Alan D. Hewitt

Representative Sampling for Energetic Compounds at Military Training Ranges

Abstract Field sampling experiments were conducted at various locations on training ranges at three military installations within North America. The areas investigated included an anti-tank range firing point, an anti-tank range impact area, an artillery-range firing point, and an artillery-range impact area. The purpose of this study was to develop practical sampling strategies to reliably estimate mean concentrations of residues from munitions found in surface soil at various types of live-fire training ranges. The ranges studied differ in the types of energetic residues deposited and the mode of deposition. In most cases, the major source zones for these residues are the top two or three centimeters of soil. Multi-increment sampling was used to reduce the variance between field sample replicates and to enhance sample representativeness. Based on these criteria the results indicate that a single or a few discrete samples do not provide representative data for these types of sites. However, samples built from at least 25 increments provided data that was sufficiently representative to allow for the estimation of energetic residue mass loading in surface soils and to characterize the training activity at a given location, thereby addressing two objectives that frequently are common to both environmental and forensic investigations.

Grain-scale mechanisms influencing the elution of ions from snow

Abstract Columns containing synthetic, naturally- or laboratory-aged snow grains were washed with deionized distilled water and with a simulated precipitation solution to investigate both chemical fractionation and preferential ion elution. The resulting elution order and concentrations of Cl − , NO 3 − and SO 4 2− were not influenced by chromatographic effects, indicating that snow grains do not possess selective affinity for inorganic anions. Fractionation and preferential chemical elution were strongly influenced by ion exclusion and rearrangement processes occurring during dry snow metamorphism, independent of melt-freeze cycles.

Use of Snow-Covered Ranges to Estimate Explosives Residues from High-Order Detonations of Army Munitions

Estimation of the amounts of residues resulting from high-order detonation of munitions is complicated by the presence of residues from previous detonations and the inability to easily obtain adequately-sized samples to overcome spatial heterogeneity in residue deposition. This study was conducted to assess the use of snow-covered ranges to provide these types of estimates. Specifically, snow-covered ranges were used to estimate the amount of explosives residues that resulted from detonation of individual mortar rounds and a small antipersonnel land mine. At Fort Drum, NY, 60 mm mortars were fired and at Camp Ethan Allen, VT, 81 mm mortars and a Yugolavian PMA2 land mine were detonated by EOD (explosives ordnance disposal) personnel after attaching C4 (RDX) and/or a blasting cap. The locations where residues were deposited were identified by the presence of soot from the detonation of TNT on the surface of the otherwise clean snow. Large surface snow samples were collected with a snow shovel and the melted snow was extracted and analyzed by gas chromatography with an electron capture detector (GC-ECD) and reversed-phase high performance liquid chromatography (RP-HPLC). For both types of mortars the main charge was composition B (60% RDX and 39% TNT); for the land mine, the main charge was TNT with an RDX booster. The major residues produced for the mortars were RDX and nitroglycerine (NG), with lesser amounts of HMX, and TNT. Surface concentrations ranged from as high as 4430 mg/m 2 for RDX to <0.05 mg/m 2 for TNT, both at Camp Ethan Allen. For the land mine, the major residues were TNT and RDX with surface concentrations of 20.8 and 1.8 mg/m 2 , respectively. Published by Elsevier Science B.V.

A Methodology for Assessing Sample Representativeness

Abstract Assessing sample representativeness is a critical component of any environmental investigation and should be performed before any conclusions are reached. If the samples are not representative, any conclusions or decisions will be incorrect. A complete understanding of the data quality objective process, sample plan design, sample plan implementation, and quality control is required to assess sample representativeness. This article presents a methodology for the evaluation of sample representativeness.

Sampling for Explosives-Residues at Fort Greely, Alaska

Fort Greely, Alaska has an extensive complex of weapon training and testing areas located on lands withdrawn from the public domain under the Military Lands Withdrawal Act (PL106-65). The Army has pledged to implement a program to identify possible munitions contamination. Because of the large size (344,165,000 m2) of the high hazard impact areas, characterization of these constituents will be difficult. We used an authoritative sampling design to find locations most likely to contain explosives-residues on three impact areas. We focused our sampling on surface soils and collected multi-increment and discrete samples at locations of known firing events and from areas on the range that had craters, pieces of munitions, targets, or a designation as a firing point. In the two impact areas used primarily by the Army, RDX was the most frequently detected explosive. In the impact area that was also used by the Air Force, TNT was the most frequently detected explosive. Where detected, the explosives concentrations generally were low (<0.05 mg/kg) except in soils near low-order detonations, where the explosive-filler was in contact with the soil surface. These low-order detonations potentially can serve as localized sources for groundwater contamination if positioned in recharge areas.

Field Observations of the Persistence of Comp B Explosives Residues in a Salt Marsh Impact Area

Field observations of weathering Comp B (RDX/TNT 60/40) residue were made on a live-fire training range over four years. The Comp B residue was formed by low-order detonations of 120-mm mortar projectiles. Physical changes were the disaggregation of initially solid chunks into masses of smaller diameter pieces and formation of red phototransformation products that washed off with rain or tidal flooding. Disaggregation increased the surface area of the residue, thereby increasing the potential for dissolution. The bulk of the mass of Comp B was in the craters, but solid chunks were scattered asymmetrically up to 30m away.

Energetic residues from field disposal of gun propellants

Military training with howitzers and mortars produces excess propellant that is burned on the training range and can result in point sources containing high concentrations of unreacted propellant constituents. Propellants contain energetic compounds such as nitroglycerin (NG) and 2,4-dinitrotoluene (2,4-DNT), both of which are found at firing positions and propellant disposal areas. To quantify the mass of residue remaining from the field-expedient disposal of propellants, two mortar propellants and one howitzer propellant were burned under different field conditions. These conditions included burning on a snow pack, at the bottom of a snow pit, and in a pan surrounded by snow for the mortar propellants and on dry and wet sand for the howitzer propellant. For the mortar propellant, the energetics (NG) remaining after burning in the bowl, on frozen ground, and on snow were 0.21%, 5.2% and 18%, respectively. For the howitzer propellant, the difference in energetics (2,4-DNT) remaining after disposal on wet and dry sand was <0.1%, with the overall residue rate of around 1%, similar to that for the mortar propellant burned in an open container. These tests demonstrate that environmental factors, especially in winter, can play a significant role in the effectiveness of field-expedient disposal of propellants.

Subsampling Variance for 2,4-DNT in Firing Point Soils

At 105-mm howitzer firing points, 2,4-DNT is detectable in the surface soils, but field sampling and laboratory subsampling uncertainty can be large during quantitation. The 2,4-DNT is in particulate form, within fibers or slivers of the nitrocellulose-based propellant. The slender fibers range up to 7.5 mm in length with masses of several 100 μ g. Size fractionation of a firing point soil revealed that most of the 2,4-DNT was in the 0.595- to 2.00-mm size range, although the bulk of the soil was less than 0.6 mm prior to grinding. Machine grinding for five minutes was needed to pulverize the propellant fibers sufficiently so that estimates of 2,4-DNT were reproducible in replicate analytical subsamples. To determine 2,4-DNT, we have adopted the practice of grinding firing point soils for five one-minute intervals, with time for heat dissipation between grinds, prior to obtaining individual or replicate 10-g subsamples.

in situ thermal desorption of VOCs in vadose zone soils

A volatile organic compound (VOC) sampler developed for the site characterization and analysis penetrometer system (SCAPS) program to provide semi-quantitative field screening data was evaluated in the laboratory and in the field. The device is based on thermal desorption principles and is capable of sampling in the vadose and capillary zones. Approximately 5 g of soil is desorbed in situ, and the volatilized compounds transferred to the surface, where they are trapped and analyzed by ion trap mass spectroscopy (ITMS). Ex situ validation samples from a Mostap™ core taken 9 in. away from the in situ sample are of two types. One sample is placed in the sampler and desorbed and analyzed in the same manner as the in situ sample. The second validation sample is preserved in methanol and analyzed off site by GC/MS. Comparisons of in situ data to ex situ validation data show that subsurface heterogeneity strongly affects correlation, especially in zones of bedded sand and silt. When the two ex situ samples from the Mostap™ core are compared, the subsurface heterogeneity factor is removed and the co-efficient of determination (r2) increases to 85%.

Time for a Change of Scene

Since the inception of the global effort to remediate contaminated sites back in the 1970s, countless millions of soil samples have been collected and sent to laboratories for chemical analysis. Most of those soil samples were collected as discrete samples, and despite the efforts of those who collected them, the sampling results were often difficult at best to interpret. Relatively recently some professionals in the environmental field have advanced an approach generally known as incremental sampling. Incremental sampling tackles head-on many of the thorny issues that challenge every soil sampling campaign, and it is finding wider acceptance. The time is ripe for a national—or perhaps even international—dialogue concerning incremental sampling, particularly as it seems to address many of the shortcomings of common soil sampling practices.