3D NUMERICAL SIMULATION OF THE TRANSPORT OF EXPLOSIVES FROM UXO’s AND LANDMINES Maik Irrazábal, Julio G. Briano, Miguel Castro, and Samuel P. Hernández Center for Chemical Sensors Development, University of Puerto Rico-Mayagüez Department of Chemistry, Department of Chemical Engineering ABSTRACT The transport of explosives from buried mines in a three-dimensional (3D) array has been numerically modeled using the finite-volume technique. Compounds such as trinitrotoluene, dinitrotoluene, and their degradation products, are semi volatile and somewhat soluble in water. Furthermore, they can strongly adsorb to the soil and undergo chemical and biological degradation. Consequently, the spatial and temporal concentration distributions of such chemicals depend mainly on the mobility of the water and gaseous phases, their molecular and mechanical diffusion, adsorption characteristics, soil water content, compaction, and environmental factors affecting water content or its transport. A 3D approach is used in this work since two- dimensional (2D) symmetry may easily fade due to terrain topography: non-flat surfaces, soil heterogeneity, or underground fractures. The spatial and temporal distribution of explosives, in an inclined grid has been obtained. The fact that the chemicals may migrate horizontally, giving higher surface concentrations at positions not directly on top of the objects, emphasizes the need for understanding the transport mechanism of explosives when a chemical detector is used. Deformation in the concentration contours after rainfall is observed in the inclined surface and is attributed to both: the advective flux, and to the water flux at the surface caused by the slope. The analysis of the displacements in the position of the maximum concentrations at the surface, respect to the actual location of the mine, in an inclined system, is presented. Keywords: Numerical simulation, transport, landmines, chemical detection. 1. INTRODUCTION The goal of detecting and removing landmines is a great challenge for the scientific community. The presence of these artifacts in many regions of the world causes an environmental hazard as well as an important humanitarian concern. Several approaches are used to deal with this situation, being the most common ones those based in metals detection. Most anti-personal and anti-tanks devices, however, have little or none metal on them, and are essentially made of plastic compounds with the exception of parts of the fuse and activation mechanism. This forces the use of very sensitive devices resulting on a high frequency of false- positives. Chemical detection has been implemented by the use of dogs, and their success lies on the quality of training and the personnel skills. On the other hand, spectroscopic techniques may be tuned to allow the detection of small traces of specific energetic compounds, and may serve as a basis for the development of more reliable chemical detectors. The main concern with this approach has to do with the fate and transport of the chemicals releases into the ground. Thus, factors affecting the fate and transport (like environmental and soil parameters) will also affect the process of locating the exact position of the buried object. Environmental factors (temperature, relative humidity, rainfall precipitation, wind, sun irradiation, pressure, etc.) as well as soil characteristics (water content, compaction, porosity, chemical composition, particle size distribution, topography, vegetation, etc), have a direct impact in the fate and transport of the chemicals released from a landmine. Chemicals like TNT, DNT, and their degradation products, are semi-volatile, and somewhat