南京城市土壤的特性与重金属污染的研究

The basic properties and heavy metal pollution of urban soils in Nanjing

研究了南京市城市土壤母质组成、剖面结构、pH值、土壤质地、土壤有机质、重金属元素全量及其不同形态含量等理化性质和分布规律。结果表明,城市土壤母质来源复杂,剖面层次混乱,土壤反应石灰性、粗粒化、有机质含量升高和表聚现象较明显。城市土壤重金属污染较为严重,不同功能区的污染元素和污染程度有显著差异。综合污染程度以老工业区含量最高,依次为老居民区、商业区、风景区、城市广场、开发区。但各功能区土壤重金属的形态分异不明显。城市土壤的随机空间变异十分突出,无论是土壤性质还是重金属污染积累都如此。城市中可能存在一些高度污染的岛状区域,这在城市环境质量上必须予以密切关注。

Samples were collected by selecting different functional zones from Nanjing city. Analysis of physico-chemical properties including soil-forming parent material constituent, structure of profile, pH, soil texture, soil organic matter, the total and extractable heavy metals of the soils were conducted. The results indicated that the source of the parent material of the urban soils is complicated and the profiles were disordered. Compared with soils from conservation zone, the urban soils showed an trend of increasing soil pH, coarse particle contents, soil organic matter. The pollution by heavy metals in the urban soils was dramatic with the industrial zone being the worst. The overall pollution degree, as indicated by the pollution index calculated from the different heavy metal accumulation, is higher for the industrial zone and old residential zone plus the concentrated commercial zones. However, the extractable content of heavy metals seemed no significant variation among the functional zones. Both the soil properties and the content of heavy metals exhibited a very remarkable spatial variability. Some “islands” with extremely polluted soil with heavy metals might exist in some locations with emission impacts. This should be taken into account of the environmental concerns for the urban society.