Batch leaching testing of stabilized dredged bottom-sea sediments

Abstract

This study aims to define the long-term leaching of metals from structural fills composed of quarry byproduct-amended marine-dredged material under the influence of pH and to study the geochemical behavior of the species likely to form. Compaction and shear tests, image analysis, and pHstat and toxicity characteristic leaching procedure tests were undertaken to study the metal leaching behavior of raw dredged sediments and their blends prepared with three different quarry fines. Geochemical analysis was conducted to determine the predominant oxidation states from the analyzed metals, the aqueous concentrations of metal species, and the dominant leaching control mechanisms in the leachates. The quarry fine-amended dredged sediments satisfied the local compaction specifications for highway embankment construction while the raw sediments did not. The effective friction angle of the blends was also higher than that of raw sediments due to differences in soil structure and shape parameters. Leaching of As during the pHstat leaching tests followed an amphoteric pattern for raw sediments and a cationic pattern for the blends. Al, Cu, Fe, Ni, and Zn concentrations leached from the blends were below the EPA water quality limits at near-neutral pH. The concentrations of all metals released during the batch leach tests from the treated dredged materials are below the water quality limits under varying pH conditions. Geochemical modeling results indicated that release of all elements except arsenic from the treated dredged sediments was controlled by the dissolution and precipitation of oxide, hydroxide, and carbonate solids containing the elements.