** Unrted SUtes Science Advisory Board PPA CAO_CDC/~ „-,„«_
Environmental A101 *~«»fa trA-SAB-EPEC-93-002
Protection Agency Washington. DC November 1992
v^xEPA AN SAB REPORT: REVIEW
OF SEDIMENT CRITERIA
DEVELOPMENT
METHODOLOGY FOR
NON-IONIC ORGANIC
CONTAMINANTS
PREPARED BY THE SEDIMENT
QUALITY SUBCOMMITTEE OF THE
ECOLOGICAL PROCESSES AND
EFFECTS COMMITTEE
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
EPA-SAB-EPEC-93-002
November 5, 1992
Mr. William K Reilly
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
RE: SAB Review of Sediment Criteria Development Methodology for Non-
ionic Organic Contaminants
Dear Mr. Reilly,
The Sediment Quality Subcommittee of the Ecological Processes and Effects
Committee of the Science Advisory Board (SAB) has completed its review of
sediment criteria. The review was conducted on June 10-11, 1992. As you are
aware, the SAB has conducted previous reviews of various approaches for
developing sediment quality values. The current methodology is based on the
Equilibrium Partitioning Approach (EqP). In our previous review, the SAB found
that the scientific basis for the concept was valid but recommended that Agency
conduct additional research and testing to evaluate the uncertainties associated
with the EqP-based predictions of field effects.
In May, 1992, the SAB was asked by the Office of Water to evaluate the
Agency's progress in reducing the uncertainties associated with the EqP approach
in light of how the Agency intends to use sediment quality criteria. The .review
was conducted on June 10-11, 1992 and was attended by scientists from academia,
industry, public interest groups, and other government agencies. The
Subcommittee reviewed five draft criteria documents, scientific publications, and
received presentations from the Agency on possible uses of the sediment criteria.
They also received public comments, including a detailed presentation by the US
Army Corps of Engineers.
The Subcommittee commends EPA for its progress in addressing many the
recommendations from the previous SAB reviews. The Subcommittee believes that
EPA has significantly reduced ,fhe uncertainty associated with prediction of
sediment toxicity generated by the EqP methodology, but there are still questions
regarding the application of these estimates to the natural environment. The
Subcommittee concludes that the EPA should proceed according to the following
sequence of events: 1) establish criteria on the basis of present knowledge within
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the bounds of uncertainty discussed in this report; 2) improve the present
knowledge so as to improve the procedures for establishing criteria; and 3)
periodically revisit the criteria to make them more consistent with conditions in
the natural environment.
The Agency should consider how these criteria will be applied in various
program offices. At this tune, the Subcommittee believes that the criteria can be
used to identify three ranges of sediment contamination: 1) concentrations well
below the criterion which are unlikely to have adverse effects, 2) a range well
above the criterion where adverse effects are likely and management is needed,
and 3) a range in between, above and below the criterion, where more information
is needed before a management decision can be made. The dividing lines between
these ranges are vague and the precise location could vary depending on the
intended use among programs. The Subcommittee recommends that these criteria
not be used as a stand-alone, pass-fail value for all applications. The
Subcommittee also recommends that EPA develop minimum data base
requirements for the sediment criteria and prepare a users manual for the
derivation and application of sediment quality criteria.
The Science Advisory Board appreciates the opportunity to review this
important aspect of EPA's environmental quality criteria program and we look
forward to reviewing the Agency's approach to establishing sediment quality
criteria for metals in the future.
Sincerely yours,
__ c. ^^=^
Rayn^md Loehr, Chair-"~~~~~~^ KetmetlTL. Dickson, Chair
Executive Committee Ecological Processes and
Science Advisory Board • Effects Committee
Robert Hugget
Sediment Qualify Subcommittee
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U.S. ENVIRONMENTAL PROTECTION AGENCY
NOTICE
This report has been written as a part of the activities of the Science
Advisory Board, a public advisory group providing extramural scientific
information and advice to the Administrator and other officials of the
Environmental Protection Agency. The Board is structured to provide a balanced
expert assessment of scientific matters related to problems facing the Agency.
This report has not been reviewed for approval by the Agency; and hence, the
contents of this report do not necessarily represent the views and policies of the
Environmental Protection Agency or other agencies in Federal government.
Mention of trade names or commercial products does not constitute a
recommendation for use.
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ABSTRACT
The report represents the conclusions and recommendations of the U.S.
Environmental Protection Agency's Science Advisory Board regarding EPA's
Sediment Criteria Development Methodology. The Review was held June 10-11,
1992 in Arlington, VA by the Sediment Quality Subcommittee of the Ecological
Processes and Effects Committee. The report commends EPA for its progress
toward reducing the uncertainties associated with estimates of safe levels of non-
ionic organic contaminants in sediments using the Equilibrium Partitioning (EqP)
approach. The report supports the EqP concept to develop sediment criteria
where the conditions of equilibrium among the various phases of sediments are
likely. The Agency is cautioned that there are still uncertainties associated with
application of the criteria due to limited field validation data currently available.
It is recommended that EPA use defined ranges of sediment contaminant
concentrations based on the EqP approach that indicate whether or not sediments
are acceptable, unacceptable, or require further evaluation. The Subcommittee also
recommends further testing to improve the method and reduce uncertainty. It is
also recommended that the criteria boundaries be revised periodically to reflect
recent knowledge and experience, and that a document be developed to explain the
derivation, application, and monitoring procedures for the Sediment Quality
Criteria.
KEY WORDS: Equilibrium Partitioning, Sediment Quality Criteria, Uncertainty.
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US ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
SEDIMENT QUALITY SUBCOMMITTEE
CHAIRMAN
DR. ROBERT J. HTJGGETT, Professor, VA Institute of Marine Sciences,
College of William and Mary, Gloucester Point, Virginia
MEMBERS/CONSULTANTS
DR. WILLIAM J. ADAMS, ABC Laboratories, Columbia, Missouri
i
DR. BEN B. EWING, Professor Emeritus, University of Illinois, Champaign-
Urbana
DR. ROLF HARTUNG, Professor, School of Public Health, University of
Michigan, Ann Arbor, Michigan
DR. CHRISTOPHER G. INGERSOLL, National Fisheries Research Center,
Fish and Wildlife Service, Columbia, Missouri
DR. SUSAN LIBES, Department of Marine Science, Coastal College,
Conway, South Carolina
DR. EDWARD LONG, National Oceanographic and Atmospheric
Administration, Seattle, Washington
DR. SAMUEL N. LUOMA, U.S. Geological Survey, Menlo Park, California
DR. FREDERICK K. PFAENDER, Director, Institute of Environmental
Studies, University of North Carolina, Chapel Hill, North Carolina
DR. TERRY F. YOUNG, Environmental Defense Fund, Oakland, California
SCIENCE ADVISORY BOAR.D STAFF
DR. EDWARD S. BENDER, Designated Federal Official, US EPATScience
Advisory Board, 401 M Street, S.W., (A-101F), Washington, D.C. 20460
MRS. MARCIA K JOLLY (MARCY), Secretary to the Designated Federal
Official
in
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TABLE OF CONTENTS
1. EXECUTIVE SUMMARY
2. INTRODUCTION - - 2
2.1 Statement of the Charge *
2.2 Subcommittee Review Procedures 3
3 EVALUATION OF THE EqP APPROACH AND INTENDED
USE • • • : *
3.1 Sources of Uncertainty 4
3.2 Appropriate Uses and Limitations 6
3.3 Additional Comments and Recommendations 9
3.3.1 Limitations for Current Use of the Criteria ..... 9
3.3.2 Future Research to Improve the Method 9
3.3.3 Guidance for using the Criteria
4.
LITERATURE CITED • 12
IV
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1. EXECUTIVE SUMMARY
The Sediment Quality Subcommittee of the Ecological Processes and Effects
Committee of the Science Advisory Board (SAB) met June 10-11, 1992 to review
EPA's Sediment Criteria Development Methodology and evaluate its progress in
addressing the uncertainties associated with the Equilibrium Partitioning (EqP)
approach. In an earlier review (EPA-SAB-EPEC-90-006), the SAB recommended
that the Agency conduct additional research and testing to evaluate more
thoroughly field and laboratory effects and the effect of various chemical
properties on bioavailability.
In this review, the Subcommittee reaffirmed that the EqP approach is
scientifically sound. The Subcommittee considered broad sources of uncertainty
including laboratory measurements to determine the precision or reproducibility of
the EqP and field verification of the values predicted in the laboratory. The
Subcommittee found that EPA had substantially reduced the uncertainty associated
with laboratory measurements. The Subcommittee recommended that EPA set
criteria with ranges of sediment contamination denoting where adverse biological
effects are likely to occur, unlikely to occur, or unknown and further evaluation is
required. This approach recognizes uncertainty that is associated with the theory
and the site specific application, in contrast to pass-fail, single-value criteria. They
also encouraged the Agency to give high priority to developing a chronic sediment
toxicity test and additional field verification of the laboratory predictions. The
Subcommittee recommended further research on bioavailability, sediment
chemistry, and bioaccumulation. It was recommended that EPA provide guidance
on the derivation of sediment criteria and effects of the assumptions, application of
the criteria by various programs, and monitoring for site assessments, trends, or
compliance. The Subcommittee encouraged the Agency to revisit its criteria and
revise the sediment contaminant ranges based on its research and monitoring data.
The Subcommittee also encourages the Office of Water to consider using similar
weight-of-evidence approaches that reflect uncertainties for other environmental
criteria.
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2. INTRODUCTION
The Office of Water has served as a technical manager and focal point for
EPA's development of the Sediment Quality Criteria (SQC). The Agency has
evaluated several approaches to determining these values. It has supported
extramural and EPA laboratory research to develop methods for measuring the
effects of contaminated sediments on aquatic organisms and to validate the
assumptions underlying the equilibrium partitioning (EqP) approach. The Office
of Water is also developing a contaminated sediments management strategy to
coordinate the use of SQC values and biological assays among different regulatory
programs within EPA. The various programs within EPA must deal with
contaminated sediment problems within the bounds of their regulatory statutes,
their policies, and the options that are available for management of those
sediments. The scientific foundation of the EqP and the Apparent Effects
Threshold approaches to developing sediment quality values have been reviewed in
the past by the Science Advisory Board (EPA-SAB-EPEC-90-006 and EPA-SAB-
EEFTC-89-027 respectively). In addition, the SAB has reviewed an Agency
summary of other approaches (EPA-SAB-EPEC-90-018).
At the tune of the SAB review, the potential uses of SQC by EPA programs
were not well defined. In general, the SQC would be the threshold for identifying
the sediment as contaminated. Management alternatives would be program
specific. For example, in monitoring programs, SQC could be used to identify
where sediments are contaminated and pose a threat to benthic organisms, or in
the Dredged Material Management program, SQC could be used as part of the
disposal management decision process.
2.1 Statement of the Charge
The Subcommittee accepted the following charge to guide them in their
review:
Evaluate the Agency's progress in addressing the uncertainties associated
with the Equilibrium Partitioning (EqP) approach, as pointed out in the
SAB review and evaluate how the Agency intends to use the Sediment
Quality Criteria in light of the uncertainties.
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2.2 Subcommittee Review Procedures
The Sediment Quality Subcommittee is a standing Subcommittee of the
Ecological Processes and Effects Committee of the SAB. For this review, expert
scientists were added as liaisons from three federal agencies. The Subcommittee
was provided with the charge, five draft SQC documents (phenanthrene, endrin,
acenaphthene, dieldrin, and flouranthene), technical articles (Bruyn et al (1989)
and Di Toro et al (1991)), and public comments prior to the meeting.
The Sediment Quality Subcommittee met in Washington, D.C. on June 10-
11, 1992. At that time it received briefings on the Agency's response to earlier
SAB recommendations for EqP, the development of SQC, and the intended uses by
the Agency. At the meeting, the Subcommittee received comments from the public
and the U. S. Army Corps of Engineers. Following the meeting, a draft report was
provided to EPA and the public for information.
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3. EVALUATION OF THE EqP APPROACH AND INTENDED USE
The Sediment Quality Subcommittee of the Environmental Processes and
Effects Committee reviewed the Equilibrium Partitioning (EqP) approach to
developing sediment quality criteria (SQC) in 1989. The resulting report (EPA-
SAB-EPEC-90-006 Evaluation of the Equilibrium Partitioning Approach for
Assessing Sediment Quality) raised a number of questions related to the scientific
basis of the technique and suggested that more information was needed before it
could be reasonably used for generation of SQC. The Subcommittee commends
EPA for addressing those questions and suggestions in the subsequent three years.
The results of these efforts have reduced the uncertainties related to utilizing the
EqP approach to establish SQC. There are, however, a number of issues
remaining. This document presents the consensus of the Subcommittee on those
issues.
3.1 Sources of Uncertainty
Toxicity data from laboratory experiments generally fall within a factor of 5
of the toxicity predicted by the EqP. Often the levels differ only by a factor of 2
to 4 and appear to be unbiased. However, limited field data are available to assess
the uncertainty associated with extrapolating values derived by the method to the
natural environment. Thus, the accuracy and reliability of the method has not
been fully characterized.
Nonconformity with theoretical assumptions inherent hi the EqP
methodology may affect the accuracy of the derived criteria when they are applied
to the natural environment. The following are examples of how this may occur: 1)
the extent to which factors other than organic carbon which may influence
bioavailability for non-ionic organic chemicals may vary in the environment, (2)
sensitivity to chemicals may be different between water column arid benthic
organisms in ways which are not affected by the tests used to establish water
quality criteria, (3) not all sediments are in equilibrium with the pore water, (4)
occasionally Kow may not be a good predictor of Koc, (5) partitioning of
contaminants to and from sediments may be kinetic-limited, and (6) short-term
bioassays may underestimate effects observed in long-term or full life cycle
exposures to contaminants. The above points do not negate the EqP method, but
they may limit the reliability and applicability of the approach.
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The EqP methodology assumes that sediment contaminant activities,
predicted by organic carbon normalization, correlate with contaminant
bioavailability. Consideration of bioavailability is an important step in the
development of contaminant criteria. The concept seems reasonably well
supported for the five chemicals evaluated to date (acenaphthene, dieldrin, endrin,
flouranthene, and phenantJhrene). The supporting experiments, however, are
limited to short term (days) bioassays with a few species (mostly arthropods).
Most experiments have been conducted with spiked and/or manipulated sediments
although some recent supportive data also exist from experiments with field-
collected sediments. It is of some concern that, in general, only one experimental
paradigm has been employed to test the concept. As a result, the predictive
capability of EqP-derived criteria has not been demonstrated across a range of
circumstances and field environments. For example, there are few examples of its
applicability in nature to resident species. The Subcommittee recognizes the
challenges inherent in testing the bioavailability hypothesis of EqP in nature with
resident species, but feels efforts to verify this concept in the field should continue,
even as the initial five SQC's are implemented. Field testing need not be limited '
to toxicity tests. It could (and probably should) take the form of appropriate field
bioaccumulation studies, biomarker studies, or studies at population or community
levels of organization.
EPA should be aware of the growing number of studies that point toward
the importance of uptake from food by benthic species for some organic
contaminants (Louma et. al., 1992 and Boese et. al., 1990). Pore water
concentrations, indeed, might allow prediction of bioavailability, in nature, when
all routes of uptake are in equilibrium. The question of whether sediment
associated organic contaminants are at equilibrium in nature is central i~ this
point. The theoretical explanations that suggest that near-equilibrium is common
in sediments are reasonable, although largely untested. Even so, it is possible, and
demonstrated in the case of at least one trace element, (Luoma, et. al., 1992) that
water only toxicity tests in the laboratory will underestimate the exposures
occurring in nature, which may involve several additive routes of exposure. The
above discussion does not dispute that the bioavailability concept is a valuable first
order principle. Rather it emphasizes the need to understand under what
conditions sediment associated organic contaminants are or are not at equilibrium
with respect to the sediment particles, organic carbon, and interstitial water.
As previously mentioned, the Subcommittee recognizes that the EPA has
made progress in quantifying and minimizing the uncertainties associated with
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SQC's derived from the EqP. The uncertainties have diminished largely as a
result of more accurate determinations of the Row's. The Subcommittee
recommends that the EPA continue their efforts to identify and quantify the
sources of uncertainties in EqP derived sediment criteria.
3.2 Appropriate Uses and Limitations
Within the framework of the known uncertainty, it appears that the EqP
method provides a useful sediment assessment tool. The SAB concludes that the
method is sufficiently valid to be used in the regulatory process if the uncertainty
associated with the method is considered, described, and incorporated. For
sediments with contaminant levels outside the boundaries of uncertainty, the EqP-
derived criteria may generally be used to support regulatory decisions; and for
levels within the bounds of uncertainty, confirmatory tests are required. The SAB
concludes that the EqP-derived criteria, if applied properly, are ready for
publication and use.
The Subcommittee recommends that EPA prepare a SQC users manual for
internal and external programmatic uses before the SQC are implemented. The
users manual should identify legislated programs (CERCLA, CWA, MPRSA, RCRA,
301h, NPDES, etc.) to which the SQC's would apply and how they would apply.
Confusion and controversies regarding the proposed uses of the SQC's are
apparent and should be resolved. The users manual should be program-specific
and represent the consensus policy of the Agency. The manual should identify the
significance of exceedances and non-exceedances of the lower and upper confidence
intervals of the SQC concentrations and the anticipated actions (and nonactions)
triggered by those non-exceedances and exceedances. The document should clearly
state the ^appropriate uses of the SQC's, such as mandatory target clean-up
standards, unless additional site specific studies are completed. The Subcommittee
recommends that EPA set a range of values above and below the SQC for which
particular decisions will be made. The manual should also include requirements
for sampling strategies that address the issues of on-site spatial and temporal
variability.
The uncertainty related to the EqP-derived SQC means that there is a
range of sediment chemical contaminant concentration above and below the SQC
in which decisions about the effects of the contaminant are too questionable for
decision-making on the basis' of SQC alone. This concept is illustrated in Figure
1. Since SQC are different for every contaminant, for illustration purposes, the
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SQC values have been "normalized" by plotting the difference between the
concentration of the chemical in the ambient sediment per unit of organic carbon
(Cs^ and the Sediment Quality Criterion, SQC. If the difference is greatly
negative, so that the Cs^ is much smaller than SQC, one can be somewhat certain
that there will be no adverse biological effects. However, if site-specific data
indicate that such a "clean" sediment may cause adverse effects, the biological
information should override the criterion, and EPA should require further
evaluation. Likewise, if the difference is greatly positive so that the contaminant
concentration is much above the SQC, one can conclude that there will be effects
from this contaminant. In either of these cases, the decision may be obvious. For
cases in which the Cs^. is in some indefinite range near the SQC, further
evaluations are necessary. This would be an indication of the need to proceed to
the next testing tier in the ease of dredged material disposal, for example. The
lack of adverse effects from limited field testing of sediments that exceed an EqP
derived criterion should not override the presumption that the sediments
contaminants are adversely impacting the environment. However, given that
sufficient testing (toxicity, bioaccumulation, and field verification) has been
performed the criterion could be overridden or revised.
The vertical locations of the various programs in Figure 1 are jumbled in the
left hand column in order to indicate that there is no effort to suggest that any
one of them has a wider or more narrow range for the questionable zone than
others. It is important that each of these programs have its own lower and upper
limits of the questionable zone. The lower part of Figure 1 indicates that, in the
course of time, further testing and refinement of the SQC procedures may well
result in a general narrowing of the questionable range and possibly a shift in the
value of SQC, and hence also change in the value of Cs,oc - SQC. Likewise, if the
understanding of the biological effects is advanced, the questionable zone may
narrow.
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FIGURE 1. Conceptual sediment management scheme for contaminated sediments
utilizing the EqP-based Sediment Quality Criteria (SQC). On the
horizontal axis, values have been "normalized" by plotting the
difference between the concentration of the chemical in the
ambient sediment per unit of organic carbon (Csoc) and the SQC.
Csoe--SQC
Positive
/'.'iSly-"^'7.--*'^
CONFIDENT j
Sediments
OK
->--'••:- QUESTIONABLE ~-.>tV
'.'. ^ Further
*»••..„ Data
' ^ • Required 3i-;~c.-
• '•* -
ADDITIONAL
INFORMATION
%,
CONFIDENT
Sediments
OK
CON
Sediments
.Not OK
- i
-Further --
Data
•.Required ?.
Pooov*
8
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In summary, the scientific rationale underlying the EqP-based SQC is
sufficiently valid that it can be used in sediment management decisions for the five
chemicals presented. The use of the SQC's as stand-alone, pass-fail criteria is not
recommended for all applications. Rather, they should be used along with other
tools as guidance in management and regulatory decisions. The use of the SQC's
should not preclude the use of biological effects testing.
3.3 Additional Comments and Recommendations
3.3.1 Limitations for Current Use of the Criteria
a) The EqP method requires equilibrium conditions on the sediments. It
should be used only with extreme caution for sediments in zones of
rapid deposition or erosion. In these cases the assumption of
chemical equilibrium between the sediment and the pore water may
not be valid (e.g., areas where more than 10 cm/yr is deposited such
as dredge disposal areas, barge and boat impacted areas, and some
river channels).
b) The SAB concludes that the EqP method should not be applied to
broad classes of compounds or mixtures if one Kow value is used to
represent the entire class or the mixture.
3.3.2 Future Research to Improve the Method
a) The Subcommittee recommends that, in support of both the
development of SQC's and the overall Sediment Management
Strategy, the EPA should develop appropriate chronic (life cycle)
sediment toxicity tests to use in the SQC validation process. Since
the SQC's are based upon chronic and acute sediment water toxicity
tests, the laboratory validation and field verification tests should be
conducted with chronic life cycle end-points.
b) Field verification studies are needed to evaluate the accuracy and
reliability of the SQC method. These should include both new studies
and greater use of existing data from contaminated sites where both
contaminant and species presence/absence data are available.
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c) Additional measurements of chemical concentrations in interstitial
water from natural sediment samples are needed. Those values
should be compared to predicted values for the same sediments. The
effects of dissolved organic carbon should be evaluated in these
studies of the distribution of contaminants between sediments and
interstitial water.
d) Additional research is needed to evaluate the relative significance of
factors other than organic carbon which may affect bioavailability.
The principal work cited by the Agency for the conclusion that carbon
dominates the sorption process for various size fractions of sediment
does not agree completely with the conclusions of the Prahl study
(1982). It is recommended that additional sorption studies be
performed to define the boundaries of the utility of organic carbon for
normalizing sediment concentrations for non-ionic organic chemicals.
Presently it is thought that the lower boundary ranges from 0.2 to
0.5% and the upper boundary is about 10 to 12% organic carbon.
e) Bioaccumulation from food and kinetic limitations on contaminant
bioaccumulation need to be further evaluated, and their relevance
determined, for both equilibrium and non-equilibrium situations.
f) Additional work by the Agency is required to establish how mixtures
of contaminants hi sediments should be handled. Most contaminated
sites contain a variety of materials that could have a biological
impact. Conceptually and practically, how should SQC be determined
for such sediments? Work in this area needs to be continued and
expanded.
g) The time and space scales over which sediment quality criteria
generated by the EqP model are valid should be assessed. These time
and space scales are likely to be site specific. For example, oyster
reefs influence the rates of sediment deposition and they have very
patchy distributions. They also harbor a diverse community of
organisms, including species that may be particularly sensitive to
contaminants or accumulate them efficiently.
10
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3.3.3 Guidance for using the Criteria
a) The Subcommittee recommend? that the EPA prepare a methods
manual for the derivation the EqP-based SQC's. This manual should
include a description of the: (a) step-wise process for derivation of the
criteria; (b) the acceptable uncertainties in the Kow factors; (c) the
acceptable analytical error in the chemical analyses performed in
support of the Kow coefficient derivations; (d) the minimum
acceptable water-toxicity data base necessary for derivation of SQC's;
and (e) the minimum acceptable degree of agreement in sensitivities
between the benthic animals to which the SQC's would apply and the
pelagic/planktonic animals from which they were derived. The
manual should include the minimum acceptable level of effort to
validate the criteria with laboratory spiked-sediment bioassays and to
verify the criteria with field-collected data. It should also describe the
assumptions used in the derivation of SQC and their possible effects
on the application of SQC and the sources of uncertainty for EqP-
derived criteria. Further, the Agency should establish "Minimum
data" requirements for determining a SQC when Water Quality
Criteria for that substance does not exist. The Subcommittee
recommends that the guidelines for deriving numerical national
sediment quality criteria should outline the minimum database
requirements for toxicity, chemistry,, and bioavailability. The
minimum date requirement should be specified for the number and
type of benthic species used in the derivation of final acute values,
final chronic values, and sediment bioavailability.
b) EPA should publish guidelines for sediment monitoring including
rules regarding spatial averaging of sample results.
c) There does not appear to be a consensus within EPA on how
reference area definition and characterization for dredged material
should be approached. The Subcommittee is concerned that the EqP
method could be used too conservatively or too liberally, depending on
how the reference site is chosen. EPA should consider whether
reliance on a reference area site should be maintained given that a
single definition seems elusive at this time.
11
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4. LITERATURE CITED
1. Boese, B.L., H. Lee, D.T. Specht, R.C. Randall, and N.M. Winsor. 1990.
Comparison of aqueous and solid-phase uptake for hexachlorobenzene in the
Tellinid clam Macoma nasuta (Conrad): A mass balance approach. Environ.
Toxieol. Chem. 9:221-231.
2. De Bruyn, J., F. Busser, W. Seinen, and J. Hermens. 1989. Determination of
Octanol/Water partition coefficients for hydrophobic organic chemicals with the
"slow-stirring" method. Environ. Toxicol. Chem. &499-512.
3. Di Toro, D.M., C.S. Zarba, D.J. Hansen, WJ. Berry, R.C. Swartz, C.E. Cowan,
S.P. Pavlou, H.E. Allen, N.A. Thomas, and P.R. Paquin. 1991. Annual Review.
Technical basis for establishing sediment quality criteria for nonionic organic
chemicals using equilibrium partitioning. Environ. Toxicol. Chem. 10-1541-1583.
4. Karichoff, S.W., V.K. McDaniel, C. Melton, A.N. Vellino, D.E. Nute, and LA.
Carreira. 1991. Predicting Reactivity by computer. Environ. Toxicol. Chem.
1&1405-1416.
5. Luoma, S.N., C. Johns, N.S. Fisher, NA. Steinberg, R.S. Oremland, and J.R.
Reinfelder. 1992. Determination of selenium bioavailability to a benthic bivalve
from particulate and solute pathways. Environmental Science and Technology
2j£:485-491.
6. Pahl, F.G. 1982. The geochemistry of polycyclic aromatic hydrocarbons in
Columbia River and Washington coastal sediments. Ph.D. Thesis. Washington
State University, Pullman, WA.
12
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