Contaminants in sediments: remobilisation and demobilisation

In this study, the contaminated anoxic sediment of the Mulde reservoir (Sax ony, Germany) was investigated. Several sediment cores were analysed for he avy metals and organic chemicals such as chlorobenzenes and DDTs. The compa rison between anoxic and oxidised sediment cores showed the potential dange r for heavy metal (Zn and Cd) remobilisation from sediment due to bioturbat ion or resuspension by: flooding. Chemical sequential extraction was used t o describe partitioning of heavy metals among different mineralogical compo nents in the sediments. Results showed remobilisation of Zn and Cd from the sediments. The stable fraction (organic/sulfidic-bound) of Zn and Cd decre ased from 10 to 3%, and from 35 to 5%, respectively, Simultaneously, the ca rbonate fraction increased from 3 to 12% for Cd and from 10 to 22% for Zn. Furthermore, the simulation of the diffusion of organic pollutants showed r emobilisation of 1,4-dichlorobenzene. The results confirmed the;necessity o f sediment remediation in the reservoir. Capping seems to be a promising ap proach for a low-cost remediation. (C) 2001 Elsevier Science B.V. All right s reserved.