Distribution and risk evaluation of heavy metal in the soil of typical grassed swale

The concentration and distribution of Pb, Zn, Cu and Cr in the surface soil of three grassed swales located in the city of Beijing, Jiaxing and Shenzhen were studied in this paper. Evaluations on the risk of heavy metals were conducted based on the second level limit of soil environmental quality standard, using different indexes (i.e., single item, comprehensive items and potential ecological risk indexes). Results show that the concentration of Pb, Zn, Cu and Cr in all the soil samples is within the limit of second level of soil environmental quality standard of China, except the soil samples of the grassed swale from Shenzhen city. The result also shows that the concentration of the four kinds of heavy metals in the surface soil of grassed swales is linearly correlated with the depth of soil sampling points. In summary, ecological risk of heavy metals in the three grassed swales is slight.