不同级别城镇土壤重金属污染状况比较分析——以郑州市、中牟县和韩寺镇为例

选取自然条件类似但工业化、城镇化水平明显差异的郑州市、中牟县和韩寺镇,在野外调查取样、室内化验分析的基础上,运用地积累指数法比较了土壤Pb、Cd、Zn、Cr、Cu、Ni等6种重金属元素的污染特征。结果表明:(1)城镇土壤主要污染元素为Pb、Cd、Zn、Cr,基本上不存在Cu、Ni元素的外源性累积;由于受人为活动干扰,城镇土壤重金属元素具有强烈的变异性。(2)城镇土壤Pb和Cd污染主要与工业、交通废气沉降有关,Zn污染除工业、交通因素外,还与居民日常生活废弃物排放密切相关;工业区、交通密集区以及居民区土壤重金属污染程度显著高于其他功能区。(3)Pb和Cd在各研究区的累积程度的大小顺序为郑州市区>韩寺镇区>中牟县城>对照区,Zn为中牟县城>郑州市区>韩寺镇区>对照区,而Cr污染除在对照区略小之外,其他三个区域相差不大;不同级别城镇土壤重金属污染的差异是人为活动的历史累积作用和近年来城镇化、工业化影响作用相互叠加的结果。

Comparison of Heavy Metal Contaminations in Different Ranking Urban Soils: A Case Study of Zhengzhou, Zhongmu and Hansi, Henan, China

An attempt was made to investigate heavy metal pollution in urban soils as exemplified by Zhengzhou City, Zhongmu County and Hansi Town, which share similar natural conditions but have different levels of urbanization and industrialization.The contents of Pb, CA, Cu, Zn, Cr and Ni in soil samples, eolleeted from these areas mentioned above, were analyzed through indoor determination. By adopting the approach of index of geoaeeumulation, the results showed that: (1) The main contaminated elements in urban soils are Pb, Cd, Zn and Cr. However, there does not basically exist exogenous accumulation of Cu and Ni. Due to artificial disturbance, heavy metals in urban soils show great variability. (2) Pollution of Pb and Cd is chiefly caused by waste gases from traffic transportation and industrial activities, and Zn pollution is mainly caused by residential daily lives, traffic transportation and industrial activities. The pollution degree of heavy metals in industrial districts, traffic areas and residential regions is obviously higher than that of other urban functional types. (3) The accumulated pollution of Pb and Cd in these study areas follows the order of Zhengzhou City>Hansi Town>Zhongmu County>contrasted area, and Zn follows the order of Zhongmu County>Zhengzhou City>Hansi Town>contrasted area, but Cr pollution among these three town areas changes little, with the exception that Cr pollution is slight in the contrasted area. Differences in heavy metal contaminations for the three urban soils are due to long-term accumulation effects of human activities as well as urbanization and industrialization in recent years.