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OCR for page 38
NATIONAL PERSPECTIVE ON SEDIMENT QUALITY
Christopher Zarba
U.S. Environmental Protection Agency
ABSTRACT
To address the growing concerns on the effects of contam-
inated sediments on aquatic life, wild life, and human
health, the U.S. Environmental Protection Agency (EPA)
placed greater emphasis on development of a regulatory mech-
anism to aid in evaluating and making decisions concerning
contaminated sediments. Started in 1984, one of the first
activities conducted under this effort was a national
assessment of the scope of contaminated sediments. At that
time, need and available resources did not warrant exhaus-
tive study of the extent of contaminated sediments; however,
to focus future activities a general assessment was needed.
EPA Storage and Retrieval System (STORET) data was used (and
supplemented with data from the literature) to provide a
partial picture of distribution of some commonly found chem-
icals in sediments and to identify chemical concentrations
associated with contaminated sediments on a national basis.
The following identifies the findings of the national
assessment study.
SEDIMENT QUALITY ASSESSMENT AND REGULATION
The Environmental Protection Agency's (EPA) Criteria and Standards
Division (CSD) develops and revises criteria, regulations, standards,
r
and guidelines in support of the mandates of the Clean Water Act. The
CSD has published water quality criteria for 65 priority pollutants and
pollutant categories. These criteria are based on an assessment of
water column pollutant concentrations, which--if not exceeded--will pro-
tect designated uses of a water body and 95 percent of the aquatic life
from adverse effects. The EPA recognizes that while ambient water qual-
ity criteria are an important component in assuring a healthy aquatic
and human environment, contaminated sediments may be responsible for
significant adverse effects even though water quality criteria are
being met.
To meet the growing need for a regulatory tool that could be used
in assessing and making decisions concerning contaminated sediments, a
sediment criteria development effort was undertaken by CSD. One of the
These criteria are based on an assessment of
38
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39
first activities conducted in this effort was development of a better
understanding of the scope of contaminated sediments on a national
basis. A national assessment on sediment quality was conducted. While
this national assessment of sediment quality was not intended to be an
exhaustive study, it was intended to provide those responsible for
directing and focusing sediment criteria development activities with a
clearer picture on the extent of the problem.
The assessment was conducted using a total of 48 chemical contam-
inants representing a diverse group of naturally occurring and anthro-
pogenic materials indicative of compounds of increasing environmental
concern. This list is not intended to be exhaustive, but rather is
illustrative of the types of chemical data available for sediment.
The seven chemical categories identified are
polynuclear aromatic hydrocarbons,
2. pesticides,
3. chlorinated hydrocarbons,
4. mononuclear aromatic hydrocarbons,
S. phthalate esters,
6. metals, and
7. miscellaneous.
Threshold concentrations were then developed to judge differences
in the levels of various chemicals in sediments. The majority of these
values were calculated using the methodology of the Sediment-Water
Equilibrium Partitioning Approach.
To do this the assumption was made that the distribution of a chemi-
cal between the organic carbon phase of the sediment and the soluble
phase in interstitial water in equilibrium with the solid phase is
determined by the organic carbon-water partitioning coefficient (Kook)
for the chemical. If the water quality criterion value for the chemi-
cal is taken to be the maximum acceptable concentration of the chemical
in solution in the interstitial water, then the threshold concentration
of the chemical in the bulk sediment is calculated based on the sedi-
ment organic carbon-normalized KoC for the chemical.
This allows for a numerical threshold to be established against
which available monitoring data can be compared. The nonjudgmental use
of this approach allows the distribution of the data set into percent-
iles above and below the threshold even though one might question the
significance of the results relative to the observed integrity or lack
of integrity of biological communities.
Threshold values derived from the sediment-water partitioning
approach are based on the organic carbon content of the particular sed-
iment (Table 1~. These values were adjusted to a whole sediment basis
on the assumption that an average sediment contains 4 percent organic
carbon. Furthermore, the values are compared to the monitoring data on
a dry weight equivalent basis. For several chemicals, for which no
acute and chronic water quality criterion values are available, other
toxicological endpoints were used.
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40
TABLE 1 Contaminants Reviewed and Developed Threshold Values
Threshold value Threshold value
Contaminants mg/kg Contaminants mg/kg
Polynuclear aromatic Monoaromatic hydro-
hydrocarbons carbons
benzoapyrene 1,800 toluene 10
naphthalene 42 benzene 1.36
phenanthrene 56 ethylbenzene 5.6
chrysene 460 nitrobenzene 6.6
fluorene 28 dinitrobenzene 0.88
acenaphthene 66
anthracene 44 Phthalates
benzoaanthracene 220 butylbenzyl phthalate 220
acentphthalene 24 di-N-butylphthalate 2,000
indeno(l,2,3-CD) diethylphthalate 1.28
pyrene 24,000 dimethylphthalate 1.96
benzod
fluoranthene 5,000 Metals
arsenic 33
Pesticides cadmium 31
lindane 0.012 copper 136
DDD 13 lead 132
DDE 28 mercuryb 0.8
aldrin 0.021 zinc 760
isophrone 9.6 chromiume 25
DDT 0.006 nickele 20
chlordaneb 0.020
toxapheneb 0.020 Miscellaneous
heptachlorb 0.020 cyanide 0.1
Chlorinated hydrocarbons
hexachloroethane 14.4
hexachlorobutadiene 1.28
tetrachloroethylene 1.8
trichloroethylene 6.4
dichlorobenzene 2.8
methylene chloride 2
PCBsC 0.28
NOTES:
aThreshold concentrations are those determined by the EPA/OWRS unless
otherwise stated. Criteria for organic contaminants are calculated on
the basis of 4 percent organic carbon content of sediment.
bU.S. Geological Survey sediment alert levels.
CBased on criterion for hexachlorobiphenyl.
~he value of 0.8 was not corrected for organic carbon. Correction
of this value would have resulted in a mercury concentration of 0.03.
which is considerably lower than the concentration of this metal in
most sediments.
eEPA Region V guidelines for designating contaminated verses noncon-
taminated sediments.
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41
The methods used to evaluate the level of various chemicals in sedi-
ments of fresh waters, marine waters, and estuaries was consistent to
the extent that the data search included the same chemical and selected
threshold values.
To compare the monitoring data, the concentrations were divided for
convenience into four subranges:
level 1, less than threshold value;
level 2, 1-3 times threshold value;
level 3, 3-10 times threshold value; and
level 4, greater than 10 times threshold value.
THE DATA BASE
Due to the limitations of the EPA Storage and Retrieval System
(STORET) data base for this type of analysis, it is likely that there
are numerous additional areas with significant contaminant levels that
are not represented in this report. Figures 1, 2, and 3 depict loca-
tions where contaminants were at levels 3 and 4.
Freshwater Data
A very large data base was available for evaluation of contamina-
tion of sediments in streams, rivers, lakes, and reservoirs. The
STORET system was the primary source of data for this effort. Of the
group of 48 chemicals identified initially, data on 22 were obtained
from the STORET system and over 255,000 data records were processed.
No attempt was made to judge the quality of these data or the accuracy
and precision of the analytical techniques used to obtain them.
Marine/Estuarine Data
Concentrations of various chemicals in marine and estuarine sedi-
ments were obtained from the published literature and from some litera-
ture with limited distributions. An additional set of referenced data
points was derived from STORET data files. Marine/e stuarine STORET
data were limited to median concentrations of various chemicals. No
ranges of concentrations were given and the data base was sufficient to
manipulate data.
OBSERVATIONS AND CONCLUSIONS
Fresh Water
There was a clustering of a variety of chemicals at certain sites
rather than a general scattering of data. In general, coastal areas
were the most noticeably affected regions. New York, New Jersey,
OCR for page 42
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OCR for page 45
45
Michigan, Arizona, Nevada, Washington, and California contain areas
which were repeatedly identified as contaminated. This distribution
indicated a broad spectrum of contamination within certain areas.
The limited analysis of station-by-station data for the top 200
measurements indicate that (1) areas are widely scattered around the
country, justifying development of sediment criteria on a national
basis, and (2) the highest contamination levels for many chemicals
represent potential hot spots rather than general high concentrations
over a broad area.
Metal concentrations were, for the most part, classified in level
1. Only nickel, which had 42 percent of the data in the upper three
concentration levels, was an exception. In situ and bioassay data sug-
gest a need to reevaluate threshold values derived from water quality
criteria.
Almost all of the PAN data were classified in level 1.
A wide span exists between the currently suggested threshold values
and even the highest observed concentrations. The biological impact
data suggest a need to reevaluate threshold levels.
A significant percent of phthalate data fell in the higher classifi-
cation levels: 36 percent for diethylphthalate and 35 percent for
dimethylphthalate. However, no biological impact data were found to
indicate a need to review threshold values.
The vast majority of the pesticide data were in the level 1 range.
Chlordane, DOT, and toxaphene had 16, 7, and 14 percent of the data
points in the level 2 range, respectively. Biological impact data indi-
cated a need to reevaluate threshold levels.
The PCB data were distributed with 18 percent of the data above
level 1. However, only 0.04 percent would be located in level 2 at the
highest proposed threshold value using alternative criteria. There is
a need for further evaluation using biological impact data.
Much of the available in situ or in viva data were inappropriate to
determine sediment-related toxic effects, because parallel measurements
of chemical concentrations and biological species distribution of other
biological effects have not been made.
Marine/Estuartne Waters
The principal sites that contained chemicals of interest at high
concentrations include Puget Sound waterways, Corpus Christi Harbor,
New York Harbor, Baltimore Harbor, Boston Harbor, New Bedford Harbor,
Blackrock Harbor, the California sewage outfalls at Palos Verdes, and
parts of San Francisco Bay.
Chemicals of major concern were those that exceeded the provisional
sediment threshold values of several coastal locations. These chemi-
cals include toxic metals, PAR, PCBs, and DOT. Other chemicals in this
inventory of coastal sites did not reach or exceed the first-cut sedi-
ment threshold values.
The marine/c stuarine survey was based on a very limited data base.
A more detailed literature search may reveal additional chemicals of
major concern.
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46
Threshold concentrations for chemicals in sediments based on
sediment-water equilibrium partitioning are probably set too high for
the majority of chemicals considered, most notably for PAR compounds
and metals. This overestimation was best illustrated by the
discrepancy between biological effects observed in New York Bight
sediments, despite corresponding sediment contaminant concentrations of
inventoried chemicals that rarely exceed threshold biological effects
levels.
ACKNOWLEDGMENT
The material presented in this paper is a summary of material pre-
sented in the EPA document "National Perspective on Sediment Quality."
This document was assembled in 1985 and in many cases reflects the
state of knowledge on toxic sediments at that time. If this document
were updated. changes in the conclusions identified above would be
likely. For copies of the document or for additional information con-
tact Christopher Zarba at (202) 47S-7326.
Representative terms from entire chapter:
threshold values
