Effect On Heavy Metal Contamination In Roadside Soils Of Highway At Different Operation Time

Soil is one of the most important resource for mankind. The heavy metal contamination mainly derives from industrial waste, municipal solid waste, pesticide and fertilizer as well as automobile exhaust and so on, in which we should attach importance to traffic pollution. As the source of environmental pollution, automobile exhaust is one kind of important soil chemical contamination source. With the development of the transportation carrying trade, vehicles possessions increased rapidly. Accordingly, the increased traffic volumes have brought about serious heavy metal contamination along highway. Therefore, the monitoring and assessment of the soil heavy metal contamination will be in favor of illuminating the residual and accumulating mechanism of the heavy metal in the soil.In this dissertation, the contamination and migration of heavy metals ( Pb,Cd,Ni,Cu,Zn,Cr) in the roadside soils along Lian-Huo highway were studied. On the basis of experimental data of the heavy metals in soil, the author analyzed heavy metal contamination status and law of migration of heavy metal, then discussed the factors that affect the migration of heavy metal pollutants in the area.There are four main parts of this dissertation:PartⅠIn this part, the current situation and development tendency of the research about heavy metal contamination in soil system were generally introduced. Then the author summarized the present situation of the study at home and abroad on the heavy metal contamination in soil caused by traffic problem.PartⅡIn this part, the basic conditions of the research area and the sampling transects were introduced. Then the collection and preparation process of the soil along Lian-Huo highway were also presented. Finally, the methods of the experimental items were expounded. PartⅢBased on the experimental data , The law of distribution and migration of heavy metals in the soil was analyzed. The heavy metal contamination levels of soil along Lian-Huo highway were assessed.The the factors that impact the heavy metal migration were also studied.PartⅣIn this part , the main conclusions were drawn.Central conclusions are as follows:(1) The heavy metal contents of the soil along Lian-Huo highway obviously exceed the local background values, except Cr and Pb. Both sampling transects form the slight contamination belt within the distance of 300 m from the roadbed of highway, and the most serious pollution sampling point were all in the range of 0-50 m.(2) The heavy metal contents of the soil along Zhengzhou-Kaifeng section obviously exceed Kaifeng-Shangqiu section, It's pollution level was more secious than Kaifeng-Shangqiu section, It's most serious pollution sampling point was nearer the roadbed. The reason may be that the two sections had different operation time.(3) Change law of the heavy metals contents in roadside soil was different with distance from the highway, Some heavy metal concentrations were firstly increased then decreased with the distance, the other are high in the range of 0-5m from the roadbed of highway, than firstly decreased then increased,then decreased with the distance.(4) Most heavy metal concentrations reach maximum values in the range of the15～100 m from highway. Exceptional heavy metal's content curves were provided with double- peaks.(5) Heavy metals entering into soil mainly accumulate in the surface layer(0～20 cm). Concentrations of the heavy metals decrease with depth.