Abstract:

With the urban soil of plain area of Baoding city as a target, this essay evaluates the environmental quality of soil heavy metals and pollution characteristics by adopting the single factor index method and Nemerow comprehensive index method. Besides, the potential ecological hazard index suggested by Hakanson is used to assess the ecological hazard of heavy metal in urban soil. The results show that the elements, according to the pollution degree of heavy metal, are followed by the order of Cd＞Zn＞Hg＞Cu＞Pb＞Cr＞Ni＞As. Most importantly, Cr，Pb，Ni，As and most of Hg and Cu are in a clean and safe condition, only to find 0.15% of Ni and 0.40% of Cu in an alert state. However, Cd, Zn are all in the pollution state, especially the pollution of Cd represents the largest polluted area, reaching 0.22%. On the whole, Integrated Pollution Assessment showed the soil environment is good, in which clean, safe, alert, contaminated soil area ratio is 94.39%，5.00%，0.50%，0.11% respectively; and alert and contaminated soil area accounts for 0.61%. Its formation may be related to industrial production and human activities. In the heavy metal elements, resulting in potential ecological hazard of heavy metals is mainly Hg, which have reached to moderate potential ecological hazard level, the remaining heavy metals are all mild potential ecological hazard. Considering synthetically the potential ecological hazard of heavy metals, we found that the percentage of small, medium, high and strong ecological hazard is respectively 93.71%，4.71%，1.29%，0.29%. Therefore, the general performance is the small potential ecological hazard.

Key words: soil, heavy metal contamination, potential ecological hazard, assessment, Baoding city