Assessment of Sampling Error Associated with Collection and Analysis of SoilSamples at a Firing Range Contaminated with HMX

摘要

Short-range and mid-range (grid size) spatial heterogeneity in explosivesconcentrations within surface soils was studied at an active antitank firing range at the Canadian Force Base-Valcartier, Val-Belair, Quebec. Intensive sampling was conducted over short distances using a 6-m square grid (36-sq m) pattern including two target tanks. Sixteen grids were installed. Four area-integrated surface samples were formed into piles, one in each quadrant of each grid, using a circular pattern that included about 10% of the top 5 cm of the quadrant. After in-situ homogenization of a pile, several random aliquots were combined to form a representative sample. Replicates were collected to assess the representativeness achieved. In addition, grid composites were prepared by combining equal portions of the four subgrid samples for each of sixteen grids. In nine of the subgrids, a second area integrated sample was prepared. On-site analysis showed concentrations of HMX ranging from as high as 1640 mg/kg near one target to 2.1 mg/kg at a distance of 15 m from the target. On the other hand, TNT concentrations were much lower than would be expected based on the 70:30 composition ratio of HMX to TNT in the melt-cast explosive used on site. A colorimetric method, originally developed to analyze for RDX, was found to provide concentration estimates for HMX that were in excellent agreement with laboratory results. Spatial heterogeneity of HMX concentrations was large on both