Characterization of landfill deposited sediment from dredging process during different maturation stages

Abstract

A long-term monitoring of deposited sediment in the environment is considered in order to examine the mechanism of incorporation of Cu and Cd into mineral fractions and to investigate their bioavailability during landfill maturation. Using the sequential extraction technique (Community Bureau of Reference, BCR), the dominant presence of Cu and Cd in the oxidation and residual fraction was determined, which suggests a low risk of bioavailability of these metals in the environment. The maturation of the deposited sediment indicates that the Cu and Cd content decreases over time in the exchangeable fraction and increases in the oxidation fraction. X-ray techniques XRF and EDS indicated a prevalence of silicates in the tested samples, which suggests the possibility of presence of silicate compounds that can bind metals and thus convert them into less mobile forms in the sediment. By imaging the samples with a scanning electron microscope SEM, the formation of heterogeneous structures over time was determined, which confirms the formation of new minerals and the potential possibility of incorporating copper and cadmium in them. In order to determine the mineral forms and dominant compounds in the examined sediment samples, X-ray diffraction analysis was applied, and the transformation pathways were explained.