Heavy metals and their bonding forms in sediments of the middle course of the River Elbe

摘要

The clay size fraction of sediments from four groyne fields along the middle course of the River Elbe was geochemically analysed. The main mineral phases, like quartz and feldspars, and clay minerals, were identified by X-ray diffractometry. The following clay minerals were detected: chlorite, kaolinite, and mixed-layers out of illite and montmorillonite. The total contents of main and trace elements were determined by ICP-OES and compared to geogenic background values. According to this comparison,Cd, Cu, and Zn are highly enriched in the clay size fraction, e.g. Zn by a factor of 10 to 20, while Cr and Ni range within the target values for a remediation of the Elbe. In order to be able to judge the mobility of some heavy metals, a six-step sequential extraction scheme after Jakob et al. (1990) was applied. The results show that a high proportion of oxidic mineralisations is present. Relatively high contents of more easily mobilisable bondings were also detected.