表面电荷性质对离子在土壤胶体界面扩散的影响

EFFECT OF SURFACE CHARGE PROPERTIES ON ION DIFFUSION IN SOIL COLLOID INTERFACE

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。

Ion diffusion is an important path of mass transport in nature,controlling movement of nutrients from bulk soil to plant roots as well as fate of potentially harmful salts and toxic compounds.The kinetic method was used in this experiment to determine surface charge properties of soil colloids of neutral purplish soil and latosol and to study K＋,Mg2＋ diffusion in the two types of colloids under the same condition as surface charge properties were determined.And the diffusion flux dependent of time and diffusion coefficient in the two types of colloids（at different of pH electrolyte type and electrolyte concentration） were determined.Results show 1） the total diffusion flux varied in the range of 2.6 ～3.1 mg g-1 in neutral purple soil under different environmental conditions,about 6～10 times higher than what in latosol,being in the range of 0.26 ～0.51 mg g-1;and 2） the diffusion coefficient varied in the range of 1.17×10^-9～1.91×10^-9 cm^2 s^-1 in neutral purple soil under different environmental conditions,and in the range of 0.23×10^-9～0.45×10^-9 cm^2 s^-1 in latosol.Surface charge properties were the dominant factor affecting ion diffusion in charged colloids.