9.4.1 Tier III - Plant Survival and Growth

9.4.1 Tier III - Plant Survival and Growth

The initial information of interest is whether or not plants will grow on the

dredged material. This is usually not a concern with dredged material disposal in

a CDF unless plant cover is part of the management strategy for aesthetics, to

minimize surface water runoff, for habitat, or other reasons. Obviously, plant

bioaccumulation would not be a concern if plants were unable to survive in the

CDF because of toxicity from salts, metals or organic contaminants, low pH, or

other plant-limiting soil conditions. However, toxicity to plants is a flag that may

indicate a potential need to carefully manage the site to include possible control

measures for other pathways such as surface runoff or animal bioaccumulation.

The procedure can be used to determine the plant growth on dredged material

in both saturated (wetland) and air-dried (terrestrial) habitat conditions. Except for

leaching of salts for the evaluation of saline dredged material under terrestrial

conditions, no other processes to enhance plant growth are conducted. The

specific use of index plants is described in the next section. A control sediment or

soil is included in the test for the usual purposes of a laboratory control, and a

reference sediment or soil is included to provide a point of comparison for

evaluation of the test results.

9.4.2 Tier III - Plant Bioaccumulation of Contaminants

The plant bioaccumulation test procedure addresses geochemical changes in

dredged material in a CDF and the subsequent bioaccumulation of COC by plants

growing on the dredged material. The procedure is described by Folsom and

Price (1989) for plants in freshwater dredged material under terrestrial and

wetland habitat conditions, by Lee et al. (1992a, 1992b, 1993a and 1993b) for

plants in saltwater dredged material under terrestrial habitat conditions, and by

Lee et al. (2000) for plants in saltwater dredged material under wetland habitat

conditions.

The plant bioaccumulation procedure consists of the exposure of index plants

to dredged material and to a reference soil or sediment. The dredged material and

reference material are (1) prepared to simulate wetland (saturated) habitat

conditions, or (2) processed by drying and oxidation to simulate terrestrial habitat

conditions, then planted with seedlings of the appropriate specie. Spartina

alterniflora is used for saltwater wetland habitat conditions. Cyperus esculentus

is used for saltwater terrestrial, freshwater wetland, and freshwater terrestrial

habitat conditions. The procedure calls for growth of the plant through vegetative

maturity on the sediment in an environmentally controlled greenhouse.

Aboveground plant tissues are harvested and analyzed for COC concentrations.

Concentrations of COC in tissues of plants grown in the dredged material are

statistically compared to the concentrations in tissues of plants in the reference

material to determine whether there is an indication of greater bioaccumulation

from the dredged material than from the reference. Because the reference material

is carefully selected to represent acceptable conditions, whatever bioaccumulation

it may cause is an acceptable level of plant bioaccumulation.

9-10

Chapter 9

Plant Bioaccumulation