河北保定市安新—清苑县土壤重金属形态分布及风险评估

Fraction distribution and risk assessment of soil heavy metals in Anxin—Qingyuan County in Baoding of Hebei

为揭示河北保定市安新—清苑县土壤重金属(Cd、Cu、Pb、Zn)的形态及潜在生态风险,采集37个土样,测定其重金属的含量与赋存形态。综合考虑土壤重金属的总量及形态,进行风险评估。将直接可利用态Cbio、潜在可利用态C_(Pbio)和不可利用态CNbio与Hakanson潜在生态危害指数法相结合,赋予不同权重因子,构建土壤重金属风险的综合评价模型。结果表明:(1)4种重金属Cbio比例依次为Cd>Pb>Cu>Zn,C_(Pbio)比例依次为Pb>Cu>Zn>Cd,CNbio比例依次为Zn>Cu>Pb>Cd;(2)Hakanson潜在生态危害指数法和赋存形态的综合潜在生态危害指数法得到的生态风险指数平均值大小顺序相同,均为Cd>Pb>Cu>Zn。由风险分布图可以更直观地看到两者结果分布的相似性。由于赋存形态的潜在生态危害指数法同时考虑了重金属的全量和不同赋存形态的生物有效性的差异,相对于单方面考虑重金属全量的评价方法更加合理。

In order to reveal chemical forms and its potential ecological risk of soil heavy metals（ Cd,Cu,Pb,Zn） in Anxin-Qingyuan County in Baoding of Hebei Province,37 soil samples were collected to determine total contents and chemical speciation of heavy metals. Potential ecological risk assessment was performed based on the total amount and different forms of heavy metal in soil. The bioavailability of heavy metals,including the directly available state Cbio,the potentially available state C_（Pbio）and the non-use state CNbio,were combined with the Hakanson potential ecological risk index method to construct a comprehensive evaluation of soil heavy metal pollution risk model using different weight factors. The results show that Cbioratio of heavy metals followed the order： Cd Pb Cu Zn,C_（Pbio）ratio： Pb Cu Zn Cd,and CNbioratio： Zn Cu Pb Cd. The average values of the ecological risk index obtained by the bioavailability metal-form method were identical to those of the Hakanson method. Risk distribution map directly shows the similarity of the distribution of the evaluation results. Since the chemical speciation of the potential ecological risk index takes into account the total amount of heavy metals and the bioavailability of chemical speciation,it would be more reasonable compared to those with the Hakanson method,which only considers the total amount of heavy metals.