Spatial characteristics of soil heavy metal pollution in polluted sites: taking a relocated electroplating factory as an example

Taking a relocated electroplating plant as an example and based on the sampling data in the survey report of the polluted site, the categories of polluting heavy metals were screened according to the Soil Environmental Quality-Risk Control Standard for Soil Contamination of Agricultural Land (Trial) (GB 15618-2018). The inverse distance weighting (IDW) method was used to analyze the distribution characteristics of heavy metals in the study area, Moran index was used for spatial correlation analysis, and the semivariogram was used to analyze the overall spatial structure and trend of heavy metal pollution, so as to explore the spatial characteristics of heavy metal pollution in the polluted site. The results showed that the concentrations of Ni, Cr, Zn and Cu in the soil in the study area exceeded the soil background value, and the risk screening value multiples of the sampling points with the highest concentration were 9.55, 1.35, 5.94 and 10.67, respectively. The concentrations of Cu and Zn showed an inverted U-shaped trend in the east-west and north-south directions within the site, high in the middle and low around. The spatial distribution characteristics of Ni and Cr concentrations are similar, and the high value area is located at the northeast boundary of the site. The spatial characteristics of the four over-standard heavy metals were quite different, but they all showed aggregation characteristics.