Diffusion of explosives through frozen and unfrozen sand

摘要

Areas subject to military conflict or military training sometimes contain unexploded ordinance and/or explosives residues resulting from detonations. A variety of past field and modeling studies have investigated the behavior of explosives in soils in warm climates, but the behavior in cold climates, including frozen soil and snow, has been less studied. In northern areas of military conflict, and at Army military training grounds in cold regions, winter weather exists for many months of the year. The impact of temperature and moisture changes in the soil, due to changing weather conditions, can have a large effect on the fate and transport of the explosives. The basic transport parameters for the behavior of the contaminant in frozen soil are unknown, yet these parameters are needed for problem assessment both for simple estimates and full numerical studies. In this paper we discuss sample results of controlled laboratory experiments performed to investigate the diffusion of 2,4-DNT through sand, under two conditions each of temperature and moisture. Based on the experimental data we present preliminary effective diffusion coefficients for the conditions. The concentrations show clear transport of the contaminant due to vapor diffusion and sorption. Sorption is a controlling feature of diffusion of explosives in sand. Diffusion rates and concentration on the particles increase with temperature. In both frozen and unfrozen sand, higher moisture content causes faster diffusion rates but lower particle concentration levels than in the corresponding dry cases.