Effect of Sediment Organic Matter on Migration of Various Chemical Constituents During Disposal of Dredged Material

The disposal of both freshwater and saltwater sediments in open waters has been experimentally investigated in the laboratory. The emphasis of the experimental work was directed towards identifying the role that sediment organic carbon has in controlling various water-quality parameters at disposal sites. Long-term studies examined the possibility of transport of material from sediments into an overlying water column as well as monitoring the changes in the aqueous phase which initially contained large amounts of suspended matter. For the latter case, metal and nutrient concentrations were initially high but decreased significantly with time. Exceptions to this behavior were noted. Specific components were identified which migrated from the sediment into the water column. They include ammonium-nitrogen, orthophosphate, cadmium, and manganese, the latter only in seawater media. Organic carbon and inorganic nitrogen underwent transformations with the systems investigated. Both sediment organic carbon and soluble organic matter were generally found to have no demonstrable effect on water quality. Exceptions to this general conclusion were found in two sediments containing significant amounts of petroleum hydrocarbons.