Phytoremediation of dredged marine sediment: Monitoring of chemical and biochemical processes contributing to sediment reclamation

• Phytoremediation was applied to recover dredged marine sediments.
• A significant reduction in contaminants was obtained in planted sediments.
• The enzyme activity increase indicated the sediment functionality stimulation.
• Plant-root activity promoted the sediment transformation into a soil-like matrix.

In this study, a pilot phytoremediation experiment was performed to treat about 80 m3 of silty saline sediments contaminated by heavy metals and organic compounds. After preliminary mixing with a sandy soil and green compost application, three different plant treatments [Paspalum vaginatum (P); P. vaginatum + Spartium junceum (P + S); P. vaginatum + Tamarix gallica (P + T)] were compared to each other and to an unplanted control (C) in order to evaluate the plant efficiency in remediating and ameliorating agronomical and functional sediment properties. The experiment was monitored for one year after planting by taking sediment samples at two depths and performing several chemical and biochemical analyses. After one year, the increase in hydrolytic enzyme and dehydrogenase activities indicated the stimulation of sediment functionality. Additionally, the availability of energy sources derived from organic matter application and plant-root activity promoted the formation of a stable organic matter fraction. Finally, P + S and P + T were also effective in decontaminating polluted marine sediments from both organic (total petroleum hydrocarbons, TPH) and inorganic (heavy metal) pollutants.

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