The Research Of Heavy Metals Pollution In The Soil Of The Xi’an City Park

Heavy metal is one kind of the potentially pollutants in the soil. And once the soil is suffered by heavy metal, it will be very difficult to completely remove the pollution. The city parks are devoted to the public for leisure and entertainment. So the quality of the park soil, especially the heavy metals, will affect the health of the residents. And the children are more sensitive to the heavy metals. So it is significant to research the heavy metals pollution in the soil of the city park.Heavy metal concentration and chemical speciation of Cu, Ni, Zn, Cd and Pb were analyzed for the surface soil samples taken from the11city parks inside the Xi’an Second Ring Road. And the heavy metals pollution level and the potential ecological risk were evaluated by Nemero pollution index and Hakanson potential ecological risk index. The correlations between the soil physicochemical properties and the Heavy metal concentration, the soil physical-chemical properties and the chemical speciation, the Heavy metal concentration and the chemical speciation, the Heavy metal concentration and the Heavy metal concentration were analyzed. The pollution sources were analyzed by principal component analysis and cluster analysis. The results were as follows:(1) The soil appeared alkaline and the average pH was8.18. The soil contained plenty of organic matter. And the moisture content was appeared in different soil samples.(2) The average concentrations of Cu, Ni, Zn, Cd and Pb were33.49mg/kg,23.44mg/kg,86.54mg/kg,0.157mg/kg and53.63mg/kg. And the percents of the concentrations beyond the criteria of the1st Standard of Soil Environment Quality were35.26%,1.28%,26.92%,21.15%and91.03%. And all samples were not beyond the criteria of the2nd Standard of Soil Environment Quality.(3) The chemical speciation of Cu, Ni, Cd, and Zn mainly existed in residual form, and Pb mainly existed in oxide form. The availability was in the order of Pb>Cu>Zn>Cd>Ni.(4) The maximum single pollution index was Pb of2.51and the minimum was Ni of0.82. The single pollution index was in the order of Pb>Cd>Cu>Zn>Ni.(5) The average Nemero index was’2.87, that was the soil has been moderately polluted by heavy metals. And the soil of North Area of Xi’an City Wall Park contaminated by heavy metals was the most severe.(6) The elements potential ecological risk index of Cu, Ni, Zn and Pb were7.83,4.04,1.25, and12.53. The maximum elements Potential ecological risk index were Cd of50.26.(7) The average potential ecological risk index was75.90, that was the soil presented a slight ecological risk.(8) The pH of the soil had positive correlation with Cu, Ni, Zn, and Pb, except Cd. The soil organic matter had positive correlation with the heavy metal concentration and had significant positive correlation with Pb. The moisture content had low correlation with heavy metal concentration.(9) Cu, Zn, and Pb had the significant positive correlation with each other. Cd had positive correlation with Zn, and had low correlation with other elements. Ni had the significant positive correlation with Zn and Pb, and had low correlation with Cu and Cd. Heavy metal concentration had the positive correlation with chemical speciation.(10) The principal component analysis and cluster analysis showed that the pollution source of Cd was different from other elements.