酸性土壤中Cd^(2+)的吸附与运移特性  

CHARACTERISTICS OF ADSORPTION AND TRANSPORT OF Cd^(2+) IN ACIDIC SOILS

作　　者：王代长[1] 蒋新[2] 贺纪正[3] 卞永荣[2] 郜红建[4] 

机构地区：[1]河南农业大学资源与环境学院,郑州450002 [2]中国科学院南京土壤研究所,南京210008 [3]中国科学院生态环境研究中心,北京100085 [4]安徽农业大学资源与环境学院,合肥230036

出　　处：《环境化学》2007年第3期307-313,共7页Environmental Chemistry

基　　金：国家杰出青年科学基金(40325001);中国科学院知识创新领域前沿项目(ISSASIP0202);河南农业大学创新基金(2006-CX-017).

摘　　要：采用平衡吸附和室内土柱淋溶实验研究Cd2+在酸性土壤中的吸附和运移规律.结果表明:红壤和砖红壤中Cd2+的吸附,在其低浓度范围内符合线性等温方程,Cd2+在砖红壤上的分配系数是红壤上的8倍,能较好地用一级动力学方程的两点和一点模型拟合Cd2+的吸附.红壤快反应的比例约为50%—60%,砖红壤快反应的比例约为90%—95%.采用两点位非平衡模型,红壤β值范围为0.50—0.70,f值的范围是0.40—0.60,仅有40%—60%的吸附点位是瞬间完成,还有一部分吸附点位受速率限制,用非平衡两点模型比用平衡模型能更好地描述Cd2+的运移规律;而砖红壤β值在0.93—0.99,f>0.92,有大于90%的吸附点位是瞬间完成,不到10%受速率限制,很容易达到局部平衡,运用平衡模型可能更适合,这与动力学方程的结果基本一致.The characteristics of adsorption and transport of Cd^2＋ were investigated in red soil and in latosol by using batch and column-leaching methods. The results showed that there were much different adsorption and transport behaviors of Cd^2＋ in both acidic soils. The adsorption of Cd^2＋ by using batch method was well described by the linear isotherm equation in the range of its low concentrations. The partitioning coefficient of Cd^2＋ in latosol, Kd was about 8 times as high as that in red soil. Accumulative amounts of Cd^2＋ adsorption in the column-leaching method could be well fitted by two-site as well as one-site models based on first order kinetic equation. The kinetics of Cd^2＋ adsorption indicated that the adsorption reaction could be divided into fast and slow reactive steps. The fast and slow reactive steps in red soil had almost the same contribution to Cd^2＋ adsorption, whereas the fast adsorption reaction in latosol was dominant. According to two-site nonequilibrium model, two important parameters,β and f, could be used for evaluating local equilibrium and for describing the fraction of instantaneous adsorption, respectively. β and fvalues were 0. 50-0. 70 and 0.40-0. 60 for red soil, respectively; 0. 93-0. 99 and 〉 0. 92 for latosol, respectively; which suggested that in red soil about 50% adsorption sites were instantaneous and the other 50% rate-limited, but in latosol 〉 90% adsorption sites were instantaneous and less than 10% adsorption sites rate-limited. A conclusion could be drawn from the results above that equilibrium models could give an apparently good fit to the observed data of Cd^2＋ transport in latosol, whereas non equilibrium model could be well used to describe Cd^2＋ transport in red soil, which was supported by the results of Cd^2＋ adsorption kinetics.

关 键 词：镉 吸附 土壤 CXTFIT2.0模型 

分 类 号：X131.3[环境科学与工程—环境科学]