The Coastal Resource Coordinator's Bioassessment Manual

HAZMAT 93-1–Toxicity Tests
Testing Water, Soil, or Sediment
Toxicity tests have been developed that
expose test organisms to water, soil, or
sediment. In water toxicity tests, the
test organisms are placed directly in a
sample of the water of concern.
However, there are four different
exposure scenarios for soil or sediment
toxicity tests. First, organisms can be
exposed to whole, intact soil or
sediments ("bulk sediment" or the "solid
phase") with, in the case of sediments,
overlying clean water. Second, they can
be exposed to soil or "sediment
elutriate" where clean water is mixed
with the test material. The mixture is
then either allowed to settle or is
centrifuged and the water phase is
poured off to become the test sample.
This elutriate sample contains the
"suspended phase" if it still contains
particulates, or is the "liquid phase" if
the particulates have been removed by
centrifugation or filtration.
The third scenario is exposing
organisms to soil or sediment extracts,
Table 3-2. Steps in toxicity test selection.
DEFINE TEST OBJECTIVES
DETERMINE ECOSYSTEM TYPE
Terrestrial
Freshwater
Brackish (Estuarine)
Marine
DETERMINE MATRIX TO BE TESTED
Soil
Water
Sediment
Bulk
Elutriate
Extract
Pore Water
DETERMINE TYPE OF TEST DESIRED
Acute
Chronic
SELECT TEST ORGANISM
DEFINE ENDPOINTS TO BE OBSERVED
Death
Growth
Reproduction
Etc.
using a chemical extraction procedure similar to that used for sediment chemistry analyses.
This extraction process isolates specific classes of contaminants (neutral, non-ionic organic
compounds) while failing to extract others (metals and highly acidic and basic organic
compounds). The fourth, relatively new technique involves exposing organisms to the
interstitial or pore water present in a sediment sample. Pore water can be collected from
wet bulk sediment through the use of centrifuges, squeezers and filters, or dialysis
chambers. After the pore water is collected, water toxicity tests can be used. Although
3-5 August 1997