生活垃圾填埋场封场后种植植物中重金属迁移研究

在上海老港生活垃圾填埋场填埋单元封场的覆盖土中掺混了矿化垃圾种植植物,分析Cd、Pb、Cu、Zn 4种重金属在土壤和植物中的迁移变化,研究表明:(1)覆盖土土质从一般耕作土变成肥沃土壤;覆盖土和种植混合土重金属Cd、Pb、Cu、Zn中Cd、Pb含量相近,但种植土的Cu含量略大于覆盖原土,Zn含量远大于覆盖原土;(2)植物能富集土壤和垃圾中的重金属,木本植物的根部富集重金属的能力强于草本植物,但重金属在草本植物根、茎、叶中的迁移速度大于木本植物;(3)植物根、茎、叶的Cu、Zn含量均远大于未受污染土壤种植植物相应部位的Cu、Zn含量,种植的植物不能供家养动物食用,以免通过食物链作用危及人体安全.

Distribution of heavy metals in cover soil and vegetation of closed sanitary landfill

Mineralized refuse (> 8 years) was mixed into the cover soil before planting of the landfilling compartments closed for more than 5 years in Shanghai Laogang Sanitary Landfill. Measurements of 4 heavy metals (Cu, Pb, Zn, Cd) were performed on samples of the mixed cover soil and parts (root, trunk and leaves) of typical annual and wooden plant to study the transport of metals as a function of time. Relative to the base cover soil, the slightly more acidic mixed cover soil was enriched with C, N and P species resulting from applied fertilizer and/or bacterial actions; its Cd and Pb contents remained about the same while its Cu content was higher and that its Zn content was much higher. The changes were more notable for the compartment with a longer planting history as more nutrients and metals were released from the aged refuse. Data on metal concentrations of the vegetation samples also demonstrated accumulation of Cu and Zn in the same pattern. More metals were accumulated, although at lower rates, in the wooden plant than the smaller annual. Vegetation of those close landfill compartments should not be used for direct animal consumption to avoid transfer of the harmful metals in the food chain.