Mapping heavy metals in polluted soil by disjunctive kriging.

The soil of some 50 km(2) around the town of Weinfelden in north-east Switzerland has been sampled and analysed to estimate and map the concentrations of heavy metals before an incinerator for the canton's waste is built. Given that the estimates are subject to error, the probabilities that true values exceed the maximum tolerable concentrations of the Swiss federal guide have also been estimated by disjunctive kriging. These may now be used by the local planners for making decisions. Of the metals examined, lead exceeded the guide value at several sampling points, and a moderate probability of excess of lead is fairly widespread. Copper exceeded the guide value in vineyards and orchards, but also in a few places elsewhere, and the estimated probabilities of excess were not negligible. The other two metals of concern, cadmium (with one exception) and zinc, had concentrations much less than the guide values. The patterns of distribution of the four metals were similar, the product-moment correlations among them are substantial, except in the vineyards and orchards, and it seems likely that they had common sources.