Mathematical Modeling of Solute Segregation and Redistribution During Freezing in Peat and Overlying Water (Heat and Mass Transfer, Solidification, Peatland ).

Abstract

Freezing of the water in a peatland causes the redistribution of existing solutes in both the shallow water and the peat zone. Such solute redistribution phenomena are of interest for establishing the geochronology of deposits and determining the nature of pollutant burial. Understanding these phenomena is important for the consideration of peatlands as multi-use resources. This work presents the theoretical analyses and mathematical models to describe the solute redistribution processes during freezing in overlying water and interstitial water in the porous peat. The analyses include the segregation of the solute at the ice-water interface in both the overlying water and the peat zone, solute transport in overlying water, as well as adsorbable solute and non-adsorbable solute transport in the interstitial water of the peat zone. An algorithm has been developed to solve these nonlinear moving interface problems. A parameter estimation technique has been used to determine parameters in the model that are difficult to obtain directly from the experimental data. Computer simulation using this model provides good predictions for solute concentration profiles in the frozen water and the peat zones, as compared to independent experimental data. The basic theoretical analysis and the mathematical model have been utilized to describe the salt ice formation process and macrosegregation during freezing of binary alloys.