Analysis and Evaluation on Heavy Metal Contents in Farm Land Soil and Vegetables of Yuzhong County

In order to investigate the pollution situation of heavy metals in farm land soil and vegetables of Yuzhong County,the vegetable and the soil of cultivation layer were collected from representative farm land at harvest time.The contents and pollution degree of Cd,Cr,Hg,Pb,Cu and Zn were analyzed and evaluated in this paper.Results:1)The contents of Cd,Cu,and Zn in all soil samples were higher than the background values of Lanzhou soil,and the contents of Cr in 33.3% soil samples exceeded the background values of Lanzhou soil,while the content of Hg was not detected.Compared with the GradeⅡof environment quality standard for soil(GB 15618—1995),only the content of Cd in all of the samples exceeded the standard,while Cr,Cu,Pb,and Zn were under the standard.Correlation analysis indicated that several heavy metal elements including Cu and Pb in soil had a greater possibility to have come from the same source,however,Cd,Cr,and Zn rooted in a different source from those elements mentioned above.2)The contents of Cd,Cr,Cu,Pb,and Zn in all vegetable samples were higher than the environmental quality standard for vegetable,and the exceed standard of Cr was 16.56,which showed the pollution of Cr in vegetable samples was the most serious;Moreover,the pollution of Cd,Cu,Pb,and Zn reached a serious grade.The pollution index were calculated by utilizing single factor pollution index and synthesizing pollution index,with the GradeⅡof soil environment quality as its evaluative criterion.The results showed that the single pollution index of Cd reached severe pollution levels,and the other heavy metals were in secure range.While synthesizing pollution index was 3.423,which reached severe pollution level.With national standard limits(GB 184061-2001)as its evaluative criterion,the single factor pollution index of heavy metals Cd,Cr,Pb,and Zn in vegetable samples reached severe pollution levels,and only Cu was mild pollution level;while synthesizing pollution index was 12.43,that it reached very serious pollution level.