Multi-Increment Sampling for the Characterization of Energetic Residues on Military Training Ranges

U.S. Army Engineer Research and Development Center (ERDC)
Published Nov. 19, 2012

Capability

Training with live munitions can potentially release energetic compounds to training-range soils. The legacy explosives and propellants used in fired munitions contain compounds such as 2,4,6-trinitrotoluene (TNT), dinitrotoluene (DNT), 1,3,5-hexahydro-1,3,5-trinitrotriazine referred to as Research Development Explosive (RDX), octrahydro-1,3,5,7- tetranitro-1,3,5,7-tetrazocine or High Melting Explosive (HMX), and nitroglycerine (NG). The new Insensitive Munitions (IM) compounds such as 2,4-dinitroanisole (DNAN), nitroguanidine (NQ), 3-nitro-1,2,4-triazol-5-one (NTO) can also be released to the environment as can the metals in small-arms projectiles such as antimony (Sb), lead (Pb), and tungsten (W). Munition compounds have varying degrees of toxicity and have the potential to be harmful to humans and biota as result of environmental exposure. Live-fire training with weapon systems results in varying amounts of energetic and metal residues introduced to the environment as small particles. While high-order detonations leave almost no residue, low-order detonations or dud rounds can scatter more than half of their explosive fill onto the soil surface in the form of millimeter- to centimeter-sized explosive particles. ERDC’s Cold Regions Research and Engineering Laboratory (CRREL) and the Interstate Technology Regulatory Council the (ITRC) has developed the Incremental Sampling Method (ISM) to determine the levels of materials of military interest more representatively in range soils.

Approach

The traditional environmental sampling method of taking a few discrete or grab soil samples is not effective when evaluating military ranges because discrete samples do not reflect the varied distribution and composition of energetic and other constituent residues in the soil. Surface soil samples collected using ISM result in more representative results for constituents distributed into the environment in particulate form.

Adapted from methods used in the mining industry, ISM consists of a single sample made up of many soil increments collected from evenly distributed locations throughout the area of interest sampled. The individual soil increments of the same geometry and mass are combined and processed to form a single sample representative of the mean concentration of the constituents of interest occurring throughout the area sampled.

Discrete surface soil sampling, which was commonly used historically on military ranges, is less accurate in providing an estimate of the mean concentration. In studies comparing both discrete and ISM samples from the same site, the discrete sample constituent concentrations varied by orders of magnitude whereas the ISM samples varied by less than 30 percent as determined by calculating the relative standard deviation. Quality assurance procedures have also been developed for ISM, which allow quantification of the sampling error, which is not possible when collecting discrete samples. If applied correctly, ISM is the most cost-effective, reproducible, and defensible method for sampling surface soils where analytes of interest are introduced into the environment as heterogeneously distributed particles.

Requirements

The effectiveness of ISM depends on collecting the soil increments from the entire area of interest. Fifty (50) or more increments should be collected per sample. Ideally, the increments should be evenly distributed within the area (i.e., be the same distance from each other), be taken from the same depth in the soil, and have a similar size and mass. CRREL developed a sampling tool for the collection of multi-increment samples.

Applications

ISM can be used to estimate the concentration of all analytes in most media but was originally developed to address heterogeneously distributed particulates. Before sampling, it is important to determine data quality objectives and to frame the overall goals of the project. These objectives determine how many increments are required per sample and how many ISM samples are needed to provide the information required to achieve the goals.

ERDC-CRREL has used multi-increment samples to map the distribution and concentration of energetic compounds and other constituents of military interest in soils at a variety of military ranges, including anti-tank rocket, artillery, mortar, grenade, aerial bombing, and small-arms ranges.

ISM is effective in characterizing both active and closed military-range soils. Information on energetic concentrations have been used to (1) modify or change the location of live-fire training on active ranges to minimize the threat to groundwater or (2) determine if the land on closed ranges can be reused for other purposes or returned to civilian control.

Multi-increment samples have also been used to quantify how much residue is deposited by high- and low- order detonations of single projectiles detonated on snow — a clean collection surface. This information is needed to estimate the mass (load) of energetics being deposited on training ranges and as input to models that predict the likelihood that energetics will be dissolved and transported to groundwater.

ERDC Points of Contact

Questions about Incremental Sampling Method?

Contact: Jay Clausen, Sam Beal, Matt Bigl
Email: jay.l.clausen@usace.army.mil
Phone: 603-646-4597


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