镉在东北地区4种土壤中的吸附动力学

吸附是外源重金属进入土壤后首先发生的最重要的过程，直接影响着重金属的生物可利用性。采用间歇法研究了不同重金属镉浓度时，镉在东北地区4种农业土壤黑土、盐碱土、暗棕壤和草甸白浆土上的吸附动力学特征，并采用常用的动力学方程进行拟合。研究结果表明，Cd在东北地区4种土壤上的吸附动力学过程分为两个阶段：开始的快速反应阶段和经过一段时间后的慢速反应阶段，低浓度下Cd达到吸附平衡的时间更短；黑土和盐碱土吸附速率、吸附量都要高于草甸白浆土和暗棕壤，这在初始Cd 1.6 mg L-1时表现的更加明显，这与黑土高有机质含量、盐碱土的粘粒较多、pH高有直接关系。通过非线性拟合的方法获取了适宜描述Cd在东北地区土壤上吸附动力学特征的最优化模型，综合来看，指数方程和指数函数方程比较适宜于描4种土壤对Cd的吸附动力学特征。

Study on Kinetics of Adsorption of Cadmium on four types of soils in Northeast, China

Adsorption is the initial process when the exterior heavy metals enter soil, influencing directly bioavailability of metals in soil. The batch techniques were used to investigate the adsorption kinetics of cadmium (Cd) on four types of soils in Northeast China: phaeozem, saline-alkali soil, meadow albic bleached soil and dark brown forest soil. Sorption data was fitted by numbers of kinetic equations in common use. The result showed that, the process of Cd sorption on four types soils could divided into two phases: the fast phase and slow phase. Compared with high Cd concentration 16 mg L-1, there was lesser time for reaching balance of Cd sorption by soils at low Cd concentration 1.6 mg L-1. The rate and amount of Cd sorption by phaeozem, saline-alkali soil were higher than by meadow albic bleached soil and dark brown forest soil, which was more distinct in lower Cd 1.6 mg L-1. That was due to higher content of organic matter on phaeozem, higher pH value and proportion of clay components on saline-alkali soil. The optimum models were obtained by non-linear fitting to describe the kinetic processes of adsorption of Cd on four types of soils in Northeast, China. According to the results, exponential equation and exponential function equation were more appropriate to fit the kinetic process than other equations.