黄石市典型农业土壤中重金属污染水平及评价

Concentration and Assessment of Heavy Metals in the Typical Agricultural Soil from Huangshi City

以黄石市阳新县某大型农场作为研究区,于2012年2月采集8个代表性表层（0~20 cm）土壤样品,采用火焰-原子吸收分光光度法分析了各重金属元素（Cu、Pb、Zn、Cd、Mn、Co）的总量及BCR连续提取法提取土壤中重金属的弱酸态、可还原态、可氧化态和残渣态含量。结果显示,Cu、Pb、Zn、Cd、Mn和Co总量的平均值分别为122.10、141.29、335.53、2.18、2 606.58和128.27 mg/kg,其中Cd超过了土壤环境三级标准限值,Mn具有最强的变异系数,受到外来污染因素的影响最大。通过地积累指数法和潜在生态危害法表明,6种重金属累积程度由高到低依次为Cd〉Co〉Cu〉Pb〉Zn〉Mn,且Cd、Mn为主要生态风险因子。同时由形态分析可知,Cu、Pb、Cd、Zn、Mn和Co的化学形态分布均以残渣态为主,说明该农场土壤中重金属元素比较稳定,不易迁移转化,对生物的毒性较小。

Eight agricultural surface soil samples（0 ~20 cm） were collected from a typical farm in Yangxin County of Huangshi City as the study area in February 2012. Total contents of heavy metals such as Cu,Pb,Zn,Cd,Mn and Co as well as BCR method for extraction of heavy metal in the state of acid extractable,reducible,oxidizable and residual were analyzed by using flame atomic absorption spectrometer. Results showed that total concentration of Cu,Pb,Zn,Cd,Mn and Co was 122.10 mg/kg,141.29 mg/kg,335.53 mg/kg,2.18 mg/kg,2 606.58 mg/kg and 128.27 mg/kg respectively,Cd was above the Grade III of soil environment limit. The coefficient of variation of Mn is the strongest,affected by external pollution factors greatest. The index of geo-accumulation（Igeo）is used to evaluate heavy metal pollution in soil from the farm.The level of heavy metal accumulation was in the order as CdCoCuPbZnMn,and potential ecological risk coefficient indicated that Cd and Mn were the main factors. Through the BCR（European Communities Bureau of Reference）sequential extraction procedure analysis,major fraction of heavy metals in soil was the residual. The results indicated that heavy metal elements in the farm soil were relatively stable,and difficult to migrate into organism.