| Summary: | Metals and organic contaminants are common in many marine and fresh water environments as a result of industrial and military activities. Traditional remediation/risk management options for sediments contaminated with these materials include no action, monitored natural recovery, institutional controls (land use restrictions, etc.), in situ treatment and management, and ex situ treatment and management. Active capping is a newer approach for treating contaminated sediments that involves applying chemically reactive amendments to the sediment surface. The mobile, soluble forms of contaminants are generally considered toxic. Induced chemical precipitation of these metals can shift toxic metals from the aqueous phase to a solid, precipitated phase which is often less bioavailable. This can be achieved through the application of sequestering agents such as rock phosphates, organoclays, zeolites, clay minerals, and biopolymers (e.g., chitosan) in active caps. Active caps can stabilize contaminants in contaminated sediments, lower the bioavailable pool of contaminants, and reduce the release of contaminants to the water column thereby providing an economical and effective alternative to traditional treatments.
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