Is phytoextraction a suitable green treatment for metal contaminated sediments

The cleaning of waterways by regular dredging generates great volumes of sediments and, owing to human activities, these sediments often contain large amounts of metals. For some of these contaminated sediments, a treatment by phytoextraction could be considered. To our knowledge, phytoextraction with hyperaccumulating plants has been rarely tested on heavily contaminated sediments. This work consisted in a preliminary study of Cd phytoextraction potentialities and focused on the fate of Cd present in a metal-polluted dredged sediment during the culture of Arabidopsis halleri, a Zn and Cd hyperaccumulating plant. In this purpose, a five month pot experiment was achieved; results obtained for the first four months of monitoring are presented here. Cd contents in the sediment, in the aerial parts of plant and in the leachates were measured each month. Cd speciation in the sediment was studied by EXAFS and µXANES spectroscopy, Cd localization by SEM-EDX and µXRF. Before culture, Cd was present as mixed Zn, Cd and Fe sulphide in the sediment. Version traduite : La phytoextraction est-elle un traitement "vert" approprie pour les sediments contamines en metaux ? La maintenance des voies navigables par dragages reguliers genere de grands volumes de sediment et, suite aux activites humaines, ces sediments contiennent souvent de grandes quantites de metaux. Pour certains de ces sediments contamines, un traitement par phytoextraction pourrait etre envisage. A notre connaissance, la phytoextraction utilisant des plantes hyperaccumulatrices a rarement ete testee sur des sediments contamines en metaux. Ce travail est une etude preliminaire sur le potentiel de la phytoextraction du cadmium (Cd). Il porte sur le devenir du Cd present dans un sediment de curage contamine par des metaux lors de la culture d’Arabidopsis halleri, plante hyperaccumulatrice de Zn et de Cd. Dans ce but, une experience de culture en pot de cinq mois est realisee ; les resultats obtenus pendant les quatre premiers mois du suivi de culture sont presentes ici. Les teneurs en Cd contenues dans le sediment, dans les parties aeriennes de la plante et dans les lixiviats sont mesurees chaque mois. La speciation du Cd present dans le sediment est etudiee par spectroscopie EXAFS et µXANES et la localisation par MEB-EDX et µXRF. Mots-cles: Arabidopsis halleri; Cadmium (Cd); Hyperaccumulation; Phytoextraction; Sediment; Speciation.