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The heterogeneous distribution of munitions constituents, released as particles from munitions firing and detonations on military training ranges, presents challenges for representative soil sample collection and for defensible decision making. Military range characterization studies and the development of the incremental sampling methodology (ISM) have enabled the development of recommended methods for soil sampling that produce representative and reproducible concentration data for munitions constituents. This article provides a broad overview of recommended soil sampling and processing practices for analysis of munitions constituents on military ranges.
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<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
  
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'''Related Article(s)''':
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'''CONTRIBUTOR(S):'''  [[Dr. Samuel Beal]]
  
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
  
'''Related Article(s):'''
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'''Key Resource(s)''':
*[[Direct Push (DP) Technology]]
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*[[media:Taylor-2011 ERDC-CRREL TR-11-15.pdf| Guidance for Soil Sampling of Energetics and Metals]]<ref name= "Taylor2011">Taylor, S., Jenkins, T.F., Bigl, S., Hewitt, A.D., Walsh, M.E. and Walsh, M.R., 2011. Guidance for Soil Sampling for Energetics and Metals (No. ERDC/CRREL-TR-11-15). [[media:Taylor-2011 ERDC-CRREL TR-11-15.pdf| Report.pdf]]</ref>
*[[Geophysical Methods]]
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*[[Media:Hewitt-2009 ERDC-CRREL TR-09-6.pdf| Report.pdf | Validation of Sampling Protocol and the Promulgation of Method Modifications for the Characterization of Energetic Residues on Military Testing and Training Ranges]]<ref name= "Hewitt2009">Hewitt, A.D., Jenkins, T.F., Walsh, M.E., Bigl, S.R. and Brochu, S., 2009. Validation of sampling protocol and the promulgation of method modifications for the characterization of energetic residues on military testing and training ranges (No. ERDC/CRREL-TR-09-6). Engineer Research and Development Center / Cold Regions Research and Engineering Lab (ERDC/CRREL) TR-09-6, Hanover, NH, USA. [[Media:Hewitt-2009 ERDC-CRREL TR-09-6.pdf | Report.pdf]]</ref>
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*[[media:Epa-2006-method-8330b.pdf| U.S. EPA SW-846 Method 8330B: Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC)]]<ref name= "USEPA2006M">U.S. Environmental Protection Agency (USEPA), 2006. Method 8330B (SW-846): Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC), Rev. 2. Washington, D.C. [[media:Epa-2006-method-8330b.pdf | Report.pdf]]</ref>
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*[[media:Epa-2007-method-8095.pdf | U.S. EPA SW-846 Method 8095: Explosives by Gas Chromatography.]]<ref name= "USEPA2007M">U.S. Environmental Protection Agency (US EPA), 2007. Method 8095 (SW-846): Explosives by Gas Chromatography. Washington, D.C. [[media:Epa-2007-method-8095.pdf| Report.pdf]]</ref>
  
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==Introduction==
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[[File:Beal1w2 Fig1.png|thumb|200 px|left|Figure 1: Downrange distance of visible propellant plume on snow from the firing of different munitions. Note deposition behind firing line for the 84-mm rocket. Data from: Walsh et al.<ref>Walsh, M.R., Walsh, M.E., Ampleman, G., Thiboutot, S., Brochu, S. and Jenkins, T.F., 2012. Munitions propellants residue deposition rates on military training ranges. Propellants, Explosives, Pyrotechnics, 37(4), pp.393-406. [http://dx.doi.org/10.1002/prep.201100105 doi: 10.1002/prep.201100105]</ref><ref>Walsh, M.R., Walsh, M.E., Hewitt, A.D., Collins, C.M., Bigl, S.R., Gagnon, K., Ampleman, G., Thiboutot, S., Poulin, I. and Brochu, S., 2010. Characterization and Fate of Gun and Rocket Propellant Residues on Testing and Training Ranges: Interim Report 2. (ERDC/CRREL TR-10-13.  Also: ESTCP Project ER-1481)  [[media:Walsh-2010 ERDC-CRREL TR-11-15 ESTCP ER-1481.pdf| Report]]</ref>]]
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[[File:Beal1w2 Fig2.png|thumb|left|200 px|Figure 2: A low-order detonation mortar round (top) with surrounding discrete soil samples produced concentrations spanning six orders of magnitude within a 10m by 10m area (bottom). (Photo and data: A.D. Hewitt)]]
  
'''CONTRIBUTOR(S):''' [[Gaisheng Liu]] and [[Jim Butler]]
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Munitions constituents are released on military testing and training ranges through several common mechanisms. Some are locally dispersed as solid particles from incomplete combustion during firing and detonation. Also, small residual particles containing propellant compounds (e.g., [[Wikipedia: Nitroglycerin | nitroglycerin [NG]]] and [[Wikipedia: 2,4-Dinitrotoluene | 2,4-dinitrotoluene [2,4-DNT]]]) are distributed in front of and surrounding target practice firing lines (Figure 1). At impact areas and demolition areas, high order detonations typically yield very small amounts (<1 to 10 mg/round) of residual high explosive compounds (e.g., [[Wikipedia: TNT | TNT ]], [[Wikipedia: RDX | RDX ]] and [[Wikipedia: HMX | HMX ]]) that are distributed up to and sometimes greater than) 24 m from the site of detonation<ref name= "Walsh2017">Walsh, M.R., Temple, T., Bigl, M.F., Tshabalala, S.F., Mai, N. and Ladyman, M., 2017. Investigation of Energetic Particle Distribution from High‐Order Detonations of Munitions. Propellants, Explosives, Pyrotechnics, 42(8), pp.932-941. [https://doi.org/10.1002/prep.201700089 doi: 10.1002/prep.201700089] [[media: Walsh-2017-High-Order-Detonation-Residues-Particle-Distribution-PEP.pdf| Report.pdf]]</ref>.
  
'''Key Resource(s)''':
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Low-order detonations and duds are thought to be the primary source of munitions constituents on ranges<ref>Hewitt, A.D., Jenkins, T.F., Walsh, M.E., Walsh, M.R. and Taylor, S., 2005. RDX and TNT residues from live-fire and blow-in-place detonations. Chemosphere, 61(6), pp.888-894. [https://doi.org/10.1016/j.chemosphere.2005.04.058 doi: 10.1016/j.chemosphere.2005.04.058]</ref><ref>Walsh, M.R., Walsh, M.E., Poulin, I., Taylor, S. and Douglas, T.A., 2011. Energetic residues from the detonation of common US ordnance. International Journal of Energetic Materials and Chemical Propulsion, 10(2). [https://doi.org/10.1615/intjenergeticmaterialschemprop.2012004956 doi: 10.1615/IntJEnergeticMaterialsChemProp.2012004956] [[media:Walsh-2011-Energetic-Residues-Common-US-Ordnance.pdf| Report.pdf]]</ref>. Duds are initially intact but may become perforated or fragmented into micrometer to centimeter;o0i0k-sized particles by nearby detonations<ref>Walsh, M.R., Thiboutot, S., Walsh, M.E., Ampleman, G., Martel, R., Poulin, I. and Taylor, S., 2011. Characterization and fate of gun and rocket propellant residues on testing and training ranges (No. ERDC/CRREL-TR-11-13). Engineer Research and Development Center / Cold Regions Research and Engineering Lab (ERDC/CRREL) TR-11-13, Hanover, NH, USA. [[media:Epa-2006-method-8330b.pdf| Report.pdf]]</ref>. Low-order detonations can scatter micrometer to centimeter-sized particles up to 20 m from the site of detonation<ref name= "Taylor2004">Taylor, S., Hewitt, A., Lever, J., Hayes, C., Perovich, L., Thorne, P. and Daghlian, C., 2004. TNT particle size distributions from detonated 155-mm howitzer rounds. Chemosphere, 55(3), pp.357-367.[[media:Taylor-2004 TNT PSDs.pdf| Report.pdf]]</ref>
*[https://doi.org/10.1007/1-4020-3102-5_2 Hydrogeological Methods for Estimation of Spatial Variations in Hydraulic Conductivity]<ref name= "Butler2005">Butler, J.J., 2005. Hydrogeological methods for estimation of spatial variations in hydraulic conductivity. In Hydrogeophysics (pp. 23-58). Springer, Dordrecht. [https://doi.org/10.1007/1-4020-3102-5_2 doi: 10.1007/1-4020-3102-5_2 ]</ref>  
 
*Hydraulic conductivity profiling with direct push methods<ref name= "Liu2012"> Liu, G., Butler, J.J., Reboulet, E. and Knobbe, S., 2012. Hydraulic conductivity profiling with direct push methods. Grundwasser, 17(1), pp.19-29. [https://doi.org/10.1007/s00767-011-0182-9 doi: 10.1007/s00767-011-0182-9]</ref>
 
*Groundwater<ref name= "Freeze1979">Freeze, R.A., Cherry, J.A. and Groundwater., A., 1979. Prentice-Hall. Inc., Englewood Cliffs, NJ ISBN 0-13-365312-9.</ref>
 
  
==Introduction==
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The particulate nature of munitions constituents in the environment presents a distinct challenge to representative soil sampling. Figure 2 shows an array of discrete soil samples collected around the site of a low-order detonation – resultant soil concentrations vary by orders of magnitude within centimeters of each other. The inadequacy of discrete sampling is apparent in characterization studies from actual ranges which show wide-ranging concentrations and poor precision (Table 1).
Hydraulic conductivity is mathematically defined as the parameter ''K'' in Darcy’s Law<ref>Darcy, H. (1856). Les Fontaines Publiques de la Ville de Dijon, Dalmont, Paris. [https://doi.org/10.1029/2001wr000727 doi: 10.1029/2001WR000727]</ref> (see Fig. 1),
 
  
[[File:Liu1w2 Eq1.png|300 px]]
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In comparison to discrete sampling, incremental sampling tends to yield reproducible concentrations (low relative standard deviation [RSD]) that statistically better represent an area of interest<ref name= "Hewitt2009"/>.
  
{|
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{| class="wikitable" style="float: right; text-align: center; margin-left: auto; margin-right: auto;"
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|+ Table 1. Soil Sample Concentrations and Precision from Military Ranges Using Discrete and Incremental Sampling. (Data from Taylor et al. <ref name= "Taylor2011"/> and references therein.)
 
|-
 
|-
| where:
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! Military Range Type !! Analyte !! Range<br/>(mg/kg) !! Median<br/>(mg/kg) !! RSD<br/>(%)
 
|-
 
|-
| ''Q'' || is the flow rate across area ''A'' of a porous medium,
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| colspan="5" style="text-align: left;" | '''Discrete Samples'''
 
|-
 
|-
| ''K'' || is the hydraulic conductivity, and
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| Artillery FP || 2,4-DNT || <0.04 – 6.4 || 0.65 || 110
 
|-
 
|-
| ''i'' || is the hydraulic gradient, which can be computed as:
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| Antitank Rocket || HMX || 5.8 – 1,200 || 200 || 99
|}
 
 
 
[[File:Liu1w2 Eq2.png| 300 px]]
 
 
 
{|
 
 
|-
 
|-
| where:
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| Bombing || TNT || 0.15 – 780 || 6.4 || 274
 
|-
 
|-
| ''h<sub>1</sub>'' and ''h<sub>2</sub>''  &nbsp; &nbsp; || are the hydraulic heads at the ends of the experimental domain, and
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| Mortar || RDX || <0.04 – 2,400 || 1.7 || 441
 
|-
 
|-
| ''L'' || is the total length.
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| Artillery || RDX || <0.04 – 170 || <0.04 || 454
|}
 
 
 
[[File:Liu1w2 Fig1.png|thumb|Figure 1. Schematic of Darcy’s Law flow experiment.]]
 
 
 
Hydraulic conductivity is dependent on the properties of both water and the porous medium,
 
 
 
[[File:Liu1w2 Eq3.png|300 px]]
 
 
 
{|
 
 
|-
 
|-
| where:
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| colspan="5" style="text-align: left;" | '''Incremental Samples*'''
 
|-
 
|-
| ''k'' || is the intrinsic permeability of the medium, a parameter which is solely dependent on the geometry of the interconnected pores,
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| Artillery FP || 2,4-DNT || 0.60 – 1.4 || 0.92 || 26
 
|-
 
|-
| ''g'' || is the gravitational constant,
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| Bombing || TNT || 13 – 17 || 14 || 17
 
|-
 
|-
| ''&rho;'' || is the density of the pore water, and
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| Artillery/Bombing || RDX || 3.9 – 9.4 || 4.8 || 38
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|-
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| Thermal Treatment || HMX || 3.96 – 4.26 || 4.16 || 4
 
|-
 
|-
| ''&mu;'' || is the dynamic viscosity of the pore water, respectively.
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| colspan="5" style="text-align: left; background-color: white;" | * For incremental samples, 30-100 increments and 3-10 replicate samples were collected.
 
|}
 
|}
  
Many approaches have been developed to characterize ''K''<ref name= "Butler2005"/>. These approaches can be grouped into two general categories based on how the ''K'' estimates are obtained:
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==Incremental Sampling Approach==
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ISM is a requisite for representative and reproducible sampling of training ranges, but it is an involved process that is detailed thoroughly elsewhere<ref name= "Hewitt2009"/><ref name= "Taylor2011"/><ref name= "USEPA2006M"/>. In short, ISM involves the collection of many (30 to >100) increments in a systematic pattern within a decision unit (DU). The DU may cover an area where releases are thought to have occurred or may represent an area relevant to ecological receptors (e.g., sensitive species). Figure 3 shows the ISM sampling pattern in a simplified (5x5 square) DU. Increments are collected at a random starting point with systematic distances between increments. Replicate samples can be collected by starting at a different random starting point, often at a different corner of the DU. Practically, this grid pattern can often be followed with flagging or lathe marking DU boundaries and/or sampling lanes and with individual pacing keeping systematic distances between increments. As an example, an artillery firing point might include a 100x100 m DU with 81 increments.
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[[File:Beal1w2 Fig3.png|thumb|200 px|left|Figure 3. Example ISM sampling pattern on a square decision unit. Replicates are collected in a systematic pattern from a random starting point at a corner of the DU. Typically more than the 25 increments shown are collected]]
  
*hydraulic methods that involve water injection or extraction and the measurement of the induced pressure response, and
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DUs can vary in shape (Figure 4), size, number of increments, and number of replicates according to a project’s data quality objectives.
* indirect methods that rely on empirical correlations, often site-specific in nature, between ''K'' and other more readily evaluated formation properties (e.g., resistance to electric current).  
 
  
Because hydraulic methods can be directly related to the mathematical definition of ''K'' through Darcy’s Law, ''K'' estimates obtained with those methods are generally considered to be more reliable than those obtained with indirect methods.
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[[File:Beal1w2 Fig4.png|thumb|right|250 px|Figure 4: Incremental sampling of a circular DU on snow shows sampling lanes with a two-person team in process of collecting the second replicate in a perpendicular path to the first replicate. (Photo: Matthew Bigl)]]
  
Other classifications of ''K'' characterization approaches are possible. For example, approaches can be divided into those based on data collected in the field and those based on measurements on core samples in the laboratory. In the latter case, there can be considerable uncertainty about how representative the core sample is of field conditions.  
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==Sampling Tools==
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In many cases, energetic compounds are expected to reside within the soil surface. Figure 5 shows soil depth profiles on some studied impact areas and firing points. Overall, the energetic compound concentrations below 5-cm soil depth are negligible relative to overlying soil concentrations. For conventional munitions, this is to be expected as the energetic particles are relatively insoluble, and any dissolved compounds readily adsorb to most soils<ref>Pennington, J.C., Jenkins, T.F., Ampleman, G., Thiboutot, S., Brannon, J.M., Hewitt, A.D., Lewis, J., Brochu, S., 2006. Distribution and fate of energetics on DoD test and training ranges: Final Report. ERDC TR-06-13, Vicksburg, MS, USA. Also: SERDP/ESTCP Project ER-1155. [[media:Pennington-2006_ERDC-TR-06-13_ESTCP-ER-1155-FR.pdf| Report.pdf]]</ref>. Physical disturbance, as on hand grenade ranges, may require deeper sampling either with a soil profile or a corer/auger.
  
Field-based approaches can be further subdivided based on whether the measurement is conducted in the subsurface or on the surface. Subsurface measurements provide the most reliable information about ''K'' variations at the scale needed for environmental site investigations. Nearly all field-based hydraulic methods are performed in the subsurface and require either boreholes or direct push (DP) installations for extracting or injecting water and monitoring the induced head changes. Compared to methods that rely on existing wells, DP approaches can be applied essentially wherever ''K'' information is needed, thus greatly expanding the spatial coverage of ''K'' measurement in the field. DP approaches, however, are generally limited to use in relatively shallow (20-30 m from land surface) unconsolidated settings.
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[[File:Beal1w2 Fig5.png|thumb|left|200 px|Figure 5. Depth profiles of high explosive compounds at impact areas (bottom) and of propellant compounds at firing points (top). Data from: Hewitt et al. <ref>Hewitt, A.D., Jenkins, T.F., Ramsey, C.A., Bjella, K.L., Ranney, T.A. and Perron, N.M., 2005. Estimating energetic residue loading on military artillery ranges: Large decision units (No. ERDC/CRREL-TR-05-7). [[media:Hewitt-2005 ERDC-CRREL TR-05-7.pdf| Report.pdf]]</ref> and Jenkins et al. <ref>Jenkins, T.F., Ampleman, G., Thiboutot, S., Bigl, S.R., Taylor, S., Walsh, M.R., Faucher, D., Mantel, R., Poulin, I., Dontsova, K.M. and Walsh, M.E., 2008. Characterization and fate of gun and rocket propellant residues on testing and training ranges (No. ERDC-TR-08-1). [[media:Jenkins-2008 ERDC TR-08-1.pdf| Report.pdf]]</ref>]]
  
Field ''K'' measurements can also be performed on the land surface or in an aircraft. Most of these are geophysical approaches that involve measuring electrical, magnetic, or seismic properties of the formation and then transforming them into ''K'' estimates using empirical relations. The biggest advantage of surface or airborne approaches is their minimal site disturbance, as no subsurface boring is needed. However, the resolution that can be provided is limited, as the measurements are typically affected by conditions over a relatively large volume of the formation. Geophysical methods can also be performed in boreholes. Borehole geophysical methods can provide a much higher resolution description of ''K'' than surface-based methods.
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Soil sampling with the Cold Regions Research and Engineering Laboratory (CRREL) Multi-Increment Sampling Tool (CMIST) or similar device is an easy way to collect ISM samples rapidly and reproducibly. This tool has an adjustable diameter size corer and adjustable depth to collect surface soil plugs (Figure 6). The CMIST can be used at almost a walking pace (Figure 7) using a two-person sampling team, with one person operating the CMIST and the other carrying the sample container and recording the number of increments collected. The CMIST with a small diameter tip works best in soils with low cohesion, otherwise conventional scoops may be used. Maintaining consistent soil increment dimensions is critical.
 
The scale of measurement is an important factor to consider when assessing various approaches. For water-supply investigations, a single estimate of ''K'' averaged over a large volume of an aquifer will usually suffice; such an estimate is commonly obtained via pumping tests in a well<ref name= "Freeze1979"/>. For water-quality investigations, however, ''K'' estimates over a large measurement volume are often of limited value<ref name= "Butler2009">Butler Jr, J.J., 2009. Pumping tests for aquifer evaluation - Time for a change?. Groundwater, 47(5), pp.615-617. [https://doi.org/10.1111/j.1745-6584.2008.00488.x doi: 10.1111/j.1745-6584.2008.00488.x]</ref>. In that case, small-scale ''K'' measurements that provide information about local geological controls on groundwater flow and transport are usually required to obtain reliable predictions of contaminant behavior and to design effective remediation systems.  
 
  
In this article, we focus on the approaches that can be used to obtain small-scale, localized measurements of ''K'' for environmental site investigations. Only the more commonly used approaches are discussed. Some other approaches, such as dipole flow tests<ref>Kabala, Z.J., 1993. The dipole flow test: A new single‐borehole test for aquifer characterization. Water Resources Research, 29(1), pp.99-107. [https://doi.org/10.1029/92WR01820 doi: 10.1029/92WR01820]</ref><ref>Zlotnik, V.A. and Zurbuchen, B.R., 1998. Dipole probe: Design and field applications of a single‐borehole device for measurements of vertical variations of hydraulic conductivity. Groundwater, 36(6), pp.884-893. [https://doi.org/10.1111/j.1745-6584.1998.tb02095.x doi: 10.1111/j.1745-6584.1998.tb02095.x]</ref>, tracer tests<ref>Datta‐Gupta, A., Yoon, S., Vasco, D.W. and Pope, G.A., 2002. Inverse modeling of partitioning interwell tracer tests: A streamline approach. Water Resources Research, 38(6), pp.15-1. [https://doi.org/10.1029/2001WR000597 doi: 10.1029/2001WR000597]</ref>, or hydraulic tomography<ref>Yeh, T.C.J. and Liu, S., 2000. Hydraulic tomography: Development of a new aquifer test method. Water Resources Research, 36(8), pp.2095-2105. [[media:2000-Yeh-Hydraulic_Tomography..Development_of_a_new_aquifer_test_method.pdf| Report.pdf]]</ref><ref>Bohling, G.C. and Butler Jr, J.J., 2010. Inherent limitations of hydraulic tomography. Groundwater, 48(6), pp.809-824. [https://doi.org/10.1111/j.1745-6584.2010.00757.x doi: 10.1111/j.1745-6584.2010.00757.x]</ref> will not be discussed here. 
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The sampling tool should be cleaned between replicates and between DUs to minimize potential for cross-contamination<ref>Walsh, M.R., 2009. User’s manual for the CRREL Multi-Increment Sampling Tool. Engineer Research and Development Center / Cold Regions Research and Engineering Lab (ERDC/CRREL) SR-09-1, Hanover, NH, USA. [[media:Walsh-2009 ERDC-CRREL SR-09-1.pdf | Report.pdf]]</ref>.
  
==Hydraulic Testing Approaches==
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==Sample Processing==
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While only 10 g of soil is typically used for chemical analysis, incremental sampling generates a sample weighing on the order of 1 kg. Splitting of a sample, either in the field or laboratory, seems like an easy way to reduce sample mass; however this approach has been found to produce high uncertainty for explosives and propellants, with a median RSD of 43.1%<ref name= "Hewitt2009"/>. Even greater error is associated with removing a discrete sub-sample from an unground sample. Appendix A in [https://www.epa.gov/sites/production/files/2015-07/documents/epa-8330b.pdf U.S. EPA Method 8330B]<ref name= "USEPA2006M"/> provides details on recommended ISM sample processing procedures.
  
===Pumping Tests===
+
Incremental soil samples are typically air dried over the course of a few days. Oven drying thermally degrades some energetic compounds and should be avoided<ref>Cragin, J.H., Leggett, D.C., Foley, B.T., and Schumacher, P.W., 1985. TNT, RDX and HMX explosives in soils and sediments: Analysis techniques and drying losses. (CRREL Report 85-15) Hanover, NH, USA. [[media:Cragin-1985 CRREL 85-15.pdf| Report.pdf]]</ref>. Once dry, the samples are sieved with a 2-mm screen, with only the less than 2-mm fraction processed further. This size fraction represents the USDA definition of soil. Aggregate soil particles should be broken up and vegetation shredded to pass through the sieve. Samples from impact or demolition areas may contain explosive particles from low order detonations that are greater than 2 mm and should be identified, given appropriate caution, and potentially weighed.
The pumping test is the most common method for determining ''K'' over a relatively large volume of an aquifer in water-supply investigations<ref name= "Butler2009"/>. During a typical test, the pumping rate is kept constant, although it can be varied in time to obtain better signal-to-noise ratios in the acquired data<ref>Rasmussen, T.C., Haborak, K.G. and Young, M.H., 2003. Estimating aquifer hydraulic properties using sinusoidal pumping at the Savannah River site, South Carolina, USA. Hydrogeology Journal, 11(4), pp.466-482. [https://doi.org/10.1007/s10040-003-0255-7 doi: 10.1007/s10040-003-0255-7]</ref>. In the constant-rate approach, a well, preferably centrally located at the site, is pumped while induced head changes are monitored at that and nearby wells. The head changes, along with the pumping rate, can then be used to estimate aquifer parameters using different models of the well-aquifer configuration<ref>Batu, V., 1998. Aquifer hydraulics: a comprehensive guide to hydrogeologic data analysis. John Wiley & Sons.</ref><ref>Kruseman, G.P., De Ridder, N.A. and Verweij, J.M., 1990. Analysis and evaluation of pumping test data – ILRI Pub. 47. The Netherlands: International institute for land reclamation and improvement</ref>. Pumping test analyses can be facilitated using software packages like AQTESOLV (Aquifer Test Solver), which has been developed for analyzing different types of aquifer tests<ref name= "Duffield2007">Duffield, G.M., 2007. AQTESOLV for Windows Version 4.5 User's Guide. HydroSOLVE, Reston, VA.</ref>.
 
  
Pumping tests are primarily performed to obtain large-scale volumetric averages of aquifer parameters as well as information about aquifer boundaries. However, one form of the pumping test, the step-drawdown test, is specifically directed at getting information about the efficiency of the pumping well. The ''K'' estimate from a pumping test is an average over a large volume of the formation and does not provide information at the scale of most relevance for issues involving contaminant transport (e.g., meters or less). Thus, pumping tests are less commonly employed for environmental site investigations<ref name= "Butler2009"/>.  
+
The <2-mm soil fraction is typically still ≥1 kg and impractical to extract in full for analysis. However, subsampling at this stage is not possible due to compositional heterogeneity, with the energetic compounds generally present as <0.5 mm particles<ref name= "Walsh2017"/><ref name= "Taylor2004"/>. Particle size reduction is required to achieve a representative and precise measure of the sample concentration. Grinding in a puck mill to a soil particle size <75 µm has been found to be required for representative/reproducible sub-sampling (Figure 8). For samples thought to contain propellant particles, a prolonged milling time is required to break down these polymerized particles and achieve acceptable precision (Figure 9). Due to the multi-use nature of some ranges, a 5-minute puck milling period can be used for all soils. Cooling periods between 1-minute milling intervals are recommended to avoid thermal degradation. Similar to field sampling, sub-sampling is done incrementally by spreading the sample out to a thin layer and collecting systematic random increments of consistent volume to a total mass for extraction of 10 g (Figure 10).
  
===Slug Tests===
+
<li style="display: inline-block;">[[File:Beal1w2 Fig6.png|thumb|200 px|Figure 6: CMIST soil sampling tool (top) and with ejected increment core using a large diameter tip (bottom).]]</li>
The slug test is one of the most common methods for determining ''K'' at the scale of relevance for environmental site investigations<ref name= "Butler1997">Butler Jr, J.J., 1997. The design, performance, and analysis of slug tests. Crc Press.</ref><ref name= "Butler2009"/>. Slug tests are typically performed in existing wells at multiple horizontal and vertical locations across the site to characterize the spatial distribution of ''K'' values. However, slug tests can also be performed in temporary installations such as DP rods. In this approach, a near-instantaneous head change is applied in the well or DP rods and the subsequent head recovery is used to estimate ''K''. The initial head change can be introduced using a solid object (slug), compressed gas (pneumatic system), or by the addition/removal of a certain amount of water<ref name= "Butler1997"/>. The recovery data can be analyzed using different models of the well-formation configuration<ref name= "Duffield2007"/><ref name= "Butler1997"/>. In contrast to pumping tests, slug tests provide a ''K'' estimate that is primarily a function of the materials in the vicinity of the screened interval of the test well. Slug test data analyses can be facilitated using software packages like AQTESOLV (Aquifer Test Solver), which has been developed for analyzing different test methods<ref name= "Duffield2007"/>.
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<li style="display: inline-block;">[[File:Beal1w2 Fig7.png|thumb|200 px|Figure 7: Two person sampling team using CMIST, bag-lined bucket, and increment counter. (Photos: Matthew Bigl)]]</li>
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<li style="display: inline-block;">[[File:Beal1w2 Fig8.png|thumb|200 px|Figure 8: Effect of machine grinding on RDX and TNT concentration and precision in soil from a hand grenade range. Data from Walsh et al.<ref>Walsh, M.E., Ramsey, C.A. and Jenkins, T.F., 2002. The effect of particle size reduction by grinding on subsampling variance for explosives residues in soil. Chemosphere, 49(10), pp.1267-1273. [https://doi.org/10.1016/S0045-6535(02)00528-3 doi: 10.1016/S0045-6535(02)00528-3]</ref> ]]</li>
 +
<li style="display: inline-block;">[[File:Beal1w2 Fig9.png|thumb|200 px|Figure 9: Effect of puck milling time on 2,4-DNT concentration and precision in soil from a firing point. Data from Walsh et al.<ref>Walsh, M.E., Ramsey, C.A., Collins, C.M., Hewitt, A.D., Walsh, M.R., Bjella, K.L., Lambert, D.J. and Perron, N.M., 2005. Collection methods and laboratory processing of samples from Donnelly Training Area Firing Points, Alaska, 2003 (No. ERDC/CRREL-TR-05-6). [[media:Walsh-2005 ERDC-CRREL TR-05-6.pdf| Report.pdf]]</ref>.]]</li>
 +
<li style="display: inline-block;">[[File:Beal1w2 Fig10.png|thumb|200 px|center|Figure 10: Incremental sub-sampling of a milled soil sample spread out on aluminum foil.]]</li>
  
Although a slug test is very simple in principle, considerable care must be taken in all stages of a test<ref name= "Butler2005"/><ref name= "Butler1997"/><ref name= "Butler2009"/>. Because test responses are highly sensitive to the materials immediately adjacent to the test well, that well must be appropriately developed before a test is performed. Otherwise, the ''K'' estimate can be biased by a low-''K'' zone (skin) that can form during well construction. In high-''K'' formations, the head recovery is rapid, and pneumatic methods are often used to minimize the time associated with test initiation. In addition, due to the relatively high flow velocity, the impact of pipe hydraulics on pressure readings should be considered when analyzing slug test data from high-''K'' zones<ref name= "Butler2003">Butler Jr, J.J., Garnett, E.J. and Healey, J.M., 2003. Analysis of slug tests in formations of high hydraulic conductivity. Groundwater, 41(5), pp.620-631. [https://doi.org/10.1111/j.1745-6584.2003.tb02400.x doi: 10.1111/j.1745-6584.2003.tb02400.x]</ref>.  In low-''K'' formations, slug tests can take an extremely long time to complete, although test time can be significantly reduced by decreasing the effective casing radius (portion of well in which the water level is changing)<ref name= "Butler1997"/>.
+
==Analysis==
+
Soil sub-samples are extracted and analyzed following [[Media: epa-2006-method-8330b.pdf | EPA Method 8330B]]<ref name= "USEPA2006M"/> and [[Media:epa-2007-method-8095.pdf | Method 8095]]<ref name= "USEPA2007M"/> using [[Wikipedia: High-performance liquid chromatography | High Performance Liquid Chromatography (HPLC)]] and [[Wikipedia: Gas chromatography | Gas Chromatography (GC)]], respectively. Common estimated reporting limits for these analysis methods are listed in Table 2.
Slug tests can be configured to obtain information about vertical variations in ''K'' along the screened (open) interval of a well. Test intervals can be isolated with straddle packers, and slug tests performed within that isolated interval. The straddle packers can be incrementally moved along the screened interval of a well to characterize the vertical variation of ''K'' at a relatively high resolution. Using a two-packer tool (Fig. 2A), slug tests have been performed in a number of 0.25-m intervals in a well at the Geohydrologic Experimental and Monitoring Site (GEMS) in the Kansas River valley<ref name= "Butler2005"/>.  At each isolated interval, multiple tests are performed, initiated with different head changes, following recommended test guidelines<ref name= "Butler1997"/><ref name= "Butler2009"/>. An example data set is presented in Figure 2B. The multi-level slug test ''K'' estimates compare favorably with estimates obtained using other approaches (Fig. 3).  
 
  
<div><ul>
+
{| class="wikitable" style="float: center; text-align: center; margin-left: auto; margin-right: auto;"
<li style="display: inline-block;">[[File:Liu1w2 Fig2A.png|thumb|400 px|Figure 2A. Schematic of a falling-head slug test (water flows from well into aquifer) performed in a multi-level slug-test system. Head change is introduced in standpipe, which is directly connected to the interval isolated by the straddle packers (not to scale).]] 
+
|+ Table 2. Typical Method Reporting Limits for Energetic Compounds in Soil. (Data from Hewitt et al.<ref>Hewitt, A., Bigl, S., Walsh, M., Brochu, S., Bjella, K. and Lambert, D., 2007. Processing of training range soils for the analysis of energetic compounds (No. ERDC/CRREL-TR-07-15). Hanover, NH, USA. [[media:Hewitt-2007 ERDC-CRREL TR-07-15.pdf| Report.pdf]]</ref>)
<li style="display: inline-block;">[[File:Liu1w2 Fig2B.png|thumb|400 px|Figure 2B. Example data plot from a multilevel slug test at GEMS. Test is initiated by sudden depressurization of a pressurized air column<ref name= "Butler2003"/>.]]</li>
+
|-
<li style="display: inline-block;">[[File:Liu1w2 Fig3.png|thumb|400 px|Figure 3. ''K'' estimates from different field methods at GEMS<ref name= "Butler2005"/>. Well DW is located 2 m east of GEMS4S.]]
+
! rowspan="2" | Compound
</ul></div>
+
! colspan="2" | Soil Reporting Limit (mg/kg)
 
+
|-
In addition to existing wells, slug tests can also be performed in DP installations so that ''K'' estimates can be obtained virtually at any location in unconsolidated formations. Various approaches have been developed that allow slug tests to be performed at one or multiple levels in a single DP hole<ref>Hinsby, K., Bjerg, P.L., Andersen, L.J., Skov, B. and Clausen, E.V., 1992. A mini slug test method for determination of a local hydraulic conductivity of an unconfined sandy aquifer. Journal of Hydrology, 136(1-4), pp.87-106. [https://doi.org/10.1016/0022-1694(92)90006-H doi: 10.1016/0022-1694(92)90006-H]</ref><ref>Butler Jr, J.J., Healey, J.M., McCall, G.W., Garnett, E.J. and Loheide, S.P., 2002. Hydraulic tests with direct‐push equipment. Groundwater, 40(1), pp.25-36. [https://doi.org/10.1111/j.1745-6584.2002.tb02488.x doi: 10.1111/j.1745-6584.2002.tb02488.x]</ref><ref name= "McCall2002">McCall, W., J.J. Butler, Jr., J.M. Healey, A.A. Lanier, S.M. Sellwood, and E.J. Garnett, 2002. A dual-tube direct-push method for vertical profiling of hydraulic conductivity in unconsolidated formations, Environ. & Eng. Geoscience, 8(2), 75-84.  [https://doi.org/10.2113/gseegeosci.8.2.75 doi: 10.2113/gseegeosci.8.2.75]</ref><ref name= "Sellwood2005">Sellwood, S.M., Healey, J.M., Birk, S. and Butler, J.J., 2005. Direct‐push hydrostratigraphic profiling: coupling electrical logging and slug tests. Ground water, 43(1), pp.19-29. [http://dx.doi.org/10.1111/j.1745-6584.2005.tb02282.x  doi: 10.1111/j.1745-6584.2005.tb02282.x]</ref>.  In McCall et al. (2002)<ref name= "McCall2002"/>, a pair of nested rod strings were driven to the test interval with a solid drive point attached to the end of inner rod string for advancement. Upon reaching the test depth, the drive point and inner rod string were retracted, and a screen was lowered to the bottom of the outer rod string. The outer rod string was pulled up while the screen was held in place, leaving the screen exposed to the surrounding formation. After the slug test was completed in the exposed screen, the screen was removed and the inner rod string with the attached solid drive point was reinserted. The nested rod strings were then driven to the next test depth. In low-''K'' formations such as silts and clays, the formation materials may not collapse completely back to the screen when the outer rod string is pulled up. In this case, the diameter of the borehole can be estimated and used in place of the screen diameter, or the problem can be avoided by using a coring tube of similar size to the screen to create a hole below the end of the outer rod string. Instead of setting the screen by pulling up the outer rod string, the screen can be directly inserted into the hole for slug testing. Regardless of how the screen is set into the formation, it is always recommended that the screen be appropriately developed before slug tests are performed. In low-''K'' formations, development may be limited to scraping the sides of the cored hole with a steel brush and removing the silty water from the screen with a low-flow pump.
+
! HPLC (8330)  
 
+
! GC (8095)
Sellwood et al. (2005)<ref name= "Sellwood2005"/> proposed a modification of the approach by McCall et al. (2002)<ref name= "McCall2002"/> to reduce profiling time and gain more information about subsurface stratigraphy. Instead of performing slug tests on the way down, slug tests were performed at different depths as the outer rod string was pulled up (Fig. 4). This way, the number of changes between the outer and inner rod strings was minimized (i.e., only one change needed at the bottom of the profile). Furthermore, an electrical conductivity (EC) probe was attached to the inner rod string so that EC data could be collected as the rod strings were advanced; the EC data could then be used for selecting the intervals for slug tests as the rod strings were retracted. This approach, called hydrostratigraphic profiling, enabled the collection of information on electrical and hydraulic conductivity to be obtained at a speed and resolution that had previously not been possible. 
+
|-
 
+
| HMX || 0.04 || 0.01
[[File:Liu1w2 Fig4.png|thumb|right|400 px|Figure 4. Schematic illustrating hydrostratigraphic profiling, the combination of electrical conductivity (EC) and multilevel slug test profiling<ref name= "Sellwood2005"/>.]]
+
|-
 
+
| RDX || 0.04 || 0.006
===Borehole Flowmeter Profiling===
+
|-
Borehole flowmeter profiling is one of the most efficient approaches for characterizing the vertical variations of ''K''<ref name= "Molz1989">Molz, F.J., Morin, R.H., Hess, A.E., Melville, J.G. and Güven, O., 1989. The impeller meter for measuring aquifer permeability variations: evaluation and comparison with other tests. Water Resources Research, 25(7), pp.1677-1683. [https://doi.org/10.1029/WR025i007p01677 doi: 10.1029/WR025i007p01677]</ref>. This approach involves pumping a well at a constant rate while measuring the vertical flow rate within the screened interval (Fig. 5). A flowmeter is initially positioned at the bottom of the screen. After the pump is turned on and the pumping rate stabilizes, the flowmeter is gradually moved up, often in an incremental fashion with short stops, although continuous profiling is also done. After the entire screened interval is measured, the profile of vertical flow rates versus depths can be used for ''K'' estimation. Typically, two profiles are performed, one prior to pumping and one during pumping. The profile obtained during pumping is corrected with the profile prior to pumping to remove the impacts of ambient flow in the well. Due to the difficulty of detecting small differences in flow rates, the ''K'' estimates from flowmeter profiling are subject to more noise in less permeable settings<ref name= "Bohling2012">Bohling, G.C., Liu, G., Knobbe, S.J., Reboulet, E.C., Hyndman, D.W., Dietrich, P. and Butler, J.J., 2012. Geostatistical analysis of centimeter‐scale hydraulic conductivity variations at the MADE site. Water Resources Research, 48(2). [https://doi.org/10.1029/2011wr010791 doi: 10.1029/2011WR010791]</ref>. In addition, the results of flowmeter profiling are sensitive to in-well hydraulics, such as the impedance of flowmeter to vertical flow and disturbance by the pump intake when it is too close to the measurement interval<ref name= "Butler2005"/>.
+
| [[Wikipedia: 1,3,5-Trinitrobenzene | TNB]] || 0.04 || 0.003
 
+
|-
[[File:Liu1w2 Fig5.png|thumb|400 px|Figure 5. Schematic diagram showing the borehole flowmeter profiling procedure<ref name = "Molz1989"/>.]]
+
| TNT || 0.04 || 0.002
 
+
|-
Different types of flowmeters have been used for borehole profiling<ref>Young, S.C. and Pearson, H.S., 1995. The electromagnetic borehole flowmeter: Description and application. Groundwater Monitoring & Remediation, 15(4), pp.138-147. [https://doi.org/10.1111/j.1745-6592.1995.tb00561.x doi: 10.1111/j.1745-6592.1995.tb00561.x]</ref>.  For example, electromagnetic flowmeters are often used in environmental site investigations due to their lower flow rate detection limit and lower head loss (high head loss across the flowmeter can cause flow bypass through the filter pack of the well). However, they may be more expensive than other options and have certain practical limitations as well<ref>Bomana, G.K., Molz, F.J. and Boonec, K.D., 1997. Borehole flowmeter application in fluvial sediments: Methodology, results, and assessment. Groundwater, 35(3), pp.443-450. [https://doi.org/10.1111/j.1745-6584.1997.tb00104.x doi: 10.1111/j.1745-6584.1997.tb00104.x]</ref>.  Heat pulse flowmeters are also used for profiling in less-permeable settings.
+
| [[Wikipedia: 2,6-Dinitrotoluene | 2,6-DNT]] || 0.08 || 0.002
 
 
The most common method of estimating ''K'' from borehole flowmeter profiles is based on the assumption that the lateral flow rate of an interval (zone between flow-rate measurements) is proportional to the ''K'' and thickness of that interval in a well fully screened in a perfectly layered aquifer,
 
 
 
[[File:Liu1w2 Eq4.png|400 px]]
 
{|
 
 
|-
 
|-
| where:
+
| 2,4-DNT || 0.04 || 0.002
 
|-
 
|-
| ''K<sub>i</sub>'' || is the ''K'' of test interval ''i'';
+
| 2-ADNT || 0.08 || 0.002
 
|-
 
|-
| ''K<sub>a</sub>'' || is the average ''K'' for the entire screened interval;
+
| 4-ADNT || 0.08 || 0.002
 
|-
 
|-
| ''&Delta;Q<sub>i</sub>'' || is the net lateral inflow across interval ''i'', which can be calculated by subtracting the flow rate at the bottom of the interval from that at the top and taking ambient flow, if any, into account;
+
| NG || 0.1 || 0.01
 
|-
 
|-
| ''Q<sub>t</sub>'' ||is the total pumping rate;
+
| [[Wikipedia: Dinitrobenzene | DNB ]] || 0.04 || 0.002
 
|-
 
|-
| ''&Delta;B<sub>i</sub>'' || is the thickness of interval ''i''; and
+
| [[Wikipedia: Tetryl | Tetryl ]]  || 0.04 || 0.01
 
|-
 
|-
| ''B<sub>t</sub>'' || is the total thickness of the aquifer.
+
| [[Wikipedia: Pentaerythritol tetranitrate | PETN ]] || 0.2 || 0.016
 
|}
 
|}
 
''K<sub>a</sub>'' can be obtained from pumping or slug tests at the same well, although it is generally recommended that slug tests be used, as the average ''K'' in the immediate vicinity of the well may differ from that determined from a pumping test in a laterally heterogeneous aquifer<ref name= "Butler2005"/>.
 
 
Figure 3 compares the results of borehole flowmeter profiling and multilevel slug tests at GEMS. Despite some local differences, the ''K'' estimates from borehole flowmeter profiling and multilevel slug tests are quite similar at that well.
 
 
===DP Injection Logging===
 
 
 
 
 
  
 
==References==
 
==References==
<references />
+
<references/>
  
 
==See Also==
 
==See Also==
 +
*[https://itrcweb.org/ Interstate Technology and Regulatory Council]
 +
*[http://www.hawaiidoh.org/tgm.aspx Hawaii Department of Health]
 +
*[http://envirostat.org/ Envirostat]

Latest revision as of 18:58, 29 April 2020

The heterogeneous distribution of munitions constituents, released as particles from munitions firing and detonations on military training ranges, presents challenges for representative soil sample collection and for defensible decision making. Military range characterization studies and the development of the incremental sampling methodology (ISM) have enabled the development of recommended methods for soil sampling that produce representative and reproducible concentration data for munitions constituents. This article provides a broad overview of recommended soil sampling and processing practices for analysis of munitions constituents on military ranges.

Related Article(s):


CONTRIBUTOR(S): Dr. Samuel Beal


Key Resource(s):

Introduction

Figure 1: Downrange distance of visible propellant plume on snow from the firing of different munitions. Note deposition behind firing line for the 84-mm rocket. Data from: Walsh et al.[5][6]
Figure 2: A low-order detonation mortar round (top) with surrounding discrete soil samples produced concentrations spanning six orders of magnitude within a 10m by 10m area (bottom). (Photo and data: A.D. Hewitt)

Munitions constituents are released on military testing and training ranges through several common mechanisms. Some are locally dispersed as solid particles from incomplete combustion during firing and detonation. Also, small residual particles containing propellant compounds (e.g., nitroglycerin [NG] and 2,4-dinitrotoluene [2,4-DNT]) are distributed in front of and surrounding target practice firing lines (Figure 1). At impact areas and demolition areas, high order detonations typically yield very small amounts (<1 to 10 mg/round) of residual high explosive compounds (e.g., TNT , RDX and HMX ) that are distributed up to and sometimes greater than) 24 m from the site of detonation[7].

Low-order detonations and duds are thought to be the primary source of munitions constituents on ranges[8][9]. Duds are initially intact but may become perforated or fragmented into micrometer to centimeter;o0i0k-sized particles by nearby detonations[10]. Low-order detonations can scatter micrometer to centimeter-sized particles up to 20 m from the site of detonation[11]

The particulate nature of munitions constituents in the environment presents a distinct challenge to representative soil sampling. Figure 2 shows an array of discrete soil samples collected around the site of a low-order detonation – resultant soil concentrations vary by orders of magnitude within centimeters of each other. The inadequacy of discrete sampling is apparent in characterization studies from actual ranges which show wide-ranging concentrations and poor precision (Table 1).

In comparison to discrete sampling, incremental sampling tends to yield reproducible concentrations (low relative standard deviation [RSD]) that statistically better represent an area of interest[2].

Table 1. Soil Sample Concentrations and Precision from Military Ranges Using Discrete and Incremental Sampling. (Data from Taylor et al. [1] and references therein.)
Military Range Type Analyte Range
(mg/kg)
Median
(mg/kg)
RSD
(%)
Discrete Samples
Artillery FP 2,4-DNT <0.04 – 6.4 0.65 110
Antitank Rocket HMX 5.8 – 1,200 200 99
Bombing TNT 0.15 – 780 6.4 274
Mortar RDX <0.04 – 2,400 1.7 441
Artillery RDX <0.04 – 170 <0.04 454
Incremental Samples*
Artillery FP 2,4-DNT 0.60 – 1.4 0.92 26
Bombing TNT 13 – 17 14 17
Artillery/Bombing RDX 3.9 – 9.4 4.8 38
Thermal Treatment HMX 3.96 – 4.26 4.16 4
* For incremental samples, 30-100 increments and 3-10 replicate samples were collected.

Incremental Sampling Approach

ISM is a requisite for representative and reproducible sampling of training ranges, but it is an involved process that is detailed thoroughly elsewhere[2][1][3]. In short, ISM involves the collection of many (30 to >100) increments in a systematic pattern within a decision unit (DU). The DU may cover an area where releases are thought to have occurred or may represent an area relevant to ecological receptors (e.g., sensitive species). Figure 3 shows the ISM sampling pattern in a simplified (5x5 square) DU. Increments are collected at a random starting point with systematic distances between increments. Replicate samples can be collected by starting at a different random starting point, often at a different corner of the DU. Practically, this grid pattern can often be followed with flagging or lathe marking DU boundaries and/or sampling lanes and with individual pacing keeping systematic distances between increments. As an example, an artillery firing point might include a 100x100 m DU with 81 increments.

Figure 3. Example ISM sampling pattern on a square decision unit. Replicates are collected in a systematic pattern from a random starting point at a corner of the DU. Typically more than the 25 increments shown are collected

DUs can vary in shape (Figure 4), size, number of increments, and number of replicates according to a project’s data quality objectives.

Figure 4: Incremental sampling of a circular DU on snow shows sampling lanes with a two-person team in process of collecting the second replicate in a perpendicular path to the first replicate. (Photo: Matthew Bigl)

Sampling Tools

In many cases, energetic compounds are expected to reside within the soil surface. Figure 5 shows soil depth profiles on some studied impact areas and firing points. Overall, the energetic compound concentrations below 5-cm soil depth are negligible relative to overlying soil concentrations. For conventional munitions, this is to be expected as the energetic particles are relatively insoluble, and any dissolved compounds readily adsorb to most soils[12]. Physical disturbance, as on hand grenade ranges, may require deeper sampling either with a soil profile or a corer/auger.

Figure 5. Depth profiles of high explosive compounds at impact areas (bottom) and of propellant compounds at firing points (top). Data from: Hewitt et al. [13] and Jenkins et al. [14]

Soil sampling with the Cold Regions Research and Engineering Laboratory (CRREL) Multi-Increment Sampling Tool (CMIST) or similar device is an easy way to collect ISM samples rapidly and reproducibly. This tool has an adjustable diameter size corer and adjustable depth to collect surface soil plugs (Figure 6). The CMIST can be used at almost a walking pace (Figure 7) using a two-person sampling team, with one person operating the CMIST and the other carrying the sample container and recording the number of increments collected. The CMIST with a small diameter tip works best in soils with low cohesion, otherwise conventional scoops may be used. Maintaining consistent soil increment dimensions is critical.

The sampling tool should be cleaned between replicates and between DUs to minimize potential for cross-contamination[15].

Sample Processing

While only 10 g of soil is typically used for chemical analysis, incremental sampling generates a sample weighing on the order of 1 kg. Splitting of a sample, either in the field or laboratory, seems like an easy way to reduce sample mass; however this approach has been found to produce high uncertainty for explosives and propellants, with a median RSD of 43.1%[2]. Even greater error is associated with removing a discrete sub-sample from an unground sample. Appendix A in U.S. EPA Method 8330B[3] provides details on recommended ISM sample processing procedures.

Incremental soil samples are typically air dried over the course of a few days. Oven drying thermally degrades some energetic compounds and should be avoided[16]. Once dry, the samples are sieved with a 2-mm screen, with only the less than 2-mm fraction processed further. This size fraction represents the USDA definition of soil. Aggregate soil particles should be broken up and vegetation shredded to pass through the sieve. Samples from impact or demolition areas may contain explosive particles from low order detonations that are greater than 2 mm and should be identified, given appropriate caution, and potentially weighed.

The <2-mm soil fraction is typically still ≥1 kg and impractical to extract in full for analysis. However, subsampling at this stage is not possible due to compositional heterogeneity, with the energetic compounds generally present as <0.5 mm particles[7][11]. Particle size reduction is required to achieve a representative and precise measure of the sample concentration. Grinding in a puck mill to a soil particle size <75 µm has been found to be required for representative/reproducible sub-sampling (Figure 8). For samples thought to contain propellant particles, a prolonged milling time is required to break down these polymerized particles and achieve acceptable precision (Figure 9). Due to the multi-use nature of some ranges, a 5-minute puck milling period can be used for all soils. Cooling periods between 1-minute milling intervals are recommended to avoid thermal degradation. Similar to field sampling, sub-sampling is done incrementally by spreading the sample out to a thin layer and collecting systematic random increments of consistent volume to a total mass for extraction of 10 g (Figure 10).

  • Figure 6: CMIST soil sampling tool (top) and with ejected increment core using a large diameter tip (bottom).
  • Figure 7: Two person sampling team using CMIST, bag-lined bucket, and increment counter. (Photos: Matthew Bigl)
  • Figure 8: Effect of machine grinding on RDX and TNT concentration and precision in soil from a hand grenade range. Data from Walsh et al.[17]
  • Figure 9: Effect of puck milling time on 2,4-DNT concentration and precision in soil from a firing point. Data from Walsh et al.[18].
  • Figure 10: Incremental sub-sampling of a milled soil sample spread out on aluminum foil.
  • Analysis

    Soil sub-samples are extracted and analyzed following EPA Method 8330B[3] and Method 8095[4] using High Performance Liquid Chromatography (HPLC) and Gas Chromatography (GC), respectively. Common estimated reporting limits for these analysis methods are listed in Table 2.

    Table 2. Typical Method Reporting Limits for Energetic Compounds in Soil. (Data from Hewitt et al.[19])
    Compound Soil Reporting Limit (mg/kg)
    HPLC (8330) GC (8095)
    HMX 0.04 0.01
    RDX 0.04 0.006
    TNB 0.04 0.003
    TNT 0.04 0.002
    2,6-DNT 0.08 0.002
    2,4-DNT 0.04 0.002
    2-ADNT 0.08 0.002
    4-ADNT 0.08 0.002
    NG 0.1 0.01
    DNB 0.04 0.002
    Tetryl 0.04 0.01
    PETN 0.2 0.016

    References

    1. ^ 1.0 1.1 1.2 Taylor, S., Jenkins, T.F., Bigl, S., Hewitt, A.D., Walsh, M.E. and Walsh, M.R., 2011. Guidance for Soil Sampling for Energetics and Metals (No. ERDC/CRREL-TR-11-15). Report.pdf
    2. ^ 2.0 2.1 2.2 2.3 Hewitt, A.D., Jenkins, T.F., Walsh, M.E., Bigl, S.R. and Brochu, S., 2009. Validation of sampling protocol and the promulgation of method modifications for the characterization of energetic residues on military testing and training ranges (No. ERDC/CRREL-TR-09-6). Engineer Research and Development Center / Cold Regions Research and Engineering Lab (ERDC/CRREL) TR-09-6, Hanover, NH, USA. Report.pdf
    3. ^ 3.0 3.1 3.2 3.3 U.S. Environmental Protection Agency (USEPA), 2006. Method 8330B (SW-846): Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC), Rev. 2. Washington, D.C. Report.pdf
    4. ^ 4.0 4.1 U.S. Environmental Protection Agency (US EPA), 2007. Method 8095 (SW-846): Explosives by Gas Chromatography. Washington, D.C. Report.pdf
    5. ^ Walsh, M.R., Walsh, M.E., Ampleman, G., Thiboutot, S., Brochu, S. and Jenkins, T.F., 2012. Munitions propellants residue deposition rates on military training ranges. Propellants, Explosives, Pyrotechnics, 37(4), pp.393-406. doi: 10.1002/prep.201100105
    6. ^ Walsh, M.R., Walsh, M.E., Hewitt, A.D., Collins, C.M., Bigl, S.R., Gagnon, K., Ampleman, G., Thiboutot, S., Poulin, I. and Brochu, S., 2010. Characterization and Fate of Gun and Rocket Propellant Residues on Testing and Training Ranges: Interim Report 2. (ERDC/CRREL TR-10-13. Also: ESTCP Project ER-1481) Report
    7. ^ 7.0 7.1 Walsh, M.R., Temple, T., Bigl, M.F., Tshabalala, S.F., Mai, N. and Ladyman, M., 2017. Investigation of Energetic Particle Distribution from High‐Order Detonations of Munitions. Propellants, Explosives, Pyrotechnics, 42(8), pp.932-941. doi: 10.1002/prep.201700089 Report.pdf
    8. ^ Hewitt, A.D., Jenkins, T.F., Walsh, M.E., Walsh, M.R. and Taylor, S., 2005. RDX and TNT residues from live-fire and blow-in-place detonations. Chemosphere, 61(6), pp.888-894. doi: 10.1016/j.chemosphere.2005.04.058
    9. ^ Walsh, M.R., Walsh, M.E., Poulin, I., Taylor, S. and Douglas, T.A., 2011. Energetic residues from the detonation of common US ordnance. International Journal of Energetic Materials and Chemical Propulsion, 10(2). doi: 10.1615/IntJEnergeticMaterialsChemProp.2012004956 Report.pdf
    10. ^ Walsh, M.R., Thiboutot, S., Walsh, M.E., Ampleman, G., Martel, R., Poulin, I. and Taylor, S., 2011. Characterization and fate of gun and rocket propellant residues on testing and training ranges (No. ERDC/CRREL-TR-11-13). Engineer Research and Development Center / Cold Regions Research and Engineering Lab (ERDC/CRREL) TR-11-13, Hanover, NH, USA. Report.pdf
    11. ^ 11.0 11.1 Taylor, S., Hewitt, A., Lever, J., Hayes, C., Perovich, L., Thorne, P. and Daghlian, C., 2004. TNT particle size distributions from detonated 155-mm howitzer rounds. Chemosphere, 55(3), pp.357-367. Report.pdf
    12. ^ Pennington, J.C., Jenkins, T.F., Ampleman, G., Thiboutot, S., Brannon, J.M., Hewitt, A.D., Lewis, J., Brochu, S., 2006. Distribution and fate of energetics on DoD test and training ranges: Final Report. ERDC TR-06-13, Vicksburg, MS, USA. Also: SERDP/ESTCP Project ER-1155. Report.pdf
    13. ^ Hewitt, A.D., Jenkins, T.F., Ramsey, C.A., Bjella, K.L., Ranney, T.A. and Perron, N.M., 2005. Estimating energetic residue loading on military artillery ranges: Large decision units (No. ERDC/CRREL-TR-05-7). Report.pdf
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    18. ^ Walsh, M.E., Ramsey, C.A., Collins, C.M., Hewitt, A.D., Walsh, M.R., Bjella, K.L., Lambert, D.J. and Perron, N.M., 2005. Collection methods and laboratory processing of samples from Donnelly Training Area Firing Points, Alaska, 2003 (No. ERDC/CRREL-TR-05-6). Report.pdf
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    See Also