Heat and Mass transfer were studied in closed soil columns. The study included loam soil materials with two salinity levels. The soil was moistened either with distilled water or potassium chloride solution. The initial soil water contents were 0.247 and 0.257 m3/m3 for solute-free and salinized soils conditions, respectively. The initial potassium chloride concentration was 0.78 mol/kg of soil solution for the salinized soil. The moistened soil was packed into PVC columns (1.16-m long and 0.052 m inside diameter). Two replicate columns were packed for each salinity level. Thermocouples were inserted at twelve depths in each soil column. The soil columns were then sealed at both ends and buried vertically in a grass field with column surface exposed to ambient weather conditions in Ames, Iowa. The experiment took place from Dec. 6, 1996 until Feb. 17, 1997. Soil temperature was monitored bihourly during the course of the experiment. On Feb. 17, 1997, the soil columns were removed from the soil and sectioned into 0.02-m increments in order to measure water content and chloride concentration distributions. In addition to the observed heat and mass transfer, the SHAW model was used to predict heat and mass transfer in the soil columns. The SHAW model solved the heat, water, and chemical transfer equations simultaneously. The model described the temperature distributions fairly well for the salinized and solute-free soils. Both observed and predicted values of water distribution showed water accumulation in the upper 0.4 m in the solute-free soil. The water depleted slightly in the upper 0.20-m region in the salinized soil columns. The solute did not move in appreciable amounts in the salinized soil. The observed and predicted frost depths in the solute-free soil were between depths of 0.45 m and 0.65 m. Apparently, freezing did not occur in the salinized soil. Increasing the solute concentration lowered the temperature of freezing in the salinized soil in comparison to the solute-free soil. The SHAW model was also used to predict heat and mass transfer at an initial water of 0.357 m3/m3. The predicted ice content decreased as the solute concentration increased. Increasing the initial water content resulted in an accumulation of solute toward the bottom of the soil profile.
Dr. Gerald N. Flerchinger USDA Agricultural Research Service Northwest Watershed Research Center 800 Park Blvd, Suite 105 Boise, ID 83712 Phone: 208-334-1363 Fax: 208-334-1502 E-mail: gflerchi@nwrc.ars.pn.usbr.gov Ibrahim Nassar Department of Agronomy Iowa State University Ames, IA 50011 E-mail: inassar@iastate.edu Prof. Robert Horton Department of Agronomy Iowa State University Ames, IA 50011 Phone: (515) 294-7843 E-mail: rhorton@iastate.edu