老工业搬迁区土壤重金属污染特征及潜在生态风险—以沈阳铁西老工业区为例

Characters and Potential Ecological Risks of Heavy Metals in Soil of Chinese Brownfield Redevelopment Site—Case of Tiexi Old Industrial Area, Shenyang City

老工业区搬迁区土壤重金属污染及其潜在生态风险是环境领域的重要前沿问题。本研究以沈阳市土壤元素背景值和《场地环境评价导则》中居住用地标准作为参比值,对沈阳市铁西老工业搬迁区表层(0~20 cm)土壤中8种重金属Cu、Cd、Pb、Zn、As、Hg、Ni和Cr的含量及富集情况进行调查,探讨了城市老工业搬迁区土壤重金属的富集系数及超标率,并结合Müller地累积指数法和Hǎkanson潜在生态风险指数法对污染状况进行潜在生态风险评估。结果表明,与沈阳市土壤背景值相比,铁西老工业搬迁区土壤重金属累积效应显著,除As和Cr外,其它重金属平均含量均超过其背景值,重金属的富集顺序为Cd >Cu >Zn >Pb >Hg >Ni;部分采样点土壤中As含量超过《场地环境质量导则》中限制,是主要的场地修复金属类型;不同功能各种重金属的平均含量均高于其背景值,其中仅以绿地重金属累积最少,工业区、商住区和交通区累积较为严重,工业活动和交通运输已成为影响研究区土壤环境质量的主要因素;研究区土壤具有极强的重金属污染潜在生态危害,其中Cd为极强潜在生态危害,Hg为强潜在生态危害。综上所述,铁西老工业搬迁区土壤重金属复合积累显著,Cd,Hg和As将是该区域土壤重金属修复的重点污染物。

Research about heavy metal soil pollution and its potential ecological risk in brownfiled redevelopment sites is an important frontier issue in environmental fields. Concentrations and accumulation of heavy metals (Cu, Cd, Pb, Zn, Hg, As, Ni and Cr) in surface soil (0 - 20 cm) were collected from an area of about29 km2 inthe Tiexi Old Industrial Area of Shenyang City and analyzed over 71 soil samples. The reference value of the Site Environmental Evaluation Guideline and the environmental background values of Shenyang city were used to analyze the coefficient and rates beyond the soil standard then the Müller land accumulation index and Hǎkanson potential ecological risk index methods were applied to assess the ecological risk of the studied brownfields. The results showed that whilst the average concentrations for As and Cr were not anomalous from background values, the average concentrations of Cu, Cd, Pb, Zn, Hg and Ni in the soil were higher than their background values. This indicates obvious accumulation effects and the accumulated order for these metals was Cd >Cu >Zn >Pb >Hg >Ni. The concentrations of some As samples exceeded the threshold value of the guideline. Moreover, the heavy metal average concentrations in different functional zones were significantly over the background values, especially in industrial, business and residential and traffic zones. It was deemed that industrial activities and transportation have been the main factors that influenced the soil quality in the case study area. According to the potential ecological risk assessment of heavy metal soil pollution, the case study area owned extremely strong ecological harm, in which Cd especially showed extremely strong ecological risk. As well as this, Hg indicated strong risk, and other metals for slight risk. In summary, the soil of the Tiexi Brownfield Redevelopment Site was polluted by mixed heavy metals, especially by Cd, Hg and As. These metals should therefore be the most important pollutants to be considered to be remediated.