Applicability of boundary conditions for analytical modelling of advection-dispersion transport in low-permeability clay column tests

The column tests on advection-dispersion are commonly used to measure the contaminant transport parameters in soils. The applicability of boundary conditions for analytical modelling of the column tests is under debate. The low-permeability kaolin column tests subjected to different hydraulic heads are conducted at 1g and under centrifuge conditions. The pore-water concentration profiles and the effluent concentration curves in the columns are obtained, and the applicability of boundary conditions for different scenarios is discussed. For the modelling of pore-water concentration profile in the low-permeability soil column, the continuous mass flux at the inlet boundary is better than the continuous concentration, and the combination of the continuous mass flux at the inlet boundary and the semi-infinite at the outlet boundary is recommended for the modelling of pore-water concentration profile. For the modelling of effluent concentration curve, the combination of the continuous concentration at the inlet boundary and the semi-infinite at the outlet boundary is better than other three combinations of boundary conditions, which is recommended for the modelling of effluent concentration curve.