Transport of explosive residue surrogates in saturated porous media

Contamination of soils by munitions constituents is pervasive on Department of Defense operational ranges. Low-order detonations result in the heterogeneous distribution of explosives residues (ER) at shallow depths. At a limited number of ranges ER contamination of groundwater has been observed. Previous studies have shown that the downward migration of colloid-sized contaminants can significantly impact groundwater quality. The goal of this study was to investigate if colloid transport plays a role in the migration of ER contaminants. Our primary objective was to determine the transport potential of fine (\u3c5\u3eum) ER particles under ideal conditions for colloid transport. A secondary objective was to develop a direct detection method for the identification and quantitative analysis of particulate ER. A series of saturated transport experiments were conducted in columns (2x20 cm) packed with clean sand. 2,6- Dinitrotoluene was used as a surrogate for explosives chemicals. Experiments were conducted with both particulate and dissolved-phase DNT. Bromide and microspheres tracers were also used to characterize nonreactive transport. Particulate tracers were applied to the columns, either suspended in the influent solution, or directly to the top layer of sand, in order to more realistically replicate field conditions. Experimental results indicate that DNT movement through the columns occurred as a combination of solid and dissolved phase transport. Concentration differences between unfiltered and filtered samples indicate that particulate DNT accounted up to 30% of the total mass recovered in the effluent