Characteristics and contamination evaluation on cultivated soil heavy metals in consolidation project areas in Guizhou province—A case study on Yanjiao town in Liuzhi District

In order to find out the heavy metals contamination characteristics of cultivated soil in Yanjiao town consolidation project area of Liuzhi Special District in Guizhou province，the concentrations of heavy metals such as Cr，Cu，Zn，Cd，Pb，Hg，As etc. of cultivated soil in nine typical land remediation project areas were analyzed. Single factor contamination index method，Nemerow contamination index，contamination load index method and potential ecological risk index method were used to assess soil heavy metal pollution，State environmental standards and soil heavy metal background values of Guizhou province were used to obtain the soil environmental quality database in project areas. Assessment on the heavy metal contamination and ecological risk of cultivated soils in the project area，comprehensive evaluation results showed that，evaluating based on the secondary limit values of national standards，the comprehensive contamination index was 0.923 and was below alertness line level. There was already a high level of environmental contamination，dry land was higher than paddy fields. Two kinds of evaluation results showed that single factor index of Cd，Cr and Cu were above 1，these three elements were the major contributors to pollution in project areas. Ecological evaluation results showed that the cultivated soil of the areas was at slight ecological risk level，Cd and Hg were the main risk factos. Therefore，the high standard basic farmland and contamination-free production bases should be reasonable layout.