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==Supercritical Water Oxidation (SCWO)==
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==Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)==  
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Supercritical water oxidation (SCWO) is a single step [[Wikipedia: Wet oxidation | wet oxidation]] process that transforms organic matter into water, carbon dioxide and, depending on the waste undergoing treatment, an inert mineral solid residue. The process is highly effective and can treat a variety of wet wastes without dewatering. The SCWO technology allows for the complete destruction of persistent and toxic organic contaminants such as [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | perfluoroalkyl and polyfluoroalkyl substances (PFAS)]], [[1,4-Dioxane | 1,4-dioxane]], and many more.  
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Sediment porewater dialysis passive samplers, also known as “peepers,” are sampling devices that allow the measurement of dissolved inorganic ions in the porewater of a saturated sediment. Peepers function by allowing freely-dissolved ions in sediment porewater to diffuse across a micro-porous membrane towards water contained in an isolated compartment that has been inserted into sediment. Once retrieved after a deployment period, the resulting sample obtained can provide concentrations of freely-dissolved inorganic constituents in sediment, which provides measurements that can be used for understanding contaminant fate and risk. Peepers can also be used in the same manner in surface water, although this article is focused on the use of peepers in sediment.  
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<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):'''
 
'''Related Article(s):'''
  
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* [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
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*[[Contaminated Sediments - Introduction]]
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* [[PFAS Transport and Fate]]
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*[[Contaminated Sediment Risk Assessment]]
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* [[Chlorinated Solvents]]
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*[[In Situ Treatment of Contaminated Sediments with Activated Carbon]]
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*[[Passive Sampling of Munitions Constituents]]
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*[[Sediment Capping]]
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*[[Mercury in Sediments]]
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*[[Passive Sampling of Sediments]]
  
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'''Contributor(s):''' [[Kobe Nagar]] and [[Dr. Marc Deshusses]]
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'''Contributor(s):'''  
 +
 
 +
*Florent Risacher, M.Sc.
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*Jason Conder, Ph.D.
  
 
'''Key Resource(s):'''
 
'''Key Resource(s):'''
  
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*Treatment of municipal sewage sludge in supercritical water: A review<ref name="Qian2016">Qian, L., Wang, S., Xu, D., Guo, Y., Tang, X., and Wang, L., 2016. Treatment of municipal sewage sludge in supercritical water: A review. Water Research, 89, pp. 118-131.  [https://doi.org/10.1016/j.watres.2015.11.047 DOI: 10.1016/j.watres.2015.11.047]&nbsp;nbsp; Free download from: [https://www.researchgate.net/profile/Shuzhong-Wang/publication/284563832_Treatment_of_Municipal_Sewage_Sludge_in_Supercritical_Water_a_Review/links/5d9b63b6299bf1c363fef63e/Treatment-of-Municipal-Sewage-Sludge-in-Supercritical-Water-a-Review.pdf ResearchGate]</ref>.
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*A review of peeper passive sampling approaches to measure the availability of inorganics in sediment porewater<ref>Risacher, F.F., Schneider, H., Drygiannaki, I., Conder, J., Pautler, B.G., and Jackson, A.W., 2023. A Review of Peeper Passive Sampling Approaches to Measure the Availability of Inorganics in Sediment Porewater. Environmental Pollution, 328, Article 121581. [https://doi.org/10.1016/j.envpol.2023.121581 doi: 10.1016/j.envpol.2023.121581]&nbsp;&nbsp;[[Media: RisacherEtAl2023a.pdf | Open Access Manuscript]]</ref>
  
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*Supercritical Water Oxidation – Current Status of Full-scale Commercial Activity for Waste Destruction<ref name="Marrone2013">Marrone, P.A., 2013. Supercritical Water Oxidation – Current Status of Full-scale Commercial Activity for Waste Destruction. Journal of Supercritical Fluids, 79, pp. 283-288. [https://doi.org/10.1016/j.supflu.2012.12.020 DOI: 10.1016/j.supflu.2012.12.020]&nbsp;&nbsp; Author’s manuscript available from: [https://semspub.epa.gov/work/06/9545963.pdf US EPA]</ref>.
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*Best Practices User’s Guide: Standardizing Sediment Porewater Passive Samplers for Inorganic Constituents of Concern<ref name="RisacherEtAl2023">Risacher, F.F., Nichols, E., Schneider, H., Lawrence, M., Conder, J., Sweett, A., Pautler, B.G., Jackson, W.A., Rosen, G., 2023b. Best Practices User’s Guide: Standardizing Sediment Porewater Passive Samplers for Inorganic Constituents of Concern, ESTCP ER20-5261. [https://serdp-estcp.mil/projects/details/db871313-fbc0-4432-b536-40c64af3627f Project Website]&nbsp;&nbsp;[[Media: ER20-5261BPUG.pdf | Report.pdf]]</ref>
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*[https://serdp-estcp.mil/projects/details/db871313-fbc0-4432-b536-40c64af3627f/er20-5261-project-overview Standardizing Sediment Porewater Passive Samplers for Inorganic Constituents of Concern, ESTCP Project ER20-5261]
  
 
==Introduction==
 
==Introduction==
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Supercritical water oxidation (SCWO) is an [[Wikipedia: Advanced oxidation process]] that holds enormous potential for the treatment of a wide range of organic wastes, in particular concentrated wet wastes in slurries such as biosolids, sludges, agricultural wastes, chemical wastes with recalcitrant chemicals such as [[perfluoroalkyl and poly substances (PFAS)]], and many more. SCWO relies on the unique reactivity and transport properties that occur when an aqueous waste stream is brought above the critical point of water (374&deg;C and 218 atm, or 704&deg;F and 3200 psi, see phase diagram in Figure 1). Supercritical water is a dense single phase with transport properties similar to those of a gas, and solvent properties comparable to those of a non-polar solvent
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Biologically available inorganic constituents associated with sediment toxicity can be quantified by measuring the freely-dissolved fraction of contaminants in the porewater<ref>Conder, J.M., Fuchsman, P.C., Grover, M.M., Magar, V.S., Henning, M.H., 2015. Critical review of mercury SQVs for the protection of benthic invertebrates. Environmental Toxicology and Chemistry, 34(1), pp. 6-21. [https://doi.org/10.1002/etc.2769 doi: 10.1002/etc.2769]&nbsp;&nbsp; [[Media: ConderEtAl2015.pdf | Open Access Article]]</ref><ref name="ClevelandEtAl2017">Cleveland, D., Brumbaugh, W.G., MacDonald, D.D., 2017. A comparison of four porewater sampling methods for metal mixtures and dissolved organic carbon and the implications for sediment toxicity evaluations. Environmental Toxicology and Chemistry, 36(11), pp. 2906-2915. [https://doi.org/10.1002/etc.3884 doi: 10.1002/etc.3884]</ref>. Classical sediment porewater analysis usually consists of collecting large volumes of bulk sediments which are then mechanically squeezed or centrifuged to produce a supernatant, or suction of porewater from intact sediment, followed by filtration and collection<ref name="GruzalskiEtAl2016">Gruzalski, J.G., Markwiese, J.T., Carriker, N.E., Rogers, W.J., Vitale, R.J.,  Thal, D.I., 2016. Pore Water Collection, Analysis and Evolution: The Need for Standardization. In: Reviews of Environmental Contamination and Toxicology, Vol. 237, pp. 37–51. Springer. [https://doi.org/10.1007/978-3-319-23573-8_2 doi: 10.1007/978-3-319-23573-8_2]</ref>. The extraction and measurement processes present challenges due to the heterogeneity of sediments, physical disturbance, high reactivity of some complexes, and interaction between the solid and dissolved phases, which can impact the measured concentration of dissolved inorganics<ref>Peijnenburg, W.J.G.M., Teasdale, P.R., Reible, D., Mondon, J., Bennett, W.W., Campbell, P.G.C., 2014. Passive Sampling Methods for Contaminated Sediments: State of the Science for Metals. Integrated Environmental Assessment and Management, 10(2), pp. 179–196. [https://doi.org/10.1002/ieam.1502 doi: 10.1002/ieam.1502]&nbsp;&nbsp; [[Media: PeijnenburgEtAl2014.pdf | Open Access Article]]</ref>. For example, sampling disturbance can affect redox conditions<ref name="TeasdaleEtAl1995">Teasdale, P.R., Batley, G.E., Apte, S.C., Webster, I.T., 1995. Pore water sampling with sediment peepers. Trends in Analytical Chemistry, 14(6), pp. 250–256. [https://doi.org/10.1016/0165-9936(95)91617-2 doi: 10.1016/0165-9936(95)91617-2]</ref><ref>Schroeder, H., Duester, L., Fabricius, A.L., Ecker, D., Breitung, V., Ternes, T.A., 2020. Sediment water (interface) mobility of metal(loid)s and nutrients under undisturbed conditions and during resuspension. Journal of Hazardous Materials, 394, Article 122543. [https://doi.org/10.1016/j.jhazmat.2020.122543 doi: 10.1016/j.jhazmat.2020.122543]&nbsp;&nbsp; [[Media: SchroederEtAl2020.pdf | Open Access Article]]</ref>, which can lead to under or over representation of inorganic chemical concentrations relative to the true dissolved phase concentration in the sediment porewater<ref>Wise, D.E., 2009. Sampling techniques for sediment pore water in evaluation of reactive capping efficacy. Master of Science Thesis. University of New Hampshire Scholars’ Repository. 178 pages. [https://scholars.unh.edu/thesis/502 Website]&nbsp;&nbsp; [[Media: Wise2009.pdf | Report.pdf]]</ref><ref name="GruzalskiEtAl2016"/>.
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To address the complications with mechanical porewater sampling, passive sampling approaches for inorganics have been developed to provide a method that has a low impact on the surrounding geochemistry of sediments and sediment porewater, thus enabling more precise measurements of inorganics<ref name="ClevelandEtAl2017"/>. Sediment porewater dialysis passive samplers, also known as “peepers,” were developed more than 45 years ago<ref name="Hesslein1976">Hesslein, R.H., 1976. An in situ sampler for close interval pore water studies. Limnology and Oceanography, 21(6), pp. 912-914. [https://doi.org/10.4319/lo.1976.21.6.0912 doi: 10.4319/lo.1976.21.6.0912]&nbsp;&nbsp; [[Media: Hesslein1976.pdf | Open Access Article]]</ref> and refinements to the method such as the use of reverse tracers have been made, improving the acceptance of the technology as decision-making tool.
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==Peeper Designs==
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Peepers (Figure 1) are inert containers with a small volume (typically 1-100 mL) of purified water (“peeper water”) capped with a semi-permeable membrane. Peepers can be manufactured in a wide variety of formats (Figure 2, Figure 3) and deployed in in various ways.
  
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Two designs are commonly used for peepers. Frequently, the designs are close adaptations of the original multi-chamber Hesslein design<ref name="Hesslein1976"/> (Figure 2), which consists of an acrylic sampler body with multiple sample chambers machined into it. Peeper water inside the chambers is separated from the outside environment by a semi-permeable membrane, which is held in place by a top plate fixed to the sampler body using bolts or screws. An alternative design consists of single-chamber peepers constructed using a single sample vial with a membrane secured over the mouth of the vial, as shown in Figure 3, and applied in Teasdale ''et al.''<ref name="TeasdaleEtAl1995"/>, Serbst ''et al.''<ref>Serbst, J.R., Burgess, R.M., Kuhn, A., Edwards, P.A., Cantwell, M.G., Pelletier, M.C.,  Berry, W.J., 2003. Precision of dialysis (peeper) sampling of cadmium in marine sediment interstitial water. Archives of Environmental Contamination and Toxicology, 45(3), pp. 297–305. [https://doi.org/10.1007/s00244-003-0114-5 doi: 10.1007/s00244-003-0114-5]</ref>, Thomas and Arthur<ref name="ThomasArthur2010">Thomas, B., Arthur, M.A., 2010. Correcting porewater concentration measurements from peepers: Application of a reverse tracer. Limnology and Oceanography: Methods, 8(8), pp. 403–413. [https://doi.org/10.4319/lom.2010.8.403 doi: 10.4319/lom.2010.8.403]&nbsp;&nbsp; [[Media: ThomasArthur2010.pdf | Open Access Article]]</ref>, Passeport ''et al.''<ref>Passeport, E., Landis, R., Lacrampe-Couloume, G., Lutz, E.J., Erin Mack, E., West, K., Morgan, S., Lollar, B.S., 2016. Sediment Monitored Natural Recovery Evidenced by Compound Specific Isotope Analysis and High-Resolution Pore Water Sampling. Environmental Science and Technology, 50(22), pp. 12197–12204. [https://doi.org/10.1021/acs.est.6b02961 doi: 10.1021/acs.est.6b02961]</ref>, and Risacher ''et al.''<ref name="RisacherEtAl2023"/>. The vial is filled with deionized water, and the membrane is held in place using the vial cap or an o-ring. Individual vials are either directly inserted into sediment or are incorporated into a support structure to allow multiple single-chamber peepers to be deployed at once over a given depth profile (Figure 3).
  
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Three technologies are well demonstrated for removal of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] from drinking water and non-potable groundwater (as described below):
 
 
   
 
   
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* membrane filtration including [[wikipedia: Reverse osmosis | reverse osmosis (RO)]] and [[Wikipedia: Nanofiltration | nanofiltration (NF)]]
 
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* granular [[Wikipedia: Activated carbon | activated carbon]] (GAC) and powdered activated carbon (PAC) adsorption
 
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* [[wikipedia: Ion_exchange | anion exchange (IX)]] 
 
  
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However, these technologies are less demonstrated for removal of PFAS from more complex matrices such as wastewater and leachate.  
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{| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;"
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Site-specific considerations that affect the selection of optimum treatment technologies for a given site include water chemistry, required flow rate, treatment criteria, waste residual generation, residual disposal options, and operational complexity.  Treatability studies with site water are highly recommended because every site has different factors that may affect engineering design for these technologies.
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|+Table 1. Analyte list with acronyms and CAS numbers.
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|-
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!Compound
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! Acronym
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!CAS Number
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|-
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| 1,2-Dinitrobenzene (surrogate) ||'''1,2-DNB (surr.)''' || 528-29-0
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|-
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| 1,3-Dinitrobenzene || 1,3-DNB || 99-65-0
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|-
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| 1,3,5-Trinitrobenzene || 1,3,5-TNB || 99-35-4
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|-
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| 1,4-Dinitrobenzene || '''1,4-DNB (surr.)''' || 100-25-4
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|-
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| 2-Amino-4,6-dinitrotoluene || 2-Am-4,6-DNT || 35572-78-2
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|-
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| 2-Nitrophenol || '''2-NP''' || 88-75-5
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|-
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| 2-Nitrotoluene || 2-NT || 88-72-2
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|-
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| 2,4-Dinitrophenol || '''2,4-DNP''' || 51-28-5
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|-
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| 2,4-Dinitrotoluene || 2,4-DNT || 121-14-2
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|-
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| 2,4,6-Trinitrophenol || '''Picric Acid (PA)''' || 88-89-1
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|-
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| 2,4,6-Trinitrotoluene || 2,4,6-TNT || 118-96-7
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|-
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| 2,6-Dinitrotoluene || 2,6-DNT || 606-20-2
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|-
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| 3-Nitrotoluene || 3-NT || 99-08-1
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|-
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| 3,5-Dinitroaniline || 3,5-DNA || 618-87-1
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|-
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| 4-Amino-2,6-dinitrotoluene || 4-Am-2,6-DNT || 19406-51-0
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|-
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| 4-Nitrophenol || '''4-NP''' || 100-02-7
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|-
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| 4-Nitrotoluene || 4-NT || 99-99-0
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|-
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| 2,4-Dinitroanisole || '''DNAN''' || 119-27-7
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|-
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| Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine || HMX || 2691-41-0
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|-
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| Nitrobenzene || NB || 98-95-3
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|-
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| Nitroglycerine || NG || 55-63-0
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|-
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| Nitroguanidine || '''NQ''' || 556-88-7
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|-
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| 3-Nitro-1,2,4-triazol-5-one || '''NTO''' || 932-64-9
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|-
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| ''ortho''-Nitrobenzoic acid || '''''o''-NBA (surr.)''' || 552-16-9
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|-
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| Pentaerythritol tetranitrate || PETN || 78-11-5
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|-
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| Hexahydro-1,3,5-trinitro-1,3,5-triazine || RDX || 121-82-4
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|-
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| N-Methyl-N-(2,4,6-trinitrophenyl)nitramide || Tetryl || 479-45-8
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|-
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| colspan="3" style="background-color:white;" | Note: Analytes in '''bold''' are not identified by EPA Method 8330B.
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|}
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[[File: ScircleFig1.png | thumb | 400px | Figure 1. Primary Method labeled chromatograms]]
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[[File: ScircleFig2.png | thumb | 400px | Figure 2. Secondary Method labeled chromatograms]]
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The&nbsp;primary&nbsp;intention of the analytical methods presented here is to support the monitoring of legacy and insensitive munitions contamination on test and training ranges, however legacy and insensitive munitions often accompany each other at demilitarization facilities, manufacturing facilities, and other environmental sites. Energetic materials typically appear on ranges as small, solid particulates and due to their varying functional groups and polarities, can partition in various environmental compartments<ref>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]</ref>. To ensure that contaminants are monitored and controlled at these sites and to sustainably manage them a variety of sample matrices (surface or groundwater, process waters, soil, and tissues) must be considered. (Process water refers to water used during industrial manufacturing or processing of legacy and insensitive munitions.) Furthermore, additional analytes must be added to existing methodologies as the usage of IM compounds changes and as new degradation compounds are identified.  Of note, relatively new IM formulations containing [[Wikipedia: Nitrotriazolone | NTO]], [[Wikipedia: 2,4-Dinitroanisole | DNAN]], and [[Wikipedia: Nitroguanidine | NQ]] are seeing use in [[Wikipedia: IMX-101 | IMX-101]], IMX-104, Pax-21 and Pax-41 (Table 1)<ref>Mainiero, C. 2015. Picatinny Employees Recognized for Insensitive Munitions. U.S. Army, Picatinny Arsenal Public Affairs.  [https://www.army.mil/article/148873/picatinny_employees_recognized_for_insensitive_munitions Open Access Press Release]</ref><ref>Frem, D., 2022. A Review on IMX-101 and IMX-104 Melt-Cast Explosives: Insensitive Formulations for the Next-Generation Munition Systems. Propellants, Explosives, Pyrotechnics, 48(1), e202100312. [https://doi.org/10.1002/prep.202100312 doi: 10.1002/prep.202100312]</ref>.
  
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===Membrane Filtration===
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Sampling procedures for legacy and insensitive munitions are identical and utilize multi-increment sampling procedures found in USEPA Method 8330B Appendix A<ref name= "8330B"/>. Sample hold times, subsampling and quality control requirements are also unchanged. The key differences lie in the extraction methods and instrumental methods. Briefly, legacy munitions analysis of low concentration waters uses a single cartridge reverse phase [[Wikipedia: Solid-phase extraction | SPE]] procedure, and [[Wikipedia: Acetonitrile | acetonitrile]] (ACN) is used for both extraction and [[Wikipedia: Elution | elution]] for aqueous and solid samples<ref name= "8330B"/><ref>United States Environmental Protection Agency (USEPA), 2007. EPA Method 3535A (SW-846) Solid-Phase Extraction (SPE), Revision 1. [https://www.epa.gov/esam/epa-method-3535a-sw-846-solid-phase-extraction-spe USEPA Website]&nbsp; &nbsp;[[Media: epa-3535a.pdf | Method 3535A.pdf]]</ref>. An [[Wikipedia: High-performance_liquid_chromatography#Isocratic_and_gradient_elution | isocratic]] separation via reversed-phase C-18 column with 50:50 methanol:water mobile phase or a C-8 column with 15:85 isopropanol:water mobile phase is used to separate legacy munitions<ref name= "8330B"/>. While these procedures are sufficient for analysis of legacy munitions, alternative solvents, additional SPE cartridges, and a gradient elution are all required for the combined analysis of legacy and insensitive munitions.  
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[[File: revOsmosisPlant.png | thumb | 500px | Figure 1.  A RO municipal drinking water plant in Arizona]]
 
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Given their ability to remove dissolved contaminants at a molecular size level, RO and some NF membranes can be highly effective for PFAS removal. For RO systems (Figure 1), several studies have demonstrated effective removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) (see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature) from drinking water with removal rates well above 90%<ref name="Tang2006">Tang, C.Y., Fu, Q.S., Robertson, A.P., Criddle, C.S., and Leckie, J.O., 2006. Use of Reverse Osmosis Membranes to Remove Perfluorooctane Sulfonate (PFOS) from Semiconductor Wastewater. Environmental Science and Technology, 40(23), pp. 7343-7349.  [https://doi.org/10.1021/es060831q DOI: 10.1021/es060831q]</ref><ref name="Flores2013">Flores, C., Ventura, F., Martin-Alonso, J., and Caixach, J., 2013. Occurrence of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in NE Spanish surface waters and their removal in a drinking water treatment plant that combines conventional and advanced treatments in parallel lines. Science of the Total environment, 461, 618-626.  [https://doi.org/10.1016/j.scitotenv.2013.05.026 DOI: 10.1016/j.scitotenv.2013.05.026]</ref><ref name="Appleman2014">Appleman, T.D., Higgins, C.P., Quiñones, O., Vanderford, B.J., Kolstad, C., Zeigler-Holady, J.C., and Dickenson, E.R., 2014. Treatment of poly- and perfluoroalkyl substances in US full-scale water treatment systems. Water Research, 51, pp. 246-255.  [https://doi.org/10.1016/j.watres.2013.10.067 DOI: 10.1016/j.watres.2013.10.067]</ref>. RO potable water reuse treatment systems implemented in California have also demonstrated effective PFOS and PFOA removal as reported by the Water Research Foundation (WRF)<ref name="Dickenson2016"/>. Analysis of permeate at both sites referenced by the WRF confirmed that short and long chain PFAS concentrations in the treated water were reduced to levels below test method reporting limits.
 
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Full-scale studies using larger effective pore size NF membranes for PFAS removal are limited in number but are promising since NF systems are somewhat less costly than RO and may be nearly as effective in removing PFAS.  Recent laboratory or pilot studies have shown good performance of NF membranes<ref name="Steinle-Darling2008">Steinle-Darling, E., and Reinhard, M., 2008. Nanofiltration for Trace Organic Contaminant Removal: Structure, Solution, and Membrane Fouling Effects on the Rejection of Perfluorochemicals. Environmental Science and Technology, 42(14), pp. 5292-5297. [https://doi.org/10.1021/es703207s DOI: 10.1021/es703207s]&nbsp;&nbsp; Free download from: [https://d1wqtxts1xzle7.cloudfront.net/48926882/es703207s20160918-21142-1xmqco5.pdf?1474189169=&response-content-disposition=inline%3B+filename%3DNanofiltration_for_Trace_Organic_Contami.pdf&Expires=1613000850&Signature=N-ZvvjOJX3TSOQzg7od3Q0LulNSZOqqjfummVEUfmiYlC3VasS4FuBHOgY52Xy~7FrKbOLhx0xx8QHdUsR~fbRTMQNXhiqbEslnU2gda2EcZHMMJj0mf-01wIA3jFIywA7IIabmTd3uMUGsIfT1D0PrGY00RmprYIQBoG3Dg~KjoizdfxYfvEgdZw2C~7D47pPiwMSnavZiGuvO0~dbRF8nawL7Prg91xt5BFTNUQQiIrIlMWc4PhVjzE5Su2CUZqnNlYdAW5Ck7B9lKmmVMPiOgz07vFnyp7m-q4UK3woa~aBFW9Wp~hjqN6vfohn8Hocv5oMpZNamhu8vBbPilKw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA Academia].</ref><ref name="Appleman2013">Appleman, T.D., Dickenson, E.R., Bellona, C., and Higgins, C.P., 2013. Nanofiltration and granular activated carbon treatment of perfluoroalkyl acids. Journal of Hazardous Materials, 260, 740-746.  [https://doi.org/10.1016/j.jhazmat.2013.06.033 DOI: 10.1016/j.jhazmat.2013.06.033]</ref><ref name="Soriano2017">Soriano, Á., Gorri, D., and Urtiaga, A., 2017. Efficient treatment of perfluorohexanoic acid by nanofiltration followed by electrochemical degradation of the NF concentrate. Water Research, 112, 147-156.  [https://doi.org/10.1016/j.watres.2017.01.043 DOI: 10.1016/j.watres.2017.01.043]&nbsp;&nbsp; [[Media: Soriano2017.pdf | Author’s Manuscript.]]</ref><ref name="Zeng2017">Zeng, C., Tanaka, S., Suzuki, Y., Yukioka, S., and Fujii, S., 2017. Rejection of Trace Level Perfluorohexanoic Acid (PFHxA) in Pure Water by Loose Nanofiltration Membrane. Journal of Water and Environment Technology, 15(3), pp. 120-127.  [https://doi.org/10.2965/jwet.16-072 DOI: 10.2965/jwet.16-072]&nbsp;&nbsp; Free download from: [https://www.jstage.jst.go.jp/article/jwet/15/3/15_16-072/_pdf J-STAGE]</ref><ref name="Wang2018">Wang, J., Wang, L., Xu, C., Zhi, R., Miao, R., Liang, T., Yue, X., Lv, Y. and Liu, T., 2018. Perfluorooctane sulfonate and perfluorobutane sulfonate removal from water by nanofiltration membrane: The roles of solute concentration, ionic strength, and macromolecular organic foulants. Chemical Engineering Journal, 332, pp. 787-797.  [https://doi.org/10.1016/j.cej.2017.09.061 DOI: 10.1016/j.cej.2017.09.061]</ref>.
 
  
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Although membrane RO and NF processes are generally capable of providing uniform removal rates relative to short and long chain PFAS compounds (see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature), other aspects of these treatment technologies are more challenging:
+
Previously, analysis of legacy and insensitive munitions required multiple analytical techniques, however the methods presented here combine the two munitions categories resulting in an HPLC-UV method and accompanying extraction methods for a variety of common sample matrices. A secondary HPLC-UV method and a HPLC-MS method were also developed as confirmatory methods. The methods discussed in this article were validated extensively by single-blind round robin testing and subsequent statistical treatment as part of ESTCP [https://serdp-estcp.mil/projects/details/d05c1982-bbfa-42f8-811d-51b540d7ebda ER19-5078]. Wherever possible, the quality control criteria in the Department of Defense Quality Systems Manual for Environmental Laboratories were adhered to<ref>US Department of Defense and US Department of Energy, 2021. Consolidated Quality Systems Manual (QSM) for Environmental Laboratories, Version 5.4. 387 pages. [https://www.denix.osd.mil/edqw/denix-files/sites/43/2021/10/QSM-Version-5.4-FINAL.pdf Free Download]&nbsp; &nbsp;[[Media: QSM-Version-5.4.pdf | QSM Version 5.4.pdf]]</ref>. Analytes included in the methods presented here are found in Table&nbsp;1.
  
−
* Membranes must be flushed and cleaned periodically, such that overall water recovery rates (process water volumes consumed, wasted, and lost vs. treated water volumes produced) are much lower than those for GAC and IX processes. Membrane fouling can be slowed or avoided depending on operating conditions, membrane modifications, and feed modifications<ref name="LeRoux2005">Le Roux, I., Krieg, H.M., Yeates, C.A. and Breytenbach, J.C., 2005. Use of chitosan as an antifouling agent in a membrane bioreactor. Journal of Membrane Science, 248(1-2), pp. 127-136.  [https://doi.org/10.1016/j.memsci.2004.10.005 DOI: 10.1016/j.memsci.2004.10.005]</ref>. Typically, 70-90% of the water supplied into a membrane RO process is recoverable as treated water. The remaining 10-30% is reject containing approximately 4 to 8 times the initial PFAS concentration (depending on recovery rate).
+
The chromatograms produced by the primary and secondary HPLC-UV methods are shown in Figure 1 and Figure 2, respectively. Chromatograms for each detector wavelength used are shown (315, 254, and 210 nm).
  
−
* These cleaning and flushing processes create a continuous liquid waste stream, which periodically includes harsh membrane cleaning chemicals as well as a continuous flow of concentrated membrane reject chemicals (i.e., PFAS) that must be properly managed and disposed of. Management often includes further treatment to remove PFAS from the liquid waste.
+
==Extraction Methods==
 +
[[File: ScircleFig3.PNG |thumb|400px|Figure 3. Triple cartridge SPE setup]]
 +
[[File: ScircleFig4.PNG |thumb|400px|Figure 4. A flow chart of the soil extraction procedure]]
 +
===High&nbsp;Concentration&nbsp;Waters (> 1 ppm)===
 +
Aqueous samples suspected to contain the compounds of interest at concentrations detectable without any extraction or pre-concentration are suitable for analysis by direct injection. The method deviates from USEPA Method 8330B by adding a pH adjustment and use of MeOH rather than ACN for dilution<ref name= "8330B"/>. The pH adjustment is needed to ensure method accuracy for ionic compounds (like NTO or PA) in basic samples. A solution of 1% HCl/MeOH is added to both acidify and dilute the samples to a final acid concentration of 0.5% (vol/vol) and a final solvent ratio of 1:1 MeOH/H<sub><small>2</small></sub>O. The direct injection samples are then ready for analysis.
  
−
* RO and NF systems are inherently more expensive and complicated systems to implement, operate, and maintain compared to adsorption processes. Treatment system operator certification and process monitoring requirements are correspondingly markedly higher for RO and NF than they are for GAC and IX.  
+
===Low Concentration Waters (< 1 ppm)===
 +
Aqueous samples suspected to contain the compounds of interest at low concentrations require extraction and pre-concentration using solid phase extraction (SPE). The SPE setup described here uses a triple cartridge setup shown in Figure 3. Briefly, the extraction procedure loads analytes of interest onto the cartridges in this order: Strata<sup><small>TM</small></sup> X, Strata<sup><small>TM</small></sup> X-A, and Envi-Carb<sup><small>TM</small></sup>. Then the cartridge order is reversed, and analytes are eluted via a two-step elution, resulting in 2 extracts (which are combined prior to analysis). Five milliliters of MeOH is used for the first elution, while 5 mL of acidified MeOH (2% HCl) is used for the second elution. The particular SPE cartridges used are noncritical so long as cartridge chemistries are comparable to those above.  
  
−
* Water feed pressures required to drive flow through membrane RO and NF processes are considerably higher than those involved with GAC and IX processes. This results in reduced process efficiency and higher pumping and electrical operating costs.
+
{| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;"
 +
|+Table 2. Primary HPLC-UV mobile phase gradient method concentrations
 +
|-
 +
| colspan="5" style="background-color:white;"| Method run time = 48 minutes; Column temperature = 25&deg;C<br>Injection volume = 50 &mu;L; Flow rate = 1.0 mL/min<br>Detector wavelengths = 210, 254, and 310 nm
 +
|-
 +
! Time<br>(min)
 +
! Reagent Water<br>(%)
 +
! MeOH<br>(%)
 +
! 0.1% TFA/Water<br>(%)
 +
! ACN<br>(%)
 +
|-
 +
| 0.00 || 89 || 3 || 3 || 5
 +
|-
 +
| 2.00 || 89 || 3 || 3 || 5
 +
|-
 +
| 2.20 || 52 || 40 || 3 || 5
 +
|-
 +
| 12.5 || 52 || 40 || 3 || 5
 +
|-
 +
| 19.0 || 57 ||35 || 3 || 5
 +
|-
 +
| 28.0 || 48 || 44 || 3 || 5
 +
|-
 +
| 32.0 || 48 || 44 || 3 || 5
 +
|-
 +
| 44.0 || 32 || 60 || 3 || 5
 +
|-
 +
| 44.1 || 89 || 3 || 3 || 5
 +
|-
 +
| 48.0 || 89 || 3 || 3 || 5
 +
|}
  
−
* Membrane systems can also be subject to issues with irreversible membrane fouling, clogging, and scaling or other physical membrane damage and failures. Additional water pretreatment and higher levels of monitoring and maintenance are then required, further adding to the higher costs of such systems.
+
===Soils=== 
 +
Soil collection, storage, drying and grinding procedures are identical to the USEPA Method 8330B procedures<ref name= "8330B"/>; however, the solvent extraction procedure differs in the number of sonication steps, sample mass and solvent used. A flow chart of the soil extraction procedure is shown in Figure 4. Soil masses of approximately 2 g and a sample to solvent ratio of 1:5 (g/mL) are used for soil extraction. The extraction is carried out in a sonication bath chilled below 20 ⁰C and is a two-part extraction, first extracting in MeOH (6 hours) followed by a second sonication in 1:1 MeOH:H<sub><small>2</small></sub>O solution (14 hours). The extracts are centrifuged, and the supernatant is filtered through a 0.45 μm PTFE disk filter.  
  
−
===Activated Carbon Adsorption===
+
The solvent volume should generally be 10 mL but if different soil masses are required, solvent volume should be 5 mL/g. The extraction results in 2 separate extracts (MeOH and MeOH:H<sub><small>2</small></sub>O) that are combined prior to analysis.
−
[[File: GAChouse.JPG | thumb| 500px | Figure 2.  Typical private water supply well GAC installation for removal PFAS. Pressure gages and sample ports located before the first (or lead) vessel, at the midpoint, and after the second (or lag) vessel allow monitoring for pressure drop due to fouling and for contaminant breakthrough.]] 
 
−
Activated carbon is a form of carbon processed to have small pores that increase the surface area available for adsorption of constituents from water. Activated carbon is derived from many source materials, including coconut shells, wood, lignite, and bituminous coal. Different types of activated carbon base materials have varied adsorption characteristics such that some may be better suited to removing certain contaminant compounds than others.  Results from laboratory testing, pilot evaluations, and full-scale system operations suggest that bituminous coal-based GAC is generally the best performing carbon for PFAS removal<ref name="McNamara2018">McNamara, J.D., Franco, R., Mimna, R., and Zappa, L., 2018. Comparison of Activated Carbons for Removal of Perfluorinated Compounds from Drinking Water. Journal‐American Water Works Association, 110(1), pp. E2-E14.  [https://doi.org/10.5942/jawwa.2018.110.0003 DOI: 10.5942/jawwa.2018.110.0003]</ref><ref name="Westreich2018">Westreich, P., Mimna, R., Brewer, J., and Forrester, F., 2018. The removal of short‐chain and long‐chain perfluoroalkyl acids and sulfonates via granular activated carbons: A comparative column study. Remediation Journal, 29(1), pp. 19-26.  [https://doi.org/10.1002/rem.21579 DOI: 10.1002/rem.21579]</ref>.
 
  
−
The removal efficiency of individual PFAS compounds using GAC is a function of both the PFAS functional group (carboxylic acid versus sulfonic acid) and also the perfluoro-carbon chain length<ref name="McCleaf2017">McCleaf, P., Englund, S., Östlund, A., Lindegren, K., Wiberg, K., and Ahrens, L., 2017. Removal efficiency of multiple poly-and perfluoroalkyl substances (PFASs) in drinking water using granular activated carbon (GAC) and anion exchange (AE) column tests. Water Research, 120, pp. 77-87.  [https://doi.org/10.1016/j.watres.2017.04.057 DOI: 10.1016/j.watres.2017.04.057]</ref><ref name="Eschauzier2012">Eschauzier, C., Beerendonk, E., Scholte-Veenendaal, P., and De Voogt, P., 2012. Impact of Treatment Processes on the Removal of Perfluoroalkyl Acids from the Drinking Water Production Chain. Environmental Science and Technology, 46(3), pp. 1708-1715.  [https://doi.org/10.1021/es201662b DOI: 10.1021/es201662b]</ref>(see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature):
+
===Tissues===
−
* perfluoro-sulfonate acids (PFSAs) are more efficiently removed than perfluoro-carboxylic acids (PFCAs) of the same chain length
 
−
* long chain compounds of the same functional group are removed better than the shorter chains
 
−
Activated carbon may be applied in drinking water systems as GAC or PAC<ref name="Dudley">Dudley, L.A., Arevalo, E.C., and Knappe, D.R., 2015. Removal of Perfluoroalkyl Substances by PAC Adsorption and Anion Exchange. Water Research Foundation Project #4344.  Free  download of Executive Summary from: [https://www.waterrf.org/system/files/resource/2019-04/4344_ProjectSummary.pdf Water Research Foundation (Public Plus account)]</ref><ref name="Qian2017">Qian, J., Shen, M., Wang, P., Wang, C., Li, K., Liu, J., Lu, B. and Tian, X., 2017. Perfluorooctane sulfonate adsorption on powder activated carbon: Effect of phosphate (P) competition, pH, and temperature. Chemosphere, 182, pp. 215-222.  [https://doi.org/10.1016/j.chemosphere.2017.05.033 DOI: 10.1016/j.chemosphere.2017.05.033]</ref>. GAC has larger granules and is reusable, while PAC has much smaller granules and is not typically reused.  PAC has most often been used as a temporary treatment because costs associated with disposal and replacement of the used PAC tend to preclude using it for long-term treatment. A typical GAC installation for a private drinking water well is shown in Figure 2. Contrary to PAC, GAC used to treat PFAS can be reactivated by the manufacturer, driving the PFAS from the GAC and into off-gas. The extracted gas is then treated with thermal oxidation (temperatures often 1200&deg;C to 1400&deg;C).  The reactivated GAC is then brought back to the site and reused.  Thus, GAC can ultimately be a destructive treatment technology.
 
  
−
[[File: IXcycle.png | thumb | 400px | left | Figure 3. Operational cycle of a packed bed reactor with anion exchange resin beads]]
+
Tissue matrices are extracted by 18-hour sonication using a ratio of 1 gram of wet tissue per 5 mL of MeOH. This extraction is performed in a sonication bath chilled below 20 ⁰C and the supernatant (MeOH) is filtered through a 0.45 μm PTFE disk filter.  
  
−
===Anion Exchange===
+
Due to the complexity of tissue matrices, an additional tissue cleanup step, adapted from prior research, can be used to reduce interferences<ref name="RussellEtAl2014">Russell, A.L., Seiter, J.M., Coleman, J.G., Winstead, B., Bednar, A.J., 2014. Analysis of munitions constituents in IMX formulations by HPLC and HPLC-MS. Talanta, 128, pp. 524–530. [https://doi.org/10.1016/j.talanta.2014.02.013 doi: 10.1016/j.talanta.2014.02.013]</ref><ref name="CrouchEtAl2020"/>. The cleanup procedure uses small scale chromatography columns prepared by loading 5 ¾” borosilicate pipettes with 0.2 g activated silica gel (100–200 mesh). The columns are wetted with 1 mL MeOH, which is allowed to fully elute and then discarded prior to loading with 1 mL of extract and collecting in a new amber vial. After the extract is loaded, a 1 mL aliquot of MeOH followed by a 1 mL aliquot of 2% HCL/MeOH is added. This results in a 3 mL silica treated tissue extract. This extract is vortexed and diluted to a final solvent ratio of 1:1 MeOH/H<sub><small>2</small></sub>O before analysis.
−
Anion exchange has also been demonstrated for the adsorption of PFAS, and published results note higher sorption per pound than GAC<ref name="McCleaf2017"/><ref name=" Senevirathna2010">Senevirathna, S.T.M.L.D., Tanaka, S., Fujii, S., Kunacheva, C., Harada, H., Shivakoti, B.R., and Okamoto, R., 2010. A comparative study of adsorption of perfluorooctane sulfonate (PFOS) onto granular activated carbon, ion-exchange polymers and non-ion-exchange polymers. Chemosphere, 80(6), pp. 647-651. [https://doi.org/10.1016/j.chemosphere.2010.04.053 DOI: 10.1016/j.chemosphere.2010.04.053]&nbsp;&nbsp; Free download from: [https://www.researchgate.net/profile/Chinagarn_Kunacheva/publication/44672056_A_comparative_study_of_adsorption_of_perfluorooctane_sulfonate_PFOS_onto_granular_activated_carbon_ion-exchange_polymers_and_non-ion-exchange_polymers/links/5a3380510f7e9b2a288a2b21/A-comparative-study-of-adsorption-of-perfluorooctane-sulfonate-PFOS-onto-granular-activated-carbon-ion-exchange-polymers-and-non-ion-exchange-polymers.pdf ResearchGate]</ref><ref name="Woodard2017">Woodard, S., Berry, J., and Newman, B., 2017. Ion exchange resin for PFAS removal and pilot test comparison to GAC. Remediation Journal, 27(3), pp. 19-27.  [https://doi.org/10.1002/rem.21515 DOI: 10.1002/rem.21515]</ref>. The higher capacity is believed to be due to combined hydrophobic and ion exchange adsorption mechanisms, whereas GAC mainly relies on hydrophobic attraction. Anion exchange resins can be highly selective, or they can also remove other contaminants based on design requirements and water chemistry. Resins have greater affinity for PFAS subgroup PFSA than for PFCA, and affinity increases with carbon chain length.
 
−
[[Wikipedia: Ion-exchange resin | Anion exchange resins]] are a viable alternative to GAC for ''ex situ'' treatment of PFAS anions, and several venders sell resins capable of removing PFAS. Resins available for treating PFAS include regenerable resins that can be used multiple times (Figure 3) and single-use resins that must be disposed or destroyed after use<ref name=" Senevirathna2010"/>. Regenerable resins generate a solvent and brine solution, which is distilled to recover the solvent prior to the brine being adsorbed onto a small quantity of GAC or resin for ultimate disposal. This use of one treatment technology (GAC, IX) to support another (RO) is sometimes referred to as a “treatment train” approach. Single-use resins can be more fully exhausted than regenerable resins can and may be a more cost-effective solution for low concentration PFAS contamination, while regenerable resins may be more cost effective for higher concentration contamination.
 
  
−
==Developing PFAS Treatment Technologies==  
+
==HPLC-UV and HPLC-MS Methods==
−
{| class="wikitable" style="float:right; margin-left:10px;"
+
{| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;"
−
|+ Table 1. Developmental Technologies
+
|+Table 3. Secondary HPLC-UV mobile phase gradient method concentrations
 +
|-
 +
| colspan="5" style="background-color:white;" | Method run time = 43 minutes; Column temperature = 25&deg;C<br>Injection volume = 50 &mu;L; Flow rate = 0.8 mL/min<br>Detector wavelengths = 210, 254, and 310 nm
 +
|-
 +
! Time<br>(min)
 +
! Reagent Water<br>(%)
 +
! MeOH<br>(%)
 +
! 0.1% TFA/Water<br>(%)
 +
! ACN<br>(%)
 +
|-
 +
| 0.00 || 75 || 10 || 10 || 5
 +
|-
 +
| 2.50 || 75 || 10 || 10 || 5
 +
|-
 +
| 2.60 || 39 || 46 ||10 || 5
 +
|-
 +
| 9.00 || 39 || 46 ||10 || 5
 +
|-
 +
| 9.10 || 33.5 || 51.5 || 10 || 5
 +
|-
 +
| 15.00 || 35 || 50 || 10 || 5
 +
|-
 +
| 15.10 || 43 || 42 || 10 || 5
 +
|-
 +
| 33.00 || 30 || 55 || 10 || 5
 +
|-
 +
| 33.10 || 75 || 10 || 10 || 5
 +
|-
 +
| 43.00 || 75 || 10 || 10 || 5
 +
|}
 +
{| class="wikitable mw-collapsible" style="float:right; margin-left:20px; text-align:center;"
 +
|+Table 4. Ionization source and detector parameters
 +
|-
 +
! Parameter
 +
! Value
 +
|-
 +
| Ionization Source || APCI
 
|-
 
|-
−
! Stage
+
| Ionization Mode || Negative
−
! Separation/Transfer
 
−
! Destructive*
 
 
|-
 
|-
−
| Developing
+
| Drying Gas Temperature (&deg;C) || 350
−
|
 
−
* Biochar<ref name="Guo2017">Guo, W., Huo, S., Feng, J., and Lu, X., 2017. Adsorption of perfluorooctane sulfonate (PFOS) on corn straw-derived biochar prepared at different pyrolytic temperatures. Journal of the Taiwan Institute of Chemical Engineers, 78, pp. 265-271.  [https://doi.org/10.1016/j.jtice.2017.06.013 DOI: 10.1016/j.jtice.2017.06.013]</ref><ref name="Kupryianchyk2016">Kupryianchyk, D., Hale, S.E., Breedveld, G.D., and Cornelissen, G., 2016. Treatment of sites contaminated with perfluorinated compounds using biochar amendment. Chemosphere, 142, pp. 35-40.  [https://doi.org/10.1016/j.chemosphere.2015.04.085 DOI: 10.1016/j.chemosphere.2015.04.085]&nbsp;&nbsp; Free download from: [https://www.researchgate.net/profile/Sarah_Hale3/publication/276067521_Treatment_of_sites_contaminated_with_perfluorinated_compounds_using_biochar_amendment/links/5cdbe03b299bf14d959895d9/Treatment-of-sites-contaminated-with-perfluorinated-compounds-using-biochar-amendment.pdf ResearchGate]</ref><ref name="Inyang2017">Inyang, M., and Dickenson, E.R., 2017. The use of carbon adsorbents for the removal of perfluoroalkyl acids from potable reuse systems. Chemosphere, 184, pp. 168-175.  [https://doi.org/10.1016/j.chemosphere.2017.05.161 DOI: 10.1016/j.chemosphere.2017.05.161]</ref>
 
−
* Modified Zeolites<ref name="Espana2015">Espana, V.A.A., Mallavarapu, M., and Naidu, R., 2015. Treatment technologies for aqueous perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA): A critical review with an emphasis on field testing. Environmental Technology and Innovation, 4, pp. 168-181.  [https://doi.org/10.1016/j.eti.2015.06.001 DOI: 10.1016/j.eti.2015.06.001]&nbsp;&nbsp; Free download from: [https://www.researchgate.net/profile/Ravi_Naidu2/publication/341241612_Recent_advances_in_the_analysis_of_per-and_polyfluoroalkyl_substances_PFAS-A_review/links/5eb9e3d892851cd50dab441c/Recent-advances-in-the-analysis-of-per-and-polyfluoroalkyl-substances-PFAS-A-review.pdf ResearchGate]</ref><ref name="CETCO2019">CETCO, 2019. FLUORO-SORB&reg; Adsorbent (product sales brochure).  [https://www.mineralstech.com/docs/default-source/performance-materials-documents/cetco/environmental-products/brochures/ps_fluorosorb_am_en_201905_v1.pdf Free download]&nbsp;&nbsp; [[Media:  FluoroSorb2019.pdf | Fluoro-Sorb.pdf]]</ref>
 
−
* Specialty adsorbents<ref name="Zhang2011">Zhang, Q., Deng, S., Yu, G., and Huang, J., 2011. Removal of perfluorooctane sulfonate from aqueous solution by crosslinked chitosan beads: sorption kinetics and uptake mechanism. Bioresource Technology, 102(3), pp. 2265-2271.  [https://doi.org/10.1016/j.biortech.2010.10.040 DOI: 10.1016/j.biortech.2010.10.040]</ref><ref name="Cao2016">Cao, F., Wang, L., Ren, X., and Sun, H., 2016. Synthesis of a perfluorooctanoic acid molecularly imprinted polymer for the selective removal of perfluorooctanoic acid in an aqueous environment. Journal of Applied Polymer Science, 133(15).  [https://doi.org/10.1002/app.43192 DOI: 10.1002/app.43192]</ref><ref name="Hu2016">Hu, L., Li, Y., and Zhang, W., 2016. Characterization and application of surface-molecular-imprinted-polymer modified TiO2 nanotubes for removal of perfluorinated chemicals. Water Science and Technology, 74(6), pp. 1417-1425.  [https://doi.org/10.2166/wst.2016.321 DOI: 10.2166/wst.2016.321]&nbsp;&nbsp; [[Media: Hu2016.pdf | Free access article.]]</ref>
 
−
|
 
−
* Electro-oxidation<ref name="Zhang2016">Zhang, C., Tang, J., Peng, C., and Jin, M., 2016. Degradation of perfluorinated compounds in wastewater treatment plant effluents by electrochemical oxidation with Nano-ZnO coated electrodes. Journal of Molecular Liquids, 221, pp. 1145-1150.  [https://doi.org/10.1016/j.molliq.2016.06.093 DOI: 10.1016/j.molliq.2016.06.093]</ref><ref name="Urtiaga2015">Urtiaga, A., Fernández-González, C., Gómez-Lavín, S., and Ortiz, I., 2015. Kinetics of the electrochemical mineralization of perfluorooctanoic acid on ultrananocrystalline boron doped conductive diamond electrodes. Chemosphere, 129, pp. 20-26.  [https://doi.org/10.1016/j.chemosphere.2014.05.090 DOI: 10.1016/j.chemosphere.2014.05.090]&nbsp;&nbsp; Free download from: [https://d1wqtxts1xzle7.cloudfront.net/39233145/00b7d53b67db54fca5000000.pdf?1445006282=&response-content-disposition=inline%3B+filename%3DKinetics_of_the_electrochemical_minerali.pdf&Expires=1613074964&Signature=Bfvds3n9udSs5F9J00Embf8MRJxumQVJoaj5jEni5mqPnmo2QFGGN3fUvWISkRD1yKfoIhNEDQ0a-ISxfZ9vW9jBTkTjN7ud7aSC3rBelIFdtFasfpEXgPvnqsLfKRTWI5S~QRsHbvK5XbwnKo2VyFAmUcuJUjVFP1PK1kEY9-gB2d-8FwSJWbCAAd83fNWm3zHzbOvdchJ~fjAqlydgq7Pu~AwEeH4Zl1LhcYxajzcenTSiBWmMStfOUpTyETSCpSwF7XKuhKMYGePsit8fAWpxH4dleYWmvOi9Gc9YyTB32qBziOTfeqjhTsA-uqECz9bxyD65voHUW7sEchkrKw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA Academia.edu]</ref><ref name="Schaefer2018">Schaefer, C.E., Choyke, S., Ferguson, P.L., Andaya, C., Burant, A., Maizel, A., Strathmann, T.J. and Higgins, C.P., 2018. Electrochemical Transformations of Perfluoroalkyl Acid (PFAA) Precursors and PFAAs in Groundwater Impacted with Aqueous Film Forming Foams. Environmental Science and Technology, 52(18), pp. 10689-10697.  [https://doi.org/10.1021/acs.est.8b02726 DOI: 10.1021/acs.est.8b02726]</ref>
 
−
* Heat activated persulfate<ref name="Park2016">Park, S., Lee, L.S., Medina, V. F., Zull, A., and Waisner, S., 2016. Heat-activated persulfate oxidation of PFOA, 6: 2 fluorotelomer sulfonate, and PFOS under conditions suitable for in-situ groundwater remediation. Chemosphere, 145, pp. 376-383.  [https://doi.org/10.1016/j.chemosphere.2015.11.097 DOI: 10.1016/j.chemosphere.2015.11.097]</ref>
 
−
* Alkaline perozone<ref name="Lin2012">Lin, A.Y.C., Panchangam, S.C., Chang, C.Y., Hong, P.A., and Hsueh, H.F., 2012. Removal of perfluorooctanoic acid and perfluorooctane sulfonate via ozonation under alkaline condition. Journal of Hazardous Materials, 243, pp. 272-277.  [https://doi.org/10.1016/j.jhazmat.2012.10.029 DOI: 10.1016/j.jhazmat.2012.10.029]</ref>
 
−
* Sonolysis<ref name="Campbell2015">Campbell, T., Hoffmann, M.R., 2015. Sonochemical degradation of perfluorinated surfactants: Power and multiple frequency effects. Separation and Purification Technology, 156(3), pp. 1019-1027.  [https://doi.org/10.1016/j.seppur.2015.09.053 DOI: 10.1016/j.seppur.2015.09.053]&nbsp;&nbsp; Free download from: [https://www.researchgate.net/profile/Tammy_Campbell5/publication/282583363_Sonochemical_Degradation_of_Perfluorinated_Surfactants_Power_and_Multiple_Frequency_Effects/links/5bfc40bd92851cbcdd74449b/Sonochemical-Degradation-of-Perfluorinated-Surfactants-Power-and-Multiple-Frequency-Effects.pdf ResearchGate]</ref><ref name="Cheng2010">Cheng, J., Vecitis, C.D., Park, H., Mader, B.T., Hoffmann, M.R., 2010. Sonochemical Degradation of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoate (PFOA) in Groundwater: Kinetic Effects of Matrix Inorganics. Environmental Science and Technology, 44(1), pp. 445-450.  [https://doi.org/10.1021/es902651g DOI: 10.1021/es902651g]</ref><ref name="Gole2018a">Gole, V.L., Sierra-Alvarez, R., Peng, H., Giesy, J.P., Deymier, P., Keswani, M., 2018. Sono-chemical treatment of per- and poly-fluoroalkyl compounds in aqueous film-forming foams by use of a large-scale multi-transducer dual-frequency based acoustic reactor. Ultrasonics Sonochemistry, 45, pp. 213-222.  [https://doi.org/10.1016/j.ultsonch.2018.02.014 DOI: 10.1016/j.ultsonch.2018.02.014]&nbsp;&nbsp; [https://www.sciencedirect.com/science/article/pii/S1350417718301937 Open access article.]&nbsp;&nbsp; [[Media: Gole2018a.pdf | Report.pdf]]</ref><ref name="Gole2018b">Gole, V.L., Fishgold, A., Sierra-Alvarez, R., Deymier, P., Keswani, M., 2018. Treatment of perfluorooctane sulfonic acid (PFOS) using a large-scale sonochemical reactor. Separation and Purification Technology, 194, pp. 104-110.  [https://doi.org/10.1016/j.seppur.2017.11.009 DOI: 10.1016/j.seppur.2017.11.009]</ref>
 
−
* Super Critical Water Oxidation
 
 
|-
 
|-
−
| Maturing and</br>Demonstrated
+
| Vaporizer Temperature (&deg;C) || 325
−
|
 
−
* Chemical coagulation<ref name="Cornelsen2015">Cornelsen Ltd., 2015. PerfluorAd, PFC Water Treatment Solution (product sales site). [http://www.cornelsen.co.uk/perfluorad-pfc-treatment/ Website]</ref>
 
−
* Electrocoagulation<ref name="Wang2016">Wang, Y., Lin, H., Jin, F., Niu, J., Zhao, J., Bi, Y., and Li, Y., 2016. Electrocoagulation mechanism of perfluorooctanoate (PFOA) on a zinc anode: Influence of cathodes and anions. Science of the Total Environment, 557, pp. 542-550.  [https://doi.org/10.1016/j.scitotenv.2016.03.114 DOI: 10.1016/j.scitotenv.2016.03.114]</ref>
 
−
* Foam fractionation<ref name="Horst2018">Horst, J., McDonough, J., Ross, I., Dickson, M., Miles, J., Hurst, J., and Storch, P., 2018. Water Treatment Technologies for PFAS: The Next Generation. Groundwater Monitoring and Remediation, 38(2), pp. 13-23.  [https://doi.org/10.1111/gwmr.12281 DOI: 10.1111/gwmr.12281]</ref><ref name="EPC2017">EPC Media Group Pty Ltd., 2017. OPEC systems delivers PFAS contamination breakthrough. Waste + Water Management Australia, 44(3), 26-27.  [https://search.informit.org/doi/10.3316/informit.253699294687114 DOI: 10.3316/informit.253699294687114]  ISSN: 1838-7098</ref>
 
−
|
 
−
* Low temperature plasma<ref name="Stratton2017">Stratton, G.R., Dai, F., Bellona, C.L., Holsen, T.M., Dickenson, E.R., and Mededovic Thagard, S., 2017. Plasma-Based Water Treatment: Efficient Transformation of Perfluoroalkyl Substances in Prepared Solutions and Contaminated Groundwater. Environmental Science and Technology, 51(3), pp. 1643-1648.  [https://doi.org/10.1021/acs.est.6b04215 DOI: 10.1021/acs.est.6b04215]</ref><ref name="Singh2019">Singh, R.K., Multari, N., Nau-Hix, C., Anderson, R.H., Richardson, S.D., Holsen, T.M. and Mededovic Thagard, S., 2019. Rapid Removal of Poly- and Perfluorinated Compounds from Investigation-Derived Waste (IDW) in a Pilot-Scale Plasma Reactor. Environmental Science and Technology, 53(19), pp. 11375-11382.  [https://doi.org/10.1021/acs.est.9b02964 DOI: 10.1021/acs.est.9b02964]</ref>
 
 
|-
 
|-
−
| colspan="3" style="background:white;" | * There are several other destructive technologies such as alternative oxidants, and activation</br>methods of oxidants, but for the purpose of this article, the main categories are presented here.
+
| Drying Gas Flow (L/min) || 4.0
 +
|-
 +
| Nebulizer Pressure (psig) || 40
 +
|-
 +
| Corona Current (&mu;A) || 10
 +
|-
 +
| Capillary Potential (V) || 1500
 +
|-
 +
| Mass Range || 40 – 400
 +
|-
 +
| Fragmentor || 100
 +
|-
 +
| Gain || 1
 +
|-
 +
| Threshold || 0
 +
|-
 +
| Step Size || 0.20
 +
|-
 +
| Speed (&mu;/sec) || 743
 +
|-
 +
| Peak Width (min) || 0.06
 +
|-
 +
| Cycle Time (sec/cycle) || 0.57
 
|}
 
|}
−
Numerous&nbsp;separation&nbsp;and destructive technologies are in the developmental stages of bench-scale testing or limited field-scale demonstrations.  Some of these are listed in Table&nbsp;1:
 
  
−
==Conclusions==
+
The Primary HPLC-UV method uses a Phenomenex Synergi 4 µm Hydro-RP column (80Å, 250 x 4.6 mm), or comparable, and is based on both the HPLC method found in USEPA 8330B and previous work<ref name= "8330B"/><ref name="RussellEtAl2014"/><ref name="CrouchEtAl2020"/>. This separation relies on a reverse phase column and uses a gradient elution, shown in Table 2. Depending on the analyst’s needs and equipment availability, the method has been proven to work with either 0.1% TFA or 0.25% FA (vol/vol) mobile phase. Addition of a guard column like a Phenomenex SecurityGuard AQ C18 pre-column guard cartridge can be optionally used. These optional changes to the method have no impact on the method’s performance.
−
The well established processes for removing PFAS from water all produce residuals that require management, and it is likely that newer processes under development will also produce some residuals. Often, it is the residuals that limit the usefulness of the process. For instance, RO and NF may currently provide the most complete treatment of water, but the production of a relatively high volume of PFAS-containing liquid reject (the portion of the liquid that retains the contaminants and is “rejected” from the process) limits their application.  Often, a second treatment technology such as an adsorbent is required to support the main technology by concentrating or treating the residuals. 
+
 
−
As more testing and operational data on adsorbents are generated, it is becoming evident that no adsorbent technology outperforms the others in all cases.  Whether GAC, ion exchange or another technology is the most technically efficient and cost effective long term option for a given site depends on influent water geochemistry and contaminant concentrations, treatment standards, co-contaminants, duration of treatment, and required flow rates. New generation adsorbents are rapidly being introduced into the market at “evaluation scale” which may provide advantages over commercially available adsorbents.
+
The Secondary HPLC-UV method uses a Restek Pinnacle II Biphenyl 5 µm (150 x 4.6 mm) or comparable column and is intended as a confirmatory method. Like the Primary method, this method can use an optional guard column and utilizes a gradient elution, shown in Table 3.
−
Several newer technologies are being evaluated in the lab and in the field which include electro-oxidation, heat-activated persulfate, sonolysis, electrocoagulation, low temperature plasma, super critical water oxidation, and foam fractionation. These and other potential treatments for PFAS are still largely in the developmental stage. Several technologies show promise for improved management of PFAS sites. However, it is unlikely that a single technology will be adequate for full remediation at many sites. A multi-technology treatment train approach may be necessary for effective treatment of this complicated group of compounds.
+
   
 +
For instruments equipped with a mass spectrometer (MS), a secondary MS method is available and was developed alongside the Primary UV method. The method was designed for use with a single quadrupole MS equipped with an atmospheric pressure chemical ionization (APCI) source, such as an Agilent 6120B. A majority of the analytes shown in Table 1 are amenable to this MS method, however nitroglycerine (which is covered extensively in USEPA method 8332) and 2-,3-, and 4-nitrotoluene compounds aren’t compatible with the MS method. MS method parameters are shown in Table 4.
  
−
<br clear="left" />
+
==Summary==
 +
The extraction methods and instrumental methods in this article build upon prior munitions analytical methods by adding new compounds, combining legacy and insensitive munitions analysis, and expanding usable sample matrices. These methods have been verified through extensive round robin testing and validation, and while the methods are somewhat challenging, they are crucial when simultaneous analysis of both insensitive and legacy munitions is needed.
  
 
==References==
 
==References==
−
 
 
<references />
 
<references />
  
 
==See Also==
 
==See Also==
 +
*[[Media: ERDC_TR-21-12.pdf | Preparative, Extraction, and Analytical Methods for Simultaneous Determination of Legacy and Insensitive Munition (IM) Constituents in Aqueous, Soil or Sediment, and Tissue Matrices]]
 +
*[https://serdp-estcp.mil/focusareas/9f7a342a-1b13-4ce5-bda0-d7693cf2b82d/uxo#subtopics  SERDP/ESTCP Focus Areas – UXO – Munitions Constituents]
 +
*[https://denix.osd.mil/edqw/home/  Environmental Data Quality Workgroup]

Latest revision as of 21:59, 26 September 2024

Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)

Sediment porewater dialysis passive samplers, also known as “peepers,” are sampling devices that allow the measurement of dissolved inorganic ions in the porewater of a saturated sediment. Peepers function by allowing freely-dissolved ions in sediment porewater to diffuse across a micro-porous membrane towards water contained in an isolated compartment that has been inserted into sediment. Once retrieved after a deployment period, the resulting sample obtained can provide concentrations of freely-dissolved inorganic constituents in sediment, which provides measurements that can be used for understanding contaminant fate and risk. Peepers can also be used in the same manner in surface water, although this article is focused on the use of peepers in sediment.

Related Article(s):


Contributor(s):

  • Florent Risacher, M.Sc.
  • Jason Conder, Ph.D.

Key Resource(s):

  • A review of peeper passive sampling approaches to measure the availability of inorganics in sediment porewater[1]
  • Best Practices User’s Guide: Standardizing Sediment Porewater Passive Samplers for Inorganic Constituents of Concern[2]

Introduction

Biologically available inorganic constituents associated with sediment toxicity can be quantified by measuring the freely-dissolved fraction of contaminants in the porewater[3][4]. Classical sediment porewater analysis usually consists of collecting large volumes of bulk sediments which are then mechanically squeezed or centrifuged to produce a supernatant, or suction of porewater from intact sediment, followed by filtration and collection[5]. The extraction and measurement processes present challenges due to the heterogeneity of sediments, physical disturbance, high reactivity of some complexes, and interaction between the solid and dissolved phases, which can impact the measured concentration of dissolved inorganics[6]. For example, sampling disturbance can affect redox conditions[7][8], which can lead to under or over representation of inorganic chemical concentrations relative to the true dissolved phase concentration in the sediment porewater[9][5].

To address the complications with mechanical porewater sampling, passive sampling approaches for inorganics have been developed to provide a method that has a low impact on the surrounding geochemistry of sediments and sediment porewater, thus enabling more precise measurements of inorganics[4]. Sediment porewater dialysis passive samplers, also known as “peepers,” were developed more than 45 years ago[10] and refinements to the method such as the use of reverse tracers have been made, improving the acceptance of the technology as decision-making tool.

Peeper Designs

Peepers (Figure 1) are inert containers with a small volume (typically 1-100 mL) of purified water (“peeper water”) capped with a semi-permeable membrane. Peepers can be manufactured in a wide variety of formats (Figure 2, Figure 3) and deployed in in various ways.

Two designs are commonly used for peepers. Frequently, the designs are close adaptations of the original multi-chamber Hesslein design[10] (Figure 2), which consists of an acrylic sampler body with multiple sample chambers machined into it. Peeper water inside the chambers is separated from the outside environment by a semi-permeable membrane, which is held in place by a top plate fixed to the sampler body using bolts or screws. An alternative design consists of single-chamber peepers constructed using a single sample vial with a membrane secured over the mouth of the vial, as shown in Figure 3, and applied in Teasdale et al.[7], Serbst et al.[11], Thomas and Arthur[12], Passeport et al.[13], and Risacher et al.[2]. The vial is filled with deionized water, and the membrane is held in place using the vial cap or an o-ring. Individual vials are either directly inserted into sediment or are incorporated into a support structure to allow multiple single-chamber peepers to be deployed at once over a given depth profile (Figure 3).


Table 1. Analyte list with acronyms and CAS numbers.
Compound Acronym CAS Number
1,2-Dinitrobenzene (surrogate) 1,2-DNB (surr.) 528-29-0
1,3-Dinitrobenzene 1,3-DNB 99-65-0
1,3,5-Trinitrobenzene 1,3,5-TNB 99-35-4
1,4-Dinitrobenzene 1,4-DNB (surr.) 100-25-4
2-Amino-4,6-dinitrotoluene 2-Am-4,6-DNT 35572-78-2
2-Nitrophenol 2-NP 88-75-5
2-Nitrotoluene 2-NT 88-72-2
2,4-Dinitrophenol 2,4-DNP 51-28-5
2,4-Dinitrotoluene 2,4-DNT 121-14-2
2,4,6-Trinitrophenol Picric Acid (PA) 88-89-1
2,4,6-Trinitrotoluene 2,4,6-TNT 118-96-7
2,6-Dinitrotoluene 2,6-DNT 606-20-2
3-Nitrotoluene 3-NT 99-08-1
3,5-Dinitroaniline 3,5-DNA 618-87-1
4-Amino-2,6-dinitrotoluene 4-Am-2,6-DNT 19406-51-0
4-Nitrophenol 4-NP 100-02-7
4-Nitrotoluene 4-NT 99-99-0
2,4-Dinitroanisole DNAN 119-27-7
Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine HMX 2691-41-0
Nitrobenzene NB 98-95-3
Nitroglycerine NG 55-63-0
Nitroguanidine NQ 556-88-7
3-Nitro-1,2,4-triazol-5-one NTO 932-64-9
ortho-Nitrobenzoic acid o-NBA (surr.) 552-16-9
Pentaerythritol tetranitrate PETN 78-11-5
Hexahydro-1,3,5-trinitro-1,3,5-triazine RDX 121-82-4
N-Methyl-N-(2,4,6-trinitrophenyl)nitramide Tetryl 479-45-8
Note: Analytes in bold are not identified by EPA Method 8330B.
Figure 1. Primary Method labeled chromatograms
Figure 2. Secondary Method labeled chromatograms

The primary intention of the analytical methods presented here is to support the monitoring of legacy and insensitive munitions contamination on test and training ranges, however legacy and insensitive munitions often accompany each other at demilitarization facilities, manufacturing facilities, and other environmental sites. Energetic materials typically appear on ranges as small, solid particulates and due to their varying functional groups and polarities, can partition in various environmental compartments[14]. To ensure that contaminants are monitored and controlled at these sites and to sustainably manage them a variety of sample matrices (surface or groundwater, process waters, soil, and tissues) must be considered. (Process water refers to water used during industrial manufacturing or processing of legacy and insensitive munitions.) Furthermore, additional analytes must be added to existing methodologies as the usage of IM compounds changes and as new degradation compounds are identified. Of note, relatively new IM formulations containing NTO, DNAN, and NQ are seeing use in IMX-101, IMX-104, Pax-21 and Pax-41 (Table 1)[15][16].

Sampling procedures for legacy and insensitive munitions are identical and utilize multi-increment sampling procedures found in USEPA Method 8330B Appendix A[17]. Sample hold times, subsampling and quality control requirements are also unchanged. The key differences lie in the extraction methods and instrumental methods. Briefly, legacy munitions analysis of low concentration waters uses a single cartridge reverse phase SPE procedure, and acetonitrile (ACN) is used for both extraction and elution for aqueous and solid samples[17][18]. An isocratic separation via reversed-phase C-18 column with 50:50 methanol:water mobile phase or a C-8 column with 15:85 isopropanol:water mobile phase is used to separate legacy munitions[17]. While these procedures are sufficient for analysis of legacy munitions, alternative solvents, additional SPE cartridges, and a gradient elution are all required for the combined analysis of legacy and insensitive munitions.

Previously, analysis of legacy and insensitive munitions required multiple analytical techniques, however the methods presented here combine the two munitions categories resulting in an HPLC-UV method and accompanying extraction methods for a variety of common sample matrices. A secondary HPLC-UV method and a HPLC-MS method were also developed as confirmatory methods. The methods discussed in this article were validated extensively by single-blind round robin testing and subsequent statistical treatment as part of ESTCP ER19-5078. Wherever possible, the quality control criteria in the Department of Defense Quality Systems Manual for Environmental Laboratories were adhered to[19]. Analytes included in the methods presented here are found in Table 1.

The chromatograms produced by the primary and secondary HPLC-UV methods are shown in Figure 1 and Figure 2, respectively. Chromatograms for each detector wavelength used are shown (315, 254, and 210 nm).

Extraction Methods

Figure 3. Triple cartridge SPE setup
Figure 4. A flow chart of the soil extraction procedure

High Concentration Waters (> 1 ppm)

Aqueous samples suspected to contain the compounds of interest at concentrations detectable without any extraction or pre-concentration are suitable for analysis by direct injection. The method deviates from USEPA Method 8330B by adding a pH adjustment and use of MeOH rather than ACN for dilution[17]. The pH adjustment is needed to ensure method accuracy for ionic compounds (like NTO or PA) in basic samples. A solution of 1% HCl/MeOH is added to both acidify and dilute the samples to a final acid concentration of 0.5% (vol/vol) and a final solvent ratio of 1:1 MeOH/H2O. The direct injection samples are then ready for analysis.

Low Concentration Waters (< 1 ppm)

Aqueous samples suspected to contain the compounds of interest at low concentrations require extraction and pre-concentration using solid phase extraction (SPE). The SPE setup described here uses a triple cartridge setup shown in Figure 3. Briefly, the extraction procedure loads analytes of interest onto the cartridges in this order: StrataTM X, StrataTM X-A, and Envi-CarbTM. Then the cartridge order is reversed, and analytes are eluted via a two-step elution, resulting in 2 extracts (which are combined prior to analysis). Five milliliters of MeOH is used for the first elution, while 5 mL of acidified MeOH (2% HCl) is used for the second elution. The particular SPE cartridges used are noncritical so long as cartridge chemistries are comparable to those above.

Table 2. Primary HPLC-UV mobile phase gradient method concentrations
Method run time = 48 minutes; Column temperature = 25°C
Injection volume = 50 μL; Flow rate = 1.0 mL/min
Detector wavelengths = 210, 254, and 310 nm
Time
(min) 		Reagent Water
(%) 		MeOH
(%) 		0.1% TFA/Water
(%) 		ACN
(%)
0.00 89 3 3 5
2.00 89 3 3 5
2.20 52 40 3 5
12.5 52 40 3 5
19.0 57 35 3 5
28.0 48 44 3 5
32.0 48 44 3 5
44.0 32 60 3 5
44.1 89 3 3 5
48.0 89 3 3 5

Soils

Soil collection, storage, drying and grinding procedures are identical to the USEPA Method 8330B procedures[17]; however, the solvent extraction procedure differs in the number of sonication steps, sample mass and solvent used. A flow chart of the soil extraction procedure is shown in Figure 4. Soil masses of approximately 2 g and a sample to solvent ratio of 1:5 (g/mL) are used for soil extraction. The extraction is carried out in a sonication bath chilled below 20 ⁰C and is a two-part extraction, first extracting in MeOH (6 hours) followed by a second sonication in 1:1 MeOH:H2O solution (14 hours). The extracts are centrifuged, and the supernatant is filtered through a 0.45 μm PTFE disk filter.

The solvent volume should generally be 10 mL but if different soil masses are required, solvent volume should be 5 mL/g. The extraction results in 2 separate extracts (MeOH and MeOH:H2O) that are combined prior to analysis.

Tissues

Tissue matrices are extracted by 18-hour sonication using a ratio of 1 gram of wet tissue per 5 mL of MeOH. This extraction is performed in a sonication bath chilled below 20 ⁰C and the supernatant (MeOH) is filtered through a 0.45 μm PTFE disk filter.

Due to the complexity of tissue matrices, an additional tissue cleanup step, adapted from prior research, can be used to reduce interferences[20][21]. The cleanup procedure uses small scale chromatography columns prepared by loading 5 ¾” borosilicate pipettes with 0.2 g activated silica gel (100–200 mesh). The columns are wetted with 1 mL MeOH, which is allowed to fully elute and then discarded prior to loading with 1 mL of extract and collecting in a new amber vial. After the extract is loaded, a 1 mL aliquot of MeOH followed by a 1 mL aliquot of 2% HCL/MeOH is added. This results in a 3 mL silica treated tissue extract. This extract is vortexed and diluted to a final solvent ratio of 1:1 MeOH/H2O before analysis.

HPLC-UV and HPLC-MS Methods

Table 3. Secondary HPLC-UV mobile phase gradient method concentrations
Method run time = 43 minutes; Column temperature = 25°C
Injection volume = 50 μL; Flow rate = 0.8 mL/min
Detector wavelengths = 210, 254, and 310 nm
Time
(min) 		Reagent Water
(%) 		MeOH
(%) 		0.1% TFA/Water
(%) 		ACN
(%)
0.00 75 10 10 5
2.50 75 10 10 5
2.60 39 46 10 5
9.00 39 46 10 5
9.10 33.5 51.5 10 5
15.00 35 50 10 5
15.10 43 42 10 5
33.00 30 55 10 5
33.10 75 10 10 5
43.00 75 10 10 5
Table 4. Ionization source and detector parameters
Parameter Value
Ionization Source APCI
Ionization Mode Negative
Drying Gas Temperature (°C) 350
Vaporizer Temperature (°C) 325
Drying Gas Flow (L/min) 4.0
Nebulizer Pressure (psig) 40
Corona Current (μA) 10
Capillary Potential (V) 1500
Mass Range 40 – 400
Fragmentor 100
Gain 1
Threshold 0
Step Size 0.20
Speed (μ/sec) 743
Peak Width (min) 0.06
Cycle Time (sec/cycle) 0.57

The Primary HPLC-UV method uses a Phenomenex Synergi 4 µm Hydro-RP column (80Å, 250 x 4.6 mm), or comparable, and is based on both the HPLC method found in USEPA 8330B and previous work[17][20][21]. This separation relies on a reverse phase column and uses a gradient elution, shown in Table 2. Depending on the analyst’s needs and equipment availability, the method has been proven to work with either 0.1% TFA or 0.25% FA (vol/vol) mobile phase. Addition of a guard column like a Phenomenex SecurityGuard AQ C18 pre-column guard cartridge can be optionally used. These optional changes to the method have no impact on the method’s performance.

The Secondary HPLC-UV method uses a Restek Pinnacle II Biphenyl 5 µm (150 x 4.6 mm) or comparable column and is intended as a confirmatory method. Like the Primary method, this method can use an optional guard column and utilizes a gradient elution, shown in Table 3.

For instruments equipped with a mass spectrometer (MS), a secondary MS method is available and was developed alongside the Primary UV method. The method was designed for use with a single quadrupole MS equipped with an atmospheric pressure chemical ionization (APCI) source, such as an Agilent 6120B. A majority of the analytes shown in Table 1 are amenable to this MS method, however nitroglycerine (which is covered extensively in USEPA method 8332) and 2-,3-, and 4-nitrotoluene compounds aren’t compatible with the MS method. MS method parameters are shown in Table 4.

Summary

The extraction methods and instrumental methods in this article build upon prior munitions analytical methods by adding new compounds, combining legacy and insensitive munitions analysis, and expanding usable sample matrices. These methods have been verified through extensive round robin testing and validation, and while the methods are somewhat challenging, they are crucial when simultaneous analysis of both insensitive and legacy munitions is needed.

References

  1. ^ Risacher, F.F., Schneider, H., Drygiannaki, I., Conder, J., Pautler, B.G., and Jackson, A.W., 2023. A Review of Peeper Passive Sampling Approaches to Measure the Availability of Inorganics in Sediment Porewater. Environmental Pollution, 328, Article 121581. doi: 10.1016/j.envpol.2023.121581   Open Access Manuscript
  2. ^ 2.0 2.1 Risacher, F.F., Nichols, E., Schneider, H., Lawrence, M., Conder, J., Sweett, A., Pautler, B.G., Jackson, W.A., Rosen, G., 2023b. Best Practices User’s Guide: Standardizing Sediment Porewater Passive Samplers for Inorganic Constituents of Concern, ESTCP ER20-5261. Project Website   Report.pdf
  3. ^ Conder, J.M., Fuchsman, P.C., Grover, M.M., Magar, V.S., Henning, M.H., 2015. Critical review of mercury SQVs for the protection of benthic invertebrates. Environmental Toxicology and Chemistry, 34(1), pp. 6-21. doi: 10.1002/etc.2769   Open Access Article
  4. ^ 4.0 4.1 Cleveland, D., Brumbaugh, W.G., MacDonald, D.D., 2017. A comparison of four porewater sampling methods for metal mixtures and dissolved organic carbon and the implications for sediment toxicity evaluations. Environmental Toxicology and Chemistry, 36(11), pp. 2906-2915. doi: 10.1002/etc.3884
  5. ^ 5.0 5.1 Gruzalski, J.G., Markwiese, J.T., Carriker, N.E., Rogers, W.J., Vitale, R.J., Thal, D.I., 2016. Pore Water Collection, Analysis and Evolution: The Need for Standardization. In: Reviews of Environmental Contamination and Toxicology, Vol. 237, pp. 37–51. Springer. doi: 10.1007/978-3-319-23573-8_2
  6. ^ Peijnenburg, W.J.G.M., Teasdale, P.R., Reible, D., Mondon, J., Bennett, W.W., Campbell, P.G.C., 2014. Passive Sampling Methods for Contaminated Sediments: State of the Science for Metals. Integrated Environmental Assessment and Management, 10(2), pp. 179–196. doi: 10.1002/ieam.1502   Open Access Article
  7. ^ 7.0 7.1 Teasdale, P.R., Batley, G.E., Apte, S.C., Webster, I.T., 1995. Pore water sampling with sediment peepers. Trends in Analytical Chemistry, 14(6), pp. 250–256. doi: 10.1016/0165-9936(95)91617-2
  8. ^ Schroeder, H., Duester, L., Fabricius, A.L., Ecker, D., Breitung, V., Ternes, T.A., 2020. Sediment water (interface) mobility of metal(loid)s and nutrients under undisturbed conditions and during resuspension. Journal of Hazardous Materials, 394, Article 122543. doi: 10.1016/j.jhazmat.2020.122543   Open Access Article
  9. ^ Wise, D.E., 2009. Sampling techniques for sediment pore water in evaluation of reactive capping efficacy. Master of Science Thesis. University of New Hampshire Scholars’ Repository. 178 pages. Website   Report.pdf
  10. ^ 10.0 10.1 Hesslein, R.H., 1976. An in situ sampler for close interval pore water studies. Limnology and Oceanography, 21(6), pp. 912-914. doi: 10.4319/lo.1976.21.6.0912   Open Access Article
  11. ^ Serbst, J.R., Burgess, R.M., Kuhn, A., Edwards, P.A., Cantwell, M.G., Pelletier, M.C., Berry, W.J., 2003. Precision of dialysis (peeper) sampling of cadmium in marine sediment interstitial water. Archives of Environmental Contamination and Toxicology, 45(3), pp. 297–305. doi: 10.1007/s00244-003-0114-5
  12. ^ Thomas, B., Arthur, M.A., 2010. Correcting porewater concentration measurements from peepers: Application of a reverse tracer. Limnology and Oceanography: Methods, 8(8), pp. 403–413. doi: 10.4319/lom.2010.8.403   Open Access Article
  13. ^ Passeport, E., Landis, R., Lacrampe-Couloume, G., Lutz, E.J., Erin Mack, E., West, K., Morgan, S., Lollar, B.S., 2016. Sediment Monitored Natural Recovery Evidenced by Compound Specific Isotope Analysis and High-Resolution Pore Water Sampling. Environmental Science and Technology, 50(22), pp. 12197–12204. doi: 10.1021/acs.est.6b02961
  14. ^ 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
  15. ^ Mainiero, C. 2015. Picatinny Employees Recognized for Insensitive Munitions. U.S. Army, Picatinny Arsenal Public Affairs. Open Access Press Release
  16. ^ Frem, D., 2022. A Review on IMX-101 and IMX-104 Melt-Cast Explosives: Insensitive Formulations for the Next-Generation Munition Systems. Propellants, Explosives, Pyrotechnics, 48(1), e202100312. doi: 10.1002/prep.202100312
  17. ^ 17.0 17.1 17.2 17.3 17.4 17.5 Cite error: Invalid <ref> tag; no text was provided for refs named 8330B
  18. ^ United States Environmental Protection Agency (USEPA), 2007. EPA Method 3535A (SW-846) Solid-Phase Extraction (SPE), Revision 1. USEPA Website    Method 3535A.pdf
  19. ^ US Department of Defense and US Department of Energy, 2021. Consolidated Quality Systems Manual (QSM) for Environmental Laboratories, Version 5.4. 387 pages. Free Download    QSM Version 5.4.pdf
  20. ^ 20.0 20.1 Russell, A.L., Seiter, J.M., Coleman, J.G., Winstead, B., Bednar, A.J., 2014. Analysis of munitions constituents in IMX formulations by HPLC and HPLC-MS. Talanta, 128, pp. 524–530. doi: 10.1016/j.talanta.2014.02.013
  21. ^ 21.0 21.1 Cite error: Invalid <ref> tag; no text was provided for refs named CrouchEtAl2020

See Also

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