Xi'an City Parks Physical And Chemical Properties Of Dust And Heavy Metal Contamination

There is certain pollution in human society that advent of the industrial age, substantial growth of population and growing Urbanization initiate. People pay more and more attention to the development of the urban ecological environment, while urban dust is attracting a lot of interest of academic researchers as the people most likely to contact contaminants. Park System is the major place where citizens can relax and contact with nature. However, the human body will receive a series of hazards because of floating, easy to enter the body through respiration and other special properties, particularly will affect children's growth and development. Therefore, researching about urban dust of has important practical significance that the discussion of the ecological quality of the city, the source of heavy metals in dust, heavy metal pollution in parks.The study concentrated on 25 parks in Xi'an city and got by field investigation, sample collection and laboratory analysis, which systematically studied the physical and chemical properties of dust from Xi'an city park (particle size, pH, conductivity, magnetic susceptibility, organic matter and constant component),full amount and chemical speciation of Pb, Zn, Cu, Ni, Mn. The concentration of Pb, Zn, Cu, Ni, Mn which is under different size of dust was analyzed.The potential risks and pollution of heavy metal was analyzed by Geo-accumulation Pollution Index and Potential Ecological Risk Index. The relationship between dust physical-chemical property and heavy metal contents and the possible sources of heavy metals in the dust were discussed by using correlation analysis and principal component analysis to discuss. There are following conclusions:1.The dust of Xi'an city parks had highly alkaline and more alkaline than soil. The pH value not only was affected by the soil in the parks, the more was affected by the alkaline material in dust; The composition of dust was mainly powder particle, the average composition of powder particle size accounted for 62.94%, sand and gravel accounted for 37.06%, which was in relation to the locations of park, the particle size of soil and so on; Conductivity value which was higher than park soil was 2.29 ms/cm; organic matter of dust was 9.02% and the distribution was largely different; High-frequency and low-frequency magnetic susceptibility in dust were higher than those in Xi'an park soil;2. The content of heavy metals elements Pb, Zn, Cu, Ni in dust of Xi'an city parks was exceeded Shaanxi Province background value of soil, which had been marked varying degrees of accumulation, followed by intensity of Pb>Cu>Zn>Ni; According the differences of heavy metal content in different regions park, realizing the heavy metal contents in dust were mainly related with the regional distribution of industry in Xi'an city, and also affected by other pollution sources; Using Geo-accumulation Pollution Index to evaluate that heavy metals elements Pb, Zn, Cu, Ni have a certain degree of pollution,followed by intensity of Pb>Cu>Zn>Ni; Using Potential Ecological Risk Index to evaluate that pollution of heavy metals elements Pb, Zn, Cu, Ni, Mn have emerged and individual heavy metal pollution show Pb>Cu>Zn>Ni>Mn.Potential ecological risk showed Pb>Cu>Ni>Zn>Mn and different potential ecological risk; With the diameter decreasing, the average content of heavy metals elements Pb, Zn, Cu, Ni, Mn in dust with different particles size of Xi'an city parks took on overall upward trend; Using Geo-accumulation Pollution Index to evaluate that heavy metals elements Pb, Zn, Cu, Ni have a certain degree of pollution. Pb, Cu was most polluted in the 0.1-0.15mm of dust particles; Zn was most polluted in the 0.075-0.1mm of dust particles; Ni was most polluted in the<0.075mm of dust particles. Using Potential Ecological Risk Index to evaluate that pollution of heavy metals elements Pb, Zn, Cu, Ni, Mn have emerged. Furthermore, Pb, Cu was most individually polluted in the 0.1-0.15mm of dust particles; Zn was most individually polluted in the 0.075-O.lmm of dust particles; Ni was most individually polluted in the<0.075mm of dust particles. Potential ecological risk showed Pb>Cu>Zn>Ni>Mn and different potential ecological risk in dust with different particles size of Xi'an city parks; However Pb and Cu had high or very high potential ecological risk in particle size range of local parks.3. The modality form of heavy metals and migration and transformation in dust from Xi'an city park showed that:Pb mainly existed in the form of residual state and Residual state, Zn mainly existed in the form of residual state, Cu mainly existed in the form of oxidizable state and the residual state, Ni mainly exists in the form of residual state, Mn mainly exists in the form of residual state;4. By the physical and chemical properties associated with the heavy metal contents analysis, the result showed that no correlation among pH, content of organic matter and particle composition. It indicated the level of heavy metals was less affected by these factors. From the correlation analysis and principal component analysis, industry is the main factor for Cu and Ni. Pb and Zn were not only affected by industry factors, but also were affected by transport activity factors, while Mn may be affected and constrained by many factors.