ZHONG Xiao-Lan, ZHOU Sheng-Lu, ZHAO Qi-Guo
In this paper,soil contamination characteristics of 8 heavy metals(Cd,Cr,Cu,Ni,Hg,Pb,Zn and As) in the topsoil(0-20cm) from Taicang City,a typical region of the Yangtze River Delta,were analyzed,and ecological risk of soil heavy metals was evaluated by means of the potential ecological hazards index.Zn and Cu were distributed lognomally,strong in variability,while Cd,Ni,Hg,As,Cr and Pb were distributed nomally,medium in variability. The concentrations of Cu,Hg,Zn,As exceeded their background levels significantly,and As ranked first in contamination index and over limit rate.Except that As increased from the top down,all other soil heavy metals dropped off accordingly in the soil profile.Compound heavy metals contamination of the soil in Taicang was quite severe.The soil ecological hazard of Taicang was moderate,and the risk of well drained soil was higher than that of the sand with ridge.The soil heavy metals contamination was the most serious in the dyeing factories,followed by electric plating factories and breed factories.Hg and Cd brought the dominating potential ecological hazard,while As,Cu,Zn,Cr,Ni and Pb did slight hazard.