中文摘要：

研究了外源钍在土壤上的吸附行为并评估其对土壤的污染风险.通过静态吸附解吸实验考察土壤样品对不同量外源钍的吸附容量、吸附平衡时间、分配系数和解吸能力.土壤样品对外源钍有很强的吸附能力,在吸附平衡时吸附百分比均大于92%,而解吸率均小于5%;钍在土壤溶液中分配系数最高可达104以上;吸附容量和平衡时间与土壤性质有关.吸附实验结果表明,可用Freundlich吸附等温式和Elovich方程分别描述土壤样品对钍吸附的热力学行为（r≥0.916 7）和动力学过程（R2≥0.898 0）.较佳的拟合结果表明,土壤样品对外源钍的吸附是非线性物理化学吸附,吸附反应速率受钍在土壤表面和矿物内层扩散影响.采用形态连续萃取法分析外源钍在土壤上吸附后的赋存形态.由钍形态萃取结果,少量外源钍（10^-7～10^-6mol·L^-1）进入土壤后主要以不稳定非残留态存在,其含量在58%以上;随着外源钍量增加,钍非残留态量增加,同时更多外源钍迁移到稳定残留态.

英文摘要：

The adsorption behavior of exogenous thorium on soil was studied to evaluate the contaminated risk on soil.The adsorption capacity,equilibrium time,distribution coefficient and desorption ability were investigated by the experiments of static adsorption.The strong adsorption ability of exogenous thorium on soil samples was observed by high adsorption ratio（〉92%） and low desorption ratio（〈5%） in equilibrium,and the biggest distribution coefficient was over 104.The adsorption capacity and equilibrium time were related to soil properties.According to the results of adsorption,Freundlich equation（r≥0.9167） and Elovich equation（R^2≥0.8980） were primely fit for describing the thermodynamics and kinetics of the adsorption of exogenous thorium on soil samples,respectively,which indicated that the adsorption was belonged to the nonlinear adsorption,and was affected by the diffusion of thorium on soil surface and in mineral interbed.Sequential extraction procedure was employed to evaluate the bound fractions of exogenous thorium adsorbed on soil samples.Based on the extracted results of thorium fractions,exogenous thorium was presented in the labile nonresidual fractions（over 58%） at the low initial concentration（10^-7-10^-6mol·L^-1）,and nonresidual fractions enhanced with the increase of the initial amount,meanwhile more exogenous throium was transferred to the stable residual fractions.