Substrates

ERDC TN-DOER-R3

September 2004

For C18 disks:

Sorption, as measured by the disk-organics concentrations accumulated in 28 days, in

mg kg-1 DW.

Substrates. Two dredged materials (DM) were used in the tests. The contaminated DM from

the field site was chosen because of the interest of the U.S. Army Corps of Engineers. The latter

DM was obtained from an area planned for dredging and disposal in CDFs. It was collected in

1991 from the Indiana Harbor Canal (IHC), IN (Figure 1), and stored in a 55-gal drum in a wet

state at room temperature until use. The IHC DM contained significant amounts of polychlori-

nated biphenyls (PCBs, i.e. Arochlor 1248) and polyaromatic hydrocarbons (PAHs), but also

high levels of the metals cadmium (Cd), chromium (Cr), nickel (Ni) and zinc (Zn). The reference

DM originated from the nearby Monroe, MI, CDF, where it was excavated from the substrate

surface to a depth of 0.33 m at a dry site, in June 2002. DM from the same site was used as a ref-

erence in two earlier bioassays (Best et al. 2001; 2003). Properties of both DMs are listed in

Table 1. Both DMs were dried to a moisture content of approximately 5 percent, and ground to

pass a 2-mm sieve. During this process, part of the volatile PAHs was lost from the IHC DM,

amounting to 96 percent for naphthalene and 70 percent for acenaphthene and fluorene.

The substrate dilution series was constructed by mixing different amounts of IHC DM with ref-

erence DM (Table 1). A range of four dilutions up to approximately 70 percent IHC DM was

created, containing 46 mg kg-1 DW Arochlor-1248 and 336 mg kg-1 DW PAH. Dilutions were

used because it was expected that the high metal concentrations in the IHC DM would cause

acute toxicity in the test organisms, and thus prevent determination of bioaccumulation of

organic contaminants in the plants and worms.

As a control substrate for plants, Baccto R Lite potting soil, Michigan Peat Company, Houston,

TX, was used. As a control substrate for worms, a standard artificial soil (Organization for Eco-

nomic Cooperation and Development (OECD), Paris, France; Kula and Larink 1998) was used.

Plant Tests. The plant tests used the following treatments:

Percent IHC DM: Five levels:

-1

o Reference (0 mg A-1248, and 0.32 mg PAH kg DW)

-1

o 10 percent (10 mg A-1248, and 66.1 mg PAH kg DW)

-1

o 20 percent (17 mg A-1248, and 114.7 mg PAH kg DW)

-1

o 33 percent (24 mg A-1248, and 183.2 mg PAH kg DW)

-1

o 70 percent (46 mg A-1248, and 336.3 mg PAH kg DW)

Moisture: Two levels:

o Approximately 1/3 field capacity (15 percent)

o Close to field capacity (36 percent, field capacity being 38 percent). A moisture level

at field capacity allows maximum mobility of contaminants in soil solution.