Vapor-Phase Transport of Explosives Compounds in Soils

Abstract

Abstract : The fate and transport of explosives in the air-filled pores within soil affect both the potential detection of buried ordnance by chemical sensors and vadose zone transport of explosives residues. The efficacy of chemical sensors and their potential usefulness for detecting buried unexploded ordnance (UXO) is difficult to determine without understanding how explosives chemical signatures are transported through soil. The objectives of this study were to quantify chemical signature transport through soils under various environmental conditions in unsaturated soils and to develop a model for chemical signature transport in unsaturated soils. Flux chambers, large soil containers, and batch testing were used to determine explosives signature movement and process descriptors for model development. This study showed that the moisture content and temperature of soils affect the flux of explosives chemical signatures from soils. Low signatures were observed for explosives under all environmental conditions. Low fluxes of even the most volatile compounds from explosives indicate that this environmental loss pathway is minimal. A model was developed that can accurately predict explosives signature movement to the surface where chemical detection can occur when the source strength is known. The model can also predict explosives signature movement and corresponding accumulation of explosives concentrations in vadose zone soils. Chemical sensors will need to be very sensitive because of low signatures. However, this may result in many false alarms because of explosives residues not associated with UXO on firing ranges. Low explosives signatures should also result in insignificant air environmental exposures.