城市表层土壤由于接纳了多种污染源(如工业污染源、交通污染源、燃煤污染源等)释放的重金属,可以作为城市环境中重金属污染的“示踪物”。城市表层土壤中的重金属不仅可以通过大风扬尘等方式危害人类(特别是儿童)健康,而且能够污染地表水或地下水等水生生态系统。因此,对城市表层土壤重金属需要进行可持续管理和发展。首先探讨了城市表层土壤重金属的环境承载力的内涵和特征,分析了土壤对重金属承载机制和约束条件,区分了“绝对承载力”和“相对承载力”,并且给出了城市表层土壤重金属环境相对承载力的计算模型;其次,探讨了城市表层土壤重金属的“临界负荷”与可持续管理和发展的关系,在此基础上,提出了城市土壤中重金属可持续发展的初始评估指标(FD)和可持续发展指标(FS);最后,讨论了重金属污染源释放速率的调控措施及其手段。

Heavy metals in urban topsoil have been shown to be very useful tracers of environmental pollution because urban topsoil is the "recipients" of large amounts of heavy metals from a variety of sources including industrial wastes, vehicle emissions, coal burning waste, and other activities. Dust from the ground because of wind erosion may have toxic effects as a consequence of inhalation or ingestion by humans, particularly children, which poses major health hazard. Furthermore, any contamination of urban topsoil could cause in turn surface water/groundwater contamination because metals of the polluted topsoil tend to be more mobile than those of unpolluted ones. In this paper, we firstly probe into the connotation of carrying capacity of heavy metals in urban topsoil, analyze the mechanism and inhabiting factors of heavy metals in urban topsoil, differentiate "absolute carrying capacity" and "relative carrying capacity" and put forward the computing model of relative carrying capacity for heavy metals in urban topsoil. Secondly, the preliminary assessment index (FD) and sustainable development index (FS) are discussed. Lastly the controlling measures on the emissions of heavy metals are discussed.