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Traditional disposal alternatives of dredged material are subaqueous (open-water) disposal, application to intertidal sites and upland deposition. More recently, coastal marine disposal in capped mound deposits above the prevailing seafloor, disposal in subaqueous depressions and capping deposits in depressions have been proposed for contaminated sediments (.) These categories differ primarily in the biological population exposed to the contaminated sediments, physico-chemical conditions and transport processes potentially capable of removing contaminants from dredged material at the disposal site. (.) The ecological effects of heavy metals in contaminated sediments are determined more by the chemical form and reactivity than by the level of accumulation. Land deposition of dredged mud is mainly concerned with the following factors: 1. Change of pH; 2. Change of redox conditions; 3. Formation of soluble, complexing organic compounds; 4. Microbial interactions. These factors affect the chemical forms and bonding strength of heavy metals in sediment particles and thus mobility and availability. For the deposition of freshwater sediments in intertidal and coastal marine environments, the effect of salinity is of great importance. Remobilization of certain metals, e.g. Cd. is due to increased ion concentrations and formation of soluble chloro-complexes (.). In order to minimize potential adverse effects upun disposal of dredged material, chemical and mechanical stabilization techniques, especially for upland disposal alternatives, are proposed and discussed in the following sections.
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