Spatial Distribution Characteristics and Health Risk Assessment of Key Organic Pollutants in Chlor-alkali and Pesticide Industries: A Case Study

As the issue of soil organic pollution left behind by the relocation of traditional chemical enterprises has garnered increasing attention, this study took a decommissioned chlor-alkali-pesticide composite site in Hefei as an example. Soil samples were systematically collected through a grid-based sampling approach to analyze the spatial distribution and vertical migration characteristics of key pollutants such as benzene (Bz), trichloroethylene (TCE), formaldehyde (HCHO), and hexachlorocyclohexane (α-HCH). The results revealed that the distribution of pollutants closely corresponded to the historical production functional zones and exhibited three typical vertical patterns: "deep-layer migration-shallow-layer distribution-surface-layer enrichment." Health risk assessment based on the RAG-C model indicated that unacceptable carcinogenic risks would exist if the site were developed for Class I land use, with benzene being the primary carcinogenic contributor, while the non-carcinogenic risks of α-HCH were mainly attributed to oral ingestion and dermal contact pathways. Compared to comprehensive industrial parks, this site was predominantly contaminated by volatile solvents and pesticides, highlighting the shaping effect of industrial structure on the pollution profile. This study provides a scientific basis and practical reference for precise investigation, risk assessment, and zoning remediation of similar chemical legacy sites.