Indirect estimation of the Convective Lognormal Transfer function model parameters for describing solute transport in unsaturated and undisturbed soil

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• 作者：Mohammad Hossein Mohammadi^a ; ^{mhmohammadi@hotmail.com} ; ^{mohammadi@znu.ac.ir} ; Marnik Vanclooster^b
• 关键词：BTC ; Break Through Curve ; CLT ; Convective Lognormal Transfer ; HCC ; Hydraulic Conductivity Curve ; SMC ; Soil Moisture Characteristics
• 刊名：Journal of Contaminant Hydrology
• 出版年：2012
• 期刊代码：43_01697722
• 类别：env
• 出版时间：1 May, 2012
• 卷：132
• 期：Complete
• 页码：48-57
• 文件大小：2540 K

摘要

Solute transport in partially saturated soils is largely affected by fluid velocity distribution and pore size distribution within the solute transport domain. Hence, it is possible to describe the solute transport process in terms of the pore size distribution of the soil, and indirectly in terms of the soil hydraulic properties. In this paper, we present a conceptual approach that allows predicting the parameters of the Convective Lognormal Transfer model from knowledge of soil moisture and the Soil Moisture Characteristic (SMC), parameterized by means of the closed-form model of Kosugi (1996). It is assumed that in partially saturated conditions, the air filled pore volume act as an inert solid phase, allowing the use of the Arya et al. (1999) pragmatic approach to estimate solute travel time statistics from the saturation degree and SMC parameters. The approach is evaluated using a set of partially saturated transport experiments as presented by Mohammadi and Vanclooster (2011). Experimental results showed that the mean solute travel time, 渭_t, increases proportionally with the depth (travel distance) and decreases with flow rate. The variance of solute travel time 蟽²_t first decreases with flow rate up to 0.4-0.6 Ks and subsequently increases. For all tested BTCs predicted solute transport with 渭_t estimated from the conceptual model performed much better as compared to predictions with 渭_t and 蟽²_t estimated from calibration of solute transport at shallow soil depths. The use of 渭_t estimated from the conceptual model therefore increases the robustness of the CLT model in predicting solute transport in heterogeneous soils at larger depths. In view of the fact that reasonable indirect estimates of the SMC can be made from basic soil properties using pedotransfer functions, the presented approach may be useful for predicting solute transport at field or watershed scales.