debris and run-off

roof runoff

municipal sewer system

drinking water welllandfill contaminated soil

road base

industrially contaminated soil

factory seepage basin

agriculture

mining

7

Common Assessment Approach

road base

C

B

A* A*

B

C

A CCR Leaching

Constituent Release from Use

Constituent Pt. of Compliance

Location DAF

Use Source TermCCR Leaching in Use Context

ThresholdDefinition

Total Content• Correlation to leaching?

Regulatory Tests• Comparison to limits• Does not consider

Release Scenario Time (kinetics) Mass Transport

Characterization Tests• Range of conditions• Comparisons between

Materials Treatments Scenarios

Leaching Tests

0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

enic

(m

g/L)

pH

Total Content

0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

enic

(m

g/L)

pH

Total Content

Single Point Test

0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

enic

(m

g/L)

pH

Total Content

Single Point Test

Regulatory Limit

0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

enic

(m

g/L)

pH

Total Content

Single Point Test

Regulatory Limit

0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

enic

(m

g/L)

pH

Total Content

Single Point Test

Characterization Test

0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

enic

(m

g/L)

pH

Total Content

Regulatory Limit

Portland

Cemen

t

Characterization Test

0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

enic

(m

g/L)

pH

Total Content

Regulatory Limit

Blen

ded Ce

men

tCharacterization Test

9

Leaching Method DevelopmentLeaching characterization applied to anticipated release conditions resulting in improved accuracy and more reliable environmental decision making

“An Integrated Framework for Evaluating Leaching in Waste Management and Utilization of Secondary Materials,” D.S. Kosson, H.A. van der Sloot, F. Sanchez, and A.C. Garrabrants, Environmental Engineering Science, 19(3): 159-204, 2002.

Parallel and coordinated methods development in the EU and US

Designed to address concerns of EPA Science Advisory Board• Form of the material (e.g., monolithic)• Leaching parameters (e.g., pH, liquid-solid ratio (L/S), release rate)

Intended for situations where TCLP is not required or best suited• Assessment of materials for beneficial reuse• Evaluating treatment effectiveness (determination of equivalent treatment)• Characterizing potential release from high-volume materials • Corrective action (remediation decisions)

10

Leaching Environmental Assessment FrameworkLEAF is a collection of …

• Four leaching 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 associated use and disposal scenarios.

LEAF facilitates integration of leaching methods which provides a material-specific “source term” release for support of material management decisions.

More information at http://www.vanderbilt.edu/leaching

11

LEAF Leaching MethodsMethod 1313 – Liquid-Solid Partitioning as a Function of Eluate pH using a

Parallel Batch Procedure

Method 1314 – Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio (L/S) using an Up-flow Percolation Column Procedure

Method 1315 – Mass Transfer Rates in Monolithic and Compacted Granular Materials using a Semi-dynamic Tank Leaching Procedure

Method 1316 – Liquid-Solid Partitioning as a Function of Liquid-Solid Ratio using a Parallel Batch Procedure

Note: Incorporation into SW-846 is ongoing; method identification numbers are subject to change

12 12

Method 1313 Overview

nchemicalanalyses LnLBLA

n samples

S2 SnnBA

S1

0.01

0.1

1

10

100

1000

2 4 6 8 10 12 14Leachate pH

Cop

per [

mg/

L]

Titration Curve and Liquid-solid Partitioning (LSP) Curve as Function of Eluate pH

13

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 NaOH• 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)• Upward flow to minimize channeling• Collect leachate at cumulative L/S

0.2, 0.5, 1, 1.5, 2, 4.5, 5, 9.5, 10 mL/g-dry

• Reported Data Eluate volume collected Eluate pH and conductivity Eluate constituent concentrations

Method 1314 Overviewair lock

eluant collection bottle(s)(sized for fraction volume)

Luer shut‐offvalve

eluant reservoir

end cap

end cap

1‐cm sandlayers

pump

subjectmaterial

Luer shut‐offvalve

Luer fitting

Luer fitting

N2 or Ar (optional)

Liquid-solid Partitioning (LSP) Curve as Function of L/S; Estimate of Pore Water Concentration

14

Method 1315 OverviewMass-Transfer Test• Semi-dynamic tank leach test

Test Specifications• Material forms

monolithic (all faces exposed) compacted granular (1 circular face exposed)

• DI water so that waste dictates pH• Liquid-surface area ratio (L/A) of 9±1 mL/cm2

• Refresh leaching solution at cumulative times 2, 25, 48 hrs, 7, 14, 28, 42, 49, 63 days

• Reported Data Refresh time Eluate pH and conductivity Eluate constituent concentrations

1 Sample

nanalyticalsamples

A1

L1

A2 An

L2 Ln

∆t1 ∆tn

orMonolith

CompactedGranular

n Leaching Intervals

∆t2

Flux and Cumulative Release as a Function of Leaching Time

Granular

Monolithic

0.001

0.01

0.1

1

10

100

1000

0.01 0.1 1 10 100

Cr R

elea

se [

mg/

m2 ]

Leaching Time [days]

Availability

MDL

ML

15

Method 1316 OverviewEquilibrium Leaching Test• Parallel batch as function of L/S

Test Specifications• Five specified L/S values (±0.2 mL/g-dry)

10.0, 5.0, 2.0, 1.0, 0.5 mL/g-dry• Size-reduced material• DI water (material dictates pH)• Contact time based on particle size

18-72 hours• Reported Data

Eluate L/S Eluate pH and conductivity Eluate constituent concentrations

nchemicalanalyses LnLBLA

n samples

S2 SnnBA

S1

Liquid-solid Partitioning (LSP) Curve as a Function of L/S; Estimate of Pore Water Concentration

16

0

20

40

60

80

100

120

0 2 4 6 8 10

Mol

ybde

num

[µg/

L]LS Ratio [mL/g-dry]

Data Management ToolsData Templates

• Excel Spreadsheets for Each Method Perform basic, required calculations (e.g, moisture content) Record laboratory data Archive analytical data with laboratory information

• Form the upload file to materials database

LeachXS (Leaching eXpert System) Lite• Data management, visualization and processing program• Compare Leaching Test Data

Between materials for a single constituent (e.g., As in two different CCRs) Between constituents in a single material (e.g., Ba and SO4 in cement) To default or user-defined “indicator lines” (e.g., QA limits, threshold values)

• Export leaching data to Excel spreadsheets• Freely available at http://www.vanderbilt.edu/leaching

17 17

Data Templates

18

DRAFT METHOD 1313  (Liquid‐Solid Partitioning as a Function of pH) LAB DATA

Code  Description (optional) Test conducted by: Extraction InformationProject  ABC   Example project LS Ratio  10 [mL/g‐dry

Material  XYZ   Exaple material Solids Information Liquid Volume / Extraction  200  [mL]Replicate  A Maximum Particle Size  0.3  [mm] Recommended Bottle Size *  250  [mL]

Minimum Dry Equivalent Mass *  20.00  [g‐dry]Date Time Solids Content (default = 1)  0.901  [g‐dry/g] Nominal Reagent Information

Test Start 1/2/xx 2:00 PM Mass of "As Tested" Material / Extraction 22.20  [g] Acid Type  HNO3Test End 1/3/xx 1:45 PM Acid Normality  2.0 [meq/mL]

Required Contact Time *  23‐25  [hr] * Data based on Draft Method 1313 Table 1. Base Type  NaOHBase Normality  1.0 [meq/mL]

Schedule of Acid and Base AdditionTest Position  T01 T02 T03 T04 T05 T06 T07 T08 T09 B01 B02 B03 totals

"As Tested" Solid [g]  (±0.05g) 22.20 22.20 22.20 22.20 22.20 22.20 22.20 22.20 22.20 no solid no solid no solid 199.8Reagent Water [mL] (±5%) 147.80 167.80 185.80 197.80 195.80 193.80 189.80 185.80 178.80 200.00 181.00 150.00 2174.2Acid Volume [mL]  (±1%) ‐ ‐ ‐ ‐ 2.00 4.00 8.00 12.00 19.00 ‐ 19.00 ‐ 64.0Base Volume [mL]  (±1%)  50.00 30.00 12.00 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 50.00 142.0Acid Normality [meq/mL] ‐ ‐ ‐ ‐ 2.0 2.0 2.0 2.0 2.0 ‐ 2.0 ‐Base Normality [meq/mL] 1.0 1.0 1.0 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 1.0

Target pH 13.0±0.5 12.0±0.5 10.5±0.5 natural 8.0±0.5 7.0±0.5 5.5±0.5 4.0±0.5 2.0±0.5Acid Addition [meq/g]  ‐2.5 ‐1.5 ‐0.6 0 0.2 0.4 0.8 1.2 1.9 Water Acid Base

Eluate pH  12.80 12.20 10.80 9.20 7.80 5.98 4.79 3.60 2.30Eluate EC [mS/cm] 

Eluate Eh [mV] Save? (enter "a" or "r" ) 

Notes   pH out of range

pH out of range

1) Enter particle sizeand solids content

2) Enter acid/base

type & normality

3) Enter target equivalents from titration curve

4) Follow “set-up” recipe

5) Record pH, conductivity, Eh (optional)

6) Verify that final pH is in acceptable range

LeachXS Lite

19

1) Set working materials database

2) Select material tests from database

3) Choose display options

4) Check comparison of materials for a single constituent

5) Bulk export one or more constituents to an

Excel spreadsheet

LEAF Methods Validation

20

Study MaterialsCoal Combustion Fly Ash

• Collected for EPA study• Selected for validation of … Method 1313 Method 1316

Solidified Waste Analog• Created at Vanderbilt University• Blast Furnace Slag, Class C Fly

Ash, Type I/II Cement, Metal Salts• Selected for validation of … Method 1313 Method 1316 Method 1315

Contaminated Field Soil• Copper smelter site• Selected for validation of… Method 1313 Method 1316 Method 1315 Method 1314

Brass Foundry Sand• Selected for validation of … Method 1315 Method 1314

21

Method 1313 Validation

22

1

10

100

1000

0 2 4 6 8 10 12 14S

e R

ep

rod

uci

bil

ity

(%)

Target pH

CFS RSD‐REaFA RSD‐RSWA RSD‐R

ICP‐OES RSD

1

10

100

1000

0 2 4 6 8 10 12 14

As

Re

pro

du

cib

ilit

y (%

)

Target pH

CFS RSD‐REaFA RSD‐RSWA RSD‐R

ICP‐OES RSD

ML

MDL

0.01

0.1

1

10

0 2 4 6 8 10 12 14

Se

len

ium

(m

g/L

)

Target pH

M1313 EaFA MeanOverall SDBetween Lab SDWithin Lab SD

ML

MDL0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

en

ic (

mg

/L)

Target pH

MeanOverall SDBetween Lab SDWithin Lab SD

ML

MDL0.01

0.1

1

10

100

0 2 4 6 8 10 12 14

Ars

en

ic (

mg

/L)

Target pH

M1313 EaFA MeanOverall SDBetween Lab SDWithin Lab SD

ML

MDL

0.01

0.1

1

10

0 2 4 6 8 10 12 14

Se

len

ium

(m

g/L

)

Target pH

M1313 CFS MeanOverall SDBetween Lab SDWithin Lab SD

Coal Combustion Fly Ash Contaminated Field Soil Reproducibility

Data ProcessingLog10-Transform of Test Output

• Method 1313 – Eluate Concentration• Method 1314 – Eluate Concentration,

Cumulative Mass Release• Method 1315 – Interval Mass Flux,

Cumulative Mass Release• Method 1316 – Eluate Concentration

Linear Interpolation and Extrapolation• Collected Data Shows Variability• Brings Data to Specified pH, L/S or Time• Consistency in Comparisons

Implications for Compliance Standards

23

ML

MDL

0.01

0.1

1

10

0 2 4 6 8 10 12 14

Sele

niu

m (

mg/

L)

pH

ML

MDL

0.01

0.1

1

10

0 2 4 6 8 10 12 14

Sele

niu

m (

mg/

L)

target pH

LEAF Method Precision

24

Method Test Output RSDr(%)

RSDR(%)

Method 1313 Eluate Concentration (average over pH range) 10 26

Method 1314 Eluate Concentration (9th fraction at L/S=10)Mass Release (cumulative to L/S=0.5)Mass Release (cumulative to L/S=10)

1375

281814

Method 1315 Interval Flux (average excluding wash-off)Mass Release (cumulative to 7-days)Mass Release (cumulative to 63-days)

1196

281923

Method 1316 Eluate Concentration (average over L/S range) 7 17

Precision Comparison(pH-dependence Tests)

25

0

20

40

60

80

100

EaFA SWA CFS EN12457-2 TCLPR

SDR

(%)

Max CFSBa @ pH 13RSDR = 300%

Max SWASb @ pH 2

RSDR = 500%

Max RSDR = 124%

Max RSDR = 118%

0

20

40

60

80

100

EaFA SWA CFS EN12457-2

RSD

r(%

)

Max SWASb @ pH 2

RSDr = 130%

Max CFSBa @ pH 13RSDr = 114%

ReproducibilityRepeatability

Method Precision• Method 1314 Eluate Concentration (2 pH  13)• EN12457 Eluate Concentration (natural pH)• TCLP Eluate Concentration (acetic acid buffer)

Precision Comparison(Percolation Tests)

26

0

20

40

60

80

100

CFS JaFS DIN19528

RSD

r(%

)

0

20

40

60

80

100

CFS JaFS DIN19528 TCLPR

SDR

(%)

Max RSDR = 139%

Max RSDR = 118%

ReproducibilityRepeatability

Method Precision• Method 1314 Cumulative Release at L/S = 10 L/kg• DIN 19528 Cumulative Release at L/S = 4.0 L/kg• TCLP Eluate Concentration (L/S = 20 L/kg)

27

EPA Database Field leachate samples for fly ash only comparison withLEAF (EPA‐600/R‐09/151) All Fly Ash 5th, 50th, 95th percentiles and maximums

Comparison of Laboratory and Field Results

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

100

3 5 7 9 11 13pH

[Ni]

(mg/

kg)

0.000001

0.00001

0.0001

0.001

0.01

0.1

1

10

100

0.0001 0.001 0.01 0.1 1 10 100L/S (l/kg)

Cum

. rel

ease

, [N

i] (m

g/kg

)

Lab

Lysimeter

Field

Consistent behaviour in different scales of testing

28

29

Generic Vault Disposal System

ReinforcingSteel

Waste Form

Clean Grout(high strength)

Muli-layer Cap and Infiltration Control

Drainage Layeror Capillary Break

PerchedWater

Seepage

Infiltration

29

30

Conceptual Model• Micro-cracks develop,

increasing solid-liquid surface area

• Bridging of micro-cracks create macro-cracks

• Through-cracks develop over time, leading to convective flow

• Ultimate end state may be permeable matrix – release based on local equilibrium

Physical Integrity & Water Contact

Monolithic MatrixFlow-aroundLow interfacial areaDiffusive release

Stressed MatrixFlow-around/throughHigher interfacial areaDiffusion-convection

Spalled MatrixHigh permeabilityVery high interfacial areaEquilibrium-based release

ImpactNeed to account for the sequence of physical states and rate of changes Influences chemical reactions and constituent releaseBoth “intact” & “degraded” cases are simplistic and may not be realistic

Processes and Impacts

30

31

Needed Information• External stresses

External loads

Differential settlement

• Material strength (e.g., Young’s Modulus)

• Material pore structure

• Internal stresses

Shrinkage/dehydration

Expansive reactions within pores

Physical Integrity & Water Contact

Monolithic MatrixFlow-aroundLow interfacial areaDiffusive release

Stressed MatrixFlow-around/throughHigher interfacial areaDiffusion-convection

Spalled MatrixHigh permeabilityVery high interfacial areaEquilibrium-based release

Processes and Impacts

31

32

Moisture Transport Conceptual ModelWaste form consumes water via hydration reactionsMoisture exchange w/environment

Evaporation/condensationCapillary suctionIntermittent wetting (precipitation)Percolation (degraded matrix)

Water content determines Gaseous degradation processes (oxidation, carbonation)Constituent diffusion pathways

ImpactSpatial & temporal moisture gradientsDiffusivities are not constant over moisture regimeFractional saturation

Increases the importance of gas phase transport & reactionsDecreases rate of liquid phase transport

Full SaturationCapillary Saturation

(a)Continuous LiquidDiscontinuous Gas

Transition Zone (b)Continuous Liquid Continuous Gas

Insular Saturation (c)Discontinuous LiquidContinuous Gas

Completely Dry

Hamb

RH=100%

Hamb

RH=100%

Hamb

RH=100%

Hamb

RH=100%

Hamb

RH<100%

Hamb

RH<100%

Hamb

RH<100%

Hamb

RH<100%

Hamb

RH<100%

RH < 100%

Hamb

RH < 100%RH < 100%

Hamb

RH < 100%

Hamb

RH < 100%RH < 100%

Hamb

RH < 100%RH < 100%

Hamb

0 Saturation 1insular

saturationcapillary

saturation

Diffusivity

D/D

0

1

0GasLiquid

(a)

(c)

(b)

Processes and Impacts

32

33

Moisture TransportFull SaturationCapillary Saturation

Continuous LiquidDiscontinuous Gas

Transition ZoneContinuous Liquid Continuous Gas

Insular SaturationDiscontinuous LiquidContinuous Gas

Completely Dry

Hamb

RH=100%

Hamb

RH=100%

Hamb

RH=100%

Hamb

RH=100%

Hamb

RH<100%

Hamb

RH<100%

Hamb

RH<100%

Hamb

RH<100%

Hamb

RH<100%

RH < 100%

Hamb

RH < 100%RH < 100%

Hamb

RH < 100%

Hamb

RH < 100%RH < 100%

Hamb

RH < 100%RH < 100%

Hamb

Needed InformationWater producing & water consuming reactions

Water retention curves (capillarity)

Relative humidity-material saturation equilibrium

Drying rates

Permeability (water)

Boundary conditions

Episodic infiltration

Relative humidity

0 Saturation 1insular

saturationcapillary

saturation

Diffusivity

D/D

0

1

0GasLiquid

Processes and Impacts

33

34

OxidationRates and Extent

Air Water Ratio (A/W)

DO2 [cm2/s] 0.21 0.000019 1.1E+04

Conc of O2 [mole/L] 8.9E-03 2.6E-04 1.4E+01

(1) Wilke and Chang, 1955(2) www.swbic.org/education/ env-engr/gastransfer/gastransf.html

oxidation front

O2

occludedpore

Conceptual ModelWaste form pores – two phase system of gas and liquid; depends on moisture content (saturation)O2 transport via gaseous diffusion may be important depending on saturation.Oxidation may lead to change in leaching behavior

Increased Tc-99 release; other redox sensitive constituents

ImpactGas phase transport must be considered

Flux of O2 (gas) ~105 > liquid phase flux

Processes and Impacts

34

35

OxidationRates and Extent

oxidation front

O2

occludedpore

Needed InformationReducing capacity & redox titrationMoisture statusGas phase diffusivity f(saturation)Liquid phase diffusivity f(saturation)Boundary conditions

Processes and Impacts

35

36

Carbonation

CO2

carbonation front

Conceptual ModelCO3

-2 + Ca+2 → CaCO3 (s)Gas phase diffusion of CO2Liquid phase diffusion of HCO3

-

Pore water pH decreased

Alters solubility of constituents (increase or decrease depending on species).

CarbonationExpansive precipitate – internal stress (cracking)Pore blocking – increases diffusional resistance (decreases oxidation, release rates).Extent and pore effects depend on waste form alkalinity and saturation

0.0001

0.001

0.01

0.1

1

10

100

2 4 6 8 10 12 14Leachate pH

As

[mg/

L]

NoncarbonatedCarbonated

ImpactPotential for speciation changes (e.g., As)Impact on sorption sitesPore structure changesMay have either positive (e.g., pore capping) or detrimental (i.e., increased solubility) impacts

Processes and Impacts

36

37

Conceptual Model• Transport described by moving

dissolution fronts• Precipitation/reaction processes near

external boundaries may significantly impact release (+ or -)

• Dissolution/diffusion of Ca(OH)2 and CSH control pore water pH pH gradients alter trace species

release• SO4 leaching from waste into vault

attacking concrete physical structure.• Source of SO4 may be waste or

external environmentImpact• Mass transport estimates may not

reflect the dynamic chemistry and mineralogy of the waste form.

• Release rates and extents mechanistically different from simplified assumptions, effecting predictability.

Leaching of Major Constituents

VaultWall

WasteForm

(high SO4)

leac

han

t

Ca moving front

effHD

CCa=CCa,0SCa=Sp,0

SSO4=SSO4,0=0

Ca(OH)2dissolution

pH

CCa=CCaSCa=0>0

effCaD

SO4 moving front

effSO4D

SO4 moving front

effSO4D

Sulfate species precipitate in cracks and large pores in vault concrete.

Processes and Impacts

37

38

Conceptual Model• Release based on coupled

chemistry and mass transport.• Release dependent on:

Moisture conditions pH gradients Redox chemistry Boundary layer formation

Impact• Performance assessments may

over- or under-predict release

Leaching of Trace Constituents

leac

han

t

Ca moving front

effHD

CCa=CCa,0SCa=Sp,0SMe=SMe,0=0

Ca(OH)2dissolutionpH

Me moving front

effHDeffMeD

CCa=CCaSCa=0

CMe=f{pH}

effCaD

AMD - Selenium

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

0.01 0.1 1 10 100 1000Mean Interval [days]

Mea

n Fl

ux [m

g/m

2s]

AMD-AAMD-BMean

Simple Diffusion

Model predicts flux 102

greater than measured

after ~1 year

Processes and Impacts

38

39

Needed Information• pH dependent equilibrium

• Column test Pore water LS evolution

• Analysis of pH, EC, Eh Full suite of cations and

anions TOC, TIC, DOC, DIC

• Boundary Conditions!

Leaching of Major &Trace Constituents

leac

han

t

Ca moving front

effHD

CCa=CCa,0SCa=Sp,0SMe=SMe,0=0

Ca(OH)2dissolutionpH

Me moving front

effHDeffMeD

CCa=CCaSCa=0

CMe=f{pH}

effCaD

Processes and Impacts

39

A Possible Approach to Beneficial Use Screening LevelsStep 1: Select use application (includes engineering specifications) 

Step 2: Select corresponding pH domain and perform Method 1313

Step 3:  (a) Select corresponding fate and transport values(i)  CCR fraction in engineered use (fCCR);(ii)  Across‐the‐board engineered attenuation factor (EAF);(iii) Default constituent‐specific dilution attenuation factors (DAFs);(iv) Human or ecological benchmarks (federal and/or state); and

(b) Calculate screening levels

Step 4: Compare maximum LEAF result to screening levelsUse is protective of human health and the environment? (i.e., LEAF < screening level?)

Proceed with use

Conduct site‐specific IWEM modeling with 

Method 1313 data from Step 2 or Method 1315 

data (if available)

Can use application and/or engineering specifications be modified?Yes

No

Choose

Pass FailInappropriate for this use

Perform  Method(s) 1314/1316 or 1315

Yes

No

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Supporting DocumentationH.A. van der Sloot, D.S. Kosson, A.C. Garrabrants and J. Arnold The Impact of Coal Combustion Fly Ash Used as a Supplemental Cementitious Material on the Leaching of Constituents from Cements and Concretes, draft report in administrative review (submitted Nov 2011).

A.C. Garrabrants, D.S. Kosson, L. Stefanski, R. DeLapp, P.F.A.B. Seignette, H.A. van der Sloot, P. Kariher and M. Baldwin Interlaboratory Validation of the Leaching Environmental Assessment Framework (LEAF) Leaching Tests for Inclusion into SW-846: Method 1313 and Method 1316, draft report in administrative review (submitted Nov 2011)

A.C. Garrabrants, D.S. Kosson, H.A. van der Sloot, F. Sanchez, and O. Hjelmar (2010) Background Information for the Leaching Environmental Assessment Framework Test Methods, EPA/600/R-10/170, December 2010; http://www.epa.gov/nrmrl/pubs/600r10170/600r10170.pdf.S.A. Thorneloe, D.S. Kosson, F. Sanchez, A.C. Garrabrants, and G. Helms (2010) “Evaluating the Fate of Metals in Air Pollution Control Residues from Coal-Fired Power Plants,” Environmental Science & Technology, 44(19), 7351-7356, http://pubs.acs.org/doi/pdfplus/10.1021/es1016558.

D. Kosson, F. Sanchez, P. Kariher, L. Turner, D. Delapp, P. Seignette and S. Thorneloe (2009) Characterization of Coal Combustion Residues from Electric Utilities - Leaching and Characterization Data, EPA-600/R-09/151, December 2009; http://www.epa.gov/nrmrl/pubs/600r09151/600r09151.html.

F. Sanchez, D. Kosson, R. Keeney, R. DeLapp, L. Turner, P. Kariher, and S. Thorneloe (2008) Characterization of Coal Combustion Residues from Electric Utilities Using Wet Scrubbers for Multi-Pollutant Control, EPA-600/R-08/077, July 2008; www.epa.gov/nrmrl/pubs/600r08077/600r08077.pdf.

F. Sanchez, R. Keeney, D. Kosson, R. Delapp and S. Thorneloe (2006) Characterization of Mercury-Enriched Coal Combustion Residues from Electric Utilities Using Enhanced Sorbents for Mercury Control, EPA-600/R-06/008, February 2006; http://www.epa.gov/ORD/NRMRL/pubs/600r06008/600r06008.pdf.

D.S. Kosson, H.A. van der Sloot, F. Sanchez, and A.C. Garrabrants (2002) “An integrated framework for evaluating leaching in waste management and utilization of secondary materials,” Environmental Engineering Science, 19(3), 159-204.

41

Benefits to Use of LEAF• Provides standardization in leach testing and comparability in

resulting data for use across different materials and management scenarios

• Analytical work complete for all four methods as part of the interlaboratory validation for inclusion into SW-846

• Comparable methods being used abroad enable more robust data sets that provide better characterization across material types and management scenarios

• Provides data needed for binning materials into categories that enable more efficient beneficial use decisions (no or less stringent testing required depending upon the leaching behavior of the material)

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Benefits to Use of LEAF• Industry that generates CCRs and other industrial by-products has

clarity in what is required and access to labs across the U.S.

• Provides objective and independent analysis of claims made by producers or technologies

• LEAF allows one to understand the mechanistic behavior of materials across a range of management scenarios across long terms (can not use snap shot approach that doesn’t consider future environmental conditions)

• Provides robust source term for risk assessment by considering physical and chemical factors that control leaching behavior over time

43

ConclusionsThe LEAF test methods

• Can be used to evaluate leaching behavior of a wide range of materials using a tiered approach that considers the effect of leaching on pH, liquid-to-solid ratio, and physical form

• Prepared for inclusion into SW846 – EPA’s compendium of test methods for waste and material characterization

• Supporting software (LeachXS-Lite) available for data entry, analysis, visualization, and reporting

• Demonstrated relevance for assessing release behavior under field conditions for use and disposal scenarios

Current efforts • Complete interlaboratory validation for Method 1314 and Method 1315• Provide information on

Relationship between the LEAF testing results and field leaching Application of LEAF test methods for evaluating CCR use and disposal

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AcknowledgementsParticipating Laboratories

• Oak Ridge National Lab• Pacific Northwest National Lab• Savannah River National Lab• ARCADIS-US, Inc.• Test America, Inc.• URS Corporation, Inc.

• Ohio State University• University of Wisconsin (Madison)• Missouri Univ. of Science & Tech.• Vanderbilt University• ECN• DHI

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Funding and Support• U.S. EPA, Office of Research and Development• U.S. EPA, Office of Resource Conservation and Recovery• U.S. DOE, Office of Environmental Management • Consortium for Risk Evaluation with Stakeholder Participation (CRESP)