ABSTRACT
In the design of waste disposal facilities and evaluation of groundwater and soil contamination by organic and inorganic species, it is essential a knowledge of the mechanisms of transport of the contaminants. There are two basic processes in the transport of solutes: advection and hydrodynamic dispersion. The processes by which the substances move through porous media can be expressed through mathematical models. They are based on the integration of the advection-dispersion equation using specific boundary conditions for the system of interest. However, their applicability has been often limited due to the lack of reliable parameters obtained experimentally. This work seeks to fulfil the gap between numerical modelling and experimental studies. A new diffusimeter has been developed to measure the diffusion coefficient in unsaturated soils. It combines the single reservoir method, proposed by Rowe et al. (1988), with the osmotic control technique. Tests were performed under suction values ranging from 0 to 500 kpa. Sodium chloride and potassium chloride were used as solutes diffusing through a compacted inert sample prepared in the laboratory. The results obtained indicated that the new proposed technique worked quite well, being however recommended an improvement in the system of suction control through the use of more precise instrumentation.
