Heavy metal contents and evaluation of farmland soil and wheat in typical area of Jiangsu Province
江苏省典型区农田土壤及小麦中重金属含量与评价

The farmland soil was the most main place of the agricultural production,and the quality of soil was the main determinant for the quality and safety of agricultural products,thus it was important to make the quality evaluation of farmland soil before the start of agriculture production.In order to investigate the pollution situation of heavy metals in farmland soil and wheat plants in a seismic belt of typical area in Jiangsu Province,the wheat and the soil of cultivation layer were collected from representative farmlands at harvest.The contents and pollution degree of Cu,Pb,Cd,Ni,Cr,Hg,As,and Zn were analyzed and evaluated.The results showed that the contents of Cd,Zn,and Pb in all soil samples were higher than the background values of Jiangsu soil,and the contents of Cr in 25.64% soil samples,Cu in 97.44% soil samples,Ni in 92.31% soil samples,and As in 92.31% soil samples exceeded the background values of Jiangsu soil,while the content of Hg in all soil samples was under the background value of Jiangsu soil.Compared with the GradeⅡof environmental quality standard for soil(GB 15618—1995),among the elements tested,only the content of Cd in all of the samples exceeded the standard,while all the others were under the standard.Correlation analysis indicated that several heavy metal elements including Cd,Cu,Cr,Ni,Pb,Zn and As in soil had a greater possibility to have come from the same source,however,Hg rooted in a different source from those elements mentioned above.According to the standards on Foods and Products(NY861—2004),the proportion of wheat grain samples exceeding the standards were 100%,58.97%,33.33%,10.26%,and 2.56% for Pb,Cr,Hg,Ni,and As,respectively,while Cu,Zn and Cd in samples did not exceed the standard,it was demonstrated that the element of Pb was the most serious contaminant in wheat grains.The contents of heavy metal in wheat grain were influenced by the soil heavy metal concentration and other physical and chemical properties of soil as well.It was difficult to assess the pollution situation of heavy metal in soil comprehensively using a single evaluate method.Therefore,in this study,the pollution situation of heavy metals in sampled farmland soil was evaluated against references of national standard limits and background values of Jiangsu province soil through single factor pollution index,synthesizing pollution index and Hakanson′ potential ecological evaluation index respectively.The single pollution evaluation result showed that Cd reached severe pollution levels while the other heavy metals were in the security range.Moderate pollution occured when the method of synthesizing pollution index was used.From the potential ecological evaluation index,we found strong ecological harm in the investigated region with Cd as the main pollution factor.