| In recent years, there are greatly impacts in the soil environment with high strength human actives, and the problem of heavy metal pollution in soil environment becomes more and more serious, especially in the Yangtze River Delta, the area of intense absence resources and rapidly economic development, therefore, heavy metal pollution arouses widely attention by human beings. Kunshan city, located in Yangtze River Delta has experienced a rapidly industrialization, urbanlization and intensive cultivation in agriculture in the recent30years. Study on the heavy metal pollution status in Kunshan City with multi-variances and factor kriging analysis will help us understanding the potential risk on ecosystem from heavy metal pollution and the pollution sources. The study can also provide some reference to the continuable application and management with soil resources. The following results were obtained.(1)Analysis on the heavy metal pollution degree showed that all soil samples collected in Kunshan City were polluted by heavy metal in different degree. Few of them are in serious pollution status, most of them are in medium pollution and part of them are in low-grade pollution by heavy metal. Though the soil physical and chemical characters have showed some relation to the heavy metal content, they can’t account for all the difference of heavy metal content. The exterior factors, especially human activities can be the most important factor that caused the increasing of heavy metal content.(2) Otherness verification analysis on the heavy metal content and pollution index in the sampled soil showed apparent difference in the soil samples collected in the region with different topographty for most of the heavy metals in the study; the otherness verification analysis also showed that the heavy metal content has difference for different product region. It is remarkable for the Hg difference between the region of chemical plant and printing plant, and Cr difference between the region of printing plant, smelting plant and chemical plant.(3)Analysis on the spatial structure of these heavy metal with geo-statistical method showed that the content of Hg, Cu, Ni and Pb were moderately auto-correlated in a given spatial range. With the selected model, ordinary Kridging interpolation method were used as interpolation strategy to study the heavy metal content spatial pattern with the Geostatistics module provided by ArcGIS9.2software. It showed that Hg content is high in the central Kunshan city and showed a belt with high content in the north of Kunshan city. And the region with high As content are mainly located in the southwest of Kunshan.(4)The analysis on the sources of heavy metal in the soils showed some feature of exterior source for heavy metals. The pollution is serious from Hg and Cd. And the pollution from As, Pb and Zn are also upper. Only content of Cr in the soil samples are similar to soil background. The irrigation with sullage is the main source of Hg, Cd and Pb; printing plant can account for most of the pollution of Cr and Ni; electron plant has bring most of the Zn and Cu pollution. And the smelting and electroplating have some effects on the content of Hg, Cd, Pb, Cr, Ni, Zn and Cu in the soil of Kunshan City. The As pollution has some relation with the waterbody distribution. The content of As is higher in the regions with a higher density of rivers and lakes.(5)Ecosystem risk from As, Zn, Cu, Cr and Ni are in trivial-grade currently for all the126samples, but Ecosystem risk from Cd for84.9percent samples are in moderate-grade status,2.4percent of them are high-grade and1.6percent of them are in very-high-grade. The ecosystem risk from Hg are mainly in moderate and high grade. The ecosystem is mainly loading the pressure from Cd and Hg contamination. The spatial pattern of risk index for Pb, Cu, Hg, Cr and Cd showed similar because the high risk region are mainly located in the Penglang township. It can be accounted by the industry distribution. Several sources of heavy metals can be explained by log accumulated probability figure. |
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