冻融循环及含水量对盐碱土团聚体水稳性特征的影响

Effects of Freeze-thaw Cycles and Water Content on Water Stability Characteristics of Saline Soil Agglomerates

以北疆耕作层土壤为研究对象,采用室内冻融模拟试验,研究冻融循环过程中土壤含水量、含盐量和冻融循环次数对土壤团聚体水稳定性特征指标(平均质量直径、几何平均直径、分形维数)的影响。结果表明:70%田间持水量时冻融过程可增强团聚体稳定性,含水量过高或过低均破碎团聚体,特别是达到田间持水量时;初始含盐量对团聚体稳定性也有显著影响,随着含盐量的增加土壤团聚体稳定性逐渐降低;随冻融循环次数增加(1次、3次和5次),<0.1 mm的团聚体组成比例显著上升,几何平均直径和平均质量直径降低;在初始含水量较低时,冻融循环对分形维数没有显著影响,随着初始含水量的增加,分形维数最高增加0.88%;土壤的平均质量直径和几何平均直径均与分形维数呈显著负相关。建议在盐碱土冻结前,调节土壤含水量至70%田间持水量,可以保持和改善土壤物理结构。

Using the soil in the cultivated layer of the northern Xinajing as the study object,the indoor freeze-thaw simulation experiments were conducted to investigate the effects of soil water content,salinity and the number of freeze-thaw cycles on the characteristic indexes of water stability of soil aggregates(average mass diameter and fractal dimension)during the freeze-thaw cycle.The results showed that:the freeze-thawing process at 70%field moisture content could enhance the agglomerate stability,and the agglomerates were shattered by too high or too low moisture content,especially when the field moisture content was reached;the initial salinity also had a significant effect on the agglomerate stability,and the stability of soil agglomerates gradually decreased with the increase of salinity;with the increase of the number of freeze-thawing cycles(1,3 and 5),the proportion of agglomerates less than 0.1 mm increased significantly,while the geometric average diameter and average weight diameter decreased;When the initial water content was low,the freeze-thaw cycle had no significant effect on the fractal dimension.With the increase of the initial water content,the fractal dimension increased up to 0.88%.The mean mass diameter and geometric mean diameter of soil were negatively correlated with the fractal dimension.It is suggested that soil moisture content should be adjusted to 70%field capacity before freezing of saline-alkali soil to maintain and improve soil physical structure.