Distribution of Heavy Metals in Urban Soils of Zhengzhou City and Soil Quality Assessment

Zhengzhou is an important city in Chaotu soil area,however,very limited information is available about the heavy metals in urban soil of this city. In this work,soil samples were collected at the depths of 0-5,5-10 and 10-20 cm at 30 sampling sites in urban area of Zhengzhou city and the contents of copper (Cu),zinc (Zn),lead (Pb) and manganese (Mn) were analyzed with atomic absorption spectrometry. The results indicated that,the mean concentrations of Cu,Zn,Pb and Mn in these soil samples were 59.11,91.67,39.63 and 552.7 mg kg-1,respectively. Higher concentrations of Zn were found in early urbanized area,no obvious trend about the other three elements were observed; furthermore,higher concentrations of Zn were found in 0-5 cm layer for most samples; for Cu,Pb and Mn,higher concentrations were often found in samples from areas with shorter urbanized history. Cu had the maximum mean Pollution Index (PI),while Mn had minimum value. Integrated Pollution Index (IPI) ranged between 0.98-2.79,averaged at 1.70. Among all 30 sampling sites,average IPI of the three layers of three sites were 2.0,all with the characterized by heavy traffic. These results suggest that there is low level accumulation of Cu,Zn,Pb and Mn in urban soils of Zhengzhou City,and vehicle is the most important source of heavy metals in high concentration area.