| Jilin, Changchun and Siping Cities are located in the middle in Jilin Province, which is the political, economic and cultural center belt of the Province and Changchun City is in the core of the belt. With the urbanization process to accelerate, a large number of organic and inorganic pollutants have been thrown into the environment by human activities, causing pollution of the urban environment, so urban topsoil has become the main carrier of these pollutants. In this paper, soil heavy metals and etc. are studied and evaluated synthetically based on eco-geochemical investigation results of the topsoil layer carried out in three urban cities , with the integrated use of Excel, SPSS, GIS and geostatistical software GS +, etc., using statistical analysis, a single factor index, Nemerow comprehensive index, the potential ecological risk index . At the same time, evaluation of the the topsoil and shallow groundwater quality comparison, evaluation of organic matter in topsoil and end-dust have been made. The soil eco-geochemical quality zoning and the concept of "L-shaped" economic zone are given thus the development ideas are proposed.Through the above work, main conclusions are as follows:1. Studies of the statistical characteristics of topsoil element (mainly heavy metals) content, of structure chraracteristics and spatial distribution show that the topsoil elements of Jilin, Changchun and Siping cities is mostly normal (or near-normal) or log-normal (or near-lognormal) distributed. The average content of urban topsoil are from 1 to 3 times higher than the local background values except the condition of lack of background values. Hg in Jilin City is 10 times and in Siping City 8 times higher than the local average background value.2. Statistical analysis based on the semi-variance model shows that the urban layout of human activities, particularly of industry has effect on heavy metal contents in urban topsoil. Elements nugget effect becomes larger and its range becomes smaller. However, the spatial distribution of topsoil in the three cities is still controlled mainly by the natural spatial patterns.3. Topsoil pH values of the three cities have shown an increase from the periphery to the urban centers of alkaline trend.4. The analysis have shown that the prevailing wind direction may superimpose effects on the distribution of the surface heavy metals, which may drift along the wind direction.5. Comparison of the topsoil heavy metals were carried out in Jilin, Changchun and Siping Cities, the single factor index method, Nemerow comprehensive index method and the improved BPANN method were applied for quality assessment. Evaluation by Nemerow comprehensive index method for the three cities was light pollution . Evaluation by the improved BPANN method for the three cities was level I-and II. Quality of the topsoil are merits of the order of Changchun > Siping > Jilin , by Nemerow comprehensive index method and the improved BPANN method.6. Combined with eco-toxicity and ecological hazard assessment of potential ecological risk index, the results have shown that ecologuical risk of soil of Jilin, Changchun and Siping wew respectively medium, medium and high hazard. The order of the three urban topsoil ecological risk assessment were Changchun > Jilin > Siping, the main ecological risk elements were Hg and Cd (Hg > Cd). Sum of moderate ecological risk and the strong share of the scope of ecological risk were more than 75%, which should attract enough attention.7. Preliminary studies of PAHs in topsoil, metallurgy, coal, traffic and exhaust end-dust In Jilin, Changchun and Siping cities have shown that PAHs of end-metallurgical dust in Jilin were significantly higher than that in Changchun and Siping. And main PAHs with molecular weight 4-6 ring were high in the strong potential carcinogenic and mutagenic. Analysis of PAHs in coal, gas and traffic dust in Changchun have shown that the low-ring PAHs mainly came from coal-fired and industrial processes of coal and crude oil, and vehicle exhaust as well as some contributions. High molecular weight PAHs mainly came from the vehicle exhaust emission. Analysis of topsoil PAHs in Changchun and Jilin have shown that most of PAHs in soil were high-ring PAHs (4-6 Changchun , 4-5 rings Jilin), PAHs were higher in Jilin than in Changchun, and the extreme difference was significant. The analysis have shown that the reasons for the high PAHs in Jilin were it is an important chemical and metallurgical industrial city in the province. Overall, PAHs pollution in topsoil of Jilin and Changchun were lower than that of other cities in China.8. A Case Study of Changchun urban topsoil and shallow groundwater was carried out simultaneously, the heavy metal distribution and its internal relationship in soil and groundwater are analyzed, and evaluation on heavy metals pollution of Changchun shallow groundwater with single factor index and Nemerow comprehensive index have been taken. Researches have shown that heavy metals in groundwater pollution has emerged in Changchun, Heavy metal pollution in the contaminated area was mainly clean and potential, the two had a similar range, except the island-shaped area in the north of Yingjun Iron Works was heavily polluted.9. The author believes that heavy metals in the topsoil and vadose zone affect heavy metal content in groundwater in the water circulation system, and the affect factors are complex. High content of surface does not necessarily correspond to areas of high content of heavy metals in groundwater, but the high content of heavy metals in groundwater, topsoil or nearby areas may be high. Because of the potential scope of the region accounted for about half of the contaminated area, taking into account the effect of potential ecological risk of heavy metals, the potential pollution of heavy metals on the groundwater should attract enough attention.10. Based on the eco-geochemical evaluation of the topsoil, mainly accorded the potential ecological risk assessment map, and both Nemerow and BPANN quality assessment index map was partly considered, topsoil environmental quality of Jilin, Changchun and Siping is divided into some zones. Jilin is divided into two zones: good and bad ecological environment. Changchun into three zones: good, common and poor ecological environment. Siping (not divided): common ecological environment.11. Based on the integrated analysis of geological background and soil conditions, the economy concept and development ideas of "L-shaped" economic zone of Jilin - Changchun - Siping is proposed with the help of "point axis theory". This economic zone is the economic axis of economic development of Jilin Province with Changchun being the core axis, Siping and Jilin being the two axis points. Considering the existing characteristics of the cities, the size the center city Changchun should be unified to plan and control so that the city may be stably developed with its good radiation, thus both the urban ecological environment deterioration process is controlled, and development of the small and medium towns in the second and third rank is promoted. Finally, a high economic growth area is formed. Also, the "L-shaped" economic zone overlaps partly "the developing and opening-up Chang-Ji-Tu Pilot Area" approved by the State.
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