酸雨条件下黄壤中镉的模拟解吸动力学研究

The Characteristics of Simulated Desorption Kinetics of Cadmium in Yellow Soil under Acid Rain Condition

设计正交实验,采用动态淋滤试验方法研究了黄壤中的Cd2+在不同模拟酸雨条件下的解吸动力学特征。结果表明,在实验设定的水平范围内,酸雨中各因素对黄壤中镉解吸的影响作用依次为:pH>[SO42-]>[Ca2+]>[SO42-]:[NO3-];多项式方程是拟合Cd2+的解吸动力学过程的最优方程,相关系数R2为0.815～0.980,标准差SE为0.003～0.023;滤出液的pH值及Eh值同淋滤液有差异,且差异大小随淋滤液pH值产生变化,在实验点pH=2.5处,淋滤前后pH和Eh的变化值分别介于4.08～4.30和223～237mV之间,而在pH=3.5处,△pH和△Eh分别介于0.10～0.26和7～15mV之间;镉的解吸量及达平衡的时间除了受酸雨的酸度影响外,还和酸雨中阴阳离子的浓度有关。

In this paper, the desorption kinetics of cadmium behaviors were studied using the flow-eluviations method with orthogonal experiments in yellow soil under different simulated acid rain conditions. The results showed that within the test range, the leaching amount of Cd〉 was affected by the diversification of simulated acid rain＇s factors and generally was in an order with pH 〉[SO4^2-] 〉[Ca^2＋]〉[SO4^2-]：[NO3^-]. Polynomial equation was the optimal model to describe the desorption kinetics of Cd^2＋, with correlation coefficient R^2 in the range of 0.815-0.980 and standard deviation from 0.003 to 0.023. Flowing through the experimental tube, the pH and Eh value of filtrate were changed with the leachete. The difference of pH and Eh was dependents on the primary pH of eluviating liquid. At pH=2.5 experimental point, the ApH and AEh were 4.08-4.30 and 223-237 mV respectively, whereas those for pH=3.5 experimental point were 0.104 0.26 and 7-15 mV respectively. The amount of desorption and the time reaching equilibrium were depended on the concentration of anion and cation coexisting in the acid rain besides the acidity of simulated acid rain.