CHARACTERIZATION TESTS USEFUL IN DETERMINING BIOLOGICAL PROPERTIES

Technical Note DOER-C2

May 1999

Sulfur. Sulfur is generally taken up by plants in the form of sulfates and is often supplied from

the decomposition of organic matter or soluble minerals. Although sulfur-deficient soils are not

very common, sulfur is a necessary constituent of three essential amino acids. The amount of sulfur

required is dependent on the target vegetation.

Contaminants. The presence of contaminants (metals, pesticides, PAHs, PCBs) in dredged

material is a concern. These substances generally sorb to the sediment particulates (i.e., organic

matter, clay particles, aggregates, hydrous oxides) and settle out in the anaerobic (reduced) alkaline

environment existing on the bottom of waterways. The solubility, mobility, and bioavailability of

these contaminants are generally reduced under anaerobic alkaline conditions. However, the

dredged material can become oxidized and more acidic during dredging and placement into CPFs.

The potential then exists for sorbed contaminants to become solubilized, mobile, and bioavailable.

Analyses need to be conducted to determine if contaminants have become solubilized and bioavail-

able (i.e., DTPA, biological screening tests). Then the appropriate corrective measures can be taken

to prevent adverse environmental impacts.

Surface Runoff Quality and Leachate Quality Tests. The potential exists for solubilized

contaminants in the dredged material to migrate offsite during and after placement into upland sites.

As the dredged material dries out and becomes oxidized, the potential exists for contaminants to

become soluble, mobile, and bioavailable. During precipitation events, water percolates through

the dredged material, and contaminants can migrate in the runoff and be carried into surface-

receiving waters. Chemical analyses are conducted on surface runoff waters when there is concern

about contaminants that have established water quality criteria (WQC), and/or a biological evalu-

ation is conducted for those contaminants that have no established WQC. The leachate quality test

is used when the potential exists for contaminants to enter surface-receiving waters or groundwaters.

The leachate quality test evaluates the potential for adverse impacts from (a) seepage from dikes

into a receiving water body, (b) subsurface drainage into an aquifer used for drinking water,

and (c) seepage into nonpotable subsurface water. The results of both tests should be compared

with the quality of an appropriate reference surface water or groundwater source. Methods and

appropriate characterization tests for determining chemical properties are listed in Table 2.

CHARACTERIZATION TESTS USEFUL IN DETERMINING BIOLOGICAL PROPERTIES:

Biological tests are conducted to assess the potential for adverse effects to occur in biological

indicator organisms as a result of exposure to contaminants in the dredged material. These tests

integrate existing conditions in the dredged material and evaluate the bioavailability of contami-

nants in the dredged material. The chemical species (form) of contaminants determine their

bioavailability and potential for uptake, bioaccumulation, and toxicity once they reach their site of

action in living organisms, not simply their presence in dredged material. Elutriate bioassays are

conducted to assess/evaluate the bioavailability and potential toxicity of contaminants that are either

adsorbed on particle surfaces (can be easily washed off or eluted) or solubilized in pore waters.

The manufactured soil test and plant/animal bioassay are designed to determine if adverse (toxicity)

effects occur in test organisms as a result of exposure to contaminants in the dredged material. The

responses of dicot and monocot plant species are evaluated during the plant bioassay, and the

optimum combination of dredged material, carbon source, and organic waste amendments is

assessed using the manufactured soil test. Test conditions can be controlled or varied to simulate

those expected to be encountered under field situations (upland or wetland) so that the data obtained