Water, Heat And Solute Transport In Frozen Soil:Experimental And Modeling Study

Soil freezing/thawing has become a key factor that impacts agricultural development in cold and arid regions. Water, heat and solute transport during the winter could result in accumulation of salt on field surface, which will influence sowing in the spring. However, due to the complexity in transport of water, heat and solute in frozen soils, the study on their coupled relationships will be the key to solving soil salinization in cold and arid agricultural regions. It would also be of high interest to explore the transport of water, heat and solute in frozen soils and to make out water resources management as well as control salinization in cold and arid regions.In this study, experiments and simulation work were conducted aiming at gaining knowledge on coupled transport prcessses of water, heat and solute in agricultural field in Inner Mongolia, China. The generalized likelihood uncertainty estimation (GLUE) method was firstly applied to the simulation work for understaning the uncertainties in modeling of frozen soils. Main conclusions could be drawn as following:Experimental studies on hydraulic and thermal properties of frozen soils have shown that soil water characteristics and soil freezing characteristics were both influenced by solute types and solute contents. The soil freezing characteristic curve model with modified approach could determine soil freezing characteristic curves well under various soil water and solute conditions. The regression models for soil specific heat capacity and soil thermal conductivity under negative temperatures were also set up by using power and linear functions, respectively.Results from laboratory and field column and plot experiments have demonstrated the coupled transport processes in seasonally frozen soils. Shallow ground and high soil solute conditions could decrease soil freezing speed and increase frozen soil evaporation.By combining the process-based model (CoupModel) and GLUE uncertainty analsysis method, the uncertainties in simulation of frozen soil were also discovered. Simulation of water and heat processes in frozen soil showed large uncertainties due to the complex mechanisms behind them. The developed CoupModel based on experimental results was tested on the ability in depicting soil freezing characteristic when solute existed. The developed model showed high reliability in simulation of water, heat and solute transport in seasonally frozen soils for both the calibrated and validated periods. However, due to complexity in solute transport in frozen soils as well as the simplified processes considered in CoupModel, large unceertainty still existed in modeling results. It would be necessary in the next step of work to conduct well-controlled research into transport of solute in frozen soils and to develop the model with more detailed solute transport processes.