光散射技术在土壤胶体颗粒相互作用研究中的应用

APPLICATION OF LIGHT SCATTERING TECHNOLOGY IN STUDY ON INTERACTIONS BETWEEN SOIL COLLOIDAL PARTICLES IN SUSPENSION

由于测试手段的限制,目前对土壤中粒径为0·001～1μm的"超微粒子"之间相互作用的微观效应研究还未引起足够的重视。本文从散射角和悬液颗粒密度两个方面讨论了光散射技术在土壤胶体研究中的应用条件,探讨了土壤胶体颗粒凝聚动力学机制及形成的聚合体结构特征。结果表明:(1)对于本实验所用黄壤悬液,应用光散射准确测定的散射角范围为90°～135°,初始颗粒密度范围为1·90×10-3～0·119gL-1。(2)在自相关曲线平滑地衰减至基线且散射光强保持不变的条件下,可以用光散射技术准确测定土壤胶体颗粒凝聚过程中有效直径、最可几粒径及粒径分布的变化,反映凝聚动力学规律。(3)在298K、90mmolL-1KNO3体系中用动态光散射测得黄壤胶体颗粒凝聚动力学为扩散控制团簇聚集机制,用静态光散射测得形成的聚合体分形维数为1·56±0·02。

The study on microscopic effects of interactions between ＂Ultrafine Particles＂, ranging from 0.001 to 1 μm in diameter in soil has so far not aroused much attention due to limitation in measuring means. Conditions were discussed for application of the laser light scattering technology in the study of interactions between Ultrafine Particles in soil, from the aspects of scattering angle and soil particle density in suspension, and aggregation kinetics of soil colloidal particles and structural characteristics of the aggregates thus formed explored. Results show that （1） for the suspension of yellow earth sample, its proper scattering angle ranges from 90° to 135° and its initial particle concentration in suspension from 1.90×10-3 g L-1to 0.119 g L-1; （2） in the condition that the autocorrelation function curve declines smoothly to the baseline and the scattered light intensity keeps constant with the time going on, the dynamic light scattering technique can be used to determine precisely variation of effective diameter, most probable particle size and particle size distribution during the process of aggregation of soil colloidal particles; and （3） in the system of 298 K in temperature and 90 mmol L-1 KNO3 in electrolyte concentration, the aggregation mechanism of the yellow earth particles in suspension was found to be the diffusion-limited cluster-cluster aggregation （DLCA） process with the dynamic light scattering technique, and its fractal dimension of the aggregates formed therein was determined to be 1.56±0.02 with the static light scattering technique.