OIL MIGRATION THROUGH UNSATURATED SOILS AND ITS EFFECT ON THE VADOSE ZONE INTERACTIVE PROCESSES (VIP) MODEL OUTPUT

A mathematical model called the Vadose Zone Interactive Processes (VIP ) model was developed;lad implemented at Utah State University (USU) f or evaluating the fare of hazardous substances iu the unsaturated zone of the soil during land treatment of oily wastes, The VIP model, whic h simulates the concentration profiles of the hazardous compounds in t he soil, water, and the air phases, assumes a fixed oily phase. The pu rpose of this study was to measure oil migration iu soil systems and t o determine its effect or the VIP model output. Experiments were condu cted at USU to demonstrate the mobility of an oil through the unsatura ted zone of the soil. The oil migration studies were conducted in labo ratory scale glass columns. A Light petroleum oil and two types of soi l were used for the experiments. The water flow rate through the colum ns was adjusted to maintain saturated and unsaturated soil conditions. A predetermined quantity of soil and oil mixture was applied to the t op of the soil column. The concentration of oil in this mixture was ap plied to the top of the soil column. The concentration of oil in this mixture varied from 5% to 30% (on a mass basis). The oil present in th e mixture migrated down through the column with the aid of the infiltr ating water. After water had been flowing through the columns for the desired test times, the column was sectioned and the soil from the var ious depths was collected and analyzed for moisture and oil contents. The leachate produced was also collected and analyzed for oil content. The experiments demonstrated that oil migrates down significantly thr ough the soil columns. The extent of migration depended on the volume of oil applied and the type of soil. However, the applied oil was comp letely immobilized in the columns. The VIP model was modified to incor porate oil migration. The modified VIP model can be expected to produc e more realistic contaminant concentration profiles during land treatm ent of oily wastes when compared to that produced by the present versi on of the VIP model.