An innovative coupling between column leaching and oxygen consumption tests to assess behavior of contaminated marine dredged sediments
Résumé
Purpose: Contaminated dredged sediments are often considered hazardous wastes, so they have to be adequately managed to avoid leaching of pollutants. The mobility of inorganic contaminants is a major concern. Metal sulfides (mainly framboïdal pyrite, copper and zinc-sulfides) have been investigated in this study as an important reactive metal-bearing phase sensitive to atmospheric oxygen action.
Methods: An Oxygen Consumption-Test (OC-Test) has been adapted to assess the reactivity of dredged sediments when exposed to atmospheric oxygen. An experimental column setup has been developed allowing the coupling between leaching and oxygen consumption test to investigate the reactivity of the sediment.
Results: This reactivity, which consisted of sulfides oxidation, was found to occur for saturation degree between 60 and 90% and until the 20th testing week, through significant sulfates releases. These latter were assumed to come from sulfides oxidation in the first step of the test, then probably from gypsum dissolution. Confrontation results of OC-Test and leachates quality shows that Cu was well correlated to sulfates releases, which in turn leads to Ca and Mg dissolution (buffer-effect). Cu, and mostly Zn, was associated to organic matter, phyllosilicates and other minerals through organo-clays complexes.
Conclusions: This research confirmed that OC-Test originally developed for mine tailings could be a useful tool in the dredged sediment field which can allow for intrinsic characterization of reactivity of a material suspected to readily reacting with oxygen and for better understanding of geochemical processes that affect pollutants behavior, conversion, and transfer in the environment.
Origine : Fichiers produits par l'(les) auteur(s)
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