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Contaminated Aquatic Sediments

Sediment contamination problems are particularly vexing owing to the tendency for contaminants to be retained within sediments for a long time. Due to the strong binding of some organic and inorganic contaminants to the sediment material, sediments serve as a long-term source of the contaminant to the water body and the biota, even long after the original source of the contaminant has been removed. According to an estimate by the U.S. Environmental Protection Agency (EPA), approximately 10 percent of the sediment underlying the country’s surface water is sufficiently contaminated with toxic pollutants to pose potential risks to fish and to humans and wildlife who eat fish (EPA, 1998). This represents the upper five centimeters of sediment where many bottom dwelling organisms live, and where the primary exchange processes between the sediment and overlying surface water occur. Acute, laboratory toxicity tests performed by the National Oceanic and Atmospheric Administration (NOAA) on 1543 surficial sediment samples collected during 1991 through 1997 in 25 estuaries and marine bays representing a total area of approximately 7300 km indicated toxicity in approximately 6% of the combined area (Long, 2000). Sediment contamination problem is exacerbated by the need to periodically dredge the old deposited sediments to maintain navigable depths in waterways. Nearly three hundred million cubic yards of sediment are dredged from United States ports, harbors, and waterways each year to maintain the nation's navigation system. It is estimated that approximately 5-10% of these dredged materials are impacted with organic and inorganic contaminants. This literature review covers published works in the years of 2000 and 2001 and is divided into the following three major sections: 1) Sediment characterization; 2) Links between sediment chemistry and contaminant bioavailability and toxicity; and 3) Sediment remediation.