Integral transform analysis of radionuclide transport in variably saturated media using a physical non-equilibrium model: application to solid waste leaching at a uranium mining installation.

The Generalized Integral Transform Technique (GITT) was employed to simulate transient one-dimensional flow in variably saturated porous media, as well as radioactive waste transport within different layers (a solid waste pile, nearby soil, and a granular aquifer) towards the edge of a uranium mining installation under institutional control. Computational codes, written using the Mathematica software system, were implemented and tested for solution of the coupled advection-dispersion equations for an arbitrary number of daughter products within a radioactive chain migrating in saturated and unsaturated soil layers. The computer simulations were verified in great detail against results obtained using the built-in routine NDSolve of the Mathematica platform and the HYDRUS-1D software system.

Quasi-Saturated Layer: Implications for Estimating Recharge and Groundwater Modeling.

This study presents an extension of the concept of "quasi-saturation" to a quasi-saturated layer, defined as the uppermost dynamic portion of the saturated zone subject to water table fluctuations. Entrapped air here may cause substantial reductions in the hydraulic conductivity (K) and fillable pore water. Air entrapment is caused by a rising water table, usually as a result of groundwater recharge.

Determination of specific LNAPL volumes in soils having a multimodal pore-size distribution.

In this paper we present modifications to previously published models for determining the specific volume of non-aqueous phase liquids (LNAPLs) in the subsurface at and near the groundwater table following a spill or leak from the soil surface. The modifications account for porous media having multimodal pore-size distributions as is often the case with tropical soils. Data from the literature are used to show that the use of multimodal pore-size distributions can lead to significantly different subsurface LNAPL specific volume predictions and possible LNAPL recovery rates, compared to when only unimodal pore-size distributions are considered.

Revisiting the horizontal redistribution of water in soils: Experiments and numerical modeling.

A series of experiments and related numerical simulations were carried out to study one-dimensional water redistribution processes in an unsaturated soil. A long horizontal Plexiglas box was packed as homogenously as possible with sand. The sandbox was divided into two sections using a very thin metal plate, with one section initially fully saturated and the other section only partially saturated.

Dissolution kinetics of volatile organic compound vapors in water: An integrated experimental and computational study.

In this study we performed batch experiments to investigate the dissolution kinetics of trichloroethylene (TCE) and toluene vapors in water at room temperature and atmospheric pressure. The batch systems consisted of a water reservoir and a connected headspace, the latter containing a small glass cylinder filled with pure volatile organic compound (VOC). Results showed that air phase concentrations of both TCE and toluene increased relatively quickly to their maximum values and then became constant.