Investigation of conservative and non-conservative solute transport in soil and comparison of three adsorption models using HYDRUS-2D

In this study,transport of two conservative (sodium chloride) and non-conservative (mono-potassium phosphate) solutes in soil was investigated under laboratory conditions. the experiments were implemented with separately injection of these solutes in a sloping soil bulk. the results showed that the concentration distribution of the both solutes in various parts of the sampling box slope was different and solute outflows from the beginning of the slope earlier than the end of it. because of the adsorption of the non-conservative solute by the soil particles,not only its transport velocity was slower than the conservative solute,but also its peak concentration was less than that of the conservative solute. the hydrus-2d model was used to simulate the solutes transport. the concentration of the conservative solute was satisfactorily simulated with high values of the coefficient of determination (r2=0.907),nash-sutcliffe efficiency coefficient (ef=0.907) and a low value of root mean square error (rmse=0.351 g/l). in the simulation of the non-conservative solute transport,a linear adsorption isotherm and the two non-linear freundlich and langmuir models were individually used. the results of the freundlich model (r2=0.951,ef=0.920 and rmse=0.064 g/l) were better than those of the langmuir (r2=0.811,ef=0.802 and rmse=0.101 g/l) and the linear (r2=0.762,ef=0.761 and rmse=0.111 g/l) models. the results indicated that the conservative and non-conservative solutes had different transport behavior in the soil. the freundlich model was found to be the most appropriate adsorption isotherm for investigation of a non-conservative solute transport in soil.