An assessment of the heavy metal pollution and potential ecological hazards in urban soil of Tangshan City

Abstract：With the urban soil of Tangshan City as the study target, the authors evaluated 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 was used to assess the ecological hazards of heavy metals in urban soil. All of the heavy metal elements are not in the pollution state, especially all of Hg, Ni, Cr and As are in a clean condition. Most of Pb, Zn and Cu are in a clean condition, with only 7.94% of Pb, 6.35% of Zn and 1.59% of Cu in a safe state. Most of Cd are in a clean and safe condition, with only 1.59% of Cd in an alert state. On the whole, the integrated pollution assessment shows that the soil environment is good, with clean, safe, alert and contaminated soil area possessing 98.41%, 1.59%, 0 % and 0% respectively. As for the heavy metal elements, Hg is mainly responsible for potential ecological hazard, and its content has reached the high potential ecological hazard level; other heavy metals only cause small potential ecological hazards. Considering synthetically the potential ecological hazards of heavy metals, the authors have found that the percentage of small, medium, high and strong ecological hazard is respectively 73.02%, 26.98%, 0% and 0%. Therefore, the general performance is the small potential ecological hazard.