Repositori URV

Identifier: TDX:319

Handle: https://hdl.handle.net/20.500.11797/TDX319

Authors:
Silva Rojas, Orlando

Abstract:
The presence of some chemicals in the vadose zone can affect the physical properties of the fluid phases leading to transport processes known as non-passive. Common numerical models do not account for the simultaneous interaction of various non-passive effects on unsaturated flow and transport. The main objective of this thesis was to develop a detailed model that describe the isothermal non-passive transport of water-soluble organic compounds in the unsaturated zone. The model includes the dependence of density, viscosity, surface tension, molecular diffusion coefficient in the liquid phase, and gas-liquid partition coefficient on the aqueous mixture composition. It also takes into account the decrease in the gas-liquid partition coefficient at high capillary pressures, in accordance with Kelvin's equation for multi-component mixtures.The model was implemented in two numerical codes: 1D and 2D with cylindrical symmetry. It was used to illustrate the one-dimensional infiltration and redistribution of alcohol-water mixtures. Simulation of butanol-water mixtures infiltration in sand was in agreement with the experimental data and simulations reported in the literature. Simulation of infiltration, redistribution and volatilization of aqueous mixtures of methanol in two different soils showed that composition significantly affects volumetric liquid content and concentration profiles, as well as the normalized volatilization and evaporation fluxes. Dispersion in the liquid-phase was the predominant mechanism in the transport of methanol when dispersivity at saturation was set to 7.8 cm. Liquid flow was mainly due to capillary pressure gradients induced by changes in volumetric liquid content. However, for dispersivity at saturation set to 0.2 cm, changes in surface tension d