Spatial and temporal changes of soil heavy metal concentrations in vegetable cultivation land

The great changes have occurred in soil microelement concentration of vegetable land at Yixing region of China, constituting major objective for present study. The concentration data of Hg, Cu, Zn, Cr and Pb in soil profile were collected through field survey and laboratory tests. Based on statistical analysis, the authors found an increasing tendency of concentration of Hg, Cu, Zn, Cr and Pb in vegetable soil with planting time. In 0～60 cm soil profile, the concentrations of Hg and Cu exceeded the reference value of soil microelement concentration for natural background recommended by Chinese Environment Bureau. while the concentration of Cr did not exceed the natural background value; In 0～60 cm soil profile, the concentration of Pb in 20 yr and 45 yr vegetable land exceeded the natural background value. Moreover, the change rates of soil microelement concentration presented in this paper is a good index to express the changes of microelement concentration.