棕壤及其各粒级微团聚体对Cd^(2+)的吸附解吸特性

Characteristics of adsorption-desorption of Cd^(2+) by brown earth and microaggregates extracted from it

采用平衡液吸附法和NH4AC、EDTA溶液解吸法,研究了原土及其各粒级微团聚体组分(<10μm,10～50μm,50～250μm)对Cd2+的吸附解吸特征,为寻求有效控制土壤中Cd的环境行为的对策措施提供理论支撑。研究结果表明,各粒级微团聚体组分对Cd2+的吸附能力随粒级的减小而增强,且都强于原土。原土及其各粒级微团聚体吸附Cd2+的机制及稳定性显著不同:Cd2+的络合及专性吸附比例均以小粒级(<10μm)微团聚体相对较大,对Cd2+的固定能力较强;其次为10～50μm粒级微团聚体和原土;大粒级(50～250μm)微团聚体相对较差。分析表明,原土及其不同粒级微团聚体对Cd2+的吸附能力及稳定性的差异,与其不同的比表面积和主要胶体物质(粘粒、有机质,游离氧化铁)的相对含量及组成有关。

In order to provide scientific basis for effectively controlling Cd environmental behavior in soils, the characteristics of adsorption-desorption of Cd2~ by ultrasonic dispersion and bulk brown earth sample （BS） and several different particle size （〈10~tm, 10-50~tm and 50-250~tm） microaggregate fractions （MA） extracted from it were investigated using the methods of equilibrium adsorption and desorption by NH4AC and EDTA solution respectively in this study. The results show that the adsorption capacities of Cd2＋ by the three studied micro aggregate fractions follow the order of 〈10μm MA, 〉 10-50ktm MA, 〉 50-250μm MA, all being greater than that by BS. There were significant differences in the adsorption mechanism and stability of Cd2＋ among tested bulk soil and its micro aggregate fractions. The proportion of specific and chelate adsorptions of Cd2＋ with higher stability at the total adsorption were relatively high on 〈10μm MA, followed by on 10-50pm MA and on BS, relatively low on 50-250μm MA. According to our analysis, adsorption capacity and mechanism of Cd2＋by bulk soil and its micro aggregate fractions were closely related to their specific surface area and the relative contents and compositions of the main colloid matters （clay, organic matter and free iron oxide）.