A small-scale field column experiment was set up to assess the impact of a native tropical grass (Fimbrystilis Cymosa)
on the transport and distribution of high explosives (TNT and DNT). Explosives powders in a membrane were embedded
as a point source below 2 inches from the column surface. Three different surfaces were layered on top of the explosives
layer: one column with sand, two columns with Fimbrystilis Cymosa, and one column with a mixture of (sand+clay) soil.
Hydraulic differences due to surface vegetation which would affect explosives transport were monitored by measuring
the amount of infiltrated rain water. For the biogeochemical parameters, explosives concentrations in the infiltrated water
were quantified. At the end of the experiment, each column was sacrificed by multiple layers and distribution of
explosives concentrations, soil pH, and soil dehydrogenase concentration was quantified from the layers. Plants were
also analyzed for explosives concentrations in their leaves and roots.
KEYWORDS: 3D modeling, Solar radiation models, Solar radiation, Explosives, Sensors, Process control, Diffusion, Visible radiation, Ultraviolet radiation, Data modeling
Chemical, biological, and canine detection of buried explosive devices (BEDs) rely on the presence of explosive related
compounds (ERCs) near the soil-atmospheric surface. ERC distribution near this surface and its relation to the location
of BEDs is controlled by fate and transport processes. Experimental work was conducted in a 3D laboratory-scale
SoilBed system to determine the effect of cyclic rainfall, evaporation, temperature, and solar radiation on on the fate,
transport and detection of ERCs near soil surfaces. Experiments were conducted by burying a TNT/DNT source under
the soil surface, and applying different rainfall and light radiation cycles while monitoring salt tracers and TNT solute
concentrations temporally and spatially within the SoilBed. Transport of non-reactive solutes was highly influenced by
the cyclic variations on water flux, water content, evaporation, and influx concentrations. Concentrations of TNT and
other ERCs were further affected by vapor transport and sorptive and degradation processes.
Detection of explosive-related chemicals (ERCs) derived from landmines sources is influenced by fate and transport
processes. Characterization and quantification of the effects of environmental factors on the fate and transport
behavior ERCs near soil surface environments requires the development of physical models that can mimic the
conditions found in the field. The development of the scalable systems and methods involves proper reproduction of
soil composition, lithology and structures, appropriate placement of boundary conditions, and suitable simulation of
representative environmental conditions. This paper evaluates the ability of different packing methods for clayey
soils to attain physical and transport properties representative of field conditions, and which can yield reproducible
results across different scales and dimensions. Characteristics and reproducibility of packing properties is evaluated
in terms of soil bulk density, porosity, flow capacity and particle size distribution. The packing methods were tested
under different water content conditions and they are described as infiltration packing, saturation packing, plastic
limit packing, inverse infiltration packing, induced settling packing, and vibration packing. The systems were
evaluated for consistent bulk density, porosity, flow capacity and particle size distribution with depth. Preliminary
results exhibit satisfactory bulk density and porosity values for the vibration packing method under field water
content conditions, ranging from 1.15 to 1.31 g cm-3 and from 42 to 44%, respectively. This method also shows
acceptable flow capacity and the particle size distribution that is found in the field.
Chemical detection of buried explosives devices (BEDs) through chemical sensing is influenced by factors affecting the transport
of chemical components associated with the devices. Explosive-related chemicals, such as 2,4-dinitrotolune (DNT), are
somewhat volatile and their overall transport is influenced by vapor-phase diffusion. Gaseous diffusion depends on
environmental and soil conditions. The significance of this mechanism is greater for unsaturated soil, and increases as water
content decreases. Other mechanisms, such as sorption and degradation, which affect the overall fate and transport, may be more
significant under diffusion transport due to the higher residence time of ERCs in the soil system. Gaseous diffusion in soil was
measured using a one-dimensional physical model (1-D column) to simulate the diffusion flux through soil under various
environmental conditions. Samples are obtained from the column using solid phase microextraction (SPME) and analyzed with a
gas chromatography. Results suggest that DNT overall diffusion is influenced by diffusive and retention processes, water content,
source characteristics, and temperature. DNT effective gas phase diffusion in the soil decreases with increasing soil water
content. Vapor transport retardation was more dominant at low water contents. Most of the retardation is associated to the
partition of the vapor to the soil-water. DNT vapor flux is higher near the explosive source (mine) than at the soil surface. This
flux also increases with higher soil water content and temperature. Results also suggest non-equilibrium transport attributed to
mass transfer limitations and non-linear sorption.
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