Using indicator kriging to delineate and map the spatial patterns of zinc soil pollution

Mapping heavy metal pollution in soil is essential for environmental monitoring. Kriging is often used to characterize the spatial variability of heavy metal. However, due to its smooth effects, it is incapable of detecting the uncertainty of estimates. In this study, the indicator kriging was used to map the uncertainty of the estimate, and to provide the probability of pollution risk. Eight hundred and thirty nine samples were analyzed, according to the accumulating pollution index and the background value. Three thresholds which classified Zn pollution risk into safe, low, moderate and high levels were adopted. The result showed that there is high Zn content in the soil of the study area. Its mean reached 86.7 mg/kg, larger than the background value (80.3 mg/kg), which mainly resulted from the nearby Zn mine. The probability map indicated that the pollution risk were chiefly low and moderate levels, and the closer the distance to Zn mine, the greater the probability values.