| In this paper, a direct land application of sewage sludge is studied as the research object. Though the field survey and laboratory analysis,comparison study is analyzed by the physical and chemical properties,nutrient content,six heavy metals content and contamination of soil sample of digging in different times. This paper is divided into five parts:Partâ… : Introducing the current situation of land application of sewage sludge, the main treating methods and the background and significance of this research.Partâ…¡: Making a regional outline introduction of Pingdingshan city, including landforms, climate, industry, economy and other aspects.Partâ…¢: Giving a detail instruction on outline of sample region, the distribution of sample plots, soil sampling process, pre-training; experimental project and method.Partâ…£: Putting emphasis on the land influence of physical and chemical properties, nutrient content and content of heavy metal by applying the sewage sludge.Partâ…¤: Assessing the pollution condition by three methods and calculating the dynamic capacity of heavy metals.Conclusion can be drawn as follow:(1)There is a decline trend of pH and soil bulk density by the increasing times of land application of sewage sludge. Compared the soil profile #4 and #0, the mean value is lower 0.3 pH units and 0.2g/cm3,but the state of the soil is still alkaline. There is ascending trend of soil CEC content with the increasing times of land application of sewage sludge.The mean CEC content of #1~#4 profile is improving quickly from15.4% to 38.9% in contrast to the #0 profile. However, the change of soil CEC content is complex with the depth change.(2)The content of soil organic matter, available N, P and K is increased by application land of sewage sludge with the increasing times, the order is #4>#3>#2>#1>#0, and there is obvious improving of available P and N in the topsoil. Through the comparison of #0 and #4, the organic matter content is increased form 9.7g/kg to 15.3g/kg, improved 57.7%; the available N increased from 22.33mg/kg to 53.07mg/kg, improved about 2.4 times higher; the available P is increased from 5.32mg/kg to 17.48mg/kg, improved about 3.3 times higher; the available K increased from 73.7mg/kg to 79.8mg/kg, improved about 8.3%.(3)There is a whole decline trend that the content of organic matter, P and N with the increased depth.(4)There is a phenomenon that the content of heavy metal is increased by application land of sewage sludge by using more times and declined with the increased depth. By the comparison of profile #0 and #4, the mean content is increased from 29.28 mg/kg,83.05 mg/kg,29.05 mg/kg,0.38 mg/kg,30.65 mg/kg,59.69 mg/kg to 35.8 mg/kg,99.39 mg/kg,37.68 mg/kg,0.41 mg/kg,39.28 mg/kg,92.00 mg/kg of Cu,Zn,Pb,Cd,Ni,Cr, the Cr is obviously increased.The increased span of content of heavy metals in topsoil is larger than in subsoil, and there is some difference of increased span by different elements.Although the content of heavy metals in soil is increased, the result of four profiles reveals the soil quality is in a safe level and the soil is not polluted by heavy metals if we consider the whole profiles as the assessment object.If we consider the topsoil as the assessment object, the result of evaluation shows there is a three level pollution phenomenon. As for the result of the #0 has gotten a three level, excluding the effection of which, the soil quality will be enhanced by land application of sewage sludge and the pollution of heavy metals will not be serious.
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