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==PFAS Treatment by Electrical Discharge Plasma==
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==Remediation of Stormwater Runoff Contaminated by Munition Constituents==  
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Plasma-based water treatment is a technology that, using only electricity, converts water into a mixture of highly reactive species including OH•, O, H•, HO<sub>2</sub>•, O<sub>2</sub>•<sup>‒</sup>, H<sub>2</sub>, O<sub>2</sub>, H<sub>2</sub>O<sub>2</sub> and aqueous electrons (e<sup>‒</sup><sub>aq</sub>), called a plasma<ref name="Sunka1999">Sunka, P., Babický, V., Clupek, M., Lukes, P., Simek, M., Schmidt, J., and Cernak, M., 1999. Generation of Chemically Active Species by Electrical Discharges in Water. Plasma Sources Science and Technology, 8(2), pp. 258-265. [https://doi.org/10.1088/0963-0252/8/2/006 DOI: 10.1088/0963-0252/8/2/006]</ref><ref name="MededovicThagard2009">Mededovic Thagard, S., Takashima, K., and Mizuno, A., 2009. Chemistry of the Positive and Negative Electrical Discharges Formed in Liquid Water and Above a Gas-Liquid Surface. Plasma Chemistry and Plasma Processing, 29(6), pp.455-473. [https://doi.org/10.1007/s11090-009-9195-x DOI: 10.1007/s11090-009-9195-x]</ref>. These highly reactive species rapidly and non-selectively degrade [[Wikipedia: Volatile organic compound |volatile organic compounds (VOCs)]]<ref name="Du2019">Du, C., Gong, X., and Lin, Y., 2019. Decomposition of volatile organic compounds using corona discharge plasma technology. Journal of the Air and Waste Management Association, 69(8), pp.879-899.  [https://doi.org/10.1080/10962247.2019.1582441 DOI: 10.1080/10962247.2019.1582441]  [https://www.tandfonline.com/doi/full/10.1080/10962247.2019.1582441 Open access article.]</ref>, [[1,4-Dioxane | 1,4-dioxane]]<ref name="Xiong2019">Xiong, Y., Zhang, Q., Wandell, R., Bresch, S., Wang, H., Locke, B.R. and Tang, Y., 2019. Synergistic 1,4-Dioxane Removal by Non-Thermal Plasma Followed by Biodegradation. Chemical Engineering Journal, 361, pp.519-527. [https://doi.org/10.1016/J.CEJ.2018.12.094 DOI: 10.1016/J.CEJ.2018.12.094]</ref><ref name="Ni2013">Ni, G.H., Zhao, Y., Meng, Y.D., Wang, X.K., and Toyoda, H., 2013. Steam plasma jet for treatment of contaminated water with high-concentration 1,4-dioxane organic pollutants. Europhysics Letters, 101(4), p.45001. [https://doi.org/10.1209/0295-5075/101/45001 DOI: 10.1209/0295-5075/101/45001]</ref>, and a broad spectrum of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]] including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and short-chain PFAS<ref name="Stratton2015">Stratton, G.R., Bellona, C.L., Dai, F., Holsen, T.M. and Mededovic Thagard, S., 2015. Plasma-Based Water Treatment: Conception and Application of a New General Principle for Reactor Design. Chemical Engineering Journal, 273, pp.543-550. [https://doi.org/10.1016/j.cej.2015.03.059 DOI: 10.1016/j.cej.2015.03.059]</ref><ref name="Singh2019a">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><ref name="Singh2019b">Singh, R.K., Fernando, S., Baygi, S.F., Multari, N., Mededovic Thagard, S., and Holsen, T.M., 2019. Breakdown Products from Perfluorinated Alkyl Substances (PFAS) Degradation in a Plasma-Based Water Treatment Process. Environmental Science and Technology, 53(5), pp.2731-2738. [https://doi.org/10.1021/acs.est.8b07031 DOI: 10.1021/acs.est.8b07031]</ref>. A plasma reactor can simultaneously oxidize and reduce organics by producing a mixture of hydroxyl radicals and aqueous electrons, the latter of which act as strong reducing agents and could be the key species in removing PFAS and other non-oxidizable compounds. Additionally, the plasma process produces no residual waste and requires no chemical additions, although adding surfactants or injecting inert gas into the liquid phase can increase interfacial PFAS concentrations, exposing more of the PFAS to the plasma and therefore increasing removal efficiency.  
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Past and ongoing military operations have resulted in contamination of surface soil with [[Munitions Constituents | munition constituents (MC)]], which have human and environmental health impacts. These compounds can be transported off site via stormwater runoff during precipitation events.  Technologies to “trap and treat” surface runoff before it enters downstream receiving bodies (e.g., streams, rivers, ponds) (see Figure 1), and which are compatible with ongoing range activities are needed. This article describes a passive and sustainable approach for effective management of munition constituents in stormwater runoff.
 
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'''Related Article(s):'''
 
'''Related Article(s):'''
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*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
 
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*[[PFAS Ex Situ Water Treatment]]
 
  
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'''Contributor(s):'''
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*[[Munitions Constituents]]
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*Dr. Selma Mededovic Thagard
 
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*Dr. Thomas Holsen
 
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*Dr. Stephen Richardson, P.E
 
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*Poonam Kulkarni, P.E.
 
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*Dr. Blossom Nzeribe
 
  
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'''Key Resource(s):'''
 
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* [https://pfas-1.itrcweb.org/12-treatment-technologies/#12_2  PFAS – Per- and Polyfluoroalkyl Substances: 12.2 Field-Implemented Liquids Treatment Technologies. Interstate Technology Regulatory Council (ITRC).]  See also: [https://pfas-1.itrcweb.org/12-treatment-technologies/#12_5 12.5 Limited Application and Developing Liquids Treatment Technologies].
 
  
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* Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A review28<ref name="Nzeribe2019">Nzeribe, B.N., Crimi, M., Mededovic Thagard, S. and Holsen, T.M., 2019. Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A review. Critical Reviews in Environmental Science and Technology, 49(10), pp.866-915. [https://doi.org/10.1080/10643389.2018.1542916 DOI: 10.1080/10643389.2018.1542916]</ref>
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'''Contributor:''' Mark E. Fuller
  
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* Low Temperature Plasma for Biology, Hygiene, and Medicine: Perspective and Roadmap<ref name="Laroussi2021">Laroussi, M., Bekeschus, S., Keidar, M., Bogaerts, A., Fridman, A., Lu, X.P., Ostrikov, K.K., Hori, M., Stapelmann, K., Miller, V., Reuter, S., Laux, C., Mesbah, A., Walsh, J., Jiang, C., Mededovic Thagard, S., Tanaka, H., Liu, D.W., Yan, D., and Yusupov, M., 2021. Low Temperature Plasma for Biology, Hygiene, and Medicine: Perspective and Roadmap. IEEE Transactions on Radiation and Plasma Medical Sciences. [https://doi.org/10.1109/TRPMS.2021.3135118 DOI: 10.1109/TRPMS.2021.3135118]  [https://ieeexplore.ieee.org/abstract/document/9650590 Open access article.]</ref>
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'''Key Resource(s):'''
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*SERDP Project ER19-1106: Development of Innovative Passive and Sustainable Treatment Technologies for Energetic Compounds in Surface Runoff on Active Ranges
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==Introduction==
 
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Plasma processing plays an essential role in various industrial applications such as semiconductor fabrication, polymer functionalization, chemical synthesis, agriculture and food safety, health industry, and hazardous waste management<ref name="VanVeldhuizen2002">Van Veldhuizen, E.M., and Rutgers, W.R., 2002. Pulsed Positive Corona Streamer Propagation and Branching. Journal of Physics D: Applied Physics, 35(17), p.2169.  [https://doi.org/10.1088/0022-3727/35/17/313 DOI: 10.1088/0022-3727/35/17/313]</ref><ref name="Yang">Yang, Y., Cho, Y.I. and Fridman, A., 2012. Plasma Discharge in Liquid: Water Treatment and Applications. CRC press. ISBN: 978-1-4398-6623-8  [https://doi.org/10.1201/b11650 DOI: 10.1201/b11650]</ref><ref name="Rezaei2019">Rezaei, F., Vanraes, P., Nikiforov, A., Morent, R., and De Geyter, N., 2019. Applications of Plasma-Liquid Systems: A Review. Materials, 12(17), article 2751, 69 pp.  [https://doi.org/10.3390/ma12172751 DOI: 10.3390/ma12172751]&nbsp;&nbsp;  [https://www.mdpi.com/1996-1944/12/17/2751 Open access article].</ref><ref name="Herianto2021">Herianto, S., Hou, C.Y., Lin, C.M., and Chen, H.L., 2021. Nonthermal plasma-activated water: A comprehensive review of this new tool for enhanced food safety and quality. Comprehensive Reviews in Food Science and Food Safety, 20(1), pp. 583-626. [https://doi.org/10.1111/1541-4337.12667 DOI: 10.1111/1541-4337.12667]</ref>.  Plasma is a gaseous state of matter consisting of charged particles, metastable-state molecules or atoms, and free radicals. Depending on the energy or temperature of the electrons, compared with the temperature of the background gas, plasmas can be classified as thermal or non-thermal. In thermal plasma, an example of which is an electrical arc, individual species’ temperatures typically exceed several thousand kelvins (K). Non-thermal plasmas are formed using less power with temperatures ranging from ambient to approximately 1000 K<ref name="Jiang2014">Jiang, B., Zheng, J., Qiu, S., Wu, M., Zhang, Q., Yan, Z. and Xue, Q., 2014. Review on Electrical Discharge Plasma Technology for Wastewater Remediation. Chemical Engineering Journal, 236, pp. 348–368. [https://doi.org/10.1016/j.cej.2013.09.090 DOI: 10.1016/j.cej.2013.09.090]</ref>. An example of a non-thermal plasma is a dielectric barrier discharge used for commercial ozone generation.
 
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Plasma that is applied in water treatment (Figure 1) is typically non-thermal, which offers high-energy process efficiency and selectivity<ref name="Jiang2014"/><ref name="Magureanu2018">Magureanu, M., Bradu, C., and Parvulescu, V.I., 2018. Plasma Processes for the Treatment of Water Contaminated with Harmful Organic Compounds. Journal of Physics D: Applied Physics, 51(31), p. 313002. [https://doi.org/10.1088/1361-6463/aacd9c DOI:    10.1088/1361-6463/aacd9c]</ref>. Since the 1980s when the first plasma reactor was utilized to oxidize a dye<ref name="Clements1987">Clements, J.S., Sato, M., and Davis, R.H., 1987. Preliminary Investigation of Prebreakdown Phenomena and Chemical Reactions Using a Pulsed High-Voltage Discharge in Water. IEEE Transactions on Industry Applications, IA-23(2), pp. 224-235.  [https://doi.org/10.1109/TIA.1987.4504897 DOI: 10.1109/TIA.1987.4504897]</ref>, over a hundred different plasma reactors have been developed to treat a range of contaminants of environmental importance including biological species. Examples include treatment of pharmaceuticals, volatile organic compounds (VOCs), 1,4-dioxane, herbicides, pesticides, warfare agents, bacteria, yeasts and viruses using direct-in-liquid discharges with and without bubbles and discharges in a gas over and contacting the surface of a liquid. Different excitation sources including AC, nanosecond pulsed and DC voltages have been utilized to produce pulsed corona, corona-like, spark, arc, and glow discharges, among other discharge types. Many reviews of plasma processing for water treatment applications have recently been published<ref name="Zeghioud2020">Zeghioud, H., Nguyen-Tri, P., Khezami, L., Amrane, A., and Assadi, A.A., 2020. Review on Discharge Plasma for Water Treatment: Mechanism, Reactor Geometries, Active Species and Combined Processes. Journal of Water Process Engineering, 38, p.101664. [https://doi.org/10.1016/j.jwpe.2020.101664 DOI: 10.1016/j.jwpe.2020.101664]</ref><ref name="Murugesan2020">Murugesan, P., Evanjalin Monica, V., Moses, J.A., and Anandharamakrishnan, C., 2020. Water Decontamination Using Non-Thermal Plasma: Concepts, Applications, and Prospects. Journal of Environmental Chemical Engineering, 8(5), p. 104377. [https://doi.org/10.1016/j.jece.2020.104377 DOI: 10.1016/j.jece.2020.104377]</ref>.
 
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Plasma-based water treatment (PWT) owes its strong oxidation and disinfection capabilities to the production of reactive oxidative species (ROS), primarily OH radicals, atomic oxygen, singlet oxygen and hydrogen peroxide. The process also produces reductive species such as solvated electrons and reactive nitrogen species (RNS) when nitrogen and oxygen are present in the discharge. This process has the advantage of synergistic effects of high electric fields, UV/VUV light emissions and in some cases shockwave formation in a liquid. It requires no chemical additions, and can be optimized for batch or continuous processing.
 
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==Fundamentals of Sediment Risk Assessment==
 
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[[File: SedRiskFig1.PNG | thumb |700px|Figure 1. Schematic of the sediment risk assessment process]]
 
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Whereas there is strong evidence of anthropogenic impacts on the benthic community at many sediment sites, the degree of toxicity (or even its presence or absence) cannot be predicted with absolute certainty using contaminant concentrations alone<ref name="Apitz2011"/>. A sediment ERA should include lines of evidence (LOEs) derived from several different investigations<ref name="Wenning2005"/>. One common approach to develop several of these LOEs in a decision framework is the triad approach. Triad-based assessment frameworks require evidence based on sediment chemistry, toxicity, and benthic community structure (possibly including evidence of bioaccumulation) to designate sediment as toxic and requiring management or control<ref name="Chapman1996">Chapman, P.M., Paine, M.D., Arthur, A.D., Taylor, L.A., 1996. A triad study of sediment quality associated with a major, relatively untreated marine sewage discharge. Marine Pollution Bulletin 32(1), pp. 47–64.  [https://doi.org/10.1016/0025-326X(95)00108-Y DOI: 10.1016/0025-326X(95)00108-Y]</ref>. In some decision frameworks, particularly those used to establish and rank risks in national or regional programs, all components of the triad are carried out simultaneously, with the various LOEs combined to support weight of evidence (WOE) decision making. In other frameworks, LOEs are tiered to minimize costs by collecting only the data required to make a decision and leaving some potential consequences and uncertainties unresolved.
 
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Figure 1 provides an overview of a sediment risk assessment process. The first step, and a fundamental requirement, in sediment risk assessment, involves scoping and planning prior to undertaking work. This is important for optimizing the available assessment resource and conducting an assessment at the appropriate level of detail that is transparent and free, to the extent possible, of any bias or preconceived beliefs concerning the outcome<ref name="Hill2000">Hill, R.A., Chapman, P.M., Mann, G.S. and Lawrence, G.S., 2000. Level of Detail in Ecological Risk Assessments. Marine Pollution Bulletin, 40(6), pp. 471-477. [https://doi.org/10.1016/S0025-326X(00)00036-9 DOI: 10.1016/S0025-326X(00)00036-9]</ref>.
 
  
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===Screening-Level Risk Assessment (SLRA)===
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==Background==
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Technical guidance in many countries strongly encourages sediment risk assessment to begin with a Screening-Level Risk Assessment (SLRA)<ref name="USEPA2005"/><ref name="Tarazona2014"/><ref name="Fletcher2008"/>. The SLRA is a simplified risk assessment conducted using limited data and often assuming certain, generally conservative and generic, sediment characteristics, sediment contaminant levels, and exposure parameters in the absence of sufficient readily available information<ref name="Hope2006">Hope, B.K., 2006. An examination of ecological risk assessment and management practices. Environment International, 32(8), pp. 983-995. [https://doi.org/10.1016/j.envint.2006.06.005 DOI: 10.1016/j.envint.2006.06.005]</ref><ref name="Weinstein2010">Weinstein, J.E., Crawford, K.D., Garner, T.R. and Flemming, A.J., 2010. Screening-level ecological and human health risk assessment of polycyclic aromatic hydrocarbons in stormwater detention pond sediments of Coastal South Carolina, USA. Journal of Hazardous Materials, 178(1-3), pp. 906-916. [https://doi.org/10.1016/j.jhazmat.2010.02.024 DOI: 10.1016/j.jhazmat.2010.02.024]</ref><ref name="Rak2008">Rak, A., Maly, M.E., Tracey, G., 2008. A Guide to Screening Level Ecological Risk Assessment, TG-090801. Tri-Services Ecological Risk Assessment Working Group (TSERAWG), U.S. Army Biological Technical Assistance Group (BTAG), Aberdeen Proving Ground, MD. 26 pp. [https://usaphcapps.amedd.army.mil/erawg/SLERA.pdf Free Download]&nbsp;&nbsp; [[Media: Rak2008.pdf | Report.pdf]]</ref><ref name="USEPA2001">US Environmental Protection Agency (USEPA), 2001. ECO Update. The Role of Screening-Level Risk Assessments and Refining Contaminants of Concern in Baseline Ecological Risk Assessments. EPA 540/F-01/014. Washington, D.C. [https://www.epa.gov/sites/default/files/2015-09/documents/slera0601.pdf  Website]&nbsp;&nbsp; [[Media: EPA 540_F-01_014.pdf  | Report.pdf]]</ref>.
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===Surface Runoff Characteristics and Treatment Approaches===
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[[File: FullerFig1.png | thumb | 400 px | left | Figure 1. Conceptual model of passive trap and treat approach for MC removal from stormwater runoff]]
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During&nbsp;large&nbsp;precipitation&nbsp;events the rate of water deposition exceeds the rate of water infiltration, resulting in surface runoff (also called stormwater runoff). Surface characteristics including soil texture, presence of impermeable surfaces (natural and artificial), slope, and density and type of vegetation all influence the amount of surface runoff from a given land area. The use of passive systems such as retention ponds and biofiltration cells for treatment of surface runoff is well established for urban and roadway runoff. Treatment in those cases is typically achieved by directing runoff into and through a small constructed wetland, often at the outlet of a retention basin, or via filtration by directing runoff through a more highly engineered channel or vault containing the treatment materials. Filtration based technologies have proven to be effective for the removal of metals, organics, and suspended solids<ref>Sansalone, J.J., 1999. In-situ performance of a passive treatment system for metal source control. Water Science and Technology, 39(2), pp. 193-200. [https://doi.org/10.1016/S0273-1223(99)00023-2 doi: 10.1016/S0273-1223(99)00023-2]</ref><ref>Deletic, A., Fletcher, T.D., 2006. Performance of grass filters used for stormwater treatment—A field and modelling study. Journal of Hydrology, 317(3-4), pp. 261-275. [http://dx.doi.org/10.1016/j.jhydrol.2005.05.021 doi: 10.1016/j.jhydrol.2005.05.021]</ref><ref>Grebel, J.E., Charbonnet, J.A., Sedlak, D.L., 2016. Oxidation of organic contaminants by manganese oxide geomedia for passive urban stormwater treatment systems. Water Research, 88, pp. 481-491. [http://dx.doi.org/10.1016/j.watres.2015.10.019 doi: 10.1016/j.watres.2015.10.019]</ref><ref>Seelsaen, N., McLaughlan, R., Moore, S., Ball, J.E., Stuetz, R.M., 2006. Pollutant removal efficiency of alternative filtration media in stormwater treatment. Water Science and Technology, 54(6-7), pp. 299-305. [https://doi.org/10.2166/wst.2006.617 doi: 10.2166/wst.2006.617]</ref>.
  
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The analysis is often semi-quantitative, and typically includes comparisons of various chemical and physical sediment conditions to threshold limits established in national or international regulations or by generally accepted scientific interpretations. US technical guidance encourages the comparison of contaminant measurements in water, sediment, or soil to National Oceanographic and Atmospheric Administration (NOAA) sediment screening quick reference tables, or SQuiRT cards, which list quality guidelines from a range of sources, based on differing narrative intent<ref name="Buchman2008">Buchman, M.F., 2008. Screening Quick Reference Tables (SQuiRTs), NOAA OR&R Report 08-1. National Oceanographic and Atmospheric Administration (NOAA), Coastal Protection and Restoration Protection Division. 34 pp. [https://repository.library.noaa.gov/view/noaa/9327  website]&nbsp;&nbsp; [[Media: SQuiRTs2008.pdf | Report.pdf]]</ref>.
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===Surface Runoff on Ranges===
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[[File: FullerFig2.png | thumb | 600 px | Figure 2. Conceptual illustration of munition constituent production and transport on military ranges. Mesoscale residues are qualitatively defined as being easily visible to the naked eye (e.g., from around 50 µm to multiple cm in size) and less likely to be transported by moving water.  Microscale residues are defined as <50 µm down to below 1 µm, and more likely to be entrained in, and transported by, moving water as particulates. Blue arrows represent possible water flow paths and include both dissolved and solid phase energetics. The red vertical arrow represents the predominant energetics dissolution process in close proximity to the residues due to precipitation.]]
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Surface&nbsp;runoff&nbsp;represents&nbsp;a&nbsp;major potential mechanism through which energetics residues and related materials are transported off site from range soils to groundwater and surface water receptors (Figure 2). This process is particularly important for energetics that are water soluble (e.g., [[Wikipedia: Nitrotriazolone | NTO]] and [[Wikipedia: Nitroguanidine | NQ]]) or generate soluble daughter products (e.g., [[Wikipedia: 2,4-Dinitroanisole | DNAN]] and [[Wikipedia: TNT | TNT]]). While traditional MC such as [[Wikipedia: RDX | RDX]] and [[Wikipedia: HMX | HMX]] have limited aqueous solubility, they also exhibit recalcitrance to degrade under most natural conditions. RDX and [[Wikipedia: Perchlorate | perchlorate]] are frequent groundwater contaminants on military training ranges. While actual field measurements of energetics in surface runoff are limited, laboratory experiments have been performed to predict mobile energetics contamination levels based on soil mass loadings<ref>Cubello, F., Polyakov, V., Meding, S.M., Kadoya, W., Beal, S., Dontsova, K., 2024. Movement of TNT and RDX from composition B detonation residues in solution and sediment during runoff. Chemosphere, 350, Article 141023. [https://doi.org/10.1016/j.chemosphere.2023.141023 doi: 10.1016/j.chemosphere.2023.141023]</ref><ref>Karls, B., Meding, S.M., Li, L., Polyakov, V., Kadoya, W., Beal, S., Dontsova, K., 2023. A laboratory rill study of IMX-104 transport in overland flow. Chemosphere, 310, Article 136866. [https://doi.org/10.1016/j.chemosphere.2022.136866 doi: 10.1016/j.chemosphere.2022.136866]&nbsp; [[Media: KarlsEtAl2023.pdf | Open Access Article]]</ref><ref>Polyakov, V., Beal, S., Meding, S.M., Dontsova, K., 2025. Effect of gypsum on transport of IMX-104 constituents in overland flow under simulated rainfall. Journal of Environmental Quality, 54(1), pp. 191-203. [https://doi.org/10.1002/jeq2.20652 doi: 10.1002/jeq2.20652]&nbsp; [[Media: PolyakovEtAl2025.pdf | Open Access Article.pdf]]</ref><ref>Polyakov, V., Kadoya, W., Beal, S., Morehead, H., Hunt, E., Cubello, F., Meding, S.M., Dontsova, K., 2023. Transport of insensitive munitions constituents, NTO, DNAN, RDX, and HMX in runoff and sediment under simulated rainfall. Science of the Total Environment, 866, Article 161434. [https://doi.org/10.1016/j.scitotenv.2023.161434 doi: 10.1016/j.scitotenv.2023.161434]&nbsp; [[Media: PolyakovEtAl2023.pdf | Open Access Article.pdf]]</ref><ref>Price, R.A., Bourne, M., Price, C.L., Lindsay, J., Cole, J., 2011. Transport of RDX and TNT from Composition-B Explosive During Simulated Rainfall. In: Environmental Chemistry of Explosives and Propellant Compounds in Soils and Marine Systems: Distributed Source Characterization and Remedial Technologies. American Chemical Society, pp. 229-240. [https://doi.org/10.1021/bk-2011-1069.ch013 doi: 10.1021/bk-2011-1069.ch013]</ref>. For example, in a previous small study, MC were detected in surface runoff from an active live-fire range<ref>Fuller, M.E., 2015. Fate and Transport of Colloidal Energetic Residues. Department of Defense Strategic Environmental Research and Development Program (SERDP), Project ER-1689. [https://serdp-estcp.mil/projects/details/10760fd6-fb55-4515-a629-f93c555a92f0 Project Website]&nbsp;&nbsp; [[Media: ER-1689-FR.pdf | Final Report.pdf]]</ref>, and more recent sampling has detected MC in marsh surface water adjacent to the same installation (personal communication).  Another recent report from Canada also detected RDX in both surface runoff and surface water at low part per billion levels in a survey of several military demolition sites<ref>Lapointe, M.-C., Martel, R., Diaz, E., 2017. A Conceptual Model of Fate and Transport Processes for RDX Deposited to Surface Soils of North American Active Demolition Sites. Journal of Environmental Quality, 46(6), pp. 1444-1454. [https://doi.org/10.2134/jeq2017.02.0069 doi: 10.2134/jeq2017.02.0069]</ref>. However, overall, data regarding the MC contaminant profile of surface runoff from ranges is very limited, and the possible presence of non-energetic constituents (e.g., metals, binders, plasticizers) in runoff has not been examined.  Additionally, while energetics-contaminated surface runoff is an important concern, mitigation technologies specifically for surface runoff have not yet been developed and widely deployed in the field.  To effectively capture and degrade MC and associated compounds that are present in surface runoff, novel treatment media are needed to sorb a broad range of energetic materials and to transform the retained compounds through abiotic and/or microbial processes.
  
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The screening level approach is intended to minimize the chances of concluding that there is no risk when, in fact, risk may exist. Thus, the results of an SLRA may indicate contaminants or sediments in certain locations in the original study area initially thought to be of concern are acceptable (i.e., contaminant levels are below threshold levels), or that contaminant levels are high enough to indicate immediate action without further assessment (e.g., contaminant levels are well above probable-effects guidelines). In other cases, or at other locations, SLRA may indicate the need for further examination. Further study may apply site-specific, rather than generic and conservative assumptions, to reduce uncertainty.  
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Surface runoff of organic and inorganic contaminants from live-fire ranges is a challenging issue for the Department of Defense (DoD). Potentially even more problematic is the fact that inputs to surface waters from large testing and training ranges typically originate from multiple sources, often encompassing hundreds of acres. No available technologies are currently considered effective for controlling non-point source energetics-laden surface runoff. While numerous technologies exist to treat collected explosives residues, contaminated soil and even groundwater, the decentralized nature and sheer volume of military range runoff have precluded the use of treatment technologies at full scale in the field.
  
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===Detailed Risk Assessment===
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==Range Runoff Treatment Technology Components==
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Detailed sediment risk assessment is conducted when SLRA results indicate one or more sediment contaminants exceed background conditions or regulatory threshold limits. For some contaminants, such as the dioxins and other persistent, bioaccumulative, and toxic substances (PBTs), technical guidance may mandate further examination, regardless of whether threshold levels are exceeded<ref name="Solomon2013">Solomon, K., Matthies, M., and Vighi, M., 2013. Assessment of PBTs in the European Union: a critical assessment of the proposed evaluation scheme with reference to plant protection products. Environmental Sciences Europe, 25(1), pp. 1-17.  [https://doi.org/10.1186/2190-4715-25-10 DOI: 10.1186/2190-4715-25-10]&nbsp;&nbsp; [https://enveurope.springeropen.com/articles/10.1186/2190-4715-25-10 Open Access Article]</ref><ref name="Matthies2016">Matthies, M., Solomon, K., Vighi, M., Gilman, A. and Tarazona, J.V., 2016. The origin and evolution of assessment criteria for persistent, bioaccumulative and toxic (PBT) chemicals and persistent organic pollutants (POPs). Environmental Science: Processes and Impacts, 18(9), pp. 1114-1128.  [https://doi.org/10.1039/C6EM00311G DOI: 10.1039/C6EM00311G]</ref>. Detailed sediment risk assessment typically follows a three-step framework similar to that described for ecological risk assessment - problem formulation, exposure analysis, and risk characterization<ref name="Suter2008">Suter, G.W., 2008. Ecological Risk Assessment in the United States Environmental Protection Agency: A Historical Overview. Integrated Environmental Assessment And Management, 4(3), pp. 285-289.  [https://doi.org/10.1897/IEAM_2007-062.1 DOI: 10.1897/IEAM_2007-062.1]&nbsp;&nbsp; Free download from: [https://bioone.org/journals/integrated-environmental-assessment-and-management/volume-4/issue-3/IEAM_2007-062.1/Ecological-Risk-Assessment-in-the-United-States-Environmental-Protection-Agency/10.1897/IEAM_2007-062.1.pdf?casa_token=ieq3Cnc-YdIAAAAA:_MH-gpnwpJKvZSV2Qew43Y4ocdgADq1HvugpvmrblcGONMJgvIjYB52zQnXn_oAUW0gTy5GAkfY BioOne]</ref>.
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Based on the conceptual foundation of previous research into surface water runoff treatment for other contaminants, with a goal to “trap and treat” the target compounds, the following components were selected for inclusion in the technology developed to address range runoff contaminated with energetic compounds.
  
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US sediment management guidance describes a detailed risk assessment process similar to that followed for US ecological risk assessment<ref name="USEPA2005"/>. The first step is problem formulation. It involves defining chemical and physical conditions, delineating the spatial footprint of the sediment area to be examined, and identifying the human uses and ecological features of the sediment. Historical data are included in this initial step to better understand the results of biota, sediment, and water sampling as well as laboratory toxicity testing results. The SLRA is often included as a part of problem formulation.
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===Peat===
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Previous research demonstrated that a peat-based system provided a natural and sustainable sorptive medium for organic explosives such as HMX, RDX, and TNT, allowing much longer residence times than predicted from hydraulic loading alone<ref>Fuller, M.E., Hatzinger, P.B., Rungkamol, D., Schuster, R.L., Steffan, R.J., 2004. Enhancing the attenuation of explosives in surface soils at military facilities: Combined sorption and biodegradation. Environmental Toxicology and Chemistry, 23(2), pp. 313-324. [https://doi.org/10.1897/03-187 doi: 10.1897/03-187]</ref><ref>Fuller, M.E., Lowey, J.M., Schaefer, C.E., Steffan, R.J., 2005. A Peat Moss-Based Technology for Mitigating Residues of the Explosives TNT, RDX, and HMX in Soil. Soil and Sediment Contamination: An International Journal, 14(4), pp. 373-385. [https://doi.org/10.1080/15320380590954097 doi: 10.1080/15320380590954097]</ref><ref name="FullerEtAl2009">Fuller, M.E., Schaefer, C.E., Steffan, R.J., 2009. Evaluation of a peat moss plus soybean oil (PMSO) technology for reducing explosive residue transport to groundwater at military training ranges under field conditions. Chemosphere, 77(8), pp. 1076-1083. [https://doi.org/10.1016/j.chemosphere.2009.08.044 doi: 10.1016/j.chemosphere.2009.08.044]</ref><ref>Hatzinger, P.B., Fuller, M.E., Rungkamol, D., Schuster, R.L., Steffan, R.J., 2004. Enhancing the attenuation of explosives in surface soils at military facilities: Sorption-desorption isotherms. Environmental Toxicology and Chemistry, 23(2), pp. 306-312. [https://doi.org/10.1897/03-186 doi: 10.1897/03-186]</ref><ref name="SchaeferEtAl2005">Schaefer, C.E., Fuller, M.E., Lowey, J.M., Steffan, R.J., 2005. Use of Peat Moss Amended with Soybean Oil for Mitigation of Dissolved Explosive Compounds Leaching into the Subsurface: Insight into Mass Transfer Mechanisms. Environmental Engineering Science, 22(3), pp. 337-349. [https://doi.org/10.1089/ees.2005.22.337 doi: 10.1089/ees.2005.22.337]</ref>. Peat moss represents a bioactive environment for treatment of the target contaminants. While the majority of the microbial reactions are aerobic due to the presence of measurable dissolved oxygen in the bulk solution, anaerobic reactions (including methanogenesis) can occur in microsites within the peat. The peat-based substrate acts not only as a long term electron donor as it degrades but also acts as a strong sorbent. This is important in intermittently loaded systems in which a large initial pulse of MC can be temporarily retarded on the peat matrix and then slowly degraded as they desorb<ref name="FullerEtAl2009"/><ref name="SchaeferEtAl2005"/>. This increased residence time enhances the biotransformation of energetics and promotes the immobilization and further degradation of breakdown products. Abiotic degradation reactions are also likely enhanced by association with the organic-rich peat (e.g., via electron shuttling reactions of [[Wikipedia: Humic substance | humics]])<ref>Roden, E.E., Kappler, A., Bauer, I., Jiang, J., Paul, A., Stoesser, R., Konishi, H., Xu, H., 2010. Extracellular electron transfer through microbial reduction of solid-phase humic substances. Nature Geoscience, 3, pp. 417-421. [https://doi.org/10.1038/ngeo870 doi: 10.1038/ngeo870]</ref>.
  
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The second step is exposure analysis. This step includes the identification of pathways by which human and aquatic organisms might directly or indirectly contact contaminants in the sediment. The exposure route (i.e., ingestion, dermal, or inhalation of particulates or gaseous emissions) and both the frequency and duration of contact (i.e., hourly, daily, or seasonally) are determined for each contaminant exposure pathway and human and ecological receptor. The environmental fate of the contaminant, factors affecting uptake, and the overall exposure dose are included in the calculation of the level of contaminant exposure. The exposure analysis also includes an effects assessment, whereby the biological response and associated level required to manifest different biological responses are determined for each contaminant.
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===Soybean Oil===
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Modeling has indicated that peat moss amended with crude soybean oil would significantly reduce the flux of dissolved TNT, RDX, and HMX through the vadose zone to groundwater compared to a non-treated soil (see [https://serdp-estcp.mil/projects/details/20e2f05c-fd50-4fd3-8451-ba73300c7531 ESTCP ER-200434]). The technology was validated in field soil plots, showing a greater than 500-fold reduction in the flux of dissolved RDX from macroscale Composition B detonation residues compared to a non-treated control plot<ref name="FullerEtAl2009"/>. Laboratory testing and modeling indicated that the addition of soybean oil increased the biotransformation rates of RDX and HMX at least 10-fold compared to rates observed with peat moss alone<ref name="SchaeferEtAl2005"/>. Subsequent experiments also demonstrated the effectiveness of the amended peat moss material for stimulating perchlorate transformation when added to a highly contaminated soil (Fuller et al., unpublished data). These previous findings clearly demonstrate the effectiveness of peat-based materials for mitigating transport of both organic and inorganic energetic compounds through soil to groundwater.  
  
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The third step is risk-characterization. It involves calculating the risks for each human and ecological receptor posed by each sediment contaminant, as well as the cumulative risk associated with the combined exposure to all contaminants exerting similar biological effects. An uncertainty analysis is often included in this step of the risk assessment to convey where knowledge or data are lacking regarding the presence of the contaminant in the sediment, the biological response associated with exposure to the contaminant, or the behavior of the receptor with respect to contact with the sediment. A sensitivity analysis also may be conducted to convey the range of exposures (lowest, typical, and worst-case) and risks associated with changes in key assumptions and parameter values used in the exposure calculations and effects assessment.
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===Biochar===
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Recent reports have highlighted additional materials that, either alone, or in combination with electron donors such as peat moss and soybean oil, may further enhance the sorption and degradation of surface runoff contaminants, including both legacy energetics and [[Wikipedia: Insensitive_munition#Insensitive_high_explosives | insensitive high explosives (IHE)]]. For instance, [[Wikipedia: Biochar | biochar]], a type of black carbon, has been shown to not only sorb a wide range of organic and inorganic contaminants including MCs<ref>Ahmad, M., Rajapaksha, A.U., Lim, J.E., Zhang, M., Bolan, N., Mohan, D., Vithanage, M., Lee, S.S., Ok, Y.S., 2014. Biochar as a sorbent for contaminant management in soil and water: A review. Chemosphere, 99, pp. 19-33. [https://doi.org/10.1016/j.chemosphere.2013.10.071 doi: 10.1016/j.chemosphere.2013.10.071]</ref><ref>Mohan, D., Sarswat, A., Ok, Y.S., Pittman, C.U., 2014. Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent – A critical review. Bioresource Technology, 160, pp. 191-202. [https://doi.org/10.1016/j.biortech.2014.01.120 doi: 10.1016/j.biortech.2014.01.120]</ref><ref>Oh, S.-Y., Seo, Y.-D., Jeong, T.-Y., Kim, S.-D., 2018. Sorption of Nitro Explosives to Polymer/Biomass-Derived Biochar. Journal of Environmental Quality, 47(2), pp. 353-360. [https://doi.org/10.2134/jeq2017.09.0357 doi: 10.2134/jeq2017.09.0357]</ref><ref>Xie, T., Reddy, K.R., Wang, C., Yargicoglu, E., Spokas, K., 2015. Characteristics and Applications of Biochar for Environmental Remediation: A Review. Critical Reviews in Environmental Science and Technology, 45(9), pp. 939-969. [https://doi.org/10.1080/10643389.2014.924180 doi: 10.1080/10643389.2014.924180]</ref>, but also to facilitate their degradation<ref>Oh, S.-Y., Cha, D.K., Kim, B.-J., Chiu, P.C., 2002. Effect of adsorption to elemental iron on the transformation of 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine in solution. Environmental Toxicology and Chemistry, 21(7), pp. 1384-1389. [https://doi.org/10.1002/etc.5620210708 doi: 10.1002/etc.5620210708]</ref><ref>Ye, J., Chiu, P.C., 2006. Transport of Atomic Hydrogen through Graphite and its Reaction with Azoaromatic Compounds. Environmental Science and Technology, 40(12), pp. 3959-3964. [https://doi.org/10.1021/es060038x doi: 10.1021/es060038x]</ref><ref name="OhChiu2009">Oh, S.-Y., Chiu, P.C., 2009. Graphite- and Soot-Mediated Reduction of 2,4-Dinitrotoluene and Hexahydro-1,3,5-trinitro-1,3,5-triazine. Environmental Science and Technology, 43(18), pp. 6983-6988. [https://doi.org/10.1021/es901433m doi: 10.1021/es901433m]</ref><ref name="OhEtAl2013">Oh, S.-Y., Son, J.-G., Chiu, P.C., 2013. Biochar-mediated reductive transformation of nitro herbicides and explosives. Environmental Toxicology and Chemistry, 32(3), pp. 501-508. [https://doi.org/10.1002/etc.2087 doi: 10.1002/etc.2087]&nbsp;&nbsp; [[Media: OhEtAl2013.pdf | Open Access Article.pdf]]</ref><ref name="XuEtAl2010">Xu, W., Dana, K.E., Mitch, W.A., 2010. Black Carbon-Mediated Destruction of Nitroglycerin and RDX by Hydrogen Sulfide. Environmental Science and Technology, 44(16), pp. 6409-6415. [https://doi.org/10.1021/es101307n doi: 10.1021/es101307n]</ref><ref>Xu, W., Pignatello, J.J., Mitch, W.A., 2013. Role of Black Carbon Electrical Conductivity in Mediating Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) Transformation on Carbon Surfaces by Sulfides. Environmental Science and Technology, 47(13), pp. 7129-7136. [https://doi.org/10.1021/es4012367 doi: 10.1021/es4012367]</ref>. Depending on the source biomass and [[Wikipedia: Pyrolysis| pyrolysis]] conditions, biochar can possess a high [[Wikipedia: Specific surface area | specific surface area]] (on the order of several hundred m<small><sup>2</sup></small>/g)<ref>Zhang, J., You, C., 2013. Water Holding Capacity and Absorption Properties of Wood Chars. Energy and Fuels, 27(5), pp. 2643-2648. [https://doi.org/10.1021/ef4000769 doi: 10.1021/ef4000769]</ref><ref>Gray, M., Johnson, M.G., Dragila, M.I., Kleber, M., 2014. Water uptake in biochars: The roles of porosity and hydrophobicity. Biomass and Bioenergy, 61, pp. 196-205. [https://doi.org/10.1016/j.biombioe.2013.12.010 doi: 10.1016/j.biombioe.2013.12.010]</ref> and hence a high sorption capacity.  Biochar and other black carbon also exhibit especially high affinity for [[Wikipedia: Nitro compound | nitroaromatic compounds (NACs)]] including TNT and 2,4-dinitrotoluene (DNT)<ref>Sander, M., Pignatello, J.J., 2005. Characterization of Charcoal Adsorption Sites for Aromatic Compounds:  Insights Drawn from Single-Solute and Bi-Solute Competitive Experiments. Environmental Science and Technology, 39(6), pp. 1606-1615. [https://doi.org/10.1021/es049135l doi: 10.1021/es049135l]</ref><ref name="ZhuEtAl2005">Zhu, D., Kwon, S., Pignatello, J.J., 2005. Adsorption of Single-Ring Organic Compounds to Wood Charcoals Prepared Under Different Thermochemical Conditions. Environmental Science and Technology 39(11), pp. 3990-3998. [https://doi.org/10.1021/es050129e doi: 10.1021/es050129e]</ref><ref name="ZhuPignatello2005">Zhu, D., Pignatello, J.J., 2005. Characterization of Aromatic Compound Sorptive Interactions with Black Carbon (Charcoal) Assisted by Graphite as a Model. Environmental Science and Technology, 39(7), pp. 2033-2041. [https://doi.org/10.1021/es0491376 doi: 10.1021/es0491376]</ref>. This is due to the strong [[Wikipedia: Pi-interaction | ''&pi;-&pi;'' electron donor-acceptor interactions]] between electron-rich graphitic domains in black carbon and the electron-deficient aromatic ring of the NAC<ref name="ZhuEtAl2005"/><ref name="ZhuPignatello2005"/>. These characteristics make biochar a potentially effective, low cost, and sustainable sorbent for removing MC and other contaminants from surface runoff and retaining them for subsequent degradation ''in situ''.
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==Key Considerations==
 
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===Stakeholder Engagement===
 
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Stakeholder involvement is widely acknowledged as an important element of [[Wikipedia: Dredging | dredged]] material management<ref name="Collier2014">Collier, Z.A., Bates, M.E., Wood, M.D. and Linkov, I., 2014. Stakeholder engagement in dredged material management decisions. Science of the Total Environment, 496, pp. 248-256. [https://doi.org/10.1016/j.scitotenv.2014.07.044 DOI: 10.1016/j.scitotenv.2014.07.044] Free download from: [https://www.researchgate.net/profile/Matthew-Bates-9/publication/264460412_Stakeholder_Engagement_in_Dredged_Material_Management_Decisions/links/5a9d50fbaca2721e3f32adea/Stakeholder-Engagement-in-Dredged-Material-Management-Decisions.pdf ResearchGate]</ref>, sediment remediation<ref name="Oen2010">Oen, A.M.P., Sparrevik, M., Barton, D.N., Nagothu, U.S., Ellen, G.J., Breedveld, G.D., Skei, J. and Slob, A., 2010. Sediment and society: an approach for assessing management of contaminated sediments and stakeholder involvement in Norway. Journal of Soils and Sediments, 10(2), pp. 202-208. [https://doi.org/10.1007/s11368-009-0182-x DOI: 10.1007/s11368-009-0182-x]</ref>, and other environmental and sediment related activities<ref name="Gerrits2004">Gerrits, L. and Edelenbos, J., 2004. Management of Sediments Through Stakeholder Involvement. Journal of Soils and Sediments, 4(4), pp. 239-246. [https://doi.org/10.1007/BF02991120 DOI: 10.1007/BF02991120]</ref><ref name="Braun2019">Braun, A.B., da Silva Trentin, A.W., Visentin, C. and Thomé, A., 2019. Sustainable remediation through the risk management perspective and stakeholder involvement: A systematic and bibliometric view of the literature. Environmental Pollution, 255(1), p.113221. [https://doi.org/10.1016/j.envpol.2019.113221 DOI: 10.1016/j.envpol.2019.113221]</ref>.
 
  
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Sediment management, particularly at the river basin scale, involves a wide variety of different environmental, governmental, and societal issues<ref name="Liu2018">Liu, C., Walling, D.E. and He, Y., 2018. The International Sediment Initiative case studies of sediment problems in river basins and their management. International Journal of Sediment Research, 33(2), pp. 216-219.  [https://doi.org/10.1016/j.ijsrc.2017.05.005 DOI: 10.1016/j.ijsrc.2017.05.005]  Free download from: [https://www.researchgate.net/profile/Cheng-Liu-43/publication/317032034_Review_The_International_Sediment_Initiative_Case_Studies_of_sediment_problems_in_river_basins_and_their_management/links/5f4f37d2299bf13a319703df/Review-The-International-Sediment-Initiative-Case-Studies-of-sediment-problems-in-river-basins-and-their-management.pdf ResearchGate]</ref>. Incorporating these different views, interests, and perspectives into a form that builds consensus for whatever actions and goals are in mind (e.g., commercial ports and shipping, navigation, flood protection, or habitat restoration) necessitates a formal stakeholder engagement process<ref name="Slob2008">Slob, A.F.L., Ellen, G.J. and Gerrits, L., 2008. Sediment management and stakeholder involvement. In: Sustainable Management of Sediment Resources, Vol. 4: Sediment Management at the River Basin Scale, Owens, P.N. (ed.), pp. 199-216. Elsevier.  [https://doi.org/10.1016/S1872-1990(08)80009-8 DOI: 10.1016/S1872-1990(08)80009-8]</ref>.
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Furthermore, black carbon such as biochar can promote abiotic and microbial transformation reactions by facilitating electron transfer.  That is, biochar is not merely a passive sorbent for contaminants, but also a redox mediator for their degradation.  Biochar can promote contaminant degradation through two different mechanisms: electron conduction and electron storage<ref>Sun, T., Levin, B.D.A., Guzman, J.J.L., Enders, A., Muller, D.A., Angenent, L.T., Lehmann, J., 2017. Rapid electron transfer by the carbon matrix in natural pyrogenic carbon. Nature Communications, 8, Article 14873. [https://doi.org/10.1038/ncomms14873 doi: 10.1038/ncomms14873]&nbsp;&nbsp; [[Media: SunEtAl2017.pdf | Open Access Article.pdf]]</ref>.  
  
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Results from a three-year (2008-2010) [https://www.ngi.no/eng/Projects/Sediment-and-society Sediment and Society] research project funded by the Norwegian Research Council point to three important challenges that must be resolved for successful stakeholder engagement: (1) how to include people who have important management information and local knowledge, but not much influence in the decision-making process; (2) how to secure resources to ensure participation and (3) how to engage and motivate stakeholders to participate early in the sediment remediation planning process<ref name="Oen2010"/>.
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First, the microscopic graphitic regions in biochar can adsorb contaminants like NACs strongly, as noted above, and also conduct reducing equivalents such as electrons and atomic hydrogen to the sorbed contaminants, thus promoting their reductive degradation.  This catalytic process has been demonstrated for TNT, DNT, RDX, HMX, and [[Wikipedia: Nitroglycerin | nitroglycerin]]<ref>Oh, S.-Y., Cha, D.K., Chiu, P.C., 2002. Graphite-Mediated Reduction of 2,4-Dinitrotoluene with Elemental Iron. Environmental Science and Technology, 36(10), pp. 2178-2184. [https://doi.org/10.1021/es011474g doi: 10.1021/es011474g]</ref><ref>Oh, S.-Y., Cha, D.K., Kim, B.J., Chiu, P.C., 2004. Reduction of Nitroglycerin with Elemental Iron:  Pathway, Kinetics, and Mechanisms. Environmental Science and Technology, 38(13), pp. 3723-3730. [https://doi.org/10.1021/es0354667 doi: 10.1021/es0354667]</ref><ref>Oh, S.-Y., Cha, D.K., Kim, B.J., Chiu, P.C., 2005. Reductive transformation of hexahydro-1,3,5-trinitro-1,3,5-triazine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, and methylenedinitramine with elemental iron. Environmental Toxicology and Chemistry, 24(11), pp. 2812-2819. [https://doi.org/10.1897/04-662R.1 doi: 10.1897/04-662R.1]</ref><ref name="OhChiu2009"/><ref name="XuEtAl2010"/> and is expected to occur also for IHE including DNAN and NTO.  
  
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===Conceptual Site Model===
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Second, biochar contains in its structure abundant redox-facile functional groups such as [[Wikipedia: Quinone | quinones]] and [[Wikipedia: Hydroquinone | hydroquinones]], which are known to accept and donate electrons reversibly.  Depending on the biomass and pyrolysis temperature, certain biochar can possess a rechargeable electron storage capacity (i.e., reversible electron accepting and donating capacity) on the order of several millimoles e<small><sup>–</sup></small>/g<ref>Klüpfel, L., Keiluweit, M., Kleber, M., Sander, M., 2014. Redox Properties of Plant Biomass-Derived Black Carbon (Biochar). Environmental Science and Technology, 48(10), pp. 5601-5611. [https://doi.org/10.1021/es500906d doi: 10.1021/es500906d]</ref><ref>Prévoteau, A., Ronsse, F., Cid, I., Boeckx, P., Rabaey, K., 2016. The electron donating capacity of biochar is dramatically underestimated. Scientific Reports, 6, Article 32870. [https://doi.org/10.1038/srep32870 doi: 10.1038/srep32870]&nbsp;&nbsp; [[Media: PrevoteauEtAl2016.pdf | Open Access Article.pdf]]</ref><ref>Xin, D., Xian, M., Chiu, P.C., 2018. Chemical methods for determining the electron storage capacity of black carbon. MethodsX, 5, pp. 1515-1520. [https://doi.org/10.1016/j.mex.2018.11.007 doi: 10.1016/j.mex.2018.11.007]&nbsp;&nbsp; [[Media: XinEtAl2018.pdf | Open Access Article.pdf]]</ref>. This means that when "charged", biochar can provide electrons for either abiotic or biotic degradation of reducible compounds such as MC. The abiotic reduction of DNT and RDX mediated by biochar has been demonstrated<ref name="OhEtAl2013"/> and similar reactions are expected to occur for DNAN and NTO as well. Recent studies have shown that the electron storage capacity of biochar is also accessible to microbes.  For example, soil bacteria such as [[Wikipedia: Geobacter | ''Geobacter'']] and [[Wikipedia: Shewanella | ''Shewanella'']] species can utilize oxidized (or "discharged") biochar as an electron acceptor for the oxidation of organic substrates such as lactate and acetate<ref>Kappler, A., Wuestner, M.L., Ruecker, A., Harter, J., Halama, M., Behrens, S., 2014. Biochar as an Electron Shuttle between Bacteria and Fe(III) Minerals. Environmental Science and Technology Letters, 1(8), pp. 339-344. [https://doi.org/10.1021/ez5002209 doi: 10.1021/ez5002209]</ref><ref name="SaquingEtAl2016">Saquing, J.M., Yu, Y.-H., Chiu, P.C., 2016. Wood-Derived Black Carbon (Biochar) as a Microbial Electron Donor and Acceptor. Environmental Science and Technology Letters, 3(2), pp. 62-66. [https://doi.org/10.1021/acs.estlett.5b00354 doi: 10.1021/acs.estlett.5b00354]</ref> and reduced (or "charged") biochar as an electron donor for the reduction of nitrate<ref name="SaquingEtAl2016"/>. This is significant because, through microbial access of stored electrons in biochar, contaminants that do not sorb strongly to biochar can still be degraded.  
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The preparation of a conceptual site model (CSM) is a fundamental component of problem formulation and the first step in detailed sediment risk assessment. The CSM is a narrative and/or illustrative representation of the physical, chemical and biological processes that control the transport, migration and actual or potential impacts of sediment contamination to human and/or ecological receptors<ref name="NJDEP2019">New Jersey Department of Environmental Protection, 2019. Technical Guidance for Preparation and Submission of a Conceptual Site Model. Version 1.1. Site Remediation and Waste Management Program, Trenton, NJ. 46 pp. [https://www.nj.gov/dep/srp/guidance/srra/csm_tech_guidance.pdf Free download].</ref><ref name="USEPA2011">US Environmental Protection Agency, 2011. Guidance for the Development of Conceptual Models for a Problem Formulation Developed for Registration Review. Environmental Fate and Effects Division, Office of Pesticide Programs, Washington, D.C. [https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/guidance-development-conceptual-models-problem Website]</ref>. The CSM should include a “food web” because the aquatic food web is an important exposure pathway by which contaminants in the sediment reach humans and pelagic aquatic life<ref name="Arnot2004">Arnot, J.A. and Gobas, F.A., 2004. A Food Web Bioaccumulation Model for Organic Chemicals in Aquatic Ecosystems. Environmental Toxicology and Chemistry, 23(10), pp. 2343-2355. [https://doi.org/10.1897/03-438 DOI: 10.1897/03-438]</ref>.
 
  
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The CSM provides an early opportunity for critical examination of the interactions between sediment and the water column and the influence of groundwater inputs, surface runoff, and hydrodynamics. For example, there are situations where impacts in the aquatic food web can be driven by ongoing inputs to the water column from upstream sources, but mistakenly connected to polluted sediments. Other considerations included in a CSM can be socio-economic and include linkages to the ecosystem services provided by sediments<ref name="Broszeit2019">Broszeit, S., Beaumont, N.J., Hooper, T.L., Somerfield, P.J. and Austen, M.C., 2019. Developing conceptual models that link multiple ecosystem services to ecological research to aid management and policy, the UK marine example. Marine Pollution Bulletin, 141, pp.236-243.  [https://doi.org/10.1016/j.marpolbul.2019.02.051 DOI: 10.1016/j.marpolbul.2019.02.051]&nbsp;&nbsp; [https://www.sciencedirect.com/science/article/pii/S0025326X19301511/pdfft?md5=34993d6c3a57b6fb18a8b6329597fcb9&pid=1-s2.0-S0025326X19301511-main.pdf Open Access Article.]</ref><ref name="Wang2021">Wang, J., Lautz, L.S., Nolte, T.M., Posthuma, L., Koopman, K.R., Leuven, R.S. and Hendriks, A.J., 2021. Towards a systematic method for assessing the impact of chemical pollution on ecosystem services of water systems. Journal of Environmental Management, 281, p. 111873.  [https://doi.org/10.1016/j.jenvman.2020.111873 DOI: 10.1016/j.jenvman.2020.111873]&nbsp;&nbsp; [https://www.sciencedirect.com/science/article/pii/S0301479720317989/pdfft?md5=daff5e94f8aed44ffce6508afef2308c&pid=1-s2.0-S0301479720317989-main.pdf Open Access Article.]</ref>, or the social, economic and environmental impacts of sediment management alternatives. In such a case, when risk assessment seeks to compare risks of various management actions (including no action), the CSM can be termed a sustainability CSM, or SustCSM<ref name="McNally2020">McNally, A.D., Fitzpatrick, A.G., Harrison, D., Busey, A., and Apitz, S.E., 2020. Tiered approach to sustainability analysis in sediment remediation decision making. Remediation Journal, 31(1), pp. 29-44.  [https://doi.org/10.1002/rem.21661 DOI: 10.1002/rem.21661]&nbsp;&nbsp; [https://onlinelibrary.wiley.com/doi/epdf/10.1002/rem.21661 Open Access Article].</ref><ref name="Holland2011">Holland, K.S., Lewis, R.E., Tipton, K., Karnis, S., Dona, C., Petrovskis, E., and Hook, C., 2011. Framework for Integrating Sustainability Into Remediation Projects. Remediation Journal, 21(3), pp. 7-38. [https://doi.org/10.1002/rem.20288 DOI: 10.1002/rem.20288].</ref>. At a minimum, however, the purpose of the CSM is to illustrate the scope of the risk assessment and guide the quantification of exposure and risk.
+
Similar to nitrate, perchlorate and other relatively water-soluble energetic compounds (e.g., NTO and NQ) may also be similarly transformed using reduced biochar as an electron donor. Unlike other electron donors, biochar can be recharged through biodegradation of organic substrates<ref name="SaquingEtAl2016"/> and thus can serve as a long-lasting sorbent and electron repository in soil.  Similar to peat moss, the high porosity and surface area of biochar not only facilitate contaminant sorption but also create anaerobic reducing microenvironments in its inner pores, where reductive degradation of energetic compounds can take place.
  
−
===Environmental Fate===
+
===Other Sorbents===
−
An important consideration in exposure analysis is the determination of the bioavailable fraction of the contaminant in the sediment. There are two considerations. First, the adverse condition may be buried deep enough in sediments to be below the biologically available zone; typically, conditions in sediment below a depth of 5 cm will not contact burrowing benthic organisms<ref name="Anderson2010">Anderson, R.H., Prues, A.G. and Kravitz, M.J., 2010. Determination of the biologically relevant sampling depth for terrestrial ecological risk assessments. Geoderma, 154(3-4), pp.336-339. [https://doi.org/10.1016/j.geoderma.2009.11.004 DOI: 10.1016/j.geoderma.2009.11.004]</ref>. If there is no prospect for the adverse condition to come closer to the surface, then the risk assessment could conclude the risk of exposure is insignificant. The second consideration relates to chemistry and the factors involved in the binding to sediment particles or the chemical form of the substance in the sediment<ref name="Eggleton2004">Eggleton, J. and Thomas, K.V., 2004. A review of factors affecting the release and bioavailability of contaminants during sediment disturbance events. Environment International, 30(7), pp. 973-980. [https://doi.org/10.1016/j.envint.2004.03.001 DOI: 10.1016/j.envint.2004.03.001]</ref>. However, these assumptions should be examined in the context of [[Climate Change Primer | climate change]], and the likelihood of more frequent and extreme events, putting burial at risk, higher temperatures and changing biogeochemical conditions, which may alter environmental fate of contaminants, compared to historical studies.  
+
Chitin and unmodified cellulose were predicted by [[Wikipedia: Density functional theory | Density Functional Theory]] methods to be favorable for absorption of NTO and NQ, as well as the legacy explosives<ref>Todde, G., Jha, S.K., Subramanian, G., Shukla, M.K., 2018. Adsorption of TNT, DNAN, NTO, FOX7, and NQ onto Cellulose, Chitin, and Cellulose Triacetate. Insights from Density Functional Theory Calculations. Surface Science, 668, pp. 54-60. [https://doi.org/10.1016/j.susc.2017.10.004 doi: 10.1016/j.susc.2017.10.004]&nbsp;&nbsp; [[Media: ToddeEtAl2018.pdf | Open Access Manuscript.pdf]]</ref>. Cationized cellulosic materials (e.g., cotton, wood shavings) have been shown to effectively remove negatively charged energetics like perchlorate and NTO from solution<ref name="FullerEtAl2022">Fuller, M.E., Farquharson, E.M., Hedman, P.C., Chiu, P., 2022. Removal of munition constituents in stormwater runoff: Screening of native and cationized cellulosic sorbents for removal of insensitive munition constituents NTO, DNAN, and NQ, and legacy munition constituents HMX, RDX, TNT, and perchlorate. Journal of Hazardous Materials, 424(C), Article 127335. [https://doi.org/10.1016/j.jhazmat.2021.127335 doi: 10.1016/j.jhazmat.2021.127335]&nbsp;&nbsp; [[Media: FullerEtAl2022.pdf | Open Access Manuscript.pdf]]</ref>. A substantial body of work has shown that modified cellulosic biopolymers can also be effective sorbents for removing metals from solution<ref>Burba, P., Willmer, P.G., 1983. Cellulose: a biopolymeric sorbent for heavy-metal traces in waters. Talanta, 30(5), pp. 381-383. [https://doi.org/10.1016/0039-9140(83)80087-3 doi: 10.1016/0039-9140(83)80087-3]</ref><ref>Brown, P.A., Gill, S.A., Allen, S.J., 2000. Metal removal from wastewater using peat. Water Research, 34(16), pp. 3907-3916. [https://doi.org/10.1016/S0043-1354(00)00152-4 doi: 10.1016/S0043-1354(00)00152-4]</ref><ref>O’Connell, D.W., Birkinshaw, C., O’Dwyer, T.F., 2008. Heavy metal adsorbents prepared from the modification of cellulose: A review. Bioresource Technology, 99(15), pp. 6709-6724. [https://doi.org/10.1016/j.biortech.2008.01.036 doi: 10.1016/j.biortech.2008.01.036]</ref><ref>Wan Ngah, W.S., Hanafiah, M.A.K.M., 2008. Removal of heavy metal ions from wastewater by chemically modified plant wastes as adsorbents: A review. Bioresource Technology, 99(10), pp. 3935-3948. [https://doi.org/10.1016/j.biortech.2007.06.011 doi: 10.1016/j.biortech.2007.06.011]</ref> and therefore will also likely be applicable for some of the metals that may be found in surface runoff at firing ranges.
  
−
The above contaminant bioavailability considerations are important factors influencing assumptions in the risk assessment about contaminant exposure<ref name="Peijnenburg2020">Peijnenburg, W.J., 2020. Implementation of bioavailability in prospective and retrospective risk assessment of chemicals in soils and sediments. In: The Handbook of Environmental Chemistry, vol 100, Bioavailability of Organic Chemicals in Soil and Sediment, Ortega-Calvo, J.J., Parsons, J.R. (ed.s), pp.391-422. Springer.  [https://doi.org/10.1007/698_2020_516 DOI: 10.1007/698_2020_516]</ref><ref name="Ortega-Calvo2015">Ortega-Calvo, J.J., Harmsen, J., Parsons, J.R., Semple, K.T., Aitken, M.D., Ajao, C., Eadsforth, C., Galay-Burgos, M., Naidu, R., Oliver, R. and Peijnenburg, W.J., 2015. From Bioavailability Science to Regulation of Organic Chemicals. Environmental Science and Technology, 49, 10255−10264. [https://doi.org/10.1021/acs.est.5b02412 DOI: 10.1021/acs.est.5b02412]&nbsp;&nbsp; [https://pubs.acs.org/doi/pdf/10.1021/acs.est.5b02412 Open Access Article].</ref>. There have been recent advances in the use of sorbent amendments applied to contaminated sediments that alter sediment geochemistry, increase contaminant binding, and reduce contaminant exposure risks to people and the environment<ref name="Ghosh2011">Ghosh, U., Luthy, R.G., Cornelissen, G., Werner, D. and Menzie, C.A., 2011. In-situ sorbent amendments: a new direction in contaminated sediment management. Environmental Science and Technology, 45, 4, 1163–1168.  [https://doi.org/10.1021/es102694h DOI: 10.1021/es102694h]&nbsp;&nbsp; [https://pubs.acs.org/doi/pdf/10.1021/es102694h Open Access Article]</ref>. [[Passive Sampling of Sediments | Passive sampling techniques]] have emerged to quantify chemical binding to sediment and determine the freely dissolved concentration that is bioavailable.
+
==Technology Evaluation==
 +
Based on the properties of the target munition constituents, a combination of materials was expected to yield the best results to facilitate the sorption and subsequent biotic and abiotic degradation of the contaminants.
  
−
===Assessment and Measurement Endpoints===
+
===Sorbents===
−
Assessment and measurement endpoints used in sediment risk assessment are comparable to those described in USEPA ecological risk assessment guidance<ref name="USEPA2005"/><ref name="USEPA1992">US Environmental Protection Agency (USEPA), 1992. Framework for Ecological Risk Assessment, EPA/630/R-92/001. Risk Assessment Forum, Washington DC. [[Media: EPA-630-R-92-001.pdf | Report.pdf]]</ref><ref name="USEPA1996">US Environmental Protection Agency (USEPA), 1996. Eco Update: Ecological Significance and Selection of Candidate Assessment Endpoints. EPA/540/F-95/037. Office of Solid Waste and Emergency Response, Washington DC. [[Media: EPA 540-F-95-037.pdf | Report.pdf]]</ref><ref name="USEPA1997b">US Environmental Protection Agency (USEPA), 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments - Interim Final, EPA 540/R-97/006. Office of Solid Waste and Emergency Response, Washington DC. [[Media: EPA 540-R-97-006.pdf | Report.pdf]]</ref><ref name="USEPA1998">US Environmental Protection Agency (USEPA), 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Risk Assessment Forum, Washington DC. [[Media: EPA 630-R-95-002F.pdf | Report.pdf]]</ref>. A sediment risk assessment, and ecological risk assessments more broadly, must have clearly defined endpoints that are socially and biologically relevant, accessible to prediction and measurement, and susceptible to the hazard being assessed<ref name="USEPA1992"/>.
+
{| class="wikitable" style="margin-right: 30px; margin-left: auto; float:left; text-align:center;"
 +
|+Table 1. [[Wikipedia: Freundlich equation | Freundlich]] and [[Wikipedia: Langmuir adsorption model | Langmuir]] adsorption parameters for insensitive and legacy explosives
 +
|-
 +
! rowspan="2" | Compound
 +
! colspan="5" | Freundlich
 +
! colspan="5" | Langmuir
 +
|-
 +
! <small>Parameter</small> !! Peat !! <small>CAT</small> Pine !! <small>CAT</small> Burlap !! <small>CAT</small> Cotton !! <small>Parameter</small> !! Peat !! <small>CAT</small> Pine !! <small>CAT</small> Burlap !! <small>CAT</small> Cotton
 +
|-
 +
| colspan="12" style="background-color:white;" |
 +
|-
 +
! rowspan="3" | HMX
 +
! ''K<sub>f</sub>''
 +
| 0.08 +/- 0.00 || -- || -- || --
 +
! ''q<sub>m</sub>'' <small>(mg/g)</small>
 +
| 0.29 +/- 0.04 || -- || -- || --
 +
|-
 +
! ''n''
 +
| 1.70 +/- 0.18 || -- || -- || --
 +
! ''b'' <small>(L/mg)</small>
 +
| 0.39 +/- 0.09 || -- || -- || --
 +
|-
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.91 || -- || -- || --
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.93 || -- || -- || --
 +
|-
 +
| colspan="12" style="background-color:white;" |
 +
|-
 +
! rowspan="3" | RDX
 +
! ''K<sub>f</sub>''
 +
| 0.11 +/- 0.02 || -- || -- || --
 +
! ''q<sub>m</sub>'' <small>(mg/g)</small>
 +
| 0.38 +/- 0.05 || -- || -- || --
 +
|-
 +
! ''n''
 +
| 2.75 +/- 0.63 || -- || -- || --
 +
! ''b'' <small>(L/mg)</small>
 +
| 0.23 +/- 0.08 || -- || -- || --
 +
|-
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.69 || -- || -- || --
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.69 || -- || -- || --
 +
|-
 +
| colspan="12" style="background-color:white;" |
 +
|-
 +
! rowspan="3" | TNT
 +
! ''K<sub>f</sub>''
 +
| 1.21 +/- 0.15 || 1.02 +/- 0.04 || 0.36 +/- 0.02 || --
 +
! ''q<sub>m</sub>'' <small>(mg/g)</small>
 +
| 3.63 +/- 0.18 || 1.26 +/- 0.06 || -- || --
 +
|-
 +
! ''n''
 +
| 2.78 +/- 0.67 || 4.01 +/- 0.44 || 1.59 +/- 0.09 || --
 +
! ''b'' <small>(L/mg)</small>
 +
| 0.89 +/- 0.13 || 0.76 +/- 0.10 || -- || --
 +
|-  
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.81 || 0.93 || 0.98 || --
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.97 || 0.97 || -- || --
 +
|-
 +
| colspan="12" style="background-color:white;" |
 +
|-
 +
! rowspan="3" | NTO
 +
! ''K<sub>f</sub>''
 +
| -- || 0.94 +/- 0.05 || 0.41 +/- 0.05 || 0.26 +/- 0.06
 +
! ''q<sub>m</sub>'' <small>(mg/g)</small>
 +
| -- || 4.07 +/- 0.26 || 1.29 +/- 0.12 || 0.83 +/- .015
 +
|-
 +
! ''n''
 +
| -- || 1.61 +/- 0.11 || 2.43 +/- 0.41 || 2.53 +/- 0.76
 +
! ''b'' <small>(L/mg)</small>
 +
| -- || 0.30 +/- 0.04 || 0.36 +/- 0.08 || 0.30 +/- 0.15
 +
|-  
 +
! ''r<sup><small>2</small></sup>''
 +
| -- || 0.97 || 0.82 || 0.57
 +
! ''r<sup><small>2</small></sup>''
 +
| -- || 0.99 || 0.89 || 0.58
 +
|-
 +
| colspan="12" style="background-color:white;" |
 +
|-
 +
! rowspan="3" | DNAN
 +
! ''K<sub>f</sub>''
 +
| 0.38 +/- 0.05 || 0.01 +/- 0.01 || -- || --
 +
! ''q<sub>m</sub>'' <small>(mg/g)</small>
 +
| 2.57 +/- 0.33 || -- || -- || --
 +
|-
 +
! ''n''
 +
| 1.71 +/- 0.20 || 0.70 +/- 0.13 || -- || --
 +
! ''b'' <small>(L/mg)</small>
 +
| 0.13 +/- 0.03 || -- || -- || --
 +
|-  
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.89 || 0.76 || -- || --
 +
! ''r<sup><small>2</small></sup>''
 +
| 0.92 || -- || -- || --
 +
|-
 +
| colspan="12" style="background-color:white;" |
 +
|-
 +
! rowspan="3" | ClO<sub>4</sup>
 +
! ''K<sub>f</sub>''
 +
| -- || 1.54 +/- 0.06 || 0.53 +/- 0.03 || --
 +
! ''q<sub>m</sub>'' <small>(mg/g)</small>
 +
| -- || 3.63 +/- 0.18 || 1.26 +/- 0.06 || --
 +
|-
 +
! ''n''
 +
| -- || 2.42 +/- 0.16 || 2.42 +/- 0.26 || --
 +
! ''b'' <small>(L/mg)</small>
 +
| -- || 0.89 +/- 0.13 || 0.76 +/- 0.10 || --
 +
|-  
 +
! ''r<sup><small>2</small></sup>''
 +
| -- || 0.97 || 0.92 || --
 +
! ''r<sup><small>2</small></sup>''
 +
| -- || 0.97 || 0.97 || --
 +
|-
 +
| colspan="12" style="text-align:left; background-color:white;" |<small>Notes:</small><br /><big>'''--'''</big> <small>Indicates the algorithm failed to converge on the model fitting parameters, therefore there was no successful model fit.<br />'''CAT''' Indicates cationized material.</small>
 +
|}
  
−
Assessment endpoints for humans include both carcinogenic and noncarcinogenic effects. Due to their assumed higher levels of exposure, human receptors used in sediment risk assessment typically include recreational, commercial, and subsistence fishermen, i.e., people who might be at increased risk from eating fish or contacting the sediment or water on a regular basis such as indigenous peoples, immigrants from fishing cultures, and subsistence fishers who rely upon fish as a major source of protein. Special considerations are given to women of child-bearing age, pregnant women and young children. Assessment endpoints for ecological receptors focus on benthic organisms, resident fish, piscivorous and other predatory birds and marine mammals. Endpoints typically include mortality, reproductive success and population susceptibility to disease or similar adverse chronic conditions.
+
The&nbsp;materials&nbsp;screened&nbsp;included [[Wikipedia: Sphagnum | ''Sphagnum'' peat moss]], primarily for sorption of HMX, RDX, TNT, and DNAN, as well as [[Wikipedia: Cationization of cotton | cationized cellulosics]] for removal of perchlorate and NTO. The cationized cellulosics that were examined included: pine sawdust, pine shavings, aspen shavings, cotton linters (fine, silky fibers which adhere to cotton seeds after ginning), [[Wikipedia: Chitin | chitin]], [[Wikipedia: Chitosan |  chitosan]], burlap (landscaping grade), [[Wikipedia: Coir | coconut coir]], raw cotton, raw organic cotton, cleaned raw cotton, cotton fabric, and commercially cationized fabrics.
  
−
Measurement endpoints are related quantitatively to each assessment endpoint. Whenever practical, multiple measurement endpoints are chosen to provide additional lines of evidence for each assessment endpoint. For example, for humans, it might be possible to measure contaminant levels in both food items and human blood or tissue. For predatory fish, birds and mammals, it might be possible to measure contaminants in both prey and predator tissues. Measurement endpoints can be selected to assess non-chemical stressors as well, such as habitat alteration and water turbidity. Typically, measurement endpoints are compared to measurements at a reference site to ascertain the degree of departure from local natural or background conditions.
+
As shown in Table 1<ref name="FullerEtAl2022"/>, batch sorption testing indicated that a combination of Sphagnum peat moss and cationized pine shavings provided good removal of both the neutral organic energetics (HMX, RDX, TNT, DNAN) as well as the negatively charged energetics (perchlorate, NTO).
  
−
===Sediment Toxicity Testing===
+
===Slow Release Carbon Sources===
−
Sediment bioassays are an integral part of effects characterization when assessing the risks posed by contaminated sediments and developing sediment quality guidelines<ref name="USEPA2014">US Environmental Protection Agency (USEPA), 2014. Toxicity Testing and Ecological Risk Assessment Guidance for Benthic Invertebrates. Office of Chemical Safety and Pollution Prevention, Washington DC.  [https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/toxicity-testing-and-ecological-risk-assessment Website]&nbsp;&nbsp; [[Media: USEPA2014.pdf | Report.pdf]]</ref><ref name="Simpson2016a">Simpson, S., Campana, O., Ho, K., 2016. Chapter 7, Sediment Toxicity Testing. In: J. Blasco, P.M. Chapman, O. Campana, M. Hampel (ed.s), Marine Ecotoxicology: Current Knowledge and Future Issues. Academic Press Incorporated. pp. 199-237.  [https://doi.org/10.1016/B978-0-12-803371-5.00007-2 DOI: 10.1016/B978-0-12-803371-5.00007-2]</ref>. The selection of appropriate sediment bioassays is dependent on the questions being addressed, the physical and chemical characteristics of the sediment matrix, the nature of the contaminant(s) of concern, and preferences of the supervising regulatory authority for the test method and test organisms<ref name="Amiard-Triquet2015">Amiard-Triquet, C., Amiard, J.C. and Mouneyrac, C. (ed.s), 2015. Aquatic Ecotoxicology: Advancing Tools For Dealing With Emerging Risks. Academic Press, NY. ISBN #9780128009499.  [https://doi.org/10.1016/B978-0-12-800949-9.12001-7 DOI: 10.1016/B978-0-12-800949-9.12001-7]</ref>. Bioassay procedures have been standardized in several countries, and it is not unusual for different test methods to be required in different countries for the same sediment management purpose<ref name="DelValls2004">DelValls, T.A., Andres, A., Belzunce, M.J., Buceta, J.L., Casado-Martinez, M.C., Castro, R., Riba, I., Viguri, J.R. and Blasco, J., 2004. Chemical and ecotoxicological guidelines for managing disposal of dredged material. TrAC Trends in Analytical Chemistry, 23(10-11), pp. 819-828.  [https://doi.org/10.1016/j.trac.2004.07.014 DOI: 10.1016/j.trac.2004.07.014]&nbsp;&nbsp; Free download from: [https://d1wqtxts1xzle7.cloudfront.net/46085251/Chemical_and_Ecotoxicological_Guidelines20160530-23122-4fooj2-with-cover-page-v2.pdf?Expires=1637618385&Signature=aNsOfciO0HPhucL8S713nenRlvviD2dbLi8y63n93iGX~Cc7CHwyYQ2bfNlT6VnjuFJeVT83M01Xog6esr14gyvL9pmlo3hw5fQp5J9vA8gqXcT9kQfM1T2Q0Ig883yGMFmtgUrrU6p8c8V~8rh5DTKDD5ZsiL4zloGgF6Gs4F2ecEDqyFBZ17yYpXGVVBmpfm87sUpaPY0Ix9iWJ~5nxM~HF6XYl1sA1rgFSerT-Y5W8Ma7-XMljnYHQ7hW7eqMjyN66IDj7pwafG7Ox-Hnp07IuD-oMY1dHHrzTOmHpXpWgMYLn2zf1BSmy~tqIFHE6UjZn5ako93PgExuzEjEiw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA Academia.edu]</ref>. Guidance documents in Australia, Canada, Europe and the US cover the wide range of sediment bioassay procedures most often used in risk assessment<ref name="Bat2005">Bat, L., 2005. A Review of Sediment Toxicity Bioassays Using the Amphipods and Polychaetes. Turkish Journal of Fisheries and Aquatic Sciences, 5(2), pp. 119-139.  [https://dergipark.org.tr/en/pub/trjfas-ayrildi/issue/13287/160604 Free download]&nbsp;&nbsp; [[Media: Bat2005.pdf | Report.pdf]]</ref><ref name="Keddy1995">Keddy, C.J., Greene, J.C. and Bonnell, M.A., 1995. Review of Whole-Organism Bioassays: Soil, Freshwater Sediment, and Freshwater Assessment in Canada. Ecotoxicology and Environmental Safety, 30(3), pp. 221-251.  [https://doi.org/10.1006/eesa.1995.1027 DOI: 10.1006/eesa.1995.1027]</ref><ref name="Giesy1990">Giesy, J.P., Rosiu, C.J., Graney, R.L. and Henry, M.G., 1990. Benthic invertebrate bioassays with toxic sediment and pore water. Environmental Toxicology and Chemistry, 9(2), pp. 233-248.  [https://doi.org/10.1002/etc.5620090214 DOI: 10.1002/etc.5620090214]</ref><ref name="Simpson2016b">Simpson, S. and Batley, G. (ed.s), 2016. Sediment Quality Assessment: A Practical Guide, Second Edition. 358 pp. CSIRO Publishing, Australia. ISBN # 9781486303847.</ref><ref name="Moore2019">Moore, D.W., Farrar, D., Altman, S. and Bridges, T.S., 2019. Comparison of Acute and Chronic Toxicity Laboratory Bioassay Endpoints with Benthic Community Responses in Field‐Exposed Contaminated Sediments. Environmental Toxicology and Chemistry, 38(8), pp. 1784-1802.  [https://doi.org/10.1002/etc.4454 DOI: 10.1002/etc.4454]</ref>.
+
{| class="wikitable" style="margin-right: 30px; margin-left: auto; float:left; text-align:center;"
 +
|+Table 2. Slow-release Carbon Sources
 +
|-
 +
! Material !! Abbreviation !! Commercial Source !! Notes
 +
|-
 +
| polylactic acid || PLA6 || [https://www.goodfellow.com/usa?srsltid=AfmBOoqEiqIbrvWb1Hn1Bc090efBUUfg6V4N3Vrn6ytajHMJR-FG1Ez- Goodfellow] || high molecular weight thermoplastic polyester
 +
|-
 +
| polylactic acid || PLA80 || [https://www.goodfellow.com/usa?srsltid=AfmBOoqEiqIbrvWb1Hn1Bc090efBUUfg6V4N3Vrn6ytajHMJR-FG1Ez- Goodfellow] || low molecular weight thermoplastic polyester
 +
|-
 +
| polyhydroxybutyrate || PHB || [https://www.goodfellow.com/usa?srsltid=AfmBOoqEiqIbrvWb1Hn1Bc090efBUUfg6V4N3Vrn6ytajHMJR-FG1Ez- Goodfellow] || bacterial polyester
 +
|-
 +
| polycaprolactone || PCL || [https://www.sarchemlabs.com/?hsa_acc=4540346154&hsa_cam=20281343997&hsa_grp&hsa_ad&hsa_src=x&hsa_tgt&hsa_kw&hsa_mt&hsa_net=adwords&hsa_ver=3&gad_source=1&gad_campaignid=21209931835 Sarchem Labs] || biodegradable polyester
 +
|-
 +
| polybutylene succinate || BioPBS || [https://us.mitsubishi-chemical.com/company/performance-polymers/ Mitsubishi Chemical Performance Polymers] || compostable bio-based product
 +
|-
 +
| sucrose ester of fatty acids || SEFA SP10 || [https://www.sisterna.com/ Sisterna] || food and cosmetics additive
 +
|-
 +
| sucrose ester of fatty acids || SEFA SP70 || [https://www.sisterna.com/ Sisterna] || food and cosmetics additive
 +
|}
  
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In general, sediment toxicity tests focus on either (acute) lethality in whole organisms (typically benthic infaunal species such as amphipods and polychaetes) following short-term or acute exposures (<14 days) or (chronic) sublethal responses (e.g., reduced growth or reproduction or both) following longer-term exposures<ref name="Simpson2016a"/>. It is not unusual in sediment risk assessment to rely on more than one sediment bioassay. Both acute and chronic tests involving either solid-phase or pore-water sediment fractions can be useful to discern the contributions of different contaminants in whole sediment by examining the response of different endpoints in different test organisms<ref name="Keddy1995"/><ref name="Giesy1990"/>. The application of more specialized techniques such as toxicity identification evaluations (TIEs) have also proved useful to help identify contaminants or contaminant classes most likely responsible for toxicity and to exclude potentially confounding factors such as ammonia<ref name="Ho2013">Ho, K.T. and Burgess, R.M., 2013. What's causing toxicity in sediments? Results of 20 years of toxicity identification and evaluations. Environmental Toxicology and Chemistry, 32(11), pp. 2424-2432.  [https://doi.org/10.1002/etc.2359 DOI: 10.1002/etc.2359]</ref><ref name="Bailey2016">Bailey, H.C., Curran, C.A., Arth, P., Lo, B.P. and Gossett, R., 2016. Application of sediment toxicity identification evaluation techniques to a site with multiple contaminants. Environmental Toxicology and Chemistry, 35(10), pp. 2456-2465.  [https://doi.org/10.1002/etc.3488 DOI: 10.1002/etc.3488]</ref>.
+
A&nbsp;range&nbsp;of&nbsp;biopolymers&nbsp;widely used in the production of biodegradable plastics were screened for their ability to support aerobic and anoxic biodegradation of the target munition constituents. These compounds and their sources are listed in Table 2.   
  
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===Uncertainty===
+
[[File: FullerFig3.png | thumb | 400 px | Figure 3. Schematic of interactions between biochar and munitions constituents]]
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As part of the overall analysis of risk from exposure to certain sediment conditions, it is generally understood there is a moderate degree of uncertainty associated with sampling and the environmental fate of contaminants; an order of magnitude of uncertainty associated with ecological exposure and dose-response; and greater than an order of magnitude of uncertainty associated with the quantification of potential human health effects<ref name="DiGuardo2018">Di Guardo, A., Gouin, T., MacLeod, M. and Scheringer, M., 2018. Environmental fate and exposure models: advances and challenges in 21st century chemical risk assessment. Environmental Science: Processes and Impacts, 20(1), pp. 58-71. [https://doi.org/10.1039/C7EM00568G DOI: 10.1039/C7EM00568G]&nbsp;&nbsp; [https://pubs.rsc.org/en/content/articlehtml/2018/em/c7em00568g  Open access article]</ref>. The sources of uncertainty and significance to sediment risk assessment can vary widely, thereby affecting confidence in the decisions made based on risk assessment<ref name="Reckhow1994">Reckhow, K.H., 1994. Water quality simulation modeling and uncertainty analysis for risk assessment and decision making. Ecological Modelling, 72(1-2), pp.1-20. [https://doi.org/10.1016/0304-3800(94)90143-0 DOI: 10.1016/0304-3800(94)90143-0]</ref><ref name="Chapman2002">Chapman, P.M., Ho, K.T., Munns Jr, W.R., Solomon, K. and Weinstein, M.P., 2002. Issues in sediment toxicity and ecological risk assessment. Marine Pollution Bulletin, 44(4), pp. 271-278.  [https://doi.org/10.1016/S0025-326X(01)00329-0 DOI: 10.1016/S0025-326X(01)00329-0]</ref>.
+
Multiple pure bacterial strains and mixed cultures were screened for their ability to utilize the solid biopolymers as a carbon source to support energetic compound transformation and degradation. Pure strains included the aerobic RDX degrader [[Wikipedia: Rhodococcus | ''Rhodococcus'']] species DN22 (DN22 henceforth)<ref name="ColemanEtAl1998">Coleman, N.V., Nelson, D.R., Duxbury, T., 1998. Aerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) as a nitrogen source by a Rhodococcus sp., strain DN22. Soil Biology and Biochemistry, 30(8-9), pp. 1159-1167. [https://doi.org/10.1016/S0038-0717(97)00172-7 doi: 10.1016/S0038-0717(97)00172-7]</ref> and [[Wikipedia: Gordonia (bacterium)|''Gordonia'']] species KTR9 (KTR9 henceforth)<ref name="ColemanEtAl1998"/>, the anoxic RDX degrader [[Wikipedia: Pseudomonas fluorencens | ''Pseudomonas fluorencens'']] species I-C (I-C henceforth)<ref>Pak, J.W., Knoke, K.L., Noguera, D.R., Fox, B.G., Chambliss, G.H., 2000. Transformation of 2,4,6-Trinitrotoluene by Purified Xenobiotic Reductase B from Pseudomonas fluorescens I-C. Applied and Environmental Microbiology, 66(11), pp. 4742-4750. [https://doi.org/10.1128/AEM.66.11.4742-4750.2000 doi: 10.1128/AEM.66.11.4742-4750.2000]&nbsp;&nbsp; [[Media: PakEtAl2000.pdf | Open AccessArticle.pdf]]</ref><ref>Fuller, M.E., McClay, K., Hawari, J., Paquet, L., Malone, T.E., Fox, B.G., Steffan, R.J., 2009. Transformation of RDX and other energetic compounds by xenobiotic reductases XenA and XenB. Applied Microbiology and Biotechnology, 84, pp. 535-544. [https://doi.org/10.1007/s00253-009-2024-6 doi: 10.1007/s00253-009-2024-6]&nbsp;&nbsp; [[Media: FullerEtAl2009.pdf | Open Access Manuscript]]</ref>, and the aerobic NQ degrader [[Wikipedia: Pseudomonas | ''Pseudomonas extremaustralis'']] species NQ5 (NQ5 henceforth)<ref>Kim, J., Fuller, M.E., Hatzinger, P.B., Chu, K.-H., 2024. Isolation and characterization of nitroguanidine-degrading microorganisms. Science of the Total Environment, 912, Article 169184. [https://doi.org/10.1016/j.scitotenv.2023.169184 doi: 10.1016/j.scitotenv.2023.169184]</ref>. Anaerobic mixed cultures were obtained from a membrane bioreactor (MBR) degrading a mixture of six explosives (HMX, RDX, TNT, NTO, NQ, DNAN), as well as perchlorate and nitrate<ref name="FullerEtAl2023">Fuller, M.E., Hedman, P.C., Chu, K.-H., Webster, T.S., Hatzinger, P.B., 2023. Evaluation of a sequential anaerobic-aerobic membrane bioreactor system for treatment of traditional and insensitive munitions constituents. Chemosphere, 340, Article 139887. [https://doi.org/10.1016/j.chemosphere.2023.139887 doi: 10.1016/j.chemosphere.2023.139887]</ref>. The results indicated that the slow-release carbon sources [[Wikipedia: Polyhydroxybutyrate | polyhydroxybutyrate (PHB)]], [[Wikipedia: Polycaprolactone | polycaprolactone (PCL)]], and [[Wikipedia: Polybutylene succinate | polybutylene succinate (BioPBS)]] were effective for supporting the biodegradation&nbsp;of&nbsp;the&nbsp;mixture&nbsp;of&nbsp;energetics.
  
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Consequently, technical guidance in several countries encourages including a quantitative uncertainty analysis in sediment risk assessment<ref name="USEPA2005"/><ref name="Tarazona2014"/><ref name="Apitz2005a"/><ref name="Apitz2005b"/>. The aim of uncertainty analysis is to express either quantitatively or qualitatively the limitations inherent in predicting exposures and effects and, ultimately, the level of overall risk posed by sediment conditions<ref name="Batley2002">Batley, G.E., Burton, G.A., Chapman, P.M. and Forbes, V.E., 2002. Uncertainties in Sediment Quality Weight-of-Evidence (WOE) Assessments. Human and Ecological Risk Assessment, 8(7), pp. 1517-1547.  [https://doi.org/10.1080/20028091057466 DOI: 10.1080/20028091057466]</ref>. Sediment risk assessment increasingly relies on a weight-of-evidence process to improve the certainty of conclusions about whether or not impairment exists due to sediment contamination, and, if so, which stressors and biological species (or ecological responses) are of greatest concern<ref name="Burton2002">Burton, G.A., Batley, G.E., Chapman, P.M., Forbes, V.E., Smith, E.P., Reynoldson, T., Schlekat, C.E., Besten, P.J.D., Bailer, A.J., Green, A.S. and Dwyer, R.L., 2002. A Weight-of-Evidence Framework for Assessing Sediment (or Other) Contamination: Improving Certainty in the Decision-Making Process. Human and Ecological Risk Assessment, 8(7), pp. 1675-1696. [https://doi.org/10.1080/20028091056854 DOI: 10.1080/20028091056854]</ref>. Recent advancements, including the use of Bayesian networks and geographic information systems, also help capture the range of variability in both measured and predicted exposures and responses<ref name="Holsman2017">Holsman, K., Samhouri, J., Cook, G., Hazen, E., Olsen, E., Dillard, M., Kasperski, S., Gaichas, S., Kelble, C.R., Fogarty, M. and Andrews, K., 2017. An ecosystem‐based approach to marine risk assessment. Ecosystem Health and Sustainability, 3(1), p. e01256.  [https://doi.org/10.1002/ehs2.1256 DOI: 10.1002/ehs2.1256]&nbsp;&nbsp; [https://www.tandfonline.com/doi/full/10.1002/ehs2.1256 Open access article]</ref><ref name="Marcot2019">Marcot, B.G. and Penman, T.D., 2019. Advances in Bayesian network modelling: Integration of modelling technologies. Environmental Modelling and Software, 111, pp. 386-393.  [https://doi.org/10.1016/j.envsoft.2018.09.016 DOI: 10.1016/j.envsoft.2018.09.016]</ref><ref name="Men2019">Men, C., Liu, R., Wang, Q., Guo, L., Miao, Y. and Shen, Z., 2019. Uncertainty analysis in source apportionment of heavy metals in road dust based on positive matrix factorization model and geographic information system. Science of The Total Environment, 652, pp. 27-39.  [https://doi.org/10.1016/j.scitotenv.2018.10.212 DOI: 10.1016/j.scitotenv.2018.10.212]</ref>. The level of sophistication applied to the uncertainty analysis is a subjective consideration and often decided by regulatory pressures, public perceptions and the likely cost (not only economic, but also social and environmental) of mitigating or removing the contamination.
+
===Biochar===
 +
[[File: FullerFig4.png | thumb | left | 500 px | Figure 4. Composition of the columns during the sorption-biodegradation experiments]]
 +
[[File: FullerFig5.png | thumb | 500 px | Figure 5. Representative breakthrough curves of energetics during the second replication of the column sorption-biodegradation experiment]]
 +
The&nbsp;ability&nbsp;of&nbsp;biochar&nbsp;to sorb and abiotically reduce legacy and insensitive munition constituents, as well as biochar’s use as an electron donor for microbial biodegradation of energetic compounds was examined.  Batch experiments indicated that biochar was a reasonable sorbent for some of the energetics (RDX, DNAN), but could also serve as both an electron acceptor and an electron donor to facilitate abiotic (RDX, DNAN, NTO) and biotic (perchlorate) degradation (Figure 3)<ref>Xin, D., Giron, J., Fuller, M.E., Chiu, P.C., 2022. Abiotic reduction of 3-nitro-1,2,4-triazol-5-one (NTO), DNAN, and RDX by wood-derived biochars through their rechargeable electron storage capacity. Environmental Science: Processes and Impacts, 24(2), pp. 316-329. [https://doi.org/10.1039/D1EM00447F doi: 10.1039/D1EM00447F]&nbsp;&nbsp; [[Media: XinEtAl2022.pdf | Open Access Manuscript.pdf]]</ref>.
  
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==Role in Sediment Management==
+
===Sorption-Biodegradation Column Experiments===
−
Whether or not remediation of contaminated sediments is warranted depends on the magnitude of direct or indirect health risks to humans, ecological threats to aquatic biota, and the extent of risk reduction that can be achieved by removal or containment of the contamination<ref name="Kvasnicka2020">Kvasnicka, J., Burton Jr, G.A., Semrau, J. and Jolliet, O., 2020. Dredging Contaminated Sediments: Is it Worth the Risks? Environmental Toxicology and Chemistry, 39(3), pp. 515-516.  [https://setac.onlinelibrary.wiley.com/doi/pdfdirect/10.1002/etc.4679 DOI: 10.1002/etc.4679]&nbsp;&nbsp; [https://setac.onlinelibrary.wiley.com/doi/pdfdirect/10.1002/etc.4679 Open access article]</ref>. As all sediment management also introduces risk pathways, such as sediment re-suspension leading to contaminant release, possible impacts due to land, water and energy usage, and risk to workers, remedial decision-making should also consider the risks posed by the remedial process. There are two types of remediation risks inherent in sediment remediation - engineering and biological. Sediment remedy implementation risks are predominantly short-term engineering issues associated with applying the remedy such as worker and community health and safety, equipment failures, and accident rates<ref name="Wenning2006">Wenning, R.J., Sorensen, M. and Magar, V.S., 2006. Importance of Implementation and Residual Risk Analyses in Sediment Remediation. Integrated Environmental Assessment and Management, 2(1), pp. 59-65.  [https://doi.org/10.1002/ieam.5630020111 DOI: 10.1002/ieam.5630020111]&nbsp;&nbsp; [https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.5630020111 Open access article]</ref>. Sediment residual risks are predominantly longer-term changes in exposure and effects to humans, aquatic biota, and wildlife after the remedy has been implemented<ref name="Wenning2006"/>.
+
The&nbsp;selected&nbsp;materials&nbsp;and&nbsp;cultures discussed above, along with a small amount of range soil and crushed oyster shell as a slow-release pH buffering agent, were packed into columns, and a steady flow of dissolved energetics was passed through the columns. The composition of the four columns is presented in Figure 4. The influent and effluent concentrations of the energetics was monitored over time. The column experiment was performed twice.  As seen in Figure 5, there was sustained almost complete removal of RDX and ClO<sub>4</sub><sup>-</sup>, and more removal of the other energetics in the bioactive columns compared to the sorption only columns, over the course of the experiments. For reference, 100 PV is approximately equivalent to three months of operation. The higher effectiveness of sorption with biodegradation compared to sorption only is further illustrated in Figure 6, where the energetics mass removal in the bioactive columns was shown to be 2-fold (TNT) to 20-fold (RDX) higher relative to that observed in the sorption only column.  The mass removal of HMX and NQ were both over 40% higher with biochar added to the sorption with biodegradation treatment, although biochar showed little added benefit for&nbsp;removal&nbsp;of&nbsp;other&nbsp;energetics&nbsp;tested.
  
−
In addition to evaluating sediment conditions prior to remediation, sediment risk assessment can be useful to understand how the engineering risks, the contaminant exposure pathways, and which human and wildlife populations are at risk might change with different remediation options<ref name="NRC2001">National Research Council (NRC), 2001. A Risk‐Management Strategy For PCB Contaminated Sediments. Committee On Remediation Of PCB‐Contaminated Sediments, Board On Environmental Studies And Toxicology. National Academies Press, Washington DC. 452 pp. ISBN: 0-309-58873-1 [https://doi.org/10.17226/10041 DOI: 10.17226/10041]&nbsp;&nbsp; Free download from: [https://www.nap.edu/catalog/10041/a-risk-management-strategy-for-pcb-contaminated-sediments The National Academies Press]</ref>. Decision tools such as multi-criteria decision analysis (MCDA), or sustainability assessment<ref name="Apitz2018">Apitz, S.E., Fitzpatrick, A., McNally, A., Harrison, D., Coughlin, C., and Edwards, D.A., 2018. Stakeholder Value-Linked Sustainability Assessment: Evaluating Remedial Alternatives for the Portland Harbor Superfund Site, Portland, Oregon, USA. Integrated Environmental Assessment and Management, 14(1), pp. 43-62. [https://doi.org/10.1002/ieam.1998 DOI: 10.1002/ieam.1998]&nbsp;&nbsp; [https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.1998 Open access article]</ref><ref name="Fitzpatrick2018">Fitzpatrick, A., Apitz, S.E., Harrison, D., Ruffle, B., and Edwards, D.A., 2018. The Portland Harbor Superfund Site Sustainability Project: Introduction. Integrated Environmental Assessment and Management, 14(1), pp. 17-21.  [https://doi.org/10.1002/ieam.1997 DOI: 10.1002/ieam.197]&nbsp;&nbsp; [https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.1997 Open access article]</ref>, for example, incorporate elements from sediment risk assessment to support remediation decision making<ref name="Linkov2006a">Linkov, I., Satterstrom, F.K., Kiker, G., Seager, T.P., Bridges, T., Gardner, K.H., Rogers, S.H., Belluck, D.A. and Meyer, A., 2006. Multicriteria Decision Analysis: A Comprehensive Decision Approach for Management of Contaminated Sediments. Risk Analysis, 26(1), pp. 61-78.  [https://doi.org/10.1111/j.1539-6924.2006.00713.x DOI: 10.1111/j.1539-6924.2006.00713.x]&nbsp;&nbsp; Free download from: [https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1164&context=usarmyceomaha US Army Corps of Engineers]</ref>. Sediment risk assessment also plays an important role in the implementation of monitored natural recovery (MNR) as a remediation strategy<ref name="Magar2006">Magar, V.S. and Wenning, R.J., 2006. The role of monitored natural recovery in sediment remediation. Integrated Environmental Assessment and Management, 2(1), pp. 66-74.  [https://doi.org/10.1002/ieam.5630020112 DOI: 10.1002/ieam.5630020112]&nbsp;&nbsp; [https://setac.onlinelibrary.wiley.com/doi/full/10.1002/ieam.5630020112 Open access article]</ref>. Insofar as ecological recovery is affected by surface‐sediment‐contaminant concentrations, the primary recovery processes for MNR are natural sediment burial and transformation of the contaminant to less toxic forms by biological or chemical processes<ref name="Magar2009">Magar, V.S., Chadwick, D.B., Bridges, T.S., Fuchsman, P.C., Conder, J.M., Dekker, T.J., Steevens, J.A., Gustavson, K.E. and Mills, M.A., 2009. Technical Guide: Monitored Natural Recovery at Contaminated Sediment Sites. Environmental Security Technology Certification Program (ESTCP) Project ER-0622. 277 pp.  [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Sediments/In-place-Remediation/ER-200622/(language)/eng-US Website]&nbsp;&nbsp; [https://apps.dtic.mil/sti/pdfs/ADA512822.pdf Free download]</ref>.
+
===Trap and Treat Technology===
 +
[[File: FullerFig6.png | thumb | left | 400 px | Figure 6. Energetic mass removal relative to the sorption only removal during the column sorption-biodegradation experiments.  Dashed line given for reference to C1 removal = 1.]]
 +
These&nbsp;results&nbsp;provide&nbsp;a proof-of-concept for the further development of a passive and sustainable “trap-and-treat” technology for remediation of energetic compounds in stormwater runoff at military testing and training ranges.  At a given site, the stormwater runoff would need to be fully characterized with respect to key parameters (e.g., pH, major anions), and site specific treatability testing would be recommended to assure there was nothing present in the runoff that would reduce performance.  Effluent monitoring on a regular basis would also be needed (and would be likely be expected by state and local regulators) to assess performance decline over time.
  
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Since risk reduction is the long‐term goal of contaminated sediment management<ref name="Apitz2002">Apitz, S.E. and Power, E.A., 2002. From Risk Assessment to Sediment Management: An International Perspective. Journal of Soils and Sediments, 2(2), pp. 61-66.  [https://doi.org/10.1007/BF02987872 DOI: 10.1007/BF02987872]&nbsp;&nbsp; Free download from: [https://www.researchgate.net/profile/Sabine-Apitz/publication/225649107_From_risk_assessment_to_sediment_management_An_international_perspective/links/09e4150cb2df7c6331000000/From-risk-assessment-to-sediment-management-An-international-perspective.pdf ResearchGate]</ref>, predicting the rate at which contaminant exposures and risks are mitigated by sedimentation and degradation over time can be aided by including parameters in the risk assessment that calculate the rate of contaminant removal or decay in the sediment. Evaluating sediment management options in terms of risk reduction involves assessing risks under the diverse set of conditions that include the current state of the site as well as the conditions that would occur both during the implementation work and long after the work is complete and the ecosystem stabilizes<ref name="Linkov2006b">Linkov, I., Satterstrom, F.K., Kiker, G.A., Bridges, T.S., Benjamin, S.L. and Belluck, D.A., 2006. From Optimization to Adaptation: Shifting Paradigms in Environmental Management and Their Application to Remedial Decisions. Integrated Environmental Assessment and Management, 2(1), pp. 92-98.  [https://doi.org/10.1002/ieam.5630020116 DOI: 10.1002/ieam.5630020116]&nbsp;&nbsp; [https://setac.onlinelibrary.wiley.com/doi/epdf/10.1002/ieam.5630020116 Open access article]</ref><ref name="Reible2003">Reible, D., Hayes, D., Lue-Hing, C., Patterson, J., Bhowmik, N., Johnson, M. and Teal, J., 2003. Comparison of the Long-Term Risks of Removal and In Situ Management of Contaminated Sediments in the Fox River. Soil and Sediment Contamination, 12(3), pp. 325-344.  [https://doi.org/10.1080/713610975 DOI: 10.1080/713610975]</ref>.
+
The components of the technology would be predominantly peat moss and cationized pine shavings, supplemented with biochar, ground oyster shell, the biopolymer carbon sources, and the bioaugmentation cultures. The entire mix would likely be emplaced in a concrete vault at the outflow end of the stormwater runoff retention basin at the contaminated site.  The deployed treatment system would have further design elements, such as a system to trap and retain suspended solids in the runoff in order to minimize clogging the matrix. the inside of the vault would be baffled to maximize the hydraulic retention time of the contaminated runoff. The biopolymer carbon sources and oyster shell may need be refreshed periodically (perhaps yearly) to maintain performance. However, a complete removal and replacement of the base media (peat moss, CAT pine) would not be advised, as that would lead to a loss&nbsp;of&nbsp;the&nbsp;acclimated&nbsp;biomass.
  
 
==Summary==
 
==Summary==
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Effective sediment risk assessment begins with an initial scoping and planning exercise. The work proceeds to a SLRA and, if warranted, detailed risk assessment using a process comparable to ecological risk assessment. The key elements of sediment risk assessment must include a well‐designed and site‐specific CSM; a transparent and well‐thought‐out biological and chemical data collection and analysis plan; carefully selected reference sites and decision criteria; and an explicit discussion of uncertainty. If the risk assessment concludes that unacceptable risks exist, risk‐management strategies must be evaluated, selected, implemented, and their success evaluated.
+
Novel&nbsp;sorbents&nbsp;and&nbsp;slow-release carbon sources can be an effective way to promote the sorption and biodegradation of a range of legacy and insensitive munition constituents from surface runoff, and the added benefits of biochar for both sorption and biotic and abiotic degradation of these compounds was demonstrated. These results establish a foundation for a passive, sustainable surface runoff treatment technology for both active and&nbsp;inactive&nbsp;military&nbsp;ranges.
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Sediment risk assessments are designed to simulate and predict plausible interactions between contaminants or other stressors and both ecological and human receptors. The intent is to derive meaningful insights that provide conclusions that are both rational and protective, in that they err on the side of over-estimating the likely environmental risks. Although conservative assumptions should always be used early in the sediment risk assessment process, final decisions should be supported by refined, realistic estimates of risk provided by site‐specific data and sound analytical approaches. It is increasingly evident after nearly 50 years of application that sediment risk assessment is most useful when supported by a well‐designed, site‐specific, and tiered assessment process<ref name="Bridges2005">Bridges, T., Berry, W., Della Sala, S., Dorn, P., Ells, S., Gries, T., Ireland, S., Maher, E., Menzie, C., Porebski, L., and Stronkhorst, J., 2005. Chapter 6: A framework for assessing and managing risks from contaminated sediments. In: Use of sediment quality guidelines and related tools for the assessment of contaminated sediments. Wenning, Batley, Ingersoll, and Moore, editors. Society of Environmental Toxicology and Chemistry (SETAC), pp. 227–266. ISBN: 1-880611-71-6</ref>.
 
  
 
==References==
 
==References==
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==See Also==
 
==See Also==
 +
*[https://serdp-estcp.mil/projects/details/10760fd6-fb55-4515-a629-f93c555a92f0/er-1689-project-overview Fate and Transport of Colloidal Energetic Residues, SERDP Project ER-1689]
 +
*[https://serdp-estcp.mil/projects/details/20e2f05c-fd50-4fd3-8451-ba73300c7531/er-200434-project-overview In Place Soil Treatments for Prevention of Explosives Contamination, ESTCP Project ER-200434]

Latest revision as of 14:16, 30 October 2025

Remediation of Stormwater Runoff Contaminated by Munition Constituents

Past and ongoing military operations have resulted in contamination of surface soil with munition constituents (MC), which have human and environmental health impacts. These compounds can be transported off site via stormwater runoff during precipitation events. Technologies to “trap and treat” surface runoff before it enters downstream receiving bodies (e.g., streams, rivers, ponds) (see Figure 1), and which are compatible with ongoing range activities are needed. This article describes a passive and sustainable approach for effective management of munition constituents in stormwater runoff.

Related Article(s):


Contributor: Mark E. Fuller

Key Resource(s):

  • SERDP Project ER19-1106: Development of Innovative Passive and Sustainable Treatment Technologies for Energetic Compounds in Surface Runoff on Active Ranges

Background

Surface Runoff Characteristics and Treatment Approaches

Figure 1. Conceptual model of passive trap and treat approach for MC removal from stormwater runoff

During large precipitation events the rate of water deposition exceeds the rate of water infiltration, resulting in surface runoff (also called stormwater runoff). Surface characteristics including soil texture, presence of impermeable surfaces (natural and artificial), slope, and density and type of vegetation all influence the amount of surface runoff from a given land area. The use of passive systems such as retention ponds and biofiltration cells for treatment of surface runoff is well established for urban and roadway runoff. Treatment in those cases is typically achieved by directing runoff into and through a small constructed wetland, often at the outlet of a retention basin, or via filtration by directing runoff through a more highly engineered channel or vault containing the treatment materials. Filtration based technologies have proven to be effective for the removal of metals, organics, and suspended solids[1][2][3][4].

Surface Runoff on Ranges

Figure 2. Conceptual illustration of munition constituent production and transport on military ranges. Mesoscale residues are qualitatively defined as being easily visible to the naked eye (e.g., from around 50 µm to multiple cm in size) and less likely to be transported by moving water. Microscale residues are defined as <50 µm down to below 1 µm, and more likely to be entrained in, and transported by, moving water as particulates. Blue arrows represent possible water flow paths and include both dissolved and solid phase energetics. The red vertical arrow represents the predominant energetics dissolution process in close proximity to the residues due to precipitation.

Surface runoff represents a major potential mechanism through which energetics residues and related materials are transported off site from range soils to groundwater and surface water receptors (Figure 2). This process is particularly important for energetics that are water soluble (e.g., NTO and NQ) or generate soluble daughter products (e.g., DNAN and TNT). While traditional MC such as RDX and HMX have limited aqueous solubility, they also exhibit recalcitrance to degrade under most natural conditions. RDX and perchlorate are frequent groundwater contaminants on military training ranges. While actual field measurements of energetics in surface runoff are limited, laboratory experiments have been performed to predict mobile energetics contamination levels based on soil mass loadings[5][6][7][8][9]. For example, in a previous small study, MC were detected in surface runoff from an active live-fire range[10], and more recent sampling has detected MC in marsh surface water adjacent to the same installation (personal communication). Another recent report from Canada also detected RDX in both surface runoff and surface water at low part per billion levels in a survey of several military demolition sites[11]. However, overall, data regarding the MC contaminant profile of surface runoff from ranges is very limited, and the possible presence of non-energetic constituents (e.g., metals, binders, plasticizers) in runoff has not been examined. Additionally, while energetics-contaminated surface runoff is an important concern, mitigation technologies specifically for surface runoff have not yet been developed and widely deployed in the field. To effectively capture and degrade MC and associated compounds that are present in surface runoff, novel treatment media are needed to sorb a broad range of energetic materials and to transform the retained compounds through abiotic and/or microbial processes.

Surface runoff of organic and inorganic contaminants from live-fire ranges is a challenging issue for the Department of Defense (DoD). Potentially even more problematic is the fact that inputs to surface waters from large testing and training ranges typically originate from multiple sources, often encompassing hundreds of acres. No available technologies are currently considered effective for controlling non-point source energetics-laden surface runoff. While numerous technologies exist to treat collected explosives residues, contaminated soil and even groundwater, the decentralized nature and sheer volume of military range runoff have precluded the use of treatment technologies at full scale in the field.

Range Runoff Treatment Technology Components

Based on the conceptual foundation of previous research into surface water runoff treatment for other contaminants, with a goal to “trap and treat” the target compounds, the following components were selected for inclusion in the technology developed to address range runoff contaminated with energetic compounds.

Peat

Previous research demonstrated that a peat-based system provided a natural and sustainable sorptive medium for organic explosives such as HMX, RDX, and TNT, allowing much longer residence times than predicted from hydraulic loading alone[12][13][14][15][16]. Peat moss represents a bioactive environment for treatment of the target contaminants. While the majority of the microbial reactions are aerobic due to the presence of measurable dissolved oxygen in the bulk solution, anaerobic reactions (including methanogenesis) can occur in microsites within the peat. The peat-based substrate acts not only as a long term electron donor as it degrades but also acts as a strong sorbent. This is important in intermittently loaded systems in which a large initial pulse of MC can be temporarily retarded on the peat matrix and then slowly degraded as they desorb[14][16]. This increased residence time enhances the biotransformation of energetics and promotes the immobilization and further degradation of breakdown products. Abiotic degradation reactions are also likely enhanced by association with the organic-rich peat (e.g., via electron shuttling reactions of humics)[17].

Soybean Oil

Modeling has indicated that peat moss amended with crude soybean oil would significantly reduce the flux of dissolved TNT, RDX, and HMX through the vadose zone to groundwater compared to a non-treated soil (see ESTCP ER-200434). The technology was validated in field soil plots, showing a greater than 500-fold reduction in the flux of dissolved RDX from macroscale Composition B detonation residues compared to a non-treated control plot[14]. Laboratory testing and modeling indicated that the addition of soybean oil increased the biotransformation rates of RDX and HMX at least 10-fold compared to rates observed with peat moss alone[16]. Subsequent experiments also demonstrated the effectiveness of the amended peat moss material for stimulating perchlorate transformation when added to a highly contaminated soil (Fuller et al., unpublished data). These previous findings clearly demonstrate the effectiveness of peat-based materials for mitigating transport of both organic and inorganic energetic compounds through soil to groundwater.

Biochar

Recent reports have highlighted additional materials that, either alone, or in combination with electron donors such as peat moss and soybean oil, may further enhance the sorption and degradation of surface runoff contaminants, including both legacy energetics and insensitive high explosives (IHE). For instance, biochar, a type of black carbon, has been shown to not only sorb a wide range of organic and inorganic contaminants including MCs[18][19][20][21], but also to facilitate their degradation[22][23][24][25][26][27]. Depending on the source biomass and pyrolysis conditions, biochar can possess a high specific surface area (on the order of several hundred m2/g)[28][29] and hence a high sorption capacity. Biochar and other black carbon also exhibit especially high affinity for nitroaromatic compounds (NACs) including TNT and 2,4-dinitrotoluene (DNT)[30][31][32]. This is due to the strong π-π electron donor-acceptor interactions between electron-rich graphitic domains in black carbon and the electron-deficient aromatic ring of the NAC[31][32]. These characteristics make biochar a potentially effective, low cost, and sustainable sorbent for removing MC and other contaminants from surface runoff and retaining them for subsequent degradation in situ.

Furthermore, black carbon such as biochar can promote abiotic and microbial transformation reactions by facilitating electron transfer. That is, biochar is not merely a passive sorbent for contaminants, but also a redox mediator for their degradation. Biochar can promote contaminant degradation through two different mechanisms: electron conduction and electron storage[33].

First, the microscopic graphitic regions in biochar can adsorb contaminants like NACs strongly, as noted above, and also conduct reducing equivalents such as electrons and atomic hydrogen to the sorbed contaminants, thus promoting their reductive degradation. This catalytic process has been demonstrated for TNT, DNT, RDX, HMX, and nitroglycerin[34][35][36][24][26] and is expected to occur also for IHE including DNAN and NTO.

Second, biochar contains in its structure abundant redox-facile functional groups such as quinones and hydroquinones, which are known to accept and donate electrons reversibly. Depending on the biomass and pyrolysis temperature, certain biochar can possess a rechargeable electron storage capacity (i.e., reversible electron accepting and donating capacity) on the order of several millimoles e–/g[37][38][39]. This means that when "charged", biochar can provide electrons for either abiotic or biotic degradation of reducible compounds such as MC. The abiotic reduction of DNT and RDX mediated by biochar has been demonstrated[25] and similar reactions are expected to occur for DNAN and NTO as well. Recent studies have shown that the electron storage capacity of biochar is also accessible to microbes. For example, soil bacteria such as Geobacter and Shewanella species can utilize oxidized (or "discharged") biochar as an electron acceptor for the oxidation of organic substrates such as lactate and acetate[40][41] and reduced (or "charged") biochar as an electron donor for the reduction of nitrate[41]. This is significant because, through microbial access of stored electrons in biochar, contaminants that do not sorb strongly to biochar can still be degraded.

Similar to nitrate, perchlorate and other relatively water-soluble energetic compounds (e.g., NTO and NQ) may also be similarly transformed using reduced biochar as an electron donor. Unlike other electron donors, biochar can be recharged through biodegradation of organic substrates[41] and thus can serve as a long-lasting sorbent and electron repository in soil. Similar to peat moss, the high porosity and surface area of biochar not only facilitate contaminant sorption but also create anaerobic reducing microenvironments in its inner pores, where reductive degradation of energetic compounds can take place.

Other Sorbents

Chitin and unmodified cellulose were predicted by Density Functional Theory methods to be favorable for absorption of NTO and NQ, as well as the legacy explosives[42]. Cationized cellulosic materials (e.g., cotton, wood shavings) have been shown to effectively remove negatively charged energetics like perchlorate and NTO from solution[43]. A substantial body of work has shown that modified cellulosic biopolymers can also be effective sorbents for removing metals from solution[44][45][46][47] and therefore will also likely be applicable for some of the metals that may be found in surface runoff at firing ranges.

Technology Evaluation

Based on the properties of the target munition constituents, a combination of materials was expected to yield the best results to facilitate the sorption and subsequent biotic and abiotic degradation of the contaminants.

Sorbents

Table 1. Freundlich and Langmuir adsorption parameters for insensitive and legacy explosives
Compound Freundlich Langmuir
Parameter Peat CAT Pine CAT Burlap CAT Cotton Parameter Peat CAT Pine CAT Burlap CAT Cotton
HMX Kf 0.08 +/- 0.00 -- -- -- qm (mg/g) 0.29 +/- 0.04 -- -- --
n 1.70 +/- 0.18 -- -- -- b (L/mg) 0.39 +/- 0.09 -- -- --
r2 0.91 -- -- -- r2 0.93 -- -- --
RDX Kf 0.11 +/- 0.02 -- -- -- qm (mg/g) 0.38 +/- 0.05 -- -- --
n 2.75 +/- 0.63 -- -- -- b (L/mg) 0.23 +/- 0.08 -- -- --
r2 0.69 -- -- -- r2 0.69 -- -- --
TNT Kf 1.21 +/- 0.15 1.02 +/- 0.04 0.36 +/- 0.02 -- qm (mg/g) 3.63 +/- 0.18 1.26 +/- 0.06 -- --
n 2.78 +/- 0.67 4.01 +/- 0.44 1.59 +/- 0.09 -- b (L/mg) 0.89 +/- 0.13 0.76 +/- 0.10 -- --
r2 0.81 0.93 0.98 -- r2 0.97 0.97 -- --
NTO Kf -- 0.94 +/- 0.05 0.41 +/- 0.05 0.26 +/- 0.06 qm (mg/g) -- 4.07 +/- 0.26 1.29 +/- 0.12 0.83 +/- .015
n -- 1.61 +/- 0.11 2.43 +/- 0.41 2.53 +/- 0.76 b (L/mg) -- 0.30 +/- 0.04 0.36 +/- 0.08 0.30 +/- 0.15
r2 -- 0.97 0.82 0.57 r2 -- 0.99 0.89 0.58
DNAN Kf 0.38 +/- 0.05 0.01 +/- 0.01 -- -- qm (mg/g) 2.57 +/- 0.33 -- -- --
n 1.71 +/- 0.20 0.70 +/- 0.13 -- -- b (L/mg) 0.13 +/- 0.03 -- -- --
r2 0.89 0.76 -- -- r2 0.92 -- -- --
ClO4 Kf -- 1.54 +/- 0.06 0.53 +/- 0.03 -- qm (mg/g) -- 3.63 +/- 0.18 1.26 +/- 0.06 --
n -- 2.42 +/- 0.16 2.42 +/- 0.26 -- b (L/mg) -- 0.89 +/- 0.13 0.76 +/- 0.10 --
r2 -- 0.97 0.92 -- r2 -- 0.97 0.97 --
Notes:
-- Indicates the algorithm failed to converge on the model fitting parameters, therefore there was no successful model fit.
CAT Indicates cationized material.

The materials screened included Sphagnum peat moss, primarily for sorption of HMX, RDX, TNT, and DNAN, as well as cationized cellulosics for removal of perchlorate and NTO. The cationized cellulosics that were examined included: pine sawdust, pine shavings, aspen shavings, cotton linters (fine, silky fibers which adhere to cotton seeds after ginning), chitin, chitosan, burlap (landscaping grade), coconut coir, raw cotton, raw organic cotton, cleaned raw cotton, cotton fabric, and commercially cationized fabrics.

As shown in Table 1[43], batch sorption testing indicated that a combination of Sphagnum peat moss and cationized pine shavings provided good removal of both the neutral organic energetics (HMX, RDX, TNT, DNAN) as well as the negatively charged energetics (perchlorate, NTO).

Slow Release Carbon Sources

Table 2. Slow-release Carbon Sources
Material Abbreviation Commercial Source Notes
polylactic acid PLA6 Goodfellow high molecular weight thermoplastic polyester
polylactic acid PLA80 Goodfellow low molecular weight thermoplastic polyester
polyhydroxybutyrate PHB Goodfellow bacterial polyester
polycaprolactone PCL Sarchem Labs biodegradable polyester
polybutylene succinate BioPBS Mitsubishi Chemical Performance Polymers compostable bio-based product
sucrose ester of fatty acids SEFA SP10 Sisterna food and cosmetics additive
sucrose ester of fatty acids SEFA SP70 Sisterna food and cosmetics additive

A range of biopolymers widely used in the production of biodegradable plastics were screened for their ability to support aerobic and anoxic biodegradation of the target munition constituents. These compounds and their sources are listed in Table 2.

Figure 3. Schematic of interactions between biochar and munitions constituents

Multiple pure bacterial strains and mixed cultures were screened for their ability to utilize the solid biopolymers as a carbon source to support energetic compound transformation and degradation. Pure strains included the aerobic RDX degrader Rhodococcus species DN22 (DN22 henceforth)[48] and Gordonia species KTR9 (KTR9 henceforth)[48], the anoxic RDX degrader Pseudomonas fluorencens species I-C (I-C henceforth)[49][50], and the aerobic NQ degrader Pseudomonas extremaustralis species NQ5 (NQ5 henceforth)[51]. Anaerobic mixed cultures were obtained from a membrane bioreactor (MBR) degrading a mixture of six explosives (HMX, RDX, TNT, NTO, NQ, DNAN), as well as perchlorate and nitrate[52]. The results indicated that the slow-release carbon sources polyhydroxybutyrate (PHB), polycaprolactone (PCL), and polybutylene succinate (BioPBS) were effective for supporting the biodegradation of the mixture of energetics.

Biochar

Figure 4. Composition of the columns during the sorption-biodegradation experiments
Figure 5. Representative breakthrough curves of energetics during the second replication of the column sorption-biodegradation experiment

The ability of biochar to sorb and abiotically reduce legacy and insensitive munition constituents, as well as biochar’s use as an electron donor for microbial biodegradation of energetic compounds was examined. Batch experiments indicated that biochar was a reasonable sorbent for some of the energetics (RDX, DNAN), but could also serve as both an electron acceptor and an electron donor to facilitate abiotic (RDX, DNAN, NTO) and biotic (perchlorate) degradation (Figure 3)[53].

Sorption-Biodegradation Column Experiments

The selected materials and cultures discussed above, along with a small amount of range soil and crushed oyster shell as a slow-release pH buffering agent, were packed into columns, and a steady flow of dissolved energetics was passed through the columns. The composition of the four columns is presented in Figure 4. The influent and effluent concentrations of the energetics was monitored over time. The column experiment was performed twice. As seen in Figure 5, there was sustained almost complete removal of RDX and ClO4-, and more removal of the other energetics in the bioactive columns compared to the sorption only columns, over the course of the experiments. For reference, 100 PV is approximately equivalent to three months of operation. The higher effectiveness of sorption with biodegradation compared to sorption only is further illustrated in Figure 6, where the energetics mass removal in the bioactive columns was shown to be 2-fold (TNT) to 20-fold (RDX) higher relative to that observed in the sorption only column. The mass removal of HMX and NQ were both over 40% higher with biochar added to the sorption with biodegradation treatment, although biochar showed little added benefit for removal of other energetics tested.

Trap and Treat Technology

Figure 6. Energetic mass removal relative to the sorption only removal during the column sorption-biodegradation experiments. Dashed line given for reference to C1 removal = 1.

These results provide a proof-of-concept for the further development of a passive and sustainable “trap-and-treat” technology for remediation of energetic compounds in stormwater runoff at military testing and training ranges. At a given site, the stormwater runoff would need to be fully characterized with respect to key parameters (e.g., pH, major anions), and site specific treatability testing would be recommended to assure there was nothing present in the runoff that would reduce performance. Effluent monitoring on a regular basis would also be needed (and would be likely be expected by state and local regulators) to assess performance decline over time.

The components of the technology would be predominantly peat moss and cationized pine shavings, supplemented with biochar, ground oyster shell, the biopolymer carbon sources, and the bioaugmentation cultures. The entire mix would likely be emplaced in a concrete vault at the outflow end of the stormwater runoff retention basin at the contaminated site. The deployed treatment system would have further design elements, such as a system to trap and retain suspended solids in the runoff in order to minimize clogging the matrix. the inside of the vault would be baffled to maximize the hydraulic retention time of the contaminated runoff. The biopolymer carbon sources and oyster shell may need be refreshed periodically (perhaps yearly) to maintain performance. However, a complete removal and replacement of the base media (peat moss, CAT pine) would not be advised, as that would lead to a loss of the acclimated biomass.

Summary

Novel sorbents and slow-release carbon sources can be an effective way to promote the sorption and biodegradation of a range of legacy and insensitive munition constituents from surface runoff, and the added benefits of biochar for both sorption and biotic and abiotic degradation of these compounds was demonstrated. These results establish a foundation for a passive, sustainable surface runoff treatment technology for both active and inactive military ranges.

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