Research Programs: Contaminated Sediments
Research Areas: Resuspension

Contaminated Sediments

Do resuspended sediments and post-dredging residuals at contaminated sediment sites alter the release and bioavailability of contaminants?

Background

Dredging at the Harbor Island Superfund Site in Seattle, Washington.

If the risks associated with a contaminated sediment site are determined to be sufficiently great, dredging will frequently be used to remove the contaminated sediments and reduce the risks. While dredging removes most of the material causing the identified risk, it is the most expensive remedy and it has the greatest potential to impart short-term adverse impacts on the site and on the surrounding uncontaminated areas. These potential impacts are presumed to result from the resuspension of contaminated sediments during dredging, which can in turn lead to the transport of contaminated particles from the site, and from the flux of dissolved and bioavailable contaminants into the water column.

Problem

Does dredging cause a significant change in contaminant bioavailability? If so,

How effectively do current models of contaminant fate and transport predict the release of dissolved and bioavailable contaminants during resuspension?
What is the magnitude of release of dissolved and bioavailable contaminants during dredging from the dredging zone into the less contaminated areas?
What are the effects of resuspension and resettlement on the bioavailability of sediment contaminants?

Approach

The research evaluates modeling and empirical approaches for predicting and measuring the risk of increased bioavailability/bioaccumulation of contaminants caused by dredging. The research includes evaluating the bioavailability of resettled contaminated sediments that constitute one form of post-dredging residuals. Research activities will include the following:

Compare existing resuspension model predictions to field measurements;
Develop an approach/method for measuring dissolved organic and inorganic contaminants under field conditions (i.e., in the water column during dredging); and
Assess changes in bioavailability resulting from resuspension and resettlement of contaminated sediments (including collaborations with NRMRL post-dredging residuals research effort).