EPA/625/R-03/010
October 2003
U.S. EPA Workshop on Managing Arsenic
Risks to the Environment: Characterization of
Waste, Chemistry, and Treatment and Disposal
Proceedings and Summary Report
Denver, Colorado
May 1-3, 2001
National Risk Management Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
-------
Notice
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development, funded and man-
aged the workshop and research described here under Contract 68-C7-0011 to Science Applications International
Corporation. The Office of Solid Waste also provided funding forthis effort. It has been subjected to the Agency's peer
administrative review and has been approved for publication as an EPA document. Statements captured in the breakout
session discussions and summaries are those of the participants, not necessarily reflective of the EPA. Abstracts 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.
-------
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 environ-
mental 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 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 to anticipate emerging problems. NRMRL's research provides solutions to environ-
mental problems by: developing and promoting technologies that protect and improve the environment; advancing sci-
entific 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 to assist the user community and to link researchers with
their clients.
Hugh W. McKinnon, Director
National Risk Management Research Laboratory
-------
Acknowledgments
Many people contributed their expertise to the preparation and review of this publication. Overall technical guidance was
provided by Douglas Grosse of EPA's National Risk Management Research Laboratory (NRMRL). The document was
prepared by Lisa Kulujian and Kyle Cook of Science Applications International Corporation (SAIC), with assistance
from Peggy Groeber and Evelyn Hartzell. The following people provided guidance and review:
Douglas Grosse EPA, NRMRL
Paul Randall EPA, NRMRL
Robert Ford EPA, NRMRL
Jim Berlow EPA, Office of Solid Waste
Christopher Impellitteri EPA, NRMRL
Linda Fiedler EPA, NRMRL
Richard Wilkin EPA, NRMRL
Robert Simms SAIC
IV
-------
Table of Contents
Notice ii
Foreword iii
Acknowledgments iv
Table of Contents v
List of Acronyms vi
1.0 Executive Summary 1
1.1 Introduction 1
1.1.1 Purpose and Goals of the Workshop 1
1.1.2 Background 1
1.2 Summary of Breakout Session Discussions 2
1.2.1 Source Identification 2
1.2.2 Treatment and Disposal 3
1.2.3 Arsenic Chemistry 4
2.0 Plenary Session 6
3.0 Breakout Sessions 30
3.1 Source Identification Session 30
3.1.1 Discussion Review 30
3.1.1.1 Summary of Important Conclusions and Recommendations from the
Source Identification Session 37
3.1.2 Source Identification Session Speaker Abstracts 37
3.2 Treatment and Disposal Session 47
3.2.1 Discussion Review 47
3.2.1.1 Summary of Important Conclusions from the Treatment and Disposal
Session 50
3.2.1.2 Recommendations or Research Needs from the Treatment and Disposal
Session 51
3.2.2 Treatment and Disposal Session Speaker Abstracts 51
3.3 Arsenic Chemistry Session 64
3.3.1 Discussion Review 64
3.3.1.1 Summary of Important Conclusions from the Arsenic Chemistry Session 70
3.3.1.2 Recommendations or Research Needs from the Arsenic Chemistry
Session 70
3.3.2 Arsenic Chemistry Session Speaker Abstracts 71
Appendix A-Workshop Agenda A-1
Appendix B-Steering Committee and Attendees B-1
Appendix C-Selected Publications Bibliography C-1
-------
List of Acronyms
AMD
ATP
AVS
BOAT
BRS
CAA
CCA
CERCLA
CWA
DMAA
DOD
DOE
EM
EPA
EPCRA
FDA
GPS
HGMS
ISCF
LDR
LRPCD
MCL
MEP
MMAA
MPW
NCEA
NERL
NHEERL
NPL
Acid Mine Drainage
Adenosine Triphosphate
Acid Volatile Sulfide
Best Demonstrated Achievable Technology
EPA Biennial Report System
Clean Air Act
Chromated Copper Arsenate
Comprehensive Environmental Response, Compensation, and Liability Act
Clean Water Act
DimethylarsinicAcid
U.S. Department of Defense
U.S. Department of Energy
Electron Microprobe
U.S. Environmental Protection Agency
Emergency Planning and Community Right to Know Act
Food and Drug Administration
Global Positioning System
High Gradient Magnetic Separation
In-Situ Chemical Fixation
Land Disposal Restriction
Land Remediation and Pollution Control Division (NRMRL)
Maximum Contaminant Level
Multiple Extraction Procedure
MonomethylarsonicAcid
Mineral Processing Waste
National Center for Environmental Assessment
National Exposure Research Laboratory
National Health and Environmental Effects Research Laboratory
National Priorities List
VI
-------
NRMRL
NURE
ORD
ORP
OSW
PAH
PIG
PRB
RCRA
RME
ROD
S/S
SMZ
SPLP
SPRD
TCLP
TRI
TSD
TTSD
USGS
WET
WTP
ZVI
List of Acronyms (Cont.)
National Risk Management Research Laboratory
National Uranium Resource Evaluation (a program)
Office of Research and Development
Oxidation-Reduction Potential
Office of Solid Waste
Polynuclear Aromatic Hydrocarbons
Peat, Iron, and Gypsum
Permeable Reactive Barrier
Resource Conservation and Recovery Act
Risk Management Evaluation
Record of Decision
Solidification/Stabilization
Surfactant-Modified Zeolite
Synthetic Precipitation Leaching Procedure
Subsurface Protection and Remediation Division (NRMRL)
Toxicity Characteristic Leaching Procedure
Toxics Release Inventory
Treatment, Storage, and Disposal
Technology Transfer and Support Division (NRMRL)
U.S. Geological Survey
Waste Extraction Test
Water Treatment Plant
Zero-Valent Iron
VII
-------
1.0 Executive Summary
1.1 Introduction
1.1.1 Purpose and Goals of the Workshop
A workshop titled "Managing Arsenic Risks to the Environment: Characterization of Waste, Chemistry, and Treatment and
Disposal," was held on May 1 - 3, 2001, in Denver, Colorado. This workshop was sponsored and facilitated by the U.S.
Environmental Protection Agency (EPA) Office of Research and Development (ORD) and Office of Solid Waste (OSW),
Emergency Response. The purpose of the workshop was to achieve three goals:
1) Examine the chemical fundamentals related to arsenic chemistry, speciation, and analytical issues;
2) Examine the state of practice of existing and emerging technologies that treat and properly dispose of arsenic
wastes; and
3) Identify/characterize sources of arsenic.
The workshop was not designed to cover issues related to drinking water; rather, to focus on characterization of wastes,
arsenic speciation, and treatment and disposal practices. To facilitate discussion of these issues, the workshop fea-
tured a series of speaker presentations at a plenary session, and moderated technical breakout sessions with addi-
tional speaker presentations and participant discussions. Topics for the 12 presentations during the plenary session
included arsenic waste, chemistry, and treatment and disposal, as well as regulatory perspectives and information
management. Technical breakout sessions looked more closely at arsenic chemistry, source identification, and treat-
ment and disposal issues: presentations during these sessions were more specific to the session topics.
Presenters were from the EPA, U.S. Geological Survey (USGS), Government of Canada, state agencies, academia,
federal laboratories, consulting firms, and technology developers. Presenters and other workshop participants were
known fortheir knowledge and involvement in the field of arsenic waste and management.
This report provides a summary of the key issues pertaining to managing arsenic risks to the environment, followed by
plenary speaker abstracts, breakout session discussion review and speaker abstracts, and lastly, appendices with the
workshop agenda, attendees, and a selected arsenic publications bibliography. It is hoped that this information will be
useful to anyone involved with managing arsenic issues, and will prompt additional work and research to resolve
outstanding arsenic issues.
112 Background
It is well known that arsenic, especially the inorganic forms, is very toxic and is a carcinogen. The chemical nature of
arsenic compounds, in particulartheir tendency to change valence states or chemical form under a wide range of pH and
redox conditions, makes it difficult to assess their fate and mobility in the environment. Furthermore, case studies show
that arsenic wastes that have been treated to U.S. regulatory standards are found to leach outof landfilled waste. A key
issue for this workshop was, therefore, effective treatment and stabilization of arsenic wastes to minimize risk to health
and the environment.
Arsenic wastes are generated from several industries such as mining and smelting operations. Currently in the U.S.,
arsenic contaminated wastes are subject to the Resource Conservation and Recovery Act (RCRA) land disposal restric-
tions and must be treated to meet Toxicity Characteristic Leaching Procedure (TCLP) limits. A RCRA hazardous waste is
defined as a waste that produces an extract containing more than 100 times the maximum contaminant level (MCL) in
drinking water for that specific chemical. The MCL for arsenic (50 ppb) was recently subjected to a critical review due to
concerns about the association of long-term exposure to arsenic and serious health problems such as skin and internal
cancers and cardiovascular and neurological effects. Asa result of this review, a change in the arsenic MCL from 50 ppb
to 10 ppb was promulgated. This new, lower MCL may have implications related to public perception of the risks
associated with arsenic waste and contamination, treatment standards and effectiveness, and cost issues.
EPA funded several arsenic treatment studies throughout the 1990s and has research ongoing. Containing and minimiz-
ing arsenic contamination has been a priority for ORD. Projects have included mine waste technology, groundwater
treatment using permeable reactive barrier (PRB) technology, transport and fate in sulfidic systems, and drinking water
research including MCLs. OSW has been reviewing and re-evaluating solid waste treatment standards and evaluating
the effectiveness of land disposal restrictions for management of arsenic waste.
1
-------
Challenges and research opportunities for arsenic include:
• Arsenic chemistry and mobility at contaminated sites
• Risk assessment
• Public perception and trust in the science
• Long-term stability of treated arsenic wastes
• Stabilization design issues and organics interference
• Measurement of treatment effectiveness
• Disposal of residuals from drinking water plants
The following technical session discussion summaries speak to these challenges and other issues. Additional informa-
tion is available in the speaker abstracts and detailed session discussions.
1.2 Summary of Breakout Session Discussions
1.2.1 Source Identification
In this technical session, researchers presented information about natural and anthropogenic (influence of man) sources
of arsenic; characterizing and identifying arsenic in soils and sediments, coal deposits, and mining environments; and
management of arsenic risk in marsh environments and the mining and wood treating industries. Arsenic data were
presented from research at natural and industrial sites, and approaches for best communicating arsenic contamination
and risk data to the public were discussed. Group discussions centered around three general questions:
1) What are the primary sources that contribute to arsenic releases to the environment?
2) What are the significant data gaps and information needs for characterizing and identifying arsenic sources and
waste forms?
3) What are the important insights to be conveyed regarding the management of arsenic risks for decision makers?
Primary Sources. Arsenic in the environment occurs from both natural and anthropogenic sources. There has been an
effort to differentiate between natural and anthropogenic impacts, particularly in areas where expansion and development
is occurring and with limited water supplies. There is also a growing appreciation of the regional nature of residual arsenic
contamination from agricultural and other anthropogenic sources such as copper and sodium-based arsenicals from
herbicides and pesticides. Based on the information presented in this session, the primary natural sources of arsenic
releases to the environment are: hot springs (geothermal), igneous rock (basalt), sedimentary rock (organic/inorganic
clays, shale), metamorphic rock (slate), seawater, mineral deposits, and volcanoclastic materials/releases. The primary
anthropogenic sources of arsenic releases to the environment include: historic mining sites, pesticide/herbicide use,
combustion byproducts from burning fossil fuels, animal feeds/waste byproducts, historic wood preserving sites, medici-
nal uses, fertilizer use, landfill leachate, glass production, and tanneries.
Information Needs for Identifying and Characterizing Arsenic Sources and Wastes. Information is needed on anthro-
pogenic and natural sources to identify parameters that affect treatment and to assess effects from anthropogenic
constituents such as petroleum hydrocarbons from leaky pipelines. Site characterization techniques (e.g., oxidation,
species concentration) and guidance are also needed for collecting and analyzing data. It may be possible to determine
the source of the arsenic based on the presence of othersource-specific anthropogenic chemicals/elements (tracers) or
to understand the history of a pollution source by examining reservoir sediment samples, dendrochronological (tree wood)
samples, and local records. Soil characterization information is needed that defines "natural" arsenic concentrations and
conditions in different types of soils, and the impacts that arsenic introduction can have on different types of soil. More
information is needed on arsenic mineralogy, bioavailability, leachability, and speciation, particularly forAs(lll) and As(V).
Generic guidance is needed that can be used to help identify impacted media, characterize contamination, and assess
potential impacts. Finally, information or techniques are needed which can be used to predict the future impacts of an
arsenic release, including fundamental kinetics/thermodynamics.
Management of Arsenic Risks. Some of the primary conclusions from this session concerning management of arsenic
risks are: 1) it is important to monitor arsenic releases and provide this information to the public; 2) the risk from an
arsenic release needs to be well defined, and it is also important to differentiate real versus perceived risk; 3) during a
risk characterization, the environmental effects of the arsenic release should be predicted; and 4) it is important to
understand how to fix an arsenic contamination/release problem, and then monitor the performance of the selected
corrective action.
-------
There was a general consensus in this technical session that there is not enough information, either nationally or
regionally, on background arsenic concentrations in soils. Since this information is very important, a national database/
map is needed to address metals in soils. It is important, however, to identify criteria for collecting these samples, such
as depth and the analytical method to use, before proceeding any further with this effort. There are also a number of
sample libraries that could be used to develop the background information needed to assess human health and envi-
ronmental impacts from arsenic. Efforts to set standards are complicated by difficulties determining the difference
between "pristine" background concentrations and anthropogenic inputs after contamination has occurred. Although
MCLs are used to protect human health, it is necessary to define how they relate to natural sources with high variability.
Analytical methods must have low enough method detection limits (typically 10 to 20% of the MCL) to provide quanti-
tative arsenic MCL results. The issues raised in this summary are discussed in greater detail in the Discussion Review
section. As part of this discussion, important conclusions concerning the current state of the science are listed as well
as recommendations and research needs for improving our technical capability to resolve arsenic source identification
issues.
12.2 Treatment and Disposal
There was a series of 11 presentations in the arsenic treatment and disposal breakout session. Speakers from Austra-
lia and Canada as well as the U.S. provided the arsenic issues and the challenges to assess the chemical fundamen-
tals, as well as the treatment choices that are utilized to minimize arsenic's impact on the environment.
Group discussions centered around these general questions:
1) What are the long-term stability issues with regard to land disposal (i.e., on-site storage or landfills) of arsenic
stabilized wastes?
2) How do current advances (i.e., molecular chemistry, leaching mechanisms) impact the areas of arsenic treatment
and disposal?
The highest priority research needs in advancing arsenic treatment and disposal were also identified.
In 1996, the U.S. demand for arsenic in market products was estimated at 22,000 metric tons, making the U.S. the world's
largest consumer. Most arsenic is used in wood preservatives, but significant use also occurs in agricultural chemicals,
glass production, and metal alloys. These industrial practices and metals mining and smelting operations generate ar-
senic-bearing wastes. In 1998, the metal mining industry managed the most arsenic waste, over 617 million pounds or
96% of the total mass of arsenic waste managed. Gold mining accounted for about 93% of the arsenic mining wastes.
Several federal cleanup programs, such as the Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA) and RCRA, manage the remediation of contaminated sites that may contain arsenic. Most of the detailed
data are available due to the cleanup of Superfund sites.
Long-term Stability. There are a number of test methods used to predict the performance of stabilized arsenic wastes,
including the TCLP, Synthetic Precipitation Leaching Procedure (SPLP), and Multiple Extraction Procedure (MEP). In
California, the Waste Extraction Test (WET) is used. There are issues with all of these test methods that make it difficult
to predict the effects of time on the stability of treated wastes. Although EPA requires the use of TCLP for predicting the
performance of stabilized arsenic wastes in a landfill, several concerns have been raised about the ability of this method
to predict long-term stability. In addition, the other methods give different kinds of performance results and are not truly
comparable between sites. Models that predict thermodynamic and kinetic variables can also be used to simulate
long-term conditions and determine treated arsenic waste stability. The disposal environment of the waste must also
be considered. For example, avoid placing wastes in saturated zones, and utilize capping materials to protect waste
and minimize contact with leaching agents.
Current Advances. In research and development, advances in techniques and instrumentation have allowed for greater
site investigation. For example, X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) often provide a
better understanding of a material's microstructure. However, these advances have not yet transferred into field perfor-
mance specifications. Researchers are investigating the toxicity of different arsenic forms such as As(lll) and As(V).
This research may result in developing different regulations for different species of arsenic.
Research Needs. Important research needs for arsenic treatment and disposal are: 1) improved understanding of
long-term stability and protocols for simulating long-term conditions and performance, 2) improved understanding of
waste chemistry, speciation, and biogeochemistry, 3) improved understanding of waste microstructure and mineralogy,
-------
4) evaluation of biological processes (bacteria, fungi, plants) on arsenic mobilization, and 5) improved understanding of
arsenic toxicity issues.
The change in the arsenic MCL from 50 ppbto 10 ppb could prompt EPA to change the required treatment standard to a
value that is at or below the current TCLP regulatory level of 5 mg/L. If this is the case, then it is important to assess
whether or not the current array of treatment options could achieve the potentially more stringent treatment require-
ments. However, treating high-concentration arsenic wastes is difficult and treatment costs associated with these
technologies can be high. The key question is: are the high treatment costs justified by the incremental reduction in
potential risk associated with arsenic in treated wastes? The issues raised in this summary are discussed in greater
detail in the Discussion Review section. As part of this discussion, important conclusions concerning the current state
of the science are listed as well as recommendations and research needs for improving our technical capability to
resolve arsenic waste treatment and disposal issues.
1.2.3 Arsenic Chemistry
The basis forthe reliable prediction of arsenic mobility and treatment in subsurface systems is dependent on an adequate
understanding of the chemical processes that control arsenic partitioning between the aqueous and solid phase. While
significant effort has been expended to study the factors controlling arsenic fate and transport in environmental systems,
the ability to predict arsenic mobility and exposure in a regional or ecosystem context is still inadequate. This inadequacy
derives both from an incomplete compilation of the necessary chemical information and the application of inappropriate
methods to collect these data. The goal of this session was thus to task a panel of experts to establish the current state
of knowledge and to identify future areas of research and the most reliable pathways to fill existing data gaps.
Group discussions centered around three general questions:
1) Is our knowledge of arsenic speciation and transformation adequate to identify pathways and routes of mobility?
2) Are current collection, preservation, and analytical techniques sufficient for defining arsenic chemistry in natural
and engineered systems?
3) Are existing leaching procedures adequate for characterization of arsenic-bearing waste materials?
Arsenic Mobility. Since arsenic is a redox-sensitive element, its chemical speciation is dependent on changes in
system redox parameters that are driven by biotic and abiotic processes. The mobility of arsenic is tied to the cycling
of major elements such as carbon, iron, and sulfur between the solution and solid phase in natural and engineered
systems. While there is generally a sound phenomenological understanding of arsenic mobility, the ability to provide a
quantitative assessment is limited. This limitation is due, in part, to the complexities of coupling chemical and hydrody-
namic models in complex heterogeneous systems. This limitation is compounded by the existence of knowledge gaps,
including: 1) coupling of arsenic chemical speciation to the cycling of redox-sensitive nutrients such as nitrogen, 2)
knowledge of aqueous arsenic speciation in anoxic environments, 3) protocols for applying sorption models to describe
arsenic solid phase partitioning, and 4) predictive tools and modeling approaches to describe the influence of microbial
activity on arsenic mobility.
Analytical Tools. In general, existing analytical tools are satisfactory for quantification of arsenic chemistry in aqueous
systems. However, attempts to apply these tools in a uniform manner for evaluation of all sample matrices are prob-
lematic. A matrix was developed to point out the strengths and limitations of the various analytical tools, and this
information can be used as a guide for developing the most appropriate analytical protocol on a site- or case-specific
basis. This limitation also applies to attempts to apply a single technique for preservation of arsenic chemistry prior to
analysis. While there was agreement that filtration, acidification, and light exclusion are generally adequate for preser-
vation of most aqueous samples, this approach must be validated and modified as required to achieve desired site-
specific data quality objectives.
Waste Form Characterization. Leach tests have been developed to provide guidance as to the stability of solid waste
forms priorto orfollowing land disposal. Limitations have been identified forthe application of existing test procedures for
evaluation of arsenic stability (or mobilization potential) in waste solids. In particular, research indicates that the TCLP
provides results that do not reflect the in-situ leaching behavior of arsenic for municipal solid waste. Design of leach
tests should be governed both by the application of the test results and/or the in-situ chemistry anticipated for the
disposal environment. For example, tests designed to assess differences in treatment process effectiveness may differ
from those employed to assess the post-disposal leach potential of a solid waste form. Assessment of in-situ leach
potential should focus on critical geochemical parameters that are characteristic for the disposal environment.
-------
A re-occurring theme for all of the topics addressed in this session was that a degree of flexibility is required for
application of the knowledge and tools employed to resolve arsenic waste problems. The complexity of arsenic chem-
istry is sufficiently high to preclude rigid protocols for site assessment and waste characterization. The issues raised in
this summary are discussed in greater detail in the Discussion Review section. As part of this discussion, important
conclusions concerning the current state of the science are listed as well as recommendations and research needs for
improving our technical capability to resolve arsenic waste chemistry issues.
-------
2.0 Plenary Session
The following extended abstracts are provided for the oral presentations made by invited speakers during Day One of
the Workshop, Plenary Session. Speakers were selected by the Steering Committee, and the topics were intended to
provide some foundation for subsequent discussions that occurred both formally and informally during the balance of the
Workshop. The Plenary Session presentations covered a range of arsenic topics from regulatory to scientific issues.
EPA researchers discussed the ORD and OSW perspectives on contamination issues, treatment efforts, treatment
standards, and testing issues. Other EPA topics included arsenic sources, research on microbial activity, and the Toxics
Release Inventory (TRI). Other researchers discussed arsenic issues for mining, groundwater and drinking water, and
arsenic geochemistry, leaching, and treatment options.
Additional oral presentations were made on Day Two during the Breakout Sessions. These presentations were in-
tended to complement the session topics and provide a basis for discussion for each session. The extended abstracts
for these oral presentations are presented in Section 3.0, Breakout Sessions.
It should be noted that the abstracts were not part of the formal peer-review process which the remainder of this
document underwent, and may represent opinions or personal points of view in some cases. Any references cited in
the abstracts are the responsibility of the authors.
Presentation materials (visuals) for the Plenary Session and Breakout Session speakers are not included in this
Proceedings document, only abstracts. A few speakers did not prepare abstracts, only presentation materials. However,
speaker presentation materials can be viewed online at the EPA Technology Transfer website. The website address for
these materials is www.epa.gov/ttbnrmrl/arsenictech.htm. Or, for further information regarding this Technology Transfer
product, please contact Doug Grosse via email at: grosse.douglas@epa.gov.
-------
The Current Status of Arsenic Research in the U.S. EPA's
Office of Research and Development
Christopher A. Impellitteri and Paul M. Randall
U.S. Environmental Protection Agency
26 W. Martin Luther King Drive, Cincinnati, OH 45268
T: 513-569-7673, F: 513-569-7620
E: lmpellitteri.Christopher@epa.gov and Randall.Paul@epa.gov
Notice
This paper has been reviewed in accordance with the U.S. Environmental Protection Agency's (EPA's) peer and adminis-
trative review policies and approved for presentation and publication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
Abstract
The mission of EPA's Office of Research and Development (ORD) is "to conduct leading-edge research and foster the
sound use of science and technology in fulfilling EPA's mission to protect human health and safeguard the natural
environment" (USEPA, 2001). ORD researchers have examined how metabolic processes affect arsenic (As) specia-
tion in humans as well as carcinogenic effects of As (USEPA, 1999). An epidemiological study conducted by ORD
researchers in Utah, regarding long-term exposure to As in drinking water, has provided essential data to compare with
studies concerning non-US populations (Smith et al., 1992; Nickson et al., 1998; Karim, 2000). Other studies have
been initiated by ORD scientists and engineers examining As treatment and management in solid wastes and soils.
This abstract will briefly discuss the current status of As research within ORD.
Drinking Water Issues
EPA recently decreased the maximum contaminant level (MCL) for As in drinking water from 50 mg/L to 10 mg/L. Two
significant issues arise from the lowering of the arsenic MCL in drinking water. The first issue concerns improvement of
existing water treatment methods for water treatment plants (WTPs) to cost-effectively meet the new arsenic MCLs.
Researchers in ORD's National Risk Management Research Laboratory (NRMRL) address this issue by coordinating
studies on chemical and physical removal of As from water. One study found that the removal of natural iron signifi-
cantly reduced soluble As (USEPA, 2000a). Another study examined WTPs that employed ion exchange and activated
alumina systems. Both systems were found capable of reducing arsenic concentrations from 50 to 70 ^g/L to 5 ^g/L
providing that proper media regeneration (or change-out of exhausted media) was followed (USEPA, 2000b). A third
study analyzed the long-term performance of two coagulation/filtration plants and a lime softening plant (USEPA, 2000c).
The coagulation/filtration plants consistently achieved low levels of As in treated water (< 5 ^g/L). The study suggested
that the primary mechanism of As removal was by co-precipitation with metal hydroxides. The lime softening plant did
not consistently reduce As levels in treated water to low levels. This study determined that As removal from the water
was low because of competition for binding sites by carbonate species and/or pH effects. The second significant issue
that would result from reducing the As MCL in drinking water concerns As in WTP residuals. Research funded by
NRMRL has provided fundamental data describing As in residuals from water treatment processes (USEPA, 2000d).
This research compares As concentrations in residuals from five different water treatment processes and also illus-
trates some differences in state policies concerning disposal of As containing residuals.
Closely tied with NRMRL's research on drinking water issues is research that is currently underway in ORD's National
Exposure Research Laboratory (NERL). NERL is currently working on methods for preserving As species in drinking
water samples and the development of As speciation methodologies for separation of arsenite and arsenate. This work
provides data to support water treatment decisions in utilities affected by changes in the As MCL. NERL researchers
are also developing analytical methods for As speciation analysis in foods (e.g., seafood) and urine. NERL works in
conjunction with the Food and Drug Administration (FDA) on projects that examine methods for speciation of As in daily
diets. This work will aid in assessing risk of As exposure associated with diet. On-going NERL research will examine the
bioavailability of As species in water, soils, and food constituents (USEPA, 1998).
Health and Toxicological Issues
ORD's National Health and Environmental Effects Research Laboratory (NHEERL) currently conducts research that can
be broadly divided into three categories: 1) mechanisms/modes of As as a carcinogen and toxicant; 2) biomarkers and
population studies; and 3) modifiers of susceptibility to toxic and carcinogenic effects. Research performed by the
NHEERL on the mechanisms and modes of As toxicity has provided critical insight concerning the nature of As toxicity.
-------
For example, NHEERL researchers have shown that methylated trivalent arsenicals appear to be direct-acting
genotoxicants, which distinguishes them from other forms of As previously studied (Mass et al., 2001). Research
conducted in the area of mechanisms and modes of Astoxicity include biomethylation effects, interspecies (rat, mouse,
guinea pig, human) comparisons of As carcinogenicity, uptake and fate in living organisms, and protein binding and
effects on human cell DMA methylation. Work on biomarkers and population studies include epidemiological studies on
human exposure to As, both in the US and abroad, and identification of biomarkers (e.g., heme oxygenase and urinary
porphyrins) that could adequately indicate exposure to As species. NHEERL conducts leading-edge research in the
area of As susceptibility modifiers. Studies into the characterization and behavior of the enzyme human As
methyltransferase will lead to a better understanding of the ability for human populations to develop resistance to As
toxicity. Research on modifiers of As behavior in organisms also includes studies on heat shock proteins, selenium and
dietary folate deficiencies.
ORD's National Center for Environmental Assessment (NCEA) focuses on human health issues and works in conjunction
with NHEERL to advance our understanding of As related exposure and risk assessment. Current NCEA activities
include assessment of chronic As exposure from drinking water sources and the effects of As exposure on human
reproduction. This long-term study examines data from exposed and control populations in Chile (Hopenhayn-Rich, et al.,
2000). The NCEA works closely with the National Cancer Institute and the National Institute of Environmental Health
Sciences in the establishment and maintenance of the International Tissue and Tumor Repository on Chronic Arsenosis.
This repository holds tissues and fluids from cases of As poisoning and environmental samples (e.g., coal). The reposi-
tory also safeguards data and literature and develops databases for protocols and methods of specimen handling, stor-
age, transportation and analysis.
Groundwater Issues
NRMRL's Subsurface Protection and Remediation Division (SPRD) leads research pertaining to groundwater issues.
Though inextricably linked with solid waste and soil, groundwaterwill be considered separately here. The SPRD currently
conducts research regarding As mobilization in groundwater, oxidation-reduction reactions of As species in groundwater,
and remediation of As contaminated groundwater. SPRD researchers perform these studies in both the laboratory and
field. For example, work evaluating permeable reactive barriers (PRBs) will examine the efficacy of this remediation
technique on As removal (and other contaminants) from groundwater. Pilot-scale PRB studies will be used to identify
effective reactant media for successful, long-term uptake of inorganic contaminants, examine metal uptake mecha-
nisms, and evaluate barrier longevity and long-term PRB stability.
Solid Waste/Soil Issues
SPRD also provides essential research in the area of subsurface As fate and transport issues. Research includes
attenuation/stabilization of As on solid phases in soil/vadose zone systems, measurement procedures and protocols for
sampling of soils for As studies, and geochemical controls on As speciation in soils. In addition to studies in oxic
environments, research regarding the fate and transport of As in anoxic systems is underway in the SPRD. Laboratory
studies will provide key data for identification of mechanisms and rates of As sorption/precipitation reactions in sulfidic
media. This work will provide a better understanding of As behavior in anoxic systems and lead to improved practices for
field monitoring in these geochemically complex systems.
The Land Remediation and Pollution Control Division (LRPCD) works in conjunction with the SPRD on As soils/solid
waste issues. Researchers in the LRPCD are currently researching As source contamination issues. These studies
will focus on As contamination of solids (soils, mine tailings, sediments) from agricultural sources, mine wastes and
treated lumber sources. The researchers will examine desorption of As from solids (effects of pH and dissolved organic
matter), solution speciation, and As bonding at the molecular level. Research will also be carried out by LRPCD in the
application of thermodynamic theories to leaching studies in order to better characterize specific scenarios and provide
more focused direction on methods to minimize As mobilization. Other projects include work on As leaching from
mineral processing waste (MPW). The researchers will examine several leaching methods on MPW and compare
these data with that from the toxicity characteristic leachate procedure (TCLP- EPA Method 1311). These engineers
and scientists will also examine the relationships between leachate chemistry data and TCLP data from landfills.
Risk Management
NRMRL's Technology Transfer and Support Division (TTSD) provides a cohesive, cooperative environment where experts
in specific fields can meet and formulate Risk Management Evaluations (RMEs). RMEs play a crucial role in providing a
balanced approach to policy formulation and regulation based on sound science and engineering research. Findings from
ORD's research activities combined with other important aspects such as cost-of-compliance issues and health/eco-
nomic benefits from risk reduction aid in focusing future research efforts within the ORD.
-------
In addition to the projects mentioned previously, ORD strives to work closely with EPA regional offices. This ensures that
certain aspects of research projects focus on site-specific issues. By working closely with regional offices, ORD aids in
addressing immediate, site-specific needs while gaining fundamental knowledge for contribution to our understanding of
As and its effects on human health and the environment.
References
Hopenhayn-Rich, C., S. Browning, I. Hertz-Picciotto, C. Ferreccio, C. Peralta, and H. Gibb. 2000. Chronic arsenic
exposure and risk of infant mortality in two areas of Chile. Env. Health Perspec. 108:667-663
Karim, M. 2000. Arsenic in groundwater and health problems in Bangladesh. Wat. Res. 34:304-310.
Mass, M.J., A. Tennant, B.C. Roop, W.R. Cullen, M. Styblo, D.J. Thomas and A.D. Kligerman. 2001. Methylated
trivalent arsenic species are genotoxic. Chem. Res. Tox. 14:in press.
Nickson, R., J. McArthur, W. Burgess, K.M.Ahmed, P. Ravenscroft and M. Rahman. 1998. Arsenic poisoning of
Bangladesh groundwater. Nat. 395:338.
Smith, A.M., C. Hopenhayn-Rich, M.N. Bates, H.M. Goeden, I. Hertz-Picciotto, H.M. Duggan, R. Wood, M.J. Kosnett
and M.T. Smith. 1992. Cancer risks from arsenic in drinking water. Env. Health Perspec. 97:259-267.
USEPA. 1998. Research Plan for Arsenic in Drinking Water. February, 1998. EPA/600/R-98/042
USEPA. 1999. Research and Development Fiscal Years 1997-1998 Research Accomplishments. December, 1999.
EPA-600-R-99-106
USEPA. 2000a. Arsenic Removal from Drinking Water by Iron Removal Plants. August 2000. EPA/600/R-00/086
USEPA. 2000b. Arsenic Removal from Drinking Water by Ion Exchange and Activated Alumina Plants. October, 2000.
EPA/600/R-00/088
USEPA. 2000c. Arsenic Removal from Drinking Water by Coagulation/Filtration and Lime Softening Plants. June,
2000. EPA/600/R-00/063
USEPA. 2000d. Regulations on the Disposal of Arsenic Residuals from Drinking Water Treatment Plants. May, 2000.
EPA/600/R-00/025
USEPA. 2001. Office of Research and Development Strategic Plan. January 2001. EPA/600/R-01/003
-------
Arsenic Cycling in the Mining Environment
Rob Bowel I
SRK Consulting
Summit House, 9 Windsor Place, Cardiff CF10 3RS, Wales, UK
T: +44-2920-235566, F: +44-2920-665413, E: srk003@.aol.com
JeffParshley
SRK (US) Inc.
5250 Neil Road, Reno, NV
T: 775-828-6800
Occurrence of Arsenic in a Metal Mine
Over 200 As-containing minerals have been identified in nature. Of these 60% are arsenates, 20% sulfides and sulfosalts,
10% are oxides, and the remainder are arsenides, native elements and metal alloys. Arsenic naturally occurs in chalcophile
hydrothermal mineral deposits and is more rarely associated with volcanic or magmatic rocks. Rare arsenic phases are
also known to occur in fumaroles and geothermal systems. Occasionally arsenic can also occur associated with
sedimentary pyrite in sedimentary rocks and in this environment has been considered to be the source for anomalous
concentrations of arsenic in drinking water in Wisconsin, Maine and Bangledesh. Within the United States the largest
occurrences of arsenic minerals occur associated with the Carlin-type mines of northern Nevada in the form of realgar
(AsS), orpiment (As2S3) and arsenic-bearing pyrite (upto 5wt%,) and the rare mineral, Galkhaite, a complexsulfosaltwith
the chemistry ([Cs,TI][Hg,Cu,Zn]6[As,Sb]4S12) which also occurs in the beltattheGetchell mine. Within Carlin ores, the
arsenic minerals are intimately associated with the ore elements or adjacent host rock.
The most common arsenic mineral, globally, is arsenopyrite. Arsenopyrite is common in many vein gold deposits, such
as those of Yellowknife, Canada or Homestake, South Dakota. It also occurs in granite hosted Cu-Sn veins such as
those of Cornwall, England.
Arsenic has long been used as an excellent "pathfinder element" because of its low abundance in most rock types and
concentration in hydrothermal deposits, as well as its generally low mobility. This coupled with sensitive analytical
protocols by conventional methods makes the element extremely useful in mineral exploration. For example, the
average concentration of As in hydrothermal ore deposits ranges from 500 ppm up to 10-wt% of an ore or altered host
rock. In unmineralized rocks the average concentration is less than 10 ppm, but can be up to 20 ppm in argillaceous
sediments.
Release of Arsenic In a Mine Site
Mining does not produce arsenic although it can be liberated when exposed to conditions in which the primary host
mineral is unstable and thus oxidises or weathers, for example when placed on a heaporwaste rock dump. Alternatively
when an As-hosting ore is chemically treated prior to liberation of the ore element such as during smelting, the arsenic
mineral may also be liberated from its matrix and in this form become mobile.
The concentration of arsenic liberated from such reactions is dependent on several factors:
Total concentration available; this in turn is related to geology of the original hydrothermal deposit.
The Eh-pH regime of the environment in which the arsenic is liberated.
The chemistry of natural waters in promoting release or attenuation of arsenic.
The total amount of arsenic available is entirely dependent on the proportion of arsenic minerals available in the deposit.
So for example, for a volcanogenic massive sulfide, high sulfide-gold deposit, or a Carlin deposit, high concentrations of
arsenic would be anticipated.
Control on the release of this arsenic is then dependent on environmental conditions. Typically in very acidic environ-
ments, for example those of Iron Mountain in California, arsenic mobility would be high. Equally, in high pH environments
high arsenic mobility would be anticipated as the major control would be adsorption onto mineral phases, and this would
be predicted to be low at higher pH for arsenic oxyanions. Within ambient systems arsenic can occur as arsenate
(HnAsO43-") orarsenite (HnAsO33-") complexes or in the presence of methylating agents as Monomethylarsonic acid (MMAA)
orbimethylarsinicacid (DMAA).
10
-------
Overthe natural pH range of most soils and waters the principal species of As (V) is H2AsO42-and of As (III) is H3AsO3,
of which the reduced form is the more mobile. For example, the speciation of arsenic in the principal reactions retaining
arsenic in soil, sediment and water are in acidic solutions, adsorption by ferric oxyhydroxides and to a lesser extent AI-Mn
oxides, clays and organic matter, and in alkaline solutions co-precipitation of As as arsenate and arsenite salts.
However, the rate of change in the oxidation state of arsenic is not rapid, so the predicted proportions of arsenic species
based on thermodynamic calculations do not always correspond to actual analytical results.
Due to the strong adsorption effect exerted on As in mildly acidic soils, As uptake by plants tends only to be significant
in alkaline soils or where extremely high As levels (>10000 mg/kg As) occur in the substrate.
600
400
200
£
H3As O4
H7As
HAS O,
•*•.
-200
-400
ASS
AsCC
Ground water
Asfcg I")
300-800
300-2000
> 2000
SCP lake
As
H Epilimnion 1mg/l
B Metali rnnionO.Smgfl
H Epilimnion Smg/l
PH
8
GROUNDWATER ARSENIC CONCENTRATION
FROM GETCHELL ON Eh - pH DIAGRAM
In the Bau area of Sarawak, Malaysia, high As levels in the soil (15-50000 mg/kg As) coupled with an alkaline soil pH (7.5-
8.4) has led to high As uptake in bamboo species (up to 4500 mg/kg in roots and 2650 mg/kg in leaves). In the Kelly Basin
in northern Nevada, Great Basin Sagebrush shows a similar tolerance and uptake of arsenic that is precipitated out as
oxide phases within the vascular part of the plant.
Options for the Control of Arsenic Dispersion
The metals industry is faced with the necessity of disposing of waste material in an environmentally safe manner. Over
the last two decades significant advances have been made in the design of waste facilities, and in stabilization and
treatment of mining effluents.
Arsenic waste disposal generally involves one of four options:
Physical stabilization through the use of engineered disposal facilities and institutional controls
Chemical stabilization of arsenic containing waste
Chemical treatment of effluents to produce saleable products, such as white arsenic oxides by the El Indio or
Warox processes or production of an insoluble arsenate such as ferric arsenate
Chemical stabilization of the arsenic waste by fixing it within an inert material such as cement, slags or silica
material
Currently all options are utilised in the mining industry, and all will be illustrated with examples of use. Future application
of such technologies will be discussed in terms of key parameters of cost, environmental stability of products and risks
associated with each.
11
-------
Arsenic in Groundwaters of the United States
Dennis R. Helsel, Ph.D.
Chief, Trace Element Synthesis
U.S. Geological Survey
P.O. Box25046, MS-415, Denver, CO 80225
T: 303-236-2101 ext. 227, F: 303-236-4912, E: dhelsel@usgs.gov
The U.S. Geological Survey has collected and analyzed arsenic in potable (drinkable) water from 18,850 wells in 595
counties across the U.S. during the past two decades. These wells are used for irrigation, industrial purposes, and
research, as well as for public and private water supplies. Arsenic concentrations in samples from these wells have been
shown to be similar to those found in source waters for nearby public supplies. Arsenic concentrations in groundwater
are generally highest in the West. Parts of the Midwest and Northeast also have arsenic concentrations that exceed 10
^g/L, the World Health Organization's provisional guideline for arsenic in drinking water. Arsenic concentrations ap-
pear to be generally lowest in the Southeast. The large number of samples, broad geographic coverage, and consis-
tency of methods produce an accurate and detailed picture of arsenic concentrations across the U.S.
12
-------
Managing Arsenic Occurrence Information in Drinking Water
Larry Scan Ian
Utah Department of Health
46 N Medical Drive, Salt Lake City, UT 84092
T: 801-584-8400, E: lscanlan(S)doh.state.ut.us
With the advent of the new Drinking Water maximum contaminant level (MCL) for arsenic set at 10 ^g/L on January 22,
2001, many states are reviewing their drinking water data for compliance with the new rule. The State of Utah has had
a computerized water quality database since 1978. This flat file format was gradually changed to a multiple-table rela-
tional database in the mid 1990s. This new database linked an inventory of public water supply sources with global
positioning system (GPS) locations, source production, and other data. This data was exported to Microsoft Access in
the mid-90s and used to summarize arsenic occurrence in Utah. Detection limits have varied from certified laboratories
submitting data since 1978, but an attempt was made to review all available data for each potentially regulated drinking
water source underthe new rule. Data which obviously did not agree with subsequent analyses results were flagged for
exclusion. The remaining data were counted forthe number of measurements made, averaged, and a standard deviation
of arsenic concentration for each source was computed. This approach allows a confident statement of arsenic concen-
tration where the data allow. Fifty water systems in Utah will need to provide treatment or dilution for eighty sources to
meet the new arsenic MCL by 2006. A statewide "compliance" list has been developed to begin working with systems
needing treatment. Utah's system, the findings produced from using it thus far, and management of this occurrence
information will be presented as a possible model for use by others.
13
-------
Arsenic Hazardous and Remediation Waste: Sources and Treatment
Linda Fiedler
U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response
Technology Innovation Office
1200 Pennsylvania Avenue, NW(5102G), Washington, DC 20460
T: 703-603-7194; F: 703-603-9135; E: fiedler.linda@epa.gov
Introduction
In 1996 U.S. demand for arsenic was estimated at 22,000 metric tons, making the U.S. the world's largest consumer of
arsenic (USEPA, 2001 a). Most arsenic is used in wood preservatives, but significant use also occurs in agricultural
chemicals, glass production, and metal alloys. These industrial practices, and metals mining and smelting operations,
generate arsenic-bearing waste. In addition, past waste disposal practices have resulted in sites containing arsenic-
contaminated soil, groundwater, and other media that may pose a risk to human health and the environment. Many
additional sites contain naturally-occurring arsenic that may impact drinking water supplies.
Arsenic, especially inorganic forms, is very toxic and a known carcinogen (ATSDR, 1993). The chemical nature of arsenic
compounds, in particular their tendency to change valence or chemical form, makes it difficult to assess their fate and
mobility in the environment, and to immobilize arsenic effectively for ultimate disposal. Even wastes that have been
treated to existing federal standards are found to leach out of landfilled waste (USEPA, 2000d). To support the future
study of these and other arsenic-related issues, this paper presents the current state of arsenic waste generation and
management. It summarizes the sources and estimated quantities of arsenic industrial and remediation wastes, regu-
latory treatment standards, and treatment technologies currently used.
Arsenic Industrial Applications
Arsenic metals and compounds have not been produced domestically since 1986. The U.S. imports arsenic primarily
from China, Chile, and Mexico at about 300 per pound. Of the total 22,000 metric tons of arsenic imported in 1996, almost
20,000 metric tons of arsenic were used in wood preservatives, followed by 1,100 metrictons in agricultural chemicals,
440 metric tons in glass production, and 440 metric tons in metal alloys. The most common wood preservative is
chromated copper arsenate (CCA), used at 88% of wood preserving facilities. Agricultural applications of arsenic com-
pounds include feed additives, animal dips, and herbicides. Arsenic metal is consumed in the manufacture of nonferrous
alloys, principally lead alloys for use in lead-acid batteries. Small amounts are also found in alloys used in other applica-
tions, such as bearings, lead ammunition, and solders. Other uses include electronics and semiconductors, pyrotech-
nics, and antifouling paints (USEPA, 2001 a).
Sources and Quantities of Arsenic Waste
Hazardous Waste
Hazardous waste in the U.S. is regulated under the Resource Conservation and Recovery Act (RCRA). For 29 listed
hazardous wastes, EPA has identified arsenic as a hazardous constituent, or has established a land disposal restriction
(LDR) standard. Arsenic is also a characteristic waste. A hazardous waste exhibits the toxicity characteristic for arsenic
if the arsenic concentration is greaterthan 5 mg/l when analyzed using the Toxicity Characteristic Leaching Procedure
(TCLP). Wastes are listed for arsenic if the arsenic poses a risk; its concentration does not have to exceed 5 mg/l TCLP.
Also, there are often higher-concentration constituents present in the waste.
The EPA Biennial Report System (BRS) contains information reported by hazardous waste large quantity generators, and
by treatment, storage, and disposal (TSD) facilities. An analysis of BRS data submitted for 1997 was conducted forthe
29 hazardous waste codes that can contain arsenic, and for arsenic characteristic waste. Forthis analysis the conserva-
tive assumption was that all of the waste generated in each waste code contained arsenic. In 1997 industry generated a
total of 519 million short tons ofwastewaters (USEPA, 2000b). Of this total, 55 million tons (11%) can contain arsenic.
(One photographic facility accounts for 40 million tons.) The largest generators of arsenic wastewaters are the photo-
graphic (74%), plastics (12%), and organic chemicals (9%) industries. Half of this waste is in the form of multi-source
leachate, which has over 200 regulated constituents, including arsenic. The analysis includes all of the data submitted,
including wastewaters managed in systems that are not RCRA-permitted; these wastes are not included in the national
BRS numbers.
In 1997 industry generated 15 million tons of hazardous nonwastewaters. Of this 4 million tons (27%) can contain arsenic.
The largest generators are organic chemicals (23% of 4 million tons); steel and iron works (20%); aircraft parts/equipment
14
-------
(10%); commercial hazardous waste management (13%); national security (i.e., metals, ammunition, explosives) (10%);
and copper smelting/refining (7%). The most common forms of these wastes are solvent mixtures (27%), ash and slag
(20%), and other waste inorganic solids (12%).
Non-hazardous Waste
The EPA's Toxic Release Inventory (TRI) tracks toxic chemicals manufactured and used at facilities nationally, and
amounts of chemicals released and managed on- and off-site. Both hazardous and nonhazardous waste are reported;
however, RCRA-exempt (i.e., nonhazardous) waste from the metal mining industry accounts forthe vast majority of the
arsenic releases reported. The TRI considers arsenic and arsenic compounds to be metals; only the metal portion of the
metal compound is considered in TRI calculations, and quantities are reported by mass, not volume.
Arsenic wastes are generated from mining and smelting operations, particularly those involving copper, silver, and gold.
Because of the large volume of rock that must be moved as part of the mining operations, even low concentrations of
naturally-occurring arsenic that may be present will yield very large TRI reported quantities. Most of the reported metals
remain in the waste rock that is returned to the land at mine sites or returned underground as backfill. In 1998 the metal
mining industry managed most arsenic waste, over 617 million pounds, or 96% of the total mass of arsenic waste
managed (643 million pounds)(USEPA, 2000c). Gold mining accounts for 93% of the arsenic mining waste, followed by
copper ores (4%) and silver (3%). Lead, zinc, and iron mining wastes, combined, make up less than 1 % of the total.
The other top industries managing arsenic waste are the primary metals industry, 11 million pounds (17% of total arsenic
managed); electric utilities, 7 million pounds (1%); and RCRA/solvent recovery, 6 million pounds (1%).
Remediation Waste
Several cleanup programs manage the remediation of contaminated sites that may contain arsenic, including the Com-
prehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as Superfund), RCRA
corrective action, and the Departments of Energy (DOE) and Defense (DOD). The most detailed data available concern
Superfund sites:
1) Almost half (48%) of the1500 Superfund National Priorities List (NPL) sites have arsenic as a contaminant of
concern that must be addressed. These data are extrapolated from an analysis of 1177 NPL sites with Records of
Decision (RODs) through fiscal year 1998 (USEPA, 2000a). By comparison, lead is of concern at half of NPL sites.
2) For media, 32% of NPL sites have arsenic in groundwater, 32% in soil, and 13% in sediment.
3) Activities at NPL sites with arsenic include wood preserving, municipal and industrial landfills, metal ore mining and
smelting, machine shops, battery recycling/disposal, and pesticide/herbicide manufacturing and use.
In addition, about 5% of 137 DOE installations and other DOE cleanup locations, or about 500 sites, contain arsenic. An
estimated 20% of RCRA facilities contain arsenic in groundwater, and 13% in soil (USEPA, 1996). Data on DOD sites are
not available; however, it is expected that a large number of sites contain arsenic from machine shops, ammunition, and
explosives.
Treatment of Arsenic Waste
The chemical nature of arsenic compounds makes them difficult to treat effectively. Arsenic is a semi-metallic element
and is labile, readily changing chemical form in the environment (and in waste treatment processes). Arsenic mobility
is affected by environmental conditions including acid-base equilibria and overall pH; oxidation-reduction potential and
electron activity; the presence of complexing cations and anions (such as sulfides, calcium, and iron); and adsorption/
desorption reactions. (USEPA, 2001 a)
Arsenic can be readily precipitated from aqueous waste (including As-generated waste and groundwater) if the form of the
arsenic and other waste characteristics are considered. Oxidation of arsenic to its less soluble As+5 state can increase
the effectiveness of precipitation. Ion exchange, carbon adsorption, and membrane filtration are also used. According to
the 1997 BRS, 240,000 tons of aqueous hazardous waste can contain arsenic and are managed offsite. The treatment
methods used are chemical precipitation (31% of the aqueous waste), other aqueous organic treatment (8%), and incin-
eration of solids or liquids (13%) (USEPA, 2000b).
Of the 1.84 million tons of nonaqueous arsenic hazardous waste managed offsite, 400,000 tons (22%) are treated via
stabilization/chemical fixation using cement or pozzolans. Thermal technologies (incineration, energy recovery, or fuel
blending) are used for 36% of the wastes, most likely to address the organic fraction of the waste. An additional 11% are
subjected to recovery technologies (high temperature metals recovery or secondary smelting), but these data do not
indicate whether arsenic is being recovered.
15
-------
EPA tracks the application of cleanup technologies, primarily at Superfund sites (USEPA, 2001 b). Based on this
information, stabilization is the most common technology for disposing of nonaqueous remediation waste containing
arsenic. At least 45 NPL sites are using stabilization to treat arsenic-contaminated soil, sediments, sludge, and other
solids. Cement, lime, and phosphate are the most common stabilization binders used at these sites. Other technolo-
gies used at contaminated sites include: soil washing (6 sites), chemical treatment (4), acid extraction with hydrochloric
acid (2), in situ soil flushing (2), vitrification (3), and electrical separation (1). Chemical treatment agents used include
a combination of ferrous iron/lime/potassium permanganate, oxygenated water with an iron catalyst, and phosphate.
Groundwater contaminated with arsenic usually contains other contaminants, such as chromium or pentachlorophenol,
and other wood treating chemicals. Pump-and-treat is typically used to remediate groundwater at these sites. Data are
available on nine sites applying pump-and-treat for arsenic-contaminated groundwater. Filtration, carbon adsorption, and
chemical precipitation are commonly used to remove both the inorganic and organic groundwater contaminants. A
permeable reactive barrier has been installed at two Superfund sites (Monticello Mine Tailings, UT and Tonolli Site, PA) to
treat groundwater contaminated with arsenic and metals (USEPA, 2001 b; Remediation Technologies Development Forum,
2000).
The RCRA LDRs specify the technologies ortreatment levels that must be achieved priorto land disposal of hazardous
wastes. The LDR treatment standard for arsenic in wastewater is 1.4 mg/l, based on the performance achievable by
chemical precipitation. The standard for nonwastewaters is 5 mg/l as measured bytheTCLP, based on slag vitrification
of wastes up to almost 25% arsenic. Any technology that is not defined as impermissable dilution under RCRA can be
used to achieve these standards. In evaluating arsenic treatment performance, EPA had inconclusive performance data
for stabilization of arsenic in three different wastes using nine different binders. EPA found that the effectiveness of any
particular stabilization binder appeared to be highly dependent upon the waste type (USEPA, 1990). However, based on
the BRSand remediation data, stabilization appears to be the treatment of choice for arsenic in nonaqueous waste, and
the technology can meet the 5 mg/l TCLP standard (USEPA, 2001 a; USEPA, 2000b; USEPA, 2001 b).
References
Agency for Toxic Substances and Disease Registry (ATSDR). 1993. Toxicological Profile for Arsenic.
Remediation Technologies Development Forum. 2000. Permeable Reactive Barrier Site Profiles, .
USEPA. 1990. Office of Solid Waste. LDR, Third Scheduled Wastes, Final Rule. 55 FR 22520. June.
USEPA. 1996. Technology Innovation Office. Cleaning Up the Nation's Waste Sites: Markets and Technology Trends,
1996Edition. EPA-542-R-96-005. .
USEPA. 2000a. Office of Emergency and Remedial Response. CERCLIS3Database. October.
USEPA. 2000b. Office of Solid Waste. BRS: Biennial Reporting System. 1997 Reporting Year, .
USEPA. 2000c. Office of Environmental Information. Toxics Release Inventory. 1998 Reporting Year.
USEPA. 2000d. Office of Solid Waste. LDR Notice of Advanced Rulemaking. 65FR37932. June, .
USEPA. 2001a. Office of Solid Waste. Profile of Arsenic Waste Generation and Treatment. Draft. January.
USEPA. 2001 b. Technology Innovation Office. Treatment Technologies for Site Cleanup: Annual Status Report (Tenth
Edition). EPA542-R-01-004. .
16
-------
Treatment Options for Arsenic Wastes
Godage B. Wickramanayake, Ph.D., P.E., Senior Program Manager
Battelle
505 King Avenue, Columbus, OH 43201
T: 614-424-4698, F: 614-424-3667, E: wickram@.battelle.org
Kim Cizerle, M.S., Manager
ENVIRON International Corporation
202 Carnegie Center, Princeton, NJ 08540
T: 609-243-9858, F: 609-243-0321
Wendy Condit, M.S., Environmental Engineer
Battelle
505 King Avenue, Columbus, OH 43201
T: 614-424-4698, F: 614-424-3667, E: conditw@battelle.ora
Since recycling of arsenic-containing materials is technically challenging and cost prohibitive, there is a great demand for
the development of effective treatment technologies for the safe disposal of arsenic-contaminated hazardous wastes.
The industrial use of arsenic has been curtailed in recent times; however, historic operations have led to significant
contamination at some industrial sites where arsenic compounds were previously used to produce pesticides, herbicides,
orveterinary Pharmaceuticals. Current uses of arsenic are more limited and include the use of chromated copperarsen-
ate for wood-preserving operations and the use of gallium arsenide in the development of semiconductor material forthe
electronics industry. In addition, mining operations often involve the smelting of ores with high arsenic concentrations.
Currently, arsenic contaminated hazardous wastes are subjectto land disposal restrictions underthe Resource Conser-
vation and Recovery Act (RCRA) and must be treated to meettoxicity characteristic leaching procedure (TCLP) limits. A
RCRA hazardous waste is defined as a waste that produces an extract containing more than 100 times the maximum
contaminant level (MCL) in drinking water for that specific chemical. The MCL for arsenic (50 ^g/L) was recently sub-
jected to critical review due to concerns about a potential association between long-term exposure to arsenic and serious
health problems such as skin and internal cancers and cardiovascular and neurological effects. As a result of these
concerns, and after further review of the relevant scientific data by the U.S. Environmental Protection Agency (EPA), a
change in the arsenic MCL from 50 to 10 ^g/L was promulgated.
Due to these potential changes, there is a need to investigate the impact that a revised rule would have on the treatment
and disposal of arsenic-contaminated hazardous wastes underthe RCRA program. This presentation assumes that, if
EPA changes the TCLP regulatory level, it would also change the required treatment standard (40 CFR 268.40 and 268.48)
to a value that is at or below the TCLP regulatory level. It is important to perform an assessment of whether or not the
current array of treatment options, both innovative and conventional, will be able to achieve the potentially more stringent
treatment requirements.
Due to the existence of alternate treatment standards for soils (40 CFR 268.49), the potential changes to the TCLP limit
should not have a major effect on the treatment and disposal of arsenic-contaminated soils. However, the potential
changes would alter the treatment cap for soils and the definition of RCRA hazardous waste for arsenic (D004). With
these changes, more soils would be considered hazardous than at the current TCLP regulatory level. The existing
alternate treatment standards for soil should minimize the impact of any MCL or TCLP revisions. In setting the alternate
treatment standards, EPA already reviewed and compiled treatability data to determine cost-effectively achievable treat-
ment goals for arsenic-contaminated soils. Thus, this presentation focuses primarily on arsenic-contaminated wastes,
but will briefly review recent innovations in soil treatment technologies.
As an inorganic constituent, arsenic cannot be destroyed, but it can be converted into less soluble or leachable forms to
inhibit migration into the environment and subsequent exposure by sensitive receptors. Vitrification was selected by EPA
as the Best Demonstrated Achievable Technology (BOAT) for characteristic and listed wastes containing arsenic including
D004, K031, K084, K101, K102, P10-12, P36, P38, and U36. Vitrification involves the use of a plasma torch, an electrical
current, or other heat source to melt the contaminated material into a glass matrix at extremely high temperatures ranging
from 2,900 to 3,650°F. The vitrified material is non-porous, has a high strength, and is much more resistant to leaching
than the original feed materials. Although vitrification, as BOAT, would be considered the "conventional" approach to
17
-------
treatment, it is not widely used and has been selected as a treatment option for arsenic-contaminated waste at only one
out of twelve Superfund sites identified. The remaining sites with arsenic-impacted soil or other wastes had Record of
Decision (ROD) selected remedies that included solidification/stabilization (6), containment/capping (4), and soil washing
(1). Vitrification is not used extensively for the following reasons: 1) the cost is prohibitive since the process requires
complex, capital-intensive equipment; 2) wastes with elevated moisture content, high metal content, and/or inappropriate
physical characteristics maybe more expensive or difficult to treat; and 3) significant volatile losses of arsenic can occur
unless the waste is properly pre-treated to produce less volatile forms of arsenic.
There are several other treatment options for arsenic-contaminated wastes, including the most commonly applied tech-
nology, solidification/stabilization (S/S) with cement, fly ash, sodium silicates, or other binders. S/S relies upon mobility
reduction, resulting from a combination of physical entrapment (e.g., encapsulation) and chemical reaction (e.g., precipi-
tation) mechanisms. Cement, silicate, and other S/S binder materials were evaluated by EPA, but not accepted as BOAT
for arsenic wastes due to concerns about long-term stability and waste volume increases. However, EPA did not preclude
the use of S/S methods for the treatment of arsenic wastes, but instead recommended site-specific treatability studies.
Several studies have demonstrated that S/S can be successfully implemented forthe treatment of arsenic-contaminated
wastes, if pre-treatment methods are employed first to transform arsenic into the appropriate oxidation stage or species
and then to decrease the solubility or availability of the arsenic compounds in the solid matrix prior to binding. The
following is a list of alternate or innovative treatment technologies that can be applied to treat arsenic-contaminated
hazardous wastes:
1. S/S with pretreatment by oxidation using hydrogen peroxide, potassium permanganate, and others
2. S/S with pretreatment by hydrated salt addition including ferric sulfate, ferrous sulfate, ferric chloride, and others
3. S/S with proprietary formulations
4. Slag incorporation
5. Encapsulation with polymer resins
The advantages and limitations of the above technologies will be discussed and their ability to meet potential revisions to
the hazardous waste treatment standard will be evaluated in light of available literature and Battelle and ENVIRON's
project experience.
Treatability study results for K084 and D004 wastes will be discussed based on a case study from a veterinary pharma-
ceutical Superfund site. The waste consisted of iron-arsenic sludge and sludge generated from arsenic precipitated with
lime. As part of the ROD selected remedy, an estimated 3,800 tons of these arsenic wastes, containing up to 260,000
mg/kg of arsenic, were removed and treated off-site with S/S before disposal at a RCRA Subtitle C landfill. The treatability
study tested a total of 88 mixture designs to determine an effective method of treating the vault wastes. Table 1 lists the
types of binders and pretreatment additives that were tested.
Table 1. List of Solidification/Stabilization Treatability Study Materials
Binders
Type I, II, V Portland Cements
Class F Fly Ash
Cement Kiln Dust
Lime Kiln Dust
Sodium Silicate
HWT-25, Organophillic Clay With Additives
pH Control Additives
Sulfuricacid
Phosphoric acid
Buffer solution
Other Pre-Treatment Additives
Potassium permanganate (oxidation)
Hydrogen peroxide (oxidation)
Calcium hypochlorite (oxidation)
Potassium persulfate (oxidation)
Sodium persulfate (oxidation)
Calcium chloride (precipitation)
Ferric chloride (precipitation)
Ferric sulfate (precipitation)
Ferrous sulfate (precipitation)
Magnesium oxide (adsorbent)
Activated carbon (adsorbent)
18
-------
The final formulation arrived at during the treatability study involved pretreatment with potassium persulfate and ferric
sulfate, followed by binding with Type I Portland cement. Initial TCLP levels in the untreated waste were up to 6,900 mg/
L for arsenic; post-treatment TCLP results with the final optimized formula ranged from 0.67 to 1.9 mg/L for arsenic. The
full-scale system used a similar formulation with the substitution of sodium persulfate for oxidation of arsenic from As(l II)
to the less soluble and less toxic As(V) form. The final TCLP results from the full-scale system were 1.24 to 3.44 mg/L.
The full-scale system experienced several challenges that were not anticipated based on the bench-scale studies includ-
ing excessive heat production during mixing. The total cost for off-site S/S treatment and disposal of the arsenic-impacted
vault wastes was over $900 per ton. The cost for S/S treatment alone was approximately $800 per ton.
Other arsenic-contaminated materials on-site included K101 or distillation tar residues and K102 or activated carbon
residues. These materials contained a high enough organic content that incineration was determined to be the appropriate
treatment method. The treatment and disposal cost for the 455 tons of K101 and K102 wastes was approximately $2,000
per ton.
These data show the difficulties in treating high-strength arsenic wastes and excessive treatment costs. It will be
necessary to understand whether the high treatment costs can be justified by the incremental reduction in potential risk
associated with arsenic in treated wastes.
19
-------
Some Chemical Aspects Relating to Arsenic Remedial Technologies
Robert G. Robins
AquaMin Science Consortium International
25 Adelaide Avenue, Lindfield NSW 2070, Australia
T/F: +61 294163928, E: bobrobins@.bigpond.com.au
The information that is summarized here originates mostly from publications by well-known and established authors in the
field, during their many years of research on this subject. Most of the material is mentioned only briefly, but is found in a
publications list, which is available by e-mail from the author. Although there are many other excellent relevant references,
the author has chosen the selected papers fortheir reliability and convenience, but they are not necessarily the earliest
chronological references. There are many other statements here which originate from much unpublished work. This ex-
tended abstract is an abridged version of the paper (with the references) that is available by e-mail.
Introduction
The removal of arsenic from process solutions and effluents has been practiced by the mineral process industries for
many years. Existing hydrometallurgical techniques are adequate for most present day product specifications, but the
stability of solid and liquid waste materials for long-term disposal or discharge will not meet the regulatory requirements of
the future. The removal and disposal of arsenic from metallurgical process and effluent streams will become a greater
problem as minerals with much higher arsenic content are processed in the future, and as regulations become more
stringent. Disposal of stable residues will be critical, and the testing methods for assessing stability will need thorough
revision.
The various unit processes that have been considered to deal with arsenic in hydrometallurgical processes include:
oxidation-reduction, precipitation and thermal precipitation, coprecipitation, adsorption, electrolysis and cementation,
solvent extraction, ion exchange, membrane separations, precipitate and ion flotation, and biological processing. These
methods are not considered here, but are detailed in some of the references in the e-mail version of this paper. Here only
precipitation, adsorption and cementation are considered, as these are the processes that are presently being more
generally adopted and need further investigation.
The aqueous solution chemistry of arsenic and the most common hydrometallurgical methods that have been applied
commercially for arsenic removal, recovery, and disposal are only mentioned briefly here, as are some techniques which
have been used only in the laboratory, and otherwise suggested as a means of eliminating or recovering arsenic from
solution.
The aqueous solution chemistry of arsenic that relates to hydrometallurgical processes has been extensively covered in
the literature, and the use of thermodynamic stability diagrams to describe the chemistry has been widely adopted. The
important oxidation states of arsenic are-3, 0, +3, and+5, and all have been utilized in some way in hydrometallurgy. The
removal of arsenic from solution has relied mostly on precipitation and adsorption processes, and it has been considered
that arsenic(V) is the oxidation state that leads to the most effective removal by precipitation since the simple metal
arsenates generally have lower solubility than the arsenites, and also arsenate is more strongly adsorbed on certain
substrates, but this is pH dependent. The general assumption that arsenic(V) is more easily removed from solution, even
by adsorption, is not correct. Current work has identified other compounds and also the element (formed by either
cementation or electrolysis) to be appropriate low solubility materials for effective removal of arsenic from solution.
Arsenic complexation in solution has had little attention, and it seems that only complexes of arsenic(V) with iron(lll) have
been studied to any extent. Oxidation of arsenic(lll) in solution to arsenic(V), and reduction of arsenic(V)to arsenic(lll)
have been investigated as part of the overall chemistry relating to hydrometallurgy. Oxidants such as air and oxygen,
chlorine and hypochlorite, hydrogen peroxide, permanganate, ozone, and SO2/O2 have been investigated, both with and
without catalysts. Photochemical oxidation of arsenic (III) to arsenic(V) is a recent innovation. The removal of arsenic
from gold process solutions has been of understandable interest over the years, and has perhaps been investigated more
than other hydrometallurgical processes.
Precipitation
The insolubility of certain inorganic arsenic(V) compounds is the basis of many hydrometallurgical arsenic removal
processes, and the insoluble product is often a disposal material. The most common methods of removing arsenic from
aqueous process streams are by precipitation as arsenic(lll) sulfide, calcium arsenate, or ferric arsenate, but it has been
20
-------
shown that all of these materials are unstable under certain conditions and therefore not suitable for direct disposal to
uncontained sites as they will produce leachate containing arsenic.
The sulfide As2S3 has its lowest solubility below pH=4, but that solubility is significantly higher than has been generally
accepted. The sulfide is not usually the form that is disposed in residues as it is easily oxidized and increasingly soluble
above pH=4. There have been unsuccessful attempts to use As2S3 in landfills in which acidic-anaerobic conditions are
maintained, and also in cement cast admixes. Recent work on biological formation of arsenic sulfides may have an
application in treating process residues, but containment of waste material remains a problem.
There are a number of calcium arsenates that can be precipitated from arsenic(V) solutions by lime addition to high pH.
Lime addition in excess can reduce arsenic concentrations in solution to <0.01 mg/L, but those calcium arsenates which
are precipitated at pH>8 are not stable with respect to the CO2 in the atmosphere which converts them into calcium
carbonate, releasing arsenic to solution in balance with appropriate cations.
Arsenic(V) can be precipitated from aqueous solutions below about pH=2 with iron(lll) to form ferric arsenate, FeAsO4.2H2O,
which is white to very pale green in colour. At ambient precipitation temperatures the compound is very small in crystal
particle size (<10nm) and is "2-Line X-ray amorphous," but these particles tend to agglomerate to about 100nmandthe
material is difficult to de-water by conventional operations. At temperatures above about 90°C the precipitated compound
is crystalline (>1 OOnm) and has a solubility about 2 orders of magnitude lower than the amorphous material (this is a
particle size effect). The "amorphous" ferric arsenate exhibits incongruent solubility at about pH=1 (where [As] is about
500 mg/L) and at higher pH will convert very slowly to an arsenic bearing ferrioxyhydroxide, which initially forms around
the surfaces of the ferric arsenate tending to stabilize the material and colouring it yellow to brown. Crystalline ferric
arsenate (scorocf/fe) has an incongruent solubility point at about pH=2 and is comparatively slow to convert to the arsenic
bearing ferrioxyhydroxide, and for material of larger crystal particle size this may take some years. Crystals of FeAsO4.2H2O
do not grow to appreciable size (greater than about 1 mm) as they have a relatively high positive surface potential up to
the pH of the incongruent point. Ferric arsenate of either form is not thermodynamically stable in the neutral to high pH
region (the rate of decomposition being related to particle size and solution composition, and being controlled by diffusion
through both the reactants and the product layer). The materials may pass conventional leach tests (such as the TCLP)
and are not suited for direct uncontained disposal, but perhaps would satisfy a "slow release criteria" if regulatory
authorities would give this option its deserved consideration. Ferric arsenate is also not stable in alkaline cement cast
admixes.
There are other metal arsenates, such as those of Fe(ll), Zn(ll), Cu(ll) and Pb(ll), which are less soluble and more stable
in the neutral pH region than the calcium arsenates or ferric arsenate, but these have not been seriously considered as
disposal forms. lron(lI) arsenate has particular interest as a low solubility material, and this compound has recently been
the basis of a process developed and successfully demonstrated in a variety of applications. Barium(ll) arsenate was
proposed as being an extremely insoluble arsenate, but this was shown to be incorrect. More complex compounds, such
as the apatite structured calcium phosphate-arsenate have recently been demonstrated to be of low solubility and of
appropriate stability (including being stable to atmospheric CO2) for disposal considerations. Ferric arsenite sulfate is also
of recent interest and may prove to be useful in stabilizing arsenic(lll). One of the most insoluble arsenic compounds is
lead(ll) chloroarsenate, Pb5(AsO4)3CI, (the mineral form being mimetite) which has been studied in detail.
Very little attention has been given to mixed oxidation state materials (both Fe(ll)-Fe(lll) and As(lll)-As(V) combination
compounds have been tentatively identified, and the author is presently involved in a comprehensive study of these
systems). The Fe(ll)-Fe(lll) hydroxy sulfate, Fe"4Fem2(OH)12SO4.8H2O, (known as "green rust") incorporates arsenic into
the structure atpH<7, and is worthy of further study.
Adsorption of Arsenic on Ferrihydrite
Over many years there has been much attention directed to the removal of arsenic from hydrometallurgical process
solutions and waste waters by precipitation and coprecipitation with iron(lll). At relatively high concentrations of iron(lll)
and arsenic(V) (> about 0.001 m) and at low pH, the precipitation results in the formation of ferric arsenate, FeAsO4.2H2O,
as previously mentioned. At lower concentrations of arsenic(V) and higher iron(lll) concentrations (where Fe/As>1), the
coprecipitation of arsenic with ferrioxyhydroxide (ferrihydritf!) which occurs is probably the most effective method of
removal of arsenic from aqueous solutions, and leads to a solid phase which can be stable at least for a year or so. The
solid coprecipitate has been referred to as "basic ferric arsenate,"and in 1985 a controversy commenced, as to whether
the coprecipitated material was in fact a compound of iron(lll) and arsenic(V) orsimply an adsorptive binding of arsenic
withferrioxyhydroxide(/£/r/#yo57fe). There was even at that stage sufficient evidence to support the latter contention, but
the use of the term "basic ferric arsenate" still exists and formulae such as "FeAsO xFe(OH) " are used.
21
-------
A number of studies have indicated that various complexes are formed in the adsorption of As(V) on ferrihydrite.
EXAFS studies on arsenic bearing ferrihydrite formed at pH>7, have shown that arsenic(V) is adsorbed to ferrihydrite
as a strongly bonded inner-sphere complex with either monodentate or bidentate attachment. It has also been re-
ported that monodentate attachment predominates near the optimal pH=4-5 for adsorption.
The adsorption of arsenic(lll) on ferrihydrite has also been investigated, but the optimal adsorption in this case occurs at
pH 8-9, and although it seems an efficient process, there is no evidence that the adsorbed species is infactarsenic(lll).
It may be that during the process, oxidation of arsenic(lll) will occur at the surface with some ease, being balanced by the
reduction of Fe(lll)to Fe(ll) in the ferrihydrite structure, as has been shown in preliminary experiments by the author. It is
well known that Fe(ll) substitution in ferrihydrite does occur. Currently there is an investigation of the adsorption ofAs(lll)-
As(V) mixtures on ferrihydrite. Very little attention has been given to the possibility of modifying the ferrihydrite structure
to improve its adsorptive capacity for arsenic in solution. It is well known that many cations will incorporate into the
goethite structure, and therefore possibly into a precursor ferrihydrite. The author is aware of current work investigating
the coprecipitation of both Al(lll) and Mn(lll) with Fe(lll) to form an aluminic ferrihydrite and a manganic ferrihydrite
respectively. Both materials are showing considerably better capacity for arsenic adsorption. The control of potential is
important in this adsorption process. The effective oxidation of As(lll) by manganese substituted goethite has been
studied by XANES spectroscopy, and the implications are obvious in relation to adsorption mechanisms. There is little
work reported on the adsorption of arsenic from solutions initially below say 50 ^g/kg. This region of concentration is
presently of immediate interest in relation to drinking water, where EPA announced a new standard of 10 ppb (10 ^ig/L)
forthe maximum level allowed.
Many substrates, otherthan ferrioxyhydroxide, have been investigated and used commercially for removing arsenic from
solution by adsorption. Some of these have shown excellent adsorptive capacity, but there is not the scope here for any
details. Of personal interest is "adsorption" on sulfide minerals and titanium oxyhydroxide.
Cementation
It is well known that iron and other metals will replace arsenic from solution to produce arsenic as the element or as an
alloy. This method of removing arsenic from solution to levels <2 ^g/L has been demonstrated on groundwater at a
commercial site in California at a pilot scale of 1-5 US gallons per minute. Cementation has also been suggested,
demonstrated, and may be appropriate forthe removal of arsenic from drinking water.
Testing for Long Term Stability
Testing methods for evaluating the stability of hazardous waste residues have been defined by EPA in several "Back-
ground Document forToxicity Characteristic Leaching Procedure" publications. The test methods do not adequately
assess the long term stability of arsenical residues. Improved test methods must be designed which also include a
characterization of physical properties and chemical components (mineralogy) so that predictions of behavior can be
made.
Thermodynamic Modeling
The stability of arsenic species can be characterized by their standard free energies of formation (AfG°). Many of the
papers referenced in the e-mail version of this paper have free energy of formation data for arsenic species that have
been invaluable to the author in producing thermodynamic stability diagrams to gain a better understanding of arsenic
systems. None of the reputable thermodynamic databases have significant relevant data, but there are a number of
publications where reasonable data can be obtained, and it is likely that these data will be evaluated and a compilation
produced in the near future.
Conclusions
There have not been any significant and innovative improvements in the methods for removing arsenic from process and
effluent solutions, or for stabilizing sludges and residues, in the last decade or so. The current need to remove arsenic
from drinking water it seems is now a world problem, and so that too must be addressed.
References
This paper is available with references from bobrobins@bigpond.com.au.
22
-------
Arsenic Geochemistry: Overview of an Underhanded Element
D. Kirk Nordstrom
U.S. Geological Survey
3215 Marine St., Boulder, CO 80303
T: 303-541-3037, F: 303-447-2505, E: dkn@usgs.gov
Arsenic is 38th in cosmic abundance but only about 52nd in earth and crustal abundance. The formation of the earth
apparently discriminated against arsenic. In the ocean, however, it is 26th in abundance, suggesting accumulation in
seawater over geologic time. Arsenic is preferentially concentrated in shales relative to other major rock types. Partition-
ing into shales reflects the strong adsorption tendency of arsenic for clay minerals. During high-temperature processes,
arsenic can be expelled from sediments and volcanics and concentrated in the fluid phase, especially at low porosity.
This phenomenon may explain high arsenic in hydrothermal fluids and their ore deposits.
The geochemical cycle of arsenic from magmatic-hydrothermal processes through weathering, sedimentation, and di-
agenesis transforms the element and produces an array of natural sources. Probably the single most abundant mineral
source of arsenic is arsenian pyrite. Pyrite is ubiquitous in the earth's crust and arsenic has a strong affinity forthe sulfur
site in pyrite, substituting up to about 10wt. %. Arsenopyrite contains higher concentrations of arsenic (39-53%) but is a
much rarer mineral. Other arsenic-rich minerals include orpiment, realgar, and enargite. Weathering of these minerals in
oxidizing environments solubilizes arsenic as As(lll) and ultimately as As(V). Arsenate, orAs(V), has a strong adsorp-
tion affinity for hydrated iron oxides and in oxidized sediments iron oxides can be a source of soluble arsenic if they
undergo reductive dissolution during early diagenesis. Geothermal springs are commonly enriched in arsenic, contain-
ing 0.1-5 mg/L dissolved arsenic as bothAs(lll) and As(V).
Arsenic concentrations ingroundwaterscan range from less than a few ^ig/L to tens or even hundreds of mg/L in locally
contaminated environments. Both anthropogenic and natural sources for arsenic in groundwaters occur in many loca-
tions worldwide. Natural sources cause or have caused poisoning of populations in India, Bangladesh, Chile, Argentina,
Mexico, Taiwan, Mongolia, Japan, and China. Mining activities are responsible for arsenic poisoning in Thailand. Arsenic
mass poisoning in Bangladesh is the largest known, affecting nearly 30 million people.
The primary source of industrial and commercial arsenic was arsenictrioxide, produced as a by-product of metal mining
and processing. Stockpiles still exist and are releasing soluble arsenic to groundwaters. Several arsenic insecticides,
herbicides, desiccants, wood preservatives, animal feed additives, drugs, chemical weapons, and alloys were produced
for many years and sites are contaminated from these industries and their applications. Roxarsone, an organic arsenical,
is still widely used today to clean parasites out of the stomachs of pigs and poultry.
Arsenic in surface and groundwaters occur dominantly as either arsenite, As(lll), or arsenate, As(V). Reduction of
arsenic can produce methylated forms of arsenic. Several microorganisms, including species of fungi, algae, and bacte-
ria, catalyze the reduction of arsenic. Oxidation of As(lll) is also catalyzed by microbes and it has been demonstrated
that soluble As(lll) and arsenic sulfide minerals such as arsenopyrite and orpiment can be catalytically oxidized to soluble
As(V).
23
-------
Impact of Microorganisms on Arsenic Geochemistry
DianneAhmann
Division of Environmental Science and Engineering, Colorado School of Mines
Golden, CO 80401
T: 303-273-3402, F: 303-273-3413, E: dianne@mines.edu
Introduction
Microbial activities are ubiquitous in the geochemical environment, and they can exert tremendous influences on the
biogeochemical cycles of elements by interconverting species that display remarkably different behaviors. Arsenic is one
such element, possessing a multi-dimensional biogeochemical cycle with important components contributed both di-
rectly, by microbial transformations of arsenic itself, and indirectly, by microbial transformations of elements with bio-
geochemical cycles that intersect that of arsenic.
Microbial Energy Generation by Catalyzing Redox Reactions
One of the primary tasks of a microorganism is to catalyze chemical reactions that will help it to obtain energy for
metabolic growth from its environment, and as a result, many of the biogeochemically significant transformations that
microorganisms catalyze are the result of energy-generating endeavors. The greatest energy-generating reactions avail-
able to the biosphere are those in which electrons are transferred from one element or compound to another, also known
as oxidation-reduction or "redox" reactions (Stumm and Morgan, 1996). Redox reactions necessarily alter the electronic
configurations of the compounds involved, and because electronic associations form the basis for much chemical reac-
tivity, redox reactions frequently create dramatic alterations in the behaviors of their substrates (Schlesinger, 1997). In
addition, because the microbial incentive to catalyze energy-generating reactions is so great, and because the abiotic
rates of redox reactions are frequently so slow, such reactions frequently proceed much more rapidly and to a much
greater extent in the presence of microbial catalysis than they would otherwise (Morel etal., 1993).
Aerobic and Anaerobic Respiration
Microorganisms catalyze redox reactions by means of "respiratory" processes, which are those that catalyze the transfer
of electrons from one reactant to another. Aerobic respirations couple the oxidation of an electron donor such as organic
carbon, H2, or Fe(ll) to the reduction of molecular oxygen, O2, forming water. These processes necessarily occur in
unsaturated soils or well-mixed or oligotrophic surface waters where oxygen is abundant (Brock and Madigan, 1991). In
contrast, anaerobic respirations couple the oxidation of an electron donor to the reduction of an alternative electron
acceptor such as nitrate, Fe(lll), orsulfate, generating N2, Fe(ll), orsulfide, for example (Zehnderand Stumm, 1988).
Aerobic and anaerobic respiratory processes form one central class of processes that strongly influences arsenic bio-
geochemistry, both directly and indirectly.
Respiratory Arsenic Transformations
Within the past seven years, microorganisms have been discovered in a great diversity of anoxic environments that are
able to generate energy by coupling the oxidation of H2 or organic carbon to the reduction of inorganic As(V), arsenate,
forming inorganic As(lll), arsenite (Ahmann et al., 1994; Cummings et al., 1999; Dowdle et al., 1996; Laverman et al.,
1995; Macyetal., 1996; Newman etal., 1997; Newman etal., 1998). Arsenite behaves much differently than arsenate in
natural environments; in particular, its sorption onto clay minerals and metal oxides appears to be less rapid and/or less
stable, with the result that As(l 11) is generally much more mobile than As(V) in aqueous systems (Aggettand Kriegman,
1988; Kuhn and Sigg, 1993; Masscheleyn et al., 1991; Mok and Wai, 1994; Onken and Adriano, 1997; Seyler and Martin,
1989; Seyler and Martin, 1990; Spliethoff et al., 1995).
Because arsenate reduction is an energy-generating process forthe microorganisms involved, and because arsenite is
both more toxic and more mobile than arsenate, this process has the potential to influence greatly the geochemistry of
arsenic in anoxic systems, particularly with respect to arsenic mobilization (Ahmann etal., 1997; Cummings etal., 1999).
The converse respiratory process, the oxidation of arsenite to arsenate, coupled to the reduction of O2 to water, has the
theoretical potential to generate energy for microbial growth, but has been indicated in only one microorganism to date
24
-------
(llyaletdinov and Abdrashitova, 1981). Nevertheless, a variety of other microorganisms have been shown to oxidize
arsenite to arsenate by non-energy-generating mechanisms (Osborne and Ehrlich, 1976; Phillips and Taylor, 1976; Sehlin
and Lindstrom, 1992; Wilkie and Hering, 1998).
Respiratory Iron, Manganese, and Sulfur Transformations
Sorption onto iron and manganese oxide solids and precipitation in sulfide solids in anoxic environments appearto be the
two primary mechanisms governing arsenic mobility in aqueous, soil, and sedimentary environments (Bodek et al., 1988;
Sadiq, 1997). Consequently, microbial activities that affect the abundances of iron or manganese oxides or sulfides have
indirect, but potentially very important, influences on arsenic geochemistry. Respiratory iron and manganese reduction
are ubiquitous and, in many cases, dominant redox processes in anoxic soils and sediments (Lovley, 1993; Nealson and
Saffarini, 1994). Because the reduced forms of iron and manganese are highly soluble, their oxides dissolve readily upon
microbial reduction, simultaneously releasing sorbed substances such as arsenic (Commingsetal., 1999). When suffi-
cient sulfate is present in an anoxic region, however, microbial sulfate reduction can potentially generate sufficient sulfide
to precipitate the arsenic in solids such as amorphous arsenic sulfide, realgar, or orpiment (Moore et al., 1988). The
corresponding oxidative processes, microbial oxidation of Fe(ll), Mn(ll), or S(-ll), are known to occur, but are usually
restricted to acidic environments (Schlegel, 1993) and have not been shown directly to promote arsenic sorption onto
metal oxides norto promote arsenic sulfide dissolution. While the geochemical significance of the reductive processes
for arsenic cycling is well-established, the significance of the oxidative pathways is much less understood.
Arsenic Toxicity
In addition to energy generation, a second important task for microorganisms is to protect themselves from toxic sub-
stances. Arsenate, with its structural similarity to phosphate, enters microbial cells readily through phosphate-uptake
proteins. Its primary mode of toxicity is then to displace phosphate in the production of adenosine triphosphate (ATP), the
primary energy currency of the cell. The resulting molecules hydrolyze spontaneously, causing the cell to deplete its
energy stores rapidly (Winship, 1984). Although this mechanism of toxicity is quite effective, many cells are able to
induce highly phosphate-specific uptake proteins that improve the exclusion of arsenate (Rosenberg et al., 1977; Torriani,
1990; Willsky and Malamy, 1980). Arsenite, in contrast, is uncharged at neutral pH and appears to gain access to the
cytoplasm by less specific mechanisms, possibly including diffusion across the membrane. Once inside, it crosslinks
sulfhydryl groups on enzymes, forming stable adducts that permanently disable the enzyme. This mechanism is even
more destructive to the cell than that of arsenate (Winship, 1984).
Arsenic Detoxification
To protect themselves against the toxic effects of arsenic, many microorganisms have evolved strategies for detoxifica-
tion. The best-studied among these is the microbial reduction of arsenate to arsenite by means of the Ars system, an
enzymatic process in which energy is actually consumed to drive the reduction. The /4/ssystem is borne on plasmids
that are easily transferred among both Gram-positive and Gram-negative bacteria, and it is induced at arsenic concentra-
tions low enough to be relevant to contaminated environments, with the result that this process is potentially rapid,
extensive, and ubiquitous in both oxicand anoxic environments (Ji and Silver, 1995; Silver etal., 1993).
Certain other bacteria and fungi appear to detoxify arsenicals by reducing them to arsine, As(-lll), in both inorganic and
methylated forms (Cheng and Focht, 1979;Cullen and Reimer, 1989). In addition, some algae have been shown to reduce
arsenate to arsenite, presumably for detoxification purposes, but this purpose has not been confirmed (Sanders and
Windom, 1980). Finally, certain bacteria and algae, as well as many higher organisms, may incorporate arsenic into
organic compounds such as arsenocholine, arsenobetaine, and other arsenosugars(Andreae and Klumpp, 1979; Cullen
and Reimer, 1989). Regardless of the utility to the microorganism, however, it is clearthat many non-energy-generating
microbial transformations of arsenic occur both rapidly and extensively in natural environments, and should be consid-
ered potentially important contributors to arsenic geochemistry.
Passive Nucleation
Microbial cell surfaces possess an abundance of surface functional groups that can form complexes with dissolved ions,
including arsenic oxyanions, and such complexes have been shown to function as sites of nucleation in the precipitation
of certain minerals (Beveridge, 1989). In the case of arsenic, it may be possible that microbial cell surfaces contribute to
arsenic geochemical cycling in this passive manner as well, particularly in the instance of nucleating arsenic sulfide
precipitation (Newman etal., 1997; Rittleetal. 1995).
25
-------
Summary
In oxic environments, the dominant microbial influences on arsenic geochemistry appear to be the bacterial and algal
oxidations of arsenite to arsenate, diminishing both toxicity and mobility of the arsenic, as well as confirmed detoxifica-
tion processes, including the /4/s-mediated reduction of arsenate to arsenite and fungal generation of arsines. In anoxic
environments, in contrast, the dominant microbial roles are expected to be the respiratory reductions of arsenate, iron,
and manganese, all of which promote arsenic desorption and enhance its mobility, and the respiratory reduction of sulfate,
which promotes arsenic immobilization into sulfide solids. While the mechanisms underlying these processes are well
understood in many cases, and their geochemical influences are potentially great, the ability to quantify and, more
importantly, to predict the rates and extents of these processes in natural environments, remains a tremendous challenge
for the future.
References
Aggett, J., and M. R. Kriegman. 1988. The extent of formation ofarsenic(lll) in sediment interstitial waters and its release
to hypolimnetic waters in Lake Ohakuri. Water Res. 22:407-411.
Ahmann, D., L. R. Krumholz, H. F. Hemond, D. R. Lovley, and F. M. M. Morel. 1997. Microbial mobilization of arsenic from
sediments of the Aberjona Watershed. Environ. Sci. Technol. 31:2923-2930.
Ahmann, D.,A. L. Roberts, L. R. Krumholz, and F. M. M. Morel. 1994. Microbe grows by reducing arsenic. Nature 351:750.
Andreae, M. O., and D. Klumpp. 1979. Biosynthesis and release of organoarsenic compounds by marine algae. Environ.
Sci. Technol. 13:738-741.
Beveridge,T. J. 1989. Role of cellulardesign in bacterial metal accumulation and mineralization. Annual Review of Micro
biology 43:147-171.
Bodek, I., W J. Lyman, W F. Reehl, and D. H. Rosenblatt (eds.). 1988. Environmental inorganic chemistry: properties,
processes, and estimation methods. Pergamon Press, Inc., Elmsford, NY.
Brock, T. D., and M.T. Madigan. 1991. Biology of microorganisms, 6th ed. Prentice Hall, Englewood Cliffs, NJ.
Cheng, C.-N., and D. Focht. 1979. Production of arsine and methylarsines in soil and in culture. Appl. Environ. Microbiol.
38:494-498.
Cullen, W. R., and K. J. Reimer. 1989. Arsenicspeciation in the environment. Chem. Rev. 89:713-764.
Cummings, D. E., F. Caccavo Jr., S. Fendorf, and R. F. Rosenzweig. 1999. Arsenic mobilization bythe dissimilatory
Fe(lll)-reducing bacterium Shewane/faa/gaBfY. Environmental Science and Technology 33:723-729.
Dowdle, P., A. Laverman, and R. Oremland. 1996. Bacterial dissimilatory reduction ofarsenic(V)toarsenic(lll) in anoxic
sediments. Appl. Environ. Microbiol. 62:1664-1669.
llyaletdinov, A. N., and S. A. Abdrashitova. 1981. Autotrophic oxidation of arsenic by a culture of Pseudomonas
arsenitoxidans. Mikrobiologiya 50:197-204.
Ji, G., and S. Silver. 1995. Bacterial resistance mechanisms for heavy metals of environmental concern. J. Indust.
Microbiol. 14:61-75.
Kuhn, A., and L. Sigg. 1993. Arsenic cycling in eutrophicLakeGreifen, Switzerland: influence of seasonal redoxpro
cesses. Limnol. Oceanogr. 38:1052-1059.
Laverman, A. M., J. S. Blum, J. K. Schaefer, E. J. P. Phillips, D. R. Lovley, and R. S. Oremland. 1995. Growth of strain
SES-3 with arsenate and otherdiverse electron acceptors. Appl. Environ. Microbiol. 61:3556-3561.
Lovley, D. R. 1993. Dissimilatory metal reduction. Annu. Rev. Microbiol. 47:263-290.
26
-------
Macy, J., K. Nunan, K. Hagen, D. Dixon, P. Harbour, M. Cahill, and L. Sly. 1996. ChrysiogenesarsenatisQen. nov., sp. nov.,
a new arsenate-respiring bacterium isolated from gold minewastewater. Int. J. Syst. Bacteriol. 46:1153-1157.
Masscheleyn, P., R. Delaune,and J. Patrick, W. 1991. Effect of redox potential and pHon arsenic speciation and solubility
in a contaminated soil. Environ. Sci.Technol.25:1414-1419.
Mok, W.-M., and C. M.Wai. 1994. Mobilization of arsenic in contaminated riverwaters, p. 99-118. //?J. O. Nriagu (ed.),
Arsenic in the environment: part I: cycling, vol. 26. John Wiley & Sons, Inc., New York, NY.
Moore, J. N., W. H. Ficklin, and C.Johns. 1988. Partitioning of arsenic and metals in reducing sulfidic sediments. Environ.
Sci.Technol. 22:432-437.
Morel, F. M. M., and J. G. Hering. 1993. Principles and applications of aquatic chemistry. John Wiley & Sons, Inc., New
York, NY.
Nealson, K. H., and D. Saffarini. 1994. Iron and manganese in anaerobic respiration: environmental significance, physiol
ogy, and regulation. Annu. Rev. Microbiol. 48:311-343.
Newman, D., E. Kennedy, J. Coates, D. Ahmann, D. Ellis, D. Lovley, and F. Morel. 1997. DissimilatoryAs(V) and S(VI)
reduction in Desulfotomaculumauripigmentum, sp. nov. Arch. Microbiol. 168:380-388.
Newman, D. K., D. Ahmann, and F. M. M. Morel. 1998. A brief review of dissimilatoryarsenate reduction. Geomicrobiology
Journal 15:255-268.
Onken, B. M., and D. C.Adriano. 1997. Arsenic availability in soil with time under saturated and subsaturated conditions.
Soil Sci. Soc. Am. J. 61:746-752.
Osborne, F. H., and H. L. Ehrlich. 1976. Oxidation of arsenite by a soil isolate of Alcaligenes. Journal of Applied Bacteri
ology 41:295-305.
Phillips, S. E., and M. L. Taylor. 1976. Oxidation of arsenite to arsenate by Alcaligenes faecalis. Applied and Environmen
tal Microbiology 32:392-399.
Rittle, K.A., J. I. Drever, and P. J. S. Colberg. 1995. Precipitation of arsenic during bacterial sulfate reduction. Geomicrobiol.
J.13:1-11.
Rosenberg, H., R. G. Gerdes, and K. Chegwidden. 1977. Two systems forthe uptake of phosphate in Escherichiacoli. J.
Bacteriol. 131:505-511.
Sadiq, M. 1997. Arsenic chemistry in soils: an overview of thermodynamic predictions and field observations. Water, Air,
and Soil Pollution 93:117-136.
Sanders, J. G., and H. L. Windom. 1980. The uptake and reduction of arsenic species by marine algae. Estuar. Coastal
Mar. Sci. 10:555-567.
Schlegel, H. G. 1993. General microbiology, 7th ed. Cambridge University Press, Cambridge, UK.
Schlesinger, W. H. 1997. Biogeochemistry: An Analysis of Global Change, 2nd ed. Academic Press, San Diego, CA.
Sehlin, H. M., and E. B. Lindstrom. 1992. Oxidation and reduction of arsenic by Su/fo/obusacidoca/dariusstiam BC.
FEMS Microbiology Letters 93:87-92.
Seyler, P., and J.-M. Martin. 1989. Biogeochemical processes affecting arsenic species distribution in a permanently
stratified lake. Environ. Sci.Technol.23:1258-1263.
Seyler, P., and J. M. Martin. 1990. Distribution of arsenite and total dissolved arsenic in major French estuaries: depen
dence on biogeochemical processes and anthropogenic inputs. Mar. Chem. 29:277-294.
Silver, S., G. Ji, S. Brb'er, S. Dey, D. Dou, and B. Rosen. 1993. Orphan enzyme or patriarch of a new tribe: the arsenic
resistance ATPase of bacterial plasmids. Mol. Microbiol. 8:637-642.
27
-------
Spliethoff, H., R. P. Mason, and H. F. Hemond. 1995. Interannual variability in the speciation and mobility of arsenic in a
dimictic lake. Environ. Sci.Technol. 29:2157-2161.
Stumm, W, and J. J. Morgan. 1996. Aquatic Chemistry: Chemical Equilibria and Rates in Natural Waters. John Wiley &
Sons, New York.
Torriani,A. 1990. From cell membrane to nucleotides: the phosphate regulon in Escherichia coli. BioEssays 12:371-376.
Wilkie, J. A., and J. G. Hering. 1998. Rapid oxidation of geothermal arsenic(lll) in streamwaters of the eastern Sierra
Nevada. Environmental Science and Technology 32:657-662.
Willsky, G. R., and M. H. Malamy. 1980. Effect of arsenate on inorganic phosphate transport in Escherichia coli. J.
Bacteriol. 144:366-374.
Winship, K.A. 1984.Toxicity of inorganic arsenic salts. Adv. Drug React. Ac. Pois. Rev. 3:129-160.
Zehnder,A. J. B., and W. Stumm. 1988. Geochemistry and biogeochemistry of anaerobic habitats, p. 1-38. Ink. J. B.
Zehnder(ed.), Biology of anaerobic microorganisms. John Wiley & Sons, Inc., New York, NY.
28
-------
A Framework for Assessing Arsenic Leaching from Soils and Wastes
H. A. van derSloot
The Netherlands Energy Research Foundation
Westerduinweg 3, P.O. Box 1, Petten, 1755 ZG, The Netherlands
T: (+31) 224-56-4249, F: (+31) 224-56-3163, E: vandersloot@.ecn.nl
D. S. Kosson and F. Sanchez
Vanderbilt University, Dept. of Civil and Environmental Engineering
Box 1831, Station B, Nashville, TN 37235
T: 615-322-1064, F: 615-322-3365, E: David.Kosson(S)vanderbilt.edu.
Florence.Sanchez@vanderbilt.edu
R.N.J. Comans
The Netherlands Energy Research Foundation
Estimating long-term release from wastes and soils by leaching requires a testing and interpretation framework that
considers specific management scenarios. However, development of dedicated test methods to simulate the wide
variety of environmental scenarios is impractical. An alternative approach, presented here, is to measure a common set
of intrinsic leaching parameters and use models that reflect the anticipated environmental scenario to estimate release.
Thus, a common set of testing results can be used to compare alternative management scenarios, including site-specific
climate and design conditions. Alternatively, a set of default management assumptions can be used to compare the
efficacy of different treatment processes. Important intrinsic leaching properties of the soil or waste include: (i) release
potential, (ii) solubility and release as a function of pH, (iii) solubility and release as a function of liquid to solid ratio, and
(iv) mass transfer rates.
A challenge is simplification of the approach to allow routine implementation. It is proposed to achieve the goal by
carrying outtesting at two levels: (i) material characterization, and (ii) verification. Initial characterization is carried outto
define a class of materials, based on its behavior. Subsequently, simplified testing is carried out to verify that the material
being evaluated has not varied significantly from the material class that was subjected to more extensive characteriza-
tion. Evaluation is further enhanced by development of a multi-party database that facilitates comparison of the leaching
behavior for a wide range of materials. This presentation will provide an overview of the leaching framework and compari-
son of results for arsenic leaching from a variety of wastes and secondary materials. For a soil contaminated with As
caused by wood preservation, the geochemical modeling is presented. This illustrates the nature of the solubility control-
ling phases and the degree to which the model can predict the observed leaching behavior. A second paper presents
the testing protocols in more detail (see Sanchez, et al. "Protocols for Estimating Arsenic Leaching from Soils and
Solidified Wastes," 3.3 Arsenic Chemistry Session).
29
-------
3.0 Breakout Sessions
3.1 Source Identification Session
This session was designed to encourage discussion that addressed methods for characterizing and identifying arsenic
sources, and to develop recommendations for managing risk from arsenic releases/sources. The session co-chairs
were:
• Diana Bless - U. S. EPA, NRMRL
• Doug Grosse - U. S. EPA, NRMRL
Carol Russell - U.S. EPA Region VIII
The objective of the Source Identification session was to address the following three general questions:
1) What are the primary sources that contribute to arsenic releases to the environment?
2) What are the significant data gaps and information needs for characterizing and identifying arsenic sources and
waste forms?
3) What are the important insights to be conveyed regarding the management of arsenic risks for decision makers?
Speaker Abstracts
Speaker presentations addressed a variety of source identification and fate and transport issues from a broad spectrum
of sites/locations. Each presentation was followed by a brief question and answer period. Ageneral discussion address-
ing the three questions occurred after all the presentations had been completed. A summary of some of the material
discussed during the presentations and open discussion periods, including responses to the three questions, is pre-
sented in Section 3.1.1 of this report. The presentation abstracts are located in section 3.1.2 of this report.
3.1.1 Discussion Review
Primary Sources of Arsenic Releases
Natural vs. Anthropogenic Sources: Emphasis has been placed on differentiating between natural and anthropogenic
arsenic sources. This is particularly important in the West. For example, in California, expansion and development is
occurring in areas with naturally occurring arsenic in theirwatersupplies. It is, therefore, important to focus characteriza-
tion efforts and resources to protect the point of use ratherthan attempt to identify all of the source terms contributing to
the contamination problem.
There is also a growing awareness of the wide-scale (regional) nature of residual arsenic contamination from agricultural
and other anthropogenic sources such as copper and sodium-based arsenicals from herbicides and pesticides. Since
it is difficult to identify point sources for this contamination it is important to understand the complex behavior of arsenic.
Information is needed on distinguishing anthropogenic and natural sources in order to identify parameters that affect
treatment and to assess effects from other anthropogenic contaminants such as petroleum hydrocarbons from leaky
pipelines and/or underground storage tanks (USTs). Site characterization techniques (e.g., oxidation, species concentra-
tion) and guidance are also needed for collecting and analyzing data. It may be possible to determine the source of the
arsenic based upon the presence of other source-specific anthropogenic chemicals/elements (tracers) orto investigate
the history of contamination by examining reservoir sediments, dendrochronological "data," and local records. (Note: Both
sediments and wood can trap arsenic overtime.)
Background sources can be differentiated by: using regional distributions (via geo-referenced databases); assessing
local geochemical changes in arsenical type; and performing principal component analyses to determine chemometric
statistics. Geo-referenced databases are useful tools for understanding the location of sources indicating where treat-
ment should occur. Principal component analysis, which is a method of segregating and classifying samples (data) on
the basis of similarities or differences within variables, can be used to extract the main relationships for data of high
dimensionality. Outputs show similar components clustered together, while dissimilar components are shown as outli-
ers. The international community varies in the manner in which arsenic contaminant limits are developed. For ex-
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
30
-------
ample, the United Kingdom relies on localized background arsenic concentrations in natural formations to establish
contaminant levels. In the U.S., statewide and site-specific standards are used, complicated by naturally occurring and
anthropogenic inputs.
Arsenic Mineralogy: Background arsenic concentrations pose regulatory challenges due to arsenic's tendency to
occur naturally in soil, sediments, and minerals. According to Richard Glanzman, a large number of the background
ranges have been established in the early 1970s and 1980s for arsenic concentrations in rocks (igneous and sedimen-
tary), sediments, soils, and water sources. Much of the supporting information on how these background numbers were
developed has not been reported or made readily available, including the statistical design. Methods used to determine
arsenic concentrations (e.g., pulverization followed by the analysis of the whole sample) produced false negatives for
materials in which the arsenic was merely adsorbed to the surface. An extraction technique is perhaps more accurate
when arsenic is adsorbed to the surface of a material.
Based on the literature search performed by Mr. Glanzman, phosphorite and iron formations have the highest mean
background arsenic concentrations found in the different types of sedimentary rock analyzed, both 41 mg/kg. Travertine,
hot, and volcanic springs had the highest mean background concentrations of the different water sources analyzed; 304,
2,090, and 22,200 ug/L, respectively. Mine waters have also been measured at very high concentrations, from 3.0 to
400,000 ug/L.
Although some soil data are available, there is a paltry amount of information, of a national scale, on background arsenic
concentrations in soils. A national database/map would be useful in addressing these types of constituents in soil. It is
important to establish criteria for collecting these types of samples, including depth and the appropriate analytical method.
There currently exists a number of sample libraries which could be used to develop the background information needed
to assess human health and environmental impacts from arsenic.
Arsenic mobility, along with its ability to act as either a source or sink, is largely dependent on its natural form. Arsenic
naturally occurs as a major element in hundreds of minerals. In addition to native arsenic, there are 276 known arsenic
minerals including: 39 arsenides (X As), 64 arsenic sulfides (X AsS), 26 arsenites (X AsO3Y), and 147 arsenates (X
AsO4Y). Below is a list of cations (X's) associated with the different species of arsenic minerals; the cations are listed
according to their preference for each mineral type. For example, there are more arsenides containing nickel than
arsenides containing copper. There is also an equal number of arsenides containing iron and arsenides containing lead.
This information is relevant to principal component analyses.
Arsenides Ni>Cu>Fe = Pd>Sb = Co>Se>Pb
Sulfides Sb>Pb>Cu > TI>Ag>Fe = Rare Earth Elements (REE)>Hg
Arsenites (OH) = Mn = Pb>Fe>Ca = CI>Mg = Cu=Zn=Si
Arsenates (H2O)>(OH)>Ca>Fe>Zn>Cu>
Mn=Pb>Mg>UO2>CI>SO4=PO4>Co>Sb=Bi=F
Animal Feed: Arsenical feed amendments are used to promote weight gain in poultry, and the resultant manure con-
taining arsenic is an issue. Soil, sediment, poultry litter, and water samples extracted from ditches, tributaries, and
groundwater in the Pocomoke River Basin (a Chesapeake Bay watershed) yielded the following preliminary results:
Measurable arsenic was detected from poultry intensive agricultural areas;
Significant arsenic concentrations were also detected in the shallow pore water and groundwater;
Storm events indicate surface runoff from an arsenic source; and
More arsenic is transported in the particle bound phase than in the dissolved phase.
The degradation pathways of arsenical feed amendments (e.g., roxarsone) in the environment are still unknown, par-
ticularly the relationship between the organic forms in the feed and the observed forms in the environment. The
transport of arsenic during storm events needs to be better defined; especially, the impact that high application rates
and/or seasonal variation has on concentrations and transport due to overland and groundwater flows. It is particularly
important to look at the initial surge when sampling storm events. More information is also needed on natural sources
(background) of arsenic in the Pocomoke River Basin, as well as a variety of nutrients (i.e., ammonia in surface waters).
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
31
-------
Characterizing and Identifying Arsenic Sources and Waste Forms
Soils/Sediments: One of the methods used to evaluate methods for removal of arsenic from groundwater, determine
mobility of arsenic in surface water/sediments, and to assess arsenic mobility at an arsenical pesticide manufacturing
site was an electron microprobe (EM). EMswere also used at a wood preserving site to determine the forms of arsenic
in the soil and at a smelting site, to evaluate forms of arsenic in solid wastes, to determine solidification formulations
(agents, ratios, etc.), and to evaluate treatment effectiveness.
Although some samples were analyzed from the area surrounding the contaminated zone at the arsenical pesticide
manufacturing site, concerns were raised regarding whether the arsenic associated with biotite samples can be attrib-
uted to water adsorbed on the crystalline material rather than trace elements in the crystal. Ideally, more background
samples should have been collected upgradient for comparison. Also, a lower solid to liquid ratio (e.g., 20 to 1) would
probably have been warranted during SPLP leaching tests (with the Wester Formula) performed on samples from the
smelting site because concentrations can be quickly diluted with this method, which uses 60 to 70 pore volumes.
Appalachian Basin Coals: The presentation on the potential impacts of localized arsenic enrichment in Appalachian
Basin redirected the focus of the breakout session towards the impacts of large, diffusely impacted sites. Based on Mr.
Goldhaber's presentation, the presence and use of Appalachian Basin coal has resulted in significant depositions of
arsenic to river sediments in the Appalachian region. This deposition has been associated with natural weathering,
mining activities, mine waste deposition, and coal combustion/atmospheric impacts. Based upon the concentrations
found in the sediment cores, arsenic concentrations in sediments increased until particulate controls were implemented
in the mid 1970s. The advent of unleaded gasoline use in the 1970s may, also, have contributed to reductions in lead,
arsenic, and zinc deposition. Further data may be used to help determine appropriate baselines for arsenic and also
provide data for establishing future levels of emissions control for coal combustion.
Arsenic was introduced to the Appalachian Basin coal deposits during a large platonic collision that occurred during the
formation of the Appalachian range. Mesothermal gold deposits (e.g., gold/arsenic deposits), which were formed at the
distal end of a hydrothermal ore forming process, are also located to the east of the Appalachian basin. These deposits
contain the same type of elements (e.g., arsenic, antimony, thallium, selenium, molybdenum, and mercury) as found in
the Appalachian Basin coal deposits. Similar to gold deposits, this is the same grouping of elements that is transported
in sulfite-bearing solutions.
Mercury deposition from the coal-fired power plants is also being investigated. Mercury is typically concentrated in
pyrite at concentrations up to 220 ppm. There are certain elements such as germanium that are accumulated in fly ash
particles that are not normally found in soils orthe geology in the Appalachian Basin. These elements could theoretically
be used to help track the arsenic concentrations in the soil and sediments to power plant emissions. Mr. Goldhaberalso
plans to analyze arsenic-contaminated sediment samples for specific polynuclear aromatic hydrocarbons (PAHs) asso-
ciated with coal combustion in an attempt to link the arsenic deposition to power plant emissions.
Mining: Mr. Pantano supplemented his presentation with information provided in other presentations in orderto highlight
how different groups can reach different conclusions from the same or similar sets of data.
A review of arsenic data from samples in the Verde River watershed showed that: (1) water collected at the bottom of
mine tailings exhibited the highest concentration (210 ppb); (2) a well from the nearby Montezuma Castle National
Monument had the second highest arsenic concentration (94 ppb); and (3) concentrations in the Verde River were
measured at 200 ppb. Very few samples obtained in the watershed had arsenic concentrations below 10 ppb. It can be
inferred that the arsenic is due to the sulfide oxidation of the mine waste.
Specifically, water chemistry data from the oxidation of a sulfide mineral from a mine tailing near Tuzigoot National
Monument are shown in Table 3.1-1. When sodium, potassium, calcium, and magnesium are present, usually one
element is greatly exaggerated or increased due to dissolution of the host rock. In this case, magnesium, at 12,000 ppm,
has been elevated as a result of the acidic water digesting the other minerals. The presence of an elevated sulfate
concentration also illustrates Mr. Goldhaber's point that an arsenic source can be identified by the presence of an
associated byproduct or surrogate. In pyrite oxidation, sulfate is the natural byproduct.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
32
-------
Table 3.1-1. Water Chemistry Data from the Oxidation of aSulfide Mineral
Parameter
PH
Sodium
Calcium
Magnesium
Arsenic
Alkalinity
Chloride
Sulfate
Zinc
Iron
Copper
Aluminum
Acidity
Result
2.6
1.2ppm
280 ppm
12,000ppm
0.21 ppm
0
22.3 ppm
10, 000 ppm
4 ppm
75 ppm
2 ppm
550 ppm
198 ppm
When considering treatment for a waste stream with similar mineral composition, the recommended treatment approach
will more likely target the removal of the aluminum, copper, iron, or zinc over the arsenic. It is also likely that the arsenic
will be removed along with the key elements (e.g., aluminum, copper, iron, or zinc) specifically targeted by the treatment
process. It should also be noted that in mine waters containing copper, nickel, and zinc, arsenic is usually present at
concentrations between 1/100th and 1/200th of the composite elements.
While Stiff Diagrams, Horner Plots, and other thermodynamic modeling are good techniques for identifying arsenic
sources, these are hard to convey to the nonprofessional. When source information needs to be communicated to the
public, it may be preferable to present principal cation and aniondatato identify the source of the arsenic. Master thesis
data from creeks, lakes, mines, river, springs, and wells were presented during the session. Average arsenic concentra-
tions, pH, and alkalinity data are shown for each water source (see Table 3.1-2). Although it is possible to conclude that
the pH could be used as an indicator for elevated arsenic concentrations, this parameter can be very deceiving due to
buffering capacities. As a result, the alkalinity data may provide a little more information on the bulk chemistry of the
water and a better indicator for elevated arsenic concentrations since arsenic concentrations tend to increase with
alkalinity, except when acidic conditions prevail. Sulfate and magnesium data can also be used to characterize arsenic
impacts.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
33
-------
Table 3.1-2. Aerage Arsenic, pH, and Alkalinity Data
Parameter
Average of Arsenic (ppb)
Average of pH
Average of Alkalinity (ppb)
Creek
20
7.7
230
Lake
38
8.5
220
Mine
210
2.6
—
River
20
7.8
245
Spring
17
7.6
197
Well
65
7.6
303
Often, plots of sample frequency versus arsenic concentration can be log-normally distributed at different sites, as was
shown by a plot of the National Uranium Resource Evaluation (NURE) Program sediment samples taken from the
Walker Lake triangle. Thus, if a specific concentration (e.g., a background) with a very narrow range is chosen as the
decision criterion for either sampling or excavation for a site with a similar distribution, it is very likely that excessive
sampling or excavation will result. Therefore, a good understanding of concentration variation and background is very
important.
Management of Arsenic Risk
Marsh Environments: When investigating a remedial scenario, it is important to understand the phase of the arsenic,
the arsenic's mineralogic characteristics, and its solubility and bioavailability. When a reactive iron blanket is being
considered for use in a tidal estuarine environment like Castro Marsh in the San Francisco Bay Region of California, it is
important to: 1) identify the mechanism responsible for drawing the arsenic to the iron; 2) the longevity of this relation-
ship; and 3) the long-term consequence of using the peat, iron, and gypsum (PIG) amendment. It is also important to
consider the effects that the salinity in the water may have on the effectiveness of the barrier, such as possible kinetic
impacts. Pitting and other severe geochemical conditions have also been observed in iron zones in saline environments.
Questions were raised regarding whether As(lll) will be oxidized to As(V) before binding with iron in the surface water.
Although arsenic was found in the bioavailable fraction using AVS (Acid Volatile Sulfide) in sediment, referenced in EPA
821/R-91-100, sulfate concentrations in saltwater may recreate reducing conditions. Although most of the published
research on this issue does not, specifically, address iron's effect on arsenic, potentially useful information has been
published on iron passivation/activation. Workgroup participants suggested investigating the long-term benefits asso-
ciated with using different grain sizes when designing an adsorption/passivation system. They also suggested using
more pore volumes of water per mass of solid in the next set of bench scale studies for the Castro Marsh site.
Mining: Arsenic can be found in nature in its elemental form but is more commonly found as an inorganic arsenic
compound associated with other elements such as mercury, thallium, and selenium. Typically, natural arsenic levels in
western U.S. soils vary widely from 1 ppm up to about 100 ppmwith a mean value of 7 ppm. The mean concentration in
typical soil ranges from about 4 to 9 ppm. Arsenic compounds from the Barrick Goldstrike Mines, Inc. and Placer Dome
America mines are predominantly contained in naturally occurring minerals within the precious metal-bearing ore and
associated waste rock. Arsenic is not added to any of the natural earth materials processed on site at the Barrick
Goldstrike Mines and Placer Dome America mines.
In general, the indigenous arsenic compounds in waste rock are not altered by the mining process and remain as the
naturally occurring minerals that were present in the rock before it was mined. The arsenic is managed as an integral
constituent of the waste rock in engineered disposal facilities on-site. Thus arsenic and acid mine drainage (AMD) are
main concerns during the design of the waste rock areas, tailing impoundments, and heap leach liner systems.
Ores from both the Barrick Goldstrike and Placer Dome America mines containing naturally occurring arsenic compounds
requiring pretreatment (e.g., via pressure oxidation or roasting) are oxidized in an acidic pH environment and neutralized
in an alkaline environment priorto beneficiation to form insoluble calcium or iron arsenates. Naturally occurring arsenic
compounds are not affected by the beneficiation process and pass through the circuit as unchanged, inert materials
under normal leach conditions. Certain copper-gold ores containing high values of naturally occurring arsenic compounds
are roasted in an acidic pH environment, in which the arsenic is volatilized to form arsenic trioxide, which is subsequently
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
34
-------
collected in a bag house and either sold as arsenic trioxide product or disposed as a hazardous waste. Arsenic
compounds resulting from the beneficiation of ore, including both tank leach and heap leach facilities, are managed in
engineered containment structures.
Table 3.1-3 illustrates how the Barrick Goldstrike Mines, Inc. and Placer Dome America mines are prominently featured
in the 1998 and 1999 public reports for the EPA Toxic Release Inventory (TRI) program. Fugitive dust emissions from the
waste rockdisposal areas resulting from dumping and wind effects are responsible forthe majority of the fugitive arsenic
releases to the air. The majority of the material responsible for the 33,000,000 (Barrick) and 28,009,300 pounds
(Placer) of arsenic released to surface impoundments is managed in a composite tailing impoundment system with a
liner and clay barrier. Arsenic releases associated with "Other Disposal" refers to non-contained/impoundment dis-
posal scenarios, such as waste rock disposal.
According to Mr. Eurick and Mr. Schoen, the Barrick Goldstrike Mines, Inc. and Placer Dome America mines do not
substantially contribute arsenic to the natural earth material; their operations utilize engineered and designed closure
and reclamation of waste rock, tailing, and heap leach facilities, thus minimizing the potential for arsenic releases to the
environment. They also stated that the reported TRI values for arsenic for both sites have not been demonstrated to
represent a health or environmental concern.
It is important to clarify that TRI data, as reported, represent releases that are permitted by federal and state agencies,
not exposures. TRI also does not report concentrations. TRI data are specific numbers calculated in accordance with
guidance provided by the Emergency Planning and Community Right To Know Act (EPCRA). According to the mining
industry, the relevance of releases has been somewhat confused by the issue of coincidental manufacturing. During
coincidental manufacturing, naturally occurring mineral arsenic is converted/broken down during pretreatment (roast-
ing) to render the sulfur and carbonaceous materials inert. Under the current guidance, a second set of arsenic releases
is tallied for these new compounds. Thus, arsenic oxide formation is accounted for on top of the arsenic mineralization
coming into the system and the arsenic in the waste rock. Also, TRI data have been used to set objectives for research
and data needs. Other "numbers" besides TRI data should also be looked at, including Clean Air Act (CAA), CWA, and
RCRAdata.
Although a lot of emphasis has also been placed on reducing mercury emissions from mining sites, additional controls
for mercury should not have an impact on arsenic compounds since mercury releases are relatively small compared to
arsenic releases. These reductions are dwarfed by the huge arsenic releases at these sites. However, it may be useful
to assess and compare how much arsenic was removed from the ore circuit following the addition of organic sulfide to
reduce mercury throughout the circuit to achieve 90% reduction (Reference: Cortex Mine).
Wood Treating: Jim Easier from Osmose, Inc. gave a brief presentation as a representative of the wood treating
industry. Wood treating is an older, more established industry associated historically with shipbuilding, railroads and
utilities. In the mid 20th century, consumer use of treated wood became very popular (e.g., for decks and landscaping).
In the 1980s, water based wood preservatives, like chromated copper arsenate (CCA), experienced a tremendous
growth.
Currently, sixto seven billion board feet of dimensional lumber are preserved each year using a variety of preservatives
such as creosote solutions, pentachlorophenol systems, copper and zinc naphthalate, CCA, ammoniacal copper zinc
arsenate, etc. Approximately 30 years ago, Osmose, Inc. began to research alternative preservatives. Although they
introduced a non-arsenical system called copper citrate, this system has not been commercially successful largely due
to costs, and it is not as effective.
Some risk associated with using preserved wood has been identified. The wood treating industry recently performed a
risk:benefit analysis that concluded that the benefits of using preserved woods far outweigh the risks. Although the
wood preserving industry believes that when used properly, CCA is very safe, it is also very responsive to arsenic-
related concerns and is investigating alternative preservatives systems. For example, the wood preserving industry
has also been investigating heavy copper formulations that are comprised mostly of copper and have environmental
tradeoffs, as compared to CCA. As of January 1, 2004, EPA will not allow CCA products to be used to treat wood
intended for residential uses. The wood preserving industry voluntarily agreed to discontinue the use of CCA in con-
sumer wood products by December 31, 2003.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
35
-------
Table 3.1-3 Arsenic andTRI in Select Gold Production Operations
RELEASED TO
Fugitive Air
Stack Air
Water
Underground
Injection Control
Other Landfill
Surface Impoundment
Other Disposal
Publicly Owned
Treatment Works
Other Offsite Transfer
TOTAL
QUANTITY (pounds)
4000
72,500
340
870
12
0
0
0
0
0
33,000,000
28,009,300
160,000,000
24,342,000
0
0
1
0
% TOTAL
<0.01
0.05
<0.01
<0.01
<0.01
0
0
0
0
0
17
53
83
46
0
0
<0.01
MAJOR SOURCES
Waste Rock/Roads/Ore
Waste Rock/Ore/Process
Humboldt River
N/A
N/A
Tailing Impoundment
Waste Rock/Spent Heap
Ore 1 Infiltration
N/A
Transfer to TSDF
193,004,353/52,364,670
References:
Barrick 1999TRI Data (Goldstrike/Meikle Complex) As Compounds
Placer Dome 1999TRI Data-NV Operations (Pipeline, Bald Mountain, Getchell)As and As Compounds (bolded and
in italics)
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
36
-------
3.1.1.1 Summary of Important Conclusions and Recommendations from the Source Identification Session
Primary Sources of Arsenic Releases
1. The following activities/processes are responsible for arsenic releases to the environment: oxidation/reduction, ad-
sorption/co-precipitation, evapoconcentration, biodegradation, volatilization, photo-reactivity, ingestion/metabolism,
irrigation, over-pumping of aquifers, and transport processes such as advection, dispersion, and diffusion.
2. Hot springs (geothermal), igneous rock (basalt), sedimentary rock (organic/inorganic clays, shale), metamorphic
rock (slate), seawater, mineral deposits, and volcanoclastic materials/releases are the primary natural sources of
arsenic releases to the environment.
3. Anthropogenic sources of arsenic include: historic mining sites, pesticide/herbicide use, combustion byproducts
from burning fossil fuels, animal feeds/waste byproducts, historic wood preserving sites, medicinal uses, fertilizer
use, landfill leachate, glass production, and tanneries.
4. Production sources typically have higher concentration, localized arsenic releases. Application sources typically
have lower concentration, widespread arsenic releases.
Characterizing and Identifying Arsenic Sources and Waste Forms
1. Soil characterization information is needed that defines background arsenic concentrations/conditions in different
types of soils and the impacts that arsenic introduction can have on different types of soils.
2. Arsenic mineralogy, geoavailability, bioavailability, and leachability should be characterized at each site in order to
help identify the source of an arsenic release and determine whether it is natural or anthropogenic. Speciation data
also need to be collected, particularly As(lll) and As(V) data.
3. Characterization techniques need to be standardized. Generic guidance is needed that can be used to help
identify impacted media, characterize contamination, and assess potential impacts. Sampling designs need to be
developed that are capable of providing the data needed to address these issues.
4. Before characterizing the impacted media at a site and determining potential management approaches, it is impor-
tant to first identify the temporal and spatial scale of the system, potential receptors, and potential physical, chemi-
cal, and biological transport processes. Methods and/or models need to be developed in order to perform
multimedia integrations across spatial/temporal scales.
5. Information and techniques are needed which can be used to predict how natural or anthropogenic changes will
impact arsenic fate and transport, both in the short- and long-term. Fundamental kinetic and thermodynamic data
(e.g., the adsorption coefficients of both phosphate and arsenic on iron oxide) can be used to assess transforma-
tions between phases.
Management of Arsenic Risk
1. It is important to monitor arsenic releases and provide this information to the public.
2. It is important to identify an arsenic contamination/release problem, understand how to fix the problem, and then
monitor the performance of the selected corrective action.
3. The risk from an arsenic release needs to be well defined. It is also important to differentiate real versus perceived
risk.
It is important during a risk characterization to predict the environmental effects of the arsenic release
3.1.2 Source Identification Session Speaker Abstracts
Speaker abstracts from the Source Identification session are presented in this section.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
37
-------
Distinguishing Natural and Anthropogenic Sources of Arsenic:
Implications for Site Characterization
Scott D. Warner, CHG, CEG
Geomatrix Consultants, Inc.
2101 Webster Street, 12thFloor, Oakland, CA 94612
T: 510-663-4269, F: 510-663-4141, E: swamer@.geomatrix.com
Both anthropogenic and natural sources contribute to the presence of arsenic in soil and groundwater. Understanding
both source types, as well as the geohydrochemical conditions for a given site should be considered important in
developing and implementing an effective site characterization program, and ultimately, a technically feasible and cost-
effective management or remediation program. Anthropogenic sources of arsenic, including mineral processing, glass
manufacturing, wood preserving, pesticide production and application, landfill/waste pile leaching, and coal/oil produc-
tion and processing, typically are localized and seldom result in regional increases in arsenic concentration with the
possible exception of the widespread application of arsenical-pesticides/herbicides. Natural sources of arsenic, ofwhich
there are nearly 250 naturally-occurring arsenic-containing minerals, including volcanically-derived sediment, sulfide
minerals, and metal oxides, can affect large areas. The "background" contribution of the natural sources creates addi-
tional complexity in assessing the impact of arsenic at a given site with respect to developing appropriate site solutions.
Arsenic is a redox-sensitive element, and its presence, distribution, and mobility is dependent on the interplay of several
geochemical factors including reduction-oxidation reactions, pH conditions, microbial activity, the distribution of other
ionic species, and general solution chemistry of pore-waterorgroundwater. These factors, which are influenced by both
natural and human-based conditions and activities, in turn control the major adsorption/desorption and precipitation/
dissolution reactions that influence arsenic mobility. The two primary redoxforms of arsenic, arsenate and arsenite, can
occur in almost any hydrogeochemical setting, although arsenate generally predominates under oxidizing conditions
with arsenite predominating under reducing conditions. For waste site settings (e.g., anthropogenic sources), the type of
arsenic present in the subsurface will be strongly affected by the contributions of other waste types, including hydrocar-
bon compounds, which tend to affect pH and redox conditions of the subsurface system, as well as the form in which the
arsenic was released. Crude arsenic trioxides typically contribute to the presence of arsenates in near-surface, oxygen-
ated soil and groundwater. Reduction due to the presence of hydrocarbon contributions can, in turn, result in the
reduction and change of mobility of the arsenic ion. Local releases of sulfuric or nitric acids in waste streams, can in
turn, reoxidize arsenite to arsenate. Because conditions can change greatly over short distances in such release sites,
site characterization programs must involve a comprehensive understanding of the history of releases, as well as back-
ground information with respect to ambient site conditions.
This presentation will discuss issues associated with the types and conditions of arsenic sources and release scenarios,
as well as the characterization techniques important to developing a representative interpretation of the site conditions.
38
-------
Arsenic Background, Associated Elements and Factors Controlling Mobility
Richard K. Glanzman
CH2M HILL
100 Inverness Terrace East, Englewood, CO 80112-5304
T: 303-771-0900, F: 303-754-0196, E: rglanzma@.CH2M.com
This presentation includes representative arsenic multimedia background concentrations, and mineralogy and controls
on arsenic mobility with case histories illustrating these controls. There is a rich history of background arsenic concen-
trations in most media that are readily sampled in the environment. These background values are strongly related to
their origin but the physiochemical conditions where they originate are generally poorly described in tabulations from the
literature. Background arsenic concentrations can be used to determine distribution, attenuation and bioaccumulation
coefficients but the site-specific conditions within which the background concentrations were determined and for which
one is interested need to be carefully evaluated before their use.
Arsenic naturally occurs as a major element in hundreds of minerals and is associated as a minor or trace element in
hundreds of additional minerals. Fortunately, most of these involve sulfide and sulphosalt minerals or iron oxydroxide/
oxide phases. This considerably simplifies the geochemical conditions one requires to estimate arsenic mobility and
arsenic concentrations. From the above mineralogical relationships it is obvious that pH and closed-cell oxidation reduc-
tion potential measurements are required field measurements. Unfortunately, most regulatory data requirements collect
laboratory instead of field pH values and dissolved oxygen instead of ORP values.
Ongoing geochemical research on arsenic has lead to the quantification of arsenic adsorption onto iron oxyhydroxide/
oxide phases under natural conditions involving multiple competing ions. The specific rank of arsenic speciation with
respect to commonly associated dissolved metals and other common ions has been developed along with the total
adsorption capacity of iron oxyhydroxide/oxide phases. The kinetics of most of these reactions is generally very rapid,
commonly less than a few seconds to a few hours, therefore, kinetics is not usually an issue, as it is for manganese.
Current research defines the actual adsorption mechanisms and range of irreversible sorption characteristics under
oxidizing conditions but not the range of probable arsenic release under reducing conditions. Reducing conditions need to
be considered in the TCLP protocol for landfill disposal of arsenic adsorbed to iron oxyhydroxide.
39
-------
Reconnaissance for Arsenic in a Poultry Dominated Chesapeake Bay Watershed -
Examination of Source, Transport, and Fate
T.C. Hancock1, J.M. Denver, G. F. Riedel, and C.V. Miller
1U.S. Geological Survey
1730 E. Parham Rd., Richmond, VA
T: 804-261-2618, F: 804-261-2659, E: thancock@usas.aov
The source, transport, and fate of several arsenic compounds are being investigated in water, soil, and sediment of the
Pocomoke River Basin in Maryland and Delaware. This basin in the Chesapeake Bay Watershed has a high concentra-
tion of poultry-feeding operations where arsenic feed amendments are used extensively. Concentrations of total arsenic
in fresh poultry manure collected from the Pocomoke River Basin were as high as 27 mg/kg, whereas older, composted
manure contained less than 2 mg/kg total arsenic. Arsenic in composting manure may be volatilized, and during rain
events, it is likely leached into water. Total arsenic in agricultural and forest soil of the Pocomoke River Basin was 1-2
mg/kg; these soils had similar concentrations of arsenic as the composted manure sample. Base-flow concentrations of
total arsenic in suspended particles and in bed sediment in the Pocomoke River and its tributaries were 0.8-21.0 mg/kg
in both 1997 and 1999. Concentrations of total dissolved (0.45 urn filtered) arsenic in water samples from the Pocomoke
River did not exceed 1.6 ug/L during base-flow. Concentrations of total dissolved arsenic in agricultural ditches and in the
Pocomoke River increased during high flow, presumably due to runoff.
Although the initial input of arsenic to the basin from poultry waste is in the form of organic arsenic compounds, we found
mostly inorganic arsenic (As III and As V) and relatively low concentrations of methylated arsenic in pore water in cored
sediments collected beside an agricultural field. Total arsenic in pore water in surface sediments and at depths to 8 feet
ranged from below detection limits to as high as 29 ug/L. The As (V) concentrations were elevated in pore water from the
near-surface sandy soil (29 ug/L) and from an iron-rich clay silt layer at depth (24 ug/L). As (III) was not detected in the
near-surface sediments, but increased with depth to 11 ug/L.
Shallow groundwater from piezometers near agricultural fields, which had total dissolved arsenic concentrations as
high as 23 ug/L, appears to be an important reservoir for arsenic cycling in the Pocomoke Basin. Water from a deeper,
semi-confined part of the surficial aquifer system, which is a drinking water source, had total dissolved arsenic concen-
trations as high as 8 ug/L. This deeper groundwater also had relatively high concentrations of dissolved iron (25-29
mg/L) and did not contain any obvious signs of agricultural influence. These findings suggest two sources of arsenic in
the basin: poultry waste spread on land, and a natural source associated with iron-rich sediments, particularly at depth.
Elevated arsenic concentrations were observed in groundwater with low dissolved oxygen content, and under these
reducing conditions, groundwater has the potential to mobilize arsenic from the reduction of metal oxides.
To understand all the potential sources and sinks of arsenic in the basin, total arsenic concentrations in soil and bed
sediment samples representing varying intensities of agricultural land use will be analyzed. Core sediment collected
from various locations and representing various land uses in the basin will be analyzed for total arsenic, carbon, and
sulfur. In addition, grain-size analyses and sequential partial extractions will be performed to characterize the sedi-
ments. Storm-runoff samples will be measured for total arsenic and arsenic speciation in both whole water and dis-
solved (filtered) samples. Sampling also will be expanded to other tributaries in the Chesapeake Bay Watershed af-
fected by high-density poultry operations, such as the Shenandoah Valley of Virginia.
40
-------
Characterization of the Forms of Arsenic in Soil/Sediment To
Evaluate Mobility and Treatment
Roger L. Olsen, Ph.D., Kent S. Whiting, and Richard W. Chappell, Ph.D.
Camp Dresser & McKee, Inc.
1331 17th Street, Suite 1200, Denver, CO 80202
T: 303-298-1311, F: 303-293-8236, E: olsenrl@cdm.com
The chemical compositions or forms of arsenic in solid materials are typically evaluated using indirect methods such as
sequential leaching procedures or elemental analyses. As opposed to indirect methods, electronmicroprobe (EM) tech-
niques can determine the form, associations and morphology of individual particles of arsenic-containing materials.
This information is extremely beneficial in evaluating the mobility and treatment of arsenic in solid materials.
Case Study No. One - Arsenical Pesticide Manufacturing Site
Waste materials from the manufacture of sulfuric acid and lead arsenate were disposed of at this site. Subsequent
disposal of animal by-products and hides caused reducing conditions which mobilized the arsenic resulting in arsenic(3+)
and organic (methylated) arsenic in groundwater. The contaminated groundwater is confined to the outwash deposits
of a buried valley aquifer and discharges to a surface water pond. Even though elevated concentrations of arsenic enter
the pond from the groundwater (490 °=g/L) and pore water concentrations in the pond sediments are high (1,700 °=g/L),
concentrations of arsenic in water discharging from the pond are very low (<5 - 12.2 °=g/L). EM studies of the pond
sediments indicated that the arsenic had been removed by adsorption to natural iron-containing minerals (e.g., biotite).
The adsorption capacity of the sediments was measured to be 3,350 mg As/Kg of sediment.
Case Study No. Two - Wood Treating Site
At this site, wood was treated with zinc meta-arsenite (ZnAs^) and resulted in contaminated soil. Batch leaching
studies were performed to determine the mobility of the arsenic in the soil. Results indicated "reverse" isotherms with
lower adsorbed concentrations in the soil at higher water concentrations. EM studies of the soil revealed arsenic-
containing (e.g., 0.5 percent) iron oxyhydroxide solid phases. In addition, small particles of arsenic oxide (63 percent
arsenic) were identified. Overall, the arsenic is present as arsenic oxide, in solid-solution with iron oxyhydroxide and
adsorbed to iron containing minerals. The "reverse" isotherms are caused by dissolution of arsenic phases followed by
adsorption onto the iron-containing minerals.
Case Study No. Three - Smelter Site
During the smelting of mineral concentrates to produce lead, zinc and other metals, a variety of waste materials were
produced including calcine and bag house dust. These wastes and the associated contaminated soil contained large
concentrations of arsenic (up to 20,900 mg/Kg). One alternative to treat the contaminated soil and solid waste was
through solidification/stabilization (S/S) techniques. EM analyses were used to identify the form of the arsenic in the
original waste materials and contaminated soil and in the treated materials from the S/S processes. The evaluations
were used to determine the type and quantity of S/S agent to use and to determine the effectiveness of the treatment
process. The calcine waste contained arsenic in the form of arsenopyrite, scorodite and arsenic-bearing oxyhydroxides.
Due to the potential instability of scorodite at elevated pH values (caused by the cement S/S agent), ferrous sulfate was
added to the mixture. The iron (2+) assisted in removing any arsenic leached from the solidified waste by coprecipitation
with iron oxy hydroxides. EM studies indicated this process was effective with abundant iron oxyhydroxides present with
up to 0.7 percent arsenic in the solidified materials.
41
-------
Iron Amendments as Adjuncts To Constrain Arsenic Solubility in a
Marsh Environment
Andy Davis, Ph.D.
Geomega
2995 Baseline Rd, Suite 202, Boulder, CO 80303
T: 303-938-8115, F: 303-938-8123, E: andy@.geomega.com
Upon remediation/removal of Castro Marsh sediments, there will be remnant arsenic (As) concentrations of up to 100
mg/kg. As an adjunct to removal, an amendment was developed to mitigate any remnant soluble arsenic that may
possibly migrate to Castro Creek.
Peat, Iron and Gypsum (PIG) envisioned to be emplaced at the base and on the downgradient face of the sediment
excavation were investigated. One set of experiments using Zero Valent Iron (ZVI) was remarkably successful, result-
ing in removal of >99% of soluble arsenic from the system. Phase II of the study (upcoming) is designed to determine
the particle size and mass of ZVI necessary to provide a long-term solution to soluble As in the Castro Marsh, and also
to optimize costs.
The release of arsenic into solution was investigated initially by combining site groundwater (~3 ppm arsenic), marsh soil
(2000-3000 mg/kg arsenic), clean topsoil, and/or Dl water with and without the addition of peat, iron, and/or gypsum as
soil amendments. The soil amendments were incorporated into specific reaction vessels (along with the water and soil
media) in order to determine if these amendments could augment the removal of arsenic from solution. In this experi-
ment, three media combinations were used in the reaction vessels (either with or without amendments). They were:
1. Site Water + Clean Fill
2. Site Soil + Dl Water
3. Site Soil + Site Water
Of these three combinations, only numbers 1 and 2 provided useful data, see Figure 1. The results from these two
media combinations are summarized below.
1. Clean Fill + Site Water (no soil amendments) resulted in ~60% removal of aqueous-phase As.
2. Clean Fill + Site Water + Iron (either Fe or FeSO4) resulted in ~99 % removal of aqueous-phase As.
3. The amendments CaSO4 and peat did little to remove As when combined with clean fill and site water.
4. Oxic and anoxic experiments produced comparable results for comparable media combinations.
5. The use of FeSO4 as a soil amendment produces high levels of Fe and SO4 in solution (1800 and 1400 mg/L,
respectively).
42
-------
Figure 1. Phase 1 Results for Site Water Combined with Clean Fill
Arsenic Removed from Solution - Site Water, Clean Fill, Soil Amendments
o%
Clean Fill +
Site Water
Clean Fill +
Site Water
Fe (20 g)
Clean Fill +
Site Water +
FeS04 (20 g)
Clean Fill +
Site Water +
CaSO4 (20 g)
2000
1800
Clean Fill +
Site Water +
Peat, FeSO4, &
CaSO4 (7 g, each)
43
-------
Potential Environmental Consequences of Localized Arsenic Enrichment
in Appalachian Basin Coals
M.B. Goldhaber1, E. R. Irwin2, J.R. Hatch3, J. C. Pashin4, A. Grosz5,
Kolker6, E.G. Callender7, and J. Grossman8
1USGS, MS 973, Denver Federal Center, Denver, CO 80225, T: 303-236-1521, E:
mgold@usgs.gov
2USGS, 331 Funchess Hall, Auburn University, Auburn, AL 36849-5414
T: 334-844-9190, E: eirwin@usas.aov
3USGS, MS977, Denver Federal Center, Denver, CO 80225, E: jrhatch@usas.aov
"Geological Survey of Alabama, P. 0. Box 0., Tuscaloosa, AL 35486-9780
5USGS, MS954, National Center, Reston, VA20192, T: 703-648-6314, E: agrosz@usas.gov
6USGS, MS954, National Center, Reston, VA20192, T: 703-648-6418, E: akolker@usgs.gov
7USGS, MS430, National Center, Reston, VA20192, T: 703-648-5826, E: eccallen@usas.aov
8USGS, MS954, National Center, Reston, VA20192, T: 703-648-6184, E: jgrossman@usgs.gov
Coals from the Appalachian Basin in the eastern U.S. are locally quite enriched in arsenic. The highest arsenic concen-
trations for all U.S. coals, up to 2500 mg/kg on a whole coal basis, are found in Pennsylvanian bituminous coals of the
Warrior Cahaba and Coosa coal fields, in northern Alabama. More generally, coals in the central and southern Appala-
chian Basin, may locally contain up to several hundred-ppm arsenic. Investigation by SEM, electron microprobe, and
Laser-Ablation ICP Mass Spectroscopy demonstrates that the arsenic in Appalachian Basin coals is contained in the
mineral pyrite. Pyrite in the Warrior Basin has up to 4.7 weight percent arsenic and is accompanied by elevated mercury,
molybdenum and selenium contents.
To evaluate the possible environmental dispersion of arsenic from coals, three studies are underway. The first is in
Alabama. Archived stream sediment samples from nearly 3000 sites in northern Alabama collected during the National
Uranium Resource Evaluation (NURE) Program of the early 1970s were reanalyzed for arsenic. These data reveal that
stream sediment arsenic is clearly enriched in Warrior Basin steam sediments (generally > 12ppm) compared to adja-
cent areas (<12ppm). A more geographically focused study of several abandoned coal mines documented that aban-
doned coal waste piles are a significant source of both acid and stream sediment arsenic. Stream waters from these
sites are enriched in iron, aluminum, and zinc but not arsenic. However, stream sediments associated with these coal
acid mine drainage sites did have elevated concentrations of arsenic ranging from 4 to 180 mg/kg with an arithmetic
mean of 48 mg/kg. Streams adjacent to operating strip mines show no significant impact on either water or sediment.
A second study also involving reanalysis of NURE stream sediments in the eastern Kentucky coal field revealed detectible
but much more subdued stream sediment arsenic enrichments than in Alabama. However, natural weathering of Devo-
nian shale in rocks immediately west of the coal-mining region has produced significant stream sediment arsenic enrich-
ments of up to 100 ppm.
The third study focused on West Virginia. NURE stream sediment geochemical data show elevated arsenic concentra-
tions in the northwest portion of the state where coal mining does not occur. The arsenic-enriched area is south of a
large concentration of coal-fired power plants. To test whether coal fly ash was a source of the observed stream
sediment arsenic enrichment, a reservoir in the effected area was cored to determine the temporal evolution of arsenic
in the catchment. Very preliminary results indicate an input of coal fly ash that peaked in about the mid 1970s, and has
been declining since. The arsenic is accompanied by elevated contents of zinc and lead.
44
-------
Arsenic Concentrations in Water at Mining Sites
John Pantano
ARCO Environmental Remediation
307 East Park Street, Suite 400, Anaconda, MT 59711
T: 406-563-5211 Ext. 427, F: 406-563-8269, E: pantanj1@bp.com
Hard rock mining occurs where metal concentrations are high. There are several different geological settings that are
responsible for enrichment of metal concentration in ore bodies. Epithermal (volcanogenic massive sulfide deposits)
and supergene (in hot, arid regions where surface waters tend to redistribute metals from an exposed porphyry system,
concentrating it elsewhere) enrichments are two types of geological processes targeted for mining. Trace elements are
usually elevated in these areas. Geographically these metal deposits coincide with the "Rim of Fire,"the area of volca-
nism that rings the Pacific Ocean.
Predominately iron, magnesium, aluminum and calcium are the major cations of the minerals. Arsenic usually is present
in trace amounts. Both mining processes and natural weathering of these materials releases the elements of minerals
into the water phase. There are two main processes that transform the elements from solid phase to aqueous species.
Biological mediated oxidation of sulfide minerals produces acid and iron in solution (Equation 1).
(1)FeS2 + 7/2O2+ H2O —> Fez+ + 2 SO/- + 21-T
The abiotic actions may further dissolve the solids, due to low pH and oxidation-reduction reactions (Equations 2 & 3).
(2)FeS2 + 14 Fes+ + 8 H2O —> Fe2+ + 2 SO/- + 16H*
(3) F&+ + ~02+ H* —> Fes+ + ° H2O.
Under acidic conditions arsenic is co-dissolved with the major elements and transformed into an aqueous specie when
pH is below 4.
The amount of arsenic in the water changes as the water interacts with its surroundings. Whether the changes in the
water chemistry are due to interactions with geological materials, mining processes or water treatment, several trends
have been observed and are consistent with known geochemical reactions. As the pH of the water is increased, iron and
aluminum are precipitated out as oxy-hydroxides. Once above pH 5, because iron concentrations are usually 10-50
times those of arsenic, most of the arsenic is removed from the water and deposited with the iron oxy-hydroxide. Agood
deal of work has gone into investigating removal of arsenic with iron addition and reactions with much lower concentra-
tions. My observations are that arsenic concentrations are reduced to below levels of concerns as a side benefit,
because other elements (e.g., iron, copper, zinc, etc.) require more attention and arsenic is usually removed early on in
the process to clean water.
After reviewing data at mine sites, I have observed that arsenic is:
1. Present at many sulfide deposits as a trace element;
2. Potentially in the water above level of concern, if pH is below 4; and
3. Removed from the water phase once pH goes above 5-6.
45
-------
Arsenic and TRI in Select Nevada Gold Production Operations
Steve Schoen
Placer Dome America
HC66-50, Star Route, Beowawe, NV 89821
T: 775-468-4408, F: 775-468-4610, E: steve schoen(S)placerdome.com
Glenn Eurick
Barrick Management Corporation
136 East South Temple, Suite 1050, Salt Lake City, UT 84111
T: 801-741-4666, F: 801-541-3577, E: bacslc2@worldnet.att.net
Gold deposits mined by Barrick Goldstrike Mines Inc. and Placer Dome America in Nevada are enriched in arsenic.
Mining and processing of these deposits to recover gold currently creates a reporting requirement for arsenic and/or
arsenic compounds underthe Toxic Release Inventory (TRI) Program. Other pre-existing, media-specific environmental
programs regulate processing, reclamation, and monitoring of all mined materials.
Arsenic values reported by these two Nevada mining interests for the calendar year 1999 TRI Program were calculated
to be 217,397,023 pounds. Release categories of primary significance were surface impoundments, reflecting manage-
ment of tailing in tailing impoundments, and other disposal reflecting management of waste rock in disposal areas.
This paper describes the occurrence of arsenic in our precious metals ores, how arsenic is accounted for and reported
in the TRI Program, and the environmental protection technologies used at these U.S. gold mines to properly manage
arsenic-bearing materials; thus minimizing releases of arsenic compounds to the environment.
46
-------
3.2 Treatment and Disposal Session
This session was designed to promote discussion of the chemical fundamentals related to the treatment and disposal of
arsenic wastes and to develop conclusions about the current state of knowledge and recommendations for further
research. The session co-chairs were:
Paul Randall, Senior Chemical Engineer - U.S. EPA, NRMRL
Robert Robins, Scientific Fellow -AquaMin Science Consortium International
ChristopherImpel Uteri, Environmental Engineer - U.S. EPA, NRMRL
The objective of the Treatment and Disposal Session was to address the following questions:
1) What are the long-term stability issues impacting the land disposal (i.e., on-site storage or landfills) of arsenic sta-
bilized wastes?
2) How do current advances in molecular chemistry and leaching methodology impact the areas of arsenic treatment
and disposal?
The highest priority research needs in advancing arsenic treatment and disposal were identified at the conclusion of the
session.
Speaker Abstracts
The abstracts for presentations made during this session are located in section 3.2.2 of this report. The session began
with an overview of arsenic treatment technologies. Several case studies of mining wastes sites were presented fol-
lowed by several presentations on treatment technologies featuring phytoremediation, chemical fixation, cement stabili-
zation, electrokinetics, and soil washing. The session participants then discussed the presentations and treatment and
disposal issues in order to address the session questions. The discussion is reviewed in section 3.2.1.
3.2.1 Discussion Review
A variety of technologies can be used to treat arsenic-bearing materials. Table 3.2-1 presents these treatment tech-
nologies and the number of times they have been used to treat wastes and environmental media containing arsenic at
full-, pilot-, and bench-scale levels. These data are taken from a recent "white paper" review by EPA and other inves-
tigators of technologies available to treat wastes and media containing arsenic and their usage.
These treatment technologies are used to stabilize and/or remove arsenic contamination in order to reduce its impact
to the environment. Recycling uses pyrometallurgical or precipitation techniques that convert arsenic waste to a con-
centrated arsenic product. Vitrification, incineration, soil flushing, soil washing/acid extraction, electrokinetics, and
phytoremediation are for the treatment of non-wastewaters. Chemical precipitation, ion exchange, carbon adsorption,
membrane separation, foam floatation, and permeable reactive barriers are for the treatment of process wastewater,
groundwater, and wellhead treatment. The following paragraphs present highlights and key points generated from the
arsenic treatment and disposal case studies and current research efforts.
A large amount of arsenic contaminated media is generated from mining activities. A variety of treatment technologies
are being developed and employed at mines, mining waste sites, and impacted environments to treat this material for
beneficial reuse. For example, options for managing 265,000 tons of arsenic trioxide-bearing dust stored underground
at the Giant Mine site, in Yellowknife, Northwest Territories, Canada are being assessed. At the Newmont gold mining
site in Minahasa Raya, Indonesia, mine tailings are treated prior to submarine disposal on the sea floor.
EPA's Mine Waste Technology Program researches the removal of arsenic from waters impacted by the mining industry.
This program is evaluating a mineral-like (mineral-based) precipitation process from MSE Technology Applications Inc.
(MSE), which compares favorably to other conventional technologies (i.e., alumina adsorption and ferrihydrite adsorp-
tion) for arsenic removal and stabilization of arsenic byproducts. Mineral-like precipitation along with reductive precipi-
tation and catalyzed cementation are also effective in removing arsenic from groundwater.
The University of Florida discovered that the Brake fern is an extremely efficient arsenic-hyperaccumulating plant. The
plant has a large capacity to uptake arsenic from the soil and translocate it to the aboveground biomass (i.e., fronds) in
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
47
-------
Table 3.2-1 Frequency of Use of Treatment Technologies Used To Treat Wastes And Environmental Media Containing
Arsenic
Treatment Technology
Solidification/stabilization
Precipitation and Oxidation
Adsorption
Recycling
Ion Exchange
Vitrification
Soil Washing
Permeable Reactive Barriers
Soil Flushing
Electrokinetics
Membrane Filtration
Phytoremediation
Full-Scale
69
35
9
9
5
5
4
2
2
1
1
0
Pilot-Scale
2
10
5
1
0
10
3
0
0
1
23
0
Bench-Scale
2
2
2
6
2
a short period of time. The arsenic-rich biomass would then be treated as a hazardous waste. Brake ferns are tropical/
subtropical plants that are hardy, sun tolerant, and easy to reproduce. They show great potential in phytoremediating
arsenic contaminated sites in the southeastern U.S.
Southern Company is involved in several arsenic remediation projects. They are currently investigating in-situ chemi-
cal fixation. Batch and column tests were conducted with various mixtures of soil, water and reagents. Binding re-
agents/formulations used were: ferrous sulfate, ferrous sulfate and potassium permanganate, and ferrous sulfate,
potassium permanganate, and calcium carbonate. Although all treated soils passed the Toxicity Characteristic Leach-
ing Procedure, SW846 Method 1311 (TCLP), only soils treated with ferrous sulfate passed the Synthetic Precipitation
Leaching Procedure (SPLP). Southern Company is also evaluating variables that influence arsenic mobility, as well as
conducting an economic analysis of arsenic remediation treatment methods. Additional information can be found at the
following website: www.eng.fsu.edu/departments/civil/research/arsenicremedia/index.htm.
Researchers at Victoria University in Australia treated arsenic wastes with several S/S formulations. They evaluated
the effectiveness of treatment by three different leach tests. Their investigation showed that S/S formulations contain-
ing exclusively Portland cement were the most effective. Formulations incorporating additional iron were the least
effective in preventing arsenic leaching from the treated waste. Clemson University is currently developing an inexpen-
sive magnetic filtration/adsorption technology that can purify water supplies that may be contaminated with arsenic.
DuPont has developed a phased approach for evaluating the use of soil washing fortreating arsenic contaminated soils.
Results from a feasibility study demonstrated that adequate leaching was possible using soil washing with sodium
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
48
-------
hydroxide. The arsenate in the soil washing leachate was then sorbed onto surfactant-modified zeolite (SMZ) under a
research program conducted by Los Alamos National Laboratory.
Long-term Stability
The technologies listed in the previous subsection have been used to treat wastes and environmental media containing
arsenic; however, many of the following statements refer to the treatment of arsenic-bearing wastes using S/S.
Test Methods: Many test methods can predict the performance of stabilized arsenic wastes. Some of the more com-
monly used methods include the TCLP, SPLP, and Multiple Extraction Procedure (MEP). There are several issues
associated with test methods used to demonstrate the long-term stability of arsenic wastes. First, long-term can be
used to refer to 10, 20, 100, or 1000 years; thus, a specific evaluation time period needs to be defined before a project
begins. While some test methods can attempt to "compress" a timeframe, there are problems associated with acceler-
ated testing. The effects of time on the stability of the treated wastes (i.e., how arsenic in the waste gets bound to the
material overtime) can be difficult to predict with these test methods.
The regulatory test method used to determine the suitability of applying stabilized arsenic wastes into a landfill is the
TCLP. Several concerns have been raised about the use of TCLP and the need for EPA to identify other tests that can
simulate long-term performance. Currently, there is no regulatory protocol that accurately simulates long-term stability.
There is a need for EPA to identify and provide test methods along with guidance protocols, which are notTCLP-based.
Follow-up from this workshop might include establishing a work group to investigate various leach methods that dem-
onstrate long-term stability. Dr. David Kosson at Vanderbilt University is working with a multinational group investigat-
ing various leach procedures. This group is an important knowledge base that can be used as a valuable resource.
New guidance protocols need to be established to address what works and does not work.
Data consistency can be challenging; comparing different test results from different sites can lead to misleading informa-
tion and conclusions. Test results can also have more than one use. SPLP, a commonly used leach test method, does
not have regulatory requirements, and there are no associated pass/fail criteria. However, SPLP results given in units of
concentration can be used as a performance specification for determining releases of stabilized arsenic wastes back
into the environment. The MEP is used to monitor long-term performance/stability and is typically not used as a field
specification. MEP results can show how arsenic speciation evolves over time. Soil tests should be conducted in order
to understand the soil characteristics of the site.
While long-term stability is an important concern, short-term effectiveness must also be considered. Short-term effec-
tiveness is determined through monitoring and periodic sampling. For example, during S/S, it is important to show
treatment effectiveness as soon as possible, requiring quick turnaround test results (i.e., in days).
Use of Models and Analogs: Models that predict thermodynamic and kinetic variables can also simulate long-term
conditions and can be used to determine if and when the arsenic becomes unstable and can leach into the environment.
Archiving samples at the start of the project for later testing for stability and leaching is another way of confirming
technology effectiveness.
The use of analogs, such as ancient concrete made with arsenic rich ash and other past markers of arsenic stability,
should be examined as a method for demonstrating the potential effectiveness of S/S treatment. Historic mine tailing
piles can be used as a source forthis kind of information. In Montana, core samples have been collected andgroundwa-
ter wells installed in old mine tailing piles at abandoned mine sites.
Disposal Concerns: It is important to consider the ultimate disposal of arsenic wastes; particularly, future exposure to
leaching agents. For example, decision makers remediating arsenic sites should, when possible, avoid placing stabi-
lized wastes in saturated zones. However, this may be difficult in areas exhibiting shallow watertables, such as Florida.
In response to the posed question "How are ideal treatment conditions maintained in orderto maintain long-term stability?"
capping arsenic contaminated sites is a viable consideration. Common practice has shown that treated material above a
certain action level is typically capped. There are many capping materials available now on the market. In addition, many
manufacturing by-products or off-products also make good capping materials. Capping specifications may be an impor-
tant issue when mining is eventually halted in Butte, Montana.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
49
-------
Current Advances
In order to understand how a technology works, it is important to understand how the contaminant reacts to its location
(e.g., biogeochemistry of the site). In the research and development arena, advances in techniques and instrumenta-
tion have allowed for greater site investigation. For example, molecular chemistry and X-ray diffraction often provide a
sound understanding of material microstructure. However, these advances have not yet been applied to field perfor-
mance specifications.
Currently, regulations do not distinguish between As(lll) and As(V) species. Historically, As(lll) has been considered
more toxic than As(V), and treatment strategies have focused on converting As(lll) to As(V) which is more amenable to
conventional treatment technologies. Arsenic toxicity is not well understood. Practitioners are still investigating the toxic-
ity of the different speciated forms.
3.2.1.1 Summary of Important Conclusions from the Treatment and Disposal Session
Long-term Stability
There is a need to:
1. Establish a regulatory protocol to simulate long-term conditions/performance.
2. Examine other protocols for simulating long-term conditions/performance including internationally applied meth-
ods.
3. Examine analogs that would simulate long-term conditions/performance (i.e., ancient concrete made with arsenic
rich ash, old mine tailing piles).
4. Examine mineral phases as arsenic speciation changes with time.
5. Consider the environment in which the waste/media will be ultimately disposed.
6. Consider both thermodynamics and kinetic issues with respect to long-term stability.
Current Advances
The EPA should:
1. Continue to develop and promote technology transfer
2. Develop and maintain a web-based bulletin board to facilitate the transfer of information
3. Form a partnership/consortium of stakeholders interested in arsenic-related issues
4. Establish cooperative links and partnerships with outside experts in academia, government agencies and public
sector groups, and conduct more pilot- and field-scale demonstration projects.
3.2.1.2 Recommendations or Research Needs from the Treatment and Disposal Session
Long-term Stability
1. A potential outcome from this work group is a consensus document, which details the types of methods that are
needed to demonstrate long-term stability for a waste.
2. EPA should revisit testing guidance and protocols.
3. EPA might consider conducting a comparative laboratory study of various test methods under a large number of
conditions.
Current Advances
1. Continue to research molecular arsenic chemistry, and leaching mechanisms, in order to develop a better under-
standing of site characteristics and applicable treatment technologies.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
50
-------
2. Develop a better understanding of the following arsenic treatment and disposal research issues: arsenic chemistry,
biogeochemistry, long-term stability, chemical speciation, microstructure/mineralogy, biological processes impact-
ing the mobilization of arsenic: bacteria, fungi, and plants, phytoremediation mechanisms, and arsenic toxicity.
3.2.2 Treatment and Disposal Session Speaker Abstracts
Speaker abstracts from the Treatment and Disposal session are presented in this section.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
51
-------
Treatment Technologies for Wastes and Environmental Media
Containing Arsenic
Peter J. Shields
TetraTech EM, Inc.
1881 Campus Commons Drive, Suite 200, Reston, VA 20191
T: 703-390-0659, F: 703-391-5876, E: shieldp(S)ttemi.com
Sankalpa Nagaraja
TetraTech EM, Inc.
1881 Campus Commons Drive, Suite 200, Reston, VA 20191
T: 703-390-0653, F: 703-391-5876, E: nagaras@ttemi.com
Linda D. Fiedler
U.S. EPA Office of Solid Waste and Emergency Response
Technology Innovation Office
(5102G) 1200 Pennsylvania Avenue, NW, Washington, D.C.
T: 703-603-7194, F: 703-603-9135, E: fiedler.linda@.epa.gov
Treatment of industrial wastes and environmental media containing arsenic has been conducted using a variety of
technologies. This presentation will discuss the contents of a white paper that summarizes technologies available to
treat wastes and media containing arsenic. The purpose of the white paper is to provide background material for a
discussion of: (1) the current state of treatment of wastes and environmental media containing arsenic, and (2) areas
where additional research may yield significant benefits.
The paper describes in broad terms the sources of waste and wastewater containing arsenic, with a focus on Resource
Conservation and Recovery Act (RCRA) hazardous wastes, mining waste, and industrial wastewaters regulated under
Clean Water Act (CWA) effluent guidelines. The treatment technologies selected for discussion include those most
commonly used and innovative technologies that appearto offer promising alternatives. The technologies include solidi-
fication/stabilization, recycling, vitrification, incineration, in situ soil flushing, soil washing/acid extraction, electrokinetics,
and phytoremediation for the treatment of non-wastewaters and chemical precipitation, ion exchange, carbon adsorp-
tion, membrane separation, foam flotation, and permeable reactive barriers forthe treatment of wastewater, groundwa-
ter, and drinking water.
The paper summarizes the following information for each selected technology:
Brief technology description
How the technology is used for treatment of wastes and media containing arsenic
Status of the technology and scale of its implementation (bench, pilot, or full)
Vendors that have used the technology to treat wastes or media containing arsenic
Available performance data (amount/type of wastes or media treated, and results of analyses for total and leach
able arsenic concentrations in untreated and treated waste)
Cost data for arsenic waste
The paper also compares the expected applicability and effectiveness of the selected technologies based on the type of
wastes or media treated, the concentration of arsenic, the presence of other contaminants that may interfere with
treatment, and other factors.
For more information about treatment technologies, see the following web site: http://www.clu-in.org/arsenic
52
-------
Treatment Options for Arsenic Trioxide Bearing Dust at the Giant Mine,
Yellowknife, Northwest Territories, Canada
N. A. Thompson and S. R. Schultz1
Department of Indian Affairs and Northern Development, Government of Canada
Box 1500, Yellowknife, Northwest Territories, Canada, X1A2R3
T: 867-669-2434, F: 867-669-2439, E: thompsonn@.inac.gc.ca
1SRK Consulting Inc.
Background
The Giant Mine, located in Yellowknife, Northwest Territories, Canada, has been operating as a gold mine since 1948.
Refractory ore containing arsenopyrite was mined from underground and roasted to facilitate the recovery of gold. The
roasting process produced arsenic trioxide bearing dust as a waste product, which was placed into underground storage
chambers at a rate of 10-13 tons per day. Fifty years of operation have resulted in approximately 265,000 tons of
arsenic trioxide bearing dust, stored in 15 underground chambers.
In 1999, Royal Oak Mines, Inc., the owner of Giant Mine, was placed in receivership and the property was purchased by
an existing Yellowknife mine operator. As a result, roasting operations were shut down and Giant Mine ore is now being
processed at another local mine. In orderto effect the sale, the federal government assumed liability for the pre-existing
conditions of the site, including the arsenic trioxide bearing dust stored underground. The mine is located within city
limits, and potentially significant environmental, public health and safety concerns exist.
Project Management
The Department of Indian Affairs and Northern Development, in its role as regulator and project manager, has been
working independently and with the mine's current owner to assess options for managing the dust stored underground.
Research has been initiated into: the hydrogeology and geochemistry of the mine; options for permanent underground
storage (freezing technology, in-situ stabilization, preferential groundwater pathways); methods of extracting dust from
the underground chambers; material re-processing for arsenic and gold recovery (hot water leach or sublimation); ar-
senic chemical stabilization (ferric arsenate using autoclave); and solidification/encapsulation (glass, bitumen or ce-
ment). By October 2001, the MacKenzie Valley Land and Water Board requires the submission of a Project Description
outlining an arsenic trioxide management plan forthe dust stored underground.
This presentation will examine the activities undertaken and issues faced in evaluating treatment processes forthe Giant
Mine arsenic trioxide project.
53
-------
Removing Arsenic for Mining Industry Waters, Treatability Studies,
and the EPA Mine Waste Program
J. McCloskey and Michelle Gale
MSE
200 Technology Way, Butte, MT 59702
T: 406-494-7262, F: 406-494-7230, E: jmcclosk(S)mse-ta.com
Dr. Larry Twidwell
Montana Tech
Three technologies were demonstrated and evaluated for arsenic removal and stabilization of arsenic byproducts. Each
technology was evaluated treating two separate industrial waste water streams. The baseline technology was ferrihydrite
precipitation with concurrent adsorption of arsenic onto the ferrihydrite surface. The two innovative technologies demon-
strated were: 1) an integrated adsorption membrane filtration process that used activated alumina and micro filtration;
and 2) a process called mineral like precipitation. Each of the technologies was evaluated for arsenic removal capabili-
ties, long term stabilities of byproducts produced, and process costs. The overall results will be presented and dis-
cussed. MSE Technology Applications, Inc. managed the project and demonstrated these technologies through the U.S.
Department of Energy (DOE) and Environmental Protection Agency's Mine Waste Technology Program under Inter-
agency Agreement Number DW89938513-01-0. Work was conducted through the DOE Federal Energy Technology
Center at the Western Environmental Technology Office under DOE Contract Number DE-AC22-96EW96405.
54
-------
Characterization of Arsenic in Refractory Gold Ores Roasting-Cyanidation Processing
Rong-Yu Wan1 and Tony Weeks2
Newmont Mining Corporation
1Newmont Malozemoff Technical Facility, 10101 E Dry Creek Road, Englewood, CO 80112
2NewmontTwin Creeks Mine Site, Golconda, Nevada 89414
PT Newmont Minahasa Raya, Indonesia operates a refractory gold-ore treatment plant. The deposit is predominately
refractory in nature. Extensive studies were performed to develop a process for gold recovery as well as detoxification.
The plant operation incorporates whole ore roasting followed by conventional cyanidation and carbon adsorption. The
tailings are treated to remove arsenic and other deleterious elements before disposal by submarine tailings placement
on the sea floor.
Development of the process for Minahasa was based on a detailed understanding of the ore characteristics. The gold is
finely disseminated and associated with fine-grained pyrite enriched in arsenic. A significant fraction of this As-rich
sulfide is fine-grained pyrite and is intimately intergrown with gangue minerals. Two different refractory ore types in the
deposit were characterized: siliceous pyritic and carbonate pyritic. Blending of siliceous and carbonate ores as roaster
feed gave two advantages: (1) the sulfur dioxide generated from roasting ofthesulfideswas captured by the decompo-
sition products of carbonate minerals, especially dolomite, and (2) the fixation of arsenic in calcine during roasting.
In the roasting reaction, arsenic-bearing pyrite was oxidized to SO2and As2O5. With decomposition of dolomite, arsenic
was fixed as magnesium (or calcium) arsenate in the calcine. Concentrations of arsenic in the gas stream directly after
roasting measured from 1 to 10 mg/Nm3, (equated as 0.03 to 0.30 % of the feed arsenic). The roaster off-gas was
treated in a wet scrubber and over 99.9 % of the arsenic was removed. The concentration of arsenic in the scrubber
outlet gas stream was below the detection limit. The soluble arsenic concentration in the calcine varied depending on
the ore minerals and roaster temperature. Plant monitoring indicated the soluble arsenic in the roaster products de-
creased with increasing roaster temperature. Extensive studies in the laboratory and plant trials were performed to
understand the chemistry and optimize the operation system for both gold recovery and arsenic fixation.
In the detoxification circuit, the low concentration of soluble arsenicwas precipitated with ferrous sulfate. Ferrous sulfate
is not the normal reagent of choice for precipitation of arsenic; ferric salt is more often used. However, the process being
operated is in alkaline slurry. With due regard for the upstream effect of plant operations on the arsenic chemistry, the
success of this treatment method can be explained by reference to well documented principles of precipitation of arsenic
(V) compounds. Based on thermodynamic considerations and test results, a minimum solubility for ferrous arsenic at pH
~8 has been reported. In consideration of an operating plant, ferrous sulfate has two distinct advantages over ferric
salts. Ferrous sulfate is cheaper on an available iron basis and is easier to handle, as it is less corrosive and toxic.
Tailings after detoxification are de-aerated and discharged on the sea floor below the natural ocean thermocline. The
long-term stability of metal ions is a concern, especially arsenic in seawater. Extensive large-scale static leach tests on
tailings in seawater have been studied. The static leach tests closely simulated the fluid dynamics of submarine dis-
posal, and provided an indication of the long-term stability of the tailings deposited on the ocean floor. Since the plant
startup, monitoring work, using sea floor coring methods, measurement of chemistry and turbidity in the water column
and measurement of heavy metals uptake in the predominate fish species, has confirmed that the submarine tailing
placement system is successful. No measurable changes in the seawater quality have been detected.
55
-------
Phytoremediation of Arsenic Contaminated Sites Using Brake Fern Hyperaccumulator
Lena Ma, Cong Tu, and Ken Komar
Soil and Water Science Department, University of Florida
Gainesville, FL 32611-0290
T: 352-392-9063, F: 352-392-3902, E: lqma(S)ufl.edu
Arsenic is of great environmental concern due to its extensive contamination and carcinogenic toxicity. There is a great
need for reliable and cost-effective technologies capable of reducing arsenic contaminated sites to environmentally
acceptable levels. Phytoremediation, a plant-based green technology, has been successfully used to remove contami-
nants from soils. However, no arsenic hyperaccumulating plant was available until recently. We have discovered an
extremely efficient arsenic-hyperaccumulating plant, Brake fern. A number of plant samples were collected from an
arsenic contaminated soil and analyzed for arsenic concentrations. In addition, plants after growing in artificially con-
taminated soils for up to 8 weeks in a greenhouse were harvested and analyzed for arsenic concentrations. The
highest arsenic concentration in the aboveground biomass in plants growing in the arsenic contaminated soil in the field
was 7,500 ppm, with the arsenic concentrations in aboveground biomass being up to 200 times greater than those of
soils. After 4 weeks, the arsenic concentration reached over 2.3% in the aboveground biomass of the plant growing in
the soil spiked with 500 ppm arsenic. Obviously, this plant has an extraordinary capability to uptake a large quantity of
arsenic from soils and translocate it to aboveground biomass (up to 90%). In addition to being effective in taking up a
large amount of arsenic into its aboveground biomass in a relatively short period of time from soils containing arsenic of
different concentrations and species, Brake fern also has many desirable attributes as a hyperaccumulating plant. This
plant thus has a great potential to be used for phytoremediating arsenic contaminated sites.
56
-------
In-Situ Chemical Fixation for Arsenic Remediation
and Arsenic Mobility Studies
James C. Redwine, Ph.D.
Southern Company Services, Inc.
P.O. Box 2625, Birmingham AL 35202
T: 205-992-6075, F: 205-992-0356, E: icredwin(S)southernco.com
The Electric Power Research Institute and the Southern Company are engaged in work that can significantly reduce
arsenic risk to the environment. In-situ chemical fixation (ISCF) for remediation and factors affecting arsenic mobility are
under investigation.
ISCF, an emerging technology, can render arsenic immobile at a reasonable cost. In ISCF, a liquid reagent (such as
ferrous sulfate) is applied to contaminated soil or aquifer media in place. Processes such as adsorption and precipitation
greatly reduce the solubility of the arsenic. The University of Alabama Department of Geological Sciences performed a
series of batch treatability studies using various mixtures of soil, water, and reagents, followed by optimized column
studies. Results from soil columns treated with ferrous sulfate showed dramatic decreases in leachable arsenic (both
TCLP and SPLP) as compared to untreated control columns; specifically, total leachable arsenic was reduced by a factor
of 200 to 1000 in the column studies. Afield demonstration is currently underway to determine the effectiveness of ISCF
in the field. Costs are expected to range from $20 to $40 per cubic yard treated.
The published arsenic literature indicates that many variables may influence arsenic mobility in soil and aquifer media.
Significant parameters include pH, redox potential, carbon content, iron and other metal oxides and hydroxides, anion
and cation exchange capacity, arsenic concentration, and grain-size distribution (particularly fines). These parameters
will be tested in both batch and column studies in the laboratory, and the relative importance of each variable will be
determined. In addition, distribution coefficients (Kds) necessary for fate and transport modeling will be calculated.
57
-------
Arsenic Contamination in Soil and Groundwater: Review of Remediation Results
R. M. Markey
Gulf Power Company
Pensacola, FL 32520-0328
E: RMMARKEY@southernco.com
D. Leszczynska and A. Dzurik
Department of Civil and Environmental Engineering, Florida State University
Tallahassee, FL 32310
E: Danuta(S)eng.fsu.edu and Dzurik(S)ena.fsu.edu
Arsenic contamination is a prevalent problem throughout the world, including countries such as Bangladesh and the U.S.
These problems exist in other countries due to naturally occurring arsenic and past use of arsenic for pesticides, herbi-
cides, mining wastes and other miscellaneous uses.
Water and soil treatment methods exist to clean up these anthropogenic or natural sources of arsenic. Several success-
ful methods for soil remediation consist of excavation, soil solidification/stabilization, and soil flushing/washing. Suc-
cessful water treatment methods for arsenic consist of iron coprecipitation with soil flushing, lime precipitation, activated
alumina and reverse osmosis. Promising technologies, which can be utilized for both soil and water contamination, are
phyroremediation and electrokinetics.
In orderto evaluate existing remediation methods, an economic analysis and performance evaluation was conducted. In
addition, the final document entitled "Comparison and Economic Analysis of Arsenic Remediation Methods Used in Soil
and Groundwater" discussed case histories utilizing various technologies as well as the initiation of a website for arsenic
remediation. This website can be found on the FAMU-FSU College of Engineering webpage.
58
-------
The Cement Stabilization and Leaching of Arsenic
M. Leist1, R. J. Casey, and D. Caridi
School of Life Sciences & Technology, Victoria University
Footscray Park Campus (F008), PO Box 14428, MCMC, Victoria 8001, Australia
1Varian Australia, Research & Development Department
679 Springvale Road, Mulgrave, Victoria 3170, Australia
T: +61 3 9566 1418, F: + 61 3 9560 7950, E: M.Leist@osi.varianinc.com
Arsenic has found widespread use in agriculture and industry to control a variety of insect and fungicidal pests. Most of
these uses have been discontinued, but residues from such activities, together with the ongoing generation of arsenic
wastes from the smelting of various ores, have left a legacy of a large number of arsenic-contaminated sites. To date a
wide range of arsenic stabilization formulations have been used in an attempt to successfully fix arsenic. These have
included mixing the arsenic waste with:
Cement
Lime
Aluminum or iron hydroxides
Silicates
Fly ash
Or combinations thereof.
Despite the research that has been conducted, it is difficult at present to gauge just which of the stabilization formula-
tions is the most effective. This is due to a number of factors that include:
The diverse range of arsenic compounds and oxidation states that can be encountered as arsenic waste
The varying additive-to-waste ratios that have been utilized
The different leaching tests which researchers have used to access the leachability of the treated waste
In this study, arsenic compounds in both of the common oxidation states have been stabilized using various cement-
based formulations. Each of the formulations investigated contained near identical arsenic loadings and their success
was determined by utilizing a number of leaching tests, which have included:
Bottle leach tests
Sequential leach tests
Column leach tests
The results of this research will lead to more appropriate waste disposal management by:
1) Providing conclusive results on the success of a range of solidification/stabilization procedures, which will be appli-
cable to the hundreds of tonnes of arsenic containing wastes,
2) Comparing and contrasting the results obtained from the numerous leach tests.
59
-------
Characterization and Treatment of Arsenic Contaminated Soils:
The DuPont Experience
I. A. Legiec, Ph.D.
DuPont
Jackson Lab, Chambers Works, Deepwater, NJ 08023
T: 856-540-4912, F: 856-540-4961, E: Irene.a.legiec-2@.usa.dupont.com
Thorough characterization of complex soil matrices can provide information on chemical speciation, mobility, and distri-
bution through the soil, thus enabling the project team to develop the most technically feasible, cost effective technolo-
gies that are protective of human health and the environment. Soil characterization studies can provide the fundamental
information necessary to consider the feasible options for a site. The screening and final selection of remediation
technology is impacted by many factors such as regulations, clean-up goals, final site end-use and other project strate-
gies/goals. Scientific and engineering data generated through soil characterization can be very useful in guiding the
technology screening and development process. Based on a solid foundation of information, carefully designed treat-
ability and/or field pilot testing can be used to evaluate promising remediation technologies. Treatability studies should
be used to examine the technology-specific design and operating conditions and develop preliminary cost/performance
data.
This presentation will highlight a previous case study involving soil characterization and treatment of arsenic contami-
nated soils (Legiec et al., 1997). Detailed soil characterization studies included particle size distribution, sequential
chemical soil extraction, leaching and mobility testing, scanning electron microscopy, and XRF analyses. Results
indicated that the arsenic was primarily associated with the organic fraction and the iron oxide/manganese oxide fraction
of the soil. A phased approach was developed to evaluate the feasibility of arsenic leaching. This preliminary treatability
study demonstrated that alkaline leaching of arsenic was possible and provided information towards scale-up of the
process.
Finally, a brief overview will be provided to highlight the current research and competency building activities within
DuPont, such as metals fate and transport, including biogeochemical reactions, biogeochemical modeling, and treat-
ment.
Reference
Legiec, I .A.; Griffin, L.P.; Walling, P.O.; Breske Jr.,T.C.;Angelo, M.S.; Isaacson, R.S., and Lanza, M. B. "DuPont Soil
Washing Technology Program and Treatment of Arsenic Contaminated Soils", Environmental Progress, Vol. 16, No. 1,
Spring 1997, pp. 29-34.
60
-------
Sorption of Arsenate from Soil-Washing Leachate by Surfactant-Modified Zeolite
E.J.Sullivan
Los Alamos National Laboratory
E-ET Division, MS J514, Los Alamos, NM 87544
T: 505-667-2889, F: 505-665-9118, E: ejs@Janl.gov
R.S. Bowman
New Mexico Institute of Mining and Technology, Socorro, NM 87801
T: 505-835-5992, E: bowman@nmt.edu
I.A. Legiec
DupontCR&D, Experimental Station, P.O. Box 80304, Wilmington, DE 19880
T: 303-695-1810
Surfactant-Modified Zeolite
Surfactant-modified zeolite (SMZ) is an effective and economical sorbent for nonpolar organics, inorganic anions, and
inorganic cations dissolved in water (Haggerty and Bowman, 1994; Bowman et al., 1995). Due to its low unit cost of
about $400 per ton, SMZ is an attractive alternative to activated carbon and ion exchange resins. Oxyanions that are
sorbed by SMZ include chromate, nitrate, selenate and sulfate (Bowman etal., 1995; Lietal., 1998). SMZ was tested in
batch studies to remove arsenate from a leachate generated during a soil-washing treatability study. The SMZ was
prepared from a pure clinoptilolite zeolite from the St. Cloud mine in Winston, New Mexico. The raw zeolite was treated
with hexadecyltrimethylammonium bromide (HDTMA-Br) surfactant to a level of 150 meq/kg (42.6 g HDTMA per kg of
zeolite). The surfactant forms a stable organophilic coating on the zeolite surface. Further details on the preparation and
properties of SMZ are found in Haggerty and Bowman (1994).
Soil Leachate Characteristics and Treatment
Soil washing is an ex-situ remediation treatment technology that utilizes wet classification, mechanical separation, and
chemical extraction processes to remove contamination from soil. Byproducts include fluids or a concentrated residue
containing high concentrations of contaminants, fine particulates, and organic carbon. A synthetic soil leachate was
prepared from Kennet "A" glacial till-type soil. Clean soil (5x150g)was leached with 750 ml of 0.1 N NaOH solution (pH
>14) to yield a humate-rich solution. The leachate fractions were combined and diluted to 6 L with deionized water,
filtered, then spiked with As2O52- as the sodium salt to approximately 500 mg/L as arsenic. Batch isotherms using
variable leachate:SMZ ratios from 40:1 to 4:1 were runatpH 12 and two temperatures, 25°C and 15°C, respectively. The
supernatants and solids were analyzed using EPA methods 7060 (dissolved and total solution arsenic), EPA Method
7060 with digestion (total arsenic-solid fraction), and EPA Method 9060 (TOC).
Results
Dissolved versus total arsenic results were similar. At each temperature, sorption reached a plateau or maximum, then
decreased at the highest solution concentration (corresponding to the lowest amount of zeolite added, 2.5g). Sorption
maxima of 5540 mg of arsenic per kg of SMZ were observed at 25°C, and 3150 mg at 15°C. Total arsenate recoveries
varied from 74% to 125%. SMZ effectively decolorized the leachate solutions, proportional to the amount of SMZ. The
maximum TOC removed varied from 94 to 97 percent. The linearized form of the Langmuir equation was fitted to the As
data, with a coefficient of determination of 0.997 for the 25°C batch (0.906 for the 15°C batch). Sorption of arsenate
likely results from two mechanisms: anion exchange with bromide on the external portion of the surfactant bilayer on the
zeolite surface, and adsorption of organically complexed arsenate via hydrophobic interactions with the surfactant moi-
ety at the zeolite surface.
References
Haggerty, G.M, Bowman, R.S., 1994. ES&T, 28, 452-458.
61
-------
Bowman, R.S., Haggerty, G.M., Neel., D., Flynn, M., 1995. ACS Symposium Series 594, pp.54-64.
Li,Z.,Anghel, I., and Bowman, R.S., 1998. J. Dispersion Science and Technology, 19(6&7), 843-857.
62
-------
Adsorption and Nanoscale Magnetic Separation of Heavy Metals from Water
James D. Navratil
Clemson University, Environmental Engineering and Science
342 Computer Court, Anderson, SC 29625-6510
T: 864-656-1004, F: 864-656-0672, E: nav@.clemson.edu
One of the primary needs of mankind overthe next millennium is improved and less expensive water treatment methods.
Recent efforts by the U.S. Environmental Protection Agency (EPA) have focused on reducing the concentration levels of
arsenic in drinking and wastewater treatment plants. Thus we are developing a new and inexpensive magnetic filtration/
adsorption technology for purifying water supplies that is not only in line with mankind's future needs, but may also
alleviate the problems with arsenic identified by EPA. This nanolevel high gradient magnetic separation (HGMS) process
is based on the use of a supported surface complex adsorbent such as natural magnetite (FeO Fe2O3) in a fixed bed
mode (Kochen and Navratil). Due to its ferromagnetic property, magnetite can be used not only as an adsorbent for
removing toxic metals from solution, but also as a magnetically energizable element for attracting and retaining para-
magnetic nanoparticles, thus removing them from solution. In such a system, the inexpensive magnetite serves as a
metal ion adsorbent, high gradient magnetic filter, or both, depending on the characteristics of the aqueous stream to be
purified.
Reference
Kochen, R.L. and Navratil, J.D. "Removal of Radioactive Materials and Heavy Metals From Water Using Magnetic Resin,"
U.S. Patent5,595,666.
63
-------
3.3 Arsenic Chemistry Session
This session was designed to allow further discussion of the chemical fundamentals related to arsenic chemistry, spe-
ciation, and analytical issues, and to develop conclusions about the current state of knowledge and recommendations
for further research. The session co-chairs were:
Robert Ford, Environmental Scientist -U.S. EPA, NRMRL
Kirk Nordstrom, Chemist - USGS
The objective of the Arsenic Chemistry session was to address three general questions:
1) Is our knowledge of arsenic speciation and transformation adequate to identify pathways and routes of mobility?
2) Are current collection, preservation, and analytical techniques sufficient for defining arsenic chemistry in natural
and engineered systems?
3) Are existing leach procedures adequate for assessing the stability of arsenic-bearing waste materials?
Speaker Abstracts
Speaker presentations were first made forthe subject areas of arsenic (bio)geochemistry, analytical characterization of
aqueous and solid phase arsenic, and leach procedures for arsenic solid waste. The abstracts for these presentations
are located in section 3.3.2 of this report. The presentations and arsenic chemistry issues were then discussed by the
session participants in order to address the three session questions. The discussion is reviewed in section 3.3.1.
3.3.1 Discussion Review
Identifying Pathways and Routes of Mobility
Geochemical Factors: Afield case study was reviewed to highlight the importance of understanding the relationships
between chemical cycling of elements such as carbon, iron, nitrogen and sulfur and the redox speciation of arsenic. The
distribution of arsenic species [As(lll) and As(V)] and aqueous and solid phase iron between lake sediments and lake
water was investigated. Data showed that conversion of As(V) to As(lll) was spatially and temporally correlated with
zones of nitrate (NO3) depletion (anoxic or reducing zones). Data also showed that either NO3 or As(lll) would dominate;
they do not coexist. Spatial and temporal trends in NO3andAs(lll)/As(V) concentrations indicated that NO3 (not O2) was
the primary oxidant of As(lll). In addition, in this environment it was possible to predict the partitioning of arsenic to
hydrous iron oxides precipitated in the water column using published sorption constants. However, biological activity
can disrupt the chemical equilibrium.
This study determined that the aqueous and solid phase arsenic speciation was mediated by reaction with nitrate and
iron precipitation-dissolution processes, respectively, in anoxic lake water. These observations are significant for water-
logged agricultural soils (oxygen deficient), where arsenic may remain in an oxidized and less mobile state due to the
influence of high concentrations of NO3. However, elevated phosphate levels introduced during agricultural operations
will also influence arsenic mobility. Therefore, as part of any effort to understand arsenic fate and transport on a water-
shed scale, we need to consider the influence of nutrients such as nitrate in addition to the chemical relationships with
iron and sulfur compounds that are commonly assumed.
Microbial Factors: The role of the microbial community in arsenic cycling is in the early stages of evaluation. The
specific microbial community may have a large impact, but it is hard to extrapolate to a large-scale system. There is a
need for better ways of measuring microbial activity in the field. Currently, redox parameters and carbon dioxide produc-
tion are utilized, but these parameters are not enough to fully characterize the microbial activity. A "leave in place"
measuring system would be very useful. Also, it may be possible to use RNA for identification of the microbial commu-
nity. Our current scientific understanding indicates that microbial communities can exert both a direct and indirect
influence on arsenic chemistry, but there is no quantitative foundation to aid prediction of this influence on spatial or
temporal scales relevant to site assessment.
Modeling Fate and Transport: Applications for modeling chemical controls on arsenic solubility through solid phase
precipitation were reviewed. Thermochemical analysis was used as a tool to evaluate potential routes for optimizing
arsenic immobilization in treated solid wastes. Model chemical systems were constructed using relevant salt solutions
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
64
-------
in equilibrium with atmospheric carbon dioxide and assuming possible equilibrium with one or more minerals. The
hypothetical chemical systems were allowed to approach equilibrium based on constraints imposed by the free ener-
gies of formation for all components, phase rule restrictions, and the balance of mass and charge. Arsenic solubility
was evaluated as a function of various system chemical parameters. This analysis did not incorporate adsorption to
other solids present at equilibrium as a possible control on arsenic solubility, and thus should be viewed as an initial
approximation. The point was raised that many chemical equilibrium models do not have an adequate database that
includes solubility data for relevant arsenic-bearing solids.
Computational chemical models can be used to help understand arsenic fate and transport. Two models that were
discussed included MINTEQA2 and PHREEQC, which are supported by EPA and USGS, respectively. The MINTEQA2
model is a geochemical equilibrium speciation model that can be used to calculate the equilibrium composition of dilute
aqueous solutions in natural aqueous systems, and the equilibrium mass distribution among dissolved species, adsorbed
species, and multiple solid phases under a variety of conditions. However, MINTEQA2 does not handle species trans-
port problems. PHREEQC is also a geochemical equilibrium model that can perform one-dimensional transport calcula-
tions and is also used for speciation, batch-reaction, and inverse geochemical calculations. It was emphasized that the
user needs to determine what questions should be answered before selecting and applying a model. Also, data inputs
need to be defined including relevant aqueous and solid phase parameters and the acceptable level of uncertainty in
results.
One of the greatest shortcomings identified with the use of off-the-shelf computational chemical models was the inad-
equacies and inconsistencies in the associated database. For instance, a model database may lack data required to
account for reactions between contaminants of concern and common aqueous and solid phase constituents in soil and
sediment systems. Therefore, the users may have to add data or customize the model fortheir application. There is no
"canned" package for arsenic modeling. In addition, existing model databases may need to be updated or revised to
include more current thermochemical data. While most databases are generally complete with respect to the descrip-
tion of aqueous speciation and solid phase precipitation reactions, there is much less consistency in the data available
to support calculation of reactions describing sorption of aqueous constituents to solid surfaces. The database associ-
ated with PHREEQC is considered to be good, but the USGS needs additional funding to improve this database.
MINTEQA2 is a regulatory accepted model, but it is currently not well maintained by EPA and should be used with
caution.
There is no scientific consensus on the appropriate use of existing models to quantitatively describe sorption reactions
in complex systems. Data available in the literature may be derived either from: 1) whole soil/sediment experiments or 2)
studies that approximate system behavior by employing a predominant reactive solid phase (e.g. an iron oxide mineral).
Data derived using the first approach may result in the most reliable site-specific data, provided experiments are con-
ducted on a statistically representative set of solid phase samples. This will likely require added time and cost associ-
ated with site or system assessment. There are much more data available in the literature derived using the second
approach, but the application of these data to heterogeneous media (soils and sediments) is not reliable. It is recom-
mended that the user employ site-specific conditional constants and evaluate model results in the context of soil/sedi-
ment characterization data, e.g., mineralogy, organic matter content, surface area. Since soils/sediments and engi-
neered treatment systems rarely achieve a state of chemical equilibrium, it is also recommended that the user consider
the kinetics of chemical reactions relevant to contaminant speciation in their system.
Quantifying Arsenic Exposure and Uptake: A case study was presented to evaluate issues of site characterization
and risk assessment with respect to the potential exposure to and uptake of arsenic from anthropogenic sources.
Principal components analysis was used to determine the origins of arsenic in soils and sediments related to historic
and recent gold mine operations in Yellowknife, Northwest Territories, Canada, and to establish cleanup criteria. The
cleanup guideline for arsenic in soil is 12 mg/kg, however, natural arsenic background levels in this area ranged from 3
to 150 mg/kg. Plants and fish were also analyzed for total, extractable, and water-soluble arsenic species. Significant
arsenic levels were found in freshwater (lake) fish, which normally have much lower arsenic levels than marine fish.
These data should be considered in establishing soil and sediment cleanup levels.
Extraction studies were performed to examine arsenic uptake and bioavailability in fish. Most of the arsenic was not
extracted, and it was therefore not considered to be bioavailable. Acute arsenic toxicity is due to organic arsenic (arsenine),
while carcinogenicity is primarily due to As(l 11) and As(V) species. Methylated forms of arsenic are generally genotoxic.
There are currently no good animal carcinogenicity models. There is also a lack of knowledge of the true bioavailability
of arsenic to human and other receptors. The standard uptake of arsenic in tissues has not been looked at closely.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
65
-------
Field-Scale Application: Site assessment of arsenic chemistry, cycling, and exposure was discussed. A site-by-site
approach to evaluation/assessment may be needed because it is not realistic to use the same approach for every site
due to hydrologic and chemical heterogeneities. An iterative approach to site evaluation may be practical. Arsenic
mobility and transport must be understood, and there should be a focus on key parameters that control arsenic chemis-
try for different contaminated media. To obtain this information routinely, the use of standard and easy to implement
sampling and analytical methods is needed. There is a lack of standard procedures for some methods, and some site
characterization methods may require specially trained personnel.
It may not be necessary to do a detailed site assessment if the site contamination is well documented and remediation
is straightforward. The evaluation of long-term implications of site contamination or a complex site is more difficult and
may require the assistance of an expert. For example, to evaluate a landfill, it may be necessary to treat it as a bioreactor,
do a simulation, and look at releases. These results could be compared to other landfill results to develop fate and
transport patterns. Using only direct analytical parameter measurements may not be enough to characterize this type of
site.
Sampling and Analytical Techniques
Three principal strategies currently employed for the measurement of arsenic speciation in waters were discussed: 1)
field speciation using solid-phase cation and anion exchangers; 2) EPA Method 1632 using batch (selective) hydride
generation (HG-CT-GC-AAS); and 3) ion chromatographic separation coupled with an element-specific detector (e.g.,
ICP-MS). All three methods have advantages and disadvantages concerning issues such as species quantification or
exclusion, identification of inorganic versus organic species, interferences, and identification of additional elements.
Sample dilution can be used to overcome analytical interference problems, but there is a possibility of changing the
speciation either by addition of oxygen or other modifications to the sample chemistry. The field speciation technique
works well for clean oxic waters and no additional specie-specific preservation is needed. However, this technique may
be susceptible to As(V) breakthrough, potentially resulting in incorrect speciation patterns. Method 1632 is good for oxic
waters. It provides low detection limits, but As(V) must be quantified by difference, an indirect approach. The chroma-
tography method produces good speciation and direct quantitation of As(V). It has higher detection limits than Method
1632, but is usually adequate. Table 3.3-1 provides a comparison of the advantages and disadvantages of the three
principal methods (Frontier Geosciences, Inc. 2001).
Preservation of water samples is important in order to maintain the natural distribution of arsenic species during sam-
pling and storage. Preservation techniques include acidification and cryogenic freezing, although acidification is the
most common and cryogenic freezing is not recommended if there is a potential for the dissolved phase to develop
particulates from precipitation upon thawing. Sample oxidation can be a problem, but this factor can be minimized
through acidification. Samples should be stored in the dark to prevent light-induced transformations, and filtered to
remove microbes. Based on a recent study, there is some question about whether the EPA-specified 6-month holding
period for metals is acceptable if oxidation is a concern. The general rule of thumb is to analyze samples as soon as
possible, especially when samples are known to have low arsenic concentrations and/or a difficult sample matrix.
Collection vessels for water samples should be of FEP teflon or low-density polyethylene materials.
Speciation of Toxicity Characteristic Leaching Procedure (TCLP) leachate samples may be problematic because of the
complicated sample matrix. In addition, the leach process may modify the actual speciation; therefore, speciation of
leaching samples may not be useful for evaluation of potential arsenic mobility. However, in-situ leachate fluid samples
collected using devices such as soil lysimeters may be amenable to arsenic speciation by the principal methods.
For characterization of solid phase arsenic speciation, accurate identification of the arsenic solid phase association is
dependent on the use of collection and storage techniques that preserve the in-situ physicochemical state of the sample.
For example, samples collected from a reduced environment will react with oxygen in the atmosphere, thus altering
sample mineralogy and arsenic phase association. The presence of arsenic within a discrete solid phase may be
identified through evaluation of mineralogy using optical/electron microscopy and/orX-ray diffraction. More commonly,
solid phase associations are established through identification of correlations in element composition. These associa-
tions may be established via characterization by X-ray fluorescence spectroscopy, a non-destructive method that is
generally not as susceptible to matrix interference, or by determination of element content following chemical dissolu-
tion.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
66
-------
Table 3.3-1 Arsenic Speciation Method Comparison
Issues:
Detection limits
Preservation issues
Chemical interferences
Chromatographic interferences
Spectroscopic interferences
Direct quantification of As(V)
As(lll)/As(V) Issues
Problems with
methylated species
Suitability For:
Particulate speciation
Other As species
Sulfidic waters
Saline waters
Clean surface waters
Field Speciation
Good
Storage?
Pre-concentration?
Probably
Pre-concentration?
Possible
No
Maybe
No
No
No
No
Yes
Method 1632
Very good
Storage
Few
No
Yes
No
Yes
Yes
Possible
No
No
Yes
Yes
ICP-MS
Very good
Storage +
analysis
Few
Yes
No
Yes
No
No
No
Yes
Yes
No
Yes
Leaching Procedures for Characterization
This discussion focused on best methods to evaluate arsenic leachability from contaminated soil and treated solid
water prior to and following disposal. Relevant applications for leaching procedures include:
Hazard classification (TCLP)
Evaluation of treatment process effectiveness
Evaluation of waste management options
Evaluation of remediation endpoints
Evaluation of source term for contaminant release
Protocols for estimating arsenic leaching from soils and solidified wastes were evaluated to estimate impacts from
different waste management scenarios and to compare treatment processes. These protocols included the use of
percolation and flow-around models to assess the long-term release of the contaminant from the waste material. This
approach provides a method to estimate long-term environmental impacts from leaching and to compare the efficacy of
waste treatment processes. The site-specific liquid-to-solid ratio and mass release can be estimated with the percola-
tion method. Local pH can be a limiting factor, however. With the flow-around method, mass transport within the solid
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
67
-------
matrix is rate limiting. Fundamental leaching parameters evaluated for equilibrium-based leaching tests include con-
stituent availability, acid neutralization capacity of the waste, and liquid-solid equilibrium solubility. For mass transfer-
based leaching tests, constituent release rates should be evaluated. Study results indicate that these fundamental
leaching parameters can be used to compare the effectiveness of different waste treatment processes. A more robust
evaluation can be used for waste management decisions and to reduce overall costs while maintaining environmental
protection.
Other research that was reviewed included comparison tests that were conducted to evaluate the utility of the EPA
Toxicity Characteristic Leaching Procedure (TCLP) and the California Waste Extraction Test (WET) for characterizing
the leachability of municipal and hazardous solid waste. The primary difference between these two leach procedures is
that the TCLP uses acetate (acetic acid) as the leaching medium, while the WET uses citrate (citric acid). (Citric acid
chelates arsenic better than acetic acid, and thus makes arsenic more mobile.) Initial results showed higher leachate
concentration results from the WET than the TCLP. WET is a more aggressive leach test for arsenic and other constitu-
ents. Comparison of measured arsenic concentrations for a municipal solid waste leachate database showed that
arsenic leachabilty data derived from the WET correlated better than TCLP data.
For evaluation of site contamination, in-situ vadose zone sampling may be used as an alternative to performing simu-
lated leaching tests on collected soil samples. This method involves use of pressure/vacuum lysimeters for collection of
soil moisture (water) in the vadose zone. The lysimeters utilize ceramic cups and inert atmosphere sampling to help
determine actual arsenic mobility. It has been found that core sample soil analysis can often show high levels of (adsorbed)
arsenic or other metals, but collected interstitial soil pore water may still have very low concentrations. Arsenic in the
interstitial water represents the highly mobile contaminant phase. The soil lysimeter approach is best for evaluating in-
place source waste leaching. It is not as useful for characterizing treated waste leachability prior to disposal. Soil
lysimeter sampling can be performed at various depths and under different site conditions (wet, dry, etc.) to account for
variables that may affect soil water concentrations. Field research has shown that sites can have significant variability in
spatial sampling results.
Parameters for Site Characterization
Based on information generated during discussion of the previous arsenic chemistry topics related to the three general
questions, parameters for site characterization were evaluated for aqueous and solid phases. It is important to deter-
mine in advance the intended use of site characterization data and what level of characterization is needed to guide the
field investigation. The required parameters will vary from site-to-site due to site history, site conditions, and questions
to be answered. Some measurements may be needed to understand site conditions beyond the arsenic species present.
Table 3.3-2 presents a summary of recommended parameters that may be necessary to provide a general character-
ization of an arsenic contaminated site, to determine if arsenic is being mobilized into groundwater, and to determine
what biogeochemical processes are controlling arsenic mobilization. Not all of these parameters may be necessary at
a given site, but they provide a good starting point for site evaluation. Dependent on the availability of site data, a
stepped approach that includes periodic re-assessment of the required characterization effort may prove most practical
and cost-effective.
3.3.1.1 Summary of Important Conclusions from the Arsenic Chemistry Session
Identifying Pathways and Routes of Mobility
1. Arsenic speciation and partitioning are commonly coupled to the cycling of redox sensitive elements such as iron,
sulfur and manganese.
2. Arsenic speciation and partitioning are apparently linked to nitrogen transformations. Therefore it may be impor-
tant to examine nutrient cycling during site assessment.
3. Microbial activity may exert direct and indirect influence on arsenic speciation, but predictive tools and modeling
approaches to determine this influence are in their infancy.
4. The sophistication of chemical models is generally greater than commonly available field data and existing thermo-
dynamic and kinetic data. Sorption modeling is limited by lack of: 1) a consistent set of model parameters for oxic
systems, and 2) data for sorbents common to anoxic environments.
5. There is uncertainty about potential soluble inorganic complexes of arsenic relevant to suboxic or anoxic systems,
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
68
-------
Table 3.3-2 Recommended Site Parameters for Characterization of Arsenic Contamination and Mobility
Aqueous Phase
Solid Phase
PH
temperature
specific conductivity
dissolved oxygen
alkalinity (full titration curve)
oxidation reduction potential (ORP) - an op-
tional indicator measurement using platinum
electrode
arsenic speciation
dissolved organic carbon (DOC)
major anions - SO4, NO3, Cl, HCO3/CO3, PO4,
major cations - Na, K, Ca, Mg, Al, Si (more
anions and cations may be needed to provide
charge balance, which is required for chemical
modeling)
redox indicators - Fe(ll)/Fe(lll), As(lll)/As(V),
arsine, NO3/NO2/NH4, HS/SO2/SO3, CH4, H2,
Mn(ll) filtered and unfiltered
trace metals - Cr, Cu
Note: Aqueous samples should be tested as
unfiltered and filtered (0.1 urn) for major anions
and cations and the contaminant(s) of concern
Natural
total arsenic
organic carbon
anion exchange capacity
grain size distribution
mineralogy
lithology
hydraulic conductivity
extraction/leach test or solubility versus pH
Note: If used, the leach test should mimic site
geochemistry. The solubility versus pH assess-
ment should use a pH range representative of
site water.
Anthropogenic
total arsenic
matrix identification
site history (disposal, contamination, waste
age, etc.)
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
69
-------
such as complexes incorporating carbonate orsulfide.
Sampling and Analytical Techniques
1. Existing analytical instrumentation appears adequate for determination of aqueous arsenic speciation; however, no
single method for preservation and analysis is appropriate for all sample matrices.
2. Filtration, acidification, and light exclusion are the most critical issues for sample preservation and handling. The
techniques used should be customized to the type of sample and analytical needs, such as speciation.
3. Sample matrices that can cause analytical problems include high dissolved organic carbon, ferrous iron, and sul-
fide.
4. Current analytical approaches may inadequately describe inorganic arsenic speciation in anoxic environments.
5. Analytical limitations of EPA Method 1632 are a potential source of inaccurate species identification orquantitation.
This method requires very good laboratory expertise to get correct results.
6. Strategies for preservation and species separation need to consider the sample matrix. For example, acidification
may be beneficial with Fe(ll), but detrimental with sulfide.
Leaching Procedures for Characterization
1. TCLP may be inappropriate as a stand-alone test for evaluation of arsenic bearing materials. Sometimes, how-
ever, a combination of leach tests may be desirable.
2. The most appropriate leaching method to use may differ for the pre- and post-disposal setting.
3. The influence of waste material age with respect to long-term arsenic stability and partitioning to natural solids is
poorly understood.
3.3.1.2 Recommendations or Research Needs from the Arsenic Chemistry Session
Identifying Pathways and Routes of Mobility
1. Initiate an effort to develop and disseminate a consolidated thermochemical database with consistent parameters
for use in modeling applications.
2. EPA has a responsibility for providing adequate computer models to evaluate arsenic mobility. EPA should update
and maintain the MINTEQA2 model database and develop a website to provide users with access to arsenic chemi-
cal speciation models and application information.
3. Produce guidance outlining uniform strategies for implementation of sorption modeling.
4. Produce guidance on uniform approaches for site assessment.
5. Evaluate methods for measuring microbial activity in the field. Determine what measures are valuable for interpret-
ing the impacts of microbial activity on arsenic mobility.
Sampling and Analytical Techniques
1. Operational protocols tailored towards specific sample matrices need refinement and development.
2. Document limitations and strengths of various analytical approaches relative to different sample matrices and the
desired data output.
3. Evaluate and provide guidance for approaches to preserve speciation for oxic and anoxic sample matrices during
sampling and storage (holding time).
4. Develop a more comprehensive understanding of analytical requirements in anoxic or suboxic environments repre-
sentative of many disposal scenarios.
Leaching Procedures for Characterization
1. Design leach procedures based on information needs, such as waste classification versus source term evaluation.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
70
-------
2. For assessment of leach potential, design the leach procedure to be more representative of the in-situ environ-
ment, including:
Solubility over a range of pH inclusive of natural pH of material and pH range of in-situ environment
Consistent with site geochemistry (based on site characterization)
Measure in-situ concentrations in contact with the source (e.g., pressure/vacuum lysimeter)
3.3.2 Arsenic Chemistry Session Speaker Abstracts
Speaker abstracts from the Arsenic Chemistry session are presented in this section.
Note: Statements captured in the panel discussion are those of participants, not necessarily EPA.
71
-------
Interactions of Arsenic Speciation with the Nitrogen Cycle
Harry Hemond
Massachusetts Institute of Technology
48-311, Cambridge, MA 02139
T: 617-253-1637, F: 617-258-8850, E: hfhemond@mit.edu
The speciation of As in freshwaters is strongly influenced both by redox potential and by the presence or absence of iron
oxyhydroxides. Recent work in Upper Mystic Lake, located on the Aberjona River watershed near Boston, MA has
shown that these characteristics can both be controlled by nitrogen during a substantial part of the year. In this eutrophic
urban lake, total nitrogen (nitrate plus ammonium) concentrations typically exceed 100 micro-equivalents per liter, and
nitrification represents a major hypolimnetic oxygen demand following onset of seasonal stratification. Later during the
period of stratification, following oxygen depletion, nitrate controls the redox potential of the bottom waters and is
responsible for reoxidizing ferrous iron as it diffuses from the lake sediments into the hypolimnion. It is also suspected
that nitrate is concurrently responsible for the reoxidation of As(lll) to As (V). Consequently, As is present chiefly in
particulate form, its speciation dominated by surface complexation of As(V). The conclusion that nitrogen is the control-
ling factor is supported by clear spatial and temporal correlations, as well as by thermodynamic arguments, mass
balance data, and microcosm results. We argue that in eutrophic freshwaters, nitrogen can thus take on a chemical role
analogous to that played by molecular oxygen as a key controlling factor in the cycling and speciation of As and probably
many trace metals.
72
-------
Arsenic Immobilization: Thermochemical Analyses
Spencer K. Porter
USEPA
Center Hill Lab, 5995 Center Hill Drive, Cincinnati, OH 45224
T: 513-569-7851, F: 513-569-7879, E: porter.spencer@epa.gov
The possibility of putting arsenic into slightly soluble minerals is examined by thermodynamic methods and is the subject
of this paper. The equilibrium states of several systems are described from free energies of formation, the phase rule,
and the balances of mass and charge. Each model system has one or more minerals, a solution containing soluble salts
such as NaCI and KCI and CO2from the atmosphere. A number characteristic of each mineral and called the pKsp° is
calculated from the dissolution of that mineral according to the following rules. The mineral is on the left side ofthe
equation, written with one mole of the principal metal. The species on the right side are the neutral species, and
common oxidation states are used for each element, namely, Fe(lll), S(-ll), As(V), and Mn(ll). The value of pKsp° is then
computed from the free energies. When oxidation or reduction is required to achieve the common oxidation state, pe +
pH is used. For example:
haematite: Fe2O3, pKsp° = pFe(OH)3° = 11.943
siderite: FeCO3, pKsp° = pFe(OH)3° + pCO2° + (pH + pe) = 16.723
The activities of all othersolute species may then be calculated if the pe and pH ofthe solution are known. (The activity
of CO2 is found by assuming an atmosphere with 270 ppm.) A spreadsheet is calculated with (pH + pe) constant, with
each solute species on a row, and with each column being a fixed pH. The phase rule is used to find the degrees of
freedom, and these are satisfied by using STP, the fixed (pH + pe), and trial and error to reach mass balances. The
charge balanced is achieved at a single pH only.
Two example systems will be discussed. The first has the components Fe2O3, H2S, CO2, Na2O, K2O, HCI, H2 and O2. If
any two minerals of iron are present with the solution and the atmosphere, there will be six degrees of freedom. Three
tests on stoichiometry will be required, and these will be found by testing pCI(t), pK(t), and pNa(t) in each column against
preset values. The charge balance is found by plotting pQ(+) and p(abs(Q(-))) vs. pH and noting where the lines meet.
Twenty-seven minerals ofthe components are possible, and the chemical potentials of their precipitations are found by
comparing pKsp° to pQsp°, which has the same form with the actual activities. The customary game is to find the pair of
minerals which gives (pQsp° - pKsp°) > 0 for all the others. The system so found is the stable one, under the conditions.
The second system will be like the first with the added components As2O5 , MnO, P2O5, and CaO. There will be six
minerals or seven, and the game will be played. Graphs of arsenic solubility under several sets of circumstances will be
shown.
73
-------
Arsenic in Yellowknife, Canada
W. R. Cullen1,1. Koch, C. A. Ollson, and K. J. Reimer
Environmental Chemistry Group, University of British Columbia,
Environmental Sciences Group, Royal Military College of Canada,
Chemistry Department, University of British Columbia, Vancouver, B. C., Canada, VST 1Z1
T: 604-822-4435, F: 604-822-2847, E: wrc@chem.ubc.ca
Elevated levels of arsenic are found in a variety of environmental compartments in Yellowknife, NWT, Canada. Much of
this arsenic may be the consequence of historic and recent gold mine operations. The criteria for cleanup of the mine
sites and the surrounding land are currently being formulated but there are problems in determining what are the natural,
pre-mining concentrations that could be considered to be the remediation objective. The use of principal components
analysis to determine the origins of the arsenic in soils and sediments and to establish cleanup criteria will be described.
Plants and fish in the Yellowknife area were analyzed for total arsenic and forextractable, water-soluble, arsenic species
by using HPLC-ICP-MS methodology. The plant extracts contained mainly inorganic species although some methylated
species and arsenosugars were present. However, in general most of the arsenic, less than 50%, was not extracted.
Model gastric fluid studies suggest that the extracted arsenic represents the bioavailable arsenic. The arsenic species
in fish are more varied and probably reflect their diet. Unlike their marine counterparts, arsenobetaine is not the domi-
nant arsenic species.
74
-------
Measuring Arsenic Speciation in Waters — Choosing the Right
Analytical Technique for Your Geochemical Problem
Dirk WaiIschlager
Frontier Geosciences, Inc.
414 Pontius Ave N, Seattle, WA 98109
T: 206-622-6960, F: 206-622-6870, E: DirkW@Frontier.WA.com
Measuring arsenic (As) speciation in environmental and industrial waters is very important for accurate risk assessment,
understanding of hydrogeochemical processes, and for the design of efficient treatment strategies. Traditionally, four As
species have been determined in waters by most speciation techniques, namely arsenite [As(lll)], arsenate [As(V)],
monomethyl arsenate [MMAs(V)] and dimethylarsenate [DMAs(V)]. Different types of analytical approaches have been
employed, and a wide variety of speciation methods has been published, each of which has its inherent advantages and
disadvantages. This presentation will compare the three principal strategies currently employed forthe measurement of
As speciation in waters, and discuss their strengths and weaknesses with respect to their applicability in certain geochemical
environments.
Preservation is a key problem in the analysis of As speciation in waters, due to the instability of As(lll) towards oxidation.
Two approaches are commonly used to stabilize As(lll) between sample collection and analysis, namely acidification
and cryofreezing, but both lead to specific problems in certain types of waters. To overcome this whole problem area,
operationally-defined speciation approaches have been developed that use separation of As(lll) and As(V) in the field
(immediately after sample collection), and then only require total As measurements afterwards. Separation of As(lll)
and As(V) is achieved by selective adsorption on or desorption from solid phase extraction cartridges. However, the
separation conditions are usually optimized in aqueous standard solutions, and complex matrices may alterthe adsorp-
tion/desorption behavior, thereby introducing speciation artifacts. Also, this approach is not suitable forthe analysis of
MMAs(V) and DMAs(V).
EPA Method 1632 uses batch hydride generation (HG) to convert the four As species to their corresponding hydrides,
which are purged from the sample, cryogenically trapped, and then analyzed by gas chromatography with AAS detec-
tion. As(lll) and As(V) yield the same derivatization product, so they can only be distinguished by operationally-defined
selective HG at different pH. Due to the large possible sample volume, the technique has excellent detection limits
around 1 ng L1. It works very well in most waters; only samples with high dissolved metal concentrations give chemical
problems. Due to the fairly unspecific detection, artifactual signals have been observed in sulfidic waters and in petro-
leum-contaminated samples. The main problems of the method arise from the quantitation by difference for As(V),
which results in higher uncertainty, and sometimes in "negative" results, and often leads to issues regarding total vs.
dissolved concentrations. For MMAs(V) and DMAs(V), problems with de- and transmethylation have been widely re-
ported, unless pH during HG is controlled carefully.
Hyphenated speciation methods coupling liquid chromatography to atomic spectrometry detection are state-of-the-art
for As speciation. Each species yields a separate signal, eliminating problems arising from the indirect quantification of
As(V). HG-AFS detection yields detection limits around 0.1 °
-------
Approaches to Characterizing Solid Phase Arsenic Speciation
R. G. Ford
U. S. Environmental Protection Agency
National Risk Management Research Laboratory
919 Kerr Research Dr., Ada, OK 74820
Phone 580-436-8872, Fax 580-436-8703, ford.robert@.epa.gov
The partitioning of arsenic to solid matrices is an important process controlling the stabilization of arsenic wastes and
mobility of arsenic in the environment. Identification of the physicochemical characteristics of the partitioning mechanism(s)
is an important step towards optimization of treatment processes and assessment of the stability of arsenic-bearing
solids in environmental systems. Arsenic may reside in the solid phase as a discrete precipitate, a minor constituent
coprecipitated within the structure of a separate phase, or as a sorbed ion bound to surface sites of a separate phase.
Each of these solid phase partitioning mechanisms will possess a unique stability relative to the chemical conditions of
the treatment or disposal environment. It is critical to understand that a partitioning mechanism that is stable under pre-
disposal conditions may become unstable after disposal due to differences in system chemistry such as pH and oxida-
tion-reduction (redox) potential.
Accurate identification of the arsenic solid phase association is dependent on the use of collection and storage tech-
niques that preserve the in-situ physicochemical state of the sample. In soils and sediments, inorganic forms of arsenic
are commonly associated with solid phases composed of redox sensitive elements such as iron, manganese, and
sulfide. Samples collected from a reduced environment will react with oxygen in the atmosphere, thus altering sample
mineralogy and arsenic phase association. This type of sample alteration may not be critical if the primary task of
characterization is demonstration of patterns in element distribution. However, sample preservation is critical if the goal
of characterization is demonstration of arsenic partitioning to specific mineral phases.
Various methods are available for identification of the arsenic solid phase association. The presence of arsenic within a
discrete solid phase may be identified via optical/electron microscopy and/or X-ray diffraction provided there is sufficient
abundance of the discrete phase. It may be possible to increase the relative abundance of a discrete phase through
physical means such as particle size or density separations. More commonly, solid phase associations are established
through identification of correlations in element composition. These associations may be established via characteriza-
tion by X-ray fluorescence spectroscopy or by determination of element content following chemical dissolution. Chemi-
cal extraction procedures designed to target specific solid phase associations are frequently employed to aid identifica-
tion of the arsenic partitioning process. However, two major limitations to the universal acceptance of proposed extrac-
tion schemes are 1) the lack of standard reference materials appropriate for near surface environments, and 2) the
acceptance and application of a quality assurance protocol to verify data obtained for the various solid matrices present
in environmental systems.
76
-------
Protocols for Estimating Arsenic Leaching from Soils and Solidified Wastes
F. Sanchez, A.C. Garrabrants, D.S. Kosson
Civil and Environmental Engineering, Vanderbilt University
Box 1831, Station B, Nashville, TN 37235
T: 615-322-5135, F: 615-322-3365, E: Florence.Sanchez(S)vanderbilt.edu,
garrabra@rci.rutgers.edu, David.Kosson@vanderbilt.edu
H. A. van der Sloot
The Netherlands Energy Research Foundation
Westerduinweg 3, P.O. Box 1, Petten, 1755ZG, The Netherlands
T: +31 224-56-4249, F: +31 224-56-3163, E: vandersloot@.ecn.nl
A framework for evaluation of leaching from soils and wastes has been presented in a preceding paper (see van der
Sloot, et al. "A Framework for Assessing Arsenic Leaching from Soils and Wastes," 2.0 Plenary Session). The specific
objectives of this talk will be to: (i) describe specific testing protocols and interpretation approaches for estimating the
leaching behavior of pollutants from solid wastes, and (ii) show how the integrated use of equilibrium and mass transfer
leach tests in conjunction with appropriate mass transfer models can provide more realistic release estimates for both
direct comparison of different treatment processes underdiverse potential environmental conditions (e.g., overa range
of field pHs) and impact from different management scenarios. This approach has potential for use to estimate long-
term environmental impacts from leaching and to compare the efficacy of waste treatment processes.
We will discuss arsenic solubility as a function of pH and low liquid-to-solid ratio and arsenic release rate information of
(i) a soil contaminated with arsenic from a pesticide production facility ("untreated As soil"), and (ii) the same soil
subsequently treated by a Portland cement stabilization/solidification process ("S/S treated As soil"). As an example, we
will provide and compare long-term arsenic release estimates (100-year time frame) for different management sce-
narios (disposal under percolation and flow-around contact mode) including consideration of local conditions (e.g.,
infiltration and site-specific design).
77
-------
The Best Analog to the Real World Is the Real World: Vadose-Zone Sampling as an Alterna-
tive to Core Sampling and Leaching Protocols
JimV. Rouse
Montgomery Watson
370 Interlocken Blvd, Suite 300
Broomfield, CO 80021
303-410-4029
FAX 303-410-4100
Jim.rouse@mw.com
Shortcomings with Conventional Approach
The conventional approach to evaluating the presence and potential mobility of metals and metalloids such as arsenic in
a soil is to collect core samples of the soil, assay the core for metal content, and perhaps to run some sort of synthetic
leach protocol designed to simulate the mobility of the metal under field conditions. The analysis of the core determines
a total of three component concentrations:
1) Metals present in the soil or rock at the time of deposition, with little or no potential mobility
2) Metals sorbed onto the soil material, with variable mobility
3) Metals dissolved in the interstitial void moisture
This last component is the one that presents the greatest potential for migration into the underlying groundwater.
Cullen, Kramer, Everett and Eccles (1995) noted the failings of not considering such migration as the greatest threat to
the groundwater.
The various leach protocols commonly use some form of organic acid as a lixiviant. In some cases, the selected lixiviant
is capable of mobilizing the metal of concern to a much greater extent than real world soil moisture. For example, lead
acetate is one of the few mobile forms of lead, so use of acetic acid in the TCLP overstates the geochemical "hazard" of
lead, compared to observations of actual ground-water contamination with lead. Vinegar is not a common component of
rainfall.
Alternative Approach
An alternative that has proven useful is to utilize the real-world conditions that obtain at the sites of metal contamination
of soil and sludges, by obtaining samples of actual soil moisture by the installation and sampling of pressure/vacuum
lysimeters. Such p/vlysimeters were originally developed for soil moisture sampling in agricultural applications, but have
proven highly useful in the determination of the concentrations of contaminants in soil moisture (Wilson, Dorrance,
Bond, Everett, and Cullen, 1995) (Bond and Rouse, 1985). Such lysimeters are capable of collecting samples of actual
soil moisture, in remote locations such as under heap-leach facilities or ponds, on a periodic basis to monitor for the
development of leaks and an advancing front of contaminated moisture.
Case Histories
A number of cases are discussed, where there was little relationship between the soil moisture and total or leachable
metals content. In many cases, the conventional approach severely overstated the hazard, but in some cases it under-
stated the hazard, which potentially could lead to a false sense of security.
References
Bond, W.R. and JimV. Rouse, 1985, "Lysimeters allow quicker monitoring of heap leach and tailings sites", Mining
Engineering, vol. 37, p. 314-319.
Cullen, Stephen J., John H. Kramer, Lome G. Everett, and Lawrence A. Eccles, 1995, "Is our ground-water monitoring
strategy illogical?" Handbook of Vadose Zone Characterization and Monitoring, Lewis.
Wilson, L.G.; Dorrance, D.W; Bond, W.R.; Everett, L.G.; and S.J. Cullen, 1995, "//7.S/ft/pore-liquid sampling in the
vadose zone", Handbook of Vadose Zone Characterization and Monitoring, Lewis.
78
-------
Appendix A - Workshop Agenda
A- 1
-------
US EPA Workshop on Managing Arsenic Risks to the Environment:
Characterization of Waste, Chemistry, and Treatment and Disposal
WORKSHOP GOALS
The goals of the workshop are: (1) to examine the chemical fundamentals related to arsenic chemistry,
speciation, and analytical issues, (2) to examine the state of practice of existing and emerging technologies
that treat and properly dispose of arsenic wastes, and (3) to identify/characterize sources of arsenic.
TUESDAY, MAY 1 - PLENARY SESSION
Capitol Rooms
8:45 AM
8:55 AM
9:05 AM
9:30 AM
9:55 AM
10:10AM
10:35 AM
11:00 AM
11:30 AM
1:00 PM
1:25 PM
1:50 PM
2:15 PM
2:40 PM
3:00 PM
Welcome Remarks, Max Dodson, US EPA Region 8
Opening Remarks, Doug Grosse, US EPA, National Risk Management Research
Laboratory (NRMRL)
ORD Perspective, Paul Randall, US EPA, National Risk Management Research
Laboratory (NRMRL)
Hazardous Waste Treatment/Regulatory Issues, JimBerlow, USEPA, Office ofSolio
Waste (OSW)
Break
Arsenic Cycling in the Mining Environment, Rob Bowell, SRK Consulting
Arsenic in Groundwaters of the United States, Dennis Helsel, U.S. Geological
Survey
Managing Arsenic Occurrence Information in Drinking Water, Larry Scan/an, Utah
Department of Health
Lunch
TRI: What It Is. Where to Find It. And How to Use It., Joyel Dhieux, USEPA,
Region 8
Arsenic Hazardous and Remediation Waste: Sources and Treatment, Linda Fiedler,
USEPA, Technology Innovation Office (TIO)
Treatment Options for Arsenic Wastes, Godage Wickramanayake, Battelle Memorial
Institute
Some Chemical Aspects Relating to Arsenic Remedial Technologies, Robert Robins,
AquaMin Science Consortium International
Break
Arsenic Geochemistry: An Overview of an Underhanded Element, Kirk Nordstrom,
U.S. Geological Survey
A-2
-------
TUESDAY, MAY 1 - PLENARY SESSION
Capitol Rooms
(Continued)
3:25 PM
3:50 PM
4:30 PM
5:00 PM
Impact of Microbial Activity
School of Mines
A Framework for Assessing
Vanderbilt University
on Arsenic Geochemistry, Dianne Ahmann, Colorado
Arsenic Leaching from Soils and Water, David Kosson,
Q&A
Adjourn
WEDNESDAY, MAY 2 - CONCURRENT BREAKOUT SESSIONS
8:00 AM
10:00 AM
10:30 AM
Noon
1:30 PM
3:00 PM
3:30 PM
5:00 PM
7:30- 9:00 PM
Concurrent
Breakout Sessions
Break
Concurrent
Breakout Sessions
Lunch
Concurrent
Breakout Sessions
Break
Concurrent
Breakout Sessions
Adjourn
Meeting to
plan Day 3 Reports
A-3
-------
BREAKOUT SESSION SPEAKERS AND PARTICIPANTS
Source Identification Breakout Session
Capitol Room 2
Co-Chairs
Diana Bless, US EPANRMRL
Doug Grosse, US EPANRMRL
Carol Russell, US EPA Region VIM
Speakers
Scott Warner, Geomatrix Consultants, Inc.
Richard Glanzman, CH2M Hill
Tracy Connell Hancock, USGS
Roger Olsen, Camp Dresser & McKee, Inc.
Andy Davis, Geomega, Inc.
Martin Goldhaber, USGS
John Pantano, ARCO Env. Remediation
Stephen Schoen, Placer Dome America
and Glenn Eurick, Barrick Management
Corporation
Distinguishing Natural and Anthropogenic Sources of
Arsenic: Implications for Site Characterization
Arsenic Background and Associated Elements
Controlling Mobility
Reconnaissance for Arsenic in a Poultry Dominated
Chesapeake Bay Watershed - Examination of Source,
Transport and Fate
Characterization of the Forms of Arsenic in Soil/
Sediments to Evaluate Mobility and Treatment
Iron Amendments as Adjuncts to Constrain Arsenic
Solubility in a Marsh Environment
Potential Environmental Consequences of Localized
Arsenic Enrichment in Appalachian Basin Coals
Arsenic Concentrations in Water at Mining Sites
Arsenic and TRI in Select Nevada Gold Production
Operations
Participants
Jim Berlow, US EPA OSW
Robert Bowell, SRK Consulting
Joyel Dhieux, US EPA Region VIM
Tim Eastep, Phelps Dodge Corporation
Barbara O'Grady, Colorado Department of Public Health and Environment
Jeff Parshley, SRK Consulting
A-4
-------
Treatment and Disposal
Capitol Room 3
Co-Chairs
Paul Randall, US EPA NRMRL
Robert Robins, AquaMin Science Consortium International
Chris Impellitteri, US EPA NRMRL
Speakers
Peter Shields, Tetra Tech EMI
Neill Thompson,
Government of Canada
Jay McCloskey, MSE Inc.
Rong-Yu Wan, Newmont Mining
Corporation
Lena Ma, University of Florida
James Redwine,
Southern Company Services, Inc.
Richard Markey, Southern Company
Gulf Power Company
Michael Leist, Varian Inc.
Irene Legiec, DuPont
Jeri Sullivan, Los Alamos
National Laboratory
James Navratil, Clemson University
Treatment Technologies for Wastes and Environmental Media
Containing Arsenic
Treatment Options for Arsenic Trioxide Bearing Dust at the
Giant Mine, Yellow/knife, Northwest Territories, Canada
Removing Arsenic for Mining Industry Waters, Treatability
Studies, EPA Mine Waste Program
Characterization of Arsenic in Refractory Gold Ores Roasting
- Cyandation Processing
Phytoremediation of Arsenic Contaminated Sites Using Brake
Fern Hyperaccumulator
In-Situ Chemical Fixation for Arsenic Remediation and Arsenic
Mobility Studies
Arsenic Contamination in Soil and Groundwater: Review of -
Remediation Methods
The Cement Stabilization and Leaching of Arsenic
Characterization and Treatment of Arsenic Contaminated
Soils: The Dupont Experience
Sorption of Arsenic from Soil-Washing Leachate by
Surfactant-Modified Zeolite
Adsorption and Nanoscale Magnetic Separation of Heavy
Metals from Water
Participants
John Austin, US EPA OSW
Ed Bates, US EPA NRMRL
Eric Bock, U.S. Ecology of Idaho
John Burckle, Burckle Consulting
Jim Dunn, US EPA
Peggy Groeber, SAIC
Linda Fiedler, US EPA TIO
David Kosson, Vanderbilt University
JuanParra, USEPAOSW
Florence Sanchez, Vanderbilt University
Larry Scanlan, Utah Department of Health
Godage Wickramanayake, Battelle Memorial Institute
A-5
-------
Arsenic Chemistry
Capitol Room 4
Co-Chairs
Robert Ford, US EPA NRMRL
Kirk Nordstrom, USGS
Speakers
Harry Hemond, Massachusetts
Institute of Technology
Spencer Porter, US EPAORD
William Cullen, University of
British Columbia
DirkWallschlaeger, Frontier
Geosciences, Inc.
Robert Ford, US EPA NRMRL
Barton Simmons, California
Department of Toxic Substances Control
Florence Sanchez, Vanderbilt University
Jim V. Rouse, Montgomery Watson
Interactions of Arsenic Speciation with the Nitrogen
Cycle
Arsenic Immobilization: Thermochemical Analyses
Arsenic in Yellow/knife, Canada
Measuring Arsenic Speciation in Waters - Choosing the
Right Analytical Technique for Your Geochemical
Problem
Approaches to Characterizing Solid Phase Arsenic
Speciation
Comparative Extractions of Arsenic Containing Wastes
for Waste Classification
Protocols for Estimating Arsenic Leaching from Soils
and Solidified Waste
Alternative Methods to Assessing Leach Potential
Participants
Dianne Ahmann, Colorado School of Mines
SouhailAI-Abed, US EPA NRMRL
Willard Chappell, University of Colorado at Denver
Kyle Cook, SAIC
Jack Creed, U.S. EPAORD
Kevin H. Gardner, University of New Hampshire
Sabine Goldberg, USDA-ARS
Ed Herthmar, U.S. EPA
Ralph Ludwig, US EPA NRMRL
Gregory Miller, Geochemical, Inc.
Larry Rosengrant, US EPAOSW
RickSanzolone, USGS
Kathleen Smith, USGS
A-6
-------
THURSDAY, MAY 3 - BREAKOUT SESSION REPORTS - SINGLE SESSION
8:30 AM
9:15AM
10:00 AM
10:30 AM
11:15 AM
Noon
12:15PM
Source Identification
Arsenic Chemistry
Break
Treatment and Disposal
Q&A
Closing Remarks
Adjourn
QUESTIONS FOR BREAKOUT GROUPS
Source Identification
1. What are the primary waste forms that contribute to Arsenic contamination?
2. What are the major problems encountered with characterization of Arsenic impacted media or
sources?
3. What significant data gaps and information needs exist for characterizing and identifying Arsenic
sources and waste forms?
4. What are the two or three important insights to be conveyed regarding the management of Arsenic
risks from industry?
Treatment and Disposal
1. What are the long term stability issues with regard to land disposing (i.e., on-site storage or landfills)
arsenic stabilized wastes?
2. How do current advances (i.e., molecular chemistry, leaching mechanisms) impact the areas of
arsenic treatment and disposal?
3. What are the top five research needs in arsenic treatment and disposal?
Arsenic Chemistry
1. Is our knowledge of arsenic speciation and transformation adequate to identify pathways and routes
of mobility?
2. Are current collection, preservation, and analytical techniques sufficient for defining arsenic
chemistry in natural and engineered systems?
3. Are existing leaching procedures adequate for characterization of arsenic-bearing waste
materials?
A-7
-------
Appendix B - Steering Committee and Attendees
B- 1
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
STEERING COMMITTEE
Diana Bless
U.S. EPAORD
Jack Creed
U.S. EPAORD
Glenn Eurick
Barrick Management Corporation
Linda Fiedler
U.S. EPAOSWER
Robert Ford
U.S. EPAORD
Andrea Foster
U.S. Geological Survey
David Frank
U.S. EPA Region X
Doug Grosse
U.S. EPAORD
Ed Hanlon
U.S. EPAORD
Greg Helms
U.S. EPAOSWER
ChristopherA. Impellitteri
U.S. EPAORD
D. Kirk Nordstrom
U.S. Geological Survey
Juan Parra
U.S. EPAOSWER
Paul Randall
U.S. EPAORD
Carol Russell
U.S. EPA Region VIM
Stephen M. Schoen
Placer Dome America
James Smith
U.S. EPAOW
B-2
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Dianne Ahmann
Assistant Professor
Phone: 303-273-3402
Fax:303-273-3413
E-mail: dianne@mines.edu
Colorado School of Mines
Division of Environmental Science and Engineering,
Coolbaugh Hall
Golden, CO 80401
USA
Dr. Souhail R. AI-Abed
Chemist
Phone: 513-569-7849
Fax: 513-569-7879
E-mail: al-abed.souhail@epa.gov
U.S EPA
26 W. Martin Luther King Dr.
Cincinnati, OH 45268
USA
John J.Austin
Chemist
Phone: 703-308-0436
Fax: 703-308-8433
E-mail: austin.john@epa.gov
U.S. EPA Office of Solid Waste
Hazardous Waste Minimization & Management
Division, Mail code: 5302W, Ariel Rios Building
1200 Pennsylvania Ave., N.W
Washington, DC 20460
USA
James L. Basler
Manager, Western Customer Services
Phone: 360-695-6969
Fax: 360-693-4138
E-mail: jbasler@qwest.net
Osmose
2001 Main Street
Vancouver, WA 98660-2636
USA
Edward Bates
Phone: 513-569-7774
Fax: 513-569-7676
E-mail: bates.edward@epa.gov
US EPA
MS 489, 26 West Martin Luther King Drive
Cincinnati, OH 45268
USA
Jim Berlow
Office Director
Phone: 703-308-8414
Fax: 703-308-8433
E-mail: berlow.jim@epa.gov
US EPA Office of Solid Waste
Hazardous Waste Minimization & Management
Division, 1200
Pennsylvania Avenue, 5302W
Washington, DC 20460
USA
Ben Blaney
Phone: 513-569-7852
Fax:
E-mail: blaney.ben@epa.gov
US EPA
MS 235, 26 West Martin Luther King Drive
Cincinnati, OH 45268
USA
Diana Bless
Chemical Engineer
Phone: 513-569-7674
Fax: 513-569-7471
E-mail: bless.diana@epa.gov
U.S. EPA
26 W. Martin Luther King Drive
Cincinnati, OH 45268
USA
B-3
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Eric Bock
Laboratory Manager
Phone: 1-800-274-1516x3024
Fax: 208-834-2997
E-mail: e.bock@enso.net
U.S. Ecology of Idaho
P.O. Box400
Grand View, ID 84624
USA
Dr. Robert J. Bowell
Principal Geochemist
Phone: +44-2920-235566
Fax: +44-2920-665413
E-mail: rbowell@srk.co.uk
SRK Consulting
Summit House, 9 Windsor Place
Cardiff, Wales CF103RS
United Kingdom
John Burckle
Consultant
Phone: 513-751-5680
Fax: 513-569-7471
E-mail: johnburckle@fuse.net
Burckle Consulting
3909 Middleton Avenue
Cincinnati, OH 45220
USA
Nick Ceto
Regional Mining Coordinator
Phone: 206-553-1816
Fax: 206-553-0124
E-mail: ceto.Nicholas@epa.gov
U.S. EPA Region X
1200 Sixth Ave.
Seattle, WA 98101
USA
Willard R. Chappell
Professor
Phone: 303-556-3460
Fax: 303-556-4292
E-mail: wchappel@carbon.cudenver.edu
University of Colorado at Denver
1224 5th Street
Denver, CO 80204
USA
Scott W.Conklin
Director, Regulatory Affairs
Phone: 616-365-1563
Fax: 616-364-5558
E-mail: sconklin@ufpi.com
Universal Forest Products, Inc.
2801 East Beltline NE
Grand Rapids, Ml 49525
USA
B-4
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Kyle Cook
Project Manager
Phone: 858-826-6117
Fax: 858-826-2735
E-mail: cookky@saic.com
SAIC
4242 Campus Point Court, Mail Stop D4
San Diego, CA 92121
USA
Jack Creed
Phone: 513-569-7833
Fax: 513-569-7757
E-mail: creed.jack@epa.gov
EPA/ORD
26 W. Martin Luther King Dr.
Cincinnati, OH 45268
USA
Dr. William R.Cullen
Professor
Phone: 604-822-4435
Fax: 604-822-2847
E-mail: wrc@chem.ubc.ca
University of British Columbia
Chemistry Department, 2036 Main Mall
Vancouver, BC V6T1Z1
Canada
Andy Davis
Director of Geochemistry
Phone: 303-938-4083
Fax: 303-938-8123
E-mail: andy@geomega.com
Geomega, Inc.
2995 Baseline Rd., Suite 202
Boulder, CO 80303-2318
USA
Joyel Dhieux
EPCRA Prog ram Coordinator
Phone:303-312-6447
Fax: 303-312-6026
E-mail: dhieux.joyel@epa.gov
U.S. EPA Region VIM
999 18th Street, Suite 300
Denver, CO 80202-2466
USA
Max Dodson
Assistant Regional Administrator
Phone:303-312-6598
Fax: 303-312-7025
E-mail: dodson.max@epa.gov
EPA Region VIM
999 18th St., Suite 300
Denver, CO 80202
USA
Jim Dunn
Phone: 303-312-6573
Fax:
E-mail: dunn.james@epa.gov
US EPA
MC 8EPR - PS, 999 18th Street, Suite 300
Denver, CO 80202
USA
Tim Eastep
Sr. Environmental Engineer
Phone: 480-929-4473
Fax: 480-929-4506
E-mail teastep@phelpsdodge.com
Phelps Dodge Corporation
1501 W. Fountainhead Pkwy, Suite 290
Tempe,AZ 85282
USA
B-5
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Glenn Eurick
Phone: 801-741-4666
Fax: 801-541-3577
E-mail: bgcslc2@worldnet.att.net
Barrick Management Corporation
136 East South Temple, Suite 1050
Salt Lake City, UT 84111
USA
Linda Fiedler
Environmental Engineer
Phone:703-603-7194
Fax: 703-603-9135
E-mail: fiedler.linda@epa.gov
U.S. EPA Technology Innovation Office
1200 Pennsylvania Ave., N.W. (5102G)
Washington, DC 20460
USA
Robert Ford
Environmental Scientist
Phone: 580-436-8872
Fax: 580-436-8703
E-mail: ford.robert@epa.gov
USEPANRMRL
919 Kerr Research Dr.
Ada, OK 74820
USA
Kevin H. Gardner
Research Professor
Phone: 603-862-4334
Fax: 603-862-3957
E-mail: kevin.gardner@unh.edu
University of New Hampshire
Environmental Research Group
Durham, NH 03824
USA
Richard K. Glanzman
Senior Geochemist/Geohydrologist
Phone: 303-771-9019 ext. 5309
Fax: 303-754-0196
E-mail: rglanzma@ch2m.com
CH2M Hill
100 Inverness Terrace East
Englewood,CO 80112-5305
USA
Sabine Goldberg
Soil Scientist
Phone: 909-369-4820
Fax: 909-342-4962
E-mail: sgoldberg@ussl.ars.usda.gov
USDA-ARS
George E. Brown Jr., Salinity Laboratory,
450 W Big Springs Road
Riverside, CA 92507
USA
Martin Goldhaber
Research Chemist
Phone: 303-236-1521
Fax: 303-236-3200
E-mail: mgold@usgs.gov
US Geological Survey
Crystal Imaging Team, Denver Federal Center,
MS 973
Denver, CO 80225
USA
Peggy Groeber
Phone:513-569-5865
Fax:
E-mail: groeberm@saic.com
SAIC
2260 Park Avenue, Suite 402
Cincinnati, OH 45206
USA
B-6
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Doug Grosse
Phone: 513-569-7844
Fax:
E-mail: grosse.douglas@epa.gov
US EPA ORD
26 W. Martin Luther King Dr.
Cincinnati, OH 45268
USA
Tracy Connell Hancock
Hydrologist
Phone:804-261-2618
Fax: 804-261-2659
E-mail: thancock@usgs.gov
U.S. Geological Survey
1730 East Parham Road
Richmond, VA 23116
USA
Evelyn Hartzell
Engineer
Phone:513-569-5868
Fax: 513-569-4800
E-mail: ehartzell@queencity.com
SAIC
2260 ParkAvenue, Suite 402
Cincinnati, OH 45206
USA
Edward Heithmar, Ph.D.
Research Chemist
Phone: 702-798-2626
Fax:
E-mail: heithmar.ed@epa.gov
US EPA ORD/NERL
944 E. Harman Ave.
Las Vegas, NV 89119
USA
Dennis R. Helsel, Ph.D.
Chief, Trace Element Synthesis
Phone: 303-236-2101 ext.227
Fax: 303-236-4912
E-mail: dhelsel@usgs.gov
U.S. Geological Survey
P.O. Box25046, MS-415
Denver, CO 80225
USA
Harry Hemond
Professor of Civil and Environmental Engineering
Phone:617-253-1637
Fax: 617-258-8850
E-mail: hfhemond@mit.edu
Massachusetts Institute of Technology
48-311
Cambridge, MA 02139
USA
Christopher A. Impellitteri, Ph.D.
Environmental Engineer
Phone:513-569-7673
Fax: 513-569-7620
E-mail: lmpellitteri.Christopher@epa.gov
US EPA
26 W. Martin Luther King Drive
Cincinnati, OH 45268
USA
Dr. David Kosson
Phone:615-322-1064
Fax: 615-322-3365
E-mail: david.kosson@vanderbilt.edu
Vanderbilt University
Station B 351831
Nashville, TN 37235
USA
B-7
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Irene A. Legiec, Ph.D.
Supervisor, Analytical Services and S.H.E. Group
Phone:856-540-4912
Fax: 856-540-4961
E-mail: irene.a.legiec-2@usa.dupont.com
DuPont
Jackson Lab, Chambers Works, Route 130
Deepwater, NJ 08023
USA
Michael Leist
BSc (Hons)
Phone:+61 395661418
Fax: +61 3 9560 7950
E-mail: michael.leist@research.vu.edu.au
Varian Inc.
Varian Australia, R & D department,
679 Springvale Road
Mulgrave, Victoria 3170
Australia
Ralph Ludwig
Environmental Scientist
Phone: 580-436-8603
Fax: 580-436-8614
E-mail: ludwig.ralph@epa.gov
US EPA
Robert S. Kerr Environmental Research,
919 Kerr Research Drive
Ada, OK 74820
USA
Dr. Lena Q. Ma
Associate Professor
Phone: 352-392-9063
Fax: 352-392-3902
E-mail: lqma@ufl.edu
University of Florida
Soil and Water Science Department
Gainesville, FL 32611-0290
USA
Richard "Mike" Markey
Senior Geologist
Phone: 850-444-6573
Fax: 850-444-6217
E-mail: rmmarkey@southernco.com
Southern Company - Gulf Power Company
One Energy Place
Pensacola, FL 32520-0328
USA
Alina Martin
Environmental Specialist
Phone:703-318-4678
Fax: 703-736-0826
E-mail: martinali@saic.com
SAIC
11251 Roger Bacon Drive
Reston, VA20190
USA
Jay McCloskey
Program Manager, Process Engineer
Phone: 406-494-7262
Fax: 406-494-7230
E-mail: jmcclosk@mse-ta.com
MSE, Inc.
200 Technology Way
Butte, MT 59702
USA
B-8
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Dr. James D. Navratil
Professor
Phone: 864-656-1004
Fax: 864-656-0672
E-mail: nav@clemson.edu
Clemson University
Engineering and Science, 342 Computer Court
Anderson, SC 29625-6510
USA
D. Kirk Nordstrom
Phone: 303-541-3037
Fax: 303-447-2505
E-mail: dkn@usgs.gov
USGS
3215 Marine St. Suite E-127
Boulder, CO 80303-1066
USA
Barbara O'Grady
State Remedial Project Manager
Phone: 303-692-3395
Fax: 303-759-5355
E-mail: barbara.ogrady@state.co.us
Colorado Department of Public Health and
Environment (CDPHE)
4300 Cherry Creek Drive South
Denver, CO 80124
USA
Roger L. Olsen, Ph.D.
Sr. Geochemist/Sr. Vice President
Phone:303-298-1311
Fax: 303-293-8236
E-mail: olsenrl@cdm.com
Camp Dresser & McKee, Inc.
1331 17th Street, Suite 1200
Denver, CO 80007
USA
John Pantano
Sr. Principal Scientist
Phone: 406-563-5211 ext. 427
Fax: 406-563-8269
E-mail: pantanj1@bp.com
ARCO Env. Remediation
307 East Park St., Suite 400
Anaconda, MT 59711
USA
Juan Parra
Environmental Engineer
Phone: 703-308-0478
Fax: 703-308-8433
E-mail: parra.juan@epa.gov
US EPA Office of Solid Waste
Waste Treatment Branch, Hazardous Waste
Minimization & Management Division,
1200 Pennsylvania Avenue, 5302W
Washington, DC 20460
USA
Mr. Jeff Parshley
Principal
Phone: 775-828-6800
Fax: 775-828-6820
E-mail: jparshley@srk.com
SRK Consulting
5250 Neil Road, Suite 300
Reno, NV 89502
USA
Spencer Porter
Chemist
Phone:513-569-7851
Fax: 513-569-7879
E-mail: porter.spencer@epa.gov
US EPA
5995 Center Hill Avenue
Cincinnati, OH 45224
USA
B-9
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Paul Randall
Senior Chemical Engineer
Phone:513-569-7673
Fax: 513-569-7620
E-mail: randall.paul@epa.gov
USEPA-NRMRL
26 W. Martin Luther King Dr.
Cincinnati, OH 45268
USA
James C. Redwine, Ph.D., P.G.
Principal Geologist
Phone: 205-992-6075
Fax: 205-992-0356
E-mail: jcredwin@southernco.com
Southern Company Services, Inc.
Bin B263, 42 Inverness Parkway
Birmingham, AL 35242
USA
Robert G. Robins, M.Sc., Ph.D.
Scientific Fellow
Phone: 61 294163928
Fax: 61294163928
E-mail: bobrobins@bigpond.com.au
AquaMin Science Consortium International
25 Adelaide Avenue
Lindfield, NSW 2070
Australia
Larry Rosengrant
Senior Environmental Scientist
Phone: 703-308-0462
Fax: 703-308-0511
E-mail: rosengrant.larry@epa.gov
US EPA OSW
1200 Pennsylvania Avenue, NW(5307W)
Washington, DC 20460
USA
Jim V. Rouse
Phone: 303-526-5493
Fax:
E-mail: Jim_V_Rouse@us.mw.com
Montgomery Watson
1328 Northridge Court
Golden, CO 80401
Carol Russell
Mining Team
Phone:303-312-6310
Fax: 303-312-6897
E-mail: russell.carol@epa.gov
US EPA Region VIM
999 18th St.
Denver, CO 80202
USA
Dr. Florence Sanchez
Research Assistant Professor
Phone:615-322-5135
Fax: 615-322-3365
E-mail: florence.sanchez@vanderbilt.edu
Vanderbilt University
Civil and Environmental Engineering Department,
107CA Jacobs Hall, VU Box 1831 Station B
Nashville, TN 37235
USA
Rick Sanzolone
Research Chemist
Phone:303-236-1856
Fax: 303-236-1800
E-mail: rsanzolo@usgs.gov
USGS
Box 25046, Denver Federal Center, MS-973
Lakewood, CO 80215
USA
B- 10
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Larry P. Scanlan
Dir. of Environmental Chemistry and Toxicology
Phone:801-584-8400
Fax:
E-mail: lscanlan@doh.state.ut.us
Utah Department of Health
46 N Medical Drive
Salt Lake City, UT 84092
USA
Stephen M. Schoen
Environmental Coordinator
Phone: 775-468-4408
Fax: 775-468-4610
E-mail: steve_schoen@placerdome.com
Placer Dome America
HC66-50, Star Route
Beowawe, NV 89821
USA
Peter J. Shields
Senior Chemical Engineer
Phone: 703-390-0659
Fax: 703-391-5876
E-mail: ShieldP@ttemi.com
TetraTech EMI
1881 Campus Commons Drive, Suite 200
Reston,VA20191
USA
Barton P. Simmons, Ph.D.
Chief
Phone:510-540-3112
Fax: 510)540-2305
E-mail: bsimmons@dtsc.ca.gov
Calfornia Department of Toxic Substances Control
Hazardous Materials Laboratory, 2151 Berkeley Way
Berkeley, CA 94704
USA
Kathleen S. Smith
Geologist/Geochemist
Phone: 303-236-5788
Fax: 303-236-3200
E-mail: ksmith@usgs.gov
U.S. Geological Survey
M.S. 973, Denver Federal Center
Denver, CO 80225-0046
USA
Pat G. Smith, C.P.G.
Environmental Scientist
Phone: 303-312-6082
Fax:303-312-6067
E-mail: smith.patricia@epa.gov
US EPA Region VIII
Office of EcoSystem Protection and Remediation
(8EPR-ER),
999 18th Street, Suite 500
Denver, CO 80202
USA
Dr. Enid J. "Jeri" Sullivan
Post-Doctoral Research Associate
Phone: 505-667-2889
Fax: 505-665-9118
E-mail: ejs@lanl.gov
Los Alamos National Laboratory
LANL, MS J514, E-ET Division
Los Alamos, NM 87545
USA
B- 11
-------
US EPA Workshop on Managing Arsenic Risks to the Environment
May 1-3, 2001
Denver, Colorado
FINAL LIST OF ATTENDEES
Neill Thompson
Project Manager- Royal Oak Project
Phone: 867-669-2434
Fax: 867-669-2439
E-mail: thompsonn@inac.gc.ca
Government of Canada
Department of Indian Affairs and Northern Development
Box 1500
Yellow/knife, NT X1A7V2
Canada
Dirk Wallschlaeger, Ph.D.
Research Scientist
Phone: 206-622-6960
Fax: 206-622-6870
E-mail: DirkW@Frontier.WA.com
Frontier Geosciences, Inc.
414 Pontius Ave N.
Seattle, WA 98109
USA
Rong-Yu Wan, Ph.D.
Chief Research Scientist- Hydrometallurgy
Phone: 303-470-3524
Fax: 303-470-3524
E-mail: r.wan@worldnet.att.net
Newmont Mining Corporation
96345 Kalamere Court
Highlands Ranch, CO 80126
USA
Scott D. Warner, RG,CHG,CEG
Senior Engineering Hydrogeologist
Phone:510-663-4269
Fax: 510-663-4141
E-mail: swarner@geomatrix.com
Geomatrix Consultants, Inc.
2101 Webster Street, 12th Floor
Oakland, CA 94612
USA
Godage Wickramanayake, Ph.D., PE
Senior Program Manager
Phone:614-424-4698
Fax: 614-424-3667
E-mail: wickram@battelle.org
Battelle Memorial Institute
505 King Avenue
Columbus, OH 43201
USA
B- 12
-------
Appendix C - Selected Publications Bibliography
C-1
-------
NHEERL Publications on Arsenic
U.S. Environmental Protection Agency
Office of Research and Development
National Health and Environmental Effects Research Laboratory
Drinking Water Research Program
1998 to Present
(April 2001)
Ahmad, S., W. L.Anderson, and K. T. Kitchin. 1999. Dimethylarsinic acid effects on DMA damage and
oxidative stress related biochemical parameters in B6C3FI mice. Cancer Letters. 139:129-135.
Ahmad, S., K. T. Kitchin, and W. R. Cullen. 2000. Arsenic species that cause release of iron from ferritin
and generation of activated oxygen. Arch. Biochem. Biophys. 382:195-202.
Calderon, R. L. 2000. The epidemiology of chemical contaminants of drinking water. FoodChem. Toxicol.
38:S13-S20.
Calderon, R. L., E. Hudgens, X. Chris Le, D. Schreinemachers, D. J. Thomas. 1999. Excretion of arsenic in
urine as a function of exposure to arsenic in drinking water. Environ. Health Perspect. 107:663-667.
Chappell, W. R., C. O. Abernathy, and R. L. Calderon (eds). 1999. Arsenic Exposure and Health Effects:
Proceedings of the Third International Conference on Arsenic Exposure and Health Effects. July 12-15,
1998, San Diego, CA. New York: Elsevier.
Del Razo, L. M., M. Styblo, W. R. Cullen, D. J. Thomas. Determination of the trivalent methylated
arsenicals in biological matrices. Toxicol. Appl. Pharmacol. (in press).
Feng, A. Y. Xia, D.Tian, K. Wu, M. Schmitt, R. K. Skok, and J. L. Mumford. 2001. DMA damage in buccal
epithelial cells from individuals chronically exposed to arsenic via drinking water in Inner Mongolia,
China. AnticancerResearch2\ :51-58.
Goering, P. L., H. V. Aposhian, M. J. Mass, M. Cebrian, B. D. Beck and M. P. Waalkes. 1999. The enigma of
arsenic carcinogenesis: Role of metabolism. Toxicol. Sci. 49:5-14.
Hughes, M. F. and E. M. Kenyon. 1998. Dose-dependent effects on the disposition of monomethylarsonic
acid and dimethylarsinic acid in the mouse after intravenous administration. J. Toxicol. Environ. Health.
Part A, 53:95-112.
Hughes, M. F., E. M. Kenyon, B. C. Edwards, C. T. Mitchell, and D. J. Thomas. 1999. Strain-dependent
disposition of inorganic arsenic in the mouse. Toxicology^ 37:95-108.
Hughes, M. F., L. M. Del Razo, E. M. Kenyon. 2000. Dose-dependent effects on tissue distribution and
metabolism of dimethylarsinic acid in the mouse after intravenous administration. Toxicology ^^A 55-
166.
Kenyon, E. M., M. F. Hughes. 2001. A concise review of the toxicity and carcinogenicity of dimethylarsinic
acid. Toxicology^60:227-236.
Kenyon, E. M.,M. F.Hughes, D.L. M. Del Razo, B. C. Edwards, C.T. Mitchell, and O. A. Levander. 1999.
Influence of dietary selenium on the disposition of arsenite and arsenate in the female B6C3FI mouse.
Nutr. Environ. Interact. 3:95-113.
Kitchin, K. T. Recent advances in arsenic carcinogenesis: Modes of action, animal model systems and
methylated arsenic metabolites. Toxicol. Appl. Pharmacol. (in press).
C-2
-------
Kitchin, K. T., L. M. Del Razo, J. L. Brown, W. L.Anderson, and E. M. Kenyon. 1999. An integrated pharma
cokineticand pharmacodynamic study of arsenite action. 1. Heme oxygenase induction in rats. Terato.
Carcino. Mut. 19:385-402.
Lewis, D. R., J. W. Southwick, R. Ouellet-Hellstrom, J. Rench, and R. L. Calderon. 1999. Drinking water
arsenic in Utah: A cohort mortality study. Environ. Health Perspect, 107:359-365.
Lin, S., L. M. Del Razo, M. Styblo, C. Wang, W. R. Cullen, and D. J. Thomas. 2001. Arsenicals inhibit
thioredoxin reductase in cultured rat hepatocytes. Chem. Res. Toxicol. 2001:14:305-311.
Lin, S., W. R. Cullen, and D. J. Thomas. 1999. Methylarsenicals and arsinothiols are potent inhibitors of
mouse liverthioredoxin reductases. Chem. Res. Toxicol. 12:924-930.
Ma, H. Z., Y.J.Xia, K. G. Wu,T. Z. Sun, and J. L. Mumford. 1999. Human exposure to arsenic and health
effects in Bayingnormen, Inner Mongolia. In: Arsenic Exposure and'Health Effects: Proceedings of'the
Third International Conference on Arsenic Exposure and Health Effects, eds. W. R. Chappell, C. O.
Abernathy, and R. L. Calderon, July 12-15,1998, San Diego, CA, New York: Elsevier, pp. 127-131.
Mass, M. J., A.Tennant, B. C. Roop, W. R. Cullen, M. Styblo, D. J. Thomas, and A. D. Kligerman. 2001.
Methylated trivalent arsenic species are genotoxic. Chem. Res. Toxicol. 14:355-361.
Styblo, M., L. M. Del Razo, E. L. LeCluyse, G. A. Hamilton, C. Wang, W. R. Cullen, and D. J. Thomas. 1999.
Metabolism of arsenic in primary cultures of human and rat hepatocytes. Chem. Res. Toxicol. 12:560-
565.
Styblo, M., L. M. Del Razo, L. Vega, D. R. Germolec, E. L. LeCluyse, G. A. Hamilton, W. Reed, C. Wang, W.
R. Cullen, D. J. Thomas. 2000. Comparative toxicity of trivalent and pentavalent inorganic and
methylated arsenicals in rat and human cells. Arch. Toxicol. 74:289-299.
Styblo, M., D. J. Thomas. Selenium modifies the metabolism and toxicity of arsenic in primary rat
hepatocytes. Toxicol. Appl. Pharmacol. (in press).
Styblo, M., and Thomas, D.J.: Selenium modifies the metabolism and toxicity of arsenic in primary rat
hepatocytes. Toxicol. Appl. Pharmacol. 172:52-61, 2001.
Styblo, J., L. Vega, D. R. Germolec, M. I. Luster, L. M. Del Razo, C. Wang, W. R. Cullen, and D. J. Thomas.
1999. Metabolism and toxicity of arsenicals in cultured cells. In: Arsenic Exposure and Health Effects:
Proceedings of the Third International Conference on Arsenic Exposure and Health Effects, eds. W. R.
Chappell, C. O. Abernathy, and R. L. Calderon, July 12-15,1998, San Diego, CA, New York: Elsevier, pp.
311-323.
Tian, D. Z., H. Ma, Z. Feng, Y Xia, X. C. Le, Z. Ni, J. Allen, B. Collins, D. Schreinemachers, and J. L.
Mumford. Analyses of micronuclei in exfoliated epithelial cells from individuals chronically exposed to
arsenic via drinking water in Inner Mongolia, China. J. Toxicol. Environ. Health (submitted).
Thomas, D. J., D. M. Schreinemachers, E. E. Hudgens, M. Ma, X. C. Le, and R. L. Calderon. Urinary
excretion of methylated arsenicals as a function of exposure to inorganic arsenic in drinking water. J.
Exp. Anal. Environ. Epidemol. (in press).
Thomas, D. J., M. Styblo, S. Lin. Toxic consequences of the metabolism of arsenic. Toxicol. Appl.
Pharmacol. (in press).
Thomas, D.J., Del Razo, L.M., Schreinemachers, D.M., Hudgens, E.E., Le, X.C., Calderon, R. L.: Dose-
response relationships for the metabolism and urinary excretion of arsenicals in humans. Proceedings
of Fourth International Symposium on Health Effects of Arsenic (submitted).
Zhong, C., L. Wang, and M. Mass. Arsenite exposure causes both hypomethylation and hypermethylation
in human cell lines in culture at low concentrations. Proceedings of Fourth International Symposium on
Health Effects of Arsenic (submitted).
C-3
------- |