| Urbanization is a radical process of land utilization change.During this process,serving function of soils has experienced an obvious change from maintaining plant growth to retention,conversion and purification of pollutants.Therefore,urban soils play important ecology serving role and protecting urban environment in urban ecological systems.Just because of the conversion of serving function of urban soils,quality of urban soils also changes greatly,especially heavy metal contaminations.With the rapid development of industrialization and urbanization,influences of cities is increasingly enlarged,even many towns have the tendencies to urbanize.In order to alleviating the negative effects of human activities on soil ecological system,strengthening the quantitative study of urban soil environmental effects on city-county-town ecological belt is a tendency in urban soil study in the future.The study objects of this thesis are town areas of Zhengzhou city,Zhongmo county and Hansi town(belong to Zhongmo county),which have the similar natural conditions,whereas to study the distribution and contamination of heavy metals in different ranking urban soils.The aim is further to enrich the theories of urban soils and to provide the theoretical base for the city construction in the new century.In this study,the author divides sampling units according to different functional districts.In detail,there are nine profile sample sites in Zhengzhou city,three profile sample sites and one mixed sample site in Zhongmo county,and one profile sample site in Hansi town.In addition,three sample sites are selected in contrast area(beyond the urban areas).Based on experimental analysis,the author analyzes the distributions and pollutions of six heavy metals(Pb,Cd,Cu,Zn,Cr and Ni),and discusses the mainly influential factors of heavy metal pollution.There are five main parts of this dissertation:Partâ… The history of urban soil study and the latest study advances about urban...
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