Abstract:

The manufacture process of metal products involves the massive use of metal materials, which may lead to soil contamination by heavy metals. Understanding the spatial distribution properties, sources, and ecological risk of heavy metals in soils from brownfield sites of metal manufacturers is of great practical significance. In this study, a typical brownfield site of metal manufacture in southern China was investigated. A total of 517 soil samples were collected at the depths of 0-9 meters, and the contents of As, Cd, Cr, Hg, Ni, Pb, Sn, Zn were determined. Spatial distributions of heavy metals in each soil layer were analyzed with ArcGIS, while correlation and variability analyses were applied to explore their spatial distribution characteristics and sources. Finally, the ecological risk was assessed using the potential risk index method. The results showed the accumulation of elements including As, Cd, Cr, Ni, and Zn in the surface soil (0-50 cm), with Cd (13.27) displaying the highest enrichment coefficient, followed by Zn (1.45), As (1.22), Ni (1.17), and Cr (1.15). The spatial distribution of these metals exhibited a “hot spot” pattern, mainly concentrated in the carpentry and vanish-stoving workshops. The aggregation patterns of different elements were closely related to the manufacturing processes of metal products. Furthermore, the correlation analysis revealed a negative relationship between the contents of heavy metals and sampling depth. The vertical migration behaviors varied depending on soil properties, including texture and organic matter content, with Ni showing the highest migration ability, followed by Cr, Sn, Pb, and Zn. The correlation and other analyses indicated that the main source of soil heavy metals were wastewater and exhaust gas emissions during manufacturing, which subsequently percolated through the surface soil. The potential ecological risk assessment showed an “extremely high” level of ecological hazards, which was mainly at the depth of 0-2 m, with Cd as the most important ecological hazard contributing factor. Overall, this study offers crucial scientific and technological support for characterizing pollution in metal product manufacturing enterprises and remediating sites contaminated with heavy metals.

Key words: metal products, brownfield site, heavy metal, spatial distribution, ecological risk

摘要：

金属制品制造因涉及大量金属材料加工和使用，可能导致土壤重金属污染。揭示该行业场地土壤重金属的空间分布特征、成因和生态风险具有重要的现实意义。以华南典型金属制品制造遗留场地为对象，采集0－9 m土壤样品共517个，检测As、Cd、Cr、Hg、Ni、Pb、Sn、Zn等8种重金属元素，利用ArcGIS分析土壤各层重金属分布，通过相关性和变异性分析揭示空间分布特征与来源，并采用潜在生态风险指数法评估其生态风险。结果表明，表层（0－50 cm）土壤As、Cd、Cr、Ni和Zn等元素出现不同程度的累积，富集系数排序为Cd (13.27)>Zn (1.45)>As (1.22)>Ni (1.17)>Cr (1.15)。在水平分布上，As、Cd、Cr、Ni和Zn等元素呈现“斑块状聚集”现象，主要集中在木工和烤漆车间等区域，不同元素聚集特征与金属制品生产工艺密切相关。在垂向分布上，相关性分析表明各重金属质量分数与采样深度存在一定的负相关关系；受土壤质地、有机质含量等理化性质的共同影响，不同重金属的垂向迁移行为有所差异，垂向迁移能力排序为Ni>Cr>Sn>Pb>Zn。相关性分析结果等揭示土壤重金属可能来源于生产过程中产生的废水和废气，通过地面渗滤进入表层土壤。潜在生态风险评价表明，该场地的生态风险属于“极强”水平，主要集中在0－2 m深度范围内，且Cd是最主要的生态危害贡献因子。该研究可为金属制品生产企业场地土壤污染刻画与治理修复提供支撑。

关键词: 金属制品, 遗留场地, 重金属, 空间分布, 生态风险