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Overview of Contaminated Sediments ProblemThe ecological and health effects associated with contaminated sediments are a national and international concern. An estimated 1/8 to 1/4 of all United States national priority list sites have contaminated sediments as one component of the site. In the past, industrial and municipal wastewaters were discharged with into rivers and streams without adequate treatment. Pollutants in the wastewater, including heavy metals and hydrophobic organic chemicals, tended to partition to particulate matter and ultimately settle to the bottom sediments. As the quality of the wastewater discharges have continued to improve, however, the sediments which were once the repository for hydrophobic chemicals have become sources of chemical contamination to both the benthic and pelagic ecosystems. In addition, bioaccumulation through the food chain and atmospheric release (especially during dredging and confined disposal facility storage) of sediment-associated pollutants may pose a human health threat. Removal and upland treatment of contaminated sediments is often difficult due to the high water content, large volumes, and fine particles that tend to contain the bulk of the contaminants. These factors conspire to make treatments developed for contaminated soils uneconomical or impractical for treatment of sediments. Cost effective means of mitigating the environmental and ecosystem impacts of contaminated sediments are needed. In situations where natural sedimentation and degradation processes are reasonably rapid, intrinsic remediation may be an acceptable alternative. However, many locations exist in which this lowest cost option carries too high of a risk in terms of the potentially harmful effects to the ecosystem/human health.
Produced by the Hazardous Substance Research Centers/South & Southwest
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