Abstract Water flow and solute transport processes are more complex in frozen than in unfrozen soils. The objective of this study was to determine the effects of freezing and thawing on water flow and solute transport in field soils. Experiments were conducted at two field sites each containing soil with a distinct texture (clay loam and sandy loam). Bromide (Br−) was used as a tracer, and soil water content and tracer concentrations were measured at different depths and times. A mass balance method was proposed to estimate mean values of water and solute fluxes (apparent soil water and Br− fluxes) in frozen, transition, and unfrozen zones during a freezing period and conduction and thawed zones during a thawing period. During freezing, soil water content significantly changed below and above the freezing front. Because of the presence of solute, relatively high liquid water content was found at soil temperature below zero. Soil water fluxes were mainly affected by the phase changes during freezing and thawing periods in the clay loam soil and by changes in the hydraulic properties related to liquid water content in the sandy soil. The contribution of water flux to the change of liquid water was much larger in the frozen zones than in the transition zones. During freezing, Br− ions excluded from ice and the different directions of dispersion and convection fluxes resulted in increases and then decreases of the apparent Br− concentration to mean measured Br concentration ratios. During thawing, the movement of liquid water and the superposition of convection and dispersion fluxes resulted in Br− concentration peaks and higher variation of the ratios. The water flow process was less synchronous with the solute transport process in unfrozen soils than in frozen soils.

中文翻译：

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经受冻融的土壤中的水和溶质通量

摘要 与未冻土相比，冻土中的水流和溶质运移过程更为复杂。本研究的目的是确定冻融对田间土壤中水流和溶质迁移的影响。实验在两个田间地点进行，每个地点都含有不同质地的土壤（粘土和砂壤土）。溴化物（Br-）用作示踪剂，在不同深度和时间测量土壤含水量和示踪剂浓度。提出了一种质量平衡方法来估计冻结期间冻结、过渡和未冻结区以及解冻期间传导和解冻区的水和溶质通量（表观土壤水和 Br-通量）的平均值。在冻结期间，土壤含水量在冻结前沿以下和以上发生了显着变化。由于溶质的存在，在低于零的土壤温度下发现了相对较高的液态水含量。土壤水通量主要受粘壤土冻融期相变的影响，以及与沙土中液态水含量相关的水力性质变化的影响。冻结带中水通量对液态水变化的贡献远大于过渡带。在冷冻过程中，Br-离子从冰中排除，不同的分散方向和对流通量导致表观 Br-浓度与平均测量 Br 浓度比的增加和减少。在解冻过程中，液态水的运动以及对流和弥散通量的叠加导致 Br− 浓度峰值和比率的更大变化。