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Latest revision as of 20:39, 15 July 2024

Assessing Vapor Intrusion (VI) Impacts in Neighborhoods with Groundwater Contaminated by Chlorinated Volatile Organic Chemicals (CVOCs)

The VI Diagnosis Toolkit^[1] is a set of tools that can be used individually or in combination to assess vapor intrusion (VI) impacts at one or more buildings overlying regional-scale dissolved chlorinated solvent-impacted groundwater plumes. The strategic use of these tools can lead to confident and efficient neighborhood-scale VI pathway assessments.

Background

Figure 1. Example of instrumentation used for OPTICS monitoring.

Figure 2. Schematic diagram illustrating the OPTICS methodology. High resolution in-situ data are integrated with traditional discrete sample analytical data using partial least-square regression to derive high resolution chemical contaminant concentration data series.

Nationwide, the liability due to contaminated sediments is estimated in the trillions of dollars. Stakeholders are assessing and developing remedial strategies for contaminated sediment sites in major harbors and waterways throughout the U.S. The mobility of contaminants in surface water is a primary transport and risk mechanism^[4]^[5]^[6]; therefore, long-term monitoring of both particulate- and dissolved-phase contaminant concentration prior to, during, and following remedial action is necessary to document remedy effectiveness. Source control and total maximum daily load (TMDL) actions generally require costly manual monitoring of dissolved and particulate contaminant concentrations in surface water. The magnitude of cost for these actions is a strong motivation to implement efficient methods for long-term source control and remedial monitoring.

Traditional surface water monitoring requires mobilization of field teams to manually collect discrete water samples, send samples to laboratories, and await laboratory analysis so that a site evaluation can be conducted. These traditional methods are well known to have inherent cost and safety concerns and are of limited use (due to safety concerns and standby requirements for resources) in capturing the effects of episodic events (e.g., storms) that are important to consider in site risk assessment and remedy selection. Automated water samplers are commercially available but still require significant field support and costly laboratory analysis. Further, automated samplers may not be suitable for analytes with short hold-times and temperature requirements.

Optically-based characterization of surface water contaminants is a cost-effective alternative to traditional discrete water sampling methods. Unlike discrete water sampling, which typically results in sparse data at low resolution, and therefore, is of limited use in determining mass loading, OPTICS (OPTically-based In-situ Characterization System) provides continuous data and allows for a complete understanding of water quality and contaminant transport in response to natural processes and human impacts^[7]^[8]^[9]^[10]^[11]^[12]. The OPTICS tool integrates commercial off-the-shelf in situ aquatic sensors (Figure 1), periodic discrete surface water sample collection, and a multi-parameter statistical prediction model^[13]^[14] to provide high temporal and/or spatial resolution characterization of surface water chemicals of potential concern (COPCs) (Figure 2).

Technology Overview

The principle behind OPTICS is based on the relationship between optical properties of natural waters and the particles and dissolved material contained within them^[15]^[16]^[17]^[18]^[19]^[20]^[21]^[22]. Surface water COPCs such as heavy metals and polychlorinated biphenyls (PCBs) are hydrophobic in nature and tend to sorb to materials in the water column, which have unique optical signatures that can be measured at high-resolution using in situ, commercially available aquatic sensors^[23]^[24]^[25]^[26]. Therefore, high-resolution concentrations of COPCs can be accurately and robustly derived from in situ measurements using statistical methods.

The OPTICS method is analogous to the commonly used empirical derivation of total suspended solids concentration (TSS) from optical turbidity using linear regression^[27]. However, rather than deriving one response variable (TSS) from one predictor variable (turbidity), OPTICS involves derivation of one response variable (e.g., PCB concentration) from a suite of predictor variables (e.g., turbidity, temperature, salinity, and fluorescence of chlorophyll-a) using multi-parameter statistical regression. OPTICS is based on statistical correlation – similar to the turbidity-to-TSS regression technique. The method does not rely on interpolation or extrapolation.

The OPTICS technique utilizes partial least-squares (PLS) regression to determine a combination of physical, optical, and water quality properties that best predicts chemical contaminant concentrations with high variance. PLS regression is a statistically based method combining multiple linear regression and principal component analysis (PCA), where multiple linear regression finds a combination of predictors that best fit a response and PCA finds combinations of predictors with large variance^[13]^[14]. Therefore, PLS identifies combinations of multi-collinear predictors (in situ, high-resolution physical, optical, and water quality measurements) that have large covariance with the response values (discrete surface water chemical contaminant concentration data from samples that are collected periodically, coincident with in situ measurements). PLS combines information about the variances of both the predictors and the responses, while also considering the correlations among them. PLS therefore provides a model with reliable predictive power.

OPTICS in situ measurement parameters include, but are not limited to current velocity, conductivity, temperature, depth, turbidity, dissolved oxygen, and fluorescence of chlorophyll-a and dissolved organic matter. Instrumentation for these measurements is commercially available, robust, deployable in a wide variety of configurations (e.g., moored, vessel-mounted, etc.), powered by batteries, and records data internally and/or transmits data in real-time. The physical, optical, and water quality instrumentation is compact and self-contained. The modularity and automated nature of the OPTICS measurement system enables robust, long-term, autonomous data collection for near-continuous monitoring.

Figure 3. OPTICS to characterize COPC variability in the context of site processes at BCSA. (A) Tidal oscillations (Elev._MSL) and precipitation (Precip.). (B) – (D) OPTICS-derived particulate mercury (PHg) and methylmercury (PMeHg) and total PCBs (TPCBs). Open circles represent discrete water sample data.

OPTICS measurements are provided at a significantly reduced cost relative to traditional monitoring techniques used within the environmental industry. Cost performance analysis shows that monitoring costs are reduced by more than 85% while significantly increasing the temporal and spatial resolution of sampling. The reduced cost of monitoring makes this technology suitable for a number of environmental applications including, but not limited to site baseline characterization, source control evaluation, dredge or stormflow plume characterization, and remedy performance monitoring. OPTICS has been successfully demonstrated for characterizing a wide variety of COPCs: mercury, methylmercury, copper, lead, PCBs, dichlorodiphenyltrichloroethane (DDT) and its related compounds (collectively, DDX), and 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD or dioxin) in a number of different environmental systems ranging from inland lakes and rivers to the coastal ocean. To date, OPTICS has been limited to surface water applications. Additional applications (e.g., groundwater) would require further research and development.

Applications

Figure 4. OPTICS reveals baseflow daily cycling and confirms storm-induced particle-bound COPC resuspension and mobilization through bank interaction. (A) Flow rate (Q) and precipitation (Precip). (B) – (C) OPTICS-derived particulate mercury (PHg) and methylmercury (PMeHg). Open circles represent discrete water sample data.

Figure 5. Three-dimensional volume plot of high spatial resolution OPTICS-derived PCBs in exceedance of baseline showing that PCBs were discharged from the outfall (yellow arrow), remained in suspension, and dispersed elsewhere before settling.

An OPTICS study was conducted at Berry’s Creek Study Area (BCSA), New Jersey in 2014 and 2015 to understand COPC sources and transport mechanisms for development of an effective remediation plan. OPTICS successfully extended periodic discrete surface water samples to continuous, high-resolution measurements of PCBs, mercury, and methylmercury to elucidate COPC sources and transport throughout the BCSA tidal estuary system. OPTICS provided data at resolution sufficient to investigate COC variability in the context of physical processes. The results (Figure 3) facilitated focused and effective site remediation and management decisions that could not be determined based on periodic discrete samples alone, despite over seven years of monitoring at different locations throughout the system over a range of different seasons, tidal phases, and environmental conditions. The BCSA OPTICS methodology and its results have undergone official peer review overseen by the U.S. Environmental Protection Agency (USEPA), and those results have been published in peer-reviewed literature^[7].

OPTICS was applied at the South River, Virginia in 2016 to quantify sources of legacy mercury in the system that are contributing to recontamination and continued elevated mercury concentrations in fish tissue. OPTICS provided information necessary to identify mechanisms for COPC redistribution and to quantify the relative contribution of each mechanism to total mass transport of mercury and methylmercury in the system. Continuous, high-resolution COPC data afforded by OPTICS helped resolve baseflow daily cycling that had never before been observed at the South River (Figure 4) and provided data at temporal resolution necessary to verify storm-induced particle-bound COC resuspension and mobilization through bank interaction. The results informed source control and remedy design and monitoring efforts. Methodology and results from the South River have been published in peer-reviewed literature^[8].

The U.S. Department of Defense’s Environmental Security Technology Certification Program (ESTCP) supported an OPTICS demonstration study at the Pearl Harbor Sediment Site, Hawaii, to determine whether stormwater from Oscar 1 Pier outfall is a contributing source of PCBs to Decision Unit (DU) N-2 (ESTCP Project ER21-5021). High spatial resolution results afforded by ship-based, mobile OPTICS monitoring suggested that PCBs were discharged from the outfall, remained in suspension, and dispersed elsewhere before settling (Figure 5). More details regarding this study were presented by Chang et al. in 2024^[9].

Summary

OPTICS provides:

High resolution surface water chemical contaminant characterization
Cost-effective monitoring and assessment
Versatile and modular monitoring with capability for real-time telemetry
Data necessary for development and validation of conceptual site models
A key line of evidence for designing and evaluating remedies.

Because OPTICS monitoring involves deployment of autonomous sampling instrumentation, a substantially greater volume of data can be collected using this technique compared to traditional sampling, and at a far lower cost. A large volume of data supports evaluation of chemical contaminant concentrations over a range of spatial and temporal scales, and the system can be customized for a variety of environmental applications. OPTICS helps quantify contaminant mass flux and the relative contribution of local transport and source areas to net contaminant transport. OPTICS delivers a strong line of evidence for evaluating contaminant sources, fate, and transport, and for supporting the design of a remedy tailored to address site-specific, risk-driving conditions. The improved understanding of site processes aids in the development of mitigation measures that minimize site risks.

References

^ ^1.0 ^1.1 Johnson, P.C., Guo, Y., Dahlen, P., 2020. The VI Diagnosis Toolkit for Assessing Vapor Intrusion Pathways and Mitigating Impacts in Neighborhoods Overlying Dissolved Chlorinated Solvent Plumes. ESTCP Project ER-201501, Final Report. Project Website Final Report.pdf
^ Johnson, P.C., Guo, Y., Dahlen, P., 2021. CPM Test Guidelines: Use of Controlled Pressure Method Testing for Vapor Intrusion Pathway Assessment. ESTCP ER-201501, Technical Report. Project Website Technical_Report.pdf
^ Johnson, P.C., Guo, Y., and Dahlen, P., 2022. VI Diagnosis Toolkit User Guide, ESTCP ER-201501, User Guide. Project Website User_Guide.pdf
^ Thibodeaux, L.J., 1996. Environmental Chemodynamics: Movement of Chemicals in Air, Water, and Soil, 2nd Edition, Volume 110 of Environmental Science and Technology: A Wiley-Interscience Series of Texts and Monographs. John Wiley & Sons, Inc. 624 pages. ISBN: 0-471-61295-2
^ United States Environmental Protection Agency (USEPA), 2005. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites. Office of Superfund Remediation and Technology Innovation Report, EPA-540-R-05-012. Report.pdf
^ Lick, W., 2008. Sediment and Contaminant Transport in Surface Waters. CRC Press. 416 pages. doi: 10.1201/9781420059885
^ ^7.0 ^7.1 Cite error: Invalid <ref> tag; no text was provided for refs named ChangEtAl2019
^ ^8.0 ^8.1 Cite error: Invalid <ref> tag; no text was provided for refs named ChangEtAl2018
^ ^9.0 ^9.1 Cite error: Invalid <ref> tag; no text was provided for refs named ChangEtAl2024
^ Bergamaschi, B.A., Fleck, J.A., Downing, B.D., Boss, E., Pellerin, B., Ganju, N.K., Schoellhamer, D.H., Byington, A.A., Heim, W.A., Stephenson, M., Fujii, R., 2011. Methyl mercury dynamics in a tidal wetland quantified using in situ optical measurements. Limnology and Oceanography, 56(4), pp. 1355-1371. doi: 10.4319/lo.2011.56.4.1355 Open Access Article
^ Bergamaschi, B.A., Fleck, J.A., Downing, B.D., Boss, E., Pellerin, B.A., Ganju, N.K., Schoellhamer, D.H., Byington, A.A., Heim, W.A., Stephenson, M., Fujii, R., 2012. Mercury Dynamics in a San Francisco Estuary Tidal Wetland: Assessing Dynamics Using In Situ Measurements. Estuaries and Coasts, 35, pp. 1036-1048. doi: 10.1007/s12237-012-9501-3 Open Access Article
^ Bergamaschi, B.A., Krabbenhoft, D.P., Aiken, G.R., Patino, E., Rumbold, D.G., Orem, W.H., 2012. Tidally driven export of dissolved organic carbon, total mercury, and methylmercury from a mangrove-dominated estuary. Environmental Science and Technology, 46(3), pp. 1371-1378. doi: 10.1021/es2029137 Open Access Article
^ ^13.0 ^13.1 de Jong, S., 1993. SIMPLS: an alternative approach to partial least squares regression. Chemometrics and Intelligent Laboratory Systems, 18(3), pp. 251-263. doi: 10.1016/0169-7439(93)85002-X
^ ^14.0 ^14.1 Rosipal, R. and Krämer, N., 2006. Overview and Recent Advances in Partial Least Squares, In: Subspace, Latent Structure, and Feature Selection: Statistical and Optimization Perspectives Workshop, Revised Selected Papers (Lecture Notes in Computer Science, Volume 3940), Springer-Verlag, Berlin, Germany. pp. 34-51. doi: 10.1007/11752790_2
^ Boss, E. and Pegau, W.S., 2001. Relationship of light scattering at an angle in the backward direction to the backscattering coefficient. Applied Optics, 40(30), pp. 5503-5507. doi: 10.1364/AO.40.005503
^ Boss, E., Twardowski, M.S., Herring, S., 2001. Shape of the particulate beam spectrum and its inversion to obtain the shape of the particle size distribution. Applied Optics, 40(27), pp. 4884-4893. doi:10/1364/AO.40.004885
^ Babin, M., Morel, A., Fournier-Sicre, V., Fell, F., Stramski, D., 2003. Light scattering properties of marine particles in coastal and open ocean waters as related to the particle mass concentration. Limnology and Oceanography, 48(2), pp. 843-859. doi: 10.4319/lo.2003.48.2.0843 Open Access Article
^ Coble, P., Hu, C., Gould, R., Chang, G., Wood, M., 2004. Colored dissolved organic matter in the coastal ocean: An optical tool for coastal zone environmental assessment and management. Oceanography, 17(2), pp. 50-59. doi: 10.5670/oceanog.2004.47 Open Access Article
^ Sullivan, J.M., Twardowski, M.S., Donaghay, P.L., Freeman, S.A., 2005. Use of optical scattering to discriminate particle types in coastal waters. Applied Optics, 44(9), pp. 1667–1680. doi: 10.1364/AO.44.001667
^ Twardowski, M.S., Boss, E., Macdonald, J.B., Pegau, W.S., Barnard, A.H., Zaneveld, J.R.V., 2001. A model for estimating bulk refractive index from the optical backscattering ratio and the implications for understanding particle composition in case I and case II waters. Journal of Geophysical Research: Oceans, 106(C7), pp. 14,129-14,142. doi: 10/1029/2000JC000404 Open Access Article
^ Chang, G.C., Barnard, A.H., McLean, S., Egli, P.J., Moore, C., Zaneveld, J.R.V., Dickey, T.D., Hanson, A., 2006. In situ optical variability and relationships in the Santa Barbara Channel: implications for remote sensing. Applied Optics, 45(15), pp. 3593–3604. doi: 10.1364/AO.45.003593
^ Slade, W.H. and Boss, E., 2015. Spectral attenuation and backscattering as indicators of average particle size. Applied Optics, 54(24), pp. 7264-7277. doi: 10/1364/AO.54.007264 Open Access Article
^ Agrawal, Y.C. and Pottsmith, H.C., 2000. Instruments for particle size and settling velocity observations in sediment transport. Marine Geology, 168(1-4), pp. 89-114. doi: 10.1016/S0025-3227(00)00044-X
^ Boss, E., Pegau, W.S., Gardner, W.D., Zaneveld, J.R.V., Barnard, A.H., Twardowski, M.S., Chang, G.C., Dickey, T.D., 2001. Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf. Journal of Geophysical Research: Oceans, 106(C5), pp. 9509-9516. doi: 10.1029/2000JC900077 Open Access Article
^ Boss, E., Pegau, W.S., Lee, M., Twardowski, M., Shybanov, E., Korotaev, G. Baratange, F., 2004. Particulate backscattering ratio at LEO 15 and its use to study particle composition and distribution. Journal of Geophysical Research: Oceans, 109(C1), Article C01014. doi: 10.1029/2002JC001514 Open Access Article
^ Briggs, N.T., Slade, W.H., Boss, E., Perry, M.J., 2013. Method for estimating mean particle size from high-frequency fluctuations in beam attenuation or scattering measurement. Applied Optics, 52(27), pp. 6710-6725. doi: 10.1364/AO.52.006710 Open Access Article
^ Rasmussen, P.P., Gray, J.R., Glysson, G.D., Ziegler, A.C., 2009. Guidelines and procedures for computing time-series suspended-sediment concentrations and loads from in-stream turbidity-sensor and streamflow data. In: Techniques and Methods, Book 3: Applications of Hydraulics, Section C: Sediment and Erosion Techniques, Ch. 4. 52 pages. U.S. Geological Survey. Open Access Article

@@ Line 1: / Line 1: @@
-==1,2,3-Trichloropropane (TCP)==
+==Assessing Vapor Intrusion (VI) Impacts in Neighborhoods with Groundwater Contaminated by Chlorinated Volatile Organic Chemicals (CVOCs)==
-[[Wikipedia: 1,2,3-Trichloropropane | 1,2,3-Trichloropropane (TCP)]] is a chlorinated volatile organic compound (CVOC) that has been used in chemical production processes, in agriculture, and as a solvent, resulting in point and non-point source contamination of soil and groundwater.  TCP is mobile and highly persistent in soil and groundwater. TCP is not currently regulated at the national level in the United States, but [[Wikipedia: Maximum contaminant level | maximum contaminant levels (MCLs)]] have been developed by some states.  Current treatment methods for TCP are limited and can be cost prohibitive. However, some treatment approaches, particularly [[Chemical Reduction (In Situ - ISCR) | ''in situ'' chemical reduction (ISCR)]] with [[Wikipedia: In_situ_chemical_reduction#Zero_valent_metals_%28ZVMs%29 | zero valent zinc (ZVZ)]] and [[Bioremediation - Anaerobic | ''in situ'' bioremediation (ISB)]], have recently been shown to have potential as practical remedies for TCP contamination of groundwater.
+The VI Diagnosis Toolkit<ref name="JohnsonEtAl2020">Johnson, P.C., Guo, Y., Dahlen, P., 2020.  The VI Diagnosis Toolkit for Assessing Vapor Intrusion Pathways and Mitigating Impacts in Neighborhoods Overlying Dissolved Chlorinated Solvent Plumes.  ESTCP Project ER-201501, Final Report. [https://serdp-estcp.mil/projects/details/a0d8bafd-c158-4742-b9fe-5f03d002af71 Project Website]&nbsp;&nbsp; [[Media: ER-201501.pdf | Final Report.pdf]]</ref> is a set of tools that can be used individually or in combination to assess vapor intrusion (VI) impacts at one or more buildings overlying regional-scale dissolved chlorinated solvent-impacted groundwater plumes. The strategic use of these tools can lead to confident and efficient neighborhood-scale VI pathway assessments.
 <div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
 '''Related Article(s):'''
-*[[Bioremediation - Anaerobic | Anaerobic Bioremediation]]
-*[[Chemical Reduction (In Situ - ISCR) | ''In Situ'' Chemical Reduction (ISCR)]]
+*[[Vapor Intrusion (VI)]]
-*[[Chemical Oxidation (In Situ - ISCO) | ''In Situ'' Chemical Oxidation (ISCO)]]
+*[[Vapor Intrusion – Sewers and Utility Tunnels as Preferential Pathways]]
 '''Contributor(s):'''
-*[[Dr. Alexandra Salter-Blanc | Alexandra J. Salter-Blanc]]
-*[[Dr. Paul Tratnyek | Paul G. Tratnyek]]
+*Paul C. Johnson, Ph.D.
-*John Merrill
+*Paul Dahlen, Ph.D.
-*Alyssa Saito
+*Yuanming Guo, Ph.D.
-*Lea Kane
-*Eric Suchomel
-*[[Dr. Rula Deeb | Rula Deeb]]
 '''Key Resource(s):'''
-*Prospects for Remediation of 1,2,3-Trichloropropane by Natural and Engineered Abiotic Degradation Reactions. Strategic Environmental Research and Development Program (SERDP), Project ER-1457.<ref name="Tratnyek2010">Tratnyek, P.G., Sarathy, V., Salter, A.J., Nurmi, J.T., O’Brien Johnson, G., DeVoe, T., and Lee, P., 2010. Prospects for Remediation of 1,2,3-Trichloropropane by Natural and Engineered Abiotic Degradation Reactions. Strategic Environmental Research and Development Program (SERDP), Project ER-1457. [https://serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Emerging-Issues/ER-1457/ER-1457/(language)/eng-US  Website]&nbsp;&nbsp; [[Media: ER-1457-FR.pdf | Report.pdf]]</ref>
-*Verification Monitoring for In Situ Chemical Reduction Using Zero-Valent Zinc, A Novel Technology for Remediation of Chlorinated Alkanes. Strategic Environmental Research and Development Program (SERDP), Project ER-201628.<ref name="Kane2020">Kane, L.Z., Suchomel, E.J., and Deeb, R.A., 2020. Verification Monitoring for In Situ Chemical Reduction Using Zero-Valent Zinc, A Novel Technology for Remediation of Chlorinated Alkanes. Strategic Environmental Research and Development Program (SERDP), Project ER-201628. [https://www.serdp-estcp.org/Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Persistent-Contamination/ER-201628  Website]&nbsp;&nbsp; [[Media: ER-201628.pdf | Report.pdf]]</ref>
+*The VI Diagnosis Toolkit for Assessing Vapor Intrusion Pathways and Impacts in Neighborhoods Overlying Dissolved Chlorinated Solvent Plumes, ESTCP Project ER-201501, Final Report<ref name="JohnsonEtAl2020"/>
-==Introduction==
+*CPM Test Guidelines: Use of Controlled Pressure Method Testing for Vapor Intrusion Pathway Assessment, ESTCP Project ER-201501, Technical Report<ref name="JohnsonEtAl2021">Johnson, P.C., Guo, Y., Dahlen, P., 2021.  CPM Test Guidelines: Use of Controlled Pressure Method Testing for Vapor Intrusion Pathway Assessment.  ESTCP ER-201501, Technical Report. [https://serdp-estcp.mil/projects/details/a0d8bafd-c158-4742-b9fe-5f03d002af71 Project Website]&nbsp;&nbsp; [[Media: ER-201501_Technical_Report.pdf | Technical_Report.pdf]]</ref>
-[[File:123TCPFig1.png|thumb|left|Figure 1. Ball and stick representation of the molecular structure of TCP (Salter-Blanc and Tratnyek, unpublished)]]
-,2,3-Trichloropropane (TCP) (Figure 1) is a man-made chemical that was used in the past primarily as a solvent and extractive agent, as a paint and varnish remover, and as a cleaning and degreasing agent.<ref name="ATSDR2021"> Agency for Toxic Substances and Disease Registry (ATSDR), 2021. Toxicological Profile for 1,2,3-Trichloropropane. Free download from: [https://www.atsdr.cdc.gov/toxprofiles/tp57.pdf ATSDR]&nbsp;&nbsp; [[Media: TCP2021ATSDR.pdf | Report.pdf]]</ref>. Currently, TCP is primarily used in chemical synthesis of compounds such as [[Wikipedia: Polysulfone | polysulfone]] liquid polymers used in the aerospace and automotive industries; [[Wikipedia: Hexafluoropropylene | hexafluoropropylene]] used in the agricultural, electronic, and pharmaceutical industries; [[Wikipedia: Polysulfide | polysulfide]] polymers used as sealants in manufacturing and construction; and [[Wikipedia: 1,3-Dichloropropene | 1,3-dichloropropene]] used in agriculture as a soil fumigant. TCP may also be present in products containing these chemicals as an impurity<ref name="ATSDR2021"/><ref name="CH2M2005">CH2M HILL, 2005. Interim Guidance for Investigating Potential 1,2,3-Trichloropropane Sources in San Gabriel Valley Area 3. [[Media: INTERIM_GUIDANCE_FOR_INVESTIGATING_POTENTIAL_1%2C2%2C3-TRICHLOROPROPANE_SOURCES.pdf | Report.pdf]]&nbsp;&nbsp;  [https://cumulis.epa.gov/supercpad/cursites/csitinfo.cfm?id=0902093  Website]</ref>. For example, the 1,2-dichlropropane/1,3-dichloropropene soil fumigant mixture (trade name D-D), which is no longer sold in the United States, contained TCP as an impurity and has been linked to TCP contamination in groundwater<ref name="OkiGiambelluca1987">Oki, D.S. and Giambelluca, T.W., 1987. DBCP, EDB, and TCP Contamination of Ground Water in Hawaii. Groundwater, 25(6), pp. 693-702.  [https://doi.org/10.1111/j.1745-6584.1987.tb02210.x DOI: 10.1111/j.1745-6584.1987.tb02210.x]</ref><ref name="CH2M2005"/>. Soil fumigants currently in use which are composed primarily of 1,3-dichloropropene may also contain TCP as an impurity, for instance Telone II has been reported to contain up to 0.17 percent TCP by weight<ref name="Kielhorn2003">Kielhorn, J., Könnecker, G., Pohlenz-Michel, C., Schmidt, S. and Mangelsdorf, I., 2003. Concise International Chemical Assessment Document 56: 1,2,3-Trichloropropane. World Health Organization, Geneva.  [http://www.who.int/ipcs/publications/cicad/en/cicad56.pdf Website]&nbsp;&nbsp; [[Media: WHOcicad56TCP.pdf | Report.pdf]]</ref>.
-TCP contamination is problematic because it is “reasonably anticipated to be a human carcinogen” based on evidence of carcinogenicity to animals<ref name="NTP2016"> National Toxicology Program, 2016. Report on Carcinogens, 14th ed. U.S. Department of Health and Human Services, Public Health Service. Free download from: [https://ntp.niehs.nih.gov/ntp/roc/content/profiles/trichloropropane.pdf  NIH]&nbsp;&nbsp; [[Media: NTP2016trichloropropane.pdf | Report.pdf]]</ref>. Toxicity to humans appears to be high relative to other chlorinated solvents<ref name="Kielhorn2003"/>, suggesting that even low-level exposure to TCP could pose a significant human health risk.
+*VI Diagnosis Toolkit User Guide, ESTCP Project ER-201501<ref name="JohnsonEtAl2022">Johnson, P.C., Guo, Y., and Dahlen, P., 2022. VI Diagnosis Toolkit User Guide, ESTCP ER-201501, User Guide.  [https://serdp-estcp.mil/projects/details/a0d8bafd-c158-4742-b9fe-5f03d002af71 Project Website]&nbsp;&nbsp; [[Media: ER-201501_User_Guide.pdf | User_Guide.pdf]]</ref>
-==Environmental Fate==
+==Background==
-TCP’s fate in the environment is governed by its physical and chemical properties (Table 1). TCP does not adsorb strongly to soil, making it likely to leach into groundwater and exhibit high mobility. In addition, TCP is moderately volatile and can partition from surface water and moist soil into the atmosphere. Because TCP is only slightly soluble and denser than water, it can form a [[Wikipedia: Dense non-aqueous phase liquid | dense non-aqueous phase liquid (DNAPL)]] as observed at the Tyson’s Dump Superfund Site<ref name="USEPA2019"> United States Environmental Protection Agency (USEPA), 2019. Fifth Five-year Review Report, Tyson’s Dump Superfund Site, Upper Merion Township, Montgomery County, Pennsylvania. Free download from: [https://semspub.epa.gov/work/03/2282817.pdf USEPA]&nbsp;&nbsp; [[Media: USEPA2019.pdf | Report.pdf]]</ref>. TCP is generally resistant to aerobic biodegradation, hydrolysis, oxidation, and reduction under naturally occurring conditions making it persistent in the environment<ref name="Tratnyek2010"/>.
+[[File:ChangFig2.png | thumb | 400px| Figure 1. Example of instrumentation used for OPTICS monitoring.]]
+[[File:ChangFig1.png | thumb | 400px| Figure 2. Schematic diagram illustrating the OPTICS methodology. High resolution in-situ data are integrated with traditional discrete sample analytical data using partial least-square regression to derive high resolution chemical contaminant concentration data series.]]
+Nationwide, the liability due to contaminated sediments is estimated in the trillions of dollars. Stakeholders are assessing and developing remedial strategies for contaminated sediment sites in major harbors and waterways throughout the U.S. The mobility of contaminants in surface water is a primary transport and risk mechanism<ref>Thibodeaux, L.J., 1996. Environmental Chemodynamics: Movement of Chemicals in Air, Water, and Soil, 2nd Edition, Volume 110 of Environmental Science and Technology: A Wiley-Interscience Series of Texts and Monographs. John Wiley & Sons, Inc. 624 pages. ISBN: 0-471-61295-2</ref><ref>United States Environmental Protection Agency (USEPA), 2005. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites. Office of Superfund Remediation and Technology Innovation Report, EPA-540-R-05-012. [[Media: 2005-USEPA-Contaminated_Sediment_Remediation_Guidance.pdf | Report.pdf]]</ref><ref>Lick, W., 2008. Sediment and Contaminant Transport in Surface Waters. CRC Press. 416 pages. [https://doi.org/10.1201/9781420059885 doi:  10.1201/9781420059885]</ref>; therefore, long-term monitoring of both particulate- and dissolved-phase contaminant concentration prior to, during, and following remedial action is necessary to document remedy effectiveness. Source control and total maximum daily load (TMDL) actions generally require costly manual monitoring of dissolved and particulate contaminant concentrations in surface water. The magnitude of cost for these actions is a strong motivation to implement efficient methods for long-term source control and remedial monitoring.
-{| class="wikitable" style="float:right; margin-left:10px;text-align:center;"
+Traditional surface water monitoring requires mobilization of field teams to manually collect discrete water samples, send samples to laboratories, and await laboratory analysis so that a site evaluation can be conducted. These traditional methods are well known to have inherent cost and safety concerns and are of limited use (due to safety concerns and standby requirements for resources) in capturing the effects of episodic events (e.g., storms) that are important to consider in site risk assessment and remedy selection. Automated water samplers are commercially available but still require significant field support and costly laboratory analysis. Further, automated samplers may not be suitable for analytes with short hold-times and temperature requirements.
-|+Table 1.  Physical and chemical properties of TCP<ref name="USEPA2017">United States Environmental Protection Agency (USEPA), 2017. Technical Fact Sheet—1,2,3-Trichloropropane (TCP). EPA Project 505-F-17-007. 6 pp.  Free download from: [https://www.epa.gov/sites/production/files/2017-10/documents/ffrrofactsheet_contaminants_tcp_9-15-17_508.pdf  USEPA]&nbsp;&nbsp; [[Media: epa_tcp_2017.pdf | Report.pdf]]</ref>
-|-
-!Property
-!Value
-|-
-| Chemical Abstracts Service (CAS) Number || 96-18-4
-|-
-| Physical Description</br>(at room temperature) || Colorless to straw-colored liquid
-|-
-| Molecular weight  (g/mol) || 147.43
-|-
-| Water solubility at 25°C  (mg/L)|| 1,750 (slightly soluble)
-|-
-| Melting point  (°C)|| -14.7
-|-
-| Boiling point  (°C) || 156.8
-|-
-| Vapor pressure at 25°C  (mm Hg) || 3.10 to 3.69
-|-
-| Density at 20°C (g/cm<sup>3</sup>) || 1.3889
-|-
-| Octanol-water partition coefficient</br>(log''K<sub>ow</sub>'') || 1.98 to 2.27</br>(temperature dependent)
-|-
-| Organic carbon-water partition coefficient</br>(log''K<sub>oc</sub>'') || 1.70 to 1.99</br>(temperature dependent)
-|-
-| Henry’s Law constant at 25°C</br>(atm-m<sup>3</sup>/mol) || 3.17x10<sup>-4</sup><ref name="ATSDR2021"/> to 3.43x10<sup>-4</sup><ref name="LeightonCalo1981">Leighton Jr, D.T. and Calo, J.M., 1981. Distribution Coefficients of Chlorinated Hydrocarbons in Dilute Air-Water Systems for Groundwater Contamination Applications. Journal of Chemical and Engineering Data, 26(4), pp. 382-385.  [https://doi.org/10.1021/je00026a010 DOI: 10.1021/je00026a010]</ref>
-|}
-==Occurrence==
+Optically-based characterization of surface water contaminants is a cost-effective alternative to traditional discrete water sampling methods. Unlike discrete water sampling, which typically results in sparse data at low resolution, and therefore, is of limited use in determining mass loading, OPTICS (OPTically-based In-situ Characterization System) provides continuous data and allows for a complete understanding of water quality and contaminant transport in response to natural processes and human impacts<ref name="ChangEtAl2019"/><ref name="ChangEtAl2018"/><ref name="ChangEtAl2024"/><ref>Bergamaschi, B.A., Fleck, J.A., Downing, B.D., Boss, E., Pellerin, B., Ganju, N.K., Schoellhamer, D.H., Byington, A.A., Heim, W.A., Stephenson, M., Fujii, R., 2011. Methyl mercury dynamics in a tidal wetland quantified using in situ optical measurements. Limnology and Oceanography, 56(4), pp. 1355-1371. [https://doi.org/10.4319/lo.2011.56.4.1355 doi: 10.4319/lo.2011.56.4.1355]&nbsp;&nbsp; [[Media: BergamaschiEtAl2011.pdf | Open Access Article]]</ref><ref>Bergamaschi, B.A., Fleck, J.A., Downing, B.D., Boss, E., Pellerin, B.A., Ganju, N.K., Schoellhamer, D.H., Byington, A.A., Heim, W.A., Stephenson, M., Fujii, R., 2012. Mercury Dynamics in a San Francisco Estuary Tidal Wetland: Assessing Dynamics Using In Situ Measurements. Estuaries and Coasts, 35, pp. 1036-1048. [https://doi.org/10.1007/s12237-012-9501-3 doi: 10.1007/s12237-012-9501-3]&nbsp;&nbsp; [[Media: BergamaschiEtAl2012a.pdf | Open Access Article]]</ref><ref>Bergamaschi, B.A., Krabbenhoft, D.P., Aiken, G.R., Patino, E., Rumbold, D.G., Orem, W.H., 2012. Tidally driven export of dissolved organic carbon, total mercury, and methylmercury from a mangrove-dominated estuary. Environmental Science and Technology, 46(3), pp. 1371-1378. [https://doi.org/10.1021/es2029137 doi: 10.1021/es2029137]&nbsp;&nbsp; [[Media: BergamaschiEtAl2012b.pdf | Open Access Article]]</ref>. The OPTICS tool integrates commercial off-the-shelf ''in situ'' aquatic sensors (Figure 1), periodic discrete surface water sample collection, and a multi-parameter statistical prediction model<ref name="deJong1993">de Jong, S., 1993. SIMPLS: an alternative approach to partial least squares regression. Chemometrics and Intelligent Laboratory Systems, 18(3), pp. 251-263. [https://doi.org/10.1016/0169-7439(93)85002-X doi: 10.1016/0169-7439(93)85002-X]</ref><ref name="RosipalKramer2006">Rosipal, R. and Krämer, N., 2006. Overview and Recent Advances in Partial Least Squares, In: Subspace, Latent Structure, and Feature Selection: Statistical and Optimization Perspectives Workshop, Revised Selected Papers (Lecture Notes in Computer Science, Volume 3940), Springer-Verlag, Berlin, Germany. pp. 34-51. [https://doi.org/10.1007/11752790_2 doi: 10.1007/11752790_2]</ref> to provide high temporal and/or spatial resolution characterization of surface water chemicals of potential concern (COPCs) (Figure 2).
-TCP has been detected in approximately 1% of public water supply and domestic well samples tested by the United States Geological Survey. More specifically, TCP was detected in 1.2% of public supply well samples collected between 1993 and 2007 by Toccalino and Hopple<ref name="ToccalinoHopple2010">Toccalino, P.L., Norman, J.E., Hitt, K.J., 2010. Quality of Source Water from Public-Supply Wells in the United States, 1993–2007. Scientific Investigations Report 2010-5024. U.S. Geological Survey. [https://doi.org/10.3133/sir20105024 DOI: 10.3133/sir20105024]  Free download from: [https://pubs.er.usgs.gov/publication/sir20105024 USGS]&nbsp;&nbsp; [[Media: Quality_of_source_water_from_public-supply_wells_in_the_United_States%2C_1993-2007.pdf | Report.pdf]]</ref> and 0.66% of domestic supply well samples collected between 1991 and 2004 by DeSimone<ref name="DeSimone2009">DeSimone, L.A., 2009. Quality of Water from Domestic Wells in Principal Aquifers of the United States, 1991–2004. U.S. Geological Survey, Scientific Investigations Report 2008–5227. 139 pp. Free download from: [http://pubs.usgs.gov/sir/2008/5227 USGS]&nbsp;&nbsp; [[Media: DeSimone2009.pdf | Report.pdf]]</ref>. TCP was detected at a higher rate in domestic supply well samples associated with agricultural land-use studies than samples associated with studies comparing primary aquifers (3.5% versus 0.2%)<ref name="DeSimone2009"/>.
-==Regulation==
+==Technology Overview==
-The United States Environmental Protection Agency (USEPA) has not established an MCL for TCP, although guidelines and health standards are in place<ref name="USEPA2017"/>. TCP was included in the Contaminant Candidate List 3<ref name="USEPA2009">United States Environmental Protection Agency (US EPA), 2009. Drinking Water Contaminant Candidate List 3-Final. Federal Register 74(194), pp. 51850–51862, Document E9-24287. [https://www.federalregister.gov/documents/2009/10/08/E9-24287/drinking-water-contaminant-candidate-list-3-final Website]&nbsp;&nbsp; [[Media: FR74-194DWCCL3.pdf | Report.pdf]]</ref> and the Unregulated Contaminant Monitoring Rule 3 (UCMR 3)<ref name="USEPA2012">United States Environmental Protection Agency (US EPA), 2012. Revisions to the Unregulated Contaminant Mentoring Regulation (UCMR 3) for Public Water Systems. Federal Register 77(85) pp. 26072-26101. [https://www.federalregister.gov/documents/2012/05/02/2012-9978/revisions-to-the-unregulated-contaminant-monitoring-regulation-ucmr-3-for-public-water-systems  Website]&nbsp;&nbsp; [[Media: FR77-85UCMR3.pdf | Report.pdf]]</ref>. The UCMR 3 specified that data be collected on TCP occurrence in public water systems over the period of January 2013 through December 2015 against a reference concentration range of 0.0004 to 0.04 μg/L<ref name="USEPA2017a">United States Environmental Protection Agency (USEPA), 2017. The Third Unregulated Contaminant Monitoring Rule (UCMR 3): Data Summary. EPA 815-S-17-001. [https://www.epa.gov/dwucmr/data-summary-third-unregulated-contaminant-monitoring-rule  Website]&nbsp;&nbsp; [[Media: ucmr3-data-summary-january-2017.pdf | Report.pdf]]</ref>. The reference concentration range was determined based on a cancer risk of 10-6 to 10-4 and derived from an oral slope factor of 30 mg/kg-day, which was determined by the EPA’s Integrated Risk Information System<ref name="IRIS2009">USEPA Integrated Risk Information System (IRIS), 2009. 1,2,3-Trichloropropane (CASRN 96-18-4). [https://cfpub.epa.gov/ncea/iris2/chemicalLanding.cfm?substance_nmbr=200 Website]&nbsp;&nbsp; [[Media: TCPsummaryIRIS.pdf | Summary.pdf]]</ref>. Of 36,848 samples collected during UCMR 3, 0.67% exceeded the minimum reporting level of 0.03 µg/L. 1.4% of public water systems had at least one detection over the minimum reporting level, corresponding to 2.5% of the population<ref name="USEPA2017a"/>. While these occurrence percentages are relatively low, the minimum reporting level of 0.03 µg/L is more than 75 times the USEPA-calculated Health Reference Level of 0.0004 µg/L. Because of this, TCP may occur in public water systems at concentrations that exceed the Health Reference Level but are below the minimum reporting level used during UCMR 3 data collection. These analytical limitations and lack of lower-level occurrence data have prevented the USEPA from making a preliminary regulatory determination for TCP<ref name="USEPA2021">USEPA, 2021. Announcement of Final Regulatory Determinations for Contaminants on the Fourth Drinking Water Contaminant Candidate List. Free download from: [https://www.epa.gov/sites/default/files/2021-01/documents/10019.70.ow_ccl_reg_det_4.final_web.pdf USEPA]&nbsp;&nbsp; [[Media: CCL4.pdf | Report.pdf]]</ref>.
+The principle behind OPTICS is based on the relationship between optical properties of natural waters and the particles and dissolved material contained within them<ref>Boss, E. and Pegau, W.S., 2001. Relationship of light scattering at an angle in the backward direction to the backscattering coefficient. Applied Optics, 40(30), pp. 5503-5507. [https://doi.org/10.1364/AO.40.005503 doi: 10.1364/AO.40.005503]</ref><ref>Boss, E., Twardowski, M.S., Herring, S., 2001. Shape of the particulate beam spectrum and its inversion to obtain the shape of the particle size distribution. Applied Optics, 40(27), pp. 4884-4893. [https://doi.org/10.1364/AO.40.004885 doi:10/1364/AO.40.004885]</ref><ref>Babin, M., Morel, A., Fournier-Sicre, V., Fell, F., Stramski, D., 2003. Light scattering properties of marine particles in coastal and open ocean waters as related to the particle mass concentration. Limnology and Oceanography, 48(2), pp. 843-859. [https://doi.org/10.4319/lo.2003.48.2.0843 doi: 10.4319/lo.2003.48.2.0843]&nbsp;&nbsp; [[Media: BabinEtAl2003.pdf | Open Access Article]]</ref><ref>Coble, P., Hu, C., Gould, R., Chang, G., Wood, M., 2004. Colored dissolved organic matter in the coastal ocean: An optical tool for coastal zone environmental assessment and management. Oceanography, 17(2), pp. 50-59. [https://doi.org/10.5670/oceanog.2004.47 doi: 10.5670/oceanog.2004.47]&nbsp;&nbsp; [[Media: CobleEtAl2004.pdf | Open Access Article]]</ref><ref>Sullivan, J.M., Twardowski, M.S., Donaghay, P.L., Freeman, S.A., 2005. Use of optical scattering to discriminate particle types in coastal waters. Applied Optics, 44(9), pp. 1667–1680. [https://doi.org/10.1364/AO.44.001667 doi: 10.1364/AO.44.001667]</ref><ref>Twardowski, M.S., Boss, E., Macdonald, J.B., Pegau, W.S., Barnard, A.H., Zaneveld, J.R.V., 2001. A model for estimating bulk refractive index from the optical backscattering ratio and the implications for understanding particle composition in case I and case II waters. Journal of Geophysical Research: Oceans, 106(C7), pp. 14,129-14,142. [https://doi.org/10.1029/2000JC000404 doi: 10/1029/2000JC000404]&nbsp;&nbsp; [[Media: TwardowskiEtAl2001.pdf | Open Access Article]]</ref><ref>Chang, G.C., Barnard, A.H., McLean, S., Egli, P.J., Moore, C., Zaneveld, J.R.V., Dickey, T.D., Hanson, A., 2006. In situ optical variability and relationships in the Santa Barbara Channel: implications for remote sensing. Applied Optics, 45(15), pp. 3593–3604. [https://doi.org/10.1364/AO.45.003593 doi: 10.1364/AO.45.003593]</ref><ref>Slade, W.H. and Boss, E., 2015. Spectral attenuation and backscattering as indicators of average particle size. Applied Optics, 54(24), pp. 7264-7277. [https://doi.org/10.1364/AO.54.007264 doi: 10/1364/AO.54.007264]&nbsp;&nbsp; [[Media: SladeBoss2015.pdf | Open Access Article]]</ref>. Surface water COPCs such as heavy metals and polychlorinated biphenyls (PCBs) are hydrophobic in nature and tend to sorb to materials in the water column, which have unique optical signatures that can be measured at high-resolution using ''in situ'', commercially available aquatic sensors<ref>Agrawal, Y.C. and Pottsmith, H.C., 2000. Instruments for particle size and settling velocity observations in sediment transport. Marine Geology, 168(1-4), pp. 89-114. [https://doi.org/10.1016/S0025-3227(00)00044-X doi: 10.1016/S0025-3227(00)00044-X]</ref><ref>Boss, E., Pegau, W.S., Gardner, W.D., Zaneveld, J.R.V., Barnard, A.H., Twardowski, M.S., Chang, G.C., Dickey, T.D., 2001. Spectral particulate attenuation and particle size distribution in the bottom boundary layer of a continental shelf. Journal of Geophysical Research: Oceans, 106(C5), pp. 9509-9516. [https://doi.org/10.1029/2000JC900077  doi: 10.1029/2000JC900077]&nbsp;&nbsp; [[Media: BossEtAl2001.pdf | Open Access Article]]</ref><ref>Boss, E., Pegau, W.S., Lee, M., Twardowski, M., Shybanov, E., Korotaev, G. Baratange, F., 2004. Particulate backscattering ratio at LEO 15 and its use to study particle composition and distribution. Journal of Geophysical Research: Oceans, 109(C1), Article C01014. [https://doi.org/10.1029/2002JC001514 doi: 10.1029/2002JC001514]&nbsp;&nbsp; [[Media: BossEtAl2004.pdf | Open Access Article]]</ref><ref>Briggs, N.T., Slade, W.H., Boss, E., Perry, M.J., 2013. Method for estimating mean particle size from high-frequency fluctuations in beam attenuation or scattering measurement. Applied Optics, 52(27), pp. 6710-6725. [https://doi.org/10.1364/AO.52.006710 doi: 10.1364/AO.52.006710]&nbsp;&nbsp; [[Media: BriggsEtAl2013.pdf | Open Access Article]]</ref>. Therefore, high-resolution concentrations of COPCs can be accurately and robustly derived from ''in situ'' measurements using statistical methods.
-Some US states have established their own standards including Hawaii which has established an MCL of 0.6 μg/L<ref name="HDOH2013">Hawaii Department of Health, 2013. Amendment and Compilation of Chapter 11-20 Hawaii Administrative Rules. Free download from: [http://health.hawaii.gov/sdwb/files/2016/06/combodOPPPD.pdf Hawaii Department of Health]&nbsp;&nbsp; [[Media: Amendment_and_Compilation_of_Chapter_11-20_Hawaii_Administrative_Rules.pdf | Report.pdf]]</ref>. California has established an MCL of 0.005 μg/L<ref name="CCR2021">California Code of Regulations, 2021. Section 64444 Maximum Contaminant Levels – Organic Chemicals (22 CA ADC § 64444). [https://govt.westlaw.com/calregs/Document/IA7B3800D18654ABD9E2D24A445A66CB9 Website]</ref>,  a notification level of 0.005 μg/L, and a public health goal of 0.0007 μg/L<ref name="OEHHA2009">Office of Environmental Health Hazard Assessment (OEHHA), California Environmental Protection Agency, 2009. Final Public Health Goal for 1,2,3-Trichloropropane in Drinking Water. [https://oehha.ca.gov/water/public-health-goal/final-public-health-goal-123-trichloropropane-drinking-water Website]</ref>, and New Jersey has established an MCL of 0.03 μg/L<ref name="NJAC2020">New Jersey Administrative Code 7:10, 2020. Safe Drinking Water Act Rules. Free download from: [https://www.nj.gov/dep/rules/rules/njac7_10.pdf  New Jersey Department of Environmental Protection]</ref>.
+The OPTICS method is analogous to the commonly used empirical derivation of total suspended solids concentration (TSS) from optical turbidity using linear regression<ref>Rasmussen, P.P., Gray, J.R., Glysson, G.D., Ziegler, A.C., 2009. Guidelines and procedures for computing time-series suspended-sediment concentrations and loads from in-stream turbidity-sensor and streamflow data. In: Techniques and Methods, Book 3: Applications of Hydraulics, Section C: Sediment and Erosion Techniques, Ch. 4. 52 pages. U.S. Geological Survey.&nbsp;&nbsp; [[Media: RasmussenEtAl2009.pdf | Open Access Article]]</ref>. However, rather than deriving one response variable (TSS) from one predictor variable (turbidity), OPTICS involves derivation of one response variable (e.g., PCB concentration) from a suite of predictor variables (e.g., turbidity, temperature, salinity, and fluorescence of chlorophyll-a) using multi-parameter statistical regression. OPTICS is based on statistical correlation – similar to the turbidity-to-TSS regression technique. The method does not rely on interpolation or extrapolation.
-==Transformation Processes==
+The OPTICS technique utilizes partial least-squares (PLS) regression to determine a combination of physical, optical, and water quality properties that best predicts chemical contaminant concentrations with high variance. PLS regression is a statistically based method combining multiple linear regression and principal component analysis (PCA), where multiple linear regression finds a combination of predictors that best fit a response and PCA finds combinations of predictors with large variance<ref name="deJong1993"/><ref name="RosipalKramer2006"/>. Therefore, PLS identifies combinations of multi-collinear predictors (''in situ'', high-resolution physical, optical, and water quality measurements) that have large covariance with the response values (discrete surface water chemical contaminant concentration data from samples that are collected periodically, coincident with ''in situ'' measurements). PLS combines information about the variances of both the predictors and the responses, while also considering the correlations among them. PLS therefore provides a model with reliable predictive power.
-[[File:123TCPFig2.png|thumb|600px|left|Figure 2. Figure 2. Summary of anticipated primary reaction pathways for degradation of TCP. Oxidation, hydrolysis, and hydrogenolysis are represented by the horizontal arrows. Elimination (dehydrochlorination) and reductive elimination are shown with vertical arrows. [O] represents oxygenation (by oxidation or hydrolysis), [H] represents reduction. Gray indicates products that appear to be of lesser significance<ref name="Tratnyek2010"/>.]]
-Potential TCP degradation pathways include hydrolysis, oxidation, and reduction (Figure 2). These pathways are expected to be similar overall for abiotic and biotic reactions<ref name="Sarathy2010">Sarathy, V., Salter, A.J., Nurmi, J.T., O’Brien Johnson, G., Johnson, R.L., and Tratnyek, P.G., 2010. Degradation of 1, 2, 3-Trichloropropane (TCP): Hydrolysis, Elimination, and Reduction by Iron and Zinc. Environmental Science and Technology, 44(2), pp.787-793.  [https://doi.org/10.1021/es902595j DOI: 10.1021/es902595j]</ref>, but the rates of the reactions (and their resulting significance for remediation) depend on natural and engineered conditions.
-The rate of hydrolysis of TCP is negligible under typical ambient pH and temperature conditions but is favorable at high pH and/or temperature<ref name="Tratnyek2010"/><ref name="Sarathy2010"/>. For example, ammonia gas can be used to raise soil pH and stimulate alkaline hydrolysis of chlorinated propanes including TCP<ref name="Medina2016">Medina, V.F., Waisner, S.A., Griggs, C.S., Coyle, C., and Maxwell, M., 2016. Laboratory-Scale Demonstration Using Dilute Ammonia Gas-Induced Alkaline Hydrolysis of Soil Contaminants (Chlorinated Propanes and Explosives). US Army Engineer Research and Development Center, Environmental Laboratory (ERDC/EL), Report TR-16-10. [http://hdl.handle.net/11681/20312 Website]&nbsp;&nbsp; [[Media: ERDC_EL_TR_16_10.pdf  | Report.pdf]]</ref>. [[Thermal Conduction Heating (TCH)]] may also produce favorable conditions for TCP hydrolysis<ref name="Tratnyek2010"/><ref name="Sarathy2010"/>.
+OPTICS ''in situ'' measurement parameters include, but are not limited to current velocity, conductivity, temperature, depth, turbidity, dissolved oxygen, and fluorescence of chlorophyll-a and dissolved organic matter. Instrumentation for these measurements is commercially available, robust, deployable in a wide variety of configurations (e.g., moored, vessel-mounted, etc.), powered by batteries, and records data internally and/or transmits data in real-time. The physical, optical, and water quality instrumentation is compact and self-contained. The modularity and automated nature of the OPTICS measurement system enables robust, long-term, autonomous data collection for near-continuous monitoring.
-==Treatment Approaches==
+[[File:ChangFig3.png | thumb | 400px| Figure 3. OPTICS to characterize COPC variability in the context of site processes at BCSA. (A) Tidal oscillations (Elev.<sub>MSL</sub>) and precipitation (Precip.). (B) – (D) OPTICS-derived particulate mercury (PHg) and methylmercury (PMeHg) and total PCBs (TPCBs). Open circles represent discrete water sample data.]] OPTICS measurements are provided at a significantly reduced cost relative to traditional monitoring techniques used within the environmental industry. Cost performance analysis shows that monitoring costs are reduced by more than 85% while significantly increasing the temporal and spatial resolution of sampling. The reduced cost of monitoring makes this technology suitable for a number of environmental applications including, but not limited to site baseline characterization, source control evaluation, dredge or stormflow plume characterization, and remedy performance monitoring. OPTICS has been successfully demonstrated for characterizing a wide variety of COPCs: mercury, methylmercury, copper, lead, PCBs, dichlorodiphenyltrichloroethane (DDT) and its related compounds (collectively, DDX), and 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD or dioxin) in a number of different environmental systems ranging from inland lakes and rivers to the coastal ocean. To date, OPTICS has been limited to surface water applications. Additional applications (e.g., groundwater) would require further research and development.
-Compared to more frequently encountered CVOCs such as [[Wikipedia: Trichloroethylene | trichloroethene (TCE)]] and [[Wikipedia: Tetrachloroethylene | tetrachloroethene (PCE)]], TCP is relatively recalcitrant<ref name="Merrill2019">Merrill, J.P., Suchomel, E.J., Varadhan, S., Asher, M., Kane, L.Z., Hawley, E.L., and Deeb, R.A., 2019. Development and Validation of Technologies for Remediation of 1,2,3-Trichloropropane in Groundwater. Current Pollution Reports, 5(4), pp. 228–237.  [https://doi.org/10.1007/s40726-019-00122-7 | DOI: 10.1007/s40726-019-00122-7]</ref><ref name="Tratnyek2010"/>. TCP is generally resistant to hydrolysis, bioremediation, oxidation, and reduction under natural conditions<ref name="Tratnyek2010"/>.  The moderate volatility of TCP makes air stripping, air sparging, and soil vapor extraction (SVE) less effective compared to other VOCs<ref name="Merrill2019"/>. Despite these challenges, both ''ex situ'' and ''in situ'' treatment technologies exist. ''Ex situ'' treatment processes are relatively well established and understood but can be cost prohibitive. ''In situ'' treatment methods are comparatively limited and less-well developed, though promising field-scale demonstrations of some ''in situ'' treatment technologies have been conducted.
-===''Ex Situ'' Treatment===
+==Applications==
-The most common ''ex situ'' treatment technology for groundwater contaminated with TCP is groundwater extraction and treatment<ref name="SaminJanssen2012">Samin, G. and Janssen, D.B., 2012. Transformation and biodegradation of 1,2,3-trichloropropane (TCP). Environmental Science and Pollution Research International, 19(8), pp. 3067-3078. [https://doi.org/10.1007/s11356-012-0859-3 DOI: 10.1007/s11356-012-0859-3]&nbsp;&nbsp; [[Media:  SaminJanssen2012.pdf | Report.pdf]]</ref>. Extraction of TCP is generally effective given its relatively high solubility in water and low degree of partitioning to soil. After extraction, TCP is typically removed by adsorption to granular activated carbon (GAC)<ref name="Merrill2019"/><ref name="CalEPA2017">California Environmental Protection Agency, 2017. Groundwater Information Sheet, 1,2,3-Trichloropropane (TCP). State Water Resources Control Board, Division of Water Quality, Groundwater Ambient Monitoring and Assessment (GAMA) Program, 8 pp. Free download from: [http://www.waterboards.ca.gov/gama/docs/coc_tcp123.pdf California Waterboards]&nbsp;&nbsp; [[Media: CalEPA2017tcp123.pdf | Report.pdf]]</ref>.
+[[File:ChangFig4.png | thumb | 400px| Figure 4. OPTICS reveals baseflow daily cycling and confirms storm-induced particle-bound COPC resuspension and mobilization through bank interaction. (A) Flow rate (Q) and precipitation (Precip). (B) – (C) OPTICS-derived particulate mercury (PHg) and methylmercury (PMeHg). Open circles represent discrete water sample data.]]
+[[File:ChangFig5.png | thumb | 400px| Figure 5. Three-dimensional volume plot of high spatial resolution OPTICS-derived PCBs in exceedance of baseline showing that PCBs were discharged from the outfall (yellow arrow), remained in suspension, and dispersed elsewhere before settling.]]
+An OPTICS study was conducted at Berry’s Creek Study Area (BCSA), New Jersey in 2014 and 2015 to understand COPC sources and transport mechanisms for development of an effective remediation plan. OPTICS successfully extended periodic discrete surface water samples to continuous, high-resolution measurements of PCBs, mercury, and methylmercury to elucidate COPC sources and transport throughout the BCSA tidal estuary system. OPTICS provided data at resolution sufficient to investigate COC variability in the context of physical processes. The results (Figure 3) facilitated focused and effective site remediation and management decisions that could not be determined based on periodic discrete samples alone, despite over seven years of monitoring at different locations throughout the system over a range of different seasons, tidal phases, and environmental conditions. The BCSA OPTICS methodology and its results have undergone official peer review overseen by the U.S. Environmental Protection Agency (USEPA), and those results have been published in peer-reviewed literature<ref name="ChangEtAl2019"/>.
-TCP contamination in drinking water sources is typically treated using granular activated carbon (GAC)<ref name="Hooker2012">Hooker, E.P., Fulcher, K.G. and Gibb, H.J., 2012. Report to the Hawaii Department of Health, Safe Drinking Water Branch, Regarding the Human Health Risks of 1, 2, 3-Trichloropropane in Tap Water. [https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.269.2485&rep=rep1&type=pdf Free Download]&nbsp;&nbsp; [[Media: Hooker2012.pdf | Report.pdf]]</ref>.
+OPTICS was applied at the South River, Virginia in 2016 to quantify sources of legacy mercury in the system that are contributing to recontamination and continued elevated mercury concentrations in fish tissue. OPTICS provided information necessary to identify mechanisms for COPC redistribution and to quantify the relative contribution of each mechanism to total mass transport of mercury and methylmercury in the system. Continuous, high-resolution COPC data afforded by OPTICS helped resolve baseflow daily cycling that had never before been observed at the South River (Figure 4) and provided data at temporal resolution necessary to verify storm-induced particle-bound COC resuspension and mobilization through bank interaction. The results informed source control and remedy design and monitoring efforts. Methodology and results from the South River have been published in peer-reviewed literature<ref name="ChangEtAl2018"/>.
-In California, GAC is considered the best available technology (BAT) for treating TCP, and as of 2017 seven full-scale treatment facilities were using GAC to treat groundwater contaminated with TCP<ref name="CalEPA2017a">California Environmental Protection Agency, 2017.  Initial Statement of Reasons 1,2,3-Trichloropropane Maximum Contaminant Level Regulations. Water Resources Control Board, Title 22, California Code of Regulations (SBDDW-17-001). 36 pp.  [https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/123-tcp/sbddw17_001/isor.pdf  Free download]</ref>. Additionally, GAC has been used for over 30 years to treat 60 million gallons per day of TCP-contaminated groundwater in Hawaii<ref name="Babcock2018">Babcock Jr, R.W., Harada, B.K., Lamichhane, K.M., and Tsubota, K.T., 2018. Adsorption of 1, 2, 3-Trichloropropane (TCP) to meet a MCL of 5 ppt. Environmental Pollution, 233, 910-915. [https://doi.org/10.1016/j.envpol.2017.09.085  DOI: 10.1016/j.envpol.2017.09.085]</ref>.
+The U.S. Department of Defense’s Environmental Security Technology Certification Program (ESTCP) supported an OPTICS demonstration study at the Pearl Harbor Sediment Site, Hawaii, to determine whether stormwater from Oscar 1 Pier outfall is a contributing source of PCBs to Decision Unit (DU) N-2 (ESTCP Project ER21-5021). High spatial resolution results afforded by ship-based, mobile OPTICS monitoring suggested that PCBs were discharged from the outfall, remained in suspension, and dispersed elsewhere before settling (Figure 5). More details regarding this study were presented by Chang et al. in 2024<ref name="ChangEtAl2024"/>.
-GAC has a low to moderate adsorption capacity for TCP, which can necessitate larger treatment systems and result in higher treatment costs relative to other organic contaminants<ref name="USEPA2017"/>.  Published Freundlich adsorption isotherm parameters<ref name="SnoeyinkSummers1999">Snoeyink, V.L. and Summers, R.S, 1999. Adsorption of Organic Compounds (Chapter 13), In: Water Quality and Treatment, 5th ed., Letterman, R.D., editor.  McGraw-Hill, New York, NY. ISBN 0-07-001659-3</ref> indicate that less TCP mass is adsorbed per gram of carbon compared to other volatile organic compounds (VOCs), resulting in increased carbon usage rate and treatment cost.  Recent bench-scale studies indicate that subbituminous coal-based GAC and coconut shell-based GAC are the most effective types of GAC for treatment of TCP in groundwater<ref name="Babcock2018"/><ref name="Knappe2017">Knappe, D.R.U., Ingham, R.S., Moreno-Barbosa, J.J., Sun, M., Summers, R.S., and Dougherty, T., 2017. Evaluation of Henry’s Law Constants and Freundlich Adsorption Constants for VOCs. Water Research Foundation Project 4462 Final Report. [https://www.waterrf.org/research/projects/evaluation-henrys-law -constant-and-freundlich-adsorption-constant-vocs  Website]</ref>. To develop more economical and effective treatment approaches, further treatability studies with site groundwater (e.g., rapid small-scale column tests) may be needed.
+==Summary==
+OPTICS provides:
-===''In Situ'' Treatment===
+*High resolution surface water chemical contaminant characterization
-''In situ'' treatment of TCP to concentrations below current regulatory or advisory levels is difficult to achieve in both natural and engineered systems. However, several ''in situ'' treatment technologies have demonstrated promise for TCP remediation, including chemical reduction by zero-valent metals (ZVMs), chemical oxidation with strong oxidizers, and anaerobic bioremediation<ref name="Merrill2019"/><ref name="Tratnyek2010"/>.
+*Cost-effective monitoring and assessment
+*Versatile and modular monitoring with capability for real-time telemetry
-===''In Situ'' Chemical Reduction (ISCR)===
+*Data necessary for development and validation of conceptual site models
-Reduction of TCP under conditions relevant to natural attenuation has been observed to be negligible. Achieving significant degradation rates of TCP requires the addition of a chemical reductant to the contaminated zone<ref name="Merrill2019"/><ref name="Tratnyek2010"/>.  Under reducing environmental conditions, some ZVMs have demonstrated the ability to reduce TCP all the way to [[wikipedia:Propene | propene]]. As shown in Figure 2, the desirable pathway for reduction of TCP is the formation of [[Wikipedia: Allyl_chloride | 3-chloro-1-propene (also known as allyl chloride)]] via [[Biodegradation_-_Reductive_Processes#Dihaloelimination | dihaloelimination]], which is then rapidly reduced to propene through [[Wikipedia:Hydrogenolysis |  hydrogenolysis]] <ref name="Merrill2019"/><ref name="Tratnyek2010"/><ref name="Torralba-Sanchez2020">Torralba-Sanchez, T.L., Bylaska, E.J., Salter-Blanc, A.J., Meisenheimer, D.E., Lyon, M.A., and Tratnyek, P.G., 2020. Reduction of 1, 2, 3-trichloropropane (TCP): pathways and mechanisms from computational chemistry calculations. Environmental Science: Processes and Impacts, 22(3), 606-616. [https://doi.org/10.1039/C9EM00557A DOI: 10.1039/C9EM00557A]&nbsp;&nbsp [[Media: Torralba-Sanchez2020.pdf | Open Access Article]]</ref>.  ZVMs including granular zero-valent iron (ZVI), nano ZVI, [[wikipedia: In_situ_chemical_reduction#Bimetallic%20materials | palladized nano ZVI]], and [[wikipedia: In_situ_chemical_reduction#Zero_valent_metals_%28ZVMs%29 | zero-valent zinc (ZVZ)]] have been evaluated by researchers<ref name="Merrill2019"/><ref name="Tratnyek2010"/>.
+*A key line of evidence for designing and evaluating remedies.
-ZVI is a common reductant used for ISCR and, depending on the form used, has shown variable levels of success for TCP treatment. The Strategic Environmental Research and Development Program (SERDP) Project ER-1457 measured the TCP degradation rates for various forms of ZVI and ZVZ.  Nano-scale ZVI and palladized ZVI increased the TCP reduction rate over that of natural attenuation, but the reaction is not anticipated to be fast enough to be useful in typical remediation applications<ref name="Sarathy2010"/>.
-Commercial-grade zerovalent zinc (ZVZ) on the other hand is a strong reductant that reduces TCP relatively quickly under a range of laboratory and field conditions to produce propene without significant accumulation of intermediates<ref name="Sarathy2010"/><ref name="Salter-BlancTratnyek2011">Salter-Blanc, A.J. and Tratnyek, P.G., 2011. Effects of Solution Chemistry on the Dechlorination of 1,2,3-Trichloropropane by Zero-Valent Zinc. Environmental Science and Technology, 45(9), pp 4073–4079. [https://doi.org/10.1021/es104081p DOI: 10.1021/es104081p]&nbsp;&nbsp; [[Media: Salter-BlancTratnyek2011.pdf | Open access article]]</ref><ref name="Salter-Blanc2012">Salter-Blanc, A.J., Suchomel, E.J., Fortuna, J.H., Nurmi, J.T., Walker, C., Krug, T., O'Hara, S., Ruiz, N., Morley, T. and Tratnyek, P.G., 2012. Evaluation of Zerovalent Zinc for Treatment of 1,2,3-Trichloropropane‐Contaminated Groundwater: Laboratory and Field Assessment. Groundwater Monitoring and Remediation, 32(4), pp.42-52. [https://doi.org/10.1111/j.1745-6592.2012.01402.x DOI: 10.1111/j.1745-6592.2012.01402.x]</ref><ref name="Merrill2019"/>. Of the ZVMs tested as part of SERDP Project ER-1457, ZVZ had the fastest degradation rates for TCP<ref name="Tratnyek2010"/>. In bench-scale studies, TCP was reduced by ZVZ to propene with 3-chloro-1-propene as the only detectable chlorinated intermediate, which was short-lived and detected only at trace concentrations<ref name="Torralba-Sanchez2020"/>.
-Navy Environmental Sustainability Development to Integration (NESDI) Project 434 conducted bench-scale testing which demonstrated that commercially available ZVZ was effective for treating TCP. Additionally, this project evaluated field-scale ZVZ column treatment of groundwater impacted with TCP at Marine Corps Base Camp Pendleton (MCBCP) in Oceanside, California. This study reported reductions of TCP concentrations by up to 95% which was maintained for at least twelve weeks with influent concentrations ranging from 3.5 to 10 µg/L, without any significant secondary water quality impacts detected<ref name="Salter-Blanc2012"/>.
-Following the column study, a 2014 pilot study at MCBCP evaluated direct injection of ZVZ with subsequent monitoring. Direct injection of ZVZ was reportedly effective for TCP treatment, with TCP reductions ranging from 90% to 99% in the injection area. Concentration reduction downgradient of the injection area ranged from 50 to 80%. TCP concentrations have continued to decrease, and reducing conditions have been maintained in the aquifer since injection, demonstrating the long-term efficacy of ZVZ for TCP reduction<ref name="Kane2020"/>.
-Potential ''in situ'' applications of ZVZ include direct injection, as demonstrated by the MCBCP pilot study, and permeable reactive barriers (PRBs). Additionally, ZVZ could potentially be deployed in an ''ex situ'' flow-through reactor, but the economic feasibility of this approach would depend in part on the permeability of the aquifer and in part on the cost of the reactor volumes of ZVZ media necessary for complete treatment.
+Because OPTICS monitoring involves deployment of autonomous sampling instrumentation, a substantially greater volume of data can be collected using this technique compared to traditional sampling, and at a far lower cost. A large volume of data supports evaluation of chemical contaminant concentrations over a range of spatial and temporal scales, and the system can be customized for a variety of environmental applications. OPTICS helps quantify contaminant mass flux and the relative contribution of local transport and source areas to net contaminant transport. OPTICS delivers a strong line of evidence for evaluating contaminant sources, fate, and transport, and for supporting the design of a remedy tailored to address site-specific, risk-driving conditions. The improved understanding of site processes aids in the development of mitigation measures that minimize site risks.
-===''In Situ'' Chemical Oxidation (ISCO)===
-Chemical oxidation of TCP with mild oxidants such as permanganate or ozone is ineffective. However, stronger oxidants (e.g. activated peroxide and persulfate) can effectively treat TCP, although the rates are slower than observed for most other organic contaminants<ref name="Tratnyek2010"/><ref name="CalEPA2017"/>. [[Wikipedia: Fenton's reagent | Fenton-like chemistry]] (i.e., Fe(II) activated hydrogen peroxide) has been shown to degrade TCP in the laboratory with half-lives ranging from 5 to 10 hours<ref name="Tratnyek2010"/>, but field-scale demonstrations of this process have not been reported. Treatment of TCP with heat-activated or base-activated persulfate is effective but secondary water quality impacts from high sulfate may be a concern at some locations.
-===Aerobic Bioremediation===
-No naturally occurring microorganisms have been identified that degrade TCP under aerobic conditions<ref name="SaminJanssen2012"/>. Relatively slow aerobic cometabolism by the ammonia oxidizing bacterium [[Wikipedia: Nitrosomonas europaea | Nitrosomonas europaea]] and other populations has been reported<ref name="Vanelli1990">Vannelli, T., Logan, M., Arciero, D.M., and Hooper, A.B., 1990. Degradation of Halogenated Aliphatic Compounds by the Ammonia-Oxidizing Bacterium Nitrosomonas europaea. Applied and Environmental Microbiology, 56(4), pp. 1169–1171. [https://doi.org/10.1128/aem.56.4.1169-1171.1990 DOI: 10.1128/aem.56.4.1169-1171.1990] Free download from: [https://journals.asm.org/doi/epdf/10.1128/aem.56.4.1169-1171.1990 American Society of Microbiology]&nbsp;&nbsp; [[Media: Vannelli1990.pdf | Report.pdf]]</ref><ref name="SaminJanssen2012"/>, and genetic engineering has been used to develop organisms capable of utilizing TCP as a sole carbon source under aerobic conditions<ref name="Bosma2002">Bosma, T., Damborsky, J., Stucki, G., and Janssen, D.B., 2002. Biodegradation of 1,2,3-Trichloropropane through Directed Evolution and Heterologous Expression of a Haloalkane Dehalogenase Gene. Applied and Environmental Microbiology, 68(7), pp. 3582–3587. [https://doi.org/10.1128/AEM.68.7.3582-3587.2002 DOI: 10.1128/AEM.68.7.3582-3587.2002] Free download from: [https://journals.asm.org/doi/epub/10.1128/AEM.68.7.3582-3587.2002 American Society for Microbiology]&nbsp;&nbsp; [[Media: Bosma2002.pdf | Report.pdf]]</ref><ref name="SaminJanssen2012"/><ref name="JanssenStucki2020">Janssen, D. B., and Stucki, G., 2020. Perspectives of genetically engineered microbes for groundwater bioremediation. Environmental Science: Processes and Impacts, 22(3), pp. 487-499. [https://doi.org/10.1039/C9EM00601J DOI: 10.1039/C9EM00601J] Open access article from: [https://pubs.rsc.org/en/content/articlehtml/2020/em/c9em00601j Royal Society of Chemistry]&nbsp;&nbsp; [[Media: JanssenStucki2020.pdf | Report.pdf]]</ref>.
-===Anaerobic Bioremediation===
-Like other CVOCs, TCP has been shown to undergo biodegradation under anaerobic conditions via reductive dechlorination by [[Wikipedia:Dehalogenimonas | Dehalogenimonas (Dhg)]] species<ref name="Merrill2019"/><ref name="Yan2009">Yan, J., B.A. Rash, F.A. Rainey, and W.M. Moe, 2009. Isolation of novel bacteria within the Chloroflexi capable of reductive dechlorination of 1,2,3-trichloropropane. Environmental Microbiology, 11(4), pp. 833–843. [https://doi.org/10.1111/j.1462-2920.2008.01804.x DOI: 10.1111/j.1462-2920.2008.01804.x]</ref><ref name="Bowman2013">Bowman, K.S., Nobre, M.F., da Costa, M.S., Rainey, F.A., and Moe, W.M., 2013. Dehalogenimonas alkenigignens sp. nov., a chlorinated-alkane-dehalogenating bacterium isolated from groundwater. International Journal of Systematic and Evolutionary Microbiology, 63(Pt_4), pp. 1492-1498. [https://doi.org/10.1099/ijs.0.045054-0 DOI: 10.1099/ijs.0.045054-0]  Free access article from: [https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.045054-0?crawler=true Microbiology Society]&nbsp;&nbsp; [[Media: Bowman2013.pdf | Report.pdf]]</ref><ref name="Loffler1997">Loffler, F.E., Champine, J.E., Ritalahti, K.M., Sprague, S.J. and Tiedje, J.M., 1997. Complete Reductive Dechlorination of 1, 2-Dichloropropane by Anaerobic Bacteria. Applied and Environmental Microbiology, 63(7), pp.2870-2875. Free download from: [https://journals.asm.org/doi/pdf/10.1128/aem.63.7.2870-2875.1997 American Society for Micrebiology]&nbsp;&nbsp; [[Medeia: Loffler1997.pdf | Report.pdf]]</ref><ref name="Moe2019">Moe, W.M., Yan, J., Nobre, M.F., da Costa, M.S. and Rainey, F.A., 2009. Dehalogenimonas lykanthroporepellens gen. nov., sp. nov., a reductively dehalogenating bacterium isolated from chlorinated solvent-contaminated groundwater. International Journal of Systematic and Evolutionary Microbiology, 59(11), pp.2692-2697. [https://doi.org/10.1099/ijs.0.011502-0 DOI: 10.1099/ijs.0.011502-0] Free download from: [https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.011502-0?crawler=true Microbiology Society]&nbsp;&nbsp; [[Media: Moe2009.pdf | Report.pdf]]</ref><ref name="SaminJanssen2012"/>. However, the kinetics are slower than for other CVOCs.  Bioaugmentation cultures containing Dehalogenimonas (KB-1 Plus, SiREM) are commercially available and have been implemented for remediation of TCP-contaminated groundwater<ref name="Schmitt2017">Schmitt, M., Varadhan, S., Dworatzek, S., Webb, J. and Suchomel, E., 2017. Optimization and validation of enhanced biological reduction of 1,2,3-trichloropropane in groundwater. Remediation Journal, 28(1), pp.17-25. [https://doi.org/10.1002/rem.21539 DOI: 10.1002/rem.21539]</ref>. One laboratory study examined the effect of pH on biotransformation of TCP over a wide range of TCP concentrations (10 to 10,000 µg/L) and demonstrated that successful reduction occurred from a pH of 5 to 9, though optimal conditions were from pH 7 to 9<ref name="Schmitt2017"/>.
-As with other microbial cultures capable of reductive dechlorination, coordinated amendment with a fermentable organic substrate (e.g. lactate or vegetable oil), also known as biostimulation,  creates reducing conditions in the aquifer and provides a source of hydrogen which is required as the primary electron donor for reductive dechlorination.
-A 2016 field demonstration of ''in situ'' bioremediation (ISB) was performed in California’s Central Valley at a former agricultural chemical site with relatively low TCP concentrations (2 µg/L). The site was first biostimulated by injecting amendments of emulsified vegetable oil (EVO) and lactate, which was followed by bioaugmentation with a microbial consortium containing Dhg. After an initial lag period of six months, TCP concentrations decreased to below laboratory detection limits (<0.005 µg/L)<ref name="Schmitt2017"/>.
-The 2016 field demonstration was expanded to full-scale treatment in 2018 with biostimulation and bioaugmentation occurring over several months. The initial TCP concentration in performance monitoring wells ranged from 0.008 to 1.7 µg/L. As with the field demonstration, a lag period of approximately 6 to 8 months was observed before TCP was degraded, after which concentrations declined over fifteen months to non-detectable levels (less than 0.005 µg/L). TCP degradation was associated with increases in Dhg population and propene concentration. Long term monitoring showed that TCP remained at non-detectable levels for at least three years following treatment implementation<ref name="Merrill2019"/>.
-==Treatment Comparisons and Considerations==
-When selecting a technology for TCP treatment, considerations include technical feasibility, ability to treat to regulated levels, potential secondary water quality impacts and relative costs. A comparison of some TCP treatment technologies is provided in Table 2.
-{| class="wikitable" style="float:right; margin-left:10px;text-align:center;"
-|+Table 2.  Advantages and limitations of TCP treatment technologies<ref name="Kane2020"/>
-|-
-! Technology
-! Advantages
-! Limitations
-|-
-| ZVZ
-| style="text-align:left;" |
-* Can degrade TCP at relatively high and low concentrations
-* Faster reaction rates than ZVI
-* Material is commercially available
-| style="text-align:left;" |
-* Higher cost than ZVI
-* Difficult to distribute in subsurface ''in situ'' applications
-|-
-| Groundwater</br>Extraction and</br>Treatment
-| style="text-align:left;" |
-* Can cost-effectively capture and treat larger, more dilute</br>groundwater plumes than ''in situ'' technologies
-* Well understood and widely applied technology
-| style="text-align:left;" |
-* Requires construction, operation and maintenance of</br>aboveground treatment infrastructure
-* Typical technologies (e.g. GAC) may be expensive due</br>to treatment inefficiencies
-|-
-| ZVI
-| style="text-align:left;" |
-* Can degrade TCP at relatively high and low concentrations
-* Lower cost than ZVZ
-* Material is commercially available
-| style="text-align:left;" |
-* Lower reactivity than ZVZ, therefore may require higher</br>ZVI volumes or thicker PRBs
-* Difficult to distribute in subsurface ''in situ'' applications
-|-
-| ISCO
-| style="text-align:left;" |
-* Can degrade TCP at relatively high and low concentrations
-* Strategies to distribute amendments ''in situ'' are well established
-* Material is commercially available
-| style="text-align:left;" |
-* Most effective oxidants (e.g., base-activated or heat-activated</br>persulfate) are complex to implement
-* Secondary water quality impacts (e.g., high pH, sulfate, </br>hexavalent chromium) may limit ability to implement
-|-
-| ''In Situ''</br>Bioremediation
-| style="text-align:left;" |
-* Can degrade TCP at moderate to high concentrations
-* Strategies to distribute amendments ''in situ'' are well established
-* Materials are commercially available and inexpensive
-| style="text-align:left;" |
-* Slower reaction rates than ZVZ or ISCO
-|}
-==Summary==
-The relatively high toxicity of TCP has led to the development of health-based drinking water concentration values that are very low. TCP is sometimes present in groundwater and in public water systems at concentrations that exceed these health-based goals. While a handful of states have established MCLs for TCP, US federal regulatory determination is hindered by the lack of low-concentration occurrence data. Because TCP is persistent in groundwater and resistant to typical remediation methods (or costly to treat), specialized strategies may be needed to meet drinking-water-based treatment goals.  ''In situ'' chemical reduction (ISCR) with zero valent zinc (ZVZ) and ''in situ'' bioremediation have been demonstrated to be effective for TCP remediation.
 ==References==
@@ Line 178: / Line 66: @@
 ==See Also==
-ATSDR Toxicological Profile: https://www.atsdr.cdc.gov/ToxProfiles/TP.asp?id=912&tid=186
-EPA Technical Fact Sheet: https://www.epa.gov/sites/production/files/2014-03/documents/ffrrofactsheet_contaminant_tcp_january2014_final.pdf
-Cal/EPA State Water Resources Control Board Groundwater Information Sheet: http://www.waterboards.ca.gov/gama/docs/coc_tcp123.pdf
-California Water Boards Fact Sheet: http://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/123-tcp/123tcp_factsheet.pdf

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Assessing Vapor Intrusion (VI) Impacts in Neighborhoods with Groundwater Contaminated by Chlorinated Volatile Organic Chemicals (CVOCs)

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