Analysis And Assessment Of Heavy Metal Concentration Of Vegetable Cultivated Soils In AnNing District Of Lanzhou

Heavy metals are the sixty elements whose proportion is more than 4.0,or are the forty-five elements whose proportion is more than 5.0.With the socity and ecoomic development, the problem of environmental pollution is outstanding day by day.The soil is regard as an important component of the environment.The soil pollution ,especially the soil heavy metal pollution arouses people,s widespread interest.After the soil is polluted by the heavy metallic elements,these harmful elements will enter finally the human body through the food chain,which will do harm to the human health.In this thesis,the status of heavy metals(Cu,Zn,Cd,Pb,Hg,Cr)pollution in the soils of AnNing Suburb of Lanzhou was investigated and evaluated.The results were showed as follow:1. Except the concentration of Hg and Cr was lower than the mean level of the metal obtained based on Lanzhou City,the soil was polluted by Cu,Zn,Cd,Pb.The average content of heavy metals( Cu,Zn,Cd,Pb) was as over once as background value of soil element of Lanzhou.2. There was a trend of soil heavy metal concentration in soil profile this vegetable cultivated area. The soil heavy metal concentration of top layer (0-20cm) was greater than under layer (20-40cm). On the contrary, the content of Cd under layer (20-40cm) was greater than top layer (0-20cm).3. Correlation analysis indicated that there was significantly positive correlation between Cr and Cd. There were highly significantly positive correlation between Cr and Hg,Cr and Pb,Cr and Cu,Cr and Zn,Pb and Hg,Cu and Hg,Zn and Hg,Cu and Pb,Zn and Pb,Zn and Cu,Hg and Cd,Cd and Pb,Cd and Cu,Cd and Zn.4. The correlation between soil quality and the concentration of soil heavy metals was significant or highly significant. The concentration of Zn and Cd was remarkably negatively correlated with pH. The concentration of Pb was negatively correlated with pH. Except for Cr, all the soil heavy metals were positively correlated with soil organic matter. There was significant correlation between Hg and organic matter. There was remarkably positively significant correlation between organic matter and Cd,Cu,Zn,Pb. There was no correlation between nitration and Hg,Cr. The correlation between Pb and nitration was positively significant correlation. There was remarkably positively significant correlation between nitration and Zn,Cu,Cd.5. The order of the comprehensive pollution index was Cd>Zn>Cu>Cr>Hg>Pb.6.From the comprehensive pollution index of all samples using Secondary Standard of GB15618-1995 as assessment standard, the comprehensive pollution index of sample15,20,37,42 was more than 0.7 and less than 1,which indicated that pollution degree was on alert , pollution level was still clean. The other samples, comprehensive pollution index was less than 0.7, which indicated that pollution degree was safe, pollution level was clean.7.Using Secondary Standard of GB15618-1995 as evaluation standard, the result showed that Kongjiaai and Shilidian pollution grade was 1, pollution degree was on alert , pollution level was still clean . Liujibao and Diaochang pollution grade was degree 1, pollution degree was safe, pollution level was clean. The order of comprehensive pollution index was Kongjiaai>Shilidian>Liujibao>Diaochang.