Research on heavy metal's characteristics in the soil of vegetable farms in Chongqing City

The contents of heavy metals of Cr，Ni，Cu，Zn，As and Pb in 0～20cm and 20～40cm layers in soils have no obvious differences in the vegetable farms，and the contents of Cd and Hg have obvious differences.The differences of average contents and the variable coefficient of the heavy metals in different types of soil are smaller.The contents of heavy metals of Ni，Cu，Zn，As and Pb and the cation exchange capacity in the outskirts of a town and the areas of the factories and mines and the general countryside have no remarkable differences.The heavy metals in different types of soil and different regions have more coherency，and the Cu，Ni and Cr of heavy metals have more associated relation.The pollution of Cd of vegetable farm is bigger in Chongqing.