Using indicator kriging for evaluating heavy metal contents of a soil over serpentines

摘要

Geostatistical interpolation, kriging, is increasingly used to estimate spatial variability of soil properties and attributes. The kriging-based approach, indicator kriging (IK), may be used to model the uncertainty of mapping heavy metals. Soil samples were obtained at 53 points from the top layer of a soil developed over serpentine. Total and EDTA- extractable contents of Fe, Mn, Cr, Ni, Cu, Zn and Co were determined. The soil data were coded as 0 or 1 when higher or lower than the threshold value established as the median. Using the coded data, indicator semivariograms were computed and modelled by a nugget component plus a structure. Counter maps of probability of meeting the critical threshold value for each of the individual heavy metals were drawn by IK. Advantages of IK for assessing local uncertainty when compared with ordinary kriging were shown.