The potential of remobilization of pollutants is a major problem for anthropogenic ecosystems, because even when the anthropogenic source of pollution is identified and removed, pollutants stored in sediments can be released into the water column and impact pelagic communities during sediment resuspension provoked by dredging, storms or bottom trawling. The objectives of the present study were to assess the changes observed in the chemical composition of the water column following resuspension of a polluted marine sediment and the consequences for the chemical composition of adjacent marine waters according to season. For that purpose, an experimental sediment resuspension protocol was performed on four distinct occasions, spring, summer, fall and winter, and the changes in nutrients, organic contaminants and inorganic contaminants were measured after mixing sediment elutriate with lagoon waters and offshore waters sampled nearby. Significant seasonal variations in the chemical composition of the contaminated sediments were observed, with a strong accumulation of PAHs in fall, whereas minimum PAH concentrations were observed during winter. In all seasons, sediment resuspension provoked a significant enrichment in nutrients, dissolved organic carbon, and trace metal elements like Ni, Cu, and Zn in offshore waters and lagoon waters, with enrichment factors that were season and site dependent. The most pronounced changes were observed for offshore waters, especially in spring and winter, whereas the chemical composition of lagoon waters was weakly impacted by the compounds supplied by sediment resuspension.

Boron removal was evaluated in the present work by using calcium alginate beads (CA) and a novel composite based on alginate–alumina (CAAl) as sorbents in a batch system. The effects of different parameters such as pH, temperature, contact time, and composition of alginate (at different concentrations of guluronic and mannuronic acids) on boron sorption were investigated. The results confirm that calcium alginate beads (CA) exhibited a better adsorption capacity in a slightly basic medium, and the composite alginate–alumina (CAAl) exhibited improved boron removal at neutral pH. Sorption isotherm studies were performed and the Langmuir isotherm model was found to fit the experimental data. The maximum sorption capacities were 4.5 mmol g−1 and 5.2 mmol g−1, using CA and CAAl, respectively. Thermodynamic parameters such as change in free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were also determined. The pseudo-first-order and pseudo-second-order rate equations (PFORE and PSORE, respectively) were tested to fit the kinetic data; the experimental results can be better described with PSORE. The regeneration of the loaded sorbents was demonstrated by using dilute HCl solution (distilled water at pH 3) as eluent for metal recovery.

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