Cd and Zn concentrations in small mammals and willow leaves on disposal facilities for dredged material

Disposal sites for dredged material are often polluted with heavy metals. The uptake of Cd and Zn by small mammals and willow trees was assessed on three sites with a different pollution degree. Detailed soil sampling showed a huge variation in soil characteristics within the sites, typical for disposal sites for dredged material. This variation made risk assessment and interpretation of soil chemical analyses complicated. Small mammals were thought to give a more integral description of the contaminant level because they cover a large area. Cd concentrations in small mammals were elevated compared with background levels whereas Zn concentrations were rather low. There were no significant differences between sites in Cd or Zn levels in animals. Leaf analysis showed a clear response to the pollution degree of the sites. The calculations using the BIOMAG model indicated that the Cd of the soil caused low risk for predators. However, the elevated Cd and Zn concentrations in the willow leaves on the polluted sites and the high Cd concentrations in the small mammals on all sites indicated that ecosystem development should be carefully considered.