摘要
目前,用于模拟土壤中溶质运移过程的两区模型(TRM)的研究均集中在实验室的短土柱上,涉及的尺度较小。本研究分别应用两区模型(TRM)、对流-弥散方程(CDE)和分数微分对流-弥散方程(FADE)对1 250 cm长一维非均质土柱中NaCl的运移过程进行模拟,并分析了TRM模型参数的变化特征。结果表明:实验土柱中存在一定的不动水体,与CDE和FADE相比,TRM能更好地描述土柱中不同位置处溶质穿透曲线的提前穿透和拖尾特征,表明TRM对较大尺度条件下非均质土壤中溶质运移的模拟具有更高的精度;应用TRM研究长土柱中溶质的运移问题依然存在弥散系数的尺度效应问题,但TRM的弥散尺度效应小于CDE;TRM中的可动水体含量可以由土壤的有效孔隙率与总孔隙率的比值来确定;而质量交换系数则与对流时间(x/vm)之间存在幂函数的相关关系。
At present, most of studies about the two-region model （TRM） are all focused on modeling solute transport in laboratory short soil column at small scale. The objective of this study was to investigate the validity and parameters of the two- region model （TRM） describing solute transport across a long range of travel distances in heterogeneous soil. We used the TRM, the convection-dispersion equation （CDE） and the fractional advection-dispersion equation （FADE） to characterize the solute transport process in a 1 250-cm long one-dimensional heterogeneous soil column. Comparing to CDE and FADE, the breakthrough curves （BTCs） at different travel distances can be better fitted by using TRM, and TRM is better to capture the full evolution of the BTCs, especially for the early and long tailing part. It implies that TRM is a highly effective approach to describe the evolution of solute transport at relatively large-scale domain in heterogeneous soil. We found that TRM had similar scale-depen- dent dispersion as CDE. However, the dispersion coefficient of TRM was less scale-dependent than that of CDE. It was also found that the mass transfer coefficient of TRM decreased with the advection time in a power law function indicating the presence of multiple timescales of solute mass transfer between immobile and mobile regions, and the mobile water fraction of TRM can be determined with the ratio of effective porosity and total porosity of soil.
出处
《土壤学报》
CAS
CSCD
北大核心
2008年第3期398-404,共7页
Acta Pedologica Sinica
基金
国家重点基础研究发展规划项目(2006CB403406)
教育部长江学者创新团队发展计划(IRT0657)
教育部“新世纪优秀人才支持计划”(NCET-04-0127)资助
关键词
溶质运移
蚱均质土壤
两区模型
大尺度
不动水体
数值模拟
Solute transport
Heterogeneous soil
Two-region model
Large scale
hnmobile water
Numerical simulation
