不同调控措施对冻融土壤渗透性与水盐再分布的影响

Effects of Different Control Measures on Soil Permeability and Water-Salt Redistribution in Freeze-thaw Soil

摘要:

开展室内冻融循环试验，设置不同土壤初始含水率（15%、20%、25%）、不同含盐量（原始土壤、施加0.2% NaHCO3）、不同生物炭粒径（0~0.5mm，S处理；0.5~2mm，L处理）与未处理组（CK），分析冻融循环过程中不同调控措施下土壤孔隙结构变化对土壤渗透性与水盐再分布的影响，并定量表征土壤水盐运移过程。结果表明：冻融作用促使土壤孔隙扩张，骨料破碎，导致土壤饱和导水率（ks）上升、冻土饱和导水率（kfs）下降。且土壤初始水盐含量提升均会增加冻融作用对土壤结构的破坏，增加土壤孔隙扩张幅度与冻融循环结束后ks与kfs变化幅度，并加剧冻融期土壤水盐上迁比例。施用生物炭可降低冻融期土壤孔隙扩张幅度并提高土壤团聚体稳定性。与CK相比，各含水率及各含盐量S、L处理分别使冻融后ks平均降低48.35%、37.69%，kfs下降幅度平均降低55.44%、78.55%。同时，生物炭处理可降低表层土壤（10cm处）含水率与电导率上升幅度。土壤大孔隙占比与小孔隙占比分别为ks和kfs的关键驱动因子。本研究表明施加0.5~2mm生物炭对冻融条件下土壤渗透性能及水盐再分布状况的调控效果最佳。研究结果可为冻融土壤水盐迁移理论研究体系提供理论依据和技术支撑。

Abstract:

Setting up an indoor freeze-thaw cycle experiment, with different initial soil water contents (15%, 20%, 25%), different salt contents (original soil, 0.2% NaHCO3), different biochar particle sizes (0~0.5mm, S treatment; 0.5~2mm, L treatment) and the untreated group (CK). The effects of soil pore structure changes on soil permeability and water and salt redistribution under different regulatory measures during freeze-thaw cycle were analyzed. The results showed that freeze-thaw induced soil pore expansion, aggregate fragmentation, soil saturated water conductivity (ks) increased, frozen soil saturated water conductivity (kfs) decreased. In addition, the increase of initial soil water and salt content would increase the damage of soil structure by freeze-thaw action, increase the expansion of soil pores and the change amplitude of ks and kfs after the freeze-thaw cycle, and aggravate the proportion of soil water and salt upward migration during freeze-thaw period. The application of biochar can reduce the expansion of soil pores and improve the stability of soil aggregates during freeze-thaw period. Compared with CK, the ks was decreased by 48.35% and 37.69% on average under S and L treatment, respectively, and the kfs was decreased by 55.44% and 78.55% on average under S and L treatment, respectively. At the same time, biochar treatment can reduce the moisture content of the upper soil (10cm) and increase electric conductivity value. The proportion of large pores and small pores in soil were the key driving factors of ks and kfs, respectively. It was showed that the application of 0.5~2mm biochar had the best effect on soil permeability and water and salt redistribution under freeze-thaw conditions. The research results can provide theoretical basis and technical support for the theoretical research system of water and salt transport in freeze-thaw soil.