Abstract: The degree of soil heavy metal pollution has uncertainty and its evaluation model is required to reflect this nature. Based on the matter element theory, extension set and dependency function in the extension theory, a model for the dependency and matter elements of soil heavy metal pollution evaluation was established and used in the evaluation of six groups of heavy metal polluted soils. The research shows that extension evaluation decides the degree to which set the pollution belongs to based on their extensible dependency, solving the uncertainty in the degree classification of soil heavy metal pollution. Simple dependency function is used to determine the weight of each influencing factor, which can avoid the subjectivity as it is capable of digging relative information from data characteristics. Therefore, the evaluation method based on the extension theory is an efficient new method for soil heavy metal pollution.

Key words: Soil, Evaluation of heavy metal pollution, Extensible dependence, Dependence function