Environmental Quality Assessment for Valorization of Raw and Desalinated Dredged Marine Sediment Contaminated by Potentially Toxic Elements
Résumé
Within the framework of evaluating the long-term management of contaminated dredged sediments, we studied the mobility of inorganic contaminants contained marine sediment submitted to desalination and to leaching in an outdoor lysimeter. A set of complementary analytical techniques were used: mineral and textural analysis; simple selective extractions; sequential selective extractions; acid neutralization capacity tests and percolation dynamic leaching tests, using standardized procedures. The raw sediment presented a critical concentration of As, Hg and soluble salts compared to most European sediment quality guidelines (SQGs). Desalination allowed the leaching of soluble salts without significant leaching of most potentially toxic elements (PTEs), but greatly enhanced the mobility of Mo. Five months outdoor storage with natural cycles of wetting and drying increased the fraction bound to organic matter (OM) or sulfides of Cu, Pb, Cd, Mo, As and Pb. Cu and As mobility appeared highly related to OM dynamics. Na, Cl, B and Mo appeared highly mobile, but Mo release was lower at pH < 5. Zn, Pb, Mn, Al, Ni and Cr had behavior characteristic of species adsorbed on mineral oxides surfaces, being highly leachable at acid pH. Colloidal transport was significant for DOC, As, Ni and Co and was the main process for Pb. Drying the sediment greatly enhanced the mobility of a number of elements and compounds, particularly Cd, Pb, Mo, Ba, As. Mo mobility after drying turned the material unsuitable for technical embankment; the material may still be used in road engineering under impervious pavement.