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==PFAS Transport and Fate==
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==''In Situ'' Toxicity Identification Evaluation (iTIE)==  
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The transport and fate of Per- and Polyfluoroalkyl Substances (PFAS) in the environment is controlled by the nature of the PFAS source, characteristics of the individual PFAS, and environmental conditions where the PFAS are present. Transport, partitioning, and transformation are the primary processes controlling PFAS fate in the environment. PFAS compounds can also be taken up by both plants and animals, and in some cases, bioaccumulate through the food chain.
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The ''in situ'' Toxicity Identification Evaluation system is a tool to incorporate into weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.
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Understanding PFAS transport and fate is necessary for evaluating the potential risk from a PFAS release and for predictions about PFAS occurrence, migration, and persistence, and about the potential vectors for exposure. This knowledge is important for site characterization, identification of potential sources of PFAS to the site, development of an appropriate conceptual site model (CSM), and selection and predicted performance of remediation strategies.  
 
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<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
  
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'''Related Article(s): '''
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'''Related Article(s):'''
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* [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
 
  
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'''Contributor(s): '''
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*[[Contaminated Sediments - Introduction]]
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Dr. Hunter Anderson and Dr. Mark L. Brusseau
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*[[Contaminated Sediment Risk Assessment]]
  
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'''Key Resource(s): '''
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'''Contributors:''' Dr. G. Allen Burton Jr., Austin Crane
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*[https://pfas-1.itrcweb.org/wp-content/uploads/2020/04/ITRC_PFAS_TechReg_April2020.pdf  Per- and Polyfluoroalkyl Substances (PFAS), PFAS-1. ITRC 2020.]<ref name="ITRC2020">Interstate Technology and Regulatory Council (ITRC), 2020. Technical/Regulatory Guidance: Per- and Polyfluoroalkyl Substances (PFAS), PFAS-1. ITRC, PFAS Team, Washington DC. [https://pfas-1.itrcweb.org/wp-content/uploads/2020/04/ITRC_PFAS_TechReg_April2020.pdf  Free Download from ITRC].&nbsp;&nbsp; [[Media: ITRC_PFAS-1.pdf | Report.pdf]]</ref>
 
  
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*[[Media: Brusseau2018manuscript.pdf | Assessing the Potential Contributions of Additional Retention Processes to PFAS Retardation in the Subsurface. Brusseau 2018 (manuscript).]]<ref name="Brusseau2018">Brusseau, M.L., 2018. Assessing the Potential Contributions of Additional Retention Processes to PFAS Retardation in the Subsurface. Science of the Total Environment, 613-614, pp. 176-185. [https://doi.org/10.1016/j.scitotenv.2017.09.065 DOI: 10.1016/j.scitotenv.2017.09.065]&nbsp;&nbsp; [[Media: Brusseau2018manuscript.pdf | Author’s Manuscript]]</ref>
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'''Key Resources:'''
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*A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites<ref name="BurtonEtAl2020">Burton, G.A., Cervi, E.C., Meyer, K., Steigmeyer, A., Verhamme, E., Daley, J., Hudson, M., Colvin, M.,  Rosen, G., 2020. A novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites. Environmental Toxicology and Chemistry, 39(9), pp. 1746-1754. [https://doi.org/10.1002/etc.4799 doi: 10.1002/etc.4799]</ref>
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*An in situ toxicity identification and evaluation water analysis system: Laboratory validation<ref name="SteigmeyerEtAl2017">Steigmeyer, A.J., Zhang, J., Daley, J.M., Zhang, X., Burton, G.A. Jr., 2017. An in situ toxicity identification and evaluation water analysis system: Laboratory validation. Environmental Toxicology and Chemistry, 36(6), pp. 1636-1643. [https://doi.org/10.1002/etc.3696 doi: 10.1002/etc.3696]</ref>
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*Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document- <ref>United States Environmental Protection Agency, 2007.  Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document, EPA/600/R-07/080. 145 pages. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1003GR1.txt Free Download]&nbsp; [[Media: EPA2007.pdf | Report.pdf]]</ref>
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*In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- <ref>In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification [https://serdp-estcp.mil/projects/details/88a8f9ba-542b-4b98-bfa4-f693435535cd/er18-1181-project-overview Project Website]&nbsp; [[Media: ER18-1181Ph.II.pdf | Final Report.pdf]]</ref>
  
 
==Introduction==
 
==Introduction==
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The transport and fate of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]] is a rapidly evolving field of science, with many questions that are not yet resolved. Much of the currently available information is based on a few well-studied PFAS compounds. However, there is a large number and variety of PFAS with a wide range of physical and chemical characteristics that affect their behavior in the environment. The transport and fate of some PFAS could differ significantly from the compounds studied to date. Nevertheless, information about the behavior of some PFAS in the environment can be ascertained from the results of currently available research.  
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In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)<ref>Norberg-King, T., Mount, D.I., Amato, J.R., Jensen, D.A., Thompson, J.A., 1992. Toxicity identification evaluation: Characterization of chronically toxic effluents: Phase I. Publication No. EPA/600/6-91/005F. U.S. Environmental Protection Agency, Office of Research and Development. [https://www.epa.gov/sites/default/files/2015-09/documents/owm0255.pdf Free Download from US EPA]&nbsp; [[Media: usepa1992.pdf | Report.pdf]]</ref>, can be confounded by sample manipulation artifacts and temporal limitations of ''ex situ'' organism exposures<ref name="BurtonEtAl2020"/>. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The ''in situ'' Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.
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The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods<ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part I: Laboratory validation. Environmental Toxicology and Chemistry, 23(12), pp. 2844-2850. [https://doi.org/10.1897/03-409.1 doi: 10.1897/03-409.1]</ref><ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part II: Field validation. Environmental Toxicology and Chemistry, 23(12), pp. 2851-2855. [https://doi.org/10.1897/03-468.1 doi: 10.1897/03-468.1]</ref><ref name="BurtonEtAl2020"/><ref name="SteigmeyerEtAl2017"/>. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, [[Metal and Metalloid Contaminants | metals]], pesticides, polychlorinated biphenyls (PCB), [[Polycyclic Aromatic Hydrocarbons (PAHs) | polycyclic aromatic hydrocarbons (PAH)]], and [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression<ref name="BurtonEtAl2020"/>.
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==System Components and Validation==
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[[File: CraneFig1.png | thumb | 600 px | Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.]]
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The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water ''in situ''. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.
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===Porewater and Surface Water Collection Sub-system===
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[[File: CraneFig2.png | thumb | 600 px | Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver]]
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Given&nbsp;the&nbsp;importance&nbsp;of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies<ref>Chadwick, D.B., Harre, B., Smith, C.F., Groves, J.G., Paulsen, R.J., 2003. Coastal Contaminant Migration Monitoring: The Trident Probe and UltraSeep System. Hardware Description, Protocols, and Procedures. Technical Report 1902. Space and Naval Warfare Systems Center.</ref>. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.  
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The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.
  
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PFAS transport and fate in the environment is controlled by the nature of the PFAS source, characteristics of the individual PFAS, and environmental conditions where the PFAS are present.  Perfluoroalkyl acids (PFAAs) (see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature) are strong acids and are anionic in the environmentally-relevant pH range.  They are extremely persistent in the environment and do not degrade or transform under typical environmental conditions. Polyfluoroalkyl substances (see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] for nomenclature) include compounds that have the potential to degrade to PFAAs. These compounds are commonly referred to as PFAA precursors or just ‘precursors’.  Because some polyfluoroalkyl substances can degrade into PFAA via biotic or abiotic degradation pathways, PFAAs are sometimes referred to as “terminal PFAS” or “terminal degradation products”.
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Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.
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The most important molecular properties controlling PFAA transport are the carbon chain length and functional moieties of the headgroups (e.g., sulfonate, carboxylate). The molecular properties of PFAA precursors are more varied, with different carbon chain lengths, headgroups and ionic states<ref name="Buck2011">Buck, R.C., Franklin, J., Berger, U., Conder, J.M., Cousins, I.T., de Voogt, P., Jensen, A.A., Kannan, K., Mabury, S.A., and van Leeuwen, S.P.J., 2011. Perfluoroalkyl and Polyfluoroalkyl Substances in the Environment: Terminology, Classification, and Origins. Integrated Environmental Assessment and Management, 7(4): pp. 513-541.  [ https://doi.org/10.1002/ieam.258  DOI: 10.1002/ieam.258]&nbsp;&nbsp; [https://setac.onlinelibrary.wiley.com/doi/epdf/10.1002/ieam.258 Open Access Article]</ref><ref name="Wang2017">Wang, Z., DeWitt, J.C., Higgins, C.P., and Cousins, I.T., 2017. A Never-Ending Story of Per- and Polyfluoroalkyl Substances (PFASs)? Environmental Science and Technology, 51(5), pp. 2508-2518. American Chemical Society.  [https://doi.org/10.1021/acs.est.6b04806 DOI: 10.1021/acs.est.6b04806]&nbsp;&nbsp; [https://pubs.acs.org/doi/pdf/10.1021/acs.est.6b04806 Free Download from ACS]</ref> (see [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]]). All of these properties can influence transport and fate of PFAA precursors in the environment.  
 
  
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Important environmental characteristics include the nature of the source (mode of input into the environment), the length of time that the source was active, and the magnitude of the input, as well as precipitation and infiltration rates, depth to groundwater, surface water and groundwater flow rates and interactions, prevailing atmospheric conditions, the properties of the porous-media (e.g., soil and sediment) and aqueous solution, microbiological factors, and the presence of additional fluid phases such as air and non-aqueous phase liquids [[Wikipedia: Non-aqueous phase liquid | (NAPLs)]] in the vadose zone and water-saturated source. In the subsurface, soil characteristics (texture, organic carbon content, clay mineralogy, metal-oxide content, solid surface area, surface charge, and exchange capacity) and solution characteristics (pH, redox potential, major ion chemistry, and co-contaminants) can influence PFAS transport and fate.  
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===Oxygen Coil, Overflow Bag and Drip Chamber===
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[[File: CraneFig3.png | thumb | left | 400 px | Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.]]
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Porewater&nbsp;is&nbsp;naturally&nbsp;anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.
  
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==PFAS Transport and Fate Processes==
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Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.
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[[File:AndersonBrusseau1w2Fig1.png | thumb | 400px | Figure 1. Illustration of PFAS partitioning and transformation processes. Source: D. Adamson, GSI, used with permission.]]
 
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Transport, partitioning, and transformation are the primary processes controlling PFAS fate in the environment (Figure 1). PFAS compounds can also be taken up by both plants and animals, and in some cases, bioaccumulate through the food chain.  However, PFAS uptake and bioaccumulation is not discussed in this article (see “Environmental Concern” section of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]).
 
  
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* '''Transport:''' PFAS can be transported substantial distances in the atmosphere<ref name="Ahrens2012">Ahrens, L., Harner, T., Shoeib, M., Lane, D.A. and Murphy, J.G., 2012. Improved Characterization of Gas–Particle Partitioning for Per- and Polyfluoroalkyl Substances in the Atmosphere Using Annular Diffusion Denuder Samplers. Environmental Science and Technology, 46(13), pp. 7199-7206. [https://doi.org/10.1021/es300898s DOI: 10.1021/es300898s]&nbsp;&nbsp; Free download available from [https://www.researchgate.net/profile/Tom_Harner/publication/225046057_Improved_Characterization_of_Gas-Particle_Partitioning_for_Per-_and_Polyfluoroalkyl_Substances_in_the_Atmosphere_Using_Annular_Diffusion_Denuder_Samplers/links/5cc730c4299bf12097893fdc/Improved-Characterization-of-Gas-Particle-Partitioning-for-Per-and-Polyfluoroalkyl-Substances-in-the-Atmosphere-Using-Annular-Diffusion-Denuder-Samplers.pdf ResearchGate].</ref>, surface water<ref name="Taniyasu2013">Taniyasu, S., Yamashita, N., Moon, H.B., Kwok, K.Y., Lam, P.K., Horii, Y., Petrick, G. and Kannan, K., 2013.  Does wet precipitation represent local and regional atmospheric transportation by perfluorinated alkyl substances? Environment International, 55, pp. 25-32. [https://doi.org/10.1016/j.envint.2013.02.005 DOI: 10.1016/j.envint.2013.02.005]</ref>, soil<ref name="Braunig2017">Bräunig, J., Baduel, C., Heffernan, A., Rotander, A., Donaldson, E. and Mueller, J.F., 2017. Fate and redistribution of perfluoroalkyl acids through AFFF-impacted groundwater. Science of the Total Environment, 596, pp. 360-368. [https://doi.org/10.1016/j.scitotenv.2017.04.095 DOI: 10.1016/j.scitotenv.2017.04.095]</ref>, and groundwater<ref name="Weber2017">Weber, A.K., Barber, L.B., LeBlanc, D.R., Sunderland, E.M. and Vecitis, C.D., 2017. Geochemical and Hydrologic Factors Controlling Subsurface Transport of Poly- and Perfluoroalkyl Substances, Cape Cod, Massachusetts. Environmental Science and Technology, 51(8), pp. 4269-4279. [https://doi.org/10.1021/acs.est.6b05573 DOI: 10.1021/acs.est.6b05573]&nbsp;&nbsp; [https://bgc.seas.harvard.edu/assets/weber2017_final.pdf Free Download]</ref>. The primary mechanisms controlling PFAS transport are [[Wikipedia:Advection | advection]] and [[Wikipedia:Dispersive_mass_transfer | dispersion]], similar to other dissolved compounds. For additional information on transport in groundwater, see [[Advection and Groundwater Flow]] and [[Dispersion and Diffusion]].
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===iTIE Units: Fractionation and Organism Exposure Chambers===
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[[File: CraneFig4.png | thumb | 300px | Figure 4. A diagram of the iTIE prototype. Water flows upward into each resin chamber through the unit bottom. After being chemically fractionated in the resin chamber, water travels into the organism chamber, where test organisms have been placed. Water is drawn through the units by high-precision peristaltic pumps.]]
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At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton ''et al.''<ref name="BurtonEtAl2020"/>, the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an in situ exposure. Currently, the iTIE system can support four independent iTIE treatment units.
  
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* '''Partitioning:''' Partitioning of PFAS between the mobile and immobile phases is one of the most important processes controlling the rate of migration in the environment. The primary mobile phases are typically air and water.  Relatively immobile phases include stream sediments, soils, aquifer material, NAPLs, and interfaces between different phases (air-water, NAPL-water).  Partitioning of a significant portion of the PFAS mass into an immobile phase increases the amount of material stored in the system and slows the apparent rate of migration in the mobile phase – a phenomenon that has been observed in field metadata<ref name="Anderson2019">Anderson, R.H., Adamson, D.T. and Stroo, H.F., 2019. Partitioning of poly-and perfluoroalkyl substances from soil to groundwater within aqueous film-forming foam source zones. Journal of Contaminant Hydrology, 220, pp. 59-65. [https://doi.org/10.1016/j.jconhyd.2018.11.011 DOI: 10.1016/j.jconhyd.2018.11.011]&nbsp;&nbsp; Manuscript available from [https://www.researchgate.net/profile/Hans_Stroo3/publication/329227107_Partitioning_of_poly-_and_perfluoroalkyl_substances_from_soil_to_groundwater_WITHIN_aqueous_film-forming_foam_source_zones/links/5e56996b299bf1bdb83e2f69/Partitioning-of-poly-and-perfluoroalkyl-substances-from-soil-to-groundwater-WITHIN-aqueous-film-forming-foam-source-zones.pdf ResearchGate]</ref>.
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After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.
  
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* '''Transformation:''' Transformation of PFAS is controlled by the molecular structure of the individual compounds.  Perfluorinated compounds, including PFAAs, are resistant to abiotic and biotic transformation reactions under typical conditions and highly persistent in the environment.  In contrast, precursors can be transformed by both abiotic and biotic processes, often resulting in the production of so-called “terminal” PFAA daughter products.
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===Pumping Sub-system===
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[[File: CraneFig5.png | thumb | 300px | Figure 5. The iTIE system pumping sub-system. The sub-system consists of: A) a single booster pump, which is directly connected to the water sampling device and feeds water to the rest of the iTIE system, and B) a set of four regulation pumps, which each connect to the outflow of an individual iTIE unit. Each pump set is housed in a waterproof case with self-contained rechargeable battery power. A tablet is mounted inside the lid of the four pump case, which can be used to program and operate all of the pumps when connected to the internet.]]
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Water movement through the system is driven by a series of high-precision, programmable peristaltic pumps ([https://ecotechmarine.com/ EcoTech Marine]). Each pump set is housed in a Pelican storm travel case. Power is supplied to each pump by internal rechargeable lithium-iron phosphate batteries ([https://www.bioennopower.com/ Bioenno Power]).
  
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==Transport and Partitioning in the Atmosphere==
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First, water is supplied to the system by a booster pump (Figure 5A). This pump is situated between the water sampling sub-system and the oxygen coil. The booster pump: 1) facilitates pore water collection, especially from sediments with high fine particle fractions; 2) helps water overcome vertical lifts to travel to the iTIE system; and 3) prevents vacuums from forming in the iTIE system interior, which can accelerate the formation of disruptive gas bubbles in the oxygen coil. The booster pump should be programmed to supply an excess of water to prevent vacuum formation.
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Air serves as a transport media for PFAS, particularly for uncharged polyfluorinated PFAS.  Airborne PFAS transport contributes to global distribution and can lead to localized deposition to soils and surface water in the vicinity of emission sources<ref name="Simcik2005">Simcik, M.F. and Dorweiler, K.J., 2005. Ratio of Perfluorochemical Concentrations as a Tracer of Atmospheric Deposition to Surface Waters. Environmental Science and Technology, 39(22), pp. 8678-8683. [https://doi.org/10.1021/es0511218 DOI: 10.1021/es0511218]&nbsp;&nbsp; Free download available from [https://www.researchgate.net/profile/Matt_Simcik/publication/7444956_Ratio_of_Perfluorochemical_Concentrations_as_a_Tracer_of_Atmospheric_Deposition_to_Surface_Waters/links/5f035861299bf1881603c3be/Ratio-of-Perfluorochemical-Concentrations-as-a-Tracer-of-Atmospheric-Deposition-to-Surface-Waters.pdf ResearchGate]</ref><ref name="Prevedouros2006">Prevedouros, K., Cousins, I.T., Buck, R.C. and Korzeniowski, S.H., 2006. Sources, Fate and Transport of Perfluorocarboxylates. Environmental Science and Technology, 40(1), pp. 32-44. [https://doi.org/10.1021/es0512475 DOI: 10.1021/es0512475]&nbsp;&nbsp; Free download available from [https://d1wqtxts1xzle7.cloudfront.net/39945519/Sources_Fate_and_Transport_of_Perfluoroc20151112-1647-19vcvbf.pdf?1447365456=&response-content-disposition=inline%3B+filename%3DSources_Fate_and_Transport_of_Perfluoroc.pdf&Expires=1605023809&Signature=Z6KqgaDN6lKdAazoe6qoASoCtVystG5i~5EnrTcb~qMg3xZPz4O49Kghh62WmMzqEKE788~6EwrnlBVo9o6cM0hjf2vymFYxg4mx-eSIOEonfFjk6RonSaWp5gRbA6m~SNjwsjaKXID3OQyWIlLVpUd2LzAdI5rLGFA~gIXXtNPyCArLuGn-kbPYUIcBUg5TIkTZ6TDLXF~ujmzK9tNv~55UYabsJL4pmwIGC2sNGkEyJrYMfU577fbactdrmQXTJH7XbgpfDSfd4-xWkDZTdvVf~TypDDqUCZdtCkY8wINdpqtfe1KEzLrAj7rxxALAHUYxlVbPB45XTkLAGe5qww__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA  Academia]</ref><ref name="Ahrens2011">Ahrens, L., Shoeib, M., Harner, T., Lane, D.A., Guo, R. and Reiner, E.J., 2011. Comparison of Annular Diffusion Denuder and High Volume Air Samplers for Measuring Per- and Polyfluoroalkyl Substances in the Atmosphere." Analytical Chemistry, 83(24), pp. 9622-9628. [https://doi.org/10.1021/ac202414w DOI: 10.1021/ac202414w]&nbsp;&nbsp; Free download available from [https://www.informea.org/sites/default/files/imported-documents/UNEP-POPS-POPRC11FU-SUBM-PFOA-Canada-2-20151211.En.pdf Informea].</ref><ref name="Rauert2018">Rauert, C., Shoieb, M., Schuster, J.K., Eng, A. and Harner, T., 2018. Atmospheric concentrations and trends of poly-and perfluoroalkyl substances (PFAS) and volatile methyl siloxanes (VMS) over 7 years of sampling in the Global Atmospheric Passive Sampling (GAPS) network. Environmental Pollution, 238, pp. 94-102. [https://doi.org/10.1016/j.envpol.2018.03.017 DOI: 10.1016/j.envpol.2018.03.017]&nbsp;&nbsp; Open access article available from [https://reader.elsevier.com/reader/sd/pii/S0269749117352521?token=4C770E6E8AEDB0B3BA6A1D5B2C20ED5385F81823612551FA3380AAA1DA7A978F9CB36834AF6B7F91F35FF57E32013252 ScienceDirect]&nbsp;&nbsp; [[Media:Rauert2018.pdf | Report.pdf]]</ref>.  
 
  
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PFAAs, which are ionic and possess a negative charge under ambient environmental conditions, are far less volatile than many other groundwater contaminants.  An online database of vapor pressures and Henry’s Law constants for different PFAS, including PFAAs, is maintained by the Interstate Technology Regulatory Council<ref name="ITRC2020"/>.  In general, vapor pressures of PFAS are low and water solubilities are high, limiting partitioning from water to air<ref name="ITRC2020"/>.  However, under certain conditions, particularly within industrial stack emissions, PFAS can be transported through the atmosphere in both the gas phase and associated with fugitive particulates.  In particular, volatile compounds including fluorotelomer alcohols (FTOHs) may be present in the gas phase, whereas, PFAAs can aerosolize and be transported as particulates<ref name="Ahrens2012"/>. In addition, precursors can be transformed to PFAAs in the atmosphere, which can result in PFAA deposition.
+
Second, a set of four regulation pumps ensure precise flow rates through each independent iTIE unit (Figure 5B). Each regulation pump pulls water from the top of an iTIE unit and then dispenses that water into a sample bottle for further analysis.
−
Short-range atmospheric transport and deposition can result in PFAS contamination in terrestrial and aquatic systems near points of significant emissions, impacting soil, groundwater, and other media of concern<ref name="Fang2018">Fang, X., Wang, Q., Zhao, Z., Tang, J., Tian, C., Yao, Y., Yu, J. and Sun, H., 2018. Distribution and dry deposition of alternative and legacy perfluoroalkyl and polyfluoroalkyl substances in the air above the Bohai and Yellow Seas, China. Atmospheric Environment, 192, pp. 128-135. [https://doi.org/10.1016/j.atmosenv.2018.08.052 DOI: 10.1016/j.atmosenv.2018.08.052]</ref><ref name="Brandsma2019">Brandsma, S.H., Koekkoek, J.C., van Velzen, M.J.M. and de Boer, J., 2019.  The PFOA substitute GenX detected in the environment near a fluoropolymer manufacturing plant in the Netherlands. Chemosphere, 220, pp. 493-500. [https://doi.org/10.1016/j.chemosphere.2018.12.135 DOI: 10.1016/j.chemosphere.2018.12.135]&nbsp;&nbsp; Open access article available from [https://reader.elsevier.com/reader/sd/pii/S0045653518324706?token=E541D5C4B200C8626A86F41049FE9DCA92652BC9A8BA7D9E47832C08070AB5AF256F4872474C50B5C4908F5CA4C24947 ScienceDirect].&nbsp;&nbsp; [[Media: Brandsma2019.pdf | Report.pdf]]</ref>.  Releases of ionic PFAS from factories are likely tied to particulate matter, which settle to the ground in dry weather and are also wet-scavenged by precipitation<ref name="Barton2006">Barton, C.A., Butler, L.E., Zarzecki, C.J., Flaherty, J. and Kaiser, M., 2006. Characterizing Perfluorooctanoate in Ambient Air near the Fence Line of a Manufacturing Facility: Comparing Modeled and Monitored Values. Journal of the Air and Waste Management Association, 56(1), pp.  48-55. [https://doi.org/10.1080/10473289.2006.10464429 DOI: 10.1080/10473289.2006.10464429]&nbsp;&nbsp; Free access article available from [https://www.tandfonline.com/doi/pdf/10.1080/10473289.2006.10464429?needAccess=true Taylor and Francis Online]&nbsp;&nbsp; [[Media: Barton2006.pdf | Report.pdf]]</ref>.  The impact of other potential sources, such as combustion emissions or wind-blown fire-fighting foam from fire training and fire response sites, on the fate and transport of PFAS in air may need to be assessed.
 
  
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Long-range transport processes are responsible for the wide distribution of neutral and ionic PFAS across the Earth as evidenced by their occurrence in biota, surface snow, ice cores, seawater, and other environmental media in regions as remote as the Arctic and Antarctic<ref name="Bossi2016">Bossi, R., Vorkamp, K. and Skov, H., 2016. Concentrations of organochlorine pesticides, polybrominated diphenyl ethers and perfluorinated compounds in the atmosphere of North Greenland. Environmental Pollution, 217, pp. 4-10. [https://doi.org/10.1016/j.envpol.2015.12.026 DOI: 10.1016/j.envpol.2015.12.026]</ref><ref name="Ahrens2010">Ahrens, L., Gerwinski, W., Theobald, N. and Ebinghaus, R., 2010. Sources of polyfluoroalkyl compounds in the North Sea, Baltic Sea and Norwegian Sea: Evidence from their spatial distribution in surface water. Marine Pollution Bulletin, 60(2), pp. 255-260. [https://doi.org/10.1016/j.marpolbul.2009.09.013 DOI: 10.1016/j.marpolbul.2009.09.013]</ref>.
+
==Study Design Considerations==
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Distribution of PFAS to remote regions far removed from direct industrial input is believed to occur from both: a) long-range atmospheric transport and subsequent degradation of volatile precursors; and b) transport via ocean currents and release into the air as marine aerosols (sea spray)<ref name="DeSilva2009">De Silva, A.O., Muir, D.C. and Mabury, S.A., 2009. Distribution of perfluorocarboxylate isomers in select samples from the North American environment. Environmental Toxicology and Chemistry: An International Journal 28(9), pp. 1801-1814. [https://doi.org/10.1897/08-500.1 DOI: 10.1897/08-500.1]</ref><ref name="Armitage2009">Armitage, J.M., 2009. Modeling the global fate and transport of perfluoroalkylated substances (PFAS). Doctoral Dissertation, Institutionen för tillämpad miljövetenskap (ITM), Stockholm University. [[Media: Armitage2009.pdf | Report.pdf]]</ref>.
+
===Diagnostic Resin Treatments===
 +
Several commercially available resins have been verified for use in the iTIE system. Investigators can select resins based on stressor classes of interest at each site. Each resin selectively removes a CoC class from site water prior to organism exposure.
 +
*[https://www.dupont.com/products/ambersorb560.html DuPont Ambersorb 560] for removal of 1,4-dioxane and other organic chemicals<ref>Woodard, S., Mohr, T., Nickelsen, M.G., 2014. Synthetic media: A promising new treatment technology for 1,4-dioxane. Remediation Journal, 24(4), pp. 27-40. [https://doi.org/10.1002/rem.21402 doi: 10.1002/rem.21402]</ref>
 +
*C18 for nonpolar organic chemicals
 +
*[https://www.bio-rad.com/en-us Bio-Rad] [https://www.bio-rad.com/en-us/product/chelex-100-resin?ID=6448ab3e-b96a-4162-9124-7b7d2330288e Chelex] for metals
 +
*Granular activated carbon for metals, general organic chemicals, sulfide<ref>Lemos, B.R.S., Teixeira, I.F., de Mesquita, J.P., Ribeiro, R.R., Donnici, C.L., Lago, R.M., 2012. Use of modified activated carbon for the oxidation of aqueous sulfide. Carbon, 50(3), pp. 1386-1393. [https://doi.org/10.1016/j.carbon.2011.11.011 doi: 10.1016/j.carbon.2011.11.011]</ref>
 +
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=Shop&isocode=en_US&keyword=oasis%20hlb&multiselect=true&page=1&rows=12&sort=best-sellers&xcid=ppc-ppc_23916&gad_source=1&gad_campaignid=14746094146&gbraid=0AAAAAD_uR00nhlNwrhhegNh06pBODTgiN&gclid=CjwKCAiAtLvMBhB_EiwA1u6_PsppE0raci2IhvGnAAe5ijciNcetLaGZo5qA3g3r4Z_La7YAPJtzShoC6LoQAvD_BwE Oasis HLB] for general organic chemicals<ref name="SteigmeyerEtAl2017"/>
 +
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=All&enableHL=true&isocode=en_US&keyword=Oasis%20WAX%20&multiselect=true&page=1&rows=12&sort=most-relevant Oasis WAX] for PFAS, organic chemicals of mixed polarity<ref>Iannone, A., Carriera, F., Di Fiore, C., Avino, P., 2024. Poly- and Perfluoroalkyl Substance (PFAS) Analysis in Environmental Matrices: An Overview of the Extraction and Chromatographic Detection Methods. Analytica, 5(2), pp. 187-202. [https://doi.org/10.3390/analytica5020012 doi: 10.3390/analytica5020012]&nbsp; [[Media: IannoneEtAl2024.pdf | Open Access Article]]</ref>
 +
*Zeolite for ammonia, other organic chemicals
  
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==Transport and Partitioning in Aqueous Systems==
+
Resins must be adequately conditioned prior to use. Otherwise, they may inadequately adsorb toxicants or cause stress to organisms. New resins should be tested for efficacy and toxicity before being used in an iTIE system.  
−
PFAS adsorb from water to a variety of solid materials including organic materials, clay minerals, metal oxides, and granular activated carbon<ref name="Du2014">Du, Z., Deng, S., Bei, Y., Huang, Q., Wang, B., Huang, J. and Yu, G., 2014. Adsorption behavior and mechanism of perfluorinated compounds on various adsorbents – A review. Journal of Hazardous Materials, 274, pp. 443-454. [https://doi.org/10.1016/j.jhazmat.2014.04.038 DOI: 10.1016/j.jhazmat.2014.04.038]</ref>.  This process is thought to occur through two primary mechanisms: 1) sorption to organic-carbon components of the solids; and 2) electrostatic (and other) interactions with inorganic constituents of the solids, including clay minerals and metal-oxides<ref name="Guelfo2013">Guelfo, J.L. and Higgins, C.P., 2013. Subsurface Transport Potential of Perfluoroalkyl Acids at Aqueous Film-Forming Foam (AFFF)-Impacted Sites. Environmental Science and Technology, 47(9), pp. 4164-4171. [https://doi.org/10.1021/es3048043 DOI: 10.1021/es3048043]&nbsp;&nbsp; [https://mountainscholar.org/bitstream/handle/11124/80055/Guelfo_mines_0052E_10298.pdf?sequence=1#page=64 Doctoral Dissertation]</ref><ref name="Zhao2014">Zhao, L., Bian, J., Zhang, Y., Zhu, L. and Liu, Z., 2014. Comparison of the sorption behaviors and mechanisms of perfluorosulfonates and perfluorocarboxylic acids on three kinds of clay minerals. Chemosphere, 114, pp. 51-58. [https://doi.org/10.1016/j.chemosphere.2014.03.098 DOI: 10.1016/j.chemosphere.2014.03.098]&nbsp;&nbsp; Free download available from [https://www.researchgate.net/profile/Lixia_Zhao8/publication/262148355_Comparison_of_the_sorption_behaviors_and_mechanisms_of_perfluorosulfonates_and_perfluorocarboxylic_acids_on_three_kinds_of_clay_minerals/links/5b1be5dca6fdcca67b681a4f/Comparison-of-the-sorption-behaviors-and-mechanisms-of-perfluorosulfonates-and-perfluorocarboxylic-acids-on-three-kinds-of-clay-minerals.pdf ResearchGate].</ref>.  The relative contribution of each mechanism varies depending on surface chemistry and other geochemical factors, as well as the molecular properties of the PFAS.  In general, the impact of electrostatic interactions with charged soil constituents is more important for PFAS than non-polar, hydrophobic organic contaminants (e.g. hydrocarbons, chlorinated solvents).  Adsorption of PFAS by solids is often nonlinear, with greater sorption at lower solute concentrations.  The impacts of adsorption kinetics and their potential reversibility on PFAS transport have not yet been examined for most PFAS compounds.
 
  
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Sorption of hydrocarbons, chlorinated solvents and other hydrophobic organics is often controlled the by organic-carbon components of the solid phase (see [[Sorption of Organic Contaminants]]).  However, studies of PFAS sorption to solid phase organic carbon have reported conflicting results.  In a study of field sites with aqueous film-forming foam (AFFF, a type of fire-fighting foam) releases, solid phase organic carbon content was found to significantly influence PFAS soil-to-groundwater concentration ratios.  Statistical modeling was then used to derive apparent organic carbon partition coefficients for 18 different PFAS<ref name="Anderson2019"/>.  A recent compilation of published organic carbon partition coefficients found a good correspondence to PFAS molecular structure<ref name="Brusseau2019a">Brusseau, M.L., 2019. Estimating the relative magnitudes of adsorption to solid-water and air/oil-water interfaces for per-and poly-fluoroalkyl substances. Environmental Pollution, 254B, p. 113102. [https://doi.org/10.1016/j.envpol.2019.113102 DOI: 10.1016/j.envpol.2019.113102]</ref>. However, other studies have shown a general lack of correlation between solid phase partition coefficients and organic carbon<ref name="Li2018">Li, Y., Oliver, D.P. and Kookana, R.S., 2018. A critical analysis of published data to discern the role of soil and sediment properties in determining sorption of per and polyfluoroalkyl substances (PFASs). Science of the Total Environment, 628, pp. 110-120. [https://doi.org/10.1016/j.scitotenv.2018.01.167 DOI: 10.1016/j.scitotenv.2018.01.167]</ref>. It is possible that greater variability may be observed for broader data sets that incorporate different ranges of PFAS concentrations, different solution conditions, different measurement methods, and field-based data which often have less well-defined conditions and may also be influenced by other retention processes<ref name="Anderson2019"/><ref name="Brusseau2019a"/>.
+
===Test Organism Species and Life Stages===
  
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[[File:AndersonBrusseau1w2Fig2.png | thumb | 400px | Figure 2. Example of expected orientation and accumulation of PFAS at air-water interface. Source: D. Adamson, GSI, used with permission.]]
 
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Most solids present in the environment contain both fixed-charged (negative) and variably charged surfaces.  At neutral to high pH, variably charged clay minerals have a net-negative charge.  As a result, negatively charged PFAAs do not strongly interact electrostatically in most soils, although as the soil pH decreases electrostatic sorption would be expected to increase in soils with variably charged clay minerals.  Cationic and zwitterionic precursors are expected to be more strongly sorbed than anionic PFAAs in most environments due to well-established cation exchange reactions. Other factors, including ionic strength, composition, and the presence of co-solutes, can affect adsorption of PFAS<ref name="Higgins2006">Higgins, C.P. and Luthy, R.G., 2006. Sorption of Perfluorinated Surfactants on Sediments. Environmental Science and Technology, 40(23), pp. 7251-7256. [https://doi.org/10.1021/es061000n DOI: 10.1021/es061000n]</ref><ref name="Chen2009">Chen, H., Chen, S., Quan, X., Zhao, Y. and Zhao, H., 2009. Sorption of perfluorooctane sulfonate (PFOS) on oil and oil-derived black carbon: Influence of solution pH and [Ca2+]. Chemosphere, 77(10), pp. 1406-1411. [https://doi.org/10.1016/j.chemosphere.2009.09.008 DOI: 10.1016/j.chemosphere.2009.09.008]</ref><ref name="Pan2009">Pan, G., Jia, C., Zhao, D., You, C., Chen, H. and Jiang, G., 2009. Effect of cationic and anionic surfactants on the sorption and desorption of perfluorooctane sulfonate (PFOS) on natural sediments. Environmental Pollution, 157(1), pp.325-330. [https://doi.org/10.1016/j.envpol.2008.06.035 DOI: 10.1016/j.envpol.2008.06.035]&nbsp;&nbsp; Free download available from [https://www.researchgate.net/profile/Gang_Pan2/publication/23189567_Effect_of_cationic_and_anionic_surfactants_on_the_sorption_and_desorption_of_perfluorooctane_sulfonate_PFOS_on_natural_sediments/links/5be19d23a6fdcc3a8dc2550d/Effect-of-cationic-and-anionic-surfactants-on-the-sorption-and-desorption-of-perfluorooctane-sulfonate-PFOS-on-natural-sediments.pdf ResearchGate]</ref><ref name="Guelfo2013"/><ref name="Zhao2014"/>.
 
  
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Most PFAS compounds act as surface-active agents (or [[Wikipedia:Surfactant | surfactants]]) due to the presence of a hydrophilic headgroup and a hydrophobic tail.  The hydrophilic headgroup will preferentially partition to the aqueous phase and the hydrophobic tail will preferentially partition to the non-aqueous phase (air or organic material).  As a result, PFAS tend to accumulate at interfaces (air-water, water-NAPL, water-solid) (Figure 2).  This tendency to accumulate at interfaces can influence transport in the atmosphere (on water droplets and hydrated aerosols), in the vadose or unsaturated zone at air-water interfaces, in the presence of NAPLs, and in wastewater treatment systems<ref name="Brusseau2018"/><ref name="Brusseau2019b">Brusseau, M.L., 2019. The Influence of Molecular Structure on the Adsorption of PFAS to Fluid-Fluid Interfaces: Using QSPR to Predict Interfacial Adsorption Coefficients. Water Research, 152, pp. 148-158.  [https://doi.org/10.1016/j.watres.2018.12.057 DOI: 10.1016/j.watres.2018.12.057]&nbsp;&nbsp; [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6374777/ Author’s Manuscript]</ref>.
+
<br clear="left"/>
−
 
 
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In theoretical and experimental studies of transport in unsaturated porous media, adsorption at the air-water interface increased PFOS and PFOA retention<ref name="Brusseau2018"/><ref name="Lyu2018">Lyu, Y., Brusseau, M.L., Chen, W., Yan, N., Fu, X., and Lin, X., 2018.  Adsorption of PFOA at the Air-Water Interface during Transport in Unsaturated Porous Media. Environmental Science and Technology, 52(14), pp. 7745-7753.  [https://doi.org/10.1021/acs.est.8b02348 DOI: 10.1021/acs.est.8b02348]&nbsp;&nbsp; [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6312111/ Author’s Manuscript]</ref><ref name="BrusseauEtAl2019">Brusseau, M.L., Yan, N., Van Glubt, S., Wang, Y., Chen, W., Lyu, Y., Dungan, B., Carroll, K.C., and Holguin, F.O., 2019. Comprehensive Retention Model for PFAS Transport in Subsurface Systems. Water Research, 148, pp. 41-50.  [https://doi.org/10.1016/j.watres.2018.10.035 DOI: 10.1016/j.watres.2018.10.035]&nbsp;&nbsp; [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6294326/ Author’s Manuscript]</ref>, contributing approximately 20% to 80% of total retention in sands and soil. The impact of oil-water interfacial adsorption on PFAS transport was also quantitatively characterized in recent studies and shown to contribute to total retention on a similar scale as air-water interfacial adsorption<ref name="Brusseau2018"/><ref name="BrusseauEtAl2019"/>.  These processes may result in increased PFAS mass retained in NAPL source zones, increased PFAS sorption with the resulting retardation of transport, and greater persistence of dissolved PFAS in the environment.
 
  
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==Transformation==
+
==Advantages==
−
[[File:AndersonBrusseau1w2Fig3.png | thumb | 400px | Figure 3. Conceptual model of precursor transformation resulting in the formation of PFAAs. Source L. Trozzolo, TRC and C. Higgins, Colorado School of Mines, used with permission.]]
+
A UV/sulfite treatment system offers significant advantages for PFAS destruction compared to other technologies, including high defluorination percentage, high treatment efficiency for short-chain PFAS without mass transfer limitation, selective reactivity by ''e<sub><small>aq</small></sub><sup><big>'''-'''</big></sup>'', low energy consumption, and the production of no harmful byproducts. A summary of these advantages is provided below:
−
Certain polyfluorinated substances have the potential to transform to other PFAS, with PFAAs as the typical terminal daughter products. These polyfluorinated substances are often referred to as “precursors”. The transformation potential of polyfluorinated precursors is influenced by the presence, location, and number of carbon-hydrogen (C-H) bonds and potentially carbon-oxygen (C-O) bonds throughout the carbon chain. Specifically, PFAS with C-H bonds are subject to a variety of biotic and abiotic reactions that ultimately result in the formation of PFAAs with perfluorinated carbon chains of the same length or shorter than the initial polyfluorinated precursor<ref name="Houtz2013">Houtz, E.F., Higgins, C.P., Field, J.A. and Sedlak, D.L., 2013. Persistence of perfluoroalkyl acid precursors in AFFF-impacted groundwater and soil. Environmental Science and Technology, 47(15), pp. 8187-8195. [https://doi.org/10.1021/es4018877 DOI: 10.1021/es4018877]&nbsp;&nbsp; Free download from [https://www.researchgate.net/profile/Erika_Houtz/publication/252323955_Persistence_of_Perfluoroalkyl_Acid_Precursors_in_AFFF-Impacted_Groundwater_and_Soil/links/59dbddeeaca2728e2018336d/Persistence-of-Perfluoroalkyl-Acid-Precursors-in-AFFF-Impacted-Groundwater-and-Soil.pdf ReseqarchGate]</ref><ref name="McGuire2014">McGuire, M.E., Schaefer, C., Richards, T., Backe, W.J., Field, J.A., Houtz, E., Sedlak, D.L., Guelfo, J.L., Wunsch, A., and Higgins, C.P., 2014. Evidence of Remediation-Induced Alteration of Subsurface Poly- and Perfluoroalkyl Substance Distribution at a Former Firefighter Training Area. Environmental Science and Technology, 48(12) pp. 6644-6652. [https://doi.org/10.1021/es5006187 DOI: 10.1021/es5006187]&nbsp;&nbsp; Manuscript available from [https://ir.library.oregonstate.edu/downloads/td96k706f Oregon State University]</ref><ref name="Anderson2016">Anderson, R.H., Long, G.C., Porter, R.C. and Anderson, J.K., 2016. Occurrence of select perfluoroalkyl substances at US Air Force aqueous film-forming foam release sites other than fire-training areas: Field-validation of critical fate and transport properties. Chemosphere, 150, pp. 678-685. [https://doi.org/10.1016/j.chemosphere.2016.01.014 DOI: 10.1016/j.chemosphere.2016.01.014]</ref><ref name="Weber2017"/>.
+
*'''High efficiency for short- and ultrashort-chain PFAS:''' While the degradation efficiency for short-chain PFAS is challenging for some treatment technologies<ref>Singh, R.K., Brown, E., Mededovic Thagard, S., Holson, T.M., 2021. Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor. Journal of Hazardous Materials, 408, Article 124452. [https://doi.org/10.1016/j.jhazmat.2020.124452 doi: 10.1016/j.jhazmat.2020.124452]</ref><ref>Singh, R.K., Multari, N., Nau-Hix, C., Woodard, S., Nickelsen, M., Mededovic Thagard, S., Holson, T.M., 2020. Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor. Environmental Science and Technology, 54(21), pp. 13973-80. [https://doi.org/10.1021/acs.est.0c02158 doi: 10.1021/acs.est.0c02158]</ref><ref>Nau-Hix, C., Multari, N., Singh, R.K., Richardson, S., Kulkarni, P., Anderson, R.H., Holsen, T.M., Mededovic Thagard S., 2021. Field Demonstration of a Pilot-Scale Plasma Reactor for the Rapid Removal of Poly- and Perfluoroalkyl Substances in Groundwater. American Chemical Society’s Environmental Science and Technology (ES&T) Water, 1(3), pp. 680-87. [https://doi.org/10.1021/acsestwater.0c00170 doi: 10.1021/acsestwater.0c00170]</ref>, the UV/sulfite process demonstrates excellent defluorination efficiency for both short- and ultrashort-chain PFAS, including [[Wikipedia: Trifluoroacetic acid | trifluoroacetic acid (TFA)]] and [[Wikipedia: Perfluoropropionic acid | perfluoropropionic acid (PFPrA)]]. 
 +
*'''High defluorination ratio:''' As shown in Figure 3, the UV/sulfite treatment system has demonstrated near 100% defluorination for various PFAS under both laboratory and field conditions.
 +
*'''No harmful byproducts:''' While some oxidative technologies, such as electrochemical oxidation, generate toxic byproducts, including perchlorate, bromate, and chlorate, the UV/sulfite system employs a reductive mechanism and does not generate these byproducts.
 +
*'''Ambient pressure and low temperature:''' The system operates under ambient pressure and low temperature (<60°C), as it utilizes UV light and common chemicals to degrade PFAS. 
 +
*'''Low energy consumption:''' The electrical energy per order values for the degradation of [[Wikipedia: Perfluoroalkyl carboxylic acids | perfluorocarboxylic acids (PFCAs)]] by UV/sulfite have been reduced to less than 1.5 kilowatt-hours (kWh) per cubic meter under laboratory conditions. The energy consumption is orders of magnitude lower than that for many other destructive PFAS treatment technologies (e.g., [[Supercritical Water Oxidation (SCWO) | supercritical water oxidation]])<ref>Nzeribe, B.N., Crimi, M., Mededovic Thagard, S., 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>.
 +
*'''Co-contaminant destruction:''' The UV/sulfite system has also been reported effective in destroying certain co-contaminants in wastewater. For example, UV/sulfite is reported to be effective in reductive dechlorination of chlorinated volatile organic compounds, such as trichloroethene, 1,2-dichloroethane, and vinyl chloride<ref>Jung, B., Farzaneh, H., Khodary, A., Abdel-Wahab, A., 2015. Photochemical degradation of trichloroethylene by sulfite-mediated UV irradiation. Journal of Environmental Chemical Engineering, 3(3), pp. 2194-2202. [https://doi.org/10.1016/j.jece.2015.07.026 doi: 10.1016/j.jece.2015.07.026]</ref><ref>Liu, X., Yoon, S., Batchelor, B., Abdel-Wahab, A., 2013. Photochemical degradation of vinyl chloride with an Advanced Reduction Process (ARP) – Effects of reagents and pH. Chemical Engineering Journal, 215-216, pp. 868-875. [https://doi.org/10.1016/j.cej.2012.11.086 doi: 10.1016/j.cej.2012.11.086]</ref><ref>Li, X., Ma, J., Liu, G., Fang, J., Yue, S., Guan, Y., Chen, L., Liu, X., 2012. Efficient Reductive Dechlorination of Monochloroacetic Acid by Sulfite/UV Process. Environmental Science and Technology, 46(13), pp. 7342-49. [https://doi.org/10.1021/es3008535 doi: 10.1021/es3008535]</ref><ref>Li, X., Fang, J., Liu, G., Zhang, S., Pan, B., Ma, J., 2014. Kinetics and efficiency of the hydrated electron-induced dehalogenation by the sulfite/UV process. Water Research, 62, pp. 220-228. [https://doi.org/10.1016/j.watres.2014.05.051 doi: 10.1016/j.watres.2014.05.051]</ref>.
  
−
Transformation studies published to date have tested only a small subsample of possible precursors and, therefore, much uncertainty exists regarding 1) the extent to which precursor transformation occurs on a global scale, 2) which environmental compartments represent the majority of transformation, 3) relevant environmental conditions that affect transformation processes, and 4) transformation rates and pathways. Nevertheless, a portion of the precursors are expected to transform to PFAAs over time as shown in Figure 3.
+
==Limitations==
 +
Several environmental factors and potential issues have been identified that may impact the performance of the UV/sulfite treatment system, as listed below. Solutions to address these issues are also proposed.
 +
*Environmental factors, such as the presence of elevated concentrations of natural organic matter (NOM), dissolved oxygen, or nitrate, can inhibit the efficacy of UV/sulfite treatment systems by scavenging available hydrated electrons. Those interferences are commonly managed through chemical additions, reaction optimization, and/or dilution, and are therefore not considered likely to hinder treatment success.
 +
*Coloration in waste streams may also impact the effectiveness of the UV/sulfite treatment system by blocking the transmission of UV light, thus reducing the UV lamp's effective path length. To address this, pre-treatment may be necessary to enable UV/sulfite destruction of PFAS in the waste stream. Pre-treatment may include the use of strong oxidants or coagulants to consume or remove UV-absorbing constituents.
 +
*The degradation efficiency is strongly influenced by PFAS molecular structure, with fluorotelomer sulfonates (FTS) and [[Wikipedia: Perfluorobutanesulfonic acid | perfluorobutanesulfonate (PFBS)]] exhibiting greater resistance to degradation by UV/sulfite treatment compared to other PFAS compounds.
  
−
Precursors can be transformed by a variety of abiotic processes including hydrolysis, photolysis, and oxidation. Hydrolysis of some precursors, followed by subsequent biotransformation, can produce perfluoroalkyl sulfonates (PFSAs). An important example is the production of PFOS from perfluorooctane sulfonyl fluoride (POSF)<ref name="Martin2010">Martin, J.W., Asher, B.J., Beesoon, S., Benskin, J.P. and Ross, M.S., 2010. PFOS or PreFOS? Are perfluorooctane sulfonate precursors (PreFOS) important determinants of human and environmental perfluorooctane sulfonate (PFOS) exposure? Journal of Environmental Monitoring, 12(11), pp.1979-2004. [https://doi.org/10.1039/C0EM00295J DOI: 10.1039/C0EM00295J]&nbsp;&nbsp; Free download from [https://www.researchgate.net/profile/Matthew_Ross3/publication/47415684_PFOS_or_PreFOS_Are_perfluorooctane_sulfonate_precursors_PreFOS_important_determinants_of_human_and_environmental_perfluorooctane_sulfonate_PFOS_exposure/links/00b7d520a6132da945000000.pdf ResearchGate]</ref>.  Other hydrolysis reactions produce perfluoroalkyl carboxylates (PFCAs). At neutral pH, the hydrolysis of fluorotelomer-derived polymeric precursors results in the formation of monomeric precursors of PFOA and other PFAAs with half-lives of 50 to 90 years)<ref name="Washington2010">Washington, J.W., Ellington, J.J., Jenkins, T.M. and Yoo, H., 2010. Response to Comments on “Degradability of an Acrylate-Linked, Fluorotelomer Polymer in Soil”. Environmental Science and Technology, 44(2), pp. 849-850.  [https://doi.org/10.1021/es902672q DOI: 10.1021/es902672q]&nbsp;&nbsp; [https://pubs.acs.org/doi/pdf/10.1021/es902672q Free Download from ACS].</ref>.  Oxidation of precursors by hydroxyl radicals can occur in natural waters, with the fluorotelomer-derived precursors being oxidized relatively rapidly<ref name="Gauthier2005">Gauthier, S.A. and Mabury, S.A., 2005. Aqueous photolysis of 8: 2 fluorotelomer alcohol. Environmental Toxicology and Chemistry, 24(8), pp.1837-1846. [https://doi.org/10.1897/04-591R.1 DOI: 10.1897/04-591R.1]&nbsp;&nbsp; Free download from [https://www.researchgate.net/profile/Suzanne_Gauthier/publication/7609648_Aqueous_photolysis_of_8_2_fluorotelomer_alcohol/links/5ec16c4792851c11a86d9438/Aqueous-photolysis-of-8-2-fluorotelomer-alcohol.pdf ResearchGate].</ref><ref name="Plumlee2009">Plumlee, M.H., McNeill, K. and Reinhard, M., 2009. Indirect Photolysis of Perfluorochemicals: Hydroxyl Radical-Initiated Oxidation of N-Ethyl Perfluorooctane Sulfonamido Acetate (N-EtFOSAA) and Other Perfluoroalkanesulfonamides. Environmental Science and Technology, 43(10), pp.3662-3668.  [https://doi.org/10.1021/es803411w DOI: 10.1021/es803411w]&nbsp;&nbsp; Free download from [https://www.researchgate.net/profile/Megan_Plumlee/publication/26309488_Indirect_Photolysis_of_Perfluorochemicals_Hydroxyl_Radical-Initiated_Oxidation_of_N-Ethyl_Perfluorooctane_Sulfonamido_Acetate_N-EtFOSAA_and_Other_Perfluoroalkanesulfonamides/links/5aac0437a6fdcc1bc0b8d002/Indirect-Photolysis-of-Perfluorochemicals-Hydroxyl-Radical-Initiated-Oxidation-of-N-Ethyl-Perfluorooctane-Sulfonamido-Acetate-N-EtFOSAA-and-Other-Perfluoroalkanesulfonamides.pdf ResearchGate].</ref>.
+
==State of the Practice==
−
Evidence of aerobic biotransformation is provided from studies of PFAS composition throughout the continuum of wastewater treatments<ref name="Arvaniti2015">Arvaniti, O.S. and Stasinakis, A.S., 2015. Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment. Science of the Total Environment, 524, pp. 81-92.  [https://doi.org/10.1016/j.scitotenv.2015.04.023 DOI: 10.1016/j.scitotenv.2015.04.023]</ref>, from field studies at AFFF-impacted sites<ref name="Houtz2013"/><ref name="McGuire2014"/><ref name="Anderson2016"/><ref name="Weber2017"/>, and from microcosm experiments. In general, the literature on aerobic biotransformation collectively demonstrates or indirectly supports the following conclusions as summarized in ITRC 2020<ref name="ITRC2020"/>:
+
[[File: XiongFig2.png | thumb | 500 px | Figure 2. Field demonstration of EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> for PFAS destruction in a concentrated waste stream in a Mid-Atlantic Naval Air Station: a) Target PFAS at each step of the treatment shows that about 99% of PFAS were destroyed; meanwhile, the final degradation product, i.e., fluoride, increased to 15 mg/L in concentration, demonstrating effective PFAS destruction; b) AOF concentrations at each step of the treatment provided additional evidence to show near-complete mineralization of PFAS. Average results from multiple batches of treatment are shown here.]]
−
* Numerous aerobic biotransformation pathways exist with relatively rapid kinetics
+
[[File: XiongFig3.png | thumb | 500 px | Figure 3. Field demonstration of a treatment train (SAFF + EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>) for groundwater PFAS separation and destruction at an Air Force base in California: a) Two main components of the treatment train, i.e. SAFF and EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>; b) Results showed the effective destruction of various PFAS in the foam fractionate. The target PFAS at each step of the treatment shows that about 99.9% of PFAS were destroyed. Meanwhile, the final degradation product, i.e., fluoride, increased to 30 mg/L in concentration, demonstrating effective destruction of PFAS in a foam fractionate concentrate. After a polishing treatment step (GAC) via the onsite groundwater extraction and treatment system, all PFAS were removed to concentrations below their MCLs.]]  
−
* All polyfluorinated precursors studied to date have the potential to aerobically biotransform to PFAAs
+
The effectiveness of UV/sulfite technology for treating PFAS has been evaluated in two field demonstrations using the EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> system. Aqueous samples collected from the system were analyzed using EPA Method 1633, the [[Wikipedia: TOP Assay | total oxidizable precursor (TOP) assay]], adsorbable organic fluorine (AOF) method, and non-target analysis. A summary of each demonstration and their corresponding PFAS treatment efficiency is provided below.  
−
* Aerobic biotransformation of various fluorotelomer-derived precursors exclusively results in the formation of PFCAs, including PFOA, without necessarily the conservation of chain-length
+
*Under the [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)] [https://serdp-estcp.mil/projects/details/4c073623-e73e-4f07-a36d-e35c7acc75b6/er21-5152-project-overview Project ER21-5152], a field demonstration of EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was conducted at a Navy site on the east coast, and results showed that the technology was highly effective in destroying various PFAS in a liquid concentrate produced from an ''in situ'' foam fractionation groundwater treatment system. As shown in Figure 2a, total PFAS concentrations were reduced from 17,366 micrograms per liter (µg/L) to 195 µg/L at the end of the UV/sulfite reaction, representing 99% destruction. After the ion exchange resin polishing step, all residual PFAS had been removed to the non-detect level, except one compound (PFOS) reported as 1.5 nanograms per liter (ng/L), which is below the current Maximum Contaminant Level (MCL) of 4 ng/L. Meanwhile, the fluoride concentration increased up to 15 milligrams per liter (mg/L), confirming near complete defluorination. Figure 2b shows the adsorbable organic fluorine results from the same treatment test, which similarly demonstrates destruction of 99% of PFAS.
−
* Aerobic biotransformation of various electrochemical fluorination-derived precursors primarily results in the formation of PFAAs, including PFOS, with the conservation of chain-length
+
*Another field demonstration was completed at an Air Force base in California, where a treatment train combining [https://serdp-estcp.mil/projects/details/263f9b50-8665-4ecc-81bd-d96b74445ca2 Surface Active Foam Fractionation (SAFF)] and EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was used to treat PFAS in groundwater. As shown in Figure 3, PFAS analytical data and fluoride results demonstrated near-complete destruction of various PFAS. In addition, this demonstration showed: a) high PFAS destruction ratio was achieved in the foam fractionate, even in very high concentration (up to 1,700 mg/L of booster), and b) the effluent from EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/> was sent back to the influent of the SAFF system for further concentration and treatment, resulting in a closed-loop treatment system and no waste discharge from EradiFluor<sup><small>TM</small></sup><ref name="EradiFluor"/>. This field demonstration was conducted with the approval of three regulatory agencies (United States Environmental Protection Agency, California Regional Water Quality Control Board, and California Department of Toxic Substances Control).
−
Precursor transformation can complicate CSMs (and risk assessments) and should be considered during comprehensive site investigations.  For example, atmospheric emissions of volatile precursors can result in long-range transport where subsequent transformation and deposition can result in detectable levels of PFAAs in environmental media independent of obvious point-sources<ref name="Vedagiri2018">Vedagiri, U.K., Anderson, R.H., Loso, H.M. and Schwach, C.M., 2018. Ambient levels of PFOS and PFOA in multiple environmental media. Remediation Journal, 28(2), pp. 9-51.  [https://doi.org/10.1002/rem.21548 DOI: 10.1002/rem.21548]</ref>.  With respect to site-related precursors, transformation of otherwise unmeasured PFAS into detectable PFAAs is obviously relevant to site investigations to the extent transformation occurs after initial site characterization efforts or if past remedial efforts have accelerated ''in situ'' transformation rates<ref name="McGuire2014"/>.  Additionally, differential transport rates between precursor PFAS and the corresponding terminal PFAA could also confound CSMs if transformation rates are slower than transport rates as has been suggested<ref name="Weber2017"/>.  
 
−
To account for otherwise unmeasurable precursors, several surrogate analytical methods have been developed. See [[PFAS Sampling and Analytical Methods]] for additional detail.
 
  
 
==References==
 
==References==
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<references/>
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<references />
  
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==See Also:==
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==See Also==

Latest revision as of 10:17, 13 February 2026

In Situ Toxicity Identification Evaluation (iTIE)

The in situ Toxicity Identification Evaluation system is a tool to incorporate into weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.

Related Article(s):

Contributors: Dr. G. Allen Burton Jr., Austin Crane

Key Resources:

  • A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites[1]
  • An in situ toxicity identification and evaluation water analysis system: Laboratory validation[2]
  • Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document- [3]
  • In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- [4]

Introduction

In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)[5], can be confounded by sample manipulation artifacts and temporal limitations of ex situ organism exposures[1]. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The in situ Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.

The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods[6][7][1][2]. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, metals, pesticides, polychlorinated biphenyls (PCB), polycyclic aromatic hydrocarbons (PAH), and per- and polyfluoroalkyl substances (PFAS), among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression[1].

System Components and Validation

Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.

The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water in situ. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.

Porewater and Surface Water Collection Sub-system

Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver

Given the importance of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies[8]. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.

The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.

Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.

Oxygen Coil, Overflow Bag and Drip Chamber

Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.

Porewater is naturally anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.

Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.

iTIE Units: Fractionation and Organism Exposure Chambers

Figure 4. A diagram of the iTIE prototype. Water flows upward into each resin chamber through the unit bottom. After being chemically fractionated in the resin chamber, water travels into the organism chamber, where test organisms have been placed. Water is drawn through the units by high-precision peristaltic pumps.

At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton et al.[1], the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an in situ exposure. Currently, the iTIE system can support four independent iTIE treatment units.

After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.

Pumping Sub-system

Figure 5. The iTIE system pumping sub-system. The sub-system consists of: A) a single booster pump, which is directly connected to the water sampling device and feeds water to the rest of the iTIE system, and B) a set of four regulation pumps, which each connect to the outflow of an individual iTIE unit. Each pump set is housed in a waterproof case with self-contained rechargeable battery power. A tablet is mounted inside the lid of the four pump case, which can be used to program and operate all of the pumps when connected to the internet.

Water movement through the system is driven by a series of high-precision, programmable peristaltic pumps (EcoTech Marine). Each pump set is housed in a Pelican storm travel case. Power is supplied to each pump by internal rechargeable lithium-iron phosphate batteries (Bioenno Power).

First, water is supplied to the system by a booster pump (Figure 5A). This pump is situated between the water sampling sub-system and the oxygen coil. The booster pump: 1) facilitates pore water collection, especially from sediments with high fine particle fractions; 2) helps water overcome vertical lifts to travel to the iTIE system; and 3) prevents vacuums from forming in the iTIE system interior, which can accelerate the formation of disruptive gas bubbles in the oxygen coil. The booster pump should be programmed to supply an excess of water to prevent vacuum formation.

Second, a set of four regulation pumps ensure precise flow rates through each independent iTIE unit (Figure 5B). Each regulation pump pulls water from the top of an iTIE unit and then dispenses that water into a sample bottle for further analysis.

Study Design Considerations

Diagnostic Resin Treatments

Several commercially available resins have been verified for use in the iTIE system. Investigators can select resins based on stressor classes of interest at each site. Each resin selectively removes a CoC class from site water prior to organism exposure.

Resins must be adequately conditioned prior to use. Otherwise, they may inadequately adsorb toxicants or cause stress to organisms. New resins should be tested for efficacy and toxicity before being used in an iTIE system.

Test Organism Species and Life Stages


Advantages

A UV/sulfite treatment system offers significant advantages for PFAS destruction compared to other technologies, including high defluorination percentage, high treatment efficiency for short-chain PFAS without mass transfer limitation, selective reactivity by eaq-, low energy consumption, and the production of no harmful byproducts. A summary of these advantages is provided below:

  • High efficiency for short- and ultrashort-chain PFAS: While the degradation efficiency for short-chain PFAS is challenging for some treatment technologies[12][13][14], the UV/sulfite process demonstrates excellent defluorination efficiency for both short- and ultrashort-chain PFAS, including trifluoroacetic acid (TFA) and perfluoropropionic acid (PFPrA).
  • High defluorination ratio: As shown in Figure 3, the UV/sulfite treatment system has demonstrated near 100% defluorination for various PFAS under both laboratory and field conditions.
  • No harmful byproducts: While some oxidative technologies, such as electrochemical oxidation, generate toxic byproducts, including perchlorate, bromate, and chlorate, the UV/sulfite system employs a reductive mechanism and does not generate these byproducts.
  • Ambient pressure and low temperature: The system operates under ambient pressure and low temperature (<60°C), as it utilizes UV light and common chemicals to degrade PFAS.
  • Low energy consumption: The electrical energy per order values for the degradation of perfluorocarboxylic acids (PFCAs) by UV/sulfite have been reduced to less than 1.5 kilowatt-hours (kWh) per cubic meter under laboratory conditions. The energy consumption is orders of magnitude lower than that for many other destructive PFAS treatment technologies (e.g., supercritical water oxidation)[15].
  • Co-contaminant destruction: The UV/sulfite system has also been reported effective in destroying certain co-contaminants in wastewater. For example, UV/sulfite is reported to be effective in reductive dechlorination of chlorinated volatile organic compounds, such as trichloroethene, 1,2-dichloroethane, and vinyl chloride[16][17][18][19].

Limitations

Several environmental factors and potential issues have been identified that may impact the performance of the UV/sulfite treatment system, as listed below. Solutions to address these issues are also proposed.

  • Environmental factors, such as the presence of elevated concentrations of natural organic matter (NOM), dissolved oxygen, or nitrate, can inhibit the efficacy of UV/sulfite treatment systems by scavenging available hydrated electrons. Those interferences are commonly managed through chemical additions, reaction optimization, and/or dilution, and are therefore not considered likely to hinder treatment success.
  • Coloration in waste streams may also impact the effectiveness of the UV/sulfite treatment system by blocking the transmission of UV light, thus reducing the UV lamp's effective path length. To address this, pre-treatment may be necessary to enable UV/sulfite destruction of PFAS in the waste stream. Pre-treatment may include the use of strong oxidants or coagulants to consume or remove UV-absorbing constituents.
  • The degradation efficiency is strongly influenced by PFAS molecular structure, with fluorotelomer sulfonates (FTS) and perfluorobutanesulfonate (PFBS) exhibiting greater resistance to degradation by UV/sulfite treatment compared to other PFAS compounds.

State of the Practice

Figure 2. Field demonstration of EradiFluorTM[20] for PFAS destruction in a concentrated waste stream in a Mid-Atlantic Naval Air Station: a) Target PFAS at each step of the treatment shows that about 99% of PFAS were destroyed; meanwhile, the final degradation product, i.e., fluoride, increased to 15 mg/L in concentration, demonstrating effective PFAS destruction; b) AOF concentrations at each step of the treatment provided additional evidence to show near-complete mineralization of PFAS. Average results from multiple batches of treatment are shown here.
Figure 3. Field demonstration of a treatment train (SAFF + EradiFluorTM[20]) for groundwater PFAS separation and destruction at an Air Force base in California: a) Two main components of the treatment train, i.e. SAFF and EradiFluorTM[20]; b) Results showed the effective destruction of various PFAS in the foam fractionate. The target PFAS at each step of the treatment shows that about 99.9% of PFAS were destroyed. Meanwhile, the final degradation product, i.e., fluoride, increased to 30 mg/L in concentration, demonstrating effective destruction of PFAS in a foam fractionate concentrate. After a polishing treatment step (GAC) via the onsite groundwater extraction and treatment system, all PFAS were removed to concentrations below their MCLs.

The effectiveness of UV/sulfite technology for treating PFAS has been evaluated in two field demonstrations using the EradiFluorTM[20] system. Aqueous samples collected from the system were analyzed using EPA Method 1633, the total oxidizable precursor (TOP) assay, adsorbable organic fluorine (AOF) method, and non-target analysis. A summary of each demonstration and their corresponding PFAS treatment efficiency is provided below.

  • Under the Environmental Security Technology Certification Program (ESTCP) Project ER21-5152, a field demonstration of EradiFluorTM[20] was conducted at a Navy site on the east coast, and results showed that the technology was highly effective in destroying various PFAS in a liquid concentrate produced from an in situ foam fractionation groundwater treatment system. As shown in Figure 2a, total PFAS concentrations were reduced from 17,366 micrograms per liter (µg/L) to 195 µg/L at the end of the UV/sulfite reaction, representing 99% destruction. After the ion exchange resin polishing step, all residual PFAS had been removed to the non-detect level, except one compound (PFOS) reported as 1.5 nanograms per liter (ng/L), which is below the current Maximum Contaminant Level (MCL) of 4 ng/L. Meanwhile, the fluoride concentration increased up to 15 milligrams per liter (mg/L), confirming near complete defluorination. Figure 2b shows the adsorbable organic fluorine results from the same treatment test, which similarly demonstrates destruction of 99% of PFAS.
  • Another field demonstration was completed at an Air Force base in California, where a treatment train combining Surface Active Foam Fractionation (SAFF) and EradiFluorTM[20] was used to treat PFAS in groundwater. As shown in Figure 3, PFAS analytical data and fluoride results demonstrated near-complete destruction of various PFAS. In addition, this demonstration showed: a) high PFAS destruction ratio was achieved in the foam fractionate, even in very high concentration (up to 1,700 mg/L of booster), and b) the effluent from EradiFluorTM[20] was sent back to the influent of the SAFF system for further concentration and treatment, resulting in a closed-loop treatment system and no waste discharge from EradiFluorTM[20]. This field demonstration was conducted with the approval of three regulatory agencies (United States Environmental Protection Agency, California Regional Water Quality Control Board, and California Department of Toxic Substances Control).

References

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  20. ^ 20.0 20.1 20.2 20.3 20.4 20.5 20.6 20.7 Cite error: Invalid <ref> tag; no text was provided for refs named EradiFluor

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