Prediction of heavy metal contents and displacement in soils

Under laboratory conditions, the availability of cadmium, lead and copper in an Orthic Luvisol was investigated when applied to the soil at various initial concentrations. The metals were applied separately or concurrently with the other two heavy metal ions in order to bring about competition for the adsorption sites. The presence of competing metals increased the general availability especially of cadmium in the soil. Lead and copper were to a lesser extent also affected by the competition of other ions. On the basis of our ion‐competition results we developed a longterm trend model suitable to predict the consequences of regular heavy metal loading (e.g. in the form of sewage sludge). The model takes into consideration the annual precipitation and the water suction profile of the soil. On the basis of the model predictions it has to be concluded that the threshold values for heavy metals in the sewage sludge regulation (Switzerland) are too high.