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Passive sampling using integrative samplers enables the monitoring of munitions constituents in underwater environments over timescales of days to months and at ultra-low concentrations. Munitions compounds have an affinity for some resins and polymers that, when submerged for a period of time and corrected for the environment-specific sampling rate, can be used to determine time weighted average ambient water concentrations. This article primarily details the Polar Organic Chemical Integrative Sampler (POCIS), its optimization using laboratory flume and field experiments, and its application at munitions-impacted underwater sites.  
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The heterogeneous distribution of munitions constituents, released as particles from munitions firing and detonations on military training ranges, presents challenges for representative soil sample collection and for defensible decision making. Military range characterization studies and the development of the incremental sampling methodology (ISM) have enabled the development of recommended methods for soil sampling that produce representative and reproducible concentration data for munitions constituents. This article provides a broad overview of recommended soil sampling and processing practices for analysis of munitions constituents on military ranges.  
 
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'''CONTRIBUTOR(S):'''  [[Dr. Guilherme Lotufo]] and [[Gunther Rosen]]
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'''CONTRIBUTOR(S):'''  [[Dr. Samuel Beal]]
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'''Key Resource(s)''':  
 
'''Key Resource(s)''':  
*[[media: 2017-Rosen-Validation_of_Passive_Sampling_Devices_for_Monitoring_ER-201433.pdf| Validation of Passive Sampling Devices for Monitoring of Munitions Constituents in Underwater Environments]]<ref name= "Rosen2017">Rosen, G., Colvin, M., George, R., Lotufu, G., Woodley, C., Smith, D. and Belden, J., 2017. Validation of passive sampling devices for monitoring of munitions constituents in underwater environments (No. SPAWAR-SCP-TR-3076). SPAWAR Systems Center Pacific San Diego. [[media:2017-Rosen-Validation_of_Passive_Sampling_Devices_for_Monitoring_ER-201433.pdf| Report.pdf]]</ref>.
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*[[media:Taylor-2011 ERDC-CRREL TR-11-15.pdf| Guidance for Soil Sampling of Energetics and Metals]]<ref name= "Taylor2011">Taylor, S., Jenkins, T.F., Bigl, S., Hewitt, A.D., Walsh, M.E. and Walsh, M.R., 2011. Guidance for Soil Sampling for Energetics and Metals (No. ERDC/CRREL-TR-11-15). [[media:Taylor-2011 ERDC-CRREL TR-11-15.pdf| Report.pdf]]</ref>
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*[[Media:Hewitt-2009 ERDC-CRREL TR-09-6.pdf| Report.pdf | Validation of Sampling Protocol and the Promulgation of Method Modifications for the Characterization of Energetic Residues on Military Testing and Training Ranges]]<ref name= "Hewitt2009">Hewitt, A.D., Jenkins, T.F., Walsh, M.E., Bigl, S.R. and Brochu, S., 2009. Validation of sampling protocol and the promulgation of method modifications for the characterization of energetic residues on military testing and training ranges (No. ERDC/CRREL-TR-09-6). Engineer Research and Development Center / Cold Regions Research and Engineering Lab (ERDC/CRREL) TR-09-6, Hanover, NH, USA. [[Media:Hewitt-2009 ERDC-CRREL TR-09-6.pdf | Report.pdf]]</ref>
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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>
  
==Background==
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==Introduction==
[[File:Lotufo1w2Fig1.png|thumb|left| Figure 1. Underwater munitions are derived from UXO and historical disposal practices]]
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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>]]
Underwater [[Wikipedia: Unexploded ordnance | unexploded ordnance (UXO)]] at active and former training ranges and discarded military munitions (DMM), collectively referred to as underwater munitions and explosives of concern (MEC), present challenges due to both immediate safety considerations (e.g. explosive blast) and potential ecological and human health impacts resulting from the release of munition constituents (MC) to the marine environment. Underwater sites around the world are known to contain MEC as a result of military activities or historic disposal events (Figure 1). MC including [[Wikipedia: TNT | 2,4,6-trinitrotoluene (TNT)]] and [[Wikipedia: RDX | 1,3,5-trinitro-1,3,5-triazine (RDX)]] may be released into the surrounding aquatic environments as a result of MEC corrosion and breaching of the munition’s outer casing<ref>Lewis, J., Martel, R., Trépanier, L., Ampleman, G. and Thiboutot, S., 2009. Quantifying the transport of energetic materials in unsaturated sediments from cracked unexploded ordnance. Journal of environmental quality, 38(6), pp.2229-2236. doi: 10.2134/jeq2009.0019 [https://www.researchgate.net/profile/Richard_Martel3/publication/38054241_Quantifying_the_Transport_of_Energetic_Materials_in_Unsaturated_Sediments_from_Cracked_Unexploded_Ordnance/links/0c96051b9cfaedc02a000000.pdf Free pdf download]</ref><ref>Rosen, G. and Lotufo, G.R., 2010. Fate and effects of Composition B in multispecies marine exposures. Environmental toxicology and chemistry, 29(6), pp.1330-1337.[[Media:2010-Rosen-Fate_and_effects_of_Composition_B.pdf|Report.pdf]]</ref><ref name= "Wang2011">Wang, P.F., Liao, Q., George, R. and Wild, W., 2011. Release rate and transport of munitions constituents from breached shells in marine environment. In Environmental chemistry of explosives and propellant compounds in soils and marine systems: Distributed source characterization and remedial technologies (pp. 317-340). American Chemical Society. [https://doi.org/10.1021/bk-2011-1069.ch016 doi: 10.1021/bk-2011-1069.ch016]</ref><ref>Li, Y., Yang, C., Bao, Y., Ma, X., Lu, G. and Li, Y., 2016. Aquatic passive sampling of perfluorinated chemicals with polar organic chemical integrative sampler and environmental factors affecting sampling rate. Environmental Science and Pollution Research, 23(16), pp.16096-16103. [https://doi.org/10.1007/s11356-016-6791-1 doi: 10.1007/s11356-016-6791-1]</ref><ref name= "Voie2017">Voie, Øyvind A., and Espen Mariussen. "Risk assessment of sea dumped conventional munitions." Propellants, Explosives, Pyrotechnics 42, no. 1 (2017): 98-105. [https://doi.org/10.1002/prep.20160 doi:10.1002/prep.20160]</ref><ref name= "Rosen2018">Rosen, G., Lotufo, G.R., George, R.D., Wild, B., Rabalais, L.K., Morrison, S. and Belden, J.B., 2018. Field validation of POCIS for monitoring at underwater munitions sites. Environmental toxicology and chemistry, 37(8), pp.2257-2267. [https://doi.org/10.1002/etc.4159 doi: 10.1002/etc.4159]</ref><ref name= "Beck2018">Beck, A.J., Gledhill, M., Schlosser, C., Stamer, B., Böttcher, C., Sternheim, J., Greinert, J. and Achterberg, E.P., 2018. Spread, behavior, and ecosystem consequences of conventional munitions compounds in coastal marine waters. Frontiers in Marine Science, 5, p.141. [[media:2018-Beck-Spread%2C_Behavior_and_Ecosystem_Consequences.pdf| Report.pdf]]</ref><ref name= "Beck2019">Beck, A.J., van der Lee, E.M., Eggert, A., Stamer, B., Gledhill, M., Schlosser, C. and Achterberg, E.P., 2019. In situ measurements of explosive compound dissolution fluxes from exposed munition material in the Baltic Sea. Environmental science & technology, 53(10), pp.5652-5660. [https://doi.org/10.1021/acs.est.8b06974  doi: 10.1021/acs.est.8b06974]</ref>. Release may also occur from fragments of explosives formulations that become exposed following low-order (incomplete) detonations (LOD) resulting in fully breached munitions<ref name= "Beck2019"/> (Figure 2).
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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)]]
  
[[File:Lotufo1w2Fig2.png|thumb|left|Figure 2. Conceptual diagram of MC release from a breached underwater UXO.]]
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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 rate of release of MC from MEC into the surrounding environment is expected to be influenced by the size of the initial breach and growth of the breach hole in the munition casing, the radius of the cavity formed due to loss of MC mass from inside the MEC, the dissolution rate from solid to aqueous phases of the MC inside the MEC, the outside ambient current to which the casing breach hole is exposed, and the mass of MC remaining inside<ref name= "Wang2011"/><ref>Wang, P. F., George, R. D., Wild, W. J., and Liao, Q., 2013. Defining munition constituent (MC) source terms in aquatic environments on DoD Ranges (ER-1453), Final Report. SSC Pacific Technical Report 1999. Strategic Environmental Research and Development Program (SERDP). Space and Naval Warfare Systems Center (SSC) Pacific: San Diego, CA [[media:2013-Wang_Defining_Munition_Constituent_ER-1453.pdf| Report.pdf]]</ref>. Subsequent to the breaching event, concentrations in the surrounding environment are expected to fluctuate over time because of the dependence of release kinetics on the above parameters, as well as hydrodynamic conditions leading to dilution effects, sorption to suspended particles, photo-transformation, and other factors leading to MC loss from the aquatic environment<ref name= "Voie2017"/><ref name= "Lotufo2017">Lotufo, G.R., Chappell, M.A., Price, C.L., Ballentine, M.L., Fuentes, A.A., Bridges, T.S., George, R.D., Glisch, E.J., Carton, G. 2017. Review and synthesis of evidence regarding environmental risks posed by munitions constituents (MC) in aquatic systems, Final report. SERDP Project ER-2341. ERDC/EL TR-17-17. US Army Corps of Engineers, Engineer Research and Development Center, Vicksburg, MS [[Media:2017-Lotufo-Review_and_Synthesis_of_Evidence_Re_Envl_Risks.pdf | Report.pdf]]</ref><ref name= "Tobias2019">Tobias, C. 2019. Tracking the uptake, translocation, cycling, and metabolism of munitions compounds in coastal marine ecosystems using Stable Isotopic Tracer, Final Report.  SERDP Project ER-2122. [[media:2019-Tobias-Tracking_the_Uptake%2C_Translocation%2C_Cycling_and_Metabolism-ER-2122.pdf| Report.pdf]]</ref>. As a result of slow release and rapid removal of MC in the surrounding water<ref name= "Beck2018"/><ref name= "Lotufo2017"/><ref name= "Tobias2019"/>, MC have been detected at low frequency relative to the number of samples examined and at low concentrations at Underwater Military Munitions (UWMM) sites<ref name= "Voie2017"/><ref name= "Beck2018"/><ref name= "Lotufo2017"/>. Overall, munitions constituent persistence in the environment is a key determinant of exposure<ref name= "Lotufo2017"/>. Exposure to MC in water has been shown to be toxic to aquatic organisms belonging to various taxonomic groups<ref name= "Beck2018"/><ref name= "Lotufo2017"/><ref>Craig, H.D. and Taylor, S., 2011. Framework for evaluating the fate, transport, and risks from conventional munitions compounds in underwater environments. Marine Technology Society Journal, 45(6), pp.35-46. [https://doi.org/10.4031/MTSJ.45.6.10  doi: 10.4031/MTSJ.45.6.10 ]</ref><ref>Lotufo, G.R., Rosen, G., Wild, W. and Carton, G., 2013. Summary review of the aquatic toxicology of munitions constituents (No. ERDC/EL-TR-13-8). US Army Corps of Engineers, Engineer Research and Development Center, Vicksburg, MS [[Media:2013-Lotufo-Summary_Review_of_the_Aqatic_Toxicology.pdf | Report.pdf]]</ref>.
 
  
==Underwater Sampling Challenges==
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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>
Considering that MC are expected to be present at UWMM sites mainly at ultra-low concentrations and with concentrations decreasing with increasing distance from the source of released MC<ref name= "Rosen2018"/><ref>Rodacy, P.J., Reber, S.D., Walker, P.K. and Andre, J.V., 2001. Chemical sensing of explosive targets in the Bedford Basin, Halifax Nova Scotia. Sandia National Laboratories. [[media:2001-Rodacy-Chemical_Sensing_of_Explosive_Targets_in_the_Bedford_basin.pdf| Report.pdf]]</ref><ref>Porter, J.W., Barton, J.V. and Torres, C., 2011. Ecological, radiological, and toxicological effects of naval bombardment on the coral reefs of Isla de Vieques, Puerto Rico. In Warfare Ecology (pp. 65-122). Springer, Dordrecht. [https://doi.org/10.1007/978-94-007-1214-0_8 doi:10.1007/978-94-007-1214-0_8]</ref><ref name= "Rosen2017"/>, a number of challenges prevent accurate assessment of environmental exposure using traditional water, sediment, and tissue sampling and analyses. These challenges include a high level of effort or difficulty required to:</br>  
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1. identify breached underwater MEC that are actually releasing MC;</br>  
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2. measure MC in the water column at low levels; and</br>
 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3. characterize water column exposure using the appropriate spatial and temporal scales for determining ecological risk.</br>
 
  
Standard environmental sampling, such as grab sampling of surface water, only generates information for the time of sample collection, and spot grab sampling strategies may inadequately capture temporal changes<ref>Poulier, G., Lissalde, S., Charriau, A., Buzier, R., Cleries, K., Delmas, F., Mazzella, N. and Guibaud, G., 2015. Estimates of pesticide concentrations and fluxes in two rivers of an extensive French multi-agricultural watershed: application of the passive sampling strategy. Environmental Science and Pollution Research, 22(11), pp.8044-8057.</ref> in MC concentrations that occur at UWMM sites, thereby providing an inaccurate measure of environmental exposure. In contrast, integrative passive sampling has been used to derive ultra-low and time-weighted water concentrations for a wide range of environmental contaminants<ref>Roll, I.B. and Halden, R.U., 2016. Critical review of factors governing data quality of integrative samplers employed in environmental water monitoring. Water research, 94, pp.200-207. [[Media:2016-Roll-Critical_Review_of_Factors_Governing_Data_Quality.pdf| Open Access Manuscript]]</ref>, including MC<ref name= "Rosen2018"/><ref name= "belden2015">Belden, J.B., Lotufo, G.R., Biedenbach, J.M., Sieve, K.K. and Rosen, G., 2015. Application of POCIS for exposure assessment of munitions constituents during constant and fluctuating exposure. Environmental toxicology and chemistry, 34(5), pp.959-967. [https://doi.org/10.1002/etc.2836 doi: 10.1002/etc.2836]</ref><ref name = "Rosen2016">Rosen, G., Wild, B., George, R.D., Belden, J.B. and Lotufo, G.R., 2016. Optimization and field demonstration of a passive sampling technology for monitoring conventional munition constituents in aquatic environments. Marine Technology Society Journal, 50(6), pp.23-32. [https://doi.org/10.4031/MTSJ.50.6.4  doi: 10.4031/MTSJ.50.6.4 ]</ref><ref name= "Lotufo2018">Lotufo, G.R., George, R.D., Belden, J.B., Woodley, C.M., Smith, D.L. and Rosen, G., 2018. Investigation of polar organic chemical integrative sampler (POCIS) flow rate dependence for munition constituents in underwater environments. Environmental monitoring and assessment, 190(3), p.171. [https://doi.org/10.1007/s10661-018-6558-x  doi: 10.1007/s10661-018-6558-x ]</ref><ref name= "Lotufo2019">Lotufo, G.R., George, R.D., Belden, J.B., Woodley, C., Smith, D.L. and Rosen, G., 2019. Release of Munitions Constituents in Aquatic Environments Under Realistic Scenarios and Validation of Polar Organic Chemical Integrative Samplers for Monitoring. Environmental toxicology and chemistry, 38(11), pp.2383-2391. [https://doi.org/10.1002/etc.4553  doi: 10.1002/etc.4553 ]</ref><ref name= "Estoppey2019">Estoppey, N., Mathieu, J., Diez, E.G., Sapin, E., Delémont, O., Esseiva, P., de Alencastro, L.F., Coudret, S. and Folly, P., 2019. Monitoring of explosive residues in lake-bottom water using Polar Organic Chemical Integrative Sampler (POCIS) and chemcatcher: determination of transfer kinetics through Polyethersulfone (PES) membrane is crucial. Environmental pollution, 252, pp.767-776. [https://doi.org/10.1016/j.envpol.2019.04.087 doi: 10.1016/j.envpol.2019.04.087]</ref>. Polar organic chemical integrative samplers (POCIS)<ref name= "Alvarez2004">Alvarez, D.A., Petty, J.D., Huckins, J.N., Jones‐Lepp, T.L., Getting, D.T., Goddard, J.P. and Manahan, S.E., 2004. Development of a passive, in situ, integrative sampler for hydrophilic organic contaminants in aquatic environments. Environmental Toxicology and Chemistry: An International Journal, 23(7), pp.1640-1648. [https://doi.org/10.1897/03-603 doi:10.1897/03-603]</ref> currently are the most widely used samplers for weakly hydrophobic contaminants (typically those with [[Wikipedia: Partition coefficient | log ''K<sub>ow</sub>'']] < 4).  
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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 US Department of Defense’s [https://www.serdp-estcp.org/About-SERDP-and-ESTCP Environmental Security Technology Certification Program (ESTCP)] provided funding for research aimed at optimizing use of POCIS passive sampling technology for sampling MC in water and at demonstrating the application of POCIS to determine time-weighted average (TWA) water-column concentrations in the vicinity of MEC at a UWMM site [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Sediments/Munitions-Constituents/ER-201433 (ESTCP Project ER‐201433)]<ref name= "Rosen2017"/>. Some results of that project are presented in the following sections of this article.
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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"/>.
  
==Technology Overview==
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{| class="wikitable" style="float: right; text-align: center; margin-left: auto; margin-right: auto;"
The POCIS consists of a receiving phase [[Wikipedia: Sorbent | (sorbent)]] sandwiched between two [[Wikipedia: Polysulfone | polyethersulfone (PES)]] microporous membranes with ~0.1 μm pore size<ref name= "Alvarez2004"/> (Figure 3). The sampler is held together by two stainless steel rings with an interior diameter of 51-54 mm, which provides an exposure surface area of 41-46 cm<sup>2</sup>. The POCIS are available commercially from Environmental Sampling Technologies (EST; St. Joseph, Missouri), and contain the widely used Oasis® hydrophilic-lipophilic balance (HLB) polymer as the sorbent. A variety of sampler holders and canisters have been used to protect the passive samplers in the field. The holder and canister shown in Figure 4 are commercially available from EST.
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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.)
[[File:Lotufo1w2Fig3.png|thumb|left|Figure 3. the structure of a POCIS where stainless steel encompasses the PES membranes and the adsorbent in the middle (from Morin et al. 2012 and Seethapathy et al. 2008)<ref name = "Morin2012">Morin, N., Miège, C., Coquery, M. and Randon, J., 2012. Chemical calibration, performance, validation and applications of the polar organic chemical integrative sampler (POCIS) in aquatic environments. TrAC Trends in Analytical Chemistry, 36, pp.144-175. doi: 10.1016/j.trac.2012.01.007 [[media:2012-Morin-Chemical_Calibration_Performance%2C_Validation%2C_and_applications...POCIS.pdf| Author's Manuscript]]</ref><ref>Seethapathy, S., Gorecki, T. and Li, X., 2008. Passive sampling in environmental analysis. Journal of Chromatography A, 1184(1-2), pp.234-253. [https://doi.org/10.1016/j.chroma.2007.07.070 doi: 10.1016/j.chroma.2007.07.070]</ref>.]]
+
|-
[[File:Lotufo1w2Fig4.png|thumb|left|Figure 4.  Sample holder (left) and protective canister for multiple POCIS (right, both supplied by EST)]]
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! Military Range Type !! Analyte !! Range<br/>(mg/kg) !! Median<br/>(mg/kg) !! RSD<br/>(%)
 
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|-
For passive sampling of contaminants, the POCIS are kept immersed in water typically for two weeks to one month. However, depending on the study objectives, deployment times can range from days to months. At the end of the deployment time the POCIS are collected and transported to a laboratory where they are dismantled for collection of the full mass of sorbent. Analytes are extracted from sorbent using standard techniques, typically by organic solvent extraction in a [[Wikipedia: Column chromatography | chromatography column]]. The eluate can be analyzed using instrumental techniques such as [[Wikipedia: Liquid chromatography–mass spectrometry | liquid chromatography coupled with mass spectrometry (LC/MS)]] or by [[Wikipedia: Gas chromatography–mass spectrometry | gas chromatography coupled with MS (GC/MS)]]. More than 300 chemicals with a wide range of commercial and industrial applications have been detected or quantified by the POCIS in laboratory and field testing<ref name = "Morin2012"/>.
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| colspan="5" style="text-align: left;" | '''Discrete Samples'''
 
+
|-
Accumulation in the POCIS is based on passive diffusion of analytes from water into the POCIS receiving phase.  The POCIS is designed to operate as an infinite sink for analytes during the linear uptake stage. As such, it is used to determine TWA concentrations but does not capture any fluctuations in concentrations that occur during the deployment period. In order to obtain TWA concentrations of the molecules being studied, laboratory or ''in situ'' calibration of the POCIS is necessary. The calibration allows the determination of chemical-specific sampling rates (R<sub>s</sub>) using experimentally derived uptake rates. The R<sub>s</sub> is defined as the volume of water cleared in a unit of time (typically L/d). The sampling rates are necessary to convert the mass of a compound accumulated in the sorbent phase of the sampler to its concentration in the environmental medium sampled. Sampling rates are typically empirically derived during laboratory studies employing a closed system in which the contaminants of concern are spiked only at the beginning of the experiment or at constant time intervals<ref name= "belden2015"/><ref>Mazzella, N., Dubernet, J.F. and Delmas, F., 2007. Determination of kinetic and equilibrium regimes in the operation of polar organic chemical integrative samplers: Application to the passive sampling of the polar herbicides in aquatic environments. Journal of Chromatography A, 1154(1-2), pp.42-51. [https://doi.org/10.1016/j.chroma.2007.03.087  doi: 10.1016/j.chroma.2007.03.087 ]</ref><ref>Arditsoglou, A. and Voutsa, D., 2008. Passive sampling of selected endocrine disrupting compounds using polar organic chemical integrative samplers. Environmental Pollution, 156(2), pp.316-324. [https://doi.org/10.1016/j.envpol.2008.02.007  doi: 10.1016/j.envpol.2008.02.007 ]</ref>. The POCIS-derived TWA is calculated using Equation 1:
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| Artillery FP || 2,4-DNT || <0.04 – 6.4 || 0.65 || 110
 
+
|-
{|
+
| Antitank Rocket || HMX || 5.8 – 1,200 || 200 || 99
| || Equation 1:&nbsp;&nbsp;&nbsp;&nbsp; || '''''<big>C</big><sub>w</sub><big> =&nbsp;&nbsp;<sup>N</sup> / <sub>(R</big><sub>s</sub></sub><big><sub>* t) </sub></big>'''''
+
|-
 +
| 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
 
|-
 
|-
| Where:&nbsp;&nbsp;&nbsp;&nbsp;
+
| colspan="5" style="text-align: left;" | '''Incremental Samples*'''
 
|-
 
|-
| || ''C<sub>w</sub>'' || is the TWA water concentration (ng/L),
+
| Artillery FP || 2,4-DNT || 0.60 – 1.4 || 0.92 || 26
 
|-
 
|-
| || ''N'' || is the mass of the chemical accumulated by the sampler (ng),
+
| Bombing || TNT || 13 – 17 || 14 || 17
 
|-
 
|-
| || ''R<sub>s</sub>'' || is the sampling rate (L/day), and
+
| Artillery/Bombing || RDX || 3.9 – 9.4 || 4.8 || 38
 +
|-
 +
| Thermal Treatment || HMX || 3.96 – 4.26 || 4.16 || 4
 
|-
 
|-
| || ''t'' || is the exposure time (days).
+
| colspan="5" style="text-align: left; background-color: white;" | * For incremental samples, 30-100 increments and 3-10 replicate samples were collected.
 
|}
 
|}
  
A multitude of factors affect the sampling rate. The pattern and rate of water flow (i.e., current’s velocity and direction) across the PES membranes that house the POCIS sorbent generally have the largest impact on R<sub>s</sub>. This is because diffusion of dissolved substances across the membrane is dependent on the thickness of the water boundary layer at the membrane surface, which is affected by water flow induced turbulence around the sampler<ref name= "Harman2012">Harman, C., Allan, I.J. and Vermeirssen, E.L., 2012. Calibration and use of the polar organic chemical integrative sampler-a critical review. Environmental Toxicology and Chemistry, 31(12), pp.2724-2738. doi: 10.1002/etc.2011 [[media:2012-Harman-Calibration_and_use_of_the_Polar_Organic_Chemical.pdf| Report.pdf]]</ref><ref>Godlewska, K., Stepnowski, P. and Paszkiewicz, M., 2020. Application of the Polar Organic Chemical Integrative Sampler for Isolation of Environmental Micropollutants–A Review. Critical reviews in Analytical Chemistry, 50(1), pp.1-28. [https://doi.org/10.1080/10408347.2019.1565983 doi: 10.1080/10408347.2019.1565983]</ref>. Other variables such as biofouling have also been found to have some impact on R<sub>s</sub><ref name = Li2018">Li, Y., Yang, C., Zha, D., Wang, L., Lu, G., Sun, Q. and Wu, D., 2018. In situ calibration of polar organic chemical integrative samplers to monitor organophosphate flame retardants in river water using polyethersulfone membranes with performance reference compounds. Science of The Total Environment, 610, pp.1356-1363. [https://doi.org/10.1016/j.scitotenv.2017.08.234 doi: 10.1016/j.scitotenv.2017.08.234  ]</ref>. The accuracy of calibrated sampling rates for subsequent environmental studies is dependent on how similar the site exposure conditions are to those used in the calibration experiment<ref name= "Harman2012"/>. Therefore, samplers should be calibrated in conditions as close as possible to those expected at the monitored sites<ref name= "Estoppey2019"/>.
+
==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<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.
 +
[[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]]
 +
 
 +
DUs can vary in shape (Figure 4), size, number of increments, and number of replicates according to a project’s data quality objectives.
 +
 
 +
[[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)]]
 +
 
 +
==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.
 +
 
 +
[[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>]]
 +
 
 +
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.
  
Because of the wide range of field environmental conditions, the biggest challenge facing the use of POCIS has been the lack of a correction method to quantify the effect on the uptake process when field conditions vary from those of the calibration experiment. To overcome this issue, performance reference compounds (PRCs) with experimentally quantified dissipation rates can be spiked into the samplers prior to deployment to account for the effects of field exposure conditions on R<sub>S</sub> values. PRCs should be chosen that do not occur in the environment in which the sampler will be used. The selected PRC should also be significantly but not completely depleted over the planned  deployment period. The mass of PRC lost during deployment is then used to improve the accuracy of the estimated TWA concentration of the analyte of interest. Performance reference compounds have been successfully and widely used to correct for the impact of exposure conditions on hydrophobic passive samplers<ref>Booij, K. and Smedes, F., 2010. An improved method for estimating in situ sampling rates of nonpolar passive samplers. Environmental Science & Technology, 44(17), pp.6789-6794. [https://doi.org/10.1021/es101321v  doi: 10.1021/es101321v ] </ref>. A study by Li et al.<ref name =  "Li2018"/> was the first to demonstrate the reliable use of PRCs for determining TWA concentrations in the field using POCIS.
+
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>.
  
POCIS typically exhibit negligible analyte loss rates even when local environmental concentrations of the analyte drop to undetectable levels for some portion of the deployment period. This allows small masses of a chemical of interest from episodic release events to be retained in the device at the end of the deployment period<ref name= "belden2015"/><ref>Harman, C., Thomas, K.V., Tollefsen, K.E., Meier, S., Bøyum, O. and Grung, M., 2009. Monitoring the freely dissolved concentrations of polycyclic aromatic hydrocarbons (PAH) and alkylphenols (AP) around a Norwegian oil platform by holistic passive sampling. Marine Pollution Bulletin, 58(11), pp.1671-1679. [https://doi.org/10.1016/j.marpolbul.2009.06.022  doi: 10.1016/j.marpolbul.2009.06.022 ]</ref><ref>Morrison, S.A. and Belden, J.B., 2016. Calibration of nylon organic chemical integrative samplers and sentinel samplers for quantitative measurement of pulsed aquatic exposures. Journal of Chromatography A, 1449, pp.109-117. [https://doi.org/10.1016/j.chroma.2016.04.072  doi: 10.1016/j.chroma.2016.04.072]</ref><ref>Bernard, M., Boutry, S., Tapie, N., Budzinski, H. and Mazzella, N., 2018. Lab-scale investigation of the ability of Polar Organic Chemical Integrative Sampler to catch short pesticide contamination peaks. Environmental Science and Pollution Research, pp.1-11. [https://doi.org/10.1007/s11356-018-3391-2  doi: 10.1007/s11356-018-3391-2 ]</ref>. Therefore, the POCIS offer an advantageous alternative to traditional sampling methods (e.g. collection of discrete grab samples) at sites where fluctuation in concentrations or low-level concentrations are expected to occur, such as in the vicinity of underwater munitions. The continuous sampling approach of POCIS allows quantification of concentrations in an integrative manner as time weighted averages that are representative of the entire sampling period. The cumulative sampling of contaminant mass over the sampling period also enriches the analyte in the sorbent, which improves detection and quantification of the analyte. As another advantage, the POCIS provides protection of sorbed analytes against decomposition during post-deployment transport and storage<ref>Miège, C., Mazzella, N., Allan, I., Dulio, V., Smedes, F., Tixier, C., Vermeirssen, E., Brant, J., O’Toole, S., Budzinski, H. and Ghestem, J.P., 2015. Position paper on passive sampling techniques for the monitoring of contaminants in the aquatic environment–achievements to date and perspectives. Trends in Environmental Analytical Chemistry, 8, pp.20-26. [[media:2015-Miege-Position_Paper_on_Passive_Sampling_Techniques.pdf| Author's Manuscript]]</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.
  
 +
Incremental soil samples are typically air dried over the course of a few days. Oven drying thermally degrades some energetic compounds and should be avoided<ref>Cragin, J.H., Leggett, D.C., Foley, B.T., and Schumacher, P.W., 1985. TNT, RDX and HMX explosives in soils and sediments: Analysis techniques and drying losses. (CRREL Report 85-15) Hanover, NH, USA. [[media:Cragin-1985 CRREL 85-15.pdf| Report.pdf]]</ref>. Once dry, the samples are sieved with a 2-mm screen, with only the less than 2-mm fraction processed further. This size fraction represents the USDA definition of soil. Aggregate soil particles should be broken up and vegetation shredded to pass through the sieve. Samples from impact or demolition areas may contain explosive particles from low order detonations that are greater than 2 mm and should be identified, given appropriate caution, and potentially weighed.
  
 +
The <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).
  
 +
<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==
Line 63: Line 127:
  
 
==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