WORKSHOP REPORT
Considerations for Developing
Leaching Test Methods for Semi- and
Non-Volatile Organic Compounds
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EPA/600/R-16/057
April 2016
WORKSHOP REPORT
CONSIDERATIONS FOR DEVELOPING
LEACHING TEST METHODS FOR
SEMI- AND NON-VOLATILE ORGANIC
COMPOUNDS
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Workshop Report
Table of Contents
TABLE OF CONTENTS
NOTICE/DISCLAIMER Ill
ACKNOWLEDGEMENTS IV
ABBREVIATIONS AND ACRONYMS IV
1. INTRODUCTION 1
2. PRESENTATIONS AND RELATED DISCUSSIONS 3
2.1 Presentation: Key parameters or drivers that govern the source term at the
unit boundary for subsurface leaching of semi- (SVOC) and non-volatile
(NVOC) organic chemicals 3
Discussion 4
2.2 What is our field test experience related to organics leaching? 5
Discussion 6
2.3 Estimation of Source Term Concentration for Organics Contained on
Superfund Sites 6
Discussion 7
2.4 European and international standards on leaching of organic contaminants,
available tools and recent developments for assessment of organic
contaminants 7
2.5 What is LEAF for inorganics? What lead to its development? What was the
process and timeline for developing and validating the methods? 10
2.6 Existing Tools and Limitations to Address Leaching of Organic Species 12
3. WORKSHOP DISCUSSION 16
3.1 Key Parameters that Drive Organics Leaching 16
3.2 Important Considerations for Methods Development 17
3.3 Considerations Related to Source Materials and Constituents of Concern 18
3.4 Applicability of LEAF Methods 20
Appendix A:
Appendix B:
Appendix C:
Workshop Agenda
Workshop Participants
Workshop Presentations
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Workshop Report Lists of Tables and Figures
LIST OF TABLES
Table 2-1. LEAF Methods Overview 13
LIST OF FIGURES
Figure 2-1. Association of First Order Expressions to LEAF Leaching Tests 15
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Workshop Report Notice/Disclaimer
NOTICE/DISCLAIMER
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development,
funded the preparation of this report under EPA ContractNo. EP-D-11-006. The Office of Resource
Conservation and Recovery also provided funding for the workshop. This report was subjected to
the Agency's peer administrative review and is approved for publication as an EPA document
Statements captured in the discussion and summaries are those of the participants, not necessarily
reflective of the EPA. Presentations are the responsibility of their authors and may represent
opinions or personal points of view in some cases. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
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Workshop Report Acknowledgements
ACKNOWLEDGEMENTS
Many people contributed their expertise to the development and implementation of this workshop,
and the preparation and review of this publication. This effort would not have been possible
without the efforts of the USEPA and academic experts who participated in the workshop and
assisted in the preparation of this report The document was prepared for Susan Thorneloe of the
Air Pollution Prevention and Control Division of the National Risk Management Research
Laboratory of the USEPA Office of Research and Development under EPA Contract No. EP-D-11-006,
Work Assignment No. 5-10. Co-authors and reviewers of the report include Susan Thorneloe, ORD;
Linda Fiedler and Robin Anderson; Office of Superfund Remediation and Technology Innovation;
and Greg Helms, Office of Resource Conservation and Recovery.
IV
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Workshop Report Acknowledgements
FOREWORD
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between human
activities and the ability of natural systems to support and nurture life. To meet this mandate, EPA's
research program is providing data and technical support for solving environmental problems
today and building a science knowledge base necessary to manage our ecological resources wisely,
understand how pollutants affect our health, and prevent or reduce environmental risks in the
future.
The National Risk Management Research Laboratory (NRMRL) is the Agency's center for
investigation of technological and management approaches for preventing and reducing risks from
pollution that threaten human health and the environment The focus of the Laboratory's research
program is on methods (and their cost-effectiveness) for the prevention and control of pollution to
air, land, water, and subsurface resources; protection of water quality in public water systems;
remediation of contaminated sites, sediments and ground water; prevention and control of indoor
air pollution; and restoration of ecosystems. NRMRL collaborates with both public and private
sector partners to foster technologies that reduce the cost of compliance and in order to
identify/anticipate emerging problems. NRMRL's research provides solutions to environmental
problems by: developing and promoting technologies that protect and improve the environment;
advancing scientific and engineering information to support regulatory and policy decisions; and
providing the technical support and information transfer to ensure implementation of
environmental regulations and strategies at the national, state, and community levels.
This publication has been produced as part of the Laboratory's strategic long-term research plan. It
is published and made available by EPA's Office of Research and Development (ORD) to assist the
user community and to link researchers with their clients.
Cynthia Sonich-Mullin, Director
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
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Workshop Report
Abbreviations and Acronyms
COG
DNAPL
DOC
DOM
EPA
ERG
EU
ISO
ISS
LEAF
L/S
LSP
MCL
MGP
MSW
NAPL
NRMRL
NVOC
ORCR
ORD
OSRTI
PAH
PCB
PTFE
RCRA
SPLP
SVOC
TCLP
UVA
VOC
ABBREVIATIONS AND ACRONYMS
Contaminants of Concern
Dense Non-Aqueous Phase Liquid
Dissolved Organic Carbon
Dissolved Organic Matter
Environmental Protection Agency
Eastern Research Group
European Union
International Organization for Standardization
In Situ Solidification/Stabilization
Leaching Environmental Assessment Framework
Liquid/Solid
Liquid Solid Partitioning
Maximum Contaminant Level
Manufactured Gas Plant
Municipal Solid Waste
Non-Aqueous Phase Liquid
National Risk Management Research Laboratory
Non-Volatile Organic Chemical
Office of Resource Conservation and Recovery
Office of Research and Development
Office of Superfund Remediation and Technology Innovation
Polycyclic Aromatic Hydrocarbon
Polychlorinated Biphenyl
Polytetrafluoroethylene
Resource Conservation and Recovery Act
Synthetic Precipitation Leaching Procedure (EPA Method 1312)
Semi-Volatile Organic Chemical
Toxicity Characteristic Leaching Procedure (EPA Method 1311)
University of Virginia
Volatile Organic Chemical
VI
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Workshop Report Introduction
1. INTRODUCTION
The workshop was hosted by the US Environmental Protection Agency (EPA) on September 16 and
17, 2015 in Arlington, VA to discuss developing leaching test methods for semi- and non-volatile
organic compounds. The purpose of the workshop was to exchange information concerning how to
evaluate the potential for release of semi- or non-volatile organic constituents at contaminated
sites where sub-surface treatment approaches have been applied to control migration, and from
waste that is disposed or re-used. The workshop also considered how to predict sub-surface
leaching potential at the outer edge of the treated media, or in disposal or material re-use
situations, at the unit or use boundary. Representatives from EPA and academia participated in the
workshop. Workshop discussions focused on identifying technical issues for further consideration
to support the development of tools that could be used to make determinations of protectiveness
and regulatory compliance.
Representatives from the Office of Resource Conservation and Recovery (ORCR) and the Office of
Superfund Remediation and Technology Innovation (OSRTI) identified several workshop
objectives, including:
Identify key parameters expected to govern leaching potential of semi- and/or non-volatile
organic constituents from sub-surface treated media (e.g., soils) or disposed waste. The
keys parameters will need to be considered in the development of leaching tests to provide
more accurate source-term data that inform treatment and waste disposal decisions;
Understand how to account for these parameters when evaluating release potential both at
initial treatment and over time (in general, 50-100 years);
Identify methodologies currently used to evaluate organic constituent leaching and their
strengths and weaknesses;
Understand whether the Leaching Environmental Assessment Framework (LEAF)
established for inorganics can be adapted to evaluate leaching of organic constituents; and
Explore how to leverage the best science available to facilitate decision-making.
During the workshop, the following key points related to Superfund site remediation were
discussed to help frame workshop discussions:
Treatment effectiveness is measured at the waste management area boundary;
Clean-up levels are assumed to be known;
Superfund generally deals with site-specific data and information rather than generic or
national distributions of modeled fate and transport scenarios; and
In situ treatment technologies most often used to treat organic contaminants in soil include
soil vapor extraction for volatile organic chemicals (VOCs) and in situ
solidification/stabilization (ISS) for semi-volatile organic chemicals (SVOCs) and non-
volatile organic chemicals (NVOCs).
After the introductory remarks, there were a series of technical presentations followed by related
technical discussions. The information from each presentation is summarized in the remainder of
this report. The report also includes the three appendices listed below.
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Workshop Report Introduction
Appendix A - Presents the workshop agenda,
Appendix B - Provides a list of the meeting participants, and
Appendix C - Contains the presentations.
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Workshop Report Presentations and Related Discussions
2. PRESENTATIONS AND RELATED DISCUSSIONS
As described in the agenda found in Appendix A, the workshop included a series of presentations.
The key points from each presentation are below including summary points from the group
discussion that followed each presentation.
2.1 Presentation: Key parameters or drivers that govern the source term at the unit boundary for
subsurface leaching of semi- (SVOC) and non-volatile (NVOC) organic chemicals
Key points from Dr. Charles Werth's (University of Texas - Austin) presentation:
Factors that either retard or enhance leaching of semi- and non-volatile organics can
include:
Adsorption/desorption;
Multi-phase partitioning; and
Equilibrium vs. diffusion controlled release.
Complex matrices that influence leaching include natural components of soils, sorption
amendments to sequester pollutants, and precipitates that encapsulate pollutants..
Leaching is controlled by the capacity of the different phases for the organic chemical(s) of
interest, and the mass transfer rate from each phase. As water moves through a phase, the
solute goes through advection and dispersion; each phase holds some of the solute (water,
non-aqueous phase liquids (NAPL) - organic or a mixture, and solid), which accumulate in
the phases.
It is possible to approximate leaching from sorbed and NAPL phases with a first order
expression to illustrate dependence on the capacity of each phase for pollutant and mass
transfer rate constant.
The air phase holds little volatile organic chemicals (VOCs), semi-volatile organic chemicals
(SVOCs) or non-volatile organic chemicals (NVOCs) relative to solid and NAPL phases and
contributes little to leaching.
As is it replenished, the water phase represents leachate and serves as a pollutant sink for
other phase. The by presence of salts, co-solvents, dissolved organic matter (DOM), and
colloids affects the capacity of the water phase.
Increasing ionic strength decreases the aqueous solubility;
Altered solubility is related to concentration of the salt
As the salt concentration increases, solubility decreases (lowers the capacity of the
water)
Increasing co-solvent concentration increases the aqueous solubility (e.g., methanol -
changes the structure of the water and increases the capacity of water to hold a solute);
and
Increasing DOM concentration increases the apparent aqueous solubility (or association
with macromolecules).
Leaching capacity of soils and sediments depends on soil/sediment properties and
chemical properties. Soils, sediments, and geosorbent amendments (e.g., char) can sorb
large amounts of VOCs, SVOCs and NVOCs, and slowly release them.
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Workshop Report Presentations and Related Discussions
Equilibrium capacity of these solids is determined by composition;
There are both absorption (or partitioning) and adsorption environments; and
The capacity of the soil partitioning environment for contaminants in absorption
environments can be estimated and is often linear
Adsorption environments are more challenging to characterize, and it is impossible
to predict adsorption; therefore, empirical models are often used
The capacity of adsorption environments for contaminants must be measured; the
relationship between water and soil concentrations is typically nonlinear
Both partitioning and adsorption environments are often present in solids, and the
contribution of partitioning and adsorption environments varies widely depending on
the sorbent.
Mass transfer processes can be complex and occur in parallel or in series.
A simplified model that focuses on multi-phase partitioning and adsorption is needed to
predict mass transfer rates.
Discussion
Consider each phase and identify the capacity and subsequent mass transfer rate.
Capacity is relative to the solubility in water (high capacity = lOOOx or more soluble in
water); and
Mass transfer rate measured as velocity of leaching in a column (cm/min).
Fast = equilibrium
Medium = minutes to hour to days
Slow = many days to weeks/months
Very slow = years
Cement amendments can be in block or granular form and the format can affect the
diffusion length scale (a measure of how far the concentration has propagated over time).
Diffusion coefficient affects the time scale and can be challenging to predict (e.g., if a
contaminant is trapped throughout the cement, the length scale is unknown);
For ISS with equal distribution of NAPL, expect fairly short length scales; and
For ISS with macro-encapsulation (boundary has no NAPL), expect very long length
scales.
The manufactured gas plant (MGP) industry is adding activated carbon to reduce leaching,
and there are questions regarding whether the added components are improving
performance.
An important consideration related to mass transfer is the degree of mixing and conformity
for laboratory prepared mixes compared to the long-term effects of actual treated materials
observed in the field.
Unmixed regions may dominate field results.
The age of NAPL and its duration of contact to soil can influence the rate of leaching of
organic constituents.
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Workshop Report Presentations and Related Discussions
Adding adsorption materials to dilute the concentration of contaminated particles can
create another environment whereby new added capacity delays or slows leaching
(increasing the length scale slows overall mass transfer rate).
Participants discussed ISS conditions that are below the water table. As the water table rises
and falls, pore spaces are occupied and emptied thereby changing the connectivity of space
in the different phases.
VOC transport through gas phase can be fast (i.e., would have a large impact on the rate
at which VOC would leave); and
Mass transfer of SVOCs in NAPLs would slow when water table goes down and increase
again when water table re-rises back.
Participants identified the following key considerations and questions for future work:
The capacity and mass transfer rate constants for each phase determine the relative
contributions to leaching;
Consider and evaluate competing mechanisms when developing a framework to assess
leaching;
Consider the conditions and integrity of materials over time (e.g., carbonation of weak
cementitious material can influence product stability over time);
Simulation of the age of material can be an important factor;
Account for time scales - test at various states (initial, six months, accelerated aging);
Relate time scales of mass release to controlling process to design an experiment
and interpret release/risk
Conduct background research to better understand mixing issues and how to account
for differences between laboratory and field conditions (i.e., represent the potential for
incomplete mixing and lack of mixing in the field);
Identify uncertainties that exist between laboratory and field conditions; and
Consider external factors (environmental conditions) that influence the integrity of
materials (e.g., organoclays).
2.2 What is our field test experience related to organics leaching?
Key points from Dr. Craig Benson's (University of Virginia) presentation:
Dr. Benson discussed his experiences relating barrier experiments in the laboratory to the
field.
He underscored the importance of understanding how the subtleties of experimental design
components can dramatically influence results and predictive outcomes.
Several key issues to consider when designing experimental protocols include:
Account for biological processes and activity of a system when designing experiments;
When running long-term experiments with small amounts of mass, pay significant
attention to experimental design and apparatus - measure and conduct experiments on
design components;
When dealing with small amounts of mass, exercise caution in the quantity of liquid to
extract when sampling to avoid impact on mass transport processes;
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Workshop Report Presentations and Related Discussions
Experimental apparatus can have a significant effect on outcome of transport
experiments with hydrophobic organic contaminants at low concentrations;
Evaluate materials beforehand as sinks for organic contaminants, even in the most
obscure components, to avoid false negatives;
Evaluate apparatus for unintended sinks for organic contaminants (e.g., 0-ring);
Develop expectations for outcomes of experiments to provide a reality check on data;
Accurately model the breakthrough time using simple analytical methods to bracket
expected boundaries;
Recognize the importance of quality control (positive and negative) and method blanks;
and
Understand what you expect to see and measure why you do not
Discussion
Dr. Benson reiterated the potential importance of the relationship and influence of
dissolved organic carbon (DOC) in experimental design following the discussion of DOM
binding in Dr. Werth's talk.
Specifically, how DOC impacts binding and whether the mobility of contaminants would
increase when using real groundwater with DOC over deionized water often used in the
laboratory.
2.3 Estimation of Source Term Concentration for Organics Contained on Superfund Sites
Key points from Dr. Ed Earth's (EPA/ORD/NRMRL) presentation:
Dr. Earth discussed some of the challenges EPA Regions face in providing a quick answer for
evaluating "the source term at the waste management area" for remedies involving ISS of
organic materials (including dense non-aqueous phase liquid [DNAPLs]).
Dr. Earth discussed a variety of methods for pre-placement and post-placement evaluations.
He indicated that EPA and other organizations have guidance for the evaluation of ISS for
organics, but questioned whether there is too much emphasis on physical properties (UCS,
hydraulic conductivity) and not enough emphasis on chemical bonding strength and
leaching mechanisms, especially if free product is present on the site and if colloids are
present in the site around water.
He described one approach to evaluate barrier improvements with an emphasis on
organoclays or activated carbon. Specifically, the focus would be to: (1) evaluate the
bonding strength of activated carbon and organoclay, and (2) determine whether colloids
interfere with bonding strength.
Additional experimental design considerations specific to polycyclic aromatic hydrocarbons
(PAHs), analytical techniques, and data interpretation techniques should include:
Reduction of PAHs in laboratory samples due to photochemical oxidation exposure;
Headspace volatilization;
Dilution;
Sorption onto glassware; and
Oil sheens on sample surface.
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Workshop Report Presentations and Related Discussions
Historical and current laboratory approaches (evaluated by EPA and being proposed by
EPA regional contractors) that EPA Regions use to assess adequacy of
treatment/containment processes include:
Application of a modification to the LEAF Method 1315;
Use of site groundwater;
Use of coated glassware;
Partitioning/NAPL saturation; and
Use of pore water models based upon partitioning.
Discussion
Summary points discussed:
Some EPA Regional Offices have used leaching methods, beyond the toxicity
characteristic leaching procedure (TCLP), to ascertain whether a
treatment/containment process is either adequate to protect the public health and
environment or as a comparison to other treatment technologies;
An array of challenge fluids is available to cover the range of extraction recovery; and
While bonding-strength indicator methods are available, they are rarely used in
treatment evaluations.
More guidance is required if EPA Regions are beginning to use a modification to LEAF
Method 1315 to determine organic leaching.
TCLP remains the regulatory standard for RCRA hazardous waste determinations and land
disposal restrictions requirements and is widely used for ISS effectiveness determination.
2.4 European and international standards on leaching of organic contaminants, available tools
and recent developments for assessment of organic contaminants
Key points from Hans van der Sloot's (Consultant - retired from the Energy Research Center of the
Netherlands) presentation:
Dr. van der Sloot provided an understanding of leaching methods currently in use and the
status of standardization and validation in Europe.
European standardization is split into different fields (soil, waste, mining waste, and
construction products) and methods that may be field-specific. Many fields have boundaries
that are interrelated and therefore, regulators are questioning whether methods need to be
harmonized across fields to promote standardization.
Dr. van der Sloot described parameter differences and adaptations among methods for
organics and inorganics and noted many similarities.
In response to earlier discussions on important parameters, Dr. van der Sloot noted:
Bioactivity/biodegradation is not addressed during the test itself, rather it is dealt with
during sample preparation and storage; and
Address aging by testing at various states (initial, six months, accelerated aging), rather
than designing for aging within the leaching test method itself.
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Workshop Report Presentations and Related Discussions
Important considerations identified through observations from European Union (EU)
standardization activities for leaching standards for organics include:
The fundamental processes that characterize release behavior are not different, and in
many cases information on both organic and inorganic substances is needed; and
Material requirements for the equipment and other parts contacting the eluate are
adapted to meet requirements for both types of substances.
Glass column and stainless steel connections
In the column, quartz sand or glass beads are used instead of filters
It was noted that filtration commonly used for inorganic substances is unsuitable for
organic substances - if needed, centrifugation is recommended
Dr. vander Slootalso noted the importance of the relationship of organics leaching to DOC
and complexation with DOC. He has observed an apparent correlation of PAH with DOC,
hence, indirect pH dependence of PAH leaching. This observation further underscores the
need to understand differing field conditions with the influence of DOC, where increased
DOC can increase leaching potential.
Dr. van der Sloot summarized important take-away messages from the EU experience
developing methods for organics:
Adsorption to Material Surfaces
Match contacting surfaces to organic substances of interest
o Do not use plastics (including Viton), rubber, polytetrafluoroethylene (PTFE)
(PAHs adsorb to Teflon)
o Glass, stainless steel preferable
Volatilization
VOCs are not considered; only semi- and non-volatile organic substances are
considered
Colloid Formation
Because there is more colloid formation in a batch test compared to a column test,
centrifuge eluate rather than use filtration, if at all needed
Eluate Analysis
Always measure pH and DOC; DOC varies as a function of pH and hence water
insoluble organics associated with DOC have increased leachability as pH increases
Demonstrated Higher Release Values from Batch vs. Column Tests
Observations made during the development of International Organization for
Standardization (ISO) standards for soil show batch tests resulted in higher release
values in almost all cases due to higher turbidity and thus higher DOC levels in batch
compared to column
Filtration and/or Centrifugation
In the German test, filtration and centrifugation are not used when the turbidity of
the solution is below a certain value
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Workshop Report Presentations and Related Discussions
Additional key concepts that should be considered include:
Liquid-solid partitioning;
pH - indirectly relevant due to dependence of DOC on pH
Liquid-solid ratio
Redox - not directly relevant
Dissolution/sorption
Particulate and DOM interaction
Eluate Chemistry
Mass transport; and
Diffusivity
Surface area
Surface interactions (local equilibrium)
Limitations.
Degradation of organic substances (after results are available, happens in the
analysis)
Degradation of organic matter and associated DOC formation (time-lapsed issue)
Sorption on many surfaces
Volatilization
Important observations were shared, including:
Use of a common leaching conceptual framework and related standardized test methods
will allow for comparability of results across contaminants, sources of contaminated
materials, scenarios and regulatory jurisdictions.
Standardized tests show systematic release patterns for organic contaminants to
further understanding of release mechanisms;
Methods are aimed to simultaneously address both inorganic and organic substances to
facilitate ecotoxicity testing of eluates;
Dissolved organic matter plays an important role in release of semi- and non-volatile
organic substances due to their association with DOC;
Transport properties are controlled by the substance itself and by the transport
properties of DOC;
The pH dependence of DOC release is important because the association of organics
with DOC impacts organics partitioning and transport;
Release of organic substances from monolithic products (e.g., stabilized waste and
treated wood) is, primarily controlled by the release of DOC-bound organic substances
and thus controlled by DOC release. DOC release from porous monolithic materials is
about a factor 10-15 times slower than the release of soluble salts (e.g. Na+, K+, C1-);
DOC-associated organic substances are notbioavailable for a range of organisms
currently applied in ecotoxicity testing and thus have no toxic response;
Partitioning of DOM in sub-fractions (fulvic and humic substances) may prove
important, in view of their different binding characteristics for organic contaminants;
and
The use of soil adsorption coefficient (Koc) parameters allows the partitioning of
organic contaminants to be estimated between particulate and DOM.
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Workshop Report Presentations and Related Discussions
There were no tests have addressed specifications for leaching water (i.e., specifications for
pH and DOC) and therefore underscores the importance of a pH dependence test to
understand the impacts.
2.5 What is LEAF for inorganics? What lead to its development? What was the process and
timeline for developing and validating the methods?
Key points from Greg Helms' (EPA/ORCR) and Susan Thorneloe's (EPA/ORD/NRMRL)
presentations:
Greg Helms provided an overview of LEAF for inorganics, what led to its development and
the process and timeline for developing and validating the methods.
The TCLP is a generic leaching test representing an eluant pH = 4.98 (that of active decay
phase in a municipal solid waste [MSW] landfill); TCLP is broadly used and in many cases
inappropriately applied (e.g., at conditions not representative of the pH).
Given the deficiencies and challenges of TCLP, EPA was urged to evaluate other more
representative methods to estimate and predict leaching that provide a better
representation of what is likely to occur.
LEAF methods have broad applicability across materials and enable one to compare:
- pH;
Liquid-to-solid (L/S) ratio; and
Particle size.
LEAF results can be very useful when you gain economies of scale when analyzing waste
management and re-use options for large quantities of waste.
Susan Thorneloe provided background on the importance of establishing methods that provided a
more accurate depiction of leaching based on a range of environmental conditions. There was a
need to have a more holistic understanding of the impact of air pollution control technologies at
coal-fired power plants to ensure pollutant transfers were not delayed or shifted from one media
into another. Acros the U.S., coal-fired power plants were implementing wider spread use of air
pollution control technology such as the use of selective catalytic reduction for post-combustion
NOx removal, electrostatic precipitaters or fabric filters for particulate capture, sorbent injection
for increasing mercury control, and flue gas desulfurization or other scrubber technologies to
reduce acidic gases in the stack emissions. When these pollutants are transferred from the air stack
at coal-fired power plants to the fly ash and other air pollution control residues, the concern is
whether the pollutants may be later released when the air pollution control residues are utilized for
beneficial use or land disposed. [Thorneloe S.A., 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 and Technology, 44, 7351-7356.]
LEAF is a collection of:
Four leaching methods;
Data management tools;
Geochemical speciation and mass transfer modeling;
Quality assurance/quality control; and
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Workshop Report Presentations and Related Discussions
Integrated leaching assessment approaches.
LEAF is designed to identify characteristic leaching behaviors for a wide range of materials
and associated use and disposal scenarios to generate material- and site-specific source
terms.
LEAF is not a replacement for TCLP but instead is used when TCLP is not considered
applicable or appropriate. Uses include:
Assess materials for beneficial use;
Evaluate treatment effectiveness (equivalent treatment determination);
Characterize potential release from high-volume materials; and
Corrective action (remediation decisions).
LEAF provides a source term for future modeling and facilitates comparing data across
materials when using a common framework.
LEAF includes data management tools to facilitate implementation, including:
Spreadsheets to help manage data and pre-calculate required values (e.g., titration);
Form upload to the materials database; and
Software for processing and results visualization.
Susan shared important lessons learned through the LEAF development, including:
- Modifications to Methods 1313 and 1316;
Tolerance for contact time was added
Requirement that pH values be measured within one hour after separation of solids
and liquids due to lack of buffering in aqueous samples
Modifications to Data Templates; and
Mandatory information is highlighted
Instructions more closely follow method text
Other Considerations.
Calibration of pH meters should cover entire pH range to extent possible
Reagents should be freshly prepared, stored in vessels of compatible materials (e.g.,
strong alkalis not be stored in borosilicate glass)
Laboratories should establish a QC regimen to check the quality of reagent water
(method blanks are important)
Susan discussed lessons learned from the validation effort and suggested the following:
Engage laboratories and ensure they follow the instructions;
Brief participating laboratories through interactive webinars;
Walk participating laboratories step-by-step through the process;
Conduct methods training;
- Conduct QA/QC; and
Ensure conformance to the method.
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Workshop Report Presentations and Related Discussions
2.6 Existing Tools and Limitations to Address Leaching of Organic Species
Key points from Dr. David Kosson's (Vanderbilt University) presentation:
Dr. Kosson described the capabilities of existing leach test methods to measure factors that
impact organic leaching.
Dr. Kosson provided an overview of leaching control factors, including chemical factors and
physical factors, coupled with release mechanisms of wash off, dissolution and diffusion.
The distinction between simulation-based and characterization-based leaching approaches
was discussed:
Simulation-based Leaching Approaches:
Designed to provide representative leachate under specified conditions, simulating
a specific field scenario
Eluate concentration assumed to be leachate (source term) concentration
Simple implementation (e.g., single-batch methods like TCLP or Synthetic
Precipitation Leaching Procedure [SPLP]) and interpretation (e.g., acceptance
criteria)
Limitations
o Lack of Representativeness of testing to actual disposal or use conditions
o Results cannot be extended to scenarios that differ from simulated conditions
o Basis for comparison of results from different materials is often unclear
Characterization-based Leaching Approach:
Evaluate intrinsic leaching parameters under broad range of conditions
More complex; sometimes requiring multiple leaching tests
Results can be used to conduct "what if" analyses of disposal or use scenarios
Provides a common basis for comparison across materials and scenarios
Materials testing databases allow for initial screening
Dr. Kosson provided an overview of existing methods in practice and identified limitations
for organic contaminants.
LEAF methods were discussed, including the rationale and limitations for use with organics:
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Workshop Report
Presentations and Related Discussions
Table 2-1. LEAF Methods Overview
Method
Rationale
Limitations for Use with Organics
1313
Designed to provide Availability and
Liquid-Solid Partitioning (LSP) as a
function of pH. Also provides acid/base
titration and basis for chemical
speciation modeling
Focus on end-state conditions (pH, L/S,
DOC, etc.)
Particle size and contact intervals,
mixing to approach equilibrium
Conceptual paradigm is applicable for
organic species
Availability determination approach not
applicable for organics although some organic
constituents or fractions thereof partition
strongly to natural organic matter or NAPLs,
resulting in a very readily available fraction for
leaching and a more slowly or recalcitrant
fraction for leaching.
pH domain beyond the relevant scenario pH not
needed
Eluent and mixing conditions do not address
potential for deflocculation and colloid formation
(column test minimizes inadvertent release of
DOC; can get higher results from batch testing vs
column)
Provisions for selection of apparatus materials,
filtration, sample mass, extraction volumes,
minimizing volatilization losses are not provided
Many methods do not provide sufficient guidance
on what is "applicable"
1314
Designed to provide LSP as a function of
L/S (elution curve). Approximates initial
pore water and linkages between
individual species leaching (e.g., DOC &
chloride complexation, depletion of one
species leading to increased release of
another)
Particle size, dimensions, flow rate, to
approach equilibrium. Eluent to avoid
deflocculation
Conceptual paradigm is applicable for
organic species
Availability determination approach not applicable
for organics; percolation column approach can be
used to indicate readily leachable fraction of
organic contaminants but also must be sensitive to
leaching kinetics.
pH domain beyond the relevant scenario pH not
needed
Eluent and mixing conditions do not address
potential for deflocculation and colloid formation
(column test minimizes inadvertent release of
DOC; can get higher results from batch testing
compared to column)
Provisions for selection of apparatus materials,
filtration, sample mass, extraction volumes,
minimizing volatilization losses are not provided
Many methods do not provide sufficient guidance
on what is "applicable"
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Presentations and Related Discussions
Table 2-1. LEAF Methods Overview
Method
Rationale
Limitations for Use with Organics
1315
Designed to provide maximum release
flux (mass transport rate) by maintaining
dilute boundary condition
Closed vessels to minimize atmospheric
exchange (COz, Oz)
Interpretation includes consideration of
field scenario boundary conditions
Conceptual paradigm is applicable for
organic species
Provision for in-situ solid phase extraction not
provided (variants have been developed but not
standardized)
Provisions for selection of apparatus materials,
filtration, sample mass, extraction volumes,
minimizing volatilization losses are not provided
1316
Designed to provide LSP as a function of
0.5 < L/S < 10 mL/g dry material.
Provides basis to approximate early
leachate concentrations and
determination of availability or solubility
controlled leaching
Particle size and contact intervals,
mixing to approach equilibrium
Conceptual paradigm is applicable for
organic species
Eluent and mixing conditions do not address
potential for deflocculation and colloid formation
resulting in a potential bias towards higher release
estimates.
Provisions for selection of apparatus materials,
filtration, sample mass, extraction volumes,
minimizing volatilization losses are not provided
Key take-aways from Dr. Kosson's presentation include:
Measurement of intrinsic leaching characteristics and development of source terms
based on mass balance, thermodynamic and mass transport principles provides a
robust leaching assessment framework that is applicable to both inorganic and organic
species;
Numerical modeling may be warranted when direct extension of laboratory results to
field conditions is not applicable and analytical solutions are not available;
A tiered approach to source term estimation provides for a balance between extent of
testing, complexity of source term development, and end-user needs, thus allowing
users to assess the costs associated with specific tests compared to the benefits gained
based on their needs;
Current LEAF test methods do not include specifications specific to many classes of
organic species; and
Important factors that are not addressed specifically for organics include:
Selection of apparatus materials, filtration, sample mass, extraction volumes,
minimizing volatilization losses, maintaining "dilute" boundary conditions (for
monoliths)
Use in source terms does not address NAPLs and vapor phase transport
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Presentations and Related Discussions
Discussion
The LEAF framework allows you to run computational what-if scenarios.
It is important to understand the difference between exposure conditions and field
conditions and make the appropriate modifications.
As shown in the figure below, Dr. Kosson was able to relate the first order reaction equation
addressed in Dr. Werth's talk that identifies key drivers with elements of LEAF methods
that permit measurement of key components to predict leaching of organics. LEAF leaching
test methods are designed to measure the available content, liquid-solid partitioning and
mass transfer rates to facilitate development of scenario-specific leaching source terms.
Can Approximate Leaching From Sorbed
and NAPL Phases with a First Order
Expression to Illustrate Dependence on
Capacity of Each Phase for Pollutant and
Mass Transfer Rate Constant
TT^C, dC.
=OD ,'-q
* 2
F
Available or Tola!
Courtesy C. Herlh, U. Texas
Solute in NAPL governed by mass transfer to water:
. -mass transfer rate constant, k,4
L "^ij -aqueous solubility, C^,
LSP(Eq. lซacll lest)-bulk aqueous concentration, C,
Solute in solid governed by mass transfer to water:
v f-Nr\ -mass transfer rate constant, kj
"?*-ซ ) -sorbed phase concentration, C^ne
bulk aqueous phase concentration, C4
-isotherm parameters, Kf, Nf
Figure 2-1. Association of First Order Expressions to LEAF Leaching Tests
There is a need to make the jump to practical implementation, recognizing constraints and
coming to a reasonable compromise.
Understanding pH dependence is important given that there may be situations where the
pH could shift over time and therefore influence leachability (e.g., if there is a breakdown of
organic matter in capped material and subsequent influx of dissolved organic matter
capable of mobilizing organics). Changes in pH also may occur in response to biological
processes.
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3. WORKSHOP DISCUSSION
Additional discussion followed the conclusion of presentations and continued through the morning
of Day 2. Discussion topics are summarized below and are organized by related topics.
3.1 Key Parameters that Drive Organics Leaching
In measuring organic leaching, two systems are in effect: 1) a percolation system and 2) a
diffusion system.
There are many factors to consider, not all of which are always a concern; therefore, there is
a need to identify the most important factors.
Participants described external field considerations to consider when designing an organics
leaching test:
Presence of a discrete organic phase;
- Presence of SVOCs and VOCs;
Physical form of the material;
Groundwater velocity;
Water quality/composition;
DOC, which may vary seasonally
Ionic strength
pH
Bioavailability of study material;
Depth to groundwater;
Temperature;
Reasonably translating temperature fluctuations (laboratory vs. field)
Controlled conditions
Weathering may be a factor depending geographic location and whether waste is
located above freeze-thaw line;
Diffusion
Extent of mixing/homogeneity
Durability testing
Diffusion changes based on degradation in material
Climate change factors, for example, seawater intrusion
Sampling to control microbial variables;
Representative and compositing sample collection; and
Consider whether remediation treatment itself could affect other areas of site (e.g.,
by changing the pH or adding DOC).
Participants described analytical parameters that impact leaching of organic constituents:
- pH;
Temperature;
Physical size and form of the material (granular or monolithic), which affects mass
transport distances;
L/S or water contact time, velocity, and volume;
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Composition of water used in testing;
Ionic strength
DOC
Test type: batch, column, or monolith;
Laboratory equipment compatibility and degradation (steel, coated glass, maybe
Teflon);
Scale of apparatus
Preservation to prevent degradation
Local equilibrium;
Eluate composition;
Age of sample;
90 day maximum age
Scale of apparatus;
Laboratory equipment suitable for testing organics;
Testing over time, to capture constituents that increase in solubility over time;
Design the leaching test to inform the decision maker about whether
solidification/stabilization is an appropriate treatment
Location of material relative to boundary; and
Comparability of leaching test result with the analogous analytical test method (solid
extraction).
Other potentially problematic or confounding leaching factors include:
Reducing conditions cause chlorinated compounds to leach first;
Treatment may change diffusion behavior; and
Oily wastes present a challenge to evaluate because of physical constraints of the testing
equipment and difficulties in interpreting the results.
3.2 Important Considerations for Methods Development
Through the presentations, participants gained a better understanding about the
fundamental mechanisms that affect the release of organics. The challenge now is to identify
key drivers, balancing practicality and costs, while remaining scientifically defensible. A
framework considering a phased or tiered approach may be appropriate to handle a broad
range of waste materials.
Participants expressed a desire to simplify the system, identify key parameters, and
translate components into a first order reaction.
The following questions are important to consider related to implementing an evaluation-
based approach using both modeling and testing:
How much modeling?
How much leach testing?
Are we addressing materials evaluation?
Can modeling to isolate variability be developed?
A participant noted that if a batch equilibrium test was conducted, one could run the test
where the concentration in water was close to zero to permit the calculation of maximum
flux out when the driving force concentration is known. One can relate max flux out to
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calculate water out (percolation rate) to compare against a maximum contaminant level
(MCL) (by transforming the first order rate equation to solve for MCL).
Only the bulk measurement is needed to understand the percolation rate
A step function could be an input for comparative assessment (i.e., current state, remediated
state or measure of treatment effectiveness).
The difference of results between batch and flow-through systems was discussed and when
to use each.
Column tests provide a practical dilution curve
Batch tests provide an indication for bounding modeling conditions and provide a worst
case scenario where if concentrations are below regulatory thresholds there is no need
to test further
The following issues are related to organic leaching and leach testing:
- Mobility of NAPL
Impact of mixing
Durability of treatment technology
Effective compliance monitoring at sites to assess treatment effectiveness
Quality assurance and quality control protocols to measure whether what was built was
as designed
Performance specifications for ISS
Uniformity of solidification/stabilization amendment mixing)
Other considerations related to test specifications:
An opportunity exists to modify existing methods to address material and head space
requirements to meet the needs for both inorganic and organic substances whereby a
single method could exist that addresses any required protocol deviations that may be
substance-specific
Requirements for leaching tests and analytical techniques can be collectively addressed
if a larger system is designed or a wider column is used
Cleanup levels with very low detection levels will require large volumes of waste
material to adequately assess
In partitioning testing, it may be necessary to measure DOC in solid and aqueous phase
as DOC will vary in different environments
If material contains a high levels of DOC (e.g., from natural organic matter), testing
results will likely result in increases in mobility of organic compounds.
3.3 Considerations Related to Source Materials and Constituents of Concern
Participants discussed how NAPLs will initially dominate phases, followed by partitioning
environments, and then adsorption environments.
It is possible to flush the system or conduct an extraction to isolate NAPL and then
separate from what is sorbed to understand the capacity of the fraction; otherwise,
another approach is to use the total mass
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Workshop Report Workshop Discussion
If the fraction capacity is known, how fast the NAPL is flushed would indicate the mass
transfer rate
The mass transfer rate could then be parameterized for a leaching test
MCL could be used with known volume of water to back calculate representative
velocity - Representative velocity is the ratio of mass that comes out in a certain volume
of water to predict retention time
With regards to NAPL leaching:
A batch equilibrium test would evaluate mass transfer, and provide an upper limit
(worst case)
A column test with pulverized material would estimate flux from stabilized material
EPA presented preliminary data for organic contaminant groups found at Superfund sites to
introduce the discussion of disposal scenarios and wastes that may require leaching testing
for organics. Based on an analysis of Superfund decision documents (e.g., Records of
Decision, Amended Records of Decision), both volatile and semi-volatile organic
contaminants are common at Superfund sites. For example:
Halogenated volatile organic compounds (primarily chlorinated VOCs) are
contaminants of concern (COCs) at approximately 70 percent of these sites
PAHs are COCs at half of the sites, and other semi-volatile organic (e.g.,
pesticides/herbicides, polychlorinated biphenyl (PCBs) are also common
Based on four recentyears (Fiscal Years 2009-2012), 18 decision documents include a
solidification/stabilization remedy for organic contaminants. Of these, about half have
or may have NAPLs, and about half are using solidification/stabilization as a
pretreatment prior to offsite disposal
Common contaminant distinguishing characteristics include:
Polarity
Hydrophobicity
Non-Ionic
Ionic (not likely a problem but pH can become an issue)
Priority organics of concern include:
Organo-metallic compounds
Combined contaminants
Mercury
The 40 constituents regulated in the 1990 Toxicity Characteristic (TC) Rule may be a good
starting point for organic constituents for which to consider testing. Note that the TC Rule
was developed at a time when MSW landfills did not have liners and many industries of
today did not exist; therefore, some of the underlying assumptions are dated.
Could initially consider the basic parameters that govern the release of the majority of
organic contaminants and situations, recognizing there will be exceptions, and then
design a flexible system that can accommodate most constituents and matrices
Some organic contaminants are recalcitrant, transform in the environment, and are toxic at
low levels; the potential occurrence and toxicity of daughter products is also a concern, as
well as preventing them from mobilizing into groundwater.
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Workshop Report Workshop Discussion
Participants briefly discussed scenarios where leaching of organics may be of concern:
Leaching related to industrial waste is the focus EPA's Resource Conservation and
Recovery Act (RCRA) program
Waste pharmaceuticals (expired products) management was mentioned, but workshop
participants noted direct exposure is also a concern in addition to leaching
The need to identify specific examples of scenarios that may be most problematic for
leaching was discussed
From an EU perspective, a lesson learned was to develop methods based on the material
rather than the application to reduce the number of duplicative test methods
Participants discussed scenarios where leach tests would be needed:
For Superfund, EPA is managing old contaminated sites
For RCRA, EPA is dealing with newly generated waste. Focus is primarily on the existing
list of approximately 40 constituents listed in the regulation, but also dealing with
industries that did not exist at the time of regulation. The primary focus is on industrial
waste
Could consider worst case scenarios (e.g., weathering scenario that includes degraded
[crumbled] source material) from a chemical and physical stability perspective when
designing leaching tests to account for a wide range of external conditions to ensure test
results reflect worst case conditions.
Concrete is another example of a material that often cracks under external conditions and
may be best represented by a monolithic sample in the laboratory, rather than a pulverized
sample. The movement of constituents through concrete depends on the movement of
water by gravity and interconnectedness of cracks.
Regarding representative site samples, Dr. van der Sloot indicated that research from a
heterogeneous MSW landfill site showed that the composition of the leachate was rather
homogeneous and consistent throughout the face of excavation.
Testing a composite sample by the full tests in conjunction with single step tests (own pH
batch) on spatially distributed samples can be used to place site-wide variability in
perspective to the more detailed information provided by the full testing of a composite
sample. This approach provides for detailed information at reasonable cost.
Laboratory quality assurance and quality control procedures, including sample preparation
techniques and separation procedures, are important.
Conducting training and outreach (e.g., through webinars) for both policymakers, regulators
and laboratories could improve stakeholders' understanding of the factors that affect
organics leaching and important nuances related to conducting leaching tests.
3.4 Applicability of LEAF Methods
Participants reiterated that a leaching framework is a scientific evaluative tool that provides
more accurate characterization of leaching that can be considered within a regulatory
decision framework.
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Workshop Report Workshop Discussion
It is important to consider the purpose of the leaching test (define how the data will be
used), desired testing output, and define a decision pathway such as an elution curve, L/S
equilibrium, mass transfer, or NAPL concentration.
The LEAF How-to Guide that is currently being developed for inorganic constituents
describes the suite of tests, the use of simplified screening level testing, as well as more
detailed characterization to compare results to known thresholds. The document offers
guidance on how to select the appropriate test for the material of interest. LEAF methods
can be useful for evaluating multiple inorganic contaminants with unknown release
potential.
Suggested applications of a leaching test framework at waste cleanup sites included:
To estimate contribution of a source material to mass flux and transport, given
heterogeneous distribution of contaminants often seen at contaminated sites;
To support treatability studies and provide insight on the best combination of remedial
technology to use; and
To support performance monitoring.
A leaching test framework could be useful to make a "go" or "no go" decision for whether to
apply stabilization treatment.
Leaching test methods may be used to estimate release rate at the physical boundary of
the treated/stabilized waste as an indicator of performance
Participants were reminded that leaching test methods evaluate the leaching potential of
the source material; leach test results are then used in fate and transport modeling to
predict future groundwater concentrations.
The LEAF testing methods are basic scientific tools that offer results that can then be
evaluated within the context of a specific scenario. The existing LEAF framework
established for inorganic contaminants is flexible enough that the specific context of the
waste material can be considered after generating test results. This logic is in contrast to
TCLP where the context of the waste material is considered prior to testing.
Participants discussed how to evaluate whether methods adequately predict leaching. Dr.
van der Sloot noted that the EU does not currently have data on organics to compare what
was predicted through testing and modeling to what was observed in the field, but through
the sustainable landfill project such data should be available in 2016.
It would be best to integrate laboratory testing, modeling, and field results to assess the
accuracy of predictions based on laboratory data (analogous to the approaches taken
for inorganic contaminants, e.g., Lab-to-Field study). No or very limited data is available
today.
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Appendix A
Workshop Agenda
A-l
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A-2
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Workshop Participants
USEPA Workshop on Considerations for Developing Leaching Test Methods for
Semi- and Non-Volatile Organic Compounds
Workshop Agenda
Day 1: September 16, 2015 (Wednesday)
Presentation/Discussion
Objective(s)
Welcome, Logistics, and Introductions
Presenter or Moderator
Linda Fiedler, OSRTI
Workshop Objectives
Purpose of workshop for ORCR and
OSRTI
Greg Helms-ORCR
Robin Anderson - OSRTI
Key Parameters or Drivers that Govern the
Source Term at the Unit Boundary for
Subsurface Leaching of Semi- (SVOC) and
Non-Volatile (NVOC) Organic Chemicals
Identify factors that either retard or
enhance leaching of semi- and non-
volatile organics (e.g., adsorption/
desorption/multi-phase partitioning,
equilibrium vs diffusion controlled
release).
Charles Werth,
University of Texas -
Austin
What is our field test experience related to
organics leaching?
Estimation of Source Term Concentration for
Organics Contained on Superfund Sites
What problems are being encountered
in real-world applications from
estimation of source term
concentration at the unit boundary
using present methods?
Craig Benson, University
of Virginia
Ed Barth, ORD/NRMRL
European and International Standards on
Leaching of Organic Contaminants, Available
Tools and Recent Developments for
Assessment of Organic Contaminants
Provide understanding of what
currently is in use and the status of
standardization and validation.
What is LEAF for inorganics? What lead to its
development? What was the process and
timeline for developing and validating the
methods?
Provide understanding of work done
to develop and validate LEAF.
Hans van derSloot,
Consultant (retired from
the Energy Research
Center of the
Netherlands)
Greg Helms, ORCR
Susan Thorneloe,
ORD/NRMRL
What laboratory methods are available to
measure the factors that impact leaching of
semi- and non-volatiles?
Identify laboratory methods that
measure the factors that impact
organics leaching.
Greg Helms (Moderator)
Existing Tools and Limitations to Address
Leaching of Organic Species
Describe capabilities of existing leach
test methods to measure factors that
impact organic leaching, and which
factors existing methods cannot
address.
David Kosson,
Vanderbilt University
Day 2: September 17, 2015 (Thursday
Review of Day 1
Greg Helms, ORCR
What are the capabilities of existing leach
test methods to measure factors that impact
leaching of semi- and non-volatiles?
Discuss capabilities of existing leach
test methods to measure factors that
impact organic leaching, and which
factors existing methods cannot
address.
Greg Helms
(Moderator)
What are the source materials, matrices and
constituents of potential concern and how
are these considered in determining the
reference materials?
Identify reference materials,
representative matrices, and
constituents.
Dave Jewett, ORD
(Moderator)
Closing Remarks and Adjournment
Linda Fiedler
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Workshop Report Workshop Participants
Appendix B
Workshop Participants
B-l
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Workshop Report Workshop Participants
B-2
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Workshop Report
Workshop Participants
USEPA Workshop on Considerations for Developing Leaching Test Methods for
Semi- and Non-Volatile Organic Compounds
Workshop Participants List
Name
USEPA
Robin Anderson
Linda Fiedler
David Bartenfelder
Greg Gervais
Pamela Barr
Jeff Heimerman
Kathy Davies
Greg Helms
Schatzi Fitz-James
Shen-Yi Yang
Christie Langlois
Susan Thorneloe
David Jewett
Ed Barth
Kelly Smith
OTHER PARTICIPANTS
David Kosson
Hans van der Sloot
Craig Benson
Charley Werth
Molly Rodgers
Katie Connolly
Organization
Office of Superfund Remediation and Technology Innovation (OSRTI)
OSRTI
OSRTI
OSRTI
OSRTI
OSRTI
Region III
Office of Resource Conservation and Recovery (ORCR)
ORCR
ORCR
ORCR
Office of Research and Development (ORD)/National Risk Management Research
Laboratory (NRMRL) (Research Triangle Park)
ORD/NRMRL(Ada)
ORD/NRMRL (Cincinnati)
ORD/NRMRL (Cincinnati)
Vanderbilt University
Consultant (retired from the Energy Research Center of the Netherlands)
University of Virginia
University of Texas (Austin)
Eastern Research Group, Inc. (ERG) (EPA Contractor)
ERG (EPA Contractor)
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Appendix C
Workshop Presentations
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Key parameters or drivers that govern the source
term at the unit boundary for subsurface leaching
of semi- (SVOC) and non-volatile (NVOC) organic
chemicals
Charles Werth
Civil, Architectural, and Environmental
Engineering
UT Austin
VOCs, SVOCs and NVOCs Are in Air,
Water, Solid, & NonAqueous Liquid
Phases
Solid Phases
Include:
1) Natural
Components
of Soils and
Sediments
2) Sorption
Amendments
to Sequester
Pollutants
3) Precipitates
that
Encapsulate
Pollutants
Luthyetal., ES&T, 1992
Leaching is Controlled By the Capacity^
of the Different Phases for the Organic
of Interest, and the Mass Transfer Rate
from Each Phase
This Can Be Expressed Mathematically By the Simplified Expression
Below For Pollutant Removal Mechanisms in Leachate
!T+pNa+fV
at
Solute Solute
accumul accumul
ation in ation in
leachate NAPL
Mass Transfer
Between Phases:
Solute
accumul
ation in
solids
d C dC
dx2 dx
Solute Solute
dispersion advection
/diffusion in leachate
in leachate
Mass Transport
in Water:
Can Approximate Leaching From Sorbed
and NAPL Phases with a First Order
Expression to Illustrate Dependence on
Capacity of Each Phase for Pollutant and
Mass Transfer Rate Constant
aca
ป~3T
at
aeN
~3T
at
acso a2ca
-- " a~2
3x
aca
at
dC
SORB _
"77 '
Solute in NAPL governed by mass transfer to water:
-mass transfer rate constant, kLa
-aqueous solubility, CSOL
-bulk aqueous concentration, Ca
Solute in solid governed by mass transfer to water:
-mass transfer rate constant, ks
-sorbed phase concentration, CSORB
-bulk aqueous phase concentration, Ca
-isotherm parameters, Kp NF
C-3
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Air Phase Holds Little SVOCs or NVOCs^
Relative to Solid and NAPL Phases, and
Contributes Little to Leaching
Capacity of air to
hold contaminants is
very small (ซ 1%)
- low fugacity capacity
or low Psat
Mass transfer
between air and
leachate water is
relatively fast
seconds to minutes
(modified from Schwarzenbach et al., 1993)
Water Phase Represents Leachate, and
Serves As a Pollutant Sink For Other
Phases As It is Replenished
Capacity of water
to hold SVOCs and
NVOCs is typically
small
Is affected by
presence of salts,
cosolvents,
dissolved organic
matter (DOM), &
colloids
plaining C mpoundp
3olychlori rated Biphenyls fCBs) i i
C4cfe j CCI2F
Cwsatwatersolubility (mg/L]
(modified from Schwarzenbach et al., 1993]
Increasing Ionic Strength Decreases
the Aqueous Solubility
Pure
SVOC
sat
C
= KSC
mol
Water
and
salt
[salt]tot (mol/L)
Ks = "salting out" constant, (~ 0.15-0.3; e.g. Benz = 0.19, Naph = 0.22 in NaCl solutions)
Cwsnlsnt= saturation concentration in water with salt [mol L"1; g L"1]
Cwsat = saturation concentration in distilled water [[mol L"1; g L"1]
. . ,, (Schwarzenbach et al., 1993)
C , = salt concentration [mol L"1]
Increasing Co-Solvent Concentration
Increases the Aqueous Solubility
Pure SVOC, NVOC
Water and cosolvent
e. g. methanol
W
sat -
= C
sat
(af \
CwCosat = saturation concentration in presence of cosolvent [mol/L; g/L]
fco = fraction of cosolvent [-]
(7 = solubilization constant [-] or "cosolvency power"
(7 increases with decreasing water solubility of the cosolvent a (increasing
hydrophobicity Kow.}
C-4
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Increasing Dissolved Organic Matter
Concentration Increases the Apparent
Aqueous Solubility
Pure SVOC, NVOC
Water with DOC
$at
c*
ฐ
'at
^ sat f Tf
-w JDOC^DOC
CwDOCSDt = saturation concentration in presence of DOC [mol I/1; g I/1]
/DOC = fraction of dissolved organic carbon [kg L1] (e.g.: Humic-, fulvic acids, surfactants)
KDOC = partitioning coefficient organic carbon / water (L kg"1).
KDOC increases with decreasing water solubility (increasing Kow } of the solute and increasing
hydrophobicity or molecular weight the DOC (KDOC < Kow )
Soils, Sediments, and Geosorbent
Amendments Can Sorb Large Amounts
of VOCs, SVOCs and NVOCs, and Slowly
Release Them
Leaching capacity of soils and sediments
depends on soil/sediment properties and
chemical properties
Leaching rate depends
on concentration gradient
between sorbed phase
and water, and mass
rate constant 5CSOB
at
Equilibrium Capacity of These Solids is
Determined by Composition
There are both absorption (or partitioning)
and absorption environments
- Partitioning environments
Relatively unweathered and/or recent soil organic
matter
Capacity to hold contaminants can be large, and
depends on amount of this organic matter
Mass transfer from this soil organic matter is relatively
fast (hours to days) compared to soil adsorption
environments
- Can assume equilibrium partitioning at low water flow rates
- At higher water flow rates can approximate as first order
Capacity of Soil Partitioning Environment
for Contaminants Can be Estimated
Relationship between concentrations in water
and recent soil organic matter is often ~linear
~ ^d ~ '-sorbed / '"water
Kd can be directly related to amount of
organic matter and hydrophobicity of
chemical
~ Kd - Koc * foe
Where
C-5
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Many Relationships Koc and Kow Have
Been Proposed and There is Lots of
Supporting Data
The relationship by
Karickhoffetal. (1979) is
perhaps the most common
- Log(KJ = 1.00 *log(K0J-0.21
Adsorption Environments Are More
Challenging to Characterize
Adsorption Environments
Thermally altered and/or condensed organic matter and
black carbon
E.g., Soot, charcoal, kerogen
Mineral Surfaces, e.g., Clays
Composite Amendments
Organoclays, activated carbon embedded in cements
Capacity to hold contaminants can be very large, and
depends on many factors, e.g., microporosity, surface
area, and surface charge
Mass transfer from adsorption environments can be
very slow
Leaching for months to years to decades
Natural
Materials
Become
Thermally
Altered Over
Geologic Time
With Burial
l
a
3
1
1
I
3
1
a
1
1
oEs. ^HH?d?i,hHLH
\ Pd^menzatltm PRS^
Recent HumlcAcld, Biological
Sediment M"ic Acid, Marker,
, J 1 jzggqj
[pf
^nncipa, zone |1 Hydrocarbons
of oil formation \^ Low to high
medium MW MW
jCraclmigl /Cradang |
iS ^
fo'rmatio^n8 P^~^ Light Hydrocarbons
| Residue |
sg
Crude
Oil
T^
^T"
Some Thermally Altered Sorbents Are
Anthropogenic in Origin
Soot
Combustion product of hydrocarbons
Char
Solid phase residual from biomass burning
Activated Carbon
followed by activation by exposure to acid,
oxidizing, or reducing conditions at elevated
temperature
C-6
-------
The Extent of Adsorption Varies with
Sorbate and Sorbent
1 EH>T
..HปW
I.EH0
I.EMM
I.IWM
UMO
irui if'ttj
I f'0> ITrtOl I E-fl4
The Extent of Sorption Has Been
Related to Surface Area, Pore
Volume, and Microporosity
o-Kresol
ABenz
DICE
ซ1,2DCB
4PHE
! XX
,x */
hgni
charcoal
bit coal * ,""'""
ง ,,""*'
.f'
lignite
PolyguardR ,..-
a carbon --^_..-jj'-1
ecoke ,"'"
A'. S-eY-2ฐฐ
I8
\
carbon black
coke/^
HOCs from water at 20ฐC, N2 from gas phase at -196ฐC
Capacity of Adsorption Environments for
Contaminants Must Be Measured
Relationship between water and soil
concentrations is typically nonlinear
The Freundlich equation is often used to model
data
r - K c nf
'-sorbed ^F '-water
6
-The Langmuir isotherm
equation is also used
Csorb/Csorb.max = KadsCwater / (1 + Kads Cwater)
Both Partitioning and Adsorption
Environments are Often Present in Solids
Two-part
models used to
capture
sorption to s
both
environments
simultaneously
Allen-King etal., AWR, 2002
C-7
-------
The Contribution of Partitioning and
Adsorption Environments Varies Widely
Depending on the Sorbent
I E-(M I B-rtJ I E-rtl
OS
I EOZ 1 E01 J.E*00
OS
(left) Pyrene sorption to the silty/clayey aquitard
material and (right) 1,4-dichlorobenzene
sorption to subbituminous coal
Allen-King etal.,AWR, 2002
Mass Transfer from Adsorption
Environments is Thought to Be Diffusion
Controlled
Contaminants diffuse through:
tortuous matrices of inflexible organic matter
- pores in minerals and between cemented mineral
fragments
In some cases a retarded diffusion concept
has been invoked
- E.g., Diffusion through internal pores of particle
that is retarded by sorption to pore walls
- Not a practical modeling approach
Slow Mass Transfer is Often
Approximated with a First Order Mass
Transfer Expression
Recall the single 1ฐ mass transfer expression
3p
''^snRR i /
-ks(CSORB-KFC*')
In some cases two or more first order
expressions are used in parallel to describe mass
transfer from multiple adsorption environments
ac
SORB.Part _ 1
^ ~ "
at
s.Partl^'SORB.Part
a
SORB.Adsorb _
at
_ _],
'H
Poorly Sorbing Solid Phases Are Also
Present in Samples Analyzed for Leaching
Cements used to encapsulate solid waste
materials like contaminated soils
Oxidized potassium permanganate that
precipitates around soil and NAPL phases and
creates a diffusion barrier
Composites of these materials that also
contain adsorbents
E.g., activated carbon embedded in cements
C-8
-------
Precipitates Create Serial Barriers to
Leaching
Reduces permeability so increases diffusion
length scale in stagnant water
Create a solid barrier that only allows
contaminant release through hindered
diffusion
- If precipitates contain adsorbents, then have
retarded diffusion
Contribution of Contaminants Originally
in Trapped NAPL to Leachate Can Be Large
Can be a pure NAPL, or a NAPL mixture
Mass transfer is typically described by first order
process
seN
PN ^Lai^soL ~^a) Pure NAPL
p ^1 k . (x C C ) NAPL mixture, Xj=mole fraction
Mass transfer from NAPL is relatively fast compared to
adsorption environments
Can be limiting if diffusion length scales through low
permeability zones are large and at high water velocities
Recall the Different Phases That
Contribute to Leaching
Mass Transfer Processes Can
Be in Parallel or in Series
A -> B -> Water Phase (Series)
C -> D -> Water Phase (Series)
E -> F -> Water Phase (Seri
11 Water Phase
riesT- (Parallel)
-(Parallel)
C-9
-------
^v"
Many Models Have Been Developed to
Describe These Mass Transfer Processes
Recall the simple leaching model with mass
transfer in parallel that I
-------
Issues with Organic Transport in
Physical Models of Barrier Systems
Craig H. Benson, PhD, PE, NAE
School of Engineering and Applied Science
University of Virginia
chbenson@virginia.edu
Modern Waste Containment Sysl
2. 3.
Leachate Collection: / Cover:
- remove mass 7 - limit infiltration
- limit hoad / NT -control gas
Y X-separate
7777 ^N, //
1 \N^ S/
___ฃ '
Liner: leaking
limit contaminant \ /contaminant
discharge \ /
t n
Groundwater
:ems
Drinking
Water
J Supply
////
Highly engineered systems that are protective of the environment
Single
Leachate
Collection System
Compacted
Clay Liner
Subgrade
G
Composite Liner Systems
Synthetic geomembrane
and natural clay-based
layer work synergistically
Geomembrane (GM) gnd hgve very |QW
leakage rates.
Leachate
Collection System Exceptionally strong track
-L Very long lifetimes
expected, 1000+ yr
C-ll
-------
Double Composite Liner Systems
^.Geomembrane (GM)
I-GCL
Double systems
with leak detection
essentially
eliminates release
Compacted
Clay Liner
Subgrade
_Geocomposite
Drainage Layer
^Geomembrane (GM) Of Constituents.
Found to be
extremely effective
worldwide, but
conservatism may
not be necessary.
Liner Leakage
1000
EPA Field Database
GM-Clay
&GM-GCL
10 10 10 10 10
Hydraulic Conductivity of the Clay Liner (cm/s)
Advective-Diffusive Transport
through Holes
Geomembrane
I I
I I I
I;; Organic ;;
;;;; Diffusion I
ill Org; ;;;;;;
!!! Diffusion!!!!!!
!!!! Subgrade or!
Clay Liner ;
Inorganic or Organic
Advection
Requires 3-D numerical transport
analysis
Diffusive Transport through
Intact Geomembrane
Subgrade or
day liner
Requires 1-D numerical transport
analysis
VOCs in Lysimeters Beneath Liners in Wisconsin
1000
,100
o
10
c
<0
o
ง 1
o
0.1
Dichloromethane
-MCL
PAL
MCL = Maximum Contaminant Level
PAL = Protective Action Limit
345
Time (yrs)
C-12
-------
Leachate & Lysimeter Concentrations
Composite Liner VOC Transport Experiments
Reservoir spiked
with sodium azide
to eliminate
microbial activity
leading to losses
Sampling volume
selected to have
negligible impact on
transport
VOC Concentrations in Clay Liner
with Model Predictions
200 250
'ime (days)
Dual Compartment Tests for Diffusion (DJ &
D
Partition (KJ Coefficients for Geomembrane
D
C-13
-------
Kinetic Batch Tests for Diffusion (Dg) &
Partition (Kg) Coefficients for Geomembrane
2 0.6
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0
Time (day)
Model fits
provides Dg & Kg.
Acceptable if
geomembrane is
homogeneous
material.
Partition (Kg) Coefficients for Geomembrane:
Double Compartment vs. Kinetic Batch
140
120
100
80
60
40
20
0
(a):
20 40 60 80 100 120 140
Bias from double
compartment
due to loss in
flange.
Eliminating loss
results in good
agreement.
Co-Extruded EVOH Geomembrane
Ethyl vinyl alcohol (EVOH) core
PE jacket (LLDPE or HOPE)
Tie sheet to bind EVOH and HOPE
1.0-mm EVOH
Columns for EVOH Composite Liner Tests
C-14
-------
New Flange Design
Geomembrane
Well Mixed Upper Boundary
, Sampling port
Upper reservoir
Stainless steel
' beads
Column Tests for EVOH Composite Liner Experiments
TCE Concentrations in Clay
Component of EVOH Composite Liner
10
6
O 20 mm-sampling depth
[] 40 mm-sampling depth
^ 80 mm-sampling depth
-*...ซ.
Repeatable.
Good agreement
with theory (not
shown).
0 50 100 150 200 250 300 350 400
Time (d)
C-15
-------
Reactive Barrier Strategy for Creosote
For creosote
containment:
-Impermeable to
DNAPL
-Permeable to
ground water
- Remove PAHs
dissolved in ground
water flowing thru
barrier.
Create a Variably Permeable Reactive Barrier - VPRB
What are Organoclays?
- Na bentonite (high
montmorillonite content)
exchanged with quaternary
ammonium cations
- Cation characteristic binds
molecule to clay surface.
Organic component provides
sorption site for PAHs
- Benzyltriethylammonium or
hexadecyltrimethyl-
ammonium
Creosote Remediation - Michigan's Upper Peninsula
m Mg^^^m
UP is a major source
of iron ore.
Load iron ore onto
ships for transfer to
Chicago rail
terminals.
Creosote used for
railroad tie treating
for iron ore lines.
Site Aerial View- Iron Ore Loading Facility
Upper Peninsula, Michigan
JgS Railroad tie-
treating facility
where ties
soaked in
creosote (wood
preservative).
Creosote
residue from
pits migrated
thru subsurface
& ultimately to
lake.
C-16
-------
r -^
Proposed Barrier
Location
Full-Scale Barrier
Cover broad area to
ensure all stringers
are captured.
Key into underlying
clayaquitard.
Polish effluent into
Lake Michigan using
subaqueous cap
(organoclay coremat)
Cross-Section Parallel to Flow
Source
f ~ -
Trial
barrier
Lake
Michigan
Creosote discharging into lake creating "hot spots"
Ground water with dissolved PAH emanating into Lake Michigan
Cross-Section Perpendicular to Flow
(looking upstream)
!"
i--
C-17
-------
Hydraulic Conductivity Record
10-'
10-'
Ho-e
10-1
n
NAPL
r
;
k>W
rvj
i i i i i i i i i
i i i i i
Water -
-
ป*
iii
0 20 40 60 80
Elapsed Time (d)
Material
PM-199
ET-1
EC- 199
0% PM-199
10% PM-199
25% PM-199
50% PM-199
Hydraulic
Conductivity (cm/s)
7.6X10'10 (for DNAPL)
9.6xlO-10 (for water)
3.4xlO'9
3.7X10'10 (for DNAPL)
l.lxlO'9 (for water)
4.1xlO-5
2.6xlO'6
S.SxlO'9
2.8xlO'9
- Nearly /mpermeable to
DNAPL, but varies by clay.
- Can obtain similar low K
with a sand blend.
PM-199
ET-1
Aqueous-Phase Column Experiments
Objective:
Pump
Columns Effluent
- Evaluate organoclay
under flow-through
conditions
-Determine if
parameters from
batch tests provide
reasonable
predictions of
sorption underflow
through conditions.
Breakthrough from Batch Adsorption Data
(time to breakthrough at MCL)
Thickness
of Barrier
(m)
0.5m
1.0m
Material
PM-199
ET-1
EC-199
25% PM-199
50% PM-199
PM-199
ET-1
EC-199
25% PM-199
50% PM-199
PVF to MCL in
Column Test
1843
148
920
461
922
1843
148
920
461
922
Longevity (yr)
at 1 m/yr
307
24
154
77
154
614
49
307
154
307
C-18
-------
Effluent from Organoclay Columns
Naphthalene
1 (logKow=3.30)
:
Glass Beads
PM199
ET-1
EC-199
- Field Highest Cone.
Acenaphthene
_ (logKow=3.92)
4.0 -
2.0 J-"
o.o kit
(b) -
0 40 80 120 160 200 240 280 320
120 160 200 240 280 320
- Breakthrough of naphthalene (above DL) in ET-1
organoclay (lowest OC fraction) ~ 190 PVF
- No other breakthrough in 10 months.
Summary Remarks
Experimental apparatus can have a significant
effect on outcome of transport experiments with
hydrophobic organic contaminants at low
concentrations.
Evaluate materials beforehand as sinks for
organic contaminants, even in the most obscure
components. Avoid false negative.
Evaluate apparatus for unintended sinks for
organic contaminants.
Develop expectations for outcomes of
experiments to provide reality check on data.
Acknowledgements
US Department of Energy, Environmental
Management, Consortium for Risk Evaluation
with Stakeholder Participation (CRESP)
US National Science Foundation
Wisconsin Department of Natural Resources
Kuraray America Inc.
CETCO
Union Pacific Railroad Corporation
C-19
-------
Estimation of Source
Term Concentration for
Organics Contained on
Superfund Sites
Ed Barth, PhD, PE, CIH, RS, BCEE
Office of Research and Development
Cincinnati, OH
Purpose of Presentation
1 Briefly describe and present examples to illustrate how EPA Regional
Offices (Superfund Program) and EPA Office of Research and
Development (ORD) have historically and currently evaluated "the
source term at the unit boundary" for remedies involving on-site
containment of organic materials (including DNAPLs)
Various Types of DNAPL Sites
Petroleum
Wood Preserving (Creosote, PCP)
MGP
Organic Compound Formulation Industries
Waste Recycling Industries
Remediation options for DNAPL contaminated
soil and sediments
Containment (cap, slurry wall)
Product Extraction and Recovery
In-situ solidification/stabilization (ISS)
ISS w additives (carbon or organoclays)
Complete or partial degradation via in-situ heating, in-situ
combustion, in-situ chemical treatment (oxidation, de-chlorination),
or in-situ bioremediation
C-20
-------
Pre-placement Evaluation Methods
Oily Extraction Procedure
Paint Filter Test
EPToxicity
MEP
TCLP
SPLP
ANSI 16.1 with/without site ground water
Column leach testing methods (SWLP, sediment cores)
ORD Center Hill Lab. studies involving Shrinking Core Model, Constant pH leach
note; Various Conferences and Symposiums (such as HMCRI, ASTM} have suggested
other methods which have not transferred to the Superfund Program
Post-placement Evaluation Methods
Coring: leaching and microscopy (LSD, EPA SITE program)
Water quality monitoring of terapods placed in surface water (SUNY)
SPME analysis of sediment pore-water
Ground water monitoring (Superfund Five-year review requirement)
Other Organizations with ISS Guidance
ITRC Guidance: Pert. Specs. 2011
Strong emphases on physical
properties such as:
UCS
hydraulic conductivity
EPA TCLP and LEAF Methods
Environmental Canada. 1988
Freeze/thaw cycling
Wet/dry cycling
Microscopy
Various leach methods
Alternative Evaluation Methods: Bonding Strength
Indicator Techniques (Soundararajan, Barth,
Gibbons. 1990)
Organic Solvent Extraction (methylene chloride or hexane)
FTIR
DSC
XRD
note: this qualitative prediction approach was consistent with
polymeric encapsulation processes quantitative prediction approaches
using Arrhenius modeling of a failed physical parameter during
accelerated weathering tests
C-21
-------
Further Bonding Strength IndicatorTechniques
(Johnston, Barth, Chattopadhyay. 2012)
Containment/Challenge of containing a DNAPL soup (Mukherji, et al.
1997)
Sequential extraction test (similar to Tessier series except last stage)
Consideration of facilitated transport (via low vs. high colloid
competion environment)
note: In a separate study, pore water extraction via centrifuge
(sediments) appears to be another predictive tool
Structural, Spectroscopic, and Sorption Studies of
Alkylammonium Modified Clay Minerals r~
Structural Methods
Powder X-ray diffract!
Target d-spacing of ~ 3.8 nm corresponding to
intercalation fo 2 layers of DMDODA in clay interlayer
Thermal analysis:
s- TGAto confirm surface loading of DMDODA in clay
interlayer. Target surface loading: 44%OM;35%OC
Assess thermal stability of clay and influence of
organic cation on dehydroxylation
Spectroscopic
FTIR Spectroscopy
sS * Gain molecular insight about the interaction of the
organic cation with the clay mineral.
Molecular probe of alkyl chain ordering. Measure of
organophilicity of organoclay
Lessons Learned: "Normalize" for Mass Balance
Concerning PAHs analytical techniques?
Reduction of PAHs in lab samples due to photochemical oxidation
exposure (Kochaney and Maguire. 1994)
Headspace volatilization
Dilution
Sorption onto glassware
Oil sheens on sample surface
Some Current Approaches Used by USEPA
Regions (proposed by EPA contractors)
LEAF methods
Site ground water
Coated Glassware
Partitioning/NAPL saturation
Pore water models based upon partitioning
C-22
-------
Case Study: Atlantic Wood Industry, VA: Use of OC
for in-situ application at Atlantic Wood Site
Atlantic Wood Industry Site
Region 3 contacted ORD because TCLP criteria for PCP (0.001 mg/l)
could not be met with cement based process
Based upon previous ORD work with Dr. Stephen Boyd of MSU, ORD
suggested the use of OC
Addition of organoclay greatly reduced the TCLP value of PCP, but not
below criteria established for the site
Case Study: Gowanus Canal, NY: ISS of NAPL
Contaminated Sediments
Gowanus Canal Treatability Study (Niemet, et
al. 2015 and Gentry etal., 2015)
SPLP
EPA Method 131BM: modified for organics: methanol extraction,
PDMS lined leaching vessel
Dean-Stark fluid pore saturation to indicate NAPL mobility
C-23
-------
Summary Points
Some EPA Regional Offices have used leaching methods, beyond the
TCLP, to ascertain whether a treatment/containment process is
adequate
An array of challenge fluids are available to cover the range of
extraction recovery
While bonding strength indicator methods are available, they are rarely
used in treatment evaluations
C-24
-------
European and international standards on leaching of
organic contaminants, available tools and recent
developments for assessment of organic
contaminants
Hans van der Sloot1, David Kosson2, and Andre van Zomeren3
1 Hans van der Sloot Consultancy, Langedijk, The Netherlands
2 Vanderbilt University, Nashville, TN
3 Energy Research Centre of the Netherlands, Petten, The Netherlands
USEPA Workshop on the Measurement of Leaching of Semi- and Non-Volatile Organic
Compounds September 16, 2015, Washington
VANDERBILT
SCHOOL OF ENGINEERING
tvfu^&r-Steei- I-,. /
naultancy |VJ>3'~
ECN
Outline
Uses of leaching tests for organics in European context
(e.g., products, construction materials, remediation, waste
management, beneficial use)
Where are organics considered? Which types of organics?
Standardised test methods (including current status of each
with respect to standardization and adoption)
Available leaching data for organic contaminants
Sustainable landfill scenario (inorganic and organic
substances)
Consultancy
VANDERBILT
-^ -^v^
^a^- - 2
Standards for org;
European standardised leaching methods f
waste, soil and construction products (CEN/TC2S
International standard methods for organic
(ISO/TC190)
Validated National standards: NEN - Nethe
Non-standardised methods: Netherlands - s
Recent developments: Ecotox testing for con<
biocides)
Summary of noted differences between inorgani
leaching
Limitations
Hw*~.ti,SHet I /
Consultancy l\_>y~
"IT VANDERBILT
anics
or organic contaminants from
2, CEN/TC345, CEN/TC351)
contaminants from soil
lands, DIN - Germany
ediments; Denmark- waste
truction products (emphasis on
: and organic contaminant
^ECN
MMMWOHPHIM
Leaching standards by matrix, test type, inorganic (all) and
organic substances (yellow)
Matrix
pH dependence test
Percolation test
Monolith test
Compacted granular test
Redox capacity
Acid rock drainage
Reactive surfaces
Soil, sediments,
compost and
sludge
ISO/TS2126
8-4
EPA 1313 *
ISO/TS2126
8-3
NEN7374(2004)
DIN19528
EPA 1315 *
EPA 1315
ISO/CD127
parts 1-5
12
Waste
PrEN 14429
PrEN 14497
EPA 1313
PrEN14405
NEN7373
NEN7374(2004)
DIN19528
PrEN15863
NEN7375
EPA 1315
NVN 7376 (2004)
NEN7347
EPA 1315
CEN/TS 16660
Agreement
Mining w
ste
PrEN 1442 9
PrEN 14497
EPA 1313
PrEN 14405
EPA 1315
EPA 1315
EN15875
Construction products
PrEN14429s
EPA 1313
FprCENTS 16637-3
NEN7373
NEN7374(2004)
DIN19528
FprCENTS 16637-2
NEN7375
EPA 1315
NVN7376 (2004)
FprCENTS 16637-2
EPA 1315
* EPA methods included in SW846 E based on NEN 7348 * Not yet adopted in CEN/TC 351 (very relevant for CPR)
H^ซi~^5Uw- 1 ^/
Con.iult.incy [\_.>y~
"*T VANDERBILT
^ECN
C-25
-------
.
Standardized leaching tests for organics - column test*
Origin:
Field of
Part
cle size
Hydraulic
conductivity of
he column
Substances
Lea chant:
Diameter and
height of
material
Amount of solid
Solic
Pre-
, poking
quilibration
L/S (I/kg) per
Max
a ecu
US:
mum
mulated
CENTC351 WG1
Construction products
HS'H^rL
!^d non-volatile organic
DMW
0 5 - 1 0 cm and height 30 cm glass
O.E 2.4 liter
- .
.-.hours
10
Up
ISO TC 1 90 SC7 WGE Dutch national standard NEN German national standard DIN
-.,il like matenals (e.g. Waste, soil and construction Waste and construction products
thB
J'm"' S5
..d non voiatne organic ^B
sand
OCR, EOX, phenols to^cJOTJ non volatile organic
DMW * 0.001 M CaCI2 DMW
>'
0.5
rjz: "PshZpmo"FE, sปป<ซ
2.4 liter 0.4 kg d.w
damping inca. 5 cm layers Lighttamp
::::::::. ssiFซ-r
nซ in a,. 5 cm l.y.r, L,ซhl ttmping in ra. 5 cm l.yซซ
"lฃaDa iF-si=; 5=s
10 10 2 (optional 10)
* Observations from EU standardisation activities
Hซs-ปป~i*^5iwnl- 1* /
"^T VANDERBILT
^ECN
^^^^ ^ MMBHlKHfe^'
Standardized leaching tests for organics - column test*
Test name
Tubing
Number of steps
Total test time
Temperature
Flow rate (mL/hr)
Residence time
Collection
vessels and
Liquid/solid
(inorganic vs.
Organ c)
Test status
C :
FprCENTS16637-3
US=10
20 ฑ5
24.5 ml/hr
ss;i^ฐ:sF,oEss,,7-3
...
IOC " !. ,. .,,-iar 1000- 3000 g
Cumulative mg/kg vs US
" "
ซ-.ซซ.
ISO/TS2126B-3 NEN737
DIN19528
organics)
7 , 4(opt,onalปo,mo,,)
"""" Sm" "-.I"'" '<ปyf<ปUS.2and4daป,to,US.,o
20ฑ5 20ฑ2'G 20ฑ2ฐC
cLho"5cmmcoTum7dBmSnl:4ii """"""' 54 ml/htur
5 hour.
SITS
Op icnal : 2000 - 3000 g with O^K\ . :, pfl.-j.r.rj
Op icnal filtration for only inorganics SSS RC55) 100 FNU. Options! : 2000 - 3000 g
with cooling
Cumulative mg/kg vs US Cumulat ve mg/kg vs US Cumulative mg/kg vs US
2004
ssEliI-2';, ;.:;'-:;; -JSR
* Observations from EU standardisation activities
HuvM-firSM- 1 - / "Vf VANDERBILT
^ECN
^^^^^w <*
-------
"^^^^"^ ^*"=-' -^_
/T ^Sf.^11 * ^: ^^^^^
Performance data for leaching of organic contaminants
NEN 7374 (2004)
Within lab variability Sr
Between lab variability SR
DIN 19528 (2009)
Within lab variability Sr
Between lab variability SR
DIN 19528 (2009)
Within lab variability Sr
Between lab variability SR
Huvซ~lltrSM- 1 . /
PAH PCB
25 % 15 %
42 %
EOX Phenols, cresols
12 % 3 %
42 % 14 %
IPAH Naphtalene Anthracene
13 % 10 % 12 %
50 % 45 % 45 %
Pyrene Chrysene Benzo[a]pyrene
10 % 27 % 60 %
45 % 48 % 80 %
"^" VANDERBILT
^ECN
Main features of leaching standards for organics*
CEN and ISO Standards are suitable for inorganic and organic substances.
The first and foremost reason is that the basis of testing and the use of test results in
environmental judgment of release is not fundamentally different.
In many cases information on both inorganic and organic substances is needed.
Running one test has economic advantages (equipment occupation, cost).
Ecotox testing requires eluates containing all substances of interest.
Material requirements for the equipment and other parts getting in contact with the
eluate are adapted to meet requirements for both type of substances. Glass column
and stainless steel connections.
( In the column, quartz sand or glass beads are used instead of filters.
Filtration commonly used for inorganic substances is unsuitable for organic
substances. If needed, centrifugation is prescribed.
Test limited to non-volatile organic substances at ambient conditions.
* Observations from EU standardisaton activities
g^^j-^ -y VANDERBILT ^ECN
^^^^s*. <**""=r~ _
,' *s^>- .2
Non-standardized tests for organics
Static method for porewater analysis (Solid Phase Micro Extraction (SPME),
Semipermeable Membrane Devices (SPMD), Solid Phase Extraction Disks (SPE
disks) and Tenax extraction. Applied in the Netherlands for bioavailability of
organic contaminants in sediments and soils.
Limitation: useful method, but does not provide insight in long term behaviour
Leaching tests for non-volatile organic compounds. Recirculation column
procedure derived from the CEN/TC292 procedure.
Inconsistent batch test results prompted this development. Test was developed as a
compliance test procedure. However, results are not easy to interpret.
Modified diffusion test procedure (Nordtest report TR577)
Same basic test method as defined in CEN/TC292, CEN/TC351 and EPA 1315, but
modified with a strong sorbing solid or liquid phase to create a zero boundary
condition.
rt-cw-^s-f |_ / "IT VANDERBILT ^ECN
Con.ull.ncv I\_V- V SCHOOL OF .NC,ปEปC , \J,
Available data on leaching of organics
Dutch, German, Danish and Swedish leaching data
pH dependence 14 samples
Percolation 108 samples
Monolith leaching 82 samples
Ecotox testing in connection with leach testing (Study
Umwelt Bundes Amt, Germany)
Modelling for partitioning of organic contaminants
between free, DOC and POM associated forms - Role of
DOC and POM for organic contaminant mobility.
H^^^SWf |_ / fT VANDERBILT ^ECN
Con.ull.ncv FOc*- V SCHOOL OF INCIKH.WC . \?
C-27
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Liquid-Solid partitioning and Organic Contaminants
Organic Contaminants (PAHs) 12
Solubility is not directly affected by 1'ฐ
pH | ,
Low aqueous solubility s <
Partitioning with organic phases *
Complexation with DOC
Complexation with DOC 12
Leads to high measured 3 iป
concentrations 1 ป
Quantified by KDOC ง '
DOC removal by flocculation with " ,
AI2(SO4)3atpH6.0
I~*~PAHSI
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Consultancy |\_>^~
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VANDERBILT
pH Dependent leaching of PAH and DOC for a composite sample of
Predominantly Inorganic Waste from a lysimeter
PH
Anthracene
* Benz[a]anthracene
-*-Benzo[k]fluoranthene, BKF
-a-Chrysene,CHR
ฉDissolved Organic Carbon
-JK-Mineraloil
--Sum of 16 EPA PAH
0 Phenanthrene
Apparent correlation of PAH with
DOC, hence indirect pH
dependence of PAH leaching
Consultancy
VANDERBILT
Comparison of PAH and mineral oil leaching based on laboratory,
lysimeter and field data for landfill
':-f\:i
M. fi '
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/
Comparison of PAH leaching from a wide range of
waste, soil, sediment and construction materials
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VANDERBILT
asphalt, gasworks soil,
contaminated soil, sifter
sand from demolition,
industrial fly ash
coal fly ash, MSWI bottom
ash, predominantly
inorganic waste (landfill),
river sediment, masonry
aggregate, concrete
aggregate, reclaimed
asphalt, porous asphalt
ECN
C-28
-------
~ Monolith leaching of PAH and biocides from railroad tie, stabilised
waste with organics, roofing felt and treated wood
Results from ED Leaching Test Development for Organics (1)
Adsorption to Material Surfaces
Match contacting surfaces to organic substances of interest
x Plastics (including Viton), rubber, PTFE (PAHs adsorb to Teflon)
/ Glass, stainless steel
Volatilization
Not considered as only semi- and non-volatile organic substances are
considered.
Colloid Formation
More colloid formation in a batch test vs column testing
Centrifuge eluate rather than filtration, if at all needed
Eluate Analysis
Always measure pH and DOC. DOC varies as a function of pH and hence
water insoluble organics associated with DOC have increased leachability
as pH increases.
Consultancy
VANDERBILT
Consultancy
VANDERBILT
Ss^* -*, , >
Results from ED Leaching Test Development for Organics (2)
Demonstrated higher release from batch vs column
In the context of the development of the ISO standards for Soil a
comparison was made between batch and column leaching. In
almost all cases the batch test gave higher release values.
Explanation higher turbidity and thus higher DOC level in batch vs.
column.
Filtration and/or centrifugation
In the German test filtration and centrifugation are not used when
the turbidity of the solution is below a certain value (FNU). In their
experience, this is the case for almost all construction products
and many soils.
H.^.iirfji f 1 / "*T VANDFRBTW, ^^ECN
consultancy! [ ^f SCHOOL OF ENGINEERING
Key Concepts
Liquid-Solid Partitioning
Liquid-Solid Ratio
Redox- not directly relevant
Dissolution/Sorption
Particulate and dissolved organic matter interaction
Eluate Chemistry
Mass Transport
Diffusivity
Surface Area
Surface Interactions (local equilibrium)
Limitations
Degradation of organic substances
Degradation of organic matter and associated DOC formation
Sorption on many surfaces
Volatilization
H^^i^SWf |_/ "IT VANDERBILT ^ECN
consultancy nO** W SCHOOL OF ENGINEERING
C-29
-------
Ecotox testing in connection with leach testing
(Study Umwelt Bundes Amt, Germany)
In CEN/TC292 Waste characterisation a leaching test for
ecotox testing was developed.
The validation was done in a project led by DBA (Umwelt
Bundes Amt, Berlin)
Leaching was carried out by a single step leach test and
by full characterisation using percolation test PrEN14405
and pH dependence test EN 14429
Partitioning between dissolved and solid phases was
carried out for dilutions made as part of the ecotox testing
protocols
H.uvl->aซ
-------
i *"
Sustai
Inorgani
Explanation of
approach
Example
results
Its uses
The Dutch Ministry of
Environment and
Infrastructure
regulates aftercare of
landfills
Hiซj. ^iซ. .C/- \f SCHOOL OF tNcmFER.Mt: , \!
C-31
-------
Evaluation results (concentration as a function of time in the
soil solution at 1-2 m depth) Sustainable Landfill Scenario
[taunt*] Muni
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;
V
ft xn *ป MG BOO two ',,*'
Observations (1)
Validated test methods for organic substances available at national level.
Validation of tests suitable for organic substances in construction
products up for validation in 2017, when the robustness work that will
start in early 2016 is finished (CEN/TC351).
Standardised tests show systematic release patterns for organic
contaminants allowing understanding of release mechanisms
Methods have been aimed to deal with inorganic and organic substances
simultaneously to facilitate ecotox testing of eluates
t*~rvป~t(*r5iปt l_- /
:onปi/ltjncv I'Qcr-
VANDERBILT
Consultancy
VANDERBILT
*S^* **, , &
Observations (2)
The role of dissolved organic matter is important in release of semi- and
non-volatile organic substances due to their association with DOC
The transport properties are not controlled only by the substance itself,
but also by the transport properties of DOC
The pH dependence of DOC release is important because of the
association of organics with DOC impacts organics partitioning and
transport
Release of organic substances from monolithic products (stabilised
waste and treated wood) is to a large extent controlled by release of
DOC bound organic substances and thus controlled by DOC release.
DOC release from porous monolithic materials is about a factor 10 - 15
slower than soluble salts (e.g. Na+, K+, Cl~)
rt-cw-^s-f |_ / "IT VANDERBILT ^ECN
Con.ull.ncv rOcA V SCHOOL OF .NC,ปEปC , \J,
Observations (3)
DOC associated organic substances are not bioavailable for a range of
organisms and thus have no toxic response (example: gaswork soil UBA
study)
Partitioning of dissolved organic matter in subfractions (fulvic and humic
substances) may prove important in view of their different binding
characteristics for organic contaminants
The use of Koc parameters allows the partitioning of organic
contaminants to be estimated between particulate and dissolved organic
matter
Sustainable landfill scenario considers leaching test results in conjunction
with transport, dilution and attenuation to determine leaching test
thresholds for regulation.
H^^^SWf |_ / "IT VANDERBILT ^ECN
Con.ull.ncv FOc*- V SCHOOL OF INCIKH.WC . \?
C-32
-------
__. - _
References
Standards published by CEN (European standards organisation), ISO
(International Standards organisation), Dutch Standards Organisation
(NEN) en German Standards Organisation (DIN)
Ecotoxicological characterization of waste - Results and experiences
from a European ring test. Eds: J. Rombke, R. Becker & H. Moser,
Springer Science+Business Media, Inc. Norwell (MA). Chapter: Postma
J.F., van der Sloot, H.A. and van Zomeren A. (2009): Ecotoxicological
response of three waste samples in relation to chemical speciation
modelling of leachates.
E. Brand et al. (2014) Development of emission testing values to assess
sustainable landfill management on pilot landfills Phase 2: Proposals for
testing values, RIVM report 607710002/2014
Con.ult.ncy
"IT VANDERBILT ^ F(~N
V SCHOOL OF EUGINEIRIHG ฎ* C V. IN
C-33
-------
LEAF Leach Testing for Inorganic
Contaminants: What Led to it's
Development?
Gregory Helms, ORCR
September 15, 2015
What Led to LEAF Development?
TCLP is EPA's regulatory test and most used leaching test.
Developed to implement the national RCRA regulatory program
(not tailored to be site-specific).
Based on RCRA def of hazardous waste ("may pose hazard
when improperly managed").
Simulates plausible mis-management scenario for waste
disposal (i.e., co-disposal with municipal solid waste).
Because it is the regulatory test, TCLP is used even when not
required by regulation:
EPA SAB has twice (1991 ,1999) expressed concern about over-broad
use of TCLP.
Conditions at most contaminated sites do not resemble MSW/TCLP
conditions.
I Office of Solid',
What Led to LEAF Development?
ORCR experienced several program problems
related to use of TCLP in the late 1990s:
The LDR treatment standard and hazardous waste delisting for K088
based on TCLP data resulted in environmental releases:
- Arsenic was leaching from the K088 disposal monofill at levels
more than 10Ox the TCLP results (monofill leachate pH 13)
- EPA withdrew the delisting and instituted disposal restrictions for
delisted waste.
EPA was successfully sued on use of TCPLdatato establish the LDR
standard by an aluminum company.
- The court said that models of the environment must bear a
reasonable relationship to the situation they are intended to
represent.
and Recovery. Waste Character?
v>EPA
What Led to LEAF Development?
TCLP Program Issues (cont):
In responding to legal challenges to TCLP use in determining the
hazardousness of mineral processing wastes, the Agency was urged to
consider using SPLP instead.
TCLP was used in the end, but EPA agreed to conduct a review of
leaching tests and their use in Agency Waste management programs
and Recovery. Waste Character,?
C-34
-------
Superfund Use of Leach Tests for S/S
Projects
Urtll U 7>pcr>ffcH Cure ToflngUwd tor i
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30
v
I Offios of Solid Waste and Em.
2x What Led to LEAF Development?
EPA's Science Advisory Board (SAB) has in the past
expressed concern about the Agency's use of
Leaching Tests:
- In a 1991 report, the SAB expressed concern about the over-broad
use of the test, particularly where test conditions did not match site
conditions.
-SAB expressed concern about several technical aspects of TCLP
(e.g., colloid formation)
-SAB urged the Agency to develop test methods which would:
Consider the significant parameters affecting leaching.
Consider conditions of the disposal site.
Be supported by field validation and repeatability studies.
Be supplemented by leaching and source term modeling.
- In 1999 the SAB reiterated many of the concerns expressed in the
1991 report.
I Offios of Solid Waste and Em.
xS-EPA
What Led to LEAF Development?
EPA initiated a program to identify and validate a next-
generation of leach testing approaches
-Goals in selection of appropriate tests included:
1. General applicability to a broad range of
wastes/secondary materials
2. Consideration of conditions that affect leaching
3. Flexibility to allow tailoring for a range of applications
and Recovery, Waste Characteriz
v>EPA
What Led to LEAF Development?
2003 SAB Consultation
When LEAF research on CCR leaching was begun, ORCR/ORD
consulted with the SAB about the approach being taken.
-SAB was in particular asked its advice about the relative
importance of the parameters affecting leaching that are
incorporated into LEAF.
-SAB did not disagree, but noted that other factors are
sometimes important and urged flexibility in testing.
-SAB also urged the Agency to develop leaching tests that
included leaching or organic constituents.
and Recovery, Waste Characteriz
C-35
-------
SEfi^ LEAF Addresses Many SAB Concerns
*
Most tests (including TCLP & SPLP) assess leaching
potential for a single set of conditions:
Tests tend to focus in initial conditions; final test leaching
conditions are often unknown.
However, final test conditions represent conditions under which
leaching actually occurs
Site conditions can have a significant impact on
leaching:
Metal solubility and aqueous-solid partitioning vary with pH.
Infiltration rates vary nationally (varying weather, soil type)
Redox conditions can determine which metal salts are present
(and so change solubility).
Site conditions can change overtime.
I Offios of Solid Waste and Em.
Program Use of LEAF
Intended for situations where a tailored assessment is
needed, and the conditions differ from TCLP, and TCLP is
not required by RCRA regulations
- Evaluating treatment effectiveness for corrective action/site remediation
where LDR treatment standards are not triggered
- Hazardous waste delisting
- Assessment of non-hazardous materials for beneficial reuse
-Characterizing potential release from high-volume materials
CAMU regulations can allow use of alternatives to TCLP for assessing
stabilization treatment effectiveness if the alternative more accurately
reflects conditions at the site that affect leaching. See: 40 CFR
264.552(e)(4)(iv)(F)
I Offi
-------
CMV What is LEAF for inorganics? What lead to its
development? What was the process and
timeline for developing and validating the
methods?
Susan Thorneloe, US EPA
Thorneloe.Susan@epa.gov
Presentation for USEPA Workshop for Developing Organic Leaching Test
Methods for Semi- and Non-volatile organic compounds
Office of Research and Development
National Risk Management Research Laboratory
Air Pollution Prevention and Control Division
September 16, 2015
Objective
Provide understanding of work to develop and validate:
EPA Method 1313 Liquid-Solid Partitioning as a Function of Eluate pH
using a Parallel Batch Procedure
EPA Method 1314 Liquid-Solid Partitioning as a Function of
Liquid-Solid Ratio (L/S) using an Up-flow
Percolation Column Procedure
EPA Method 1315 Mass Transfer Rates in Monolithic and
Compacted Granular Materials using a Semi-
dynamic Tank Leaching Procedure
EPA Method 1316 Liquid-Solid Partitioning as a Function of Liquid-
Solid Ratio using a Parallel Batch Procedure
Posted as "New Validated Methods" to SW-846 on Aug 2013
Range of Technologies in use for Reducing
Air Emissions at Coal-Fired Power Plants
"" Additive
Coal Additive Refined Coal Flue Gas Dry Sorbent Activated Carbon
Conditioning Injection (DSI) Injection (ACI)
Range of Coal Combustion Residues (CCR)
Management Scenarios ...
coastal protection
C-37
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Drivers for Improved
Leaching Test Methods
Existing leaching tests (i.e., simulation based) did not consider differences in
materials or environmental parameters (such as pH and liquid-solid ratio) that
influence leaching behavior
EPA received comments from EPA's Science Advisory Board, National Academy
of Sciences, NGOs and others regarding the deficiencies of existing methods
(e.g., TLCP) when not applicable or appropriate
EPA received report form the IG criticizing program that encouraged use of coal
ash without considering potential impact on human health and the environment
Changes occurring to coal fly ash and scrubber residues in response to CAA
regulations to reduce Hg and other pollutants can change the leachability of Hg
and other pollutants based on how coal combustion residues are managed by
disposal or use
Congressional request to ensure the air pollution control at coal-fired power
plants are not resulting in transferring pollutants from one medium (air) to another
(land or water resources)
SB*
Use of LEAF in Source
Term Development
Used to evaluate range of fly ashes and scrubber residues to develop material- and site-
specific source terms for land disposal of CCRs
Data led to EPA's decision to allow use of coal fly ash for substitute for portland cement for
encapsulated uses. EPA's decision was based on use of LEAF data to evaluate potential
leaching from monoliths where fly ash is used as replacement for cement.
"How to" Guidance for use of LEAF data has source term derivations for (1) coal ash used
as embankment fill; (2) contaminated soil remediation; and (3) solidified waste treatment.
Expect release in next 6 months. Will be updated as source terms are expanded to other
applications.
Continue to see broader use of LEAF by industry, academia, and commercial labs.
The EU has developed methods comparable to LEAF for source term In parallel, the EU
has developed methods comparable to LEAF for source term evaluation. China, Australia,
Israel, and the EU are adopting comparable methods.
Once CCR evaluation was completed, OSWER requested that LEAF be validated for
adoption to SW-846. Over 20 labs were involved using 4 different reference materials for
each of the 4 LEAF methods. Work began in 2010 and completed in 2013.
*-,EPA
Leaching Environmental
Assessment Framework
LEAF is a collection of ...
> Four leaching methods
> Data management tools
> Geochemical speciation and mass transfer modeling
> Quality assurance/quality control
> Integrated leaching assessment approaches
More information at http://www.vanderbilt.edu/leachinq
<>EPA Leaching Environmental
^':,"""-p'' Assessment Framework (Cont.)
Designed to identify characteristic leaching behaviors for a
wide range of materials and associated use and disposal
scenarios to generate material- and site-specific source terms
Not intended as replacement for TCLP but for use when
TCLP is not considered applicable or appropriate. Uses
include
> Assessment of materials for beneficial use
> Evaluating treatment effectiveness (equivalent treatment
determination)
> Characterizing potential release from high-volume materials
> Corrective action (remediation decisions)
C-38
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LEAF Leaching Tests*
Equilibrium-based leaching tests
-Batch tests carried out on size reduced material
-Aim to measure contaminant release related
to specific chemical conditions (pH, LS ratio)
-Method 1313 - pH dependence & titration curve
-Method 1316-LS dependence
Mass transport rate-based leaching tests
-Carried out either on monolithic material or compacted granular
material
-Aim to determine contaminant release rates by accounting for both
chemical and physical properties of the material
-Method 1315 - monolith & compacted granular options
Percolation (column) leaching tests
-May be either equilibrium or mass transfer rate
-Method 1314 - upflow column, local equilibrium (LS ratio)
^Posting to SW-846 Validated Methods completed August 2013
http://eDa.gov/wastes/hazard/testmethods/sw846/new meth.htm
LEAF Data Management Tools
Data 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
Software for LEAF data management, visualization and processing;
-Compare Leaching Test Data
Between materials for a single constituent (e.g., As in two different OCRs)
Between constituents in a single material (e.g., Ba and SO4 in cement)
To default or user-defined values indicating QA limits or health-based
threshold values)
-Export leaching data to Excel spreadsheets
Available at no cost from LEAF project website (http://www.vanderbilt.edu/leaching)
Statistical Analysis
Standard Deviations
Repeatability (within lab deviation)
Reproducibility (between lab
deviation)
95% Robust Confidence Limits
Prediction interval within which 95%
of mean Iog10 transformed data
from a lab would fall
10 12 14
Target pH
PH
Validation of LEAF Test Methods
Multi-lab Round-robin
Testing
Academic,
Commercial,
Government and
International Labs
Materials
Coal Fly Ash
Contaminated Soil
Solidified Waste
Brass Foundry Sand
EPA 600/R-12/623 EPA 600/R-12/624
C-39
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Validation Acknowledgements
Participating Labs - Domestic
Government
a Oak Ridge National Lab
a Pacific Northwest National Lab
a Savannah River National Lab
a U.S. EPA- Research Triangle
Park, NC
Academia
a Ohio State University
a University of Wisconsin -
Madison
a University of Missouri - Rolla
a Vanderbilt University
Commercial
a ARCADIS-US, Inc.
a TestAmerica Laboratories, Inc.
a URS Corporation
Other participating labs - international
DHI (Denmark)
Energy Research Centre of the
Netherlands
Support
Electric Power Research Institute
(EPRI)
Recycled Materials Research Center
(RMRC)
Tennessee Valley Authority (TVA)
LEAF Methods Focus Group
\>EPA Validation Lessons Learned
Modifications to Methods 1313 and 1316
Tolerance for contact time have been added
Requirement that pH values to be measured within 1 hr after separation
of solids and liquids due to lack of buffering in aqueous samples
Modifications to Data Templates
Mandatory information has been highlighted
Instructions more closely follow method text
Other Recommendations
Calibration of pH meters should cover entire pH range to extent possible
Reagents should be freshly prepared, stored in vessels of compatible
materials (e.g., strong alkalis not be stored in borosilicate glass)
Labs should establish a QC regimen to check the quality of reagent
water (method blanks are important)
Laboratory-to-Field Relationships
Provides understanding of leaching
assessment fundamentals
10 Cases of large-scale field analysis
coupled with laboratory testing for 7
different materials
-Coal combustion residues (fly ash,
scrubber residues
-Inorganic waste (mixed origin)
-Municipal solid waste (MSW)
-MSW incinerator bottom ash
-Cement-stabilized MSW incinerator fly ash
-Portland cement mortars and concrete
EPA 600/R-14/061
LEAF Method Validation Steps
Agreements with labs to conduct validation of individual methods
Obtain or develop samples for analysis
Prepare and deliver kits with equipment and samples for each lab and
method
Receive Excel spreadsheets with results from each lab for each
material and method
Statistical analysis of samples to evaluate inter- and intra- laboratory
variability
Documentation of results into two reports representing two batch
equilibrium methods and two mass transfer methods
Reviews and publication of EPA report
Posting of validated methods onto SW-846 web site
C-40
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Conclusions for LEAF Validation
LEAF methods for inorganics
- have been found to provide data needed for assessing release behavior under range of
field conditions for use and disposal scenarios
- 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
- were validated working with 20 different labs and posted on the SW846 website as
validated methods
Research has been coordinated with international community resulting in
leveraging expertise, data, and helping provide harmonization in leaching methods
so that comparable data is provided when evaluating use of industrial by-products
or treatment and remediation effectiveness
Field to lab report showed good comparison between lab and field data using
geochemical speciation modeling for processes not easily evaluated in lab (i.e.,
oxidation and carbonation). Able to explain leaching behavior and found LEAF is
good predicator of ultimate fate of inorganics.
Supporting Documentation for LEAF Validation
> 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.
> Background Information for the Leaching Environmental Assessment
Framework Test Methods, EPA/600/R-10/170, Dec 2010
> Interlaboratory Validation of the Leaching Environmental Assessment
Framework (LEAF) Leaching Tests for Inclusion into SW-846: Method
1313 and Method 1316, EPA 600/R-12/623, Sept 2012
> Interlaboratory Validation of the Leaching Environmental Assessment
Framework (LEAF) Leaching Tests for Inclusion into SW-846: Method
1314 and Method 1315, EPA 600/R-12/624, Sept 2012
> Laboratory-to-Field Comparisons for Leaching Evaluation using the
Leaching Environmental Assessment Framework (LEAF), EPA 600/R-
14/061, Sept 2014.
Supporting Documentation for use of LEAF to
evaluate coal combustion residues (CCRs)
> 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.
> Characterization of Coal Combustion Residues from Electric Utilities - Leaching
and Characterization Data, EPA-600/R-09/151, Dec 2009
> Characterization of Coal Combustion Residues from Electric Utilities Using Wet
Scrubbers for Multi-Pollutant Control, EPA-600/R-08/077, July 2008
> Characterization of Mercury-Enriched Coal Combustion Residues from Electric
Utilities Using Enhanced Sorbents for Mercury Control, EPA-600/R-06/008, Feb
2006
Supplementary Slides on CCR
Evaluation
C-41
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U.S. range of observed total content and leaching test results (5.4 <
pH < 12.4) for 34 fly ash samples and 20 FGD gypsum samples
TCfaglL) MCL Total
Cw/U c
(i
Hg
Sb
As
Ba
B
Cd
Cr
Mo
Se
Tl
5,000
100,000
1,000
5,000
1,000
2
6
10
2,000
7,000*
5
100
200
50
2
0.1-1.5
3-14
17-510
50-7,000
NA
0.3-1.8
66-210
6.9-77
1.1-210
0.72-13
<0.01-0.50
<0.3-11,000
0.32-18,000
50-670,000
210-270,000
<0.1-320
-------
Existing Tools and Limitations to Address Leaching
of Organic Species
David S. Kosson1
Andrew C. Garrabrants1
Hans A. van der Sloot2
1 Civil & Environmental Engineering, Vanderbilt University, Nashville, TN
2 Hans van der Sloot Consultancy, Langedijk, The Netherlands
USEPA Workshop on the Measurement of Leaching of Semi- and Non-Volatile Organic
Compounds
September 16-17 , 2015, Washington
Leaching Controlling Factors
H+
CO2
02
Chemical Factors
a Equilibrium or kinetic
control
a Liquid-solid ratio
a Potential leachability
a pH
a Complexation
a Redox
a Sorption
a Biological activity
Physical Factors
a Particle size
a Fbw rate of leachant
a Rate of mass transport
a Temperature
a Porosity
a Geometry
a Permeability
a Hydrobgical conditions
Trace elements
Soluble salts
TOC(@high pH) ^^ DOC
Simulation vs. Characterization
Simulation-based Leaching Approaches
Designed to provide representative leachate under specified conditions, simulating
a specific field scenario
Eluate concentration assumed to be leachate (source term) concentration
Simple implementation (e.g., single-batch methods like TCLP or SPLP) and
interpretation (e.g., acceptance criteria)
Limitations
a Representativeness of testing to actual disposal or use conditions?
a Results cannot be extend to scenarios that differ from simulated conditions
Characterization-based Leaching Approach
Evaluate intrinsic leaching parameters under broad range of conditions
More complex; sometimes requiring multiple leaching tests
Results can be applied to "what if analysis of disposal or use scenarios
Allows a common basis for comparison across materials and scenarios
Materials testing databases allow for initial screening
EPA Method 1310B - EP Toxicity
> Simulation Approach - Designed to mimic co-disposal in sanitary landfill, i.e.,
with municipal solid waste (assumed mismanagement scenario)
> Applicability- inorganic and organic species, volatiles not specified
> Batch, single extraction test (end-over-end mixing)
> Liquid/Solid Ratio - 20 mL/g; Particle size - <9.5 mm or 3.3 cm dia. X 7.1 cm
cylinder; 24 h contact
> Extractant - DI water + 0.5 N acetic acid added to maintain pH 5ฑ0.2 up to 4
ml 0.5 N acetic acid
Limitations
> Applicability of the scenario
> Definition of initial conditions, not necessarily end-point conditions (final pH)
> Particle size/monolith extraction time does not necessarily approach equilibrium
C-43
-------
V
EPA Method 1311 - TCLP
> Simulation Approach - Designed to mimic co-disposal in sanitary landfill,
i.e., with municipal solid waste (assumed mismanagement scenario)
> Applicability- inorganic and organic species, including volatiles
> Batch, single extraction test (end-over-end mixing)
> Liquid/Solid Ratio - 20 ml/g; Particle size - <9.5 mm; 18 h contact
> Extractants - Dilute acetic acid (pH 2.88) or buffered acetic acid (pH 4.93)
based on initial waste pH screening
Limitations
> Applicability of the scenario
> Definition of initial conditions, not end-point conditions (e.g., final pH);
treatment frequently designed to titrate test method
> Particle size/extraction time does not necessarily approach equilibrium
> PTFE is allowed apparatus material
EPA Method 1312 - SPLP
> Simulation Approach - Designed to mimic contact with synthetic
preciptation
> Applicability- inorganic and organic species, including volatiles
> Batch, single extraction test (end-over-end mixing)
> Liquid/Solid Ratio - 20 ml/g; Particle size - <9.5 mm; 18 h contact
> Extractants - Dilute 60/40 wt% H2S04/HN03to intial extraction fluid pH
4.2 or pH 5.0 (based on east or west of Mississippi River) or reagent
water (wastewater, wastes)
Limitations
> Applicability of the scenario
> Definition of initial conditions, not end-point conditions (e.g., final pH);
acidity or alkalinity of material tested overwhelms eluant acidity
> Particle size/extraction time does not necessarily approach equilibrium
EPA Method 1320 - MEP
> Simulation Approach - Designed to mimic repetitive precipitation of acid
rain on an improperly designed sanitary landfill
> Applicability- inorganic and organic species, including volatiles
> Initial EP Toxicity extraction followed by 9 serial extractions (or more)
with 60/40 wt% H2S04/HN03 to pH 3.0
> Liquid/Solid Ratio - 20 ml/g; Particle size - <9.5 mm; 18 h contact
Limitations
> Applicability of the scenario
> Definition of initial conditions, not end-point conditions (e.g., final pH);
eluant acidity often negligible compared to waste alkalinity or acidity
> Particle size/extraction time does not necessarily approach equilibrium
> PTFE is allowed apparatus material
EPA Method 1330A - Oily Wastes
> Procedural determination
> Applicability- mobile metal concentrations in oily wastes
> Batch, single extraction test (end-over-end mixing)
> 2 step soxhlet extraction with tetrahyudrofuran and then toluene on
dried solids;
> Extractants - Dilute acetic acid (pH 2.88) or buffered acetic acid (pH
4.93) based on initial waste pH screening
Limitations
> Interpretation basis??
C-44
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LEAF
leaching Environmental Assessment I:ranie\vork
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.
More information at http://www.vanderbilt.edu/leachine
LEAF Leaching Methods*
Method 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 (US) 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
'Postingto SW-846as "NewMethods"completedAugust201'3
LEAF
Framework Approach
' Test Methods designed to determine intrinsic leaching characteristics
Availability (fraction of constituent available for leaching under environmental
conditions over moderate time intervals, 100s of years)
Liquid-solid partitioning (-equilibrium) function ofpH orL/S
Elution curve approximating local equilibrium
Mass transport rate from monolithic materials (e.g., diffusion controlled)
Eluate concentrations assumed to be upper bound leachate concentrations
when consistent with leaching mechanisms and field scenario
a Solubility controlled leaching
a Percolation (uniform) with local equilibrium
Fundamental relationships and standard masstransport models used to
estimate leaching/source-term concentrations from laboratory test results
a Availability controlled leaching
a Water contact frequency and amount (e.g., field L/S or liquid/surface area)
a Preferential flow and masstransport, analytical or numerical (reactive mass
transport including chemical speciation)
a Lab-to-field verification
I
Can Approximate Leaching From Sorbed
and NAPL Phases with a First Order
Expression to Illustrate Dependence on
Capacity of Each Phase for Pollutant and
Mass Transfer Rate Constant
Dt
Dt
Dt
Available or Total
Solute in NAPL governed by mass transfer to water:
-masstransfer rate constant, kLa
-aqueous solubility, CSOL
LSP(Eq. leach test)-bulk aqueous concentration, Ca
Solute in solid governed by mass transfer to water:
N \ -masstransfer rate constant, kg
a j -sorbed phase concentration, CSORE
-bulk aqueous phase concentration, Ca
Courtesy C. Werth,U. Texas \ -isotherm parameters, KF, NF
_
4* ~pr~ ~
Mass transfer rate test
1
DC,
SORB _[
Dt
C-45
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LEAF
LEAF and EU Methods
Compactedgranulartest
Acid rock drainage
nstruction product;
FprCENTS 16637-2
Comparing pH Dependence Testing with
TCLP and SPLP -Arsenic
LEAF
Assessment Approach
Material Leaching Tests A* j
Broad-based characterization of
intrinsic leaching behavior
Material Characterization
Material Leaching in
Context of Application2
Use as Source Term
Constituent Release from
Application Scenario
DAF or Model Scenario
Constituent Cone./Release
at Point of Compliance
2 from test results or by numerical modeling
LEAF
Method 1313 Overview
Equilibrium Leaching Test
Parallel batch as function of pH
Test Specifications
9 specified target pH values plus natural conditions '
Size-reduced material
L/S= 10mL/g-dry
Dilute HNO3 or KOH
Contact time based on particle size
a 18-72 hours
Reported Data
a Equivalents of acid/base added
a Eluate pH and conductivity
a Eluate constituent concentrations
S, ,
, S2 Sn ,
S-H
i i i
Titration Curve and Liquid-solid Partitioning
(LSP) Curve as Function of Eluate pH
C-46
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LEAF
Method 1313 Rationale and Limitations
> Designed to provide Availability and Liquid-Solid Partitioning as a function of
pH. Also provides acid/base titration and basis for chemical speciation
modeling. Focus on end-state conditions (pH, L/S, DOC, etc.).
> Particle size and contact intervals, mixing to approach equilibrium.
> Conceptual paradigm is applicable for organic species.
Limitations for Use with Organics
Availabilitydeterminationapproach not applicablefororganics
pH domain beyond the relevant scenario pH not needed
Eluant and mixing conditions do not address potential for deflocculation and
colloid formation
Provisions for selection of apparatus materials, filtration, sample mass,
extraction volumes, minimizing volatilization losses are not provided
Method 1314 Overview
Equilibrium Leaching Test
Percolation through loosely-packed material
Test Specifications
" 5-cm diameterx 30-cm high glass column N;0rf
" Size-reduced material
' Dl wateror 1 mM CaCI2 (clays, organic materials)
" Upward flow to minimize channeling
" Collect leachate at cumulative L/S
a 0.2, 0.5, 1, 1.5, 2, 4.5, 5, 9.5, 10 mL/g-dry
Reported Data
a Eluate volume collected
a Eluate pH and conductivity
L E A F
Method 1314 Rationale and Limitations
> Designed to provide LSP as a function of L/S (elution curve). Approximates
initial pore water and linkages between individual species leaching (e.g.,
DOC & chloride com plexation, depletion of one species leading to increased
release of another).
> Particle size, dimensions, flow rate, to approach equilibrium. Eluant to avoid
deflocculation.
> Conceptual paradigm is applicable for organic species
Limitations for Use with Organics
Provision for in-situ solid phase extraction not provided
Provisions for selection of apparatus materials, filtration, sample mass,
extraction volumes, minimizing volatilization losses are not provided
LEAF
Method 1315 Overview
Mass-Transfer Test
" Semi-dynamictank leach test M0r
Test Specifications C
-------
LEAF
Method 1315 Rationale and Limitations
> Designed to provide maximum release flux (mass transport rate) by
maintaining dilute boundary condition.
> Closed vessels to minimizeatmosphericexchange (CO2, 02)
> Interpretation includes consideration of field scenario boundary conditions
> Conceptual paradigm is applicable for organic species
Limitations
Provision for in-situ solid phase extraction not provided (variants have been
developed but not standardized)
Provisions for selection of apparatus materials, filtration, sample mass,
extraction volumes, minimizing volatilization losses are not provided
r
ANS 16.1 - Measurement of teachability
of Solidified Wastes
> "...intended for indexing radionuclide release from solidified low-level
radioactive waste forms in a short-term (5-day) test under controlled
conditions in a well-defied leachant. It is not intended to serve as a
definition of the long-term (several hundred to thousands of years)
leaching behavior of these forms a conditions representing actual
disposal conditions."
> Monolithic sample, deionized water eluant, L/SA=10 cm, eluant refresh
at 2, 7, 24 hr; 2, 3, 4, 5,19, 47 and 90 days cumulative times.
Limitations
Not intended to be applicable to organic contaminants (inappropriate
specification of test conditions)
LEAF
Method 1316 Overview
Equilibrium Leaching Test
Parallel batch as function of L/S
Test Specifications
Five specified L/S values (ฑ0.2 mL/g-dry)
a 10, 5, 2, 1, 0.5 mL/g-dry
Size-reduced material
Dl water (material dictates pH)
Contact time based on particle size
a 18-72 hours
Reported Data
a Eluate L/S
a Eluate pH and conductivity
a Eluate constituent concentrations
Liquid-solid Partitioning (LSP) Curve as a Function
of L/S; Estimate of Pore Water Concentration
LEAF
Method 1316 Rationale and Limitations
> Designed to provide LSP as a function of 0.5 < L/S < 10 mL/g dw. Provides
basis to approximate early leachate concentrations and determination of
availability or solubility controlled leaching.
> Particle size and contact intervals, mixing to approach equilibrium.
> Conceptual paradigm is applicable for organic species.
Limitations for Use with Organics
Eluant and mixing conditionsdo not address potential for deflocculationand
colloid formation.
Provisions for selection of apparatus materials, filtration, sample mass,
extraction volumes, minimizing volatilization losses are not provided.
C-48
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LEAF
Why is Relative Hydraulic Conductivity Important?
contaminants transfer
across external
surface area
groundwater
contaminants leach
at equilibrium
concentration
Water is diverted around material
Exposed surface area limitedto
external surface
Contaminant release rate controlled
by Rate of Mass Transfer
Water percolates through material
Continuous pore area exposed
Release concentrations based on
Liquid-Solid Partitioning
(local equilibrium)
Contaminant release under equilibrium conditions will always
be greater than under mass transport rate limited conditions
Selecting Methods and Data Use
Fundamental leaching
properties
Availability, Equilibrium data,
Site information*
x^x-
Fundamental leaching
properties
Availability data. Equilibrium
data. Mass Transfer data
Site information*
LEAF
Treatment Effectiveness
Cumulative Release from S/S Treated & Untreated MGP Soil
g
Qj .
I
ra
c
s.
100,000
10,000
1,000
10
1
0.1
Total PHE in Untreated Soil
Total PHE in S/S Material *<ฃL.
1, **"
*
_. ""
S/S Material
.
o Untreated Soil
0.1 1 10
Leaching Time (days)
Total Content
Soxhlet Extraction
S/S Material
Method 1315
(modified for organics)
Untreated Soil
Method 1314
(percolation column)
Site-specific info
100 relating flowrateto US
LEAF
Monolith Diffusion Scenarios
Laboratory vs field
conditions
Variable water contacting
sequence, chemistry
Saturated or unsaturated
Carbonation, oxidation
ingress
Coupled degradation
mechanisms with
leaching
C-49
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LEAF
Percolation with Mobile-Immobile Zones Scenarios
Laboratory vs. field
conditions
Variable water flow
rate, chemistry
Effects of preferential
flow
LEAF
Percolation with Radial Diffusion Scenarios
Laboratory vs field
conditions
Cracked materials
or packed beds
Effects of
preferential flow
Variable water flow
rate, chemistry
L E A F
Lab & Field Scenario Rationale and Limitations
> Development of source terms follows a tiered approach, with simple
approximation (reasonable bounding) used based on mass balance,
chemical thermodynamic, and mass transport principles.
> More complex models used to provide basis for developing leaching source
terms under conditions that are not direct applications of laboratory test data
or simpleanalytical solutions (e.g., finite bath leaching from monolith,
evolving boundary conditions and chemistry). Includes consideration of
sorptive phases, aqueous phase complexation, NOM, DOC, redox, etc.
> Conceptual paradigm is applicable for organic species.
Limitations
Does not include consideration of NAPLs, vapor phase transport,
biodegradation/transformation.
Conclusions
> Measurement of intrinsic leaching characteristics and development of
source terms based on mass balance, thermodynamic and mass
transport principles provides a robust leaching assessment framework
that is applicable to both inorganic and organic species.
> Numerical modeling is required when direct extension of laboratory
results to field conditions is not applicable and analytical solutions are
not available.
> A tiered approach to source-term estimation provides for a balance
between extent of testing, complexity of source-term development, and
end-user needs.
> Current LEAF test methods do not include specifications specific to
many classes of organic species. Important factors that are not
addressed specifically for organicsinclude selection of apparatus
materials, filtration, sample mass, extraction volumes, minimizing
volatilization losses, maintaining "dilute" boundary conditions (for
monoliths). Use in source terms does not address NAPLS and vapor
phase transport.
C-50
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