北京市农田土壤重金属的化学形态及其对生态系统的潜在危害

Chemical Forms of Heavy Metals in Soils and Potential Hazards to Ecosystem in Beijing Farmlands

选取北京市农田96件土壤样品,采用分级提取试验方法研究土壤中重金属元素Cd、Hg、Pb、As的化学形态。结果表明,Cd、Hg、Pb、As的含量远低于国家土壤环境质量二级标准(GB15618-1995);As、Hg、Pb主要以残渣态形式存在,Cd主要以离子交换态存在;As、Pb各形态的变异系数差异相对较小,Hg、Cd各形态的变异系数差异较大;元素总量和土壤有机质含量是影响元素地球化学形态的主要因素;Cd的迁移能力较强,容易被植物吸收,对土壤生态系统的潜在危害性较大。

In this paper, 96 soil samples in Beijing farmlands were studied for chemical forms of heavy metals of Cd, Hg, Pb and As by sequential extraction method. The results showed that total concentrations of Cd, Hg, Pb, and As were much lower than the corresponding limits of national standards. As, Hg and Pb were dominated by residual forms, while Cd in exchangeable forms. The variation coefficients of chemical forms of As and Pb were comparatively smaller, whereas, the variation coefficients of each chemical forms of rig and Cd were comparatively larger. The total concentrations of heavy metals and soil organic matter content were the main factors that affect chemical forms of heavy metals. Cd was comparatively mobile and readily absorbed by plants. The potential hazard of Cd to farmland ecosystem was serious.