Assessing the bioavailability of HOCs during habitat restoration

Photo by Chris J. Benson


Nathan Johnson, University of Minnesota‐Duluth
Amanda Brennan, University of Minnesota‐Duluth

Project Summary

Re‐use of navigational dredged materials for the purpose of habitat creation could potentially benefit current and future restoration activities at moderately contaminated areas of the St. Louis River Estuary as well as reduce costs associated with management of dredged materials.

This project will evaluate the bioavailability of sediment‐associated legacy contaminants before and after restoration efforts involving dredged materials from the Duluth‐Superior Harbor.

The state of Minnesota’s current practices for assessing sediment contamination involve primarily bulk sediment analysis, which quantifies all sediment contaminants, including those that are strongly sequestered and not available for uptake by organisms. This bulk sediment analysis cannot address important questions such as which contaminants benthic organisms are exposed to and how complex sediment characteristics affect the uptake of these contaminants into organisms.

Bioavailability based techniques utilized in this research will employ passive sampling to quantify the concentrations of contaminants freely dissolved in sediment porewater, thereby providing a realistic measure of organism exposure. The Minnesota Pollution Control Agency and US Army Corps of Engineers are working together to evaluate the contaminant‐related implications of utilizing dredged material for habitat restoration and their feedback will be solicited and incorporated at various stages of the project.

Locally, the results of this project will provide resource managers with a greater understanding of the contaminant‐related implications of using dredged sediments from the Duluth‐Superior Harbor for restoration activities. On a broader scale, this project will serve as a template for the integration of data from bioavailability based techniques in assessments of site restoration in Minnesota and the Great Lakes.