表面电荷性质对离子在土壤胶体界面扩散的影响

采用动力学方法测定了中性紫色土胶体和砖红壤胶体的电荷性质,研究了不同pH、电解质体系、浓度条件下离子在带电土壤胶体中的扩散过程,分析了两种土壤胶体在不同条件下离子扩散通量和扩散系数的特点。结果表明:1)中性紫色土胶体和砖红壤胶体中离子平衡扩散量为2.6～3.1 mg g-1和0.26～0.51 mg g-1,前者的扩散平衡量是后者的6倍～10倍;2)中性紫色土胶体不同温度条件下,离子扩散系数为1.17×10-9～1.91×10-9cm2s-1,砖红壤胶体中在与其对应温度条件下,离子扩散系数为0.23×10-9～0.45×10-9cm2s-1,前者是后者的4倍～5倍。表面电荷性质对离子在带电土壤胶体界面扩散的影响起决定性作用。

Effect of surface charge properties on ion diffusion in soil colloid interface

Ion diffusion is an important style of mass transport in nature, which may control the movement of nutrients from bulk soil to plant roots as well as the fate of potentially harmful salts and toxic compounds. The kinetic method has been used in this experimental study to determine the surface charge properties. We also used the kinetic method to study K+, Mg2+ diffusion in the two type of colloid under the same condition as we determine the surface charge properties. And the diffusion flux dependent of time and diffusion coefficient in two type of colloid (at different of pH electrolyte type and electrolyte concentration) were determined. The results show: 1) the total diffusion flux is 2.6 ~3.1 mg g-1 in neutral purple soil at different environmental conditions, but it is 0.26 ~0.51 mg g-1 in latosol. The total diffusiion flux in neutral purple soil is about 6~10 times higher than latosol; 2) The diffusion coefficients is 1.17×10-9~1.91×10-9 cm2 s-1 in neutral purple soil at different environmental conditions, but it is 0.23×10-9~0.45×10-9 cm2 s-1 in latosol.The surface charge properties were dominant factor of ion diffusion in charged colloid.