河北中南部平原土壤重金属元素存在形态及生物有效性分析

An analysis of modes of occurrence and biological availability of the heavy metal elements in soil of the central and southern plain in Hebei

本文以河北省中南部平原农田表层土壤为研究对象,对表层土壤中7种重金属元素的形态含量进行了统计和分析,对重金属元素的生物有效性进行了评价,并运用相关分析法,对影响重金属元素生物有效性的因素进行了研究。结果表明,研究区表层土壤7种重金属元素的有效态含量以Cd最高,达36.83%,潜在生态危害性较大;其次为Pb,达13.37%,其中碳酸盐结合态达到12.38%,由于土壤呈中性或偏碱性,Pb元素的迁移能力较弱,其潜在危害性较小;Cu、Hg、Cr、As、Zn重金属元素含量均以稳定态的含量存在,之和均在90%以上,表明其潜在危害性较小;研究区土壤重金属元素的活性系数和迁移系数大小顺序为:Cd>Pb>Hg>Cu>Zn>As>Cr和Cd>Hg>As>Cu>Pb>Zn>Cr,其中Cd的活性系数和迁移系数平均值分别达到0.330和0.160,展现出较强的生物活性、不稳定性和迁移能力,其他重金属元素在土壤中活性系数(Pb除外)和迁移系数均较小,生物活性较弱,在土壤中稳定存在,由土壤中向植物中的迁移能力弱;研究区不同的重金属的生物有效性与其影响因素的关系不尽相同,其主要因素是土壤重金属元素全量,其次为p H、TOC、CEC、粘粒含量等,二者关系复杂。

Based on the study of topsoil of the central and southern plain in Hebei,the authors analyzed the morphology of seven heavy metals in topsoil,evaluated the biological availability of the heavy metal elements,and studied the factors which might affect the biological availability of heavy metal elements by means of correlation analysis. The results show that the content of element-available Cd is 36.83% in topsoil, the highest among all metal elements that have greater potential ecological harmfulness. The content of element- available and carbonate Pb is respectively 13.37% and 12.38%, suggesting smaller harmfulness because of neutral and alkaline soil in the study area. The total values of Cu, Hg, Cr, As, Zn that maintain stable state account for more than90%, implying smaller harmfulness. The activity coefficients and migration coefficients of heavy metal elements in topsoil in the study area are respectively arranged in order of Cd〉Pb〉Hg〉Cu〉Zn〉As〉Cr和Cd〉Hg〉As〉Cu〉Pb〉Zn〉Cr, with the average of the Cd achieving respectively 0.330 and 0.160, implying a strong biological activity, instability and migration capability.Other soil heavy metals show smaller activity coefficients（except Pb） and migration coefficients,indicating that their biological activities are weak and it is difficult for them to transfer from soil to plants. The relationships between biological effectiveness and influential factors of various heavy metals are not the same; nevertheless, the dominant factor is the total amount of soil heavy metal elements, followed by p H, TOC, CEC, clay content and other factors. There exist complicated relations between them.