MATERIAL AND METHODS

ERDC TN-DOER-R3

September 2004

(yellow nutsedge), frequently used for DM testing, was not used for the current tests, because

attempts to enhance and synchronize germination of its tubers were unsuccessful.

The earthworm E. fetida was selected for its worldwide use and acceptance, facilitating compari-

son with bioaccumulation and toxicity data of other sites, and ease of culture under laboratory

conditions. E. fetida and E. andrei, the most used laboratory test species, exhibit a litter-dwelling

ecological strategy, live in organic matter-rich soil, and reproduce via cocoons. Toxicological

effects in these test organisms originate largely from direct skin contact with the toxic com-

pounds in the interstitial water. Earthworms are suitable bioaccumulation and response indicators

for metals as well as HOCs (ASTM 1998; Kula and Larink 1998; Lokke and Van Gestel 1998).

Jager (1998) discusses earthworm ecological strategies and models to estimate the bioconcentra-

tion of organic chemicals by earthworms.

Study Objectives: The current study is aimed at identifying/validating suitable herbaceous

plant and worm species as test organisms for organic contaminants in DM from freshwater ori-

gin. The specific objectives were to evaluate in terrestrial plants and worms:

(1) Bioaccumulation of organic contaminants from organics-contaminated DM.

(2) Chronic toxicity, as indicated by decreasing biomass on organics-contaminated DM.

MATERIAL AND METHODS

Bioaccumulation and Toxicity Assays. A dilution series was constructed by mixing Indi-

ana Harbor Canal (IHC) DM with reference DM. Subsequently, dose-response curves for organ-

ics concentrations between 0 and 70 percent IHC (46 mg Arochlor-1248 kg-1 dry weight (DW)

and 336 mg PAH kg-1 DW) were constructed for both plant and animal tests. Plant and animal

tests were replicated five times, and followed a randomized block design. Desorbability of the

organic contaminants, as a measure for potential bioavailability, was evaluated using C18 disks,

replicated three times. No factors other than percent IHC-DM contribution to the test substrate

were tested because only a limited amount of IHC-DM was available. DM with concentrations of

<1 mg PCB kg-1 DW (Monroe CDF, MI; Best et al. (2003)) and 115 mg PAH kg-1 DW may be

considered representative for DM from harbors similar to IHC (Milwaukee Harbor, Talley et al.

2002).

The following responses were measured:

For plants:

Accumulation, as measured by the plant tissue-organics concentrations accumulated

in 59 days, in mg kg-1 DW and in mg kg-1 organic carbon (OC).

Toxicity, as measured by the plant biomass formed in 59 days, in g DW m-2.

For worms:

Accumulation, as measured by the worm tissue-organics concentrations accumulated

in 28 days, in mg kg-1 DW and in mg kg-1 OC.

Toxicity, as measured by the biomass of 12 worms after 28 days incubation, in g DW

cylinder-1.