镉在土壤中吸附的能量特征和解吸滞后效应研究

目的]为了研究吸附-解吸反应对重金属生物有效性的影响.方法]以我国12种典型农田土壤为试验材料,采用批次平衡法,研究重金属镉在农田土壤中吸附的能量特征和解吸滞后效应.结果]供试土壤对镉的吸附均为自发反应,温度的升高有利于促进土壤对镉的吸附.土壤镉吸附的吉布斯自由能变（△G°）可以用来预测土壤镉的解吸能力.土壤对重金属镉吸附的主要机理为化学键力.镉在土壤中的解吸过程存在滞后现象,随着镉平衡液浓度的增加,各供试土壤中镉解吸的滞后效应增强.供试土壤pH和碳酸钙含量越高,滞后系数越大.这可能与土壤pH和碳酸钙含量较高时,镉在土壤中形成难解吸的内圈配合物和碳酸镉沉淀有关.结论]该研究结果可以为防治土壤重金属污染和修复研究提供参考依据.

Study on Energy Characteristics and Hysteresis Effect of Cadmium in Soils

Objective] The research aimed to study the effects of adsorption and desorption on the bioavailability of heavy metals in soil.Method] Batch techniques were used to study the energy characteristics of adsorption and hysteresis effect of desorption of cadmium in 12 typical agricultural soils from China.Result] Adsorption process of cadmium in soils was spontaneous process.With the increasing temperature,it could promote theadsorption of cadmium in soils.The value of Gibbs free energy （△G°） could be used to predict the desorption ability of cadmium in soils.The main mechanism of the cadmium adsorption in soils was the chemical bond force.There was hysteresis effect in the process of cadmium desorption,and with the increase of cadmium concentration in the equilibrium the hysteresis effect was enhanced.When pH and calcium carbonate content were higher,the hysteresis index was greater because of the cadmium forming the inner complexes and cadmium carbonate precipitation in the soils.Conclusion] The study could provide some reference and gist for prevention of heavy metal polluted soils and for remediation of contaminated soils.