Difference between revisions of "User:Debra Tabron/sandbox"

From Enviro Wiki
Jump to: navigation, search
(Applications to Environmental Remediation and Restoration – Forensics)
 
(302 intermediate revisions by the same user not shown)
Line 1: Line 1:
Compound Specific Isotope Analysis (CSIA) refers to measurement of the isotopic signatures (typically, the stable isotopes of carbon, hydrogen, oxygen, nitrogen or sulfur) of individual compounds from a complex environmental mixture. The approach provides information about source differentiation, a quantitative means to delineate reaction pathways, including biodegradation, and an additional line of evidence for remediation monitoring of sites contaminated with hydrocarbons.  
+
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 Article(s)''':
  
'''CONTRIBUTOR(S):''' [[Dr. Barbara Sherwood Lollar, F.R.S.C.]]
+
 
 +
'''CONTRIBUTOR(S):''' [[Dr. Samuel Beal]]
  
  
 
'''Key Resource(s)''':  
 
'''Key Resource(s)''':  
*[http://www.environmentalrestoration.wiki/images/a/a9/Hunkeler-2008-A_Guide.pdf A Consensus Guide For Assessing Biodegradation and Source Identification Of Organic Contaminants In Groundwater Using Compound Specific Stable Isotope Analysis (CSIA)]<ref name = "Hunkeler2008">Hunkeler, D., Meckenstock, R. U., Sherwood Lollar, B., Schmidt, T. C. and Wilson, J. T., 2008. A Guide for Assessing Biodegradation and Source Identification of Organic Groundwater Contaminants Using Compound Specific Isotope Analysis (CSIA). U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-08/148, 2008. [http://www.environmentalrestoration.wiki/images/a/a9/Hunkeler-2008-A_Guide.pdf Report pdf]</ref>
+
*[[media:Taylor-2011 ERDC-CRREL TR-11-15.pdf| Guidance for Soil Sampling of Energetics and Metals]]<ref name= "Taylor2011">Taylor, S., Jenkins, T.F., Bigl, S., Hewitt, A.D., Walsh, M.E. and Walsh, M.R., 2011. Guidance for Soil Sampling for Energetics and Metals (No. ERDC/CRREL-TR-11-15). [[media:Taylor-2011 ERDC-CRREL TR-11-15.pdf| Report.pdf]]</ref>
 +
*[[Media: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>
 +
*[[media:Epa-2006-method-8330b.pdf| U.S. EPA SW-846 Method 8330B: Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC)]]<ref name= "USEPA2006M">U.S. Environmental Protection Agency (USEPA), 2006. Method 8330B (SW-846): Nitroaromatics, Nitramines, and Nitrate Esters by High Performance Liquid Chromatography (HPLC), Rev. 2. Washington, D.C. [[media:Epa-2006-method-8330b.pdf | Report.pdf]]</ref>
 +
*[[media:Epa-2007-method-8095.pdf | U.S. EPA SW-846 Method 8095: Explosives by Gas Chromatography.]]<ref name= "USEPA2007M">U.S. Environmental Protection Agency (US EPA), 2007. Method 8095 (SW-846): Explosives by Gas Chromatography. Washington, D.C. [[media:Epa-2007-method-8095.pdf| Report.pdf]]</ref>
  
 
==Introduction==
 
==Introduction==
Compound Specific Isotope Analysis (CSIA) refers to measurement of the '''isotopic signatures''' (typically, carbon, hydrogen, oxygen, nitrogen or sulfur in an environmental context) of individual compounds from a complex environmental mixture of components. The approach was developed most extensively during the post-WWII era for application to source rock identification and '''hydrocarbon exploration''', and remains a foundation of the oil and gas industry. In the 1980s, '''John M. Hayes''' at Indiana University Bloomington and collaborators<ref>Merritt, D.A., Brand, W.A. and Hayes, J.M., 1994. Isotope-ratio-monitoring gas chromatography-mass spectrometry: methods for isotopic calibration. Organic Geochemistry, 21(6-7), pp.573-583. [https://doi.org/10.1016/0146-6380(94)90003-5 doi: 10.1016/0146-6380(94)90003-5]</ref><ref>Brand, W.A., 1996. High precision isotope ratio monitoring techniques in mass spectrometry. Journal of Mass Spectrometry, 31(3), pp.225-235. [https://doi.org/10.1002/(sici)1096-9888(199603)31:3<225::aid-jms319>3.0.co;2-l doi: 10.1002/(SICI)1096-9888(199603)31:3<225::AID-JMS319>3.0.CO;2-L]</ref> introduced the era of continuous flow compound specific mass spectrometry by interfacing a gas chromatograph via a sample preparatory oxidation system to a stable '''isotope ratio mass spectrometry''' system. By thus lowering detection limits by up to 5 orders of magnitude and reducing analytical and sample preparation time from hours to minutes, continuous flow techniques allowed CSIA to become widely applied by providing the ability to measure stable isotope ratios for compounds of environmental concern at various spatiotemporal scales in '''environmental chemistry, biogeochemistry''', and contaminant '''hydrogeology'''.
+
[[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>]]
 +
[[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)]]
 +
 
 +
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>.
 +
 
 +
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>
 +
 
 +
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).
  
==Carbon Isotope CSIA==
+
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"/>.
The element carbon has two '''stable isotopes''', <sup>12</sup>C and <sup>13</sup>C. Typically occurring under natural conditions in the ratio of 99:1, the small relative differences in the ratio of <sup>13</sup>C/<sup>12</sup>C for a given compound (called '''stable isotope ratio''') provide a wealth of information relevant to the investigation and remediation of contaminated sites and the environment<ref name = "Hunkeler2008"/>. The measured <sup>13</sup>C/<sup>12</sup>C ratio is normalized with respect to international isotopic standards and expressed in '''delta notation''' (e.g. δ<sup>13</sup>C), in units of permil (parts per thousand or '''per mille'''). Isotopic standards have been administered centrally since the 1950s through the '''International Atomic Energy Agency''', and in the U.S. through the '''National Institute of Standards and Technology''', ensuring that all stable isotope laboratories worldwide are cross-calibrated to the same standards ensuring global consistency of results within both public and private laboratories<ref name = "Hunkeler2008"/>.
 
  
==Applications to Environmental Remediation and Restoration – Forensics==
+
{| class="wikitable" style="float: right; text-align: center; margin-left: auto; margin-right: auto;"
Both naturally sourced contaminants (e.g. '''petroleum hydrocarbons''') and man-made industrial organic contaminants (e.g. '''organochlorides, CFCs''', gasoline additives such as '''methyl tert-butyl ether (MTBE) ''') can have different δ<sup>13</sup>C values due to differences in mechanisms and source materials used in their synthesis. This provides the basis for using CSIA as a '''forensic science''' tool<ref>Mancini, S.A., Lacrampe-Couloume, G. and Lollar, B.S., 2008. Source differentiation for benzene and chlorobenzene groundwater contamination: A field application of stable carbon and hydrogen isotope analyses. Environmental Forensics, 9(2-3), pp.177-186. [http://dx.doi.org/10.1080/15275920802119086 doi: 10.1080/15275920802119086]</ref>. Both different contamination sources and different spills from the same source may potentially have distinct CSIA signatures that can be applied to attribute responsibility in a mixed contaminant plume, such as in a situation where there is off-site migration and impact. In most cases, knowledge of the initial spill material is not possible, but the approach is not dependent on that precondition. Differentiating different potential “source” areas at a site relative to each other can be achieved by comparing different areas of the site in the context of the geologic and hydrogeologic conceptual models to test source zone apportionment<ref name = "Hunkeler2008"/>. CSIA does not provide a silver bullet, as there can be significant overlap in carbon isotope signatures, but successful applications have taken advantage of the additional certainty afforded by coupling carbon isotope variations with additional constraints provided by dual isotope (2D) or triple isotope (3D) signatures (usually '''hydrogen isotope''' signatures and/or '''chlorine''' isotope signatures)<ref name = "Hunkeler2008"/><ref name= "Hunkeler2001">Hunkeler, D., Andersen, N., Aravena, R., Bernasconi, S.M. and Butler, B.J., 2001. Hydrogen and carbon isotope fractionation during aerobic biodegradation of benzene. Environmental Science & Technology, 35(17), pp.3462-3467. [https://doi.org/10.1021/es0105111 doi: 10.1021/es0105111]</ref><ref>Mancini, S.A., Ulrich, A.C., Lacrampe-Couloume, G., Sleep, B., Edwards, E.A. and Lollar, B.S., 2003. Carbon and hydrogen isotopic fractionation during anaerobic biodegradation of benzene. Applied and Environmental Microbiology, 69(1), pp.191-198. [https://doi.org/10.1128/aem.69.1.191-198.2003 doi: 10.1128/AEM.69.1.191-198.2003]</ref><ref>Shouakar-Stash, O., Frape, S.K. and Drimmie, R.J., 2003. Stable hydrogen, carbon and chlorine isotope measurements of selected chlorinated organic solvents. Journal of Contaminant Hydrology, 60(3), pp.211-228. [https://doi.org/10.1016/s0169-7722(02)00085-2 doi: 10.1016/S0169-7722(02)00085-2]</ref><ref name= "Kuder2005">Kuder, T., Wilson, J.T., Kaiser, P., Kolhatkar, R., Philp, P. and Allen, J., 2005. Enrichment of stable carbon and hydrogen isotopes during anaerobic biodegradation of MTBE: microcosm and field evidence. Environmental Science & Technology, 39(1), pp.213-220. [https://doi.org/10.1021/es040420e doi: 10.1021/es040420e]</ref><ref name= "Zwank2005">Zwank, L., Berg, M., Elsner, M., Schmidt, T.C., Schwarzenbach, R.P. and Haderlein, S.B., 2005. New evaluation scheme for two-dimensional isotope analysis to decipher biodegradation processes: Application to groundwater contamination by MTBE. Environmental Science & Technology, 39(4), pp.1018-1029. [https://doi.org/10.1021/es049650j doi: 10.1021/es049650j]</ref><ref>Sessions, A.L., 2006. Isotope‐ratio detection for gas chromatography. Journal of Separation Science, 29(12), pp.1946-1961. [https://doi.org/10.1002/jssc.200600002 doi: 10.1002/jssc.200600002]</ref>. Forensic applications of CSIA can include nitrogen isotope signatures (e.g. nitroanilines and other N-containing compounds '''Kartenbach et al., 2006'''<ref name= "Penning2007">Penning, H. and Elsner, M., 2007. Intramolecular carbon and nitrogen isotope analysis by quantitative dry fragmentation of the phenylurea herbicide isoproturon in a combined injector/capillary reactor prior to GC separation. Analytical Chemistry, 79(21), pp.8399-8405. [https://doi.org/10.1021/ac071420a doi 10.1021/ac071420a]</ref><ref>Meyer, A.H., Penning, H., Lowag, H. and Elsner, M., 2008. Precise and accurate compound specific carbon and nitrogen isotope analysis of atrazine: critical role of combustion oven conditions. Environmental Science & Technology, 42(21), pp.7757-7763. [https://doi.org/10.1021/es800534h doi: 10.1021/es800534h]</ref> or other elements relevant to the contaminant of concern.
+
|+ 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.)
 +
|-
 +
! Military Range Type !! Analyte !! Range<br/>(mg/kg) !! Median<br/>(mg/kg) !! RSD<br/>(%)
 +
|-
 +
| colspan="5" style="text-align: left;" | '''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
 +
|-
 +
| colspan="5" style="text-align: left;" | '''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
 +
|-
 +
| colspan="5" style="text-align: left; background-color: white;" | * For incremental samples, 30-100 increments and 3-10 replicate samples were collected.
 +
|}
  
==Quantifying and Monitoring Remediation Processes==
+
==Incremental Sampling Approach==
Many processes that act on contaminants once they enter the environment can affect the relative abundance of isotopes in the compound of interest and hence the <sup>13</sup>C/<sup>12</sup>C ratio. This effect is called '''isotope fractionation''' and is the key to CSIA providing insight and information on those processes<ref name= "Faure2004">Faure, G. and Mensing, T.M., 2005. Isotopes: principles and applications. John Wiley & Sons Inc.</ref>. While both degradative (e.g. chemical or biological transformation of contaminant to degradation products) and non-degradative processes (e.g. phase changes such as volatilization, sorption, diffusion) have the potential to result in carbon isotope fractionation, to date the largest fractionation signals are related to processes in which bonds are broken<ref name = "Hunkeler2008"/>. This results from the '''kinetic isotope''' effect and the fact that bonds containing a single heavy stable isotope (e.g. <sup>13</sup>C) have a lower '''zero point energy''' and corresponding larger '''activation energy''' than bonds containing exclusively light isotopes (e.g. <sup>12</sup>C). Effectively this means bonds containing a heavy isotope are harder to break, and the rate of transformation then of compounds containing exclusively light isotopes is faster than the rate of transformation of compounds containing a heavy isotope<ref name= "Faure2004"/>.
+
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]]
  
==CSIA Signals of Transformation and Remediation==
+
DUs can vary in shape (Figure 4), size, number of increments, and number of replicates according to a project’s data quality objectives.
The net outcome of fractionation is that a contaminant that has been undergoing degradation can provide a dramatic signal of transformation, as its isotopic signature can have a higher <sup>13</sup>C/<sup>12</sup>C ratio than before transformation<ref>Meckenstock, R.U., Morasch, B., Warthmann, R., Schink, B., Annweiler, E., Michaelis, W. and Richnow, H.H., 1999. 13C/12C isotope fractionation of aromatic hydrocarbons during microbial degradation. Environmental Microbiology, 1(5), pp.409-414. [https://doi.org/10.1046/j.1462-2920.1999.00050.x doi: 10.1046/j.1462-2920.1999.00050.x]</ref><ref>Hunkeler, D., Aravena, R. and Butler, B.J., 1999. Monitoring microbial dechlorination of tetrachloroethene (PCE) in groundwater using compound-specific stable carbon isotope ratios: microcosm and field studies. Environmental Science & Technology, 33(16), pp.2733-2738. [https://doi.org/10.1021/es981282u  doi: 10.1021/es981282u]</ref><ref>Lollar, B.S., Slater, G.F., Ahad, J., Sleep, B., Spivack, J., Brennan, M. and MacKenzie, P., 1999. Contrasting carbon isotope fractionation during biodegradation of trichloroethylene and toluene: Implications for intrinsic bioremediation. Organic Geochemistry, 30(8), pp.813-820. [https://doi.org/10.1016/s0146-6380(99)00064-9 doi: 10.1016/S0146-6380(99)00064-9]</ref>. The obvious corollary is that the products of degradation will be preferentially enriched in the light isotopes (lower <sup>13</sup>C/<sup>12</sup>C ratios) than the parent compound from which they are derived. This principle holds for both chemical transformation and biologically mediated transformation reactions, and the principles described above apply to other elements such as hydrogen, nitrogen, oxygen, and chlorine as well.
 
  
Laboratory experiments have shown that not only does fractionation during transformation provide a strong signal of degradation, but also that signal is highly reproducible<ref name = "Hunkeler2008"/>. For many organic contaminants of interest, the relationship between the change in carbon isotope signature and the degree of degradation is governed by a quantitative relationship – the Rayleigh equation<ref>Mariotti, A., Germon, J.C., Hubert, P., Kaiser, P., Letolle, R., Tardieux, A. and Tardieux, P., 1981. Experimental determination of nitrogen kinetic isotope fractionation: some principles; illustration for the denitrification and nitrification processes. Plant and soil, 62(3), pp.413-430. [https://doi.org/10.1007/bf02374138 doi: 10.1007/BF02374138]</ref>. Specifically, for a given compound and degradation pathway or mechanism, the measured difference in carbon isotope signatures can be quantitatively related to a specific degree of transformation (e.g. fraction or percentage of remaining contaminant) by the equation:
+
[[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)]]
  
Equation 1:  R<sub>t</sub> = R<sub>0</sub> f<sup>(α-1)</sup>  
+
==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.
  
where R<sub>t</sub> is the stable isotope ratio (<sup>13</sup>C/<sup>12</sup>C) of the compound at time t, R<sub>0</sub> is the initial isotope value of the compound and f is the fraction of remaining contaminant expressed as f = 0. The stable isotope fractionation factor is the factor alpha (α) where α = (1000 + δ<sup>13</sup>C<sub>a</sub>)/(1000+ δ<sup>13</sup>C<sub>b</sub>). Subscripts a and b may represent a compound at time zero (t<sub>0</sub>) and at a later point (t) in a reaction; or a compound in a source zone, versus a compound in a downgradient well for instance.
+
[[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>]]
  
Equation 1 can be rearranged to produce Equation 2 (see Hunkeler et al. 2008 for details)<ref name = "Hunkeler2008"/>:
+
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.
  
Equation 2: [[File:Lollar-Article 1-Equation 2.PNG|300 px]]
+
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>.
  
where δ<sup>13</sup>C<sub>groundwater</sub> is the measure of the isotope ratio in the organic contaminant in the sample of groundwater, where δ<sup>13</sup>C<sub>source</sub> is the isotopic ratio in the un-fractionated organic contaminant before biodegradation has occurred, and epsilon (ε), the stable isotope enrichment factor, is defined as ε = (α-1) * 1000.
+
==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.
  
==Implications for Remediation==
+
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 quantitative relationships controlling carbon isotope fractionation during transformation means that CSIA not only provides a signal of whether transformation is taking place, but can provide a quantitative measure of the extent of transformation independent of conventional metrics based on changes in concentration. In some cases, due to signal sensitivity, changes in stable carbon isotope fractionation can be identified in advance of definitive reduction in contaminant concentrations, or before appearance of daughter products, providing an “early warning system” for confirmation of remediation<ref name= "Morrill2005">Morrill, P.L., Lacrampe-Couloume, G., Slater, G.F., Sleep, B.E., Edwards, E.A., McMaster, M.L., Major, D.W. and Lollar, B.S., 2005. Quantifying chlorinated ethene degradation during reductive dechlorination at Kelly AFB using stable carbon isotopes. Journal of Contaminant Hydrology, 76(3), pp.279-293. [https://doi.org/10.1016/j.jconhyd.2004.11.002 doi: 10.1016/j.jconhyd.2004.11.002]</ref>. This is particularly advantageous for field studies since changes in contaminant concentration result not only from transformation processes, but from contaminant transport and dispersal. For this reason, decreasing concentrations of contaminants alone are insufficient evidence that a site is undergoing transformation towards clean-up goals<ref>Wiedemeier, T.H., Wilson, J.T., Kampbell, D.H., Miller, R.N. and Hansen, J.E., 1995. Technical Protocol for Implementing Intrinsic Remediation with Long-Term Monitoring for Natural Attenuation of Fuel Contamination Dissolved in Groundwater. U.S. Air Force Center for Environmental Excellence, Technology Transfer Division, Brooks Air Force Base, San Antonio, Texas]</ref><ref>Wiedemeier, T.H.,  Swanson, M.A., Moutoux, D.E., Gordon, E.K., Wilson, J.T., Wilson, B.H., Kampbell, D.H., Haas, P.E., Hansen, J.E., and Chapelle, F.H. 1998. Technical protocol for evaluating natural attenuation of chlorinated solvents in ground water.  EPA-600-R-98-128. [http://www.environmentalrestoration.wiki/images/2/27/Wiedemeier-1998-Technical_Protocol_for_Evaluating_Natuaral_Attenuation.pdf Report pdf]</ref>. In contrast, as transport and dispersal processes are largely neutral with respect to carbon isotope signals, a carbon isotope enrichment signal in the contaminants of concern provides a direct line of evidence that transformation is occurring and as outlined above, a second independent quantification of transformation rates that can provide constraints on conventional approaches to derive remediation rates and timelines<ref>Sherwood Lollar, B., Slater, G.F., Sleep, B., Witt, M., Klecka, G.M., Harkness, M. and Spivack, J., 2001. Stable carbon isotope evidence for intrinsic bioremediation of tetrachloroethene and trichloroethene at area 6, Dover Air Force Base. Environmental Science & Technology, 35(2), pp.261-269. [https://doi.org/10.1021/es001227x doi: 10.1021/es001227x]</ref><ref name= "Morrill2005"/><ref>McKelvie, J.R., Mackay, D.M., de Sieyes, N.R., Lacrampe-Couloume, G. and Lollar, B.S., 2007. Quantifying MTBE biodegradation in the Vandenberg Air Force Base ethanol release study using stable carbon isotopes. Journal of contaminant hydrology, 94(3), pp.157-165. [https://doi.org/10.1016/j.jconhyd.2007.05.008 doi: 10.1016/j.jconhyd.2007.05.008]</ref>.
 
  
CSIA provides additional value to environmental investigation and remediation – the ability to pinpoint which of a variety of possible degradation mechanisms may be dominating at a contaminated site – because the degree of fractionation is reaction specific. A specific example of this is 1,2-dichloroethane, an industrial chemical used in PVC production, production of furniture, upholstery and automobile parts and a common environmental contaminant of concern. Microbial biodegradation of this compound by in the environment is common, but different organisms degrade the compound via different pathways (e.g. involving a C-Cl bond cleavage, or a C-H bond cleavage). As a result, CSIA can be used to positively identify which of the two biodegradation pathways is operative at a site – information that can be critical to optimizing a remediation strategy<ref>Hunkeler, D. and Aravena, R., 2000. Evidence of Substantial Carbon Isotope Fractionation among Substrate, Inorganic Carbon, and Biomass during Aerobic Mineralization of 1, 2-Dichloroethane by Xanthobacter autotrophicus. Applied and Environmental Microbiology, 66(11), pp.4870-4876. [https://doi.org/10.1128/aem.66.11.4870-4876.2000 doi: 10.1128/AEM.66.11.4870-4876.2000]</ref><ref>Hirschorn, S.K., Grostern, A., Lacrampe-Couloume, G., Edwards, E.A., MacKinnon, L., Repta, C., Major, D.W. and Lollar, B.S., 2007. Quantification of biotransformation of chlorinated hydrocarbons in a biostimulation study: Added value via stable carbon isotope analysis. Journal of Contaminant Hydrology, 94(3), pp.249-260. [https://doi.org/10.1016/j.jconhyd.2007.07.001 doi: 10.1016/j.jconhyd.2007.07.001]</ref>. In other examples, CSIA has been a critical tool in deciphering the biodegradation potential and remediation mechanisms for benzene<ref name= "Hunkeler2001"/>'''Mancini et al. 2002'''<ref>Mancini, S.A., Devine, C.E., Elsner, M., Nandi, M.E., Ulrich, A.C., Edwards, E.A. and Sherwood Lollar, B., 2008. Isotopic evidence suggests different initial reaction mechanisms for anaerobic benzene biodegradation. Environmental Science & Technology, 42(22), pp.8290-8296. [https://doi.org/10.1021/es801107g doi: 10.1021/es801107g]</ref><ref>Fischer, A., Gehre, M., Breitfeld, J., Richnow, H.-H., 2009. Carbon and hydrogen isotope fractionation of benzene during biodegradation under sulphate-reducing conditions: A laboratory to field site approach. Rapid Communications in Mass Spectrometry 236:2439-2447.  [https://doi.org/10.1002/rcm.4049 doi:10.1002/rcm.4049]</ref>, methyl tert-butyl ether  (MTBE) <ref name= "Zwank2005"/><ref>McKelvie, J.R., Hyman, M.R., Elsner, M., Smith, C., Aslett, D.M., Lacrampe-Couloume, G. and Sherwood Lollar, B., 2009. Isotopic fractionation of methyl tert-butyl ether suggests different initial reaction mechanisms during aerobic biodegradation. Environmental Science & Technology, 43(8), pp.2793-2799. [https://doi.org/10.1021/es803307y doi: 10.1021/es803307y]</ref><ref>Elsner, M., McKelvie, J., Lacrampe Couloume, G. and Sherwood Lollar, B., 2007. Insight into methyl tert-butyl ether (MTBE) stable isotope fractionation from abiotic reference experiments. Environmental Science & Technology, 41(16), pp.5693-5700. [https://doi.org/10.1021/es070531o doi: 10.1021/es070531o]</ref><ref name= "Kuder2005"/> and other priority pollutants. In related applications, where abiotic and biotic transformation of a compound occurs via different pathways and mechanisms, CSIA can contribute to differentiating between the relative contributions of chemical versus biological transformation<ref>Elsner, M., Chartrand, M., VanStone, N., Lacrampe Couloume, G. and Sherwood Lollar, B., 2008. Identifying abiotic chlorinated ethene degradation: characteristic isotope patterns in reaction products with nanoscale zero-valent iron. Environmental Science & Technology, 42(16), pp.5963-5970. [https://doi.org/10.1021/es8001986  doi: 10.1021/es8001986]</ref><ref>Elsner, M., Couloume, G.L., Mancini, S., Burns, L. and Lollar, B.S., 2010. Carbon isotope analysis to evaluate nanoscale Fe (O) treatment at a chlorohydrocarbon contaminated site. Groundwater Monitoring & Remediation, 30(3), pp.79-95. [https://doi.org/10.1111/j.1745-6592.2010.01294.x doi: 10.1111/j.1745-6592.2010.01294.x]</ref>.  
+
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).
  
Not all transformation processes result in significant fractionation. Fractionation factors can be small to non-existent simply due to the decreased significance of fractionation related to one carbon in a molecule with many carbon atoms (naphthalene paper), or due to the highly stable nature of, for instance, carbon atoms in an aromatic ring structure<ref>Morasch, B., Richnow, H.H., Schink, B. and Meckenstock, R.U., 2001. Stable hydrogen and carbon isotope fractionation during microbial toluene degradation: mechanistic and environmental aspects. Applied and Environmental Microbiology, 67(10), pp.4842-4849. [https://doi.org/10.1128/aem.67.10.4842-4849.2001 doi: 10.1128/AEM.67.10.4842-4849.2001]</ref>. In such cases the development of models to determine intrinsic versus apparent kinetic isotope effects<ref>Elsner, M., Zwank, L., Hunkeler, D. and Schwarzenbach, R.P., 2005. A new concept linking observable stable isotope fractionation to transformation pathways of organic pollutants. Environmental Science & Technology, 39(18), pp.6896-6916. [https://doi.org/10.1021/es0504587 doi: 10.1021/es0504587]</ref>; use of multi-isotope analysis (2D or 3D)<ref name= "Penning2007"/> or novel techniques related to position specific isotope analysis targeted to specific individual atoms on the compound '''McKelvie et al., 2010'''<ref>Julien, M., Parinet, J., Nun, P., Bayle, K., Höhener, P., Robins, R.J. and Remaud, G.S., 2015. Fractionation in position-specific isotope composition during vaporization of environmental pollutants measured with isotope ratio monitoring by 13 C nuclear magnetic resonance spectrometry. Environmental Pollution, 205, pp. 299-306. [https://doi.org/10.1016/j.envpol.2015.05.047 doi: 10.1016/j.envpol.2015.05.047]</ref><ref>Gilbert, A., Yamada, K., Suda, K., Ueno, Y. and Yoshida, N., 2016. Measurement of position-specific 13 C isotopic composition of propane at the nanomole level. Geochimica et Cosmochimica Acta, 177, pp.205-216. [http://dx.doi.org/10.1016/j.gca.2016.01.017 doi: 10.1016/j.gca.2016.01.017]</ref> can be applied. The presence of additional rate-limiting steps in the transformation reaction can suppress the observed fractionation in ways which may complicate the above quantification of transformation governing Equation 1, yet yield other important information for instance about transport effects '''Nijenhuis et al., 2005''' or the efficiency of the enzymes involved in biodegradation<ref>Mancini, S.A., Hirschorn, S.K., Elsner, M., Lacrampe-Couloume, G., Sleep, B.E., Edwards, E.A. and Sherwood Lollar, B., 2006. Effects of trace element concentration on enzyme controlled stable isotope fractionation during aerobic biodegradation of toluene. Environmental Science & Technology, 40(24), pp.7675-7681. [https://doi.org/10.1021/es061363n doi: 10.1021/es061363n]</ref><ref>Lollar, B.S., Hirschorn, S., Mundle, S.O., Grostern, A., Edwards, E.A. and Lacrampe-Couloume, G., 2010. Insights into enzyme kinetics of chloroethane biodegradation using compound specific stable isotopes. Environmental Science & Technology, 44(19), pp.7498-7503. [http://dx.doi.org/10.1021/es101330r doi: 10.1021/es101330r]</ref>.
+
<li style="display: inline-block;">[[File:Beal1w2 Fig6.png|thumb|200 px|Figure 6: CMIST soil sampling tool (top) and with ejected increment core using a large diameter tip (bottom).]]</li>
 +
<li style="display: inline-block;">[[File:Beal1w2 Fig7.png|thumb|200 px|Figure 7: Two person sampling team using CMIST, bag-lined bucket, and increment counter. (Photos: Matthew Bigl)]]</li>
 +
<li style="display: inline-block;">[[File:Beal1w2 Fig8.png|thumb|200 px|Figure 8: Effect of machine grinding on RDX and TNT concentration and precision in soil from a hand grenade range. Data from Walsh et al.<ref>Walsh, M.E., Ramsey, C.A. and Jenkins, T.F., 2002. The effect of particle size reduction by grinding on subsampling variance for explosives residues in soil. Chemosphere, 49(10), pp.1267-1273. [https://doi.org/10.1016/S0045-6535(02)00528-3 doi: 10.1016/S0045-6535(02)00528-3]</ref> ]]</li>
 +
<li style="display: inline-block;">[[File:Beal1w2 Fig9.png|thumb|200 px|Figure 9: Effect of puck milling time on 2,4-DNT concentration and precision in soil from a firing point. Data from Walsh et al.<ref>Walsh, M.E., Ramsey, C.A., Collins, C.M., Hewitt, A.D., Walsh, M.R., Bjella, K.L., Lambert, D.J. and Perron, N.M., 2005. Collection methods and laboratory processing of samples from Donnelly Training Area Firing Points, Alaska, 2003 (No. ERDC/CRREL-TR-05-6). [[media:Walsh-2005 ERDC-CRREL TR-05-6.pdf| Report.pdf]]</ref>.]]</li>
 +
<li style="display: inline-block;">[[File:Beal1w2 Fig10.png|thumb|200 px|center|Figure 10: Incremental sub-sampling of a milled soil sample spread out on aluminum foil.]]</li>
  
==Conclusions==
+
==Analysis==
Applications of CSIA are dependent on background information about the degree of fractionation associated with a specific chemical reaction or biodegradation pathway. While fractionation can be calculated ''ab initio'' (from the beginning), fractionation factors are typically empirically derived from laboratory experiments and other approaches. Recent guidance documents and review papers provide an essential resource with database compilations of this knowledge to date<ref>Meckenstock, R.U., Morasch, B., Griebler, C. and Richnow, H.H., 2004. Stable isotope fractionation analysis as a tool to monitor biodegradation in contaminated acquifers. Journal of Contaminant Hydrology, 75(3), pp.215-255. [https://doi.org/10.1016/j.jconhyd.2004.06.003 doi: 10.1016/j.jconhyd.2004.06.003]</ref><ref name = "Hunkeler2008"/>).
+
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