The Coastal Resource Coordinator's Bioassessment Manual

HAZMAT 93-1–Toxicity Tests
Elutriate tests were originally developed for testing dredged material to simulate conditions
occurring during open-water disposal and are not considered appropriate for testing the
toxicity of in-situ sediments. The chemical extraction techniques, used for extraction testing,
remove only certain contaminants so the test organisms are not exposed to the full suite of
contaminants that are actually present in the contaminated sediments. Pore water
techniques require specialized laboratory equipment, and contaminant concentrations may
vary depending on the extraction technique. There are currently no generally accepted
protocols for pore water extraction.
Studies reviewed by Ankley et al. (1991) indicated that pore water exposures provide more
information on sediment toxicity than elutriate exposures. They found that pore water
samples were consistently more toxic than sediment elutriate samples. However, they also
found that pore water samples were sometimes more toxic than bulk sediment samples,
possibly due to pH differences or to the dilution of toxicants by the addition of clean water
to bulk sediment samples (Ankley et al., 1991). Chapman and Fink (1984) also noted
differences between toxicity of bulk sediment and sediment elutriate. Toxicity of bulk
sediment to larval polychaetes was generally greater than that of sediment elutriate.
However, elutriate samples from some stations were toxic, while bulk sediment from the
same stations were not (Chapman and Fink, 1984). Contaminants that have low solubility
in water generally have lower toxicities determined by elutriate tests. Bulk sediment testing
is currently the preferred method for testing sediments at hazardous waste sites to
determine the potential for biological effects at the site. The sediment toxicity tests in the list
of recommended toxicity test protocols (Table 8-1) are based primarily on exposures to bulk
sediments.
Selecting a Test Organism
A wide variety of organisms have been used in toxicity tests. The most commonly used soil
toxicity tests are the seed germination test (typically using common crop species), the root
elongation test (most often performed with lettuce), and the earthworm test. Freshwater
organisms used for water and sediment toxicity tests include algae (Selenastrum), daphnids,
chironomids, amphipods, and fish (especially fathead minnow and rainbow trout). The
most commonly tested marine and estuarine organisms are amphipods, mysids, and bivalve
or echinoderm larvae. Luminescent bacteria have also been used in tests of water, sediment,
and soil.
3-7 August 1997