| The urban soil which is the foundation of human life and product is one of the most important parts of the urban ecosystem. Hourly human activity leads distinguishing degree contaminations in urban soil, which has had the negative influence to the stability of urban ecosystem and human health. In recent years, the condition of urban soil heavy metal pollution has aroused public's attention. Through the choices of urban zones in different type areas, many studies took samples on the spots, made the analysis of urban soil heavy metal, tried to find the important sources of urban soil heavy metal, described the characteristics of spatial distribution, chemistry modalities and influencing factors of heavy metal in urban soil, as well as had carried out the research to human body's health risk and the biological effect. All these studies were to provide powerful support of knowing urban soil heavy metal pollution conditions and characteristics about how it changes. In order to offer scientific references about how to control, supervise, renovate and father urban soil heavy metal, My study was conducted in two kinds of geography scale to investigate the heavy metal contamination in soil of Xuhui Minhang and Fengxian, Shanghai, and value it.The result is:the average concentrations of total Cr, Cu, Mn, Pb and Zn are 87.72,27.80,556.97,28.86,99.36mg/kg. The concentrations of Cu and Mn are lower than the background level while the concentration of Pb has just pass the background level. The concentrations of Cr and Zn are higher than the background level.Urban transportation section of heavy metal analysis shows that, by the unilateral control of traffic pollution, soil contamination of heavy metals depends on the distance from the road traffic. Farther away from the road, the impact of soil pollution by the transport was smaller. Soil Pb, Zn pollutions were lighter, significantly decreasing trend. When the cross section on both sides were affected by traffic pollution, the distribution of soil heavy metals were complex. The certain region accumulated the phenomenon of superposition.The correlations between Zn-Cu, Zn-Pb, Pb-Cu, Mn-Cr compose leading 4 groups of heavy metals in the 260 samples.According to ArcGIS map analysis, combined with access to relevant documents, the study obtained the result that Zn, Pb, Cu these three kinds of heavy metal pollution mainly come from traffic, Mn and Cr mainly come from industrial sources. Across the study of city-suburb-rural gradient area, traffic source has covered other sources of pollution and become a leading source of heavy metal pollution.Different land use areas by type of sampling results show that industrial areas the Cr content of the soil is the highest. The Cr content of the soil shows that: Commercial> Residential> Public green> Agricultural areas. The differences between the various functional areas of Cr content are not significant. The Cu content of the soil sizes as:Business district> Industrial areas> Residential areas> Public green> Agricultural areas. The differences between the various functional areas of Cr content are not significant. The Mn content of the soil sizes as:Residential areas> Industrial areas> Public green> Business district> Agricultural area. The differences between the various functional areas of Mn content are not significant. The Pb content of the soil sizes as: Residential areas> Business district> Public green. However, Pb content in the soils spatial variability is large. The Zn content of the soil sizes as:Business district> Residential areas> Industrial areas> Public green> Agricultural areas.The evaluation results of the soil heavy metal in various functional areas show that:soil heavy metal in most of the agricultural regions less than the soil background level, the soil is light polluted. There are certain soil heavy metal accumulation in industrial, residential, commercial areas and public green land area. Soil heavy metal values in these areas are more than the soil background value and the Comprehensive Pollution Index reached mild pollution levels. This reflects that in different land use conditions, the strength of human activities, the time of contaminants accumulated, the distance to the pollution sources and other factors on the accumulation of heavy metals in soil result in the accumulation of soil heavy metal.The city-suburb-township gradient soil heavy metal pollution situation is: Xuhui (town center)> Minhang (suburb union area)> Fengxian (rural area). Unified with ArcGIS charting analysis, the highest area of Nemero contamination index stands in downtown area. Nemero contamination index decreases as type of band from north to south according to downtown-suburb-suburban area. The predominant factor which causes this kind of soil heavy metal gradient decrease shape is the urbanization:the urban center region has been urbanized for a long time. In center area, with the gather of population and the raise of transportation, the heavy metal gets a long-term accumulation to make the content reach a generally high level. The suburb region's high speed urbanization creates the fast increase of population, brings swift growth volume of traffic. The change form agricultural land to newly built industrial district, inhabited area and the business district caused the fast accumulation of soil heavy metal.
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