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Bioremediation is the process by which contaminants in soil and/or groundwater are treated biologically, primarily by microorganisms or biomolecules generated and released by the cells. This article overviews key design considerations when planning and implementing a bioremediation remedy.  This article focuses on enhanced in situ bioremediation (EISB) for the anaerobic biodegradation of organic contaminants, particularly '''chlorinated solvents''', in soil and groundwater. However, much of the information provided is applicable to other contaminant types. There are numerous resources for design and implementation of bioremediation applications as well as detailed case studies and performance evaluations. This article provides a summary of key design considerations and parameters for anaerobic biodegradation for treatment of common organic contaminants.
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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)''':
  
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
  
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'''CONTRIBUTOR(S):'''  [[Dr. Samuel Beal]]
  
'''CONTRIBUTOR(S):''' [[Michaye McMaster, M.Sc.]] and [[Leah MacKinnon, M.A.Sc., P. Eng.]]
 
  
 
'''Key Resource(s)''':  
 
'''Key Resource(s)''':  
*[http://www.environmentalrestoration.wiki/images/b/b8/EPA_542_R_13_018.pdf Report pdf Introduction to In Situ Bioremediation of Groundwater]<ref>USEPA, 2013. Introduction to In Situ Bioremediation of Groundwater. [http://www.environmentalrestoration.wiki/images/b/b8/EPA_542_R_13_018.pdf Report pdf]</ref>
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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>
 
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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>
*[http://www.navfac.navy.mil/content/dam/navfac/Specialty%20Centers/Engineering%20and%20Expeditionary%20Warfare%20Center/Environmental/Restoration/er_pdfs/d/navfacexwc-ev-tm-1501-erd-design-201503f.pdf Design Considerations for Enhanced Reductive Dechlorination. TM-NAVFAC-EXWC-EV-1501.]<ref>NAVFAC, 2015. Design considerations for Enhanced Reductive Dechlorination. TM-NAVFAC-EXWC-EV-1501. [http://www.navfac.navy.mil/content/dam/navfac/Specialty%20Centers/Engineering%20and%20Expeditionary%20Warfare%20Center/Environmental/Restoration/er_pdfs/d/navfacexwc-ev-tm-1501-erd-design-201503f.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>
  
 
==Introduction==
 
==Introduction==
Key considerations for designing in situ anaerobic bioremediation applications include the conceptual site model (CSM) and remedial goals, which determine the remedial configuration, amendment types and dosage, longevity of amendments, and modes of delivery. Often, additional site characterization, laboratory microcosm studies, or small-scale field tests are necessary to evaluate the technology and support of the full-scale remedy.  
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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)]]
  
==Conceptual Site Model Interpretation for Design==
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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>.
Successful implementation of anaerobic bioremediation must consider the CSM to develop a robust site-specific design. A CSM is developed and refined during site investigation activities to describe the site conditions, contaminant sources and extent, and the risk they pose to receptors. The following components of a CSM are evaluated to develop the optimal remedial design:
 
*Site geology and hydrogeology
 
*Contaminant distribution and concentrations, including source zones
 
*Groundwater biogeochemical conditions
 
*Site infrastructure (i.e., buildings, below-ground utilities and conduits)
 
*Human health and ecological risks
 
*Remedial goals
 
  
The remedial goals and contaminant distribution are key to defining the target treatment area and remedial configuration. The contaminant type, biogeochemistry, and hydrogeology (aquifer permeability) determines the amendment type and optimal dosage. The site infrastructure and hydrogeology also determine the delivery method, including spacing between injection points, volumes of injectate, and injection frequency.
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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>
[[File:Mackinnon-Article 2- figure 1.PNG|300px|thumbnail|right|Figure 1. Amendment addition for biobarrier.]]
 
  
==Remedial Configurations==
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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).
In-situ anaerobic bioremediation of contaminated soil and groundwater involves introducing '''amendments''' and microbial cultures, if '''bioaugmentation''' is used, into the saturated treatment zone. The two most common treatment configurations include:
 
*A grid of injection and/or extraction points for targeted treatment of a source zone or plume, and
 
*A linear treatment zone, referred to as a biobarrier (Fig. 1), treats contaminants as they flow through the biologically active zone to control plume migration. The biobarrier consists of a row(s) of injection wells/points or a trench filled with solid substrate.  
 
  
The configuration is selected based on the remedial objectives, remedial timeframe, and site conditions and restrictions.
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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"/>.
  
==Delivery Modes==
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{| class="wikitable" style="float: right; text-align: center; margin-left: auto; margin-right: auto;"
''' Amendments''' can be delivered into the subsurface using injection wells (e.g. batch injection, recirculation, push-pull), direct injections (e.g., ''' direct push technology''', hydraulic and pneumatic fracturing) or excavation and backfill. Only liquid amendments (quick release or slow release) can be emplaced through well screens. Direct injections can be used for delivery of all liquid amendments as wells as microscale-particulates (e.g., EHC, ABC+, which contain zero valent iron and solid phase carbon), while biobarriers containing mulch or compost are installed using trenches. The design spacing of direct injection points or wells are based on the estimated radius of influence, which is dependent on the site-specific geology and amendment characteristics.
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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.)
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|-
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! Military Range Type !! Analyte !! Range<br/>(mg/kg) !! Median<br/>(mg/kg) !! RSD<br/>(%)
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|-
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| colspan="5" style="text-align: left;" | '''Discrete Samples'''
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|-
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| Artillery FP || 2,4-DNT || <0.04 – 6.4 || 0.65 || 110
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|-
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| Antitank Rocket || HMX || 5.8 – 1,200 || 200 || 99
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|-
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| Bombing || TNT || 0.15 – 780 || 6.4 || 274
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|-
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| Mortar || RDX || <0.04 – 2,400 || 1.7 || 441
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|-
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| Artillery || RDX || <0.04 – 170 || <0.04 || 454
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|-
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| colspan="5" style="text-align: left;" | '''Incremental Samples*'''
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|-
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| Artillery FP || 2,4-DNT || 0.60 – 1.4 || 0.92 || 26
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|-
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| Bombing || TNT || 13 – 17 || 14 || 17
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|-
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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
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|-
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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.
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|}
  
Amendments can be applied in a passive or active manner to target the contaminant zones.  
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==Incremental Sampling Approach==
*In a passive treatment approach, amendments are typically delivered through injection wells or direct injection points in one injection event.  Natural flow of groundwater is then relied upon to deliver contaminated groundwater to biologically active areas where treatment occurs.  
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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]]
  
*In a semi-passive approach, liquid amendments are injected periodically, with intermittent periods of passive treatment between injection events.  Recirculation may be employed during the active treatment periods, while during the passive treatment periods native flow of groundwater is relied upon for delivery.  
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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.
  
*Active bioremediation approaches for groundwater involve recirculation of dissolved amendments within the targeted saturated zone (Fig. 2). Recirculation may improve substrate distribution in the discrete targeted depth and area, provide hydraulic containment, enhance contaminant/substrate mixing, and accelerate treatment time.
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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)]]
[[File:Mackinnon-Article 2- figure 2.PNG|400px|thumbnail|right|Figure 2. Groundwater recirculation system.]]
 
  
==Amendment Types==
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==Sampling Tools==
Amendments for anaerobic bioremediation include carbon-based electron donors, electron acceptors, nutrients, pH buffers, and microbial cultures. For each type of amendment that is used the critical design considerations in selection include the contaminant type, site geochemical/hydrogeological conditions, and delivery configuration/mode, as well as the amendment solubility, anticipated rate of consumption (or growth in the case of bioaugmentation), longevity, cost, and ability to be distributed in the subsurface. Bench scale testing may be used to confirm the most applicable amendment type and '''amendment dose'''.
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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.
  
===Electron Donors===
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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>]]
Many materials have been used as electron donors for anaerobic reductive bioremediation applications for anaerobic reduction of contaminants such as chlorinated solvents, energetics and perchlorate. These materials are typically classified as quick release compounds (lactate, sodium benzoate, molasses, whey) or slow release compounds (emulsified vegetable oils, Hydrogen Release Compound [HRC], EHC, ABC+, mulch, compost). Quick release compounds are often selected for active approaches to bioremediation where the electron donor may be continually replenished in the target treatment area. Slow release compounds are often selected for passive approaches where the greater longevity is desirable. In some cases, a mixture of amendments will be used; for example, a quick release compound may be used to provide initial rapid bacterial growth and a slow release compound may be used to provide a long-term source of electron donor.
 
  
===Electron Acceptors===
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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.
Electron acceptors such as nitrate, iron(III), or sulfate can be used as amendments for the anaerobic oxidative bioremediation of contaminants such as aromatic hydrocarbons, fuels, and some chloroethenes<ref>Edwards, E. A., Wills, L.E., Reinhard, M., Grbic-Galic, D., 1991. Anaerobic Degradation of Toluene and Xylene by Aquifer Microorganisms under Sulfate-Reducing Conditions. Applied and Environmental Microbiology 58:2663-2666.</ref><ref>Lovley, D.R., 1997. Potential for anaerobic bioremediation of BTEX in petroleum-contaminated aquifers. Journal of Industrial Microbiology and Biotechnology, 18(2-3), pp.75-81. [https://doi.org/10.1038/sj.jim.2900246 doi 10.1038/sj.jim.2900246]</ref><ref>Suflita, J.M. and Sewell, G.W., 1991. Anaerobic biotransformation of contaminants in the subsurface. Environmental Research Brief (USA).</ref><ref>Bradley, P.M. and Chapelle, F.H., 1997. Kinetics of DCE and VC mineralization under methanogenic and Fe (III)-reducing conditions. Environmental Science & Technology, 31(9), pp.2692-2696. [https://doi.org/10.1021/es970110e doi 10.1021/es970110e]</ref>. While these electron acceptors may promote slower kinetics compared to using oxygen, they may be chosen due to higher solubility, ease of delivery, and/or compatibility with existing geochemical conditions. Other considerations when using these electron acceptors include:
 
*Nitrate is highly soluble in water and after oxygen, provides the most energy for the microbial reaction. However, the EPA’s maximum contaminant level (MCL) for nitrate is 10 mg/L in groundwater. Therefore, the concentration and migration of nitrate needs to be carefully managed.
 
*Iron(III) is only slightly soluble in water, but gets reduced to iron(II) which is soluble in water. Water quality thresholds for iron include a secondary MCL guideline for iron of 0.3 mg/L for color, taste and staining effects.
 
*Sulfate is very soluble in water and reduces to sulfide, which typically precipitates with the naturally occurring iron in the subsurface. However, under acidic conditions, the sulfide can become hydrogen sulfide gas, which is toxic to breathe. The secondary MCL of sulfate is 250 mg/L due to taste, but does not present a risk to human health. Some common sulfate amendments include magnesium sulfate (Epsom salts), calcium sulfate (gypsum), and commercially-available products such as Nutrisulfate®.
 
  
===Nutrients===
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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>.
Under natural conditions, typical aquifers typically contain suitable amounts of trace nutrients for microbial growth, however substrate amendments may be used to provide additional nutrients such as nitrogen, phosphorous, sulfur, vitamin B12 and yeast extracts. While these nutrients may be valuable at some sites, there can be disadvantages to using nutrients, particularly at high levels, as the nutrients may precipitate with natural minerals and cause aquifer plugging. Nutrients may also compete for electron donors, when used. Additionally, nutrients such as vitamin B12 can be expensive to apply, and the cost-benefit of these additional amendments must be considered in the design process.
 
  
===pH Buffers===
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==Sample Processing==
The activity of the microorganisms that degrade the target compounds, and in particular the chlorinated volatile organic compound (cVOC)-dechlorinating microorganisms, can be inhibited at low pH (less than 6.0)<ref name="Robinson2009">Robinson, C., Barry, D.A., McCarty, P.L., Gerhard, J.I. and Kouznetsova, I., 2009. pH control for enhanced reductive bioremediation of chlorinated solvent source zones. Science of the Total Environment, 407(16), pp.4560-4573. [http://dx.doi.org/10.1016/j.scitotenv.2009.03.029 doi:10.1016/j.scitotenv.2009.03.029]</ref>. Low groundwater pH can be a result of the geologic materials, contaminant impacts (i.e. acids), or can occur during EISB due to the fermentation of electron donors and/or dehalogenation of cVOCs. The addition of a'''buffer''' (i.e., sodium bicarbonate, calcium carbonate) or base (i.e., magnesium hydroxide) may be required for some EISB applications, to neutralize pre-existing acidic groundwater conditions or to maintain pH above 6.0 during EISB. When buffering is required for an anaerobic bioremediation application it is critical to complete bench scale tests with both groundwater and aquifer solids to confirm the buffer capacity of the site materials.
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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.
  
===Bioaugmentation===
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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.
Adding microbial cultures for '''bioaugmentation''' may be considered at a site when an appropriate population of anaerobic microorganisms is not present or sufficiently active to stimulate complete anaerobic degradation of the existing contaminants. For example, the presence of Dehalococcoides-related microorganisms has been linked to complete dechlorination of PCE and TCE to ethene in the field<ref>Parsons, 2004. Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents. AFCEE, NFEC, ESTCP [http://www.environmentalrestoration.wiki/images/d/d5/AFCEE_Principles_and_Practices.pdf Report pdf]</ref><ref>Major, D.W., McMaster, M.L., Cox, E.E., Edwards, E.A., Dworatzek, S.M., Hendrickson, E.R., Starr, M.G., Payne, J.A. and Buonamici, L.W., 2002. Field demonstration of successful bioaugmentation to achieve dechlorination of tetrachloroethene to ethene. Environmental Science & Technology, 36(23), pp.5106-5116. [https://doi.org/10.1021/es0255711 doi 10.1021/es0255711]</ref><ref>Hendrickson, E.R., Payne, J.A., Young, R.M., Starr, M.G., Perry, M.P., Fahnestock, S., Ellis, D.E. and Ebersole, R.C., 2002. Molecular analysis of Dehalococcoides 16S ribosomal DNA from chloroethene-contaminated sites throughout North America and Europe. Applied and Environmental Microbiology, 68(2), pp.485-495. [https://doi.org/10.1128/aem.68.2.485-495.2002 doi 10.1128/aem.68.2.485-495.2002]</ref><ref>Lendvay, J.M., Löffler, F.E., Dollhopf, M., Aiello, M.R., Daniels, G., Fathepure, B.Z., Gebhard, M., Heine, R., Helton, R., Shi, J. and Krajmalnik-Brown, R., 2003. Bioreactive barriers: a comparison of bioaugmentation and biostimulation for chlorinated solvent remediation. Environmental Science & Technology, 37(7), pp. 1422-1431. [https://doi.org/10.1021/es025985u doi 10.1021/es025985u]</ref>. Commercially available bioaugmentation products that contain these microorganisms include KB-1®, SDC-9™, and Bio-Dechlor Inoculum® Plus.  
 
  
==Amendment Dose==
+
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).
Once the amendments for an application are selected, the quantity, concentration and frequency of amendment addition can be evaluated. To define the amendment dose, the Site conditions are reviewed in terms of remedial objectives (i.e., treatment targets, longevity) to obtain the basis of dosing calculations including dimensions of the targeted subsurface zone and associated pore volume, groundwater velocity, concentrations of terminal electron acceptors (for electron donors), the type of contaminants and geochemical characteristics (e.g., initial redox state, pH). Although conservative designs are typically applied, the potential for producing methane gas or other gases (i.e. hydrogen sulfide) must also be considered, especially in shallow aquifers. As described above, the results from bench scale testing may be used to support this evaluation.
 
  
In the case of electron donors, dosing is based on “electron donor demand” which accounts for consumption of the amendment by treating the target constituent(s) as well as competing electron acceptors. An on-line '''Planning Aqueous Amendment Injection Systems Soluble Substrate Design Tool''' is available from ESTCP for estimating electron donor demand<ref name= "Borden2012">Borden, R.C., Cha, K.Y., Simpkin, T. and Lieberman, M.T., 2012. Development of a Design Tool for Planning Aqueous Amendment Injection Systems Soluble Substrate Design Tool (No. ER-200626). North Carolina State Univ. at Raleigh. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/ER-200626/ER-200626 Report pdf]</ref>, and electron donor vendors may also have design tools to support EISB applications. These calculations can also be used to evaluate the need for and frequency of repeat injection events, which will then be confirmed based on performance monitoring. However, it is important to note that previous applications have shown that the treatment period may be extended beyond the longevity of the amended electron donor as a result of endogenic cell decay of biomass. Thus, the initial biomass growth stimulated by electron donor addition may serve as a secondary source of electron donor<ref>Adamson, D.T. and Newell, C.J., 2009. Support of source zone bioremediation through endogenous biomass decay and electron donor recycling. Bioremediation Journal, 13(1), pp.29-40. [http://dx.doi.org/10.1080/10889860802690539 doi: 10.1080/10889860802690539]</ref>.
+
<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>
 +
<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>
 +
<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>
  
==Milestones, Metrics, and Endpoints==
+
==Analysis==
Common parameters to evaluate the success of bioremediation applications include operational monitoring during implementation (e.g., amendment concentrations, injection rates, injection pressures, achieved volumes) and treatment performance monitoring. The performance monitoring program typically includes the following parameters to evaluate:
+
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.
*the distribution of amendments (e.g., conductivity, turbidity, total organic carbon, volatile fatty acids, methane)
 
*the resulting changes in the geochemistry (e.g., redox, pH, anions, cations)  
 
*associated changes in desired microbiological populations (e.g., molecular and enzyme analyses) using ''' molecular biological tools'''
 
*influence on the target contaminants (i.e., cVOCs and their daughter products), and
 
*confirmation of degradation, and potentially degradation processes, through '''compound specific isotope analysis'''.
 
  
Potential for adverse effects from amendments and/or their '''by-products''' (i.e., methane in soil gas, hydrogen sulfide, metals mobilization) is also evaluated on a site-specific basis. The monitoring plan should be adaptive to accommodate observed changes in groundwater quality at the site. Performance thresholds or triggers should be used to evaluate the performance monitoring results and identify when additional remedial contingencies may be needed to achieve the remedial objectives and/or when the remedy is complete.
+
{| class="wikitable" style="float: center; text-align: center; margin-left: auto; margin-right: auto;"
 
+
|+ 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>)
==Field Demonstrations and Performance==
+
|-
There have been numerous field demonstrations of anaerobic bioremediation documented in publicly available literature and reports, including:
+
! rowspan="2" | Compound
*U.S. EPA Contaminated Site Clean-Up Information (CLU-IN)<ref>USEPA 2016. Anaerobic Bioremediation (Direct) Application.</ref>
+
! colspan="2" | Soil Reporting Limit (mg/kg)
*In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones: Case Studies<ref name= "ITRC2007">ITRC, 2007. In Situ Bioremediation of Chlorinated Ethene DNAPL Source Zones: Case Studies, BioDNAPL-2, 173 pp, 2007. [http://www.environmentalrestoration.wiki/images/5/5a/ITRC-2007-Bioremed_of_Chlorinated_Ethene.pdf Report pdf]</ref>  
+
|-
*ESTCP Demonstrations: Cost and Performance Reports
+
! HPLC (8330)  
**ER-0008: Biodegradation of Dense Non-Aqueous Phase Liquids (DNAPLs) through Bioaugmentation of Source Areas - Dover National Test Site<ref>ESTCP, 2008. Biodegradation of Dense Non-Aqueous Phase Liquids (DNAPLs) through Bioaugmentation of Source Areas - Dover National Test Site, Dover, Delaware: ESTCP Cost and Performance Report. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Persistent-Contamination/ER-200008/ER-200008 ESTCP Project ER-0008]</ref>
+
! GC (8095)
**ER-0221: Edible Oil Barriers for Treatment of Chlorinated Solvent Groundwater<ref>Lieberman, M.T. and Borden, R.C., 2009. Edible Oil Barriers for Treatment of Chlorinated Solvent Contaminated Groundwater. Solutions Industrial and Environmental Services Raleigh NC. [http://www.environmentalrestoration.wiki/images/4/45/PRB-ER-0221-FR.pdf Report pdf]</ref>
+
|-
**ER-200219: Comparative Demonstration of Active and Semi-Passive In Situ Bioremediation Approaches for Perchlorate Impacted Groundwater: Active In Situ Bioremediation Demonstration (Aerojet Facility)<ref name= "Cox2012">Cox, E. and Krug, T., 2012. Comparative Demonstration of Active and Semi-Passive In Situ Bioremediation Approaches for Perchlorate Impacted Groundwater: Active In Situ Bioremediation Demonstration (Aerojet Facility) ESTCP Project ER-200219. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-200219 ER-200219]</ref>
+
| HMX || 0.04 || 0.01
**ER-200627: Loading Rate and Impacts of Substrate Delivery for Enhanced Anaerobic Bioremediation<ref name= "ESTCP2010LR">ESTCP, 2010. Loading Rate and Impacts of Substrate Delivery for Enhanced Anaerobic Bioremediation. ESTCP Project ER-200627, 90 pp. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/ER-200627 ER-200627]</ref>
+
|-
*Regulatory / Guidance Documents<ref name="Robinson2009"/><ref name= "Borden2012"/><ref name= "ITRC2007"/><ref name= "Cox2012"/><ref name= "ESTCP2010LR"/>
+
| RDX || 0.04 || 0.006
 
+
|-
==Summary & Conclusions==
+
| [[Wikipedia: 1,3,5-Trinitrobenzene | TNB]] || 0.04 || 0.003
The design of a successful anaerobic bioremediation application depends on a strong understanding of the CSM and remedial goals for the site. Bioremediation can be adapted to work in a wide range of site conditions, and the amendment selection and delivery methods are designed to be effective for the site-specific hydrogeologic conditions, contaminants, biogeochemistry, and infrastructure constraints to satisfy the remedial goals.
+
|-
 +
| TNT || 0.04 || 0.002
 +
|-
 +
| [[Wikipedia: 2,6-Dinitrotoluene | 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
 +
|-
 +
| [[Wikipedia: Dinitrobenzene | DNB ]] || 0.04 || 0.002
 +
|-
 +
| [[Wikipedia: Tetryl | Tetryl ]]  || 0.04 || 0.01
 +
|-
 +
| [[Wikipedia: Pentaerythritol tetranitrate | PETN ]] || 0.2 || 0.016
 +
|}
  
 
==References==
 
==References==
 
 
<references/>
 
<references/>
  
 
==See Also==
 
==See Also==
*[https://clu-in.org/techfocus/default.focus/sec/Bioremediation/cat/Anaerobic_Bioremediation_(Direct)/p/2  Bioremediation]
+
*[https://itrcweb.org/ Interstate Technology and Regulatory Council]
*[https://clu-in.org/download/contaminantfocus/dnapl/Treatment_Technologies/epa_2006_engin_issue_bio.pdf In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites]
+
*[http://www.hawaiidoh.org/tgm.aspx Hawaii Department of Health]
*[https://clu-in.org/download/remed/Bioaug2005.pdf Bioaugmentation For Remediation of Chlorinated Solvents]
+
*[http://envirostat.org/ Envirostat]
*[https://frtr.gov/costperformance/pdf/remediation/principles_and_practices_bioremediation.pdf Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents]
 
*[http://www.itrcweb.org/Team/Public?teamID=23 Bioremediation of DNAPLs]
 
*[http://www.itrcweb.org/Team/Public?teamID=33 In Situ Bioremediation]
 
*[http://navfac.navy.mil/content/dam/navfac/Specialty%20Centers/Engineering%20and%20Expeditionary%20Warfare%20Center/Environmental/Restoration/er_pdfs/b/navfac-ev-fs-biorem-dnapl-20120412.pdf Using Bioremediation in Dense Non-Aqueous Phase Liquid Source Zones]
 
*[http://navfac.navy.mil/content/dam/navfac/Specialty%20Centers/Engineering%20and%20Expeditionary%20Warfare%20Center/Environmental/Restoration/er_pdfs/d/navfacexwc-ev-tm-1501-erd-design-201503f.pdf Technical Memorandum - Design Considerations for Enhanced Reductive Dechlorination]
 
*[https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/ER-200626 Development of Design Tools for Planning Aqueous Amendment Injection Systems]
 

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
    14. ^ 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). Report.pdf
    15. ^ 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. Report.pdf
    16. ^ 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. Report.pdf
    17. ^ 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. doi: 10.1016/S0045-6535(02)00528-3
    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
    19. ^ 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. Report.pdf

    See Also