Solute mass transfer through the macropore-matrix interface during preferential flow in structured soils: model development

本项目的目的是在两个区域模型中发展一个扩展的两区域宏观传质项，用于描述结构性土壤中活性溶质的优先迁移。这一术语应该与大孔-基质界面上局部尺度物理化学性质的毫米尺度空间分布有关。其思想是在宏观尺度模型的动力学传质描述中包括在大孔(例如，生物孔壁、裂隙和涂层土团聚体)的完整表面上观察到的局部非均质吸附位置的放大信息，作为有效的延迟参数。模拟的局部尺度2D和3D传质场景将作为参考。局部尺度的模拟将利用染料染色实验和基于涂层和基质孔结构的X射线CT信息进行校准。然后通过比较不同初始和边界条件以及三种结构性土壤样品的宏观传质速率与局部分布的平均值来评估宏观传质项。最后，将三种土壤的土柱渗流实验结果与一维双渗透模型和改进的传质条件下的模拟结果进行比较，对评价的传质条件进行检验。我们期待着进一步了解土壤结构和优先流之间的关系，以及土壤管理对优先运移过程中溶质，特别是活性溶质运动的影响。

The objective of this project is to develop an extended two-region macroscopic scale mass transfer term in two-domain models for describing preferential transport of reactive solutes in structured soils. This term should be related to mm-scale spatial distributions of local scale physico-chemical properties at the macropore-matrix interface. The idea is to include up-scaled information on locally heterogeneous sorption sites observed at intact surfaces of macropores (e.g., biopore walls, cracks and coated soil aggregates) as effective retardation parameter in the kinetic mass transfer description of the macroscopic scale model. Simulated local scale 2D and 3D mass transfer scenarios will serve as a reference. The local scale simulations will be calibrated using dye staining experiments and X-ray CT-based information on the pore structure of coating and matrix. A macroscopic transfer term will then be evaluated by comparing the averaged locally-distributed with the macroscopic mass transfer rates for various initial and boundary conditions and for samples from three structured soils. The evaluated mass transfer term will finally be tested by comparing soil column percolation experiments for the three soils with simulation results obtained with a 1D dual-permeability model with the improved mass transfer term.We expect further improvement un understanding the relation between soil structure and preferential flow, and of effects soil manangement on the movement of solutes, in particular reactive solutes, during preferential transport.