Abstract
The objective of this work is to analyze and model the transport of a pollutant in the surface layer of unsaturated soil. We are particularly interested to hygroscopic soils where components of the liquid phase are strongly linked to the solid phase. Mass transfer occurring in the liquid phase and gas, taking into account the change of phase liquid-gas. Using an original apparatus, we analyze first the isothermal desorption of water, heptane, trichlorethylene (TCE) and the mixture water + TCE in two soils; one containing clay and organic matter, the other, from Burkina Faso (BF), has lower proportions of these constituents. The phase change liquid-gas of TEC has been experimentally studied in the soil of Burkina with different experimental conditions in temperature and pressure. All the bibliographic and experimental works led us to propose a mathematical model. The validation of the model has focused on the transfer of water only by comparison with transfer experiments on soil columns. This model reflects particularly well the flow of water to the surface and changing profiles of water content in columns. This model is also well suited to describe the water transfer at the interface soil-atmosphere in arid zone. In a second part, we examine the transfer of TCE in the surface layer. Sensitivity studies were conducted on thick layer of soil, water content, the initial concentration of TCE, the Henry constant and the coefficient of phase change. This study highlights the importance of different parameters on the transfer of a volatile organic compound showing that it is necessary to conduct parallel investigations in the laboratory and in situ.