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This article reviews recent results on the toxicology of nitroguanidine (NQ), 2,4-dinitroanisole (DNAN), and nitrotriazelone (3-nitro-1,2,4-triazol-5-one, NTO).
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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>
  
'''Related Articles''':
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'''Related Article(s)''':  
  
'''Key Resource(s):'''
 
  
==Introduction==
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'''CONTRIBUTOR(S):'''  [[Dr. Samuel Beal]]
The US military is replacing many of traditional explosives with Insensitive Munitions (IM) to reduce risks of accidental detonation. Since these IMX materials have not been in common use, considerable effort has been focused on understanding the toxicology of these materials. Some insensitive munition formulations use a combination of materials including nitroguanidine (NQ), 2,4-dinitroanisole (DNAN), and nitrotriazelone (3-nitro-1,2,4-triazol-5-one, NTO) and RDX.  
 
  
==2,4-Dinitroanisole (DNAN) Toxicity==
 
<u>Mammalian toxicity</u> - Oral toxicity of DNAN is similar to other nitroaromatics<ref name= "Dodd2002">Dodd, D.E. and McDougal, J.N., 2002. Recommendation of an occupational exposure level for PAX-21. AFRL-HE-WP-TR-2001-0103. Man-Tech Geo-Centers Joint Venture, Operational Toxicology Branch (AFRL/HEST). U.S. Air Force Armstrong Laboratory. Wright-Patterson Air Force Base, OH.</ref>. The median lethal dose (LD<sub>50</sub>, oral) in rats was 199 mg/kg in both sexes. Clinical signs of toxicity included decreased activity, breathing abnormalities, salivation, and soft stools<ref name="Dodd2002"/>. Lent et al. reported an oral Approximate Lethal Dose (ALD) of 300 mg/kg in rats<ref>USAPHC, Lent, E.M., Crouse, L.C., Hanna, T. and Wallace, S.M., 2012. The subchronic oral toxicity of 2, 4-dinitroanisole (DNAN) in rats (No. USAPHC-87-XE-0DBP-10). Army Public Health Command Aberdeen Proving Ground MD. [http://www.environmentalrestoration.wiki/images/0/03/USAPCH-Lent-2012--Tox_Study_no._87-XE-0DBP-10.pdf Report pdf]</ref>. After 14 days of dosing, the primary non-lethal adverse events suggested that the nitro groups were causing anemia.
 
  
<u>Genotoxicity</u> - Genotoxicity testing of DNAN has had mixed results. DNAN tested positive in the Ames Salmonella histidine reversion test in strain TA100 without activation<ref>McMahon, R.E., Cline, J.C. and Thompson, C.Z., 1979. Assay of 855 test chemicals in ten tester strains using a new modification of the Ames test for bacterial mutagens. Cancer Research, 39(3), pp.682-693. [http://www.environmentalrestoration.wiki/images/1/1c/McMahon-1979-Asasy_of_855_test_chemicals_in_ten_tester_strains....pdf Report pdf]</ref><ref>Chiu, C.W., Lee, L.H., Wang, C.Y. and Bryan, G.T., 1978. Mutagenicity of some commercially available nitro compounds for Salmonella typhimurium. Mutation Research/Genetic Toxicology, 58(1), pp.11-22. [http://dx.doi.org/10.1016/0165-1218(78)90090-3 doi:10.1016/0165-1218(78)90090-3]</ref>. DNAN tested negative in Chinese Hamster Ovary (CHO) cells (AS52/XPRT) at concentrations up to 1.0 mg/ml with and without S9 activation<ref>Dodd, D.E., S. Sharma, and G.M. Hoffman. 2002. Genotoxicity and 90-day developmental toxicity studies on an explosive formulation. Toxicologist 66:267</ref>. DNAN genotoxicity was negative in the in vivo mouse micronucleus assay at exposures of 10-90 mg/kg in both males and females<ref name= "Dodd2002"/>.
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'''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>
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*[[Media:Hewitt-2009 ERDC-CRREL TR-09-6.pdf| Report.pdf | Validation of Sampling Protocol and the Promulgation of Method Modifications for the Characterization of Energetic Residues on Military Testing and Training Ranges]]<ref name= "Hewitt2009">Hewitt, A.D., Jenkins, T.F., Walsh, M.E., Bigl, S.R. and Brochu, S., 2009. Validation of sampling protocol and the promulgation of method modifications for the characterization of energetic residues on military testing and training ranges (No. ERDC/CRREL-TR-09-6). Engineer Research and Development Center / Cold Regions Research and Engineering Lab (ERDC/CRREL) TR-09-6, Hanover, NH, USA. [[Media:Hewitt-2009 ERDC-CRREL TR-09-6.pdf | Report.pdf]]</ref>
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*[[media:Epa-2006-method-8330b.pdf| U.S. EPA SW-846 Method 8330B: Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC)]]<ref name= "USEPA2006M">U.S. Environmental Protection Agency (USEPA), 2006. Method 8330B (SW-846): Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC), Rev. 2. Washington, D.C. [[media:Epa-2006-method-8330b.pdf | Report.pdf]]</ref>
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*[[media:Epa-2007-method-8095.pdf | U.S. EPA SW-846 Method 8095: Explosives by Gas Chromatography.]]<ref name= "USEPA2007M">U.S. Environmental Protection Agency (US EPA), 2007. Method 8095 (SW-846): Explosives by Gas Chromatography. Washington, D.C. [[media:Epa-2007-method-8095.pdf| Report.pdf]]</ref>
  
<u>Ecotoxicity</u> - Administration of DNAN to Japanese quail (''Coturnix japonica'') resulted in rapid development of cataracts. All quail receiving single oral doses of 120 or 150 mg/kg developed cataracts within 4 hours of treatment. Mortality was also noted in these groups with losses being 1 of 5 at the lower dose and 5 of 9 at the higher dose<ref>Takahashi, K.W., Saito, T.R., Amao, H., Kosaka, T., Obata, M., Umeda, M. and Shirasu, Y., 1988. Acute reversible cataract due to nitrocompounds in Japanese quail (Coturnix coturnix japonica). Jikken dobutsu. Experimental animals, 37(3), pp.239-243.</ref>.
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==Introduction==
 
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[[File:Beal1w2 Fig1.png|thumb|200 px|left|Figure 1: Downrange distance of visible propellant plume on snow from the firing of different munitions. Note deposition behind firing line for the 84-mm rocket. Data from: Walsh et al.<ref>Walsh, M.R., Walsh, M.E., Ampleman, G., Thiboutot, S., Brochu, S. and Jenkins, T.F., 2012. Munitions propellants residue deposition rates on military training ranges. Propellants, Explosives, Pyrotechnics, 37(4), pp.393-406. [http://dx.doi.org/10.1002/prep.201100105 doi: 10.1002/prep.201100105]</ref><ref>Walsh, M.R., Walsh, M.E., Hewitt, A.D., Collins, C.M., Bigl, S.R., Gagnon, K., Ampleman, G., Thiboutot, S., Poulin, I. and Brochu, S., 2010. Characterization and Fate of Gun and Rocket Propellant Residues on Testing and Training Ranges: Interim Report 2. (ERDC/CRREL TR-10-13. Also: ESTCP Project ER-1481)  [[media:Walsh-2010 ERDC-CRREL TR-11-15 ESTCP ER-1481.pdf| Report]]</ref>]]
Acute and chronic aquatic toxicity bioassays conducted using standard fish (''Pimephales promelas'') and invertebrate (''Ceriodaphnia dubia'') indicated that acute toxicity was similar for the two species tested, with 48-hour lethal median concentrations (LC<sub>50</sub>) ranging from 37 to 42 mg/L DNAN. Chronic toxicity tests indicated that fish (7-day LC<sub>50</sub> = 10 mg/L) were more sensitive to DNAN compared to invertebrate (no significant impact on survival at 24 mg/L).
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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)]]
 
 
When assessing the most sensitive chronic endpoints, the two test species had similar chronic toxicity, with lowest observable adverse impacts ranging from 10 to 12 mg/L DNAN and median effects on sublethal endpoints (growth, reproduction) ranging from 11 to 15 mg/L DNAN. Chronic no-effect concentrations ranged from approximately 6 to 8 mg/L DNAN, which is less than that reported for TNT<ref>Kennedy, A.J., Lounds, C.D., Melby, N.L., Laird, J.G., Winstead, B., Brasfield, S.M. and Johnson, M.S., 2013. Development of environmental health criteria for insensitive munitions: Aquatic ecotoxicological exposures using 2, 4-dinitroanisole (No. ERDC/EL-TR-13-2). Engineer Research and Development Center, Vicksburg, MS Environmental Lab. [http://www.environmentalrestoration.wiki/images/7/7a/Kennedy-2013-Dev._of_Envl_Health_Criteria_for_Insensitive_Munitions.pdf Report pdf]</ref><ref>Kennedy, A.J., Laird, J.G., Lounds, C., Gong, P., Barker, N.D., Brasfield, S.M., Russell, A.L. and Johnson, M.S., 2015. Inter‐and intraspecies chemical sensitivity: A case study using 2, 4‐dinitroanisole. Environmental Toxicology and Chemistry, 34(2), pp.402-411. [http://dx.doi.org/10.1002/etc.2819 doi: 10.1002/etc.2819]</ref>. In a 96-hour freshwater green algae (''P. subcapitata'') inhibition test, DNAN had an EC<sub>20</sub> of 1.4 mg/L (concentration where 20% of maximum effect is observed). The results obtained for DNAN are similar to TNT (EC<sub>20</sub> of 0.54 mg/L<ref name= "DRDC2011">DRDC. 2011. Annual report 2010-2011. Environmental fate and ecological impact of emerging energetic chemicals (DNAN and its Amino-Derivatives, NTO, NQ, FOX-7, and FOX-12). Prepared by J. Hawari. NRC# 53363, Defense Research and Development Canada , National Research Council of Canada, Montréal, Québec</ref>).
 
 
 
Stanley et al. (2015)<ref>Stanley, J.K., Lotufo, G.R., Biedenbach, J.M., Chappell, P. and Gust, K.A., 2015. Toxicity of the conventional energetics TNT and RDX relative to new insensitive munitions constituents DNAN and NTO in Rana pipiens tadpoles. Environmental Toxicology and Chemistry, 34(4), pp.873-879. [http://dx.doi.org/10.1002/etc.2890 doi: 10.1002/etc.2890]</ref> reported acute and chronic (28-day) toxicity of DNAN exposure to northern leopard frogs (''Rana pipiens''; (sic)). The 96-hour LC<sub>50</sub> values from DNAN exposure were 24.3 mg/L (95% CI - 21.3-27.6 mg/L). The Lowest Observed Effect Concentration for mortality from 28-day exposures to DNAN was 2.4 mg/L. Changes in growth, swimming distance and other non-lethal parameters did not differ from controls.
 
  
===Summary===
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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>.
The nitroaromatic DNAN has toxicity properties very similar to other compounds of that class. Briefly, DNAN appears to be less toxic than TNT and many other nitroaromatics in mammalian and aquatic organisms.
 
  
==Nitrotriazelone (NTO) Toxicity==
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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>
<u>Mammalian</u> – NTO has very low acute oral toxicity. The oral median lethal dose (LD<sub>50</sub>) for NTO is >5000 mg/kg in both the rat and mouse<ref>London, J.E. and Smith, D.M., 1985. Toxicological study of NTO (No. LA-10533-MS). Los Alamos National Lab., NM (USA)</ref> systems.
 
  
Results from a 14-day subacute (between acute and chronic) oral toxicity study of NTO in rats were significantly decreased testes weights in the high-dose groups (≥500 mg/kg-day<ref name= "USAPHC2010">USAPHC. 2010. Toxicology Study No. 85-XC-0A6W-08, Protocol No. 0A6W-38-08-02-01, Subchronic oral toxicity of 3-nitro-1,2,4-triazol-5-one (NTO) in rats. Prepared by L.C.B. Crouse, J. T. Houpt, A. O'Neill, M.R. Way, T.L. Hanna, and M.J. Quinn. U.S. Army Public Health Command, Toxicology Portfolio, Aberdeen Proving Ground, MD 21010-5403</ref><ref name= "Crouse2015">Crouse, L.C., Lent, E.M. and Leach, G.J., 2015. Oral Toxicity of 3-Nitro-1, 2, 4-triazol-5-one in Rats. International journal of toxicology, 34 (1):55-66. [http://dx.doi.org/10.1177/1091581814567177 doi: 10.1177/1091581814567177 ]</ref>, but not the lower dose groups.
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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).
  
The most sensitive effect from a 90-day oral gavage study (feeding by means of a tube passed into the stomach) in rats of 0, 30, 100, 315, and 1000 mg NTO/kg-day found that testes and epididymides weights were reduced in the 315 and 1000 mg/kg-day exposures. NTO had no effect on mortality, food consumption, body weight, or neurobehavioral parameters. Moderate to severe testicular hypoplasia (underdevelopment), characterized by interstitial degeneration and loss of spermatogenic epithelium in the seminiferous tubules, was observed in the testes in 86% and 100% of males from the 315 and 1000 mg/kg-day dose groups, respectively. Epididymal aspermia was also observed at these dose levels<ref name= "USAPHC2010"/><ref name= "Crouse2015"/>. The testicular effects were the most sensitive adverse effect and were used to derive a BMDL10 (benchmark lower confidence limit yielding a 10% increase in risk) of 40 mg/kg-d. Exposures in mice show similar results<ref>Mullins, A.B., Despain, K.E., Wallace, S.M., Honnold, C.L. and May Lent, E., 2016. Testicular effects of 3-nitro-1, 2, 4-triazol-5-one (NTO) in mice when exposed orally. Toxicology Mechanisms and Methods, 26(2), pp.97-103. [doi:10.3109/15376516.2015.1118175 doi:10.3109/15376516.2015.1118175]</ref>. Reproductive studies have not found a relationship between NTO exposures and changes in offspring production; however, histological changes in testes and epididimydes remain consistent<ref>USAPHC. 2013. Repeated-Dose and Reproductive/Developmental Toxicity of NTO in the Rat. Prepared by L.C.B. Crouse, E.M. Lent, T.L. Hanna, and S.M. Wallace. U.S. Army Public Health Command, Toxicology Portfolio, Aberdeen Proving Ground, MD.</ref>. Results of investigating changes in endocrine disruption have largely been negative<ref>USAPHC. 2012. In Vitro Endocrine Disruption Screening of 3-nitro-1,2,4-triazol-5-one (NTO). Toxicology Report No. S.0002745-12. Prepared by V. H. Adams. U.S. Army Public Health Command, Toxicology Portfolio, Aberdeen Proving Ground, MD.</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"/>.
  
<u>Genotoxicity</u> - Test results examining damage to genetic information within a cell (genotoxicity) were negative in Salmonella at levels up to 500 µg/plate without activation and up to 5000 µg/plate with activation. In E. coli, results were also negative at maximum concentrations up to 2500 µg/plate without activation and 5000 µg/plate with activation<ref name= "Reddy2011">Reddy, G., Song, J., Kirby, P., Lent, E.M., Crouse, L.C. and Johnson, M.S., 2011. Genotoxicity assessment of an energetic propellant compound, 3-nitro-1, 2, 4-triazol-5-one (NTO). Mutation Research/Genetic Toxicology and Environmental Mutagenesis, 719(1), pp.35-40. [http://dx.doi.org/10.1016/j.mrgentox.2010.11.004  doi:10.1016/j.mrgentox.2010.11.004]</ref>.
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{| class="wikitable" style="float: right; text-align: center; margin-left: auto; margin-right: auto;"
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|+ Table 1. Soil Sample Concentrations and Precision from Military Ranges Using Discrete and Incremental Sampling. (Data from Taylor et al. <ref name= "Taylor2011"/> and references therein.)
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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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|}
  
NTO was also evaluated in the L5178Y TK+/˗ mouse lymphoma mutagenesis assay. Cells were treated with NTO at concentrations up to 5000 µg/mL, both with and without activation. Results of the assay were negative, either with or without activation<ref name= "Reddy2011"/>.
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==Incremental Sampling Approach==
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ISM is a requisite for representative and reproducible sampling of training ranges, but it is an involved process that is detailed thoroughly elsewhere<ref name= "Hewitt2009"/><ref name= "Taylor2011"/><ref name= "USEPA2006M"/>. In short, ISM involves the collection of many (30 to >100) increments in a systematic pattern within a decision unit (DU). The DU may cover an area where releases are thought to have occurred or may represent an area relevant to ecological receptors (e.g., sensitive species). Figure 3 shows the ISM sampling pattern in a simplified (5x5 square) DU. Increments are collected at a random starting point with systematic distances between increments. Replicate samples can be collected by starting at a different random starting point, often at a different corner of the DU. Practically, this grid pattern can often be followed with flagging or lathe marking DU boundaries and/or sampling lanes and with individual pacing keeping systematic distances between increments. As an example, an artillery firing point might include a 100x100 m DU with 81 increments.
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[[File:Beal1w2 Fig3.png|thumb|200 px|left|Figure 3. Example ISM sampling pattern on a square decision unit. Replicates are collected in a systematic pattern from a random starting point at a corner of the DU. Typically more than the 25 increments shown are collected]]
  
NTO was tested in CHO cells for clastogenicity. The test was conducted both with and without exogenous metabolic activation at concentrations up to 5000 µg/mL; results were negative<ref name= "Reddy2011"/>. NTO was negative in the SOS chromotest<ref name= "DRDC2011"/>.
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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.
  
<u>Ecotoxicity</u> - The 48-hour survival of ''Pimephales promelas'' was examined in containing NTO at concentrations ranging from 0 to 5.0 %. The LC<sub>50</sub> was 1.14 g/L calculated using the Trimmed-Spearman Karber method<ref>BAE Systems, 2007. Biomonitoring Retest of NTO Aquatic Toxicity in Pimephales promelas. West Stone Drive, Kingsport, TN 37660-9982.</ref><ref>BAE Systems Ordnance Systems, Inc. 2007. Material Safety Data Sheet (MSDS)-NTO. In 4509 West Stone Drive, Kingsport, TN 37660-9982.</ref>.
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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:No Author-Article 1-Table 1.PNG|thumbnail|right|Table 1.  Median lethal concentration of NTO to ''Ceriodaphnia'' (mg/L)]]
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==Sampling Tools==
''Ceriodaphnia dubia'' was used in a 7-day survival and reproduction study and the unicellular green algae ''Selenastrum capricornutum'' in a 96-hour growth inhibition study. In the definitive 7-day exposure study, the IC50-value was found to be 57 mg/L. The NOEC and LOEC values were found to be 34 mg/L and 66 mg/L, respectively. No eggs were produced at 262 mg/L, and at 133 mg/L eggs were produced but failed to develop<ref>Haley, M.V., Kuperman, R.G. and Checkai, R.T., 2009. Aquatic toxicity of 3-nitro-1, 2, 4-triazol-5-one (No. ECBC-TR-726). Edgewood Chemical Biological Center (ECBC), Aberdeen Proving Ground, MD. [http://www.environmentalrestoration.wiki/images/6/6c/Haley-2009-Aquatic_toxicity_of_3-Nitro-1%2C2%2C4-triazol-5-one..pdf Report pdf]</ref>, despite the lack of mortality at all concentrations up to 523 mg/L. System pH impacts the results, as indicated in Table 1.
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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.
  
===Summary===
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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>]]
Generally, NTO is much less toxic from oral exposures than other EMs. High oral concentrations in mammalian models have shown the most sensitive outcome to be low sperm production through direct toxic mode of action to germ cells in males. Aquatic toxicity is largely due to the acidic nature of NTO when added to water.
 
  
==Nitroguanidine (NQ) Toxicity==
+
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.
<u>Mammalian</u> - Nearly all studies conducted to-date suggest very low toxicity from exposures to NQ. The LD<sub>50</sub> is 3850 mg/kg in mice and 3120 mg/kg in guinea pig. Mortality is the result of respiratory cyanosis. The LD<sub>50</sub> in rats is >5000 mg/kg<ref>Brown, L.D., Wheeler, C.R. and Korte Jr, D.W., 1988. Acute Oral Toxicity of Nitroguanidine in Male and Female Rats (No. LAIR-264). Lettermann Army Inst. of Research Presidio of San Francisco, CA. [http://www.environmentalrestoration.wiki/images/0/0d/Brown-1988-Acute_Oral_Toxicity.pdf Report pdf]</ref><ref>Hiatt, G.F.S., Sano, S. K., Wheeler, C. R., and Korte, D.W., Jr., 1988. Acute oral toxicity of nitroguanidine in mice. (LAIR 265). Letterman Army Institute of Research, Presidio of San Francisco, CA. [http://www.environmentalrestoration.wiki/images/7/7c/Hiatt-1988-Acute_Oral_Toxicity_of_Nitroguanidine_in_Mice.pdf Report pdf]</ref><ref>Lewis, R.J. 2004.  Nitroguanidine in SAX’s dangerous properties of industrial materials. New York: John Wiley & Sons, Inc., Scientific, Technical and Medical Division. [http://dx.doi.org/10.1002/0471701343 doi: 10.1002/0471701343]</ref>.  
 
  
Subacute and subchronic (repeats over short period) oral toxicity of NQ in male and female rats exposed through the diet (0, 100, 316, or 1000 mg/kg-day for 90 days) indicated that food consumption was reduced and water consumption increased, with no other toxicity indicators<ref>Morgan, E.W., Brown, L.D., Lewis, C.M., Dahlgren, R.R. and Korte Jr, D.W., 1988. Fourteen-day subchronic oral toxicity study of nitroguanidine in rats (No. LAIR-272). Letterman Army Institute of Research, Presidio of San Francisco, CA. [http://www.environmentalrestoration.wiki/images/a/a2/Morgan-1988-Fourteen-day_subchronic_oral_toxicity_study....pdf Report pdf]</ref><ref>Morgan, E.W., Zaucha, G.M., Lewis, C.M., Makovec, G.T. and Pearce, M.J., 1988. Ninety-day subchronic oral toxicity study of nitroguanidine in rats (No. LAIR-306). Letterman Army Inst of Research Presidio of San Francisco CA[http://www.environmentalrestoration.wiki/images/d/d8/Morgan-1988-Ninety-day_Subchronic.pdf Report pdf]</ref>. Blood samples exhibited no abnormalities that could be attributed to NQ exposure. Microscopic examination of tissues from the control and 1000 mg/kg-day dose group animals suggested no lesions attributable to NQ exposure.
+
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>.
  
The 90-day subchronic oral toxicity of NQ using ICR (Institute of Cancer Research) mice exposed in to diet dose levels of 0, 100, 316 or 1000 mg/kg-day for 90 days indicated no effect on food consumption or weight gain; there was a dose-dependent increase in water consumption. Several serum chemistry parameters did exhibit differences compared to control values, but these changes were isolated occurrences with no consistent dose-related trends reported. Microscopic examination of tissues from the control and 1000 mg/kg-day dose group suggested no lesions attributable to the administration of NQ. The findings of increased water consumption suggest that NQ, which is excreted unchanged in mouse urine, may be acting as an osmotic diuretic. Higher brain-to-body weight ratios in male mice at 1000 mg/kg-day NQ supported a 316 mg/kg-day no adverse effect level (NOAEL)<ref>Frost, D.F., Morgan, E.W., Letellier, Y., Pearce, M.J. and Ferraris, S., 1988. Ninety-day subchronic oral toxicity study of nitroguanidine in mice (No. LAIR-319). Letterman Army Institute of Research, Presidio of San Francisco, CA. [http://www.environmentalrestoration.wiki/images/1/1e/Frost-1988-Ninety_day_subchronic_oral_Tox_study.pdf Report pdf]</ref>.  
+
==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.
  
<u>Genotoxicity</u> - NQ was not mutagenic in the Ames assay using ''Salmonella typhimurium'' strains, nor was it mutagenic for mouse lymphoma cells in the presence or absence of rat hepatic homogenates<ref>Ishidate, M. and Odashima, S., 1977. Chromosome tests with 134 compounds on Chinese hamster cells in vitro-a screening for chemical carcinogens. Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis, 48(3-4), pp.337-353. [http://dx.doi.org/10.1016/0027-5107(77)90177-4  doi: 10.1016/0027-5107(77)90177-4]</ref><ref name= "McGregor1980">McGregor, D.B., Riach, C.G., Hastwell, R.M. and Dacre, J.C., 1980. Genotoxic activity in microorganisms of tetryl, 1, 3‐dinitrobenzene and 1, 3, 5‐trinitrobenzene. Environmental mutagenesis, 2(4), pp.531-541. [http://dx.doi.org/10.1002/em.2860020411 doi: 10.1002/em.2860020411]</ref><ref>Sebastian, S.E. and D.W. Korte.  1988. Mutagenic potential of Gguanidine Nitratenitrate. Letterman Army Institute of Research, San Francisco, CA. Technical Report No. 260. Toxicology Series 107 (ADA155040). Letterman Army Institute of Research, Presidio of San Francisco, CA. </ref>. NQ-associated recombinant activity was not observed in ''Saccharomyces cerevisiae''<ref name= "McGregor1980"/>, and it was negative in dominant lethal assays with rats and mice<ref>Brusick, D. and Matheson, D.W., 1978. Mutagen and Oncogen Study on Nitroguanidine. Litton Bionetics Inc Kensington MD. [http://www.environmentalrestoration.wiki/images/5/58/Brusick-1978-Mutagen_and_Oncogen_Study_.pdf Report pdf]</ref>. NQ did not induce sister chromatid exchange in CHO cells at concentrations up to 3.9 mg/ml. DNA repair tests using E. coli (10 mg/plate) indicated no activity of NQ<ref>Harbell, J.W. and Korte Jr, D.W., 1987. Mutagenic potential of nitroguanidine in the mouse lymphoma forward mutation assay (No. LAIR-252). Letterman Army Institute of Research, Presidio of San Francisco, CA. [http://www.environmentalrestoration.wiki/images/2/29/Harbell-1987-Mutagenic_Potential_of_Nitroguanidine_Mouse_Lymphoma.pdf Report pdf]</ref><ref name= "McGregor1980"/>.
+
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.
  
<u>Ecotoxicity</u> - Fish exposed to NQ for 96 hours included fathead minnows (''Pimephales promelas''), bluegill (''Lepomis macrochirus''), Channel catfish (''Ictalurus punctatus''), and rainbow trout (''Salmo gairdneri''). Invertebrates were exposed for 48-hours and included ''Daphnia magna'', amphipods (''Hyallela azteca'' and ''Gammarus minus''), midge larvae (''Paratanytarsus dissimilis''), and aquatic worms (''Lumbriculus variegatus''). The acute toxicity of NQ was very low; fewer than 50% of the exposed organisms exposed died at concentrations up to the solubility limit of NQ in water (1700 mg/mL at 12<sup><u>o</u></sup>C for trout to about 3000 mg/L at 22<sup><u>o</u></sup>C for most other species). The alga (''Selenastrum capricornutum'') was slightly more sensitive, with 120-hour EC50’s of about 2000 mg/L. Complete photolysis of NQ with ultraviolet light greatly increased toxicity, with LC50/EC50 values decreasing to 20-35 mg/L (nominal concentration estimates).  
+
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).
  
Burrows et al. (1988)<ref>Burrows, W.D., Schmidt, M.O., Chyrek, R.H. and Noss, C.I., 1988. Photochemistry of aqueous nitroguanidine (No. USABRDL-TR-8808). Army Biomedical Research and Development Lab, Fort Detrick MD. [http://www.environmentalrestoration.wiki/images/e/e6/Burrows-1998-Photochemistry_of_aqueous_nitroguanidine.pdf Technical Report]</ref> investigated the photolytic toxicity further and reported NQ is readily degraded in water by ultraviolet and natural sunlight. The principal end products of photolysis from unbuffered NQ solutions are guanidine, urea, and nitrite ion, with lesser quantities of cyanoguanidine, nitrate ion and ammonia, accounting for 80% of the carbon and virtually all of the nitrogen. Nitrosoguanidine is an early intermediate, which is even more readily photolyzed, to guanidine. Photolysis of NQ at pH 10 proceeds at nearly the same rate as the unbuffered reaction, but the product mix is different; less than 25% of NQ carbon is accounted for as urea, guanidine and cyanoguanidine. N<sub>2</sub> is a significant product.  
+
<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>
All the identified photolysis products of NQ except urea are more toxic to aquatic organisms than the parent compound. However, only nitrite ion is present at a level high enough to account for the greatly enhanced toxicity of photolyzed NQ. It is highly unlikely that wastewaters discharged to a body of moving water could present a hazard to aquatic life unless the NQ levels substantially exceeded the present National Pollutant Discharge Elimination System (NPDES) daily average limit of 25 mg/L for Sunflower Army Ammunition Plan, given the photolytic half-life of NQ and the dilution that would take place.
+
<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>
In a 96-hour freshwater green algae (''P. subcapitata'') inhibition test, NQ had an EC20 of 760 mg/L<ref name= "DRDC2011"/>.
+
<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>
 
 
===Summary===
 
NQ generally is the least toxic of all three IM compounds. No acute toxicity or mutagenic effects have been observed. However, more research is needed to understand the potential for aquatic toxicity of environmental breakdown products that are likely short-lived.  
 
  
 +
==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==
 +
*[https://itrcweb.org/ Interstate Technology and Regulatory Council]
 +
*[http://www.hawaiidoh.org/tgm.aspx Hawaii Department of Health]
 +
*[http://envirostat.org/ Envirostat]

Latest revision as of 18:58, 29 April 2020

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

Related Article(s):


CONTRIBUTOR(S): Dr. Samuel Beal


Key Resource(s):

Introduction

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

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

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

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

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

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

Incremental Sampling Approach

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

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

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

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

Sampling Tools

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

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

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

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

Sample Processing

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

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

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

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

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

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

    References

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