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[[wikipedia: Halorespiration | Organohalide-respiring bacteria]] are generally sensitive to pH.  Reductive dechlorination of tetrachloroethene (PCE) to trichloroethene (TCE) and then to cis-1,2-dichloroethene(cDCE) can occur at a pH as low as 5.5.  However, rates of cDCE reduction to vinyl chloride (VC) and then to ethene are reduced below a pH of 6.0.  For efficient dechlorination to non-toxic end products, aquifer pH should be maintained above 6.0 during [[Bioremediation - Anaerobic | enhanced reductive dechlorination (ERD)]].
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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.  
 
 
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
  
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'''Related Article(s)''':
  
'''Related Article(s):'''
 
*[[Bioremediation - Anaerobic| In Situ Anaerobic Bioremediation]]
 
*[[Biodegradation - Reductive Processes]]
 
*[[Design Tool for Estimating Base Required during ERD]]
 
*[[pH Buffering in Aquifers]]
 
*[[Chlorinated Solvents]]
 
  
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'''CONTRIBUTOR(S):'''  [[Dr. Samuel Beal]]
  
'''CONTRIBUTOR(S):''' [[Dr. Robert Borden, P.E.]]
 
  
 
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'''Key Resource(s)''':
'''Key Resource(s):'''
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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>
*[[media:2012-Li_yixuan-MASc_thesis_Adaptation_of_KB-1_to_Acidic_Environments.pdf| Adaptation of a Dechlorinating Culture, KB-1, to Acidic Environments.]]<ref name= "Li2012">Li, Y.X., 2012. Adaptation of a Dechlorinating Culture, KB-1, to Acidic Environments. M.S. Thesis, University of Toronto, Toronto, ON, Canada. [[media:2012-Li_yixuan-MASc_thesis_Adaptation_of_KB-1_to_Acidic_Environments.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>  
*[https://doi.org/10.1021/acs.est.7b01510| Organohalide respiration with chlorinated ethenes under low pH conditions]]<ref name= "Yang2017a">Yang, Y., Cápiro, N.L., Marcet, T.F., Yan, J., Pennell, K.D. and Loffler, F.E., 2017. Organohalide respiration with chlorinated ethenes under low pH conditions. Environmental Science & Technology, 51(15), pp.8579-8588. [https://doi.org/10.1021/acs.est.7b01510 doi: 10.1021/acs.est.7b01510]</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>
*[[media:2017b-Yang-Resilience_and_recovery_of_Dehalococcoides....pdf| Resilience and recovery of Dehalococcoides mccartyi following low pH exposure]]<ref name= "Yang2017b">Yang, Y., Cápiro, N.L., Yan, J., Marcet, T.F., Pennell, K.D. and Löffler, F.E., 2017. Resilience and recovery of Dehalococcoides mccartyi following low pH exposure. FEMS microbiology ecology, 93(12), p.fix130. doi: 10.1093/femsec/fix130. [[media:2017b-Yang-Resilience_and_recovery_of_Dehalococcoides....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==
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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)]]
  
[[Bioremediation - Anaerobic | Enhanced reductive dechlorination (ERD)]] is commonly used to treat chlorinated solvents and related contaminants in groundwater by providing a fermentable organic substrate to serve as both an electron donor and a carbon source to stimulate microbially mediated [[Biodegradation - Reductive Processes| reductive dechlorination]]<ref>AFCEE, NFESC, ESTCP, 2004. Principles and Practices of Enhanced Anaerobic Bioremediation of Chlorinated Solvents. Parsons Corporation. Air Force Center for Environmental Excellence, Naval Facilities Engineering Service Center, and Environmental Security Technology Certification Program. [[media:AFCEE_Principles_and_Practices.pdf| Report PDF]]</ref><ref>ITRC, 2008. Enhanced attenuation of chlorinated organics (EACO-1): A decision framework for site transition. Washington, D.C.: Interstate Technology & Regulatory Council, Enhanced Attenuation: Chlorinated Organics Team[[media:2008-ITRC-EACO_1.pdf| Report pdf]]</ref><ref>Stroo, H.F., West, M.R., Kueper, B.H., Borden, R.C., Major, D.W. and Ward, C.H., 2014. In Situ Bioremediation Of Chlorinated Ethene Source Zones. In Chlorinated Solvent Source Zone Remediation (pp. 395-457). Springer New York. [http://dx.doi.org/10.1007/978-1-4614-6922-3_12 doi:10.1007/978-1-4614-6922-3_12]</ref>.  During ERD, the pH may decline as hydrochloric acid (HCl) is produced during reductive dechlorination<ref>Vogel, T.M. and McCarty, P.L., 1985. Biotransformation of tetrachloroethylene to trichloroethylene, dichloroethylene, vinyl chloride, and carbon dioxide under methanogenic conditions. Applied and Environmental Microbiology, 49(5), pp.1080-1083.</ref> <ref>Mohn, W.W. and Tiedje, J.M., 1992. Microbial reductive dehalogenation. Microbiological reviews, 56(3), pp.482-507.</ref> and carbonic acid and organic acids are produced by substrate fermentation.  However, dechlorinating bacteria appear to be particularly sensitive to pH changes with dechlorination of cDCE and VC to ethene completely inhibited at a pH of 5.5<ref name= "Rowlands2004">Rowlands, D., 2004.  Development of optimal pH for degradation of chlorinated solvents by the KB-1TM anaerobic bacterial culture.  M.S. Thesis, University of Guelph, Guelph, ON, Canada</ref><ref name= "Vainberg2006">Vainberg, S., Steffan, R.J., Rogers, R., Ladaa, T., Pohlmann, D. and Leigh, D., 2006.  Production and application of large-scale cultures for bioaugmentation. Proc 5th Internat Conf Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, USA. May 22-25.  Paper No. A-50.</ref><ref name= "Eaddy2008">Eaddy, A., 2008. Scale-up and characterization of an enrichment culture for bioaugmentation of the P-area chlorinated ethene plume at the Savannah River site. M.S. Thesis, Clemson University, Clemson, SC, USA. [[media:2008-Eaddy-Scale_Up_and_Characterization_Thesis_Final_pdf.pdf| Report.pdf]]</ref><ref name= "Yang2017a"/>, resulting in a significant decline in degradation rates<ref>Duhamel, M., Wehr, S.D., Yu, L., Rizvi, H., Seepersad, D., Dworatzek, S., Cox, E.E. and Edwards, E.A., 2002. Comparison of anaerobic dechlorinating enrichment cultures maintained on tetrachloroethene, trichloroethene, cis-dichloroethene and vinyl chloride. Water Research, 36(17), pp.4193-4202. [https://doi.org/10.1016/s0043-1354(02)00151-3 doi: 10.1016/S0043-1354(02)00151-3]</ref><ref>McCarty, P.L., Chu, M.Y. and Kitanidis, P.K., 2007. Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater. European Journal of Soil Biology, 43(5-6), pp.276-282. doi: 10.1016/j.ejsobi.2007.03.004. [[media: 2007-McCarty-Electron_donor_and_pH_relationships....pdf| Report.pdf]]</ref>.
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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>.
  
==Effect of pH on Bioremediation Processes==
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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>
Many biological processes are sensitive to pH.  Most microorganisms important for subsurface bioremediation function most efficiently in near neutral conditions<ref name= "Lowe1993">Lowe, S.E., Jain, M.K. and Zeikus, J.G., 1993. Biology, ecology, and biotechnological applications of anaerobic bacteria adapted to environmental stresses in temperature, pH, salinity, or substrates. Microbiological reviews, 57(2), pp.451-509</ref>. Low pH can interfere with pH homeostasis or increase the solubility of toxic metals<ref>Slonczewski, J.L., 2009 Stress Responses: pH, In Encyclopedia of Microbiology (3rd Ed.), Editor-in-Chief: Schaechter, M., Academic Press: Oxford Vol 5. pp. 477-484</ref>. Microorganisms can expend cellular energy to maintain homeostasis, or conditions in the cytoplasm and periplasm may change in response to external changes in pH<ref>Foster, J.W., 1999. When protons attack: microbial strategies of acid adaptation. Current opinion in microbiology, 2(2), pp.170-174. [https://doi.org/10.1016/s1369-5274(99)80030-7 doi: 10.1016/S1369-5274(99)80030-7]</ref>. Some anaerobes have adapted to low pH conditions through alterations in carbon and electron flow, cellular morphology, membrane structure, and protein synthesis<ref name= "Lowe1993"/>.
 
  
There is some evidence that organohalide-respiring bacteria are particularly sensitive to changes in pH. Pure cultures and consortia of organohalide-respiring microorganisms show highest dechlorination rates at circumneutral pH<ref name= "Yang2017a"/>.  Reduction of cDCE to VC to ethene is primarily carried out by strains of ''Dehalococcoides mccartyi (Dhc)''<ref name = "Löffler2013">Löffler, F.E., Yan, J., Ritalahti, K.M., Adrian, L., Edwards, E.A., Konstantinidis, K.T., Müller, J.A., Fullerton, H., Zinder, S.H. and Spormann, A.M., 2013. Dehalococcoides mccartyi gen. nov., sp. nov., obligately organohalide-respiring anaerobic bacteria relevant to halogen cycling and bioremediation, belong to a novel bacterial class, Dehalococcoidia classis nov., order Dehalococcoidales ord. nov. and family Dehalococcoidaceae fam. nov., within the phylum Chloroflexi. International journal of systematic and evolutionary Microbiology, 63(2), pp.625-635. doi: 10.1099/ijs.0.034926-0 [media: 2013-Loffler-Dehalococcoides_mccartyi_gen._nov....pdf| Report.pdf]</ref>.  Growth and dechlorination by ''Dhc'' occurs between pH 6 and 8, with highest activity measured between pH 6.9 and 7.5<ref name = "Löffler2013"/>
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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).
  
Table 1 shows the range and optimum pH for growth of bacteria that reduce PCE to TCE and cDCE.  Zhuang and Pavlostathis (1995)<ref>Zhuang, P. and Pavlostathis, S.G., 1995. Effect of temperature, pH and electron donor on the microbial reductive dechlorination of chloroalkenes. Chemosphere, 31(6), pp.3537-3548. [https://doi.org/10.1016/0045-6535(95)00204-L doi:10.1016/0045-6535(95)00204-L]</ref> found that neutral pH was optimum for reductive dechlorination by a methanogenic mixed culture capable of dechlorinating PCE to VC.  Vainberg et al. (2006)<ref name= "Vainberg2006"/> reported an optimum pH of 6.0-6.8 for dechlorination of PCE by the SDC-9<sup>™</sup> bioaugmentation culture.  Dechlorination of PCE and TCE to cDCE can occur at pH down to 5.5<ref>Vainberg, S., Condee, C.W. and Steffan, R.J., 2009. Large-scale production of bacterial consortia for remediation of chlorinated solvent-contaminated groundwater. Journal of Industrial Microbiology & Biotechnology, 36(9), pp.1189-1197. [https://doi.org/10.1007/s10295-009-0600-5 doi: 10.1007/s10295-009-0600-5]</ref>.
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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;"
'''Table 1. Range and optimum pH for growth of pure cultures reducing PCE '''
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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.)
{|- class="wikitable" style="float:left; margin: left; width: 65%;"  
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|-
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! Military Range Type !! Analyte !! Range<br/>(mg/kg) !! Median<br/>(mg/kg) !! RSD<br/>(%)
 
|-
 
|-
!style="background-color:#CEE0F2;" | Organism!!style="background-color:#CEE0F2;"|pH Range!!style="background-color:#CEE0F2;"| pH Optimum!!style="background-color:#CEE0F2;"|Reference
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| colspan="5" style="text-align: left;" | '''Discrete Samples'''
 
|-
 
|-
| ''Dehalobacter restrictus'' PER- K23 || 6.5 to 8.0 ||6.8 to 7.6 || Holliger et al., 1998<ref>Holliger, C., Hahn, D., Harmsen, H., Ludwig, W., Schumacher, W., Tindall, B., Vazquez, F., Weiss, N. and Zehnder, A.J., 1998. Dehalobacter restrictus gen. nov. and sp. nov., a strictly anaerobic bacterium that reductively dechlorinates tetra-and trichloroethene in an anaerobic respiration. Archives of Microbiology, 169(4), pp.313-321. [https://doi.org/10.1007/s002030050577  doi: 10.1007/s002030050577]</ref>
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| Artillery FP || 2,4-DNT || <0.04 – 6.4 || 0.65 || 110
 
|-
 
|-
| ''Sulfurospirillum multivorans'' || 5.5 to 8.0 || 7.0 to 7.5|| Neumann et al., 1994<ref>Neumann, A., Scholz-Muramatsu, H. and Diekert, G., 1994. Tetrachloroethene metabolism of Dehalospirillum multivorans. Archives of Microbiology, 162(4), pp.295-301. ISSN: 0302-8933, 1432-072X [https://doi.org/10.1007/bf00301854 doi: 10.1007/BF00301854]</ref>; Scholz-Muramatsu et al., 1995<ref>Scholz-Muramatsu, H., Neumann, A., Meßmer, M., Moore, E. and Diekert, G., 1995. Isolation and characterization of Dehalospirillum multivorans gen. nov., sp. nov., a tetrachloroethene-utilizing, strictly anaerobic bacterium. Archives of Microbiology, 163(1), pp.48-56. [https://doi.org/10.1007/bf00262203 doi: 10.1007/BF00262203]</ref>; Yang, 2017a<ref name= "Yang2017a"/>
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| Antitank Rocket || HMX || 5.8 – 1,200 || 200 || 99
 
|-
 
|-
| ''Desulfitobacterium dehalogenans'' JW/IU-DC-1 || 6.0 to 9.0 || 7.5 ||Utkin et al., 1994<ref>Utkin, I., Woese, C. and Wiegel, J., 1994. Isolation and characterization of Desulfitobacterium dehalogenans gen. nov., sp. nov., an anaerobic bacterium which reductively dechlorinates chlorophenolic compounds. International Journal of Systematic and Evolutionary Microbiology, 44(4), pp.612-619. [https://doi.org/10.1099/00207713-44-4-612 doi: 10.1099/00207713-44-4-612]</ref>
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| Bombing || TNT || 0.15 – 780 || 6.4 || 274
 
|-
 
|-
| ''Desulfitobacterium'' sp. PCE-1 || 7.2 to 7.8 ||7.2 || Gerritse et al., 1996<ref>Gerritse, J., Renard, V., Gomes, T.P., Lawson, P.A., Collins, M.D. and Gottschal, J.C., 1996. Desulfitobacterium sp. strain PCE1, an anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene or ortho-chlorinated phenols. Archives of microbiology, 165(2), pp.132-140. [https://doi.org/10.1007/s002030050308 doi: 10.1007/s002030050308]</ref>
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| Mortar || RDX || <0.04 – 2,400 || 1.7 || 441
 
|-
 
|-
| ''Desulfitobacterium dichloroeliminans'' DCA1|| ||7.2 to 7.8 || Fogel et al., 2009<ref>Fogel, S., Findlay, M., Folsom, S. and Kozar, M., 2009. The importance of pH in reductive dechlorination of chlorinated solvents. In Proceedings Tenth International In Situ and On-Site Bioremediation Symposium, Baltimore, MD, USA, May(pp. 5-8)</ref>
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| Artillery || RDX || <0.04 – 170 || <0.04 || 454
 
|-
 
|-
| ''Desulfuromonus chloroethenica TT4B''|| 6.5 to 7.4 || 7.4 ||Krumholz el al., 1996<ref>Krumholz, L.R., Sharp, R. and Fishbain, S.S., 1996. A freshwater anaerobe coupling acetate oxidation to tetrachloroethylene dehalogenation. Applied and Environmental Microbiology, 62(11), pp.4108-4113. [https://doi.org/10.1128/aem.01380-18 doi:10.1128/AEM.01380-18]</ref>;Krumholz, 1997<ref>Krumholz, L.R., 1997. Desulfuromonas chloroethenica sp. nov. uses tetrachloroethylene and trichloroethylene as electron acceptors. International Journal of Systematic and Evolutionary Microbiology, 47(4), pp.1262-1263. [https://doi.org/10.1099/00207713-47-4-1262 doi: 10.1099/00207713-47-4-1262]</ref>
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| colspan="5" style="text-align: left;" | '''Incremental Samples*'''
 
|-
 
|-
|''Desulfomonile tiedjei'' DCB-1 ||6.5 to 7.8 ||6.8 to 7.0 ||DeWeerd et al., 1990<ref>DeWeerd, K.A., Mandelco, L., Tanner, R.S., Woese, C.R. and Suflita, J.M., 1990. Desulfomonile tiedjei gen. nov. and sp. nov., a novel anaerobic, dehalogenating, sulfate-reducing bacterium. Archives of Microbiology, 154(1), pp.23-30</ref>
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| Artillery FP || 2,4-DNT || 0.60 – 1.4 || 0.92 || 26
 
|-
 
|-
|''Desulfuromonas michiganensis'' sp. Nov || 6.8 to 8.0|| 7.0 to 7.5 ||Sung et al., 2003<ref>Sung, Y., Ritalahti, K.M., Sanford, R.A., Urbance, J.W., Flynn, S.J., Tiedje, J.M. and Löffler, F.E., 2003. Characterization of two tetrachloroethene-reducing, acetate-oxidizing anaerobic bacteria and their description as Desulfuromonas michiganensis sp. nov. Applied and Environmental Microbiology, 69(5), pp.2964-2974. doi 10.1128/AEM.69.5.2964–2974.2003.[[media:2003-Sung-characterization_of_two_tetrachloroethene-reducing....pdf| Report.pdf]]</ref>
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| Bombing || TNT || 13 – 17 || 14 || 17
 
|-
 
|-
|''Geobacter lovleyi'' SZ|| || 6.5 to 7.2|| Sung et al., 2006<ref>Sung, Y., Fletcher, K.E., Ritalahti, K.M., Apkarian, R.P., Ramos-Hernández, N., Sanford, R.A., Mesbah, N.M. and Löffler, F.E., 2006. Geobacter lovleyi sp. nov. strain SZ, a novel metal-reducing and tetrachloroethene-dechlorinating bacterium. Applied and Environmental Microbiology, 72(4), pp.2775-2782. [https://doi.org/10.1128/aem.72.4.2775-2782.2006 doi: 10.1128/AEM.72.4.2775-2782.2006]</ref>
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| Artillery/Bombing || RDX || 3.9 – 9.4 || 4.8 || 38
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|-  
 +
| Thermal Treatment || HMX || 3.96 – 4.26 || 4.16 || 4
 
|-
 
|-
|colspan = "12"|(adapted from Damborský, 1999<ref>Damborský, J., 1999. Tetrachloroethene-dehalogenating bacteria. Folia microbiologica, 44(3), pp.247-262. [https://doi.org/10.1007/bf02818543 doi: 10.1007/BF02818543]</ref>; Yang et al. 2017a<ref name= "Yang2017a"/>)
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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.
 
|}
 
|}
  
<BR CLEAR="right">
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==Incremental Sampling Approach==
==Impact on Dechlorination Rates==
+
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.
Lacroix et al. (2014)<ref name= "Lacroix2014">Lacroix, E., Brovelli, A., Barry, D.A. and Holliger, C., 2014. Use of silicate minerals for pH control during reductive dechlorination of chloroethenes in batch cultures of different microbial consortia. Applied and environmental microbiology, pp.AEM-00493. [https://doi.org/10.1128/aem.00493-14 doi: 10.1128/AEM.00493-14]</ref> examined the effect of pH on dechlorination rates for several organohalide-respiring consortia including SL2-PCEa, SL2-PCEb, AQ-1, and PM. Dechlorination rates as a function of pH (R<sub>pH</sub>) were fit to the relationship.
+
[[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]]
[[File:Borden1w2 Eq 1.PNG]]
 
  
where R<sub>max</sub>  is the maximum dechlorination rate at the optimal pH (pH<sub>opt</sub>), and n and σ are empirical fitting parameters (Table 2).  Graphs of relative dechlorination rate (R<sub>pH</sub> / R<sub>max</sub>) are shown in Figure 1.  Dechlorination of PCE to cDCE can continue at pH below 5.5. However, dechlorination of cDCE to VC and VC to ethene is severely inhibited below a pH of 5.5.
+
DUs can vary in shape (Figure 4), size, number of increments, and number of replicates according to a project’s data quality objectives.
  
[[File:Borden1w2 Table 2.PNG|left| thumbnail|600 px| (from Lacroix et al. 2014)<ref name= "Lacroix2014"/>]]
+
[[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:Borden1w2 Figure1.png|left|thumbnail| 600 px|Figure 1. Relative Dechlorination Rates (R<sub>pH</sub> /R<sub>max</sub>) versus pH for Consortia SL2-PCEa, SL2-PCEb, AQ-1, and PM (adapted from Lacroix et al. 2014)<ref name= "Lacroix2014"/>. ]]
+
==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<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.
  
<BR CLEAR="right">
+
[[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>]]
==Low pH Tolerant Enrichments==
 
Multiple researchers have attempted to develop enrichment cultures capable of complete dechlorination of PCE and TCE to ethene at low pH. However, to date, these attempts have had only modest success.
 
  
Rowlands (2004) <ref name= "Rowlands2004"/> reported that the KB-1<sup>™</sup> bioaugmentation culture has an optimal range of 6.0-8.3 and is completely inhibited below pH~5.0.  Li (2012)<ref name= "Li2012"/> found that rates of VC reduction to ethene by a KB-1 culture declined by a factor of two as the pH was reduced from 7 to 6.  Ethene production rates declined slowly over time and multiple degradation cycles. The decline in ethene production rates was accompanied by a decline of ''Dehalococcoides (Dhc) '' numbers, increase in methanogens, and a shift in total electron equivalents consumed in dechlorination towards methanogenesis. In methanol fed pH 6 cultures, ethene production rates slowly increased over hundreds of days, with one culture showing sustained VC dechlorination at pH 5.7 (Li, 2012)<ref name= "Li2012"/>.
+
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.
  
Using a bioaugmentation culture enriched from Savannah River Site aquifer material Eaddy (2008)<ref name= "Eaddy2008"/> found that dechlorination of PCE and TCE slowed at a pH of 6.0 with increased accumulation of cDCE and VC. At pH 5.5, reduction of cDCE to VC and VC to ethene was completely inhibited.   
+
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>.
  
Yang (2017a)<ref name= "Yang2017a"/> found that various dechlorinating pure cultures and the BDI consortium showed the highest dechlorination rates at circumneutral pH.  ''Sulfurospirillum multivorans'' was the only organisms identified that dechlorinated PCE to cDCE at pH 5.5.  Yang (2016)<ref>Yang, Y., 2016. Bioremediation of Chlorinated Ethenes: pH Effects, Novel Dechlorinators and Decision-Making Tools. Ph.D. Dissertation, University of Tennessee, Knoxville, TN, USA. [[media:2016-Yang-_pH_effects_on_dechlorination.pdf| Report.pdf]]</ref> and Yang et al. (2017a)<ref name= "Yang2017a"/> found that only one enrichment culture containing ''Desulfovibrio, Sulfurospirillum'', and ''Megasphaera'' showed dechlorination of PCE to cDCE after repeated transfers at pH 5.5. After 40-days exposure to pH=5.5, ''Dhc'' lost the ability to dechlorinate VC to ethene (Yang et al. 2017b)<ref name= "Yang2017b"/>.  
+
==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%<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.
  
Overall, these results indicate that: (a) dechlorination rates are highest at circumneutral pH; (b) certain microorganisms can grow while dechlorinating PCE and TCE at pH values of 5.5 and lower; and (c) some ''Dhc''-containing consortia can dechlorinate cDCE and VC to ethene during short-term exposure to pH 5.5. However, at pH 5.5, the consortia do not grow and gradually lose their ability to dechlorinate VC to ethene. As a result, complete dechlorination to ethene will be inhibited at low pH. In addition, several groups are continuing work on development of improved enrichment cultures that are effective at low pH.
+
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.
  
==Summary==
+
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).
  
Acids are produced during ERD that can cause pH to decline, inhibiting rapid dechlorination. Reduction of PCE to TCE to cDCE can occur at pH down to 5.5 or lower. However, rates of cDCE reduction to VC to ethene are reduced below a pH of 6.0. For efficient dechlorination to non-toxic end products, the aquifer pH should be maintained above 6.0 during ERD.
+
<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>
 +
 
 +
==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.
 +
 
 +
{| 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>)
 +
|-
 +
! rowspan="2" | Compound
 +
! colspan="2" | Soil Reporting Limit (mg/kg)
 +
|-
 +
! HPLC (8330)
 +
! GC (8095)
 +
|-
 +
| HMX || 0.04 || 0.01
 +
|-
 +
| RDX || 0.04 || 0.006
 +
|-
 +
| [[Wikipedia: 1,3,5-Trinitrobenzene | TNB]] || 0.04 || 0.003
 +
|-
 +
| 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==
*[http://www.siremlab.com/kb-1-kb-1-plus/ Low pH Bioaugmentation Cultures]  
+
*[https://itrcweb.org/ Interstate Technology and Regulatory Council]
*[https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-2129 Secondary Impacts of In Situ Remediation on Groundwater Quality and Post-Treatment Management Strategies]
+
*[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
    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