Three-Dimensional Characterization and Management of Heavy Metal Contamination in Site Soils

As former chemical sites, especially retired pesticide plants, the redevelopment of “brownfield” land imposes urgent demands for detailed environmental investigation and remediation. Addressing the current limitations in pollution characterization, which often remain confined to two-dimensional representations and lack research on the vertical migration mechanisms of heavy metals and their integration with three-dimensional remediation and management strategies, this study focuses on a typical retired pesticide plant site in Southeastern Zhejiang, China. Through systematic analysis of 916 soil borehole samples collected from 92 sampling points, the study integrates three-dimensional visualization technology and three-dimensional ordinary kriging interpolation to establish a high-precision three-dimensional characterization system covering stratigraphy, pollution plumes, and composite risks. The findings reveal that the As and Ni pollution plumes have volumes of 5.35 × 104 m3 and 2.78 × 105 m3, respectively. Furthermore, As and Ni exhibit significant vertical migration capabilities within sandy and silty soil layers, while elements such as Hg, Cd, and Pb are primarily concentrated in the surface fill layer. By combining three-dimensional risk modeling based on the single-factor pollution index, Nemerow comprehensive index, and potential ecological risk index, the study precisely classifies the site into four graded zones: safe use zone, basically safe use zone, low-risk control zone, and high-risk control zone. This approach enables the visualization and quantification of pollution levels. The research constructs a comprehensive methodological framework that extends from three-dimensional pollution characterization to zonal management decision-making, providing scientific evidence and technical support for the precise remediation and sustainable redevelopment of similar retired industrial sites.