The transport of the chemical signature compounds from buried landmines 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 on the mobility of the water and gaseous phases, their molecular and mechanical diffusion, adsorption characteristics, soil water content, compaction, and environmental factors. A 3D framework is required 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 the chemical-signature-compounds, 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 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.
The transport of the chemical signature compounds from buried landmines in a three-dimensional minefield array has been numerically modeled using the finite-volume technique. Compounds such as trinitrotoluene and dinitrotoluene 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 distributions of such chemicals depend on the mobility of the water and gaseous phases, their molecular and mechanical diffusion, adsorption characteristics, soil water content and compaction, and environmental factors. Surface concentrations decrease, when precipitation occurs due to advective flux around the object. Deformation in the concentrations contours after rainfall is observed in the inclined surface case and it is attributed to both: the advective flux, and to the water flux at the surface caused by the inclination. The LaGrit code developed at Los Alamos National Laboratory (LANL) was used to generate the 3D grid array and to place several landmines at different underground positions. The simulations were performed by using the Finite-Element Heat and Mass-transfer code also developed originally at LANL.
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