Knowledge
of the spatial distribution of heavy metals is indispensable
for successful risk analysis of contaminated sites. The common practice
is to obtain soil samples for spatial interpolation through site investigation,
which generally involves preliminary and detailed surveys. In this
study, we propose an information entropy-based site investigation
(IESI) method in which an optimal design step is implemented to guide
soil sampling at the detailed survey stage. Two types of information
entropy (i.e., relative entropy and Shannon entropy) are used to design
the optimal sampling strategy. The results show that, within the IESI
method, relative entropy is superior to Shannon entropy in guiding
soil sampling. Combined with ordinary kriging, the IESI method outperforms
conventional surveys for hypothetical and actual heavy metal-contaminated
sites as it can identify new polluted and clean areas. For quantitative
comparisons, the IESI method coupled with ordinary kriging, logarithmic
ordinary kriging, and universal kriging with linear and quadratic
trends can improve the interpolation accuracy by 16–43% at
the actual heavy metal-contaminated site. Upon further examination
of the IESI method, informative sampling points are mainly distributed
around the polluted areas identified by the preliminary survey with
soil pollution probabilities between 0.75 and 0.95. This work provides
an effective tool for delineating the spatial distribution and valuable
insights into identifying encryption areas at heavy-metal sites.