Environmental Engineering Reference
In-Depth Information
the food web (Crane 1996). Therefore, sediment
chemistry represents an important indicator for
assessing the potential effects of COPCs on human
health. The bioaccumulation-based SQGs for the
protection of human health that were developed by
the New York State Department of Environmental
Conservation (NYSDEC 1999) and the Washington
State Department of Health (1995, 1996) provide a
basis for establishing sediment quality targets rela-
tive to the protection of human health.
The choice of a test organism has a major infl uence
on the relevance, success, and interpretation of a test.
As no one organism is best suited for all applications,
considering the intended uses of the resultant data is
important in the selection of toxicity tests. The fol-
lowing criteria were considered in the selection of the
methods and species that were to be described in
ASTM (2008a) and USEPA (2000a) (Tables 7.4 and
7.5). Ideally, a test organism should:
•
have a toxicological database demonstrating rela-
tive sensitivity and discrimination to a range of
COPCs in sediment;
•
have a database for inter-laboratory comparisons
of procedures (for example, round-robin studies);
•
be in contact with sediment (e.g., water column
versus sediment-dwelling organisms);
•
be readily available through culture or from fi eld
collection;
•
be easily maintained in the laboratory;
•
be easily identifi ed;
•
be ecologically or economically important;
•
have a broad geographical distribution, be
indigenous to the site being evaluated (either
present or historical), or have a niche similar to
organisms of concern at the site (for example, similar
feeding guild or behavior to the indigenous
organisms);
•
be tolerant of a broad range of sediment physico-
chemical characteristics (for example grain size);
and,
•
be compatible with selected exposure methods and
endpoints; the method should also be peer reviewed
and confi rmed with responses with natural popula-
tions of benthic organisms.
Of these criteria, a database demonstrating relative
sensitivity to contaminants, contact with sediment,
ease of culture in the laboratory, inter-laboratory
comparisons, tolerance of varying sediment physico-
chemical characteristics, and confi rmation with
responses of natural benthos populations were the
primary criteria used for selecting the amphipod
Hyalella azteca
and the midge
Chironomus dilutus
for describing test methods for freshwater sediments,
as outlined by ASTM (2008a) and USEPA (2000a)
(Table 7.4). Procedures for conducting sediment
tests with oligochaetes, mayfl ies, and other amphi-
pods or midges are also outlined in ASTM (2008a)
and in Environment Canada (1997). However,
USEPA (2000a) chose to not develop methods for
7.3.2 Selection of metrics for whole-
sediment and pore-water toxicity testing
The objective of a sediment toxicity test is to deter-
mine whether contaminated sediments are harmful
to benthic organisms (USEPA 2000a, ASTM 2008a).
These tests can be used to measure the interactive
toxic effects of complex chemical mixtures in sedi-
ment. Furthermore, knowledge of specifi c pathways
of interactions among sediments and test organisms
is not necessary to conduct the tests. Sediment tests
can be used to: (1) determine the relation between
toxic effects and bioavailability; (2) investigate
interactions among chemicals; (3) compare the
sensitivities of different organisms; (4) determine
spatial and temporal distribution of contamination;
(5) evaluate hazards of dredged material; (6)
measure toxicity as part of product licensing or
safety testing; (7) rank areas for clean up; and
(8) estimate the effectiveness of remediation or
management practices.
The results of sediment toxicity tests can be used
to assess the bioavailability of contaminants in fi eld-
collected sediments. The responses of organisms
exposed to fi eld-collected sediments are often com-
pared with the response of organisms exposed to a
negative control material and/or to appropriately
selected reference sediments. The results of toxicity
tests on sediments spiked with one or more chemicals
can also be used to help establish cause and effect
relations between chemical concentrations and bio-
logical responses. The results of toxicity tests with
test materials spiked into sediments at different con-
centrations are often reported in terms of a median
lethal concentration (LC
50
), a median inhibition con-
centration (IC
50
), a no observed effect concentration
(NOEC), or a lowest observed effect concentration
(LOEC) (USEPA 2000a; ASTM 2008a).
