A Study Of Risk Identification And Risk Assessment In Pollution Of Heavy Metals In Urban Dust Near The Groud In Hefei City

Urban dust near the groud is mainly composed of atmospheric dust, soil dust, construction dust, industrial dust, traffic dust, atmospheric suspended particles brought in atmospheric precipitation and so on, a variety of heavy metal elements such as Cd, Hg, Pb, Cu, Mn, Zn, Cr and Ni are the important environmental pollution in urban dust near the ground. The study of heavy metal pollution distribution in urban dust, analysis the key pollution factor and then carry on the ecological risk assessment, not only has the important theory value, but also has the practical guiding significantion in prevention of heavy metal, construction metal supervision system model and supporting the human health. Based on disagreement on the origin of heavy metals in dust, dust samples were collected by grid throughout the urbanized area in Hefei city. Relationship between metal in dust and urban land-use was assessed. By comprehensive analysis, origin of metal in dust was determined in urban dust. High risk heavy metals and region impact on the soil quality of urban dust were identified, the different impacts in heavy metals on the soil quality of urban dust were assessed, and the prevetion of the heavy metals was suggested.The main content can be divided into four parts.The first part identified the factors of heavy metals in dust.8heavy metal factors in dust samples,8heavy metal factors in soil samples,15heavy metal factors in dry and wet deposition samples were collected. The part analysises the heavy metals content in the dust, soil, atmospheric dry and wet deposition, assesses the heavy metal elements in use of Single factor pollution index method, Nemerow pollution index method and pollution load index method and compares the difference of heavy metals content in different types of industrial area, and preliminary analysis the pollution of heavy metal in hefei city.The second part assessed the pollution risk of heavy metal in dust. Potential ecological risk index is applied in assessing the single element in soil. The method identifies the potential ecological risk index Er of every heavy metal elements and the potential ecological risk index RI of the main city. The use of the Kriging method of interpolation analysis of heavy metals in soil in the main city of Hefei determines the coeffifient of single heavy metal element pollution, the potential ecological risk factor space distribution and the spatial distribution of index of ecological risk in Hefei city.The third part identified the high risk area of heavy metals in dust. This part selects a reasonable heavy metal pollution evaluation index system, and normalized the individual indicators. The use of cluster analysis method to determine Cd is the high risk factor in heavy metal in dust, Hg, Zn is the medium risk factors in heavy metal in dust, and As, Cu, Pb, Ni are the low risk factors in heavy metal in dust. So in the prevention of heavy metal we must pay more attention in Cd, Hg and Zn. Using the Kriging method identifies the high risk area in atmospheric dust and atmospheric dry and wet deposition, through the overlay analysis to determine the high risk area in heavy metal pollution.The forth part focused on the suggestion of heavy metal prevention in dust. The environmental supervision in heavy metal pollution is introduced by application of system dynamics in heavy metal prevention. Many problems are discovered in several aspects, for example, the scattered layout, the imbalance in project environmental management, and the difficulty in acceptance and daily supervision. Based on these issues, the solution is proposed including improving the layout, establishing the long-term mechanism in regulatory and approval, achieving the government information, and which emphasizes the integration of market mechanism and national macro-control, the importance of the integration of direct supervision, stimulus control and self-regulation.