Contamination And Spatial Distribution Of Heavy Metals In Roadside Soils Of Zhengzhou-shangqiu Section, Longxi-Haizhou Railway

Soil system is the basic unit of the biosphere, and it is one of the main research objects of environmental science. If this system is polluted by heavy metals, the environmental quality of atmosphere and water will be severely affected, and finally do harm to human health through food chain. 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 a source of environmental pollution, automobile exhaust is a kind of important soil chemical contamination source. With the development of the transportation carrying trade, vehicles possessions increase rapidly. Accordingly, the increased traffic volumes have brought about serious heavy metal contamination along railway. Therefore, the monitoring and assessment of the soil metal contamination will be in favor of illuminating the residual and accumulating mechanism of the heavy metal in the soil system.In this dissertation, the contamination and Spatial distribution of heavy metals ( Pb,Cd,Ni,Cu,Zn,Cr) in the railway side, soil system along Zhengzhou-Shangqiu section of Longxi-Haizhou railway 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, and 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 the soil system were generally introduced. Then author summarized the present situation of the study at home and abroad on the heavy metal contamination in soil system 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 samples along Zhengzhou-Shangqiu railway were also presented. Finally, the methods of the experimental items were expounded.PartⅢBased on the experimental data , the heavy metal contamination levels of soil along Zhengzhou-Shangqiu railway were assessed. The law of distribution and migration of heavy metals in the soil was analyzed. The factors that impact the heavy metal migration were also studied.PartⅣIn this part , the main conclusions were drawn. At last, the author pointed out some limitations of this study and further put forward some expectations for the future study.Central conclusions are as follows:(1) The heavy metal contents of the soil surface layer along Zhengzhou-Shangqiu railway(0～300 m) is higher than our country cultivated soil background value, is also obviously higher than the comparison value.(2) The heavy metal contamination of the soil surface layer along Zhengzhou-Shangqiu railway(0～300 m) has been extremely obvious, the synthesis pollution index mostly achieves the heavy pollution. Pb contamination is serious, synthetic contamination index and the distances from railway side are negative correlation. The both sampling transects form the contamination belt within the distance 50m from the railway side of highway.(3) Concentrations of heavy metals in roadside soils decrease with distance from the railway, and concentrations and the distance are not simply negatively correlated. Most heavy metal concentrations in the soil of the sampling transects are increased with distance from the railway, most of heavy metal concentrations reach a peak value or the inferior peak value at the distance of 50m scopes from railway, then gradually drops to the comparison value.(4) The heavy metals mainly accumulate in soil surface layer (0~20cm). Concentrations of the heavy metals decrease with depth.(5) Concentrations of heavy metals in railway sides are mainly with the distance from the railway, which are not obviously related with the soil nature.