旱区盐碱土壤优先流区与基质流区水盐分布和淋洗规律研究

Water and Salt Transport and Salt Leaching Patterns in Preferential Flow and Matrix Flow Zones of Saline-alkaline Soils in Arid Regions

摘要:

水分流经土壤大孔隙携带溶质运移进而影响土壤优先流区与基质流区的水盐运移特征。为探讨旱区盐碱地土壤优先流区与基质流区水盐分布及淋洗规律,本文采用原状土柱染色淋溶试验并结合结构方程模型,分析了盐荒地与葵花地土壤剖面水文连通性、淋溶特征与水盐含量特征及其作用关系。结果表明,葵花地土壤优先流发育程度与剖面水文连通性较盐荒地强,前者土壤垂直和水平剖面染色面积比为后者的1.05倍和1.56倍,染色面积比变异系数为后者的55%,前者染色通道细碎,后者染色集中于上层且呈狭长条带状。与盐荒地相比,葵花地累积出流量增加8.76%,开始出流时间提前68.32%,出流历时缩短88.95%,累积淋盐量和淋溶液含盐量减少83.08%和78.32%。淋溶后优先流区土壤含盐量均值低于基质流区33.38%,发生频率为89.38%。土壤剖面水文连通性直接影响土壤水盐含量和淋溶特征,亦可通过改变淋溶特征间接影响优先流区与基质流区水分分布。研究结果为深入理解盐碱土壤水盐运移机制和改良土壤结构提供了理论支持。

Abstract:

Water flowing through soil macropores transports solutes and thereby influences water and salt migration in preferential flow and matrix flow domains. To investigate the distribution and leaching patterns of water and salt in these two domains in arid saline-alkali soils,undisturbed soil column dye infiltration experiments combined with structural equation modeling were conducted. The relationships among soil profile hydrological connectivity,leaching characteristics,and water-salt contents were analyzed for soils from a barren saline land and a sunflower field. The results showed that preferential flow development and profile hydrological connectivity were stronger in the sunflower-field soil than that in the barren saline soil. The vertical and horizontal stained-area ratios of the sunflower-field soil were 1.05 times and 1.56 times those of the barren saline soil,respectively,while the coefficient of variation of stained-area ratios was only 55% of that of the latter. Stained flow paths in the sunflower-field soil were finer and more fragmented,whereas staining in the barren saline soil was mainly concentrated in the upper layer and exhibited narrow,elongated strip-like patterns. Compared with the barren saline soil,the sunflower-field soil showed an 8.76% increase in cumulative outflow,a 68.32% earlier onset of outflow,and an 88.95% reduction in outflow duration,accompanied by decreases of 83.08% and 78.32% in cumulative salt leaching and leachate salinity,respectively. After leaching,the mean soil salt content in the preferential flow domain was 33.38% lower than that in the matrix flow domain,with an occurrence frequency of 89.38%. Soil profile hydrological connectivity directly affected soil water and salt contents as well as leaching characteristics,and indirectly influenced water distribution between preferential and matrix flow domains by altering leaching behavior. These findings can provide theoretical support for a deeper understanding of water-salt transport mechanisms and for improving soil structure in arid saline-alkali soils.