不同级别城镇土壤重金属含量与潜在生态风险比较——以郑州市、中牟县和韩寺镇为例

Comparison between Heavy Metal Contents in Urban Soils and Their Potential Ecological Hazards in City and Town:a Case Study of Zhengzhou,Zhongmu and Hansi,Henan,China

以郑州市、中牟县和韩寺镇为例,在野外调查取样、室内测定的基础上,比较分析了Pb、Cd、Zn、Cr、Cu、Ni6种重金属元素在不同级别城镇土壤中的分布特征与潜在生态风险。结果表明:(1)不同重金属在各级别城镇土壤中的分布特征不尽相同。土壤Pb、Cd的分布趋势基本一致,而且含量普遍超过一级环境标准值,具有工业化、城镇化水平越高土壤污染越重、人为扰动越大的特点;土壤Zn、Cr含量在各区域的分布差异显著,体现了人为活动方式与活动强度的复杂性;不同级别的城镇土壤基本上不存在Cu和Ni的富集,两者含量的变化主要受自然波动的影响。(2)各级别城镇土壤存在着不同程度的重金属潜在生态风险,其中Cd的潜在生态风险最大,构成了很强的潜在生态危害,而Pb、Zn、Cr和Cu等元素仅具有轻微生态危害。(3)多种重金属的潜在生态风险大小为:郑州市区>韩寺镇区>中牟县城>对照区。

With the example of Zhengzhou city,Zhongmu county and Hansi town,the concentration of Pb,Cd,Cu,Zn,Cr and Ni was analyzed through field investigation and indoor determination.Then the author compared the distribution properties and potential ecological hazards of those analyzed heavy metals in different ranking urban soils.The results show as follows.The distribution properties of different heavy metal elements are also different with each other in different ranking urban soils.In detail,the general distribution patterns of Pb and Cd are in substantial agreement.And the content of Pb and Cd are generally higher than the first standard of soil environment,from which we can know that the higher the levels of the urbanization and industrialization are,the higher pollution and the greater artificial disturbance will be in urban soils.The distributions of Zn and Cr have significant difference in different ranking urban soils,which embodies complexity of anthropological activities.No obvious concentration of Cu and Ni is found in all study areas.The contents of Cu and Ni fluctuate mainly by natural fluctuation of background of heavy metal elements.（2） There exist heavy metal potential ecological hazards in different ranking urban soils to different extents.Among the five analyzed heavy metals,the potential ecological hazard of Cd is highest,meeting very strong potential ecological hazard in urban soils.But,in contrast,Pb,Zn,Cr and Cu merely reach slight ecological risk.The hazards between four study areas follows：Zhengzhou cityHansi townZhongmu countycontrast area.The result also supports the view that all three urban soils and contrast area have comparatively high hazards.These results provide certain scientific foundation for urban and rural planning,environmental treatment and ecological remediation,also ring an alarm for the eco-environment of some small towns.