Persistent organic contaminants like polychlorinated biphenyls (PCBs) are widespread in sediments and pose risks to humans and wildlife and the nation's economy through deterioration of water quality. The magnitude of the sediment contamination problem in the US is evidenced by more than 2,100 state advisories issued against consuming fish. Maryland for example has a large number of fish consumption advisories in effect in the major rivers such as the Potomac, Patuxent, Susquehanna, and Pataspco. A majority of these advisories are due to unacceptable levels of PCBs and pesticides. The problem is aggravated by the fact that contaminated sediments are very widespread in extent and traditional cleanup technologies such as dredging and disposal are too expensive and too disruptive of existing ecosystems. Cleanup is also hindered by poor knowledge of how sediment characteristics influence impacts.

This research seeks to close the knowledge gap between sediment chemistry and contaminant bioavailability, and apply new insights to innovative and practical strategies for management of contaminated sediments. We have applied microscale measurement techniques to examine the location and association of organic contaminants in sediments at the sub-particle scale. We are finding that in the presence of natural carbonaceous particles such as coal, coke, and charcoal in sediments, hydrophobic contaminants accumulate in these types of particles making the bound contaminants relatively unavailable to benthic organisms. We have also demonstrated that the addition of a strong sorbent like granular activated carbon to sediments may be a cost-effective, in situ management strategy by sorbing organic contaminants and thereby reducing bioavailability and bioaccumulation. Such a management strategy is especially attractive for large areas of low level PCB concentrations. This management strategy requires mechanistic understanding of linked chemical and biological processes and using such information in conceptual and quantitative models to understand the long-term efficacy of the in situ stabilization process. This seminar will present an overview of the laboratory research leading to a current field trial of the technology.