离子强度和胡敏酸影响下不同土壤胶体稳定性研究

土壤胶体的稳定性对其携带污染物的能力产生重要影响，但离子强度和胡敏酸（HA）对不同土壤胶体稳定性的影响程度尚不明确.本实验通过土壤胶体沉降实验以及DLVO理论研究离子强度、HA对黑钙土、潮土和黄壤3种土壤胶体稳定性的影响.结果表明：即使在高离子强度背景下，黑钙土胶体和黄壤胶体因有机质和黏土矿物（黑钙土胶体：伊/蒙混合层；黄壤胶体：伊利石）较高，表面负电荷多、静电斥力大，故稳定性好；而潮土胶体的稳定性受离子强度影响明显，在低离子强度下，静电斥力占主导，稳定性达到最高.HA通过增加土壤胶体表面的负电荷，提高土壤胶体间静电斥力而增强其稳定性，且HA浓度越高土壤胶体的稳定性越强.不同粒径HA对土壤胶体稳定性的影响受pH值控制，相对于大粒径HA，酸性条件下，小粒径HA （F-HA）自身稳定性更强，同时也会自凝聚形成较大的团聚体来提高土壤胶体的稳定性；中、碱性条件下，F-HA产生的链状凸起结构较小，导致空间弹性斥力和渗透性斥力减弱，进而降低土壤胶体的稳定性.结果为明晰离子强度和HA对不同土壤胶体稳定性产生差异性影响提供数据支撑.

Stability of different types of soil colloids under the influence of ionic strength and humic acid

The stability of soil colloids significantly affects its ability to carry environmental pollutants, but the influence of ionic strength and humic acid (HA) on the stability of different soil colloids is still unknown. In this study, the effects of ionic strength, humic acid concentration and particle size on the stability of colloids in chernozems soil, fluvo-aquic soil and yellow earth soil were studied through sedimentation experiments and DLVO theory analysis. The results showed that, even under high ionic strength, due to the higher contents of organic matter and clays in the colloids of chernozems and yellow soil, the surfaces of soil colloids were more negatively charged than in the fluvo-aquic soil, leading to higher electrostatic repulsion and better stability of colloids in the chernozems and yellow soil. The stability of colloids in the fluvo-aquic soil was significantly affected by ionic strength. At low ionic strength, colloids of fluvo-aquic soil exhibited the highest stability due to the dominance of electrostatic repulsion. HA enhanced the stability of soil colloids by increasing the negative charges on the surface of soil colloids, resulting in increased electrostatic repulsion between soil colloids. And higher HA concentration led to higher stability of soil colloids. The influence of HA particle sizes on the stability of soil colloids was controlled by soil pH. Compared with large HA particles, under acidic conditions, small HA (F-HA) particles were more stable and tended to form larger agglomerates through homoaggregation, leading to elevated stability of soil colloids; Under neutral and alkaline conditions, the size of the chain-shaped convex morphology formed by F-HA was small, which weakened the elastic-steric repulsion and osmotic repulsion, thereby reducing the stability of soil colloids. The findings in this study may provide theoretical support to clarify the differentiate effects of ionic strength and HA on the stability of soil colloids.