Validating Pathway Analysis of Organic Contaminants from Aged Dredged Material Using Plants and Worms

ERDC TN-DOER-R3

September 2004

Validating Pathway Analysis of Organic

Contaminants from Aged Dredged Material

Using Plants and Worms

PURPOSE: Contaminants in dredged material (DM) placed in an upland situation, such as a

confined disposal facility (CDF), may move from substrates into food webs because of their

contact with CDF-colonizing or inhabiting plants and animals, and therefore may cause unac-

ceptable risks outside the CDF. The primary goal of this technical note is to provide guidance on

evaluating bioaccumulation of organic contaminants and toxicological effects in test species rep-

resenting two trophic levels of a food web.

BACKGROUND: Placement of DM in CDFs and its removal from CDFs for beneficial use

require assessment of environmental risk. To this end the decision-making framework and the

U.S. Army Corps of Engineers (USACE)/U.S. Environmental Protection Agency (USEPA)

Technical Framework may require exposure and effects assessments for plants and animals of

relevant contaminant pathways prior to dredging. Currently no specific guidelines for contami-

nant residues in plants and animals exist. The purpose of this study, sponsored by the Dredging

Operations and Environmental Research (DOER) Program, was to develop and validate methods

or further validate existing methods to assess the potential for unacceptable environmental risk

outside a CDF filled with contaminated DM, and to assess the suitability of aged materials for

beneficial use outside the CDF.

INTRODUCTION: USACE annually manages about 300 million cubic meters of DM. Histori-

cally about 50 percent is disposed of in open water, 40 percent is used for beneficial purposes

and the 5 to 10 percent of the material that is contaminated and unsuitable for open-water dis-

posal is placed into CDFs. USACE Districts require tools to help integrate topical quantitative

information to yield quantifiable estimates of risk posed by dredged materials including uncer-

tainty (Moore et al. 1998). The use of effects-based testing and risk assessment is intended to

supplement the analytical options currently available to DM managers by building on the exist-

ing technical framework (U.S. Environmental Protection Agency/U.S. Army Corps of Engineers

(USEPA/USACE) 1992) and the existing tiered approaches (USEPA/USACE 1991, 1998;

USACE 2003).

Test Organisms Used for Contaminants in Dredged Material: Several test organisms

have been used by USACE to evaluate bioaccumulation of metals from DM disposed in an

upland situation (Folsom et al. 1981, Van Driel et al. 1985, Folsom and Price 1989, Simmers

et al. 1989). Unfortunately, in several of these studies the toxic effects of metals were sometimes

noted but not quantified, nor were tests for toxic effects of organics performed. In a recent study,

Cynodon dactylon (bermudagrass) and Eisenia fetida (earthworm) were used as test organisms

for metals in DM from freshwater origin (Best et al. 2003). Bermudagrass was relatively sensi-

tive to zinc, which was the metal of concern in the test material, and could, therefore, only serve

for bioaccumulation and toxicity assessment at lower Zn levels, e.g. for beneficial use of DM.