3D laboratory-scale soilbed for assessment of fate and transport of explosive-related compounds in soils under variable environmental conditions

Abstract

This paper presents the development and testing of a three-dimensional laboratory-scale soil tank system for modeling ERC fate and transport under controlled, but variable environmental conditions in partially saturated soil. The system incorporates a rainfall simulator, variable light (visible and UV), temperature and relative humidity components, and a 3D SoilBed capable of simulating several boundary and initial conditions. Experimental work indicate that water and solute transport is highly influenced by interrelated environmental and boundary conditions. The presence of light and higher system temperatures induces greater water drainage and solute fluxes. During infiltration, hydraulic heads increase at faster rates under no light exposure suggesting greater water and solute retention. The spatial and temporal distribution of hydraulic heads during rainfall events is not uniform and flow patterns reflect preferential paths. Transport of conservative solutes closely follows water flow patterns, and reflects the influence of variable and interrelated environmental factors on spatial and temporal concentration distribution. These experiments show that interrelated environmental factors must be taken into account to accurately predict the distribution of chemicals near the soil-atmosphere surface. They demonstrate that non-reactive solutes are highly influenced by variation in hydraulic, advective, and dispersive processes induced by changes in environmental conditions. Greater impacts are expected for reactive and semi-volatile solutes such as ERCs. In such case, fate and transport will also be affected by variations in soptive, gas transport, and degradation processes.