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Unintentional contaminant transfer from groundwater to the vadose zone via gas exsolution and ebullition… Chong, Andrea Denise 2016

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 UNINTENTIONAL CONTAMINANT TRANSFER FROM GROUNDWATER TO THE VADOSE ZONE VIA GAS EXSOLUTION AND EBULLITION DURING REMEDIATION OF VOLATILE ORGANIC COMPOUNDS by Andrea Denise Chong A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF  THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF SCIENCE in The Faculty of Graduate and Postdoctoral Studies (Geological Sciences)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver)  February 2016 © Andrea Denise Chong, 2016  ii Abstract Historical heavy use of chlorinated solvents in conjunction with improper disposal practices and accidental releases has resulted in widespread contamination of soils and groundwater in North America. As a result, remediation of chlorinated solvents is required at many sites. For treatment of source zone contamination, common remediation strategies include in situ chemical oxidation (ISCO) using potassium or sodium permanganate, and the enhancement of biodegradation by primary substrate addition. It is well known that these remediation methods tend to generate gas (carbon dioxide (CO2) in the case of ISCO using permanganate, CO2 and methane (CH4) in the case of bioremediation). It is hypothesized that the generation of gas in the presence of volatile organic compounds (VOCs), including chlorinated solvents, may lead to stripping of the contaminants from the source zone due to gas exsolution and ebullition. This process may lead to ‘compartment transfer’, whereby contaminants are transported away from the saturated zone into the vadose zone, with possible implications for soil vapour intrusion. Two sites in the U.S. undergoing enhanced bioremediation have exhibited behavior suggestive of contaminant transfer into the vadose zone via gas generated during remediation. These sites provided the impetus for a more in-depth investigation into this process.  To this extent, benchtop column experiments were conducted to observe the effect of gas generation during remediation of the common chlorinated solvent trichloroethylene (TCE/C2Cl3H). Two common in situ treatment strategies were simulated for source-zone subsurface contamination of TCE, including ISCO and enhanced bioremediation.   iii Results confirm that these aggressive remediation methods can lead to gas production and induce vertical transport of contaminants away from the treatment zone, following the formation of a discontinuous gas phase (bubbles). The generation of gas and the potential for unintentional contaminant stripping and transport should be taken into consideration when treating VOCs to avoid release into the atmosphere or into underground structures via soil vapour intrusion. This study also suggests that the suitability of gas-generating remediation techniques in proximity to buildings and in populated areas should be evaluated with care.     iv Preface This thesis is original, unpublished work. Experimental design by the author and Dr. K Ulrich Mayer. All samples were collected and analyzed by the author. All chapters were written by the author and edited by Dr. K Ulrich Mayer.     v Table of Contents  Abstract ................................................................................................................................ ii Preface ................................................................................................................................. iv Table of Contents .................................................................................................................. v List of Tables ....................................................................................................................... viii List of Figures ....................................................................................................................... ix List of Supplementary Materials ...........................................................................................xii Acknowledgements ............................................................................................................. xiii Chapter 1: Introduction ...................................................................................................... 1 1.1 Overview ............................................................................................................................ 1 1.2 Background......................................................................................................................... 1 1.2.1 Historical use of chlorinated solvents ......................................................................... 1 1.2.2 TCE contamination ...................................................................................................... 2 1.3 TCE remediation ................................................................................................................. 5 1.3.1 Pump and treat vs. in situ remediation ....................................................................... 5 1.3.2 ISCO ............................................................................................................................. 6 1.3.3 Enhanced bioremediation ........................................................................................... 7 1.4 Gas exsolution and ebullition ........................................................................................... 10 1.5 NAPL mass transfer .......................................................................................................... 12 1.6 Experimental overview .................................................................................................... 13 1.6.1 Hypothesis ................................................................................................................. 13 1.6.2 Field sites ................................................................................................................... 13 1.6.3 Potential impacts ....................................................................................................... 14 1.7 Figures .............................................................................................................................. 16 1.8 Tables ............................................................................................................................... 18 Chapter 2: Methods .......................................................................................................... 19 2.1 Overview .......................................................................................................................... 19 2.2 Experimental design ......................................................................................................... 19 2.2.1 Batch reactors ............................................................................................................ 19 2.2.2 Column design ........................................................................................................... 21 2.2.3 Column filling ............................................................................................................. 23  vi 2.2.4 ISCO column treatment ............................................................................................. 25 2.2.5 Enhanced bioremediation column treatment ........................................................... 26 2.2.6 Control column .......................................................................................................... 27 2.3 Column monitoring and sampling .................................................................................... 29 2.4 Sample analysis ................................................................................................................ 31 2.5 Figures .............................................................................................................................. 32 2.6 Tables ............................................................................................................................... 39 Chapter 3: Results and discussion ..................................................................................... 40 3.1 Results .............................................................................................................................. 40 3.1.1 Chapter overview ...................................................................................................... 40 3.1.2 Control column .......................................................................................................... 40 3.1.3 ISCO experiment ........................................................................................................ 41 3.1.3.1  Observations ...................................................................................................... 41 3.1.3.2  Gas production ................................................................................................... 42 3.1.3.3  Gas profiles ........................................................................................................ 43 3.1.3.4  TCE treatment .................................................................................................... 46 3.1.3.5  TCE in the column .............................................................................................. 46 3.1.3.6  TCE in the headspace ......................................................................................... 47 3.1.4 Enhanced bioremediation experiment ..................................................................... 49 3.1.4.1  Batch reactors .................................................................................................... 49 3.1.4.2  Column observations ......................................................................................... 50 3.1.4.3  Gas production ................................................................................................... 51 3.1.4.4  Gas profiles ........................................................................................................ 52 3.1.4.5  TCE treatment .................................................................................................... 54 3.1.4.6  VOCs in the column ............................................................................................ 57 3.1.4.7  VOCs in the headspace ...................................................................................... 58 3.2 Discussion ......................................................................................................................... 59 3.2.1 TCE treatment............................................................................................................ 59 3.2.1.1  ISCO column ....................................................................................................... 59 3.2.1.2  Bioremediation column ..................................................................................... 59 3.2.2 Gas transport ............................................................................................................. 61 3.2.3 VOC transport ............................................................................................................ 61 3.2.4 Diffusion .................................................................................................................... 64 3.3 Significance of findings ..................................................................................................... 65 3.3.1 VOC transport ............................................................................................................ 65 3.3.2 Soil vapour intrusion and indoor air concentrations ................................................ 67 3.4 Field sites .......................................................................................................................... 67 3.4.1 Applying experimental findings to a field scenario ................................................... 67  vii 3.4.2 Bozeman Solvent Site ................................................................................................ 68 3.4.3 Oregon site ................................................................................................................ 69 3.5 Impacts ............................................................................................................................. 70 3.6 Figures .............................................................................................................................. 71 3.7 Tables ............................................................................................................................... 99 Chapter 4: Conclusions and recommendations ................................................................ 104 4.1 Conclusions .................................................................................................................... 104 4.2 Recommendations ......................................................................................................... 107 4.2.1 Experimental work .................................................................................................. 107 4.2.2 Remediation sites .................................................................................................... 107 Bibliography ...................................................................................................................... 108 Appendices ....................................................................................................................... 117 Appendix A: Sample analysis ................................................................................................... 117 Appendix B: ISCO data ............................................................................................................. 118 Appendix C: Enhanced bioremediation column data ............................................................. 123       viii List of Tables Table 1.1- Henry’s Constants and Bunsen Coefficients ................................................................ 18 Table 2.1- Batch reactor contents ................................................................................................ 39 Table 3.1- Gas loss estimates from sampling events, ISCO column ............................................. 99 Table 3.2- Substrate addition schedule for batch reactors ........................................................ 100 Table 3.3- Gas production from batch reactors ......................................................................... 101 Table 3.4- Gas loss estimates for bioremediation column ......................................................... 102 Table 3.5- CO2 and CH4 in column at day 175 ............................................................................. 102 Table 3.6- Bozeman Solvent Site highest reported soil vapour concentrations before and after enhanced bioremediation pilot test ........................................................................................... 102 Table 3.7- Oregon industrial site soil vapour and indoor air concentrations before and during enhanced bioremediation treatment ......................................................................................... 103    ix List of Figures Figure 1.1- Reaction pathway showing sequential reductive dechlorination of TCE during co-metabolism. .................................................................................................................................. 16 Figure 1.2- Conceptual model of VOC transport via gas exsolution and ebullition. .................... 17 Figure 2.1- Glass pressure vessel for batch reactor, with pressure transducer attached to lid... 32 Figure 2.2- Column design schematic. .......................................................................................... 33 Figure 2.3- Sampling port design (top) and assembly (photos). ................................................... 34 Figure 2.4- Flexible syringes used for sampling through ports. .................................................... 35 Figure 2.5- Column stand with empty columns. Sampling ports are not attached, and pressure transducers are absent. ................................................................................................................ 36 Figure 2.6- Column design, indicating column fill and placement of sampling ports .................. 37 Figure 2.7- Injection of TCE into target zone of ISCO column. ..................................................... 38 Figure 2.8- Contamination spread following TCE injection on control (left), ISCO (middle), and bioremediation (right) columns, prior to treatment application. ................................................ 38 Figure 3.1- TCE concentrations from the h = 13 cm port on the control column. ....................... 71 Figure 3.2- Measured TCE concentrations from the h = 13 cm port on the control column, with simulated diffusion (orange dashed line) using a diffusion coefficient of 2.6 × 10-11 m2/s and a Fickian diffusion model. ................................................................................................................ 71 Figure 3.3- Permanganate pooling in the bottom of the column following injection to the treatment zone of the ISCO column. ............................................................................................ 72 Figure 3.4- Screenshots from video clip showing TCE treatment and movement following injection of permanganate, approximately 30 minutes after injection. ...................................... 73 Figure 3.5- Example of temporary void spaces appearing due to gas bubbles in the ISCO column, located near the 40 cm sampling port. ......................................................................................... 74 Figure 3.6- Example of TCE appearance and disappearance in the ISCO column in the gravel layer.  ............................................................................................................................................. 74 Figure 3.7- Appearance of the treatment zone in the ISCO column, 44 days following permanganate injection, showing precipitated manganese oxide solids. ................................... 75 Figure 3.8- Gas production and headspace overpressure in the ISCO column. ........................... 76  x Figure 3.9- Gas production rate, calculated between each sampling event, ISCO column. ........ 77 Figure 3.10- Dissolved gas concentrations for select sampling events, ISCO column. ................ 78 Figure 3.11- Dissolved gas concentrations from h = 6.5 cm (top panel) and h = 33 cm (bottom panel), ISCO column. ..................................................................................................................... 79 Figure 3.12- Compositional gas analysis of the headspace, ISCO column. ................................... 80 Figure 3.13- TCE concentrations from aqueous samples throughout the course of the experiment on select sampling days, ISCO column. ..................................................................... 81 Figure 3.14- TCE concentration in treatment zone, ISCO column. ............................................... 82 Figure 3.15- TCE concentration in headspace, ISCO column. ....................................................... 83 Figure 3.16- Comparison of TCE concentrations at the highest aqueous port (h = 40 cm) and in the headspace, after converting headspace concentrations to equivalent aqueous concentrations. ............................................................................................................................. 83 Figure 3.17- Cumulative gas production from the batch reactors. .............................................. 84 Figure 3.18- Screenshots from a video showing a bubble emerging from the sediments in the bioremediation column on t = 72 d, with red arrow indicating location of the bubble. ............. 85 Figure 3.19- Gas production and headspace overpressure in bioremediation column. .............. 86 Figure 3.20- Gas production rate, calculated between each sampling event, bioremediation column. ......................................................................................................................................... 87 Figure 3.21- Dissolved gas profiles for select sampling events, bioremediation column. ........... 88 Figure 3.22- Dissolved gas concentrations from h = 6.5 cm (top panel) and h = 33 cm (bottom panel), bioremediation column. ................................................................................................... 89 Figure 3.23- Compositional gas analysis of the headspace, bioremediation column. ................. 90 Figure 3.24- VOC concentrations in the contamination zone, bioremediation column. ............. 91 Figure 3.25- Column segments used in calculations for TCE treatment estimate in the bioremediation column. ............................................................................................................... 92 Figure 3.26- Aqueous VOC concentrations measured in the enhanced bioremediation column throughout the course of the experiment. Scale is cut off at 25 mg/L. ....................................... 93 Figure 3.27- Aqueous VOC concentrations measured in the enhanced bioremediation column throughout the course of the experiment. Full (semi-log) scale. ................................................. 94  xi Figure 3.28- VOC concentrations from h = 13 cm (top panel) and h = 33 cm (bottom panel), bioremediation column. ............................................................................................................... 95 Figure 3.29- VOC concentrations in headspace of bioremediation column ................................ 96 Figure 3.30- Comparison of VOC concentrations at the highest aqueous port (h = 40 cm) and in the headspace, after converting headspace concentrations to equivalent aqueous concentrations. ............................................................................................................................. 96 Figure 3.31- Photos from the ISCO column deconstruction. ........................................................ 97 Figure 3.32- Estimated time for diffusive transport of TCE to the sampling ports from a source concentration at solubility in the treatment zone. ...................................................................... 98    xii List of Supplementary Materials Video 3.1 .................................................................................   http://hdl.handle.net/2429/57042   xiii Acknowledgements To Uli, thank you for your wonderful supervision, guidance, and seemingly unlimited patience and understanding. To my family, thank you for your love and encouragement.  To my fellow hydronauts, thank you for your friendship.  And to Nate, who has been by my side supporting me along every step of this thesis, this is for you. 1 Chapter 1: Introduction 1.1 Overview Groundwater remediation of organic contaminants can lead to the generation of gases such as carbon dioxide (CO2) and methane (CH4) in the subsurface (Freedman and Gossett, 1989). In the case of substantial gas generation, it has been found that gases may exsolve and form bubbles, which are subsequently released into the overlying vadose zone (Amos and Mayer, 2006a). In the case of treating volatile contaminants, it can be hypothesized that this process may also lead to the partial stripping of organic contaminants from the treatment zone. The focus of this thesis is to determine whether unintentional transfer of volatile contaminants from groundwater into the overlying vadose zone may occur during groundwater remediation. This research was conducted via benchtop column experiments using the common chlorinated solvent trichloroethylene (TCE/C2Cl3H).   1.2 Background 1.2.1 Historical use of chlorinated solvents Chlorinated compounds are some of the most widely used household and industrial solvents in North America. Historic applications include degreasing, dry-cleaning, and industrial processing, and compounds such as TCE have been used heavily in the electronics, defense, food processing, textiles, pharmaceuticals, and transportation industries (Doherty, 2000). Useful industrially due to its rapid evaporation rate and low reactivity, at the peak of its popularity in the late 1960s and early 1970s the United States was producing more than 600  2 million pounds of TCE annually (Doherty, 2000). Although industrially useful, TCE exposure has been connected to numerous health issues including central nervous system, liver, kidney, endocrine, and respiratory problems, as well as increased carcinogenic risk, negative effects on fetal development, and reduced fertility (United States Environmental Protection Agency (US EPA), 2007). Largely due to the discovery of human health problems and environmental hazards and the subsequently introduced regulations, current annual TCE production in the United States is much lower than in the past, closer to 300 million pounds (Agency for Toxic Substances and Disease Registry (ATSDR), 2014).  1.2.2 TCE contamination Historical heavy use in conjunction with improper disposal practices and accidental releases has resulted in widespread contamination of soils and groundwater with TCE. TCE contamination in North America is a multi-billion dollar problem; more than 1000 of the 1699 current or former National Priorities List Superfund sites classified by the U.S. Environmental Protection Agency (considered the most crucial hazardous waste sites for federal environmental cleanup in the U.S.) have been identified as containing TCE (US EPA, 2015). Currently regulated under the Safe Drinking Water Act in the United States and the Canadian Environmental Protection Act in Canada, the maximum acceptable concentration for TCE in drinking water in both countries is 0.005 mg/L (Health Canada, 2005; US EPA).  Sites containing chlorinated solvents tend to be characterized by complex dispersal of contaminants; TCE is a dense non-aqueous phase liquid (DNAPL) that is also a volatile organic compound (VOC), and will migrate in the subsurface via a variety of pathways that can be  3 difficult to predict due to subsurface heterogeneities. Once released, downward flow of DNAPLs is controlled by gravitational, capillary, and viscous forces, resulting in the formation of DNAPL pools along capillary interfaces as well as the deposition of residual product left behind in pore spaces (Schwille, 1988). Although DNAPLs are immiscible with water and exist as a separate liquid phase, many have solubility limits that are orders of magnitude in excess of water quality standards. Residual product and pools of DNAPL will act as long term sources for dissolved compounds in groundwater. The solubility of TCE at 25°C is 1.28 g/L, more than 5 orders of magnitude higher than the drinking water standard of 0.005 mg/L (National Institute of Standards and Technology (NIST), 2015). As such, the fate of both pure phase and dissolved TCE must be considered at a contaminated site. Increased complexity is added when volatile contaminants are involved; as a VOC, TCE will also partition into the gas phase.  In a multi-phase system, the partitioning of contaminants between the gaseous and aqueous phases at a specific temperature is defined by Henry’s Law: 𝑝𝑔 = 𝐾𝐻𝐶 where pg is the partial pressure of the compound in the gas phase, KH is the Henry’s Law Constant for the compound, and C is the concentration of the compound in the aqueous phase. The typically used units of the Henry’s Law Constant KH are m3∙atm∙mol-1. The partitioning can also be expressed using a dimensionless Henry’s Constant: 𝐻 =𝐶𝑔𝐶𝑤  4 where H is the dimensionless Henry’s Constant, and Cg and Cw are the concentrations of the compound in the gas and aqueous phases, respectively (both in units of mol/m3). The dimensionless Henry’s Constant for TCE at 20°C is approximately 0.41, based on a compilation of available data by the Max-Planck Institute of Chemistry (Sander, 1999). The partitioning of contaminants between the gas and multicomponent pure phases will be controlled by Raoult’s Law: 𝑝𝑖 = 𝑝𝑖∗𝑥𝑖  where pi is the partial pressure of the compound i in the gas phase, pi* is the vapour pressure of the compound i in its pure form, and xi is the molar fraction of the compound i in the mixture. The vapour pressure of pure TCE is 9.74 × 10-2 atm at 25°C (ATSDR, 2014). The potential for volatile contaminants to partition into the vapour phase in contact with a DNAPL pool, residual product, or dissolved plume at a contaminated site is important for characterizing the extent of the contamination; once in the vadose zone contaminants can travel rapidly towards the atmosphere or into underground structures such as basements. The likelihood of soil vapour intrusion into underground structures is exacerbated by the tendency for the buildup of pressure gradients between the vadose zone and basements, based on indoor/outdoor temperature differences, wind loading, and the operation of furnaces (Little et al., 1992). While advective gas flow due to these pressure gradients is the dominant mechanism for transport of volatile contaminants from the vadose zone into basements, contaminants may also diffuse into buildings through cracks or permeable walls (Garbesi and Sextro, 1989). If  5 transported to indoor environments, vapour intrusion of VOCs poses a risk to human health via inhalation. 1.3 TCE remediation 1.3.1 Pump and treat vs. in situ remediation Due to the widespread nature of TCE contamination in North America, considerable research has been completed in the last 30 years to develop strategies to remediate TCE-contaminated sites. Conventional pump-and-treat systems, the most widely used strategy for groundwater remediation, can be difficult to apply to TCE-contaminated aquifers (Hoffman, 1993; Mackay and Cherry, 1989). There can be significant uncertainty surrounding the location and extent of DNAPL pools even in relatively homogeneous aquifers; this uncertainty is vastly increased for locating DNAPL pools in fractured or heterogeneous aquifers. Locating and removing DNAPLs in the subsurface via pumping is difficult and recovery tends to be low when this is attempted (Mackay and Cherry, 1989). During DNAPL sinking, fractures or zones of higher permeability will result in fingers of more rapid vertical flow, while layers and lenses of low permeability will cause the DNAPL to pool or spread laterally- all making accurate delineation of contamination difficult (US EPA, 1996). If the DNAPL pools cannot be accurately located, pumping from a remote well tends to be unhelpful as water will be drawn preferentially to the well. In addition, in the instances that DNAPL product is successfully pumped out of a contaminated aquifer by accurately locating DNAPL pools, residual product will remain in the subsurface and will act as a long term source for plume contamination (Michalski et al., 1995).  As an alternative, in situ remediation of TCE and other DNAPLs refers to treatment strategies  6 that are applied in the subsurface, and thus have the advantage that they do not require DNAPL to be extracted by pumping. There exist a variety of in situ remediation options, such as in situ chemical oxidation (ISCO), enhanced bioremediation, air sparging, and permeable reactive barriers, of which the first two are outlined below. 1.3.2 ISCO ISCO is a remediation method used for organic contaminants that involves redox manipulation. In this type of remediation, an oxidant solution is released into the NAPL contamination. During successful ISCO treatment, carbon-based contaminants are oxidized to carbon dioxide (CO2). Potential oxidants for ISCO treatment include hydrogen peroxide, permanganate, and ozone; the choice of oxidant depends on the target contaminant and the environmental conditions (Schnarr et al., 1998; Siegrist et al., 2008). For TCE, the most commonly used oxidant is permanganate, which has the advantages of being effective over a wide pH range, and is relatively stable in the subsurface (Yin and Allen, 1999). This can be in the form of either sodium permanganate (NaMnO4) or potassium permanganate (KMnO4), although KMnO4 tends to be used more frequently as it is a cheaper compound. Using either, the oxidation of TCE proceeds as follows: C2Cl3H + 2MnO4-  2CO2 + 2MnO2 (s) + 3Cl- + H+ In experimental studies and applications at TCE-contaminated sites, permanganate oxidation has been found to be successful at effectively treating TCE contamination (Schnarr et al., 1998; West et al., 1997; Yan and Schwartz, 1999). In particular, permanganate oxidation can be very effective at treating source-zone contamination. However, as in most groundwater  7 remediation activities, ISCO must be designed on a site-specific basis and is not appropriate for all NAPL contaminated sites. Since the oxidation is not compound specific, sites that contain high amounts of naturally occurring organic carbon make poor candidates for ISCO as the oxidant will not preferentially oxidize the target compound (Yin and Allen, 1999). Additionally, there tends to be a limit to the amount of contaminant treatment that can occur in a given location; the precipitation of solid manganese oxides can reduce the permeability of a site and prevent further treatment (Schroth et al., 2001). At sites where ISCO is inappropriate to use, other remediation strategies can be employed. 1.3.3 Enhanced bioremediation Bioremediation is a strategy that encourages the growth of native microbes that can biodegrade organic constituents. Bioremediation of TCE has been thoroughly investigated in field studies after first being demonstrated on TCE in soil columns by Wilson and Wilson (1985). It has been studied under both aerobic and anaerobic conditions, whereby microbes can achieve remediation of TCE via reductive dechlorination (e.g. Freedman and Gossett, 1989; Hopkins and McCarty, 1995; McCarty et al., 1998). This is a process that occurs via co-metabolism as the TCE does not function as the primary carbon substrate, but instead the reaction is catalyzed by the production of a microbial enzyme; the microbes require an additional electron donor/primary substrate (Magnuson et al., 1998). The electron donor may be naturally occurring organic matter, organic matter from another contaminant on site, or supplied to the site via injection wells. A variety of bacteria including methanogens and sulfate reducing bacteria are capable of mediating this reaction (Bagley and Gossett, 1990). The  8 theoretical reductive dechlorination of TCE, using toluene (C7H8) as the electron donor, is shown below (National Research Council et al., 2000): C2Cl3H + 0.167C7H8 + 2.34H2O  C2H4 + 3Cl- + 3H+ + 1.17CO2 In reality, the products shown above are unlikely to appear in this exact ratio, since the reaction will often not go to completion. The transformation of TCE to ethene proceeds via the sequential dechlorination to dichloroethylene (DCE), which has three possible isomers, then vinyl chloride (VC), before ethene (Kästner, 1991). This reaction pathway is shown in Figure 1.1. The presence of any of these daughter products is likely on sites undergoing bioremediation via co-metabolism of TCE. Due to their ubiquitous nature, microbes capable of mediating the reductive dechlorination of TCE are already present within the microbial community at most sites. However, they may require stimulation in order to effectively remediate a contaminated area; this process in known as enhanced bioremediation or biostimulation (Tyagi et al., 2011). During enhanced bioremediation, some limiting compound is provided to the native microbial population via injection wells. This can include primary substrates, electron acceptors, or nutrients, depending on the site-specific requirements. Primary substrates that have been found to successfully stimulate the microbial community to co-metabolize chlorinated solvents include acetate (Lee et al., 2012; Rittmann and Seagren, 1994), phenol (Fries et al., 1997; Hopkins et al., 1993), methanol (El Mamouni et al., 2002), lactate (Ellis et al., 2000; Song et al., 2002), and vegetable oil (Hunter, 2002), amongst others. Commercial products designed specifically as primary substrates for bioremediation are also available such as Hydrogen  9 Release Compound (REGENESIS Remediation Solutions) and EOS 100 (EOS Remediation). During microbial respiration, the chemical energy within the primary carbon substrate is released, and the microbes use the released energy for metabolism and cell synthesis. The organic carbon, which acts as the electron donor, is oxidized to CO2, while the electron acceptor is reduced. In aquifers undergoing natural microbial evolution or enhanced bioremediation, redox evolution will follow the consumption of electron acceptors in a series of decreasingly energetically favourable reactions (Champ et al., 1979). The most common electron acceptors in aquifers and their associated reduced species (in their order on the thermodynamic ladder) include: O2/H2O (upper stability field of water) NO3-/N2  Mn4+/Mn2+  Fe3+/Fe2+  SO42-/HS-  CO2/CH4  H2O/H2 (lower stability field of water)  If the reductive dechlorination of TCE goes to completion, the final products are ethene and CO2, environmentally benign substances. However, the reaction proceeds in a step-wise fashion, with each reaction having different rates and kinetic limitations (Freedman and Gossett, 1989). Incomplete dechlorination of TCE is unhelpful or even harmful to cleanup efforts, since the daughter products dichloroethylene (DCE) and vinyl chloride (VC) are also regulated toxic compounds; the maximum acceptable concentration of vinyl chloride is lower than that of TCE (0.002 mg/L in comparison to 0.005 mg/L) (ATSDR, 2006). The decreasing  10 degree of chlorination of the intermediate compounds as the reaction proceeds unfortunately has the effect of producing species with a lower potential for anaerobic co-metabolism; vinyl chloride has significantly higher potential to be co-metabolized under aerobic conditions than anaerobic conditions (Norris et al., 1993). Since aquifer redox evolution does not favour returning to an aerobic state once it is anaerobic, this is a complicating factor for TCE contaminated sites undergoing bioremediation.  1.4 Gas exsolution and ebullition  Ramifications of the presence of a discontinuous gas phase (i.e. bubbles) below the water table is a topic of increasing interest in the field of groundwater contamination and remediation. The presence of gas bubbles in the saturated zone has been found to impact physical and geochemical processes in aquifers (Amos and Mayer, 2006a).  Gas may be present in the subsurface during remediation activities for a variety of reasons; it may be either biogenically derived (such as CO2 and methane (CH4) from microbial respiration), due to chemical reactions (such as the CO2 released from an ISCO treatment, or hydrogen (H2) released in a permeable reactive barrier), or due to purposeful bubbling of gas (such as during bioventing or air sparging) (e.g. Freedman and Gossett, 1989; Hopkins and McCarty, 1995; Marley et al., 1992; Yin and Allen, 1999). Atmospheric gases may also be entrapped due to fluctuations of the water table. With respect to the TCE remediation strategies presented above, CO2 is generated during ISCO, while enhanced bioremediation will generate both CO2 and CH4. As both ISCO and enhanced bioremediation are treatment strategies that can be applied to source zone contamination, these reactions tend to occur in  11 saturated conditions below the water table. The amount of released gas that remains dissolved is dependent on the gas solubility; if the gas solubility is exceeded then gas exsolution will occur. Following exsolution, gas bubbles undergo vertical transport due to buoyancy forces, in the process of ebullition. The point at which gas solubility is exceeded varies between gases and is also dependent on the pressure, temperature, and salinity of the aquifer. Generally, gas solubility will increase with increased pressure, decreased temperature, and decreased salinity (Colt, 2002). Assuming that these are equivalent, gas solubility between gases can be compared using the Henry’s Constants (specified for a given temperature) or the Bunsen Coefficients (specified for STP). These parameters are shown in Table 1.1 for gases relevant to TCE remediation (Colt, 2002; Sander, 1999). The gas-water partitioning controls exsolution, for example, as the solubility of CO2 is significantly higher than that of CH4, CH4 will reach saturation and exsolve at lower gas concentrations.  Both nitrogen (N2) and argon (Ar) are atmospheric gases that can be considered nonreactive and conservative in many cases. This is not necessarily the case for all aquifers, such as those with denitrifying bacterial communities (Böttcher et al., 1990).  Concentrations of nonreactive gases can be used as tracers of biogenic gas production. As gases are produced in the treatment zone of a contaminated aquifer, the nonreactive gases are stripped. This evolution of dissolved gas ratios is used to trace biogenic gas production in aquifers (Blicher-Mathiesen et al., 1998).     12 1.5 NAPL mass transfer Our understanding of NAPL mass transfer from the pure phase to a dissolved plume has been greatly enhanced by detailed experiments and high-resolution field investigations such as those conducted at the Borden site in Ontario (e.g. Frind et al., 1999) and the Milford site in New Hampshire (e.g. Guilbeault et al., 2005).  Although it has received less attention, there has also been research into mass transfer of NAPL compounds into a continuous gas phase in the unsaturated zone (e.g. Bohy et al., 2006) and from the gas phase downwards to the saturated zone (Jellali et al., 2003). Mass transfer into a continuous gas phase (such as the unsaturated zone or the atmosphere) will be followed by advective and dispersive transport of the compound; however, mass transfer into a discontinuous gas phase is less well understood. Research investigating the transfer of mass from pure or dissolved phases into a discontinuous gas phase is an area which has recently started to receive interest. Using saturated columns under stagnant methanogenic conditions, Amos and Mayer (2006a) demonstrated ebullition as the primary transport mechanism for biogenically produced methane. In the presence of discontinuous gas phase ‘seeds’, NAPL compounds and atmospheric gasses were found to partition to the gas phase and affect vertical mobilization of the gas clusters (Mumford et al., 2008; Roy and Smith, 2007). In two-dimensional flow cells, Mumford et al. (2009) demonstrated that when a seed gas phase of atmospheric gasses trapped by fluctuating the water table exists above a DNAPL pool, the volatilization of the DNAPL results in vertical growth of discontinuous gas fingers. In this case no biogenically produced gas was allowed to form, achieved by the injection of a biocide.  13 1.6 Experimental overview 1.6.1 Hypothesis Currently, no research has been published investigating the mass transfer of volatile DNAPL compounds into a discontinuous gas phase generated as a byproduct of in situ DNAPL remediation techniques, and the potential for subsequent transport of the volatiles during ebullition. Volatile compound partitioning from the pure phase or dissolved phase into gas bubbles, or compartment transfer, has the potential to impact contaminant transport, particularly with respect to sites with (1) high rates of bubble formation and ebullition from biogenic or chemical gas production, and (2) high concentrations of volatile contaminants. Both of these conditions are met during TCE source zone remediation via ISCO or enhanced bioremediation, where gas is being generated in the immediate vicinity of TCE, DCE, and VC, all of which are volatile compounds. This has led to the development of the hypothesis investigated herein: that gas generated during groundwater remediation could induce compartment transfer of volatile contaminants into the gas phase, which may transport the contaminants away from the source zone. A conceptual model of this process is presented in Figure 1.2.  1.6.2 Field sites Data to support this hypothesis were noted at two field sites in the U.S. The first site was an industrial site in Oregon, where a TCE-contaminated site was subjected to enhanced bioremediation under anaerobic conditions. Following primary substrate injection to the site, indoor air concentrations of TCE in the basement of a building above the remediation were  14 found to be significantly higher than those measured prior to remediation. Additionally, the detection of DCE and VC in sub-slab soil vapour suggests the compounds originated in the remediation zone in the subsurface (Landau Associates, 2008). The second site, a US EPA Superfund Site, was a former drycleaner in Bozeman, Montana with a tetrachloroethylene (PCE) source zone and dissolved plume contamination. Here, a pilot project was implemented to investigate the suitability of enhanced bioremediation for the site (Montana Department of Environmental Quality, 2011a). Soil vapour monitoring prior to and during the project revealed substantially increased concentrations of PCE daughter products in the vadose zone. In particular, soil vapour VC concentrations (which had never been detected on site prior to the pilot project) increased to above the inhalation exposure limit immediately adjacent to the pilot project (Cardno ATC, 2015).  1.6.3 Potential impacts Unintentional stripping of volatile contaminants due to gas exsolution and ebullition has the potential to impact the success of a remediation project as well as raises concerns regarding health issues. If untreated compounds are transported away from the treatment zone and into the vadose zone, VOCs may continue to travel quickly.  The size of the contaminated area may increase, and previously ‘clean’ areas become contaminated. As they are no longer in contact with the remediation zone, the contaminants will not be treated. Due to the presence of low-pressure zones underneath building basements and foundations, there is also the likelihood of a pressure gradient forming, resulting in vapour intrusion into underground structures.   15 To investigate the potential for contaminant stripping from a TCE source zone during remediation, bench-top laboratory experiments were designed. These simulated both ISCO remediation using sodium permanganate, as well as enhanced bioremediation. The experimental setup and analytical methods are described in Chapter 2, the results and discussion thereof are shown in Chapter 3, and overall conclusions are presented in Chapter 4.     16 1.7 Figures  Figure 1.1- Reaction pathway showing sequential reductive dechlorination of TCE during co-metabolism.    trichloroethylene 1,1-dichloroethylene cis-1,2-dichloroethylene trans-1,2-dichloroethylene vinyl chloride ethene [TCE] [DCE] [VC]  17  Figure 1.2- Conceptual model of VOC transport via gas exsolution and ebullition. Treatment of the contaminant pool results in gas bubble formation. Contact of the gas bubbles with the VOCs allows the contaminant to partition into the gas phase, resulting in transport away from the treatment zone, where it may cause vapour intrusion to subsurface structures. Figure made using Health Canada Contaminated Sites Division’s Conceptual Model Builder (Health Canada, 2015). 18 1.8 Tables Table 1.1- Henry’s Constants and Bunsen Coefficients Gas Henry’s Constant1 [mol/L atm] (20°C)  Bunsen Coefficient2 [ml/L atm] (STP) N2 6.54 × 10-4 12.63 O2 1.29 × 10-3 25.28 Ar 1.42 × 10-3 27.84 CO2 3.43 × 10-2 739.50 CH4 1.38 × 10-3 27.87 1 (Sander, 1999) 2 (Colt, 2002)     19 Chapter 2: Methods 2.1 Overview There were two stages of the experiments designed to investigate unintentional contaminant stripping from a TCE source zone during remediation: batch reactors and column experiments. As the premise of the experimental hypothesis relies on the production of gas under saturated conditions, remediation methods that produce significant quantities of gas were selected for investigation. The enhanced bioremediation experiment depended on biogenic gas production. The first stage of the experiment, the batch reactors, investigated possible combinations of sediments and substrates, in order to find a biologically active combination. These results were used to dictate the choice of sediment and substrate to be used in the second stage, the column experiment. The second remediation strategy, in situ chemical oxidation, generates CO2 during the chemical oxidation of TCE by permanganate. The ISCO experiment began directly in the column stage.  2.2 Experimental design 2.2.1 Batch reactors The batch reactors were constructed containing various combinations of sediments and substrates. The batch reactor experiment was designed to determine a sediment/substrate combination capable of sustaining biodegradation processes and associated gas production (i.e. vigorous microbial respiration). Using this mixture in the column experiments ensured representative conditions including a potential for gas exsolution and ebullition driven by  20 microbial respiration. The batch reactors consisted of 325 mL heavy-walled borosilicate glass vessels with o-ring sealed polytetrafluoroethylene (PTFE) caps and fitted with pressure sensors to monitor gas production within the vessel (ACE Laboratory Glass, prod. 8648), as shown in Figure 2.1. The vessels were rated to remain gas-tight under positive pressure up to 60 psig. Various sediments were collected from local sites for testing, including silty sand from a TCE-contaminated site, and anaerobic sludge that had been previously noted to have an active microbial population. Primary substrates were selected for testing based on commonly used substrates in enhanced bioremediation. Potential substrates that were considered based on their successful use in field applications included acetate (e.g. Lee et al., 2012; Rittmann and Seagren, 1994), lactate (e.g. Ellis et al., 2000; Song et al., 2002; Wymore et al., 2006), phenol (e.g. Fries et al., 1997; Hopkins et al., 1993), methanol (e.g. El Mamouni et al., 2002), glucose (e.g. Kao and Prosser, 1999), and organic biosolids (e.g. Jones and Healey, 2010). All potential substrates are easily-degradable carbon sources that can act as electron donors during microbial respiration. The sediment/substrate combinations that were selected for testing in the batch reactor experiment are shown in Table 2.1. The batch reactor sediments were mixed with clean Ottawa sand (amounts shown in Table 2.1), and the glass vessels were filled using sediment-water slurry. Anaerobic groundwater collected from a local site was used in the batch reactors; aqueous properties and common ion concentrations are shown below:   21 pH 6.55 Temperature (°C) 13.5 Dissolved Oxygen (ppm) <0.05 Cl- (mg/L) 54.1 SO42- (mg/L) 39.6 Total Fe (mg/L) 53.3  After adding the sediment-water slurry to the batch reactor vessel, the remaining space was filled with more groundwater. The sediments were left to settle for a day, then some water was removed from the top of the vessel with a syringe in order to create a headspace of known volume (see Table 2.1). As the primary goal for the batch reactors was to determine the combination of sediment and substrate that would produce the greatest volume of gas, the headspace pressure was monitored using pressure transducers. When the rate of gas production appeared to plateau, additional substrate was added to the glass vessels, assuming the microbial respiration had slowed due to consumption of the substrate.  The results from the batch reactor experiments are found in Chapter 3. 2.2.2 Column design For the second stage of the experiment, columns were constructed to simulate remediation of a TCE source zone. The column material had to be compatible with the use of chlorinated solvents, as the potential sorption of TCE onto the sides of the column could inhibit the vertical transport of TCE and obscure the effect that was trying to be observed. Due to the material incompatibility, the use of many commonly used synthetic polymers for the  22 construction of columns was determined to be ineffective for use with TCE in this experiment. Based on studies investigating the sorption potential of organic compounds onto a variety of synthetic materials typically used for piping, it has been determined that TCE will readily sorb onto polyvinyl chloride (PVC), polypropylene, and polyethylene (Lian et al., 2012; Miller, 1982). The preferred material for use with groundwater contaminated with organic compounds when compound adsorption is of concern is glass (Pettyjohn et al., 1981). As such, borosilicate glass columns (I.D. = 10 cm, wall thickness = 5 mm, height = 75 cm) were constructed by ACE Laboratory Glass for this experiment, the design of which is shown in Figure 2.2. The columns were fitted with sampling ports up the side, each port equipped with a ball valve and a syringe septum in order to withdraw samples without disturbing the sediments, and avoid leaks. The placement and spacing of the sampling ports on the columns is also shown in Figure 2.2.  The syringe septa were made of silicone equipped with PTFE liners (also selected for material compatibility) that could be replaced after being punctured several times by closing the ball valve and unscrewing the end of the sampling port. A semi-rigid (1/8” O.D., 1/16” I.D.) PTFE tube with a screened end piece was connected to the sampling ports, which provided guidance for the long flexible needles that withdrew samples, and prevented sand from entering the samples. The design of the sampling ports is shown in Figure 2.3, as well as photos of the assembly process. Figure 2.4 shows one of the flexible needles used for sampling. The glass columns had a rounded bottom, which eliminated the potential for basal leakage, and a flat ground glass top with an inlaid gutter for an o-ring. A separate glass column headpiece with a ground glass bottom was placed on the top of the column, sealed with a PTFE o-ring between the column and the headpiece, and secured with an adjustable clamp collar. The columns were  23 completely sealed, effectively creating a closed environment. The headpiece tapered at the top to an interior-threaded port into which a PTFE adaptor could be attached; the adaptor allowed for the installation of a pressure transducer into the headspace of the column. The pressure transducer (Dwyer Instruments) measured pressure using a differential voltage and was read by a data acquisition (DAQ) modem (National Instruments) every 30 minutes. In order to have the columns stand vertically, prevent scratching of the glass, and stabilize the columns against minor disturbances, the columns were placed onto cork o-rings and supported by a custom-built stand (Figure 2.5). The entire experimental apparatus was placed in the fumehood due to the use of toxic volatile chemicals.  2.2.3 Column filling The bottom 10 cm of each column contained the ‘treatment zone’. The treatment zone was overlain with gravel, and the remainder of the column was packed with clean sand (standard Ottawa silica sand, 20-30 mesh, θ = 0.35). During experimental setup, the columns were packed using a sand-water slurry in order to avoid the entrapment of air bubbles in the column. The sediments were fully saturated, with the water table extending slightly above the sand (Figure 2.6). This made it possible to see bubbles rising up to the headspace, and ensured that there would be sufficient water in the columns in case sampling continued for longer than anticipated. The columns were stagnant, i.e. no advective flow was applied to the columns. There were two columns with remediation treatments applied, one with an in situ chemical oxidation treatment (‘ISCO column’) and one with an enhanced bioremediation treatment (‘bioremediation column’), and one control column. The control column was used to distinguish  24 the vertical transport of contaminants via compartment transfer from the effects of diffusion and other influences. Both treatment columns and the control column contained a contaminant zone composed of 10 mL of pure phase TCE (0.11 moles) amended with 100 mg/L Sudan IV dye. Sudan IV is commonly used when testing for the presence or tracking the movement of organic compounds at contaminated sites (Griffin and Watson, 2002). Sudan IV is a non-polar dye and is insoluble in water. Its use turned the TCE bright pink to allow for better visualization of the contaminant location through the glass walls of the column. The pure phase TCE was injected slowly into the lowermost port (h = 6.5 cm) of the column below the gravel layer using a 6” syringe (Figure 2.7). The goal was to inject the TCE into the center of the column and allow it to flow radially outwards in order to obtain a homogeneous spread of contaminant. Since the TCE is a DNAPL, it was expected that it would sink to the bottom of the column and pool, leaving residual product between the injection port and the pool. Where the TCE came into contact with the column walls, the dyed TCE was easily visible through the transparent glass. However, the exact location of the contaminant spread was not clear for all columns. TCE injection for the control column was fairly successful at emplacing the TCE in the centre of the column, while in the treatment columns a small amount of TCE flowed back along the injection line (Figure 2.8), resulting in non-uniform contaminant spread. Based on visual inspection, less than 10% of the injected volume remained close to the injection ports on both treatment columns.   25 2.2.4 ISCO column treatment For the ISCO column, a 40 wt% sodium permanganate (NaMnO4) solution (Sigma-Aldrich) was injected into the treatment zone.  Due to its high solubility in comparison to potassium permanganate (approximately 90 g/100 mL vs. 6.4 g/100 mL at 20°C respectively), NaMnO4 was more suited for the ISCO column experiment (NIST, 2015). Since the columns were stagnant, injections with the smallest volume possible were preferred in order to avoid creating advective flow in the columns that could influence the migration of TCE by displacement. Based on the reaction of the oxidation of TCE with permanganate, there is a 1:2 molar ratio of TCE:permanganate required for the reaction. C2Cl3H + 2 MnO4-  2CO2 + 2MnO2 (s) + 3 Cl- + H+ To fully treat the 10 mL of pure phase TCE in the contamination zone, 545 mL of potassium permanganate solution would have been necessary: 10 𝑚𝐿 𝑇𝐶𝐸 × 1.46 𝑔𝑚𝐿 ×  𝑚𝑜𝑙131.4 𝑔 = 0.11 𝑚𝑜𝑙 𝑇𝐶𝐸 1 ∶  2 𝑚𝑜𝑙𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 𝑜𝑓 𝑇𝐶𝐸 ∶ 𝐾𝑀𝑛𝑂4 0.22 𝑚𝑜𝑙 𝐾𝑀𝑛𝑂4  ×  158.034 𝑔𝑚𝑜𝑙 × 𝐿 𝐻2𝑂 @ 20 ℃63.8 𝑔  = 0.545 𝐿 = 545 𝑚𝐿 This volume of potassium permanganate solution was determined to be excessive, thus sodium permanganate was selected instead. This was injected as a 40 wt% solution in excess of the required volume to encourage the reaction to go to completion. 100 mL of sodium  26 permanganate solution was injected, which represents a 1.8× excess and thus was not anticipated to be a limiting reagent for the treatment of TCE: 100 𝑚𝐿 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 ×  1.391 𝑔𝑚𝐿 × 40 𝑤𝑡% ×  𝑚𝑜𝑙141.9 𝑔 = 0.39 𝑚𝑜𝑙 𝑁𝑎𝑀𝑛𝑂4 1 ∶ 2 𝑚𝑜𝑙𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 𝑜𝑓 𝑇𝐶𝐸 ∶  𝑁𝑎𝑀𝑛𝑂4  0.11 𝑚𝑜𝑙 𝑇𝐶𝐸 ∶ 0.39 𝑚𝑜𝑙 𝑁𝑎𝑀𝑛𝑂4  = 1.8 ×  𝑒𝑥𝑐𝑒𝑠𝑠 𝑜𝑓 𝑁𝑎𝑀𝑛𝑂4 As the reaction produces solid manganese oxides as a byproduct and the permanganate solution must be in contact with dissolved TCE in order to proceed, it was anticipated that the reaction might not go to completion. In practical applications of ISCO, an excess of permanganate may be applied in order to compensate for naturally-occurring organic carbon which may be oxidized alongside the target compound and essentially ‘use up’ the oxidant. Alternatively, sequential injections have been found to be successful at satisfying the non-target oxidant demand in addition to the target compound (Droste et al., 2002).  However, this was not anticipated to be an issue in the ISCO column as no organic-rich sediment was present. The permanganate solution was dark purple in colour, and artificially dying the solution with a tracer was therefore not necessary. 2.2.5 Enhanced bioremediation column treatment For the enhanced bioremediation column, the treatment zone was packed with sand mixed with sediments from a local TCE-contaminated site containing a seed microbial population capable of performing reductive dechlorination of TCE, and injected with 100 mL of a 20 g/L sodium acetate solution to act as the primary substrate. This primary substrate was  27 selected based on the results from the batch reactor experiment, which determined it was a combination capable of sustaining vigorous microbial respiration. In addition, it was speculated that since the microbial population had been exposed to TCE contamination (in the original location) that the microbes would be acclimatized to chlorinated solvents and resist the toxicity that can occur when microbes are subjected to high concentrations of TCE (Alvarez-Cohen and McCarty, 1991; Mu and Scow, 1994). During the packing of the bioremediation column, the contamination zone was filled with Ottawa sand mixed with the contaminated site sediment, then filled and injected with TCE as described in the ISCO column section. At time = 0 days the acetate solution was injected into the lowermost port as the primary carbon substrate for the microbes.  2.2.6 Control column In the control column, which was filled with clean sand, the same contamination zone was created, but no treatment was applied. TCE is a DNAPL and thus was expected to sink to the bottom of the column after being injected, and as no flow was applied to the column the TCE in the dissolved phase was not expected to be transported vertically via advection or dispersion. The effects of molecular diffusion over a period of several months are expected to be minimal. Using the reported value for TCE free-water diffusion D = 9.1 × 10-10 m2/s (GSI Environmental, 2014), the measured porosity of the sand (θ = 0.35), calculating the tortuosity τ using Archie’s Law, and estimating the cementation exponent m = 1.4 from standard values for unconsolidated sands (Jackson et al., 2008) to calculate the effective diffusion D*, within 6  28 months the effects of diffusion would result in the migration of TCE over less than 5 centimeters (using a breakthrough concentration of C/Co = 0.5): 𝐷∗ =  𝜃𝜏𝐷 ; 𝜏 =  𝜃1−𝑚 𝐷∗ =  0.350.35(1−1.4)(9.1 ×  10−10𝑚2𝑠) = 2.1 ×  10−10  𝑚2𝑠 𝐶𝐶𝑜⁄ = 𝑒𝑟𝑓𝑐(𝛽) = 0.5;  𝛽 = 0.47 𝛽 =𝑥2√𝐷∗𝑡 ; 0.47 =𝑥2√(2.1 ×  10−10 𝑚2 𝑠⁄ )(1.58 × 107𝑠) ; 𝑥 = 0.05 𝑚 Based on this rough calculation, it was predicted that the vertical migration of TCE via molecular diffusion would be unlikely to reach even the height of the second sampling port (13 cm) at substantial concentrations. No remediation treatment was applied to the contamination zone in the control column. However, since the treatment columns received injections and periodic withdrawals during sampling, it was thought that this forced movement of water could induce small amounts of flow, causing advective and dispersive transport of TCE.  In order to simulate this for the control column, water samples were withdrawn from the ports in a schedule that mimicked the sampling of the treatment columns. Additionally, the control column received an injection of 100 mL of a dense saturated saline solution (ρ = 1.18 g/cm3) to simulate any potential effects of the density-driven sinking of the permanganate solution.    29 2.3 Column monitoring and sampling The pressure in both of the remediation columns and the control column was monitored using pressure transducers hooked up to a data acquisition device and routed to a computer. The pressure transducers were capable of monitoring the headspace pressure continuously, although in the interest of keeping the size of the dataset more manageable the headspace pressure was only measured every 30 minutes. In order to calculate the volume of gas produced from the measured pressure, the following calculation was used: 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑔𝑎𝑠 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 =  𝑔𝑎𝑠 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 [𝑎𝑡𝑚]  ×  ℎ𝑒𝑎𝑑𝑠𝑝𝑎𝑐𝑒 𝑣𝑜𝑙𝑢𝑚𝑒 [𝐿]𝑅 [𝐿 ∙ 𝑎𝑡𝑚 ∙ 𝑚𝑜𝑙−1 ∙ 𝐾−1]  ×  𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 [𝐾] 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑔𝑎𝑠 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 = 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑔𝑎𝑠 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 × 𝑉𝑚 where R is the universal gas constant (0.08206 L∙atm∙mol-1∙K-1). For the duration of the experiment, the temperature in the fumehood was kept constant at 20°C (293.15 K). Vm is the molar volume, which describes the litres of gas in one mole. At 20°C, this value is 24.056 L/mol. For these calculations, the headspace volume was adjusted after each sampling round due to the water loss from sampling.   In the case of the ISCO column, the pressure buildup in the headspace occasionally increased close to the upper limit of the range of the pressure transducer. In this case, excess gas was vented by opening the headspace sampling valve and allowing the gas in the headspace to escape until headspace pressure was equal to atmospheric pressure. For headspace gas concentrations and calculation of cumulative gas produced, the vented gas was assumed to have a homogeneous composition equal to the concentrations observed from the previous  30 sampling event. The gas venting required a correction factor to be applied to the calculated volume of cumulative gas produced, as well as the gas sampled from the headspace for analysis. In addition, small volumes of gas loss were noted during some of the sampling rounds by comparing the expected headspace pressure change before and after sampling with the actual observed pressure change. The amount of gas loss was determined using the following calculation, where PI is the initial pressure (prior to sampling), PF is the final pressure (after sampling), VHS is the volume of gas in the headspace, VS is the volume of sampled gas, and VL is the volume of gas loss: 𝑃𝐼𝑉𝐻𝑆 = 𝑃𝐹 (𝑉𝐻𝑆 + 𝑉𝑆 + 𝑉𝐿) 𝑉𝐿 =  𝑃𝐼𝑉𝐻𝑆𝑃𝐹− 𝐻𝐻𝑆 − 𝑉𝑆 The amount of gas lost during sampling events was calculated in order to ensure it was compensated for during the calculation of cumulative gas production. During water sampling, the ball valve on the sample port was opened and samples were withdrawn using 6” long flexible needles attached to a 1 mL glass syringe. The water samples were placed into 1 mL Supelco glass vials with polypropylene screw caps equipped with silicone septa lined with PTFE. No headspace was left in the vials. In most cases, sample analysis was performed on the same day as sample withdrawal. If this was not possible, samples were stored in the refrigerator and analysis was performed as soon as possible.  For gas sampling of the headspace, the 6” long flexible needle was attached to a 5 mL gas-tight glass syringe. 2.5 mL of gas was injected into two 2 mL evacuated glass vials through  31 the silicone septa at the top of the vial. This slight overpressure was used as it was found to minimize gas leaks from the vial. In most cases, sample analysis was performed on the same day as sample withdrawal. Following analysis, silicone sealant was applied to the top of each vial for storage, in case additional analysis was desired. This resulted in the vials losing compatibility with the gas chromatograph autosampler, however manual injection could be performed. 2.4 Sample analysis Sample analysis for fixed gases was performed on a Bruker 450 gas chromatograph (GC) equipped with a heated injection port to allow for the injection of liquid samples. Sample analysis for VOCs was performed on an Agilent 6890 N GC coupled with an Agilent 5975B mass spectrometer detector (GC-MS). Analysis methods are described in more detail in Appendix A.    32 2.5 Figures  Figure 2.1- Glass pressure vessel for batch reactor, with pressure transducer attached to lid.    33   Figure 2.2- Column design schematic, reproduced with consent from Ace Glass Inc.  34  Figure 2.3- Sampling port design (top) and assembly (photos). Steps not shown include compression of the tube sleeve onto the guidance tube, attachment of Teflon tape (yellow) on threads, and tightening of threads. Sample port (fused to column), glass, #7 Ace-Thred Guidance tube, PTFE, 1/8” OD, 1/16” ID Ace-Thred / NPT adapter, PTFE o-ring, viton Compression tube sleeve Tube support Ball valve Septa, PTFE-lined Compression fitting Approximate attachment point  35  Figure 2.4- Flexible syringes used for sampling through ports.   36  Figure 2.5- Column stand with empty columns. Sampling ports are not attached, and pressure transducers are absent.    37  Figure 2.6- Column design, indicating column fill and placement of sampling ports      pressure sensor headspace sand layer gravel layer treatment zone sampling ports  75 cm h = 6.5 cm h = 13 cm h = 20 cm h = 26.5 cm h = 33 cm h = 40 cm headspace sampling port  38   Figure 2.7- Injection of TCE into target zone of ISCO column.    Figure 2.8- Contamination spread following TCE injection on control (left), ISCO (middle), and bioremediation (right) columns, prior to treatment application.  39 2.6 Tables Table 2.1- Batch reactor contents Batch reactor Sediment Substrate Sediment mass [g] Ottawa sand [g] Groundwater [mL] Headspace volume [mL] 1 Contaminated site sediment Glucose 150.1 249.8 154 18 2 Contaminated site sediment Acetate 150.4 250.1 118 29 3 Contaminated site sediment Biosolids 152.9 250 120 26 4 Local anaerobic sludge Glucose 102.3 251.1 112 16 5 Local anaerobic sludge Acetate 99.9 249.9 115 13 6 Local anaerobic sludge Biosolids 101 252 122 15    40 Chapter 3: Results and discussion 3.1 Results 3.1.1 Chapter overview Results from the control column, the ISCO column, and the enhanced bioremediation preliminary batch reactor and column experiments are presented in this chapter. 3.1.2 Control column The results from the control column are depicted in Figure 3.1, which shows the TCE concentration in the second (h = 13 cm) sampling port. In the control column, the concentration of TCE in the contamination zone was found to remain close to TCE solubility (concentrations ranged from 990-1180 mg/L) throughout the course of the experiment. No gas production was observed in the control column based on the pressure transducer measurements. However, TCE was detected in the sampling port at h = 13 cm after 80 days. No TCE was detected in any of the higher sampling ports, nor was it seen in the headspace. Using a Fickian diffusion model, an estimate for the effective diffusion coefficient was calculated to be around 2-3 × 10-11 m2/s. The effective diffusion coefficient was calculated based on a travel distance from the lowermost (6.5 cm) port to the 13 cm port rather than from the bottom of the column to the 13 cm port, since no concentration measurements could be obtained from the bottom. The measured TCE concentration in comparison to the modeled TCE concentration (using the calculated effective diffusion coefficient and assuming a source concentration at TCE solubility) is shown in Figure 3.2. The control column was left for 175 days, the same amount of time as the enhanced bioremediation column (3 months longer than the ISCO column).  41 3.1.3 ISCO experiment 3.1.3.1  Observations Immediately following the injection of the permanganate to the treatment zone, the dense permanganate solution sunk to the bottom of the column. The permanganate was visible as dark purple to blackish in colour, and began ‘feathering’ upwards within minutes of injection (Figure 3.3). Direct evidence of gas generation was observed through the transparent column walls in the form of upward-migrating bubbles and through the development of transient desaturated patches of sand (indicated in Figure 3.3 with red arrows), significant bubbling in the small void space near the sampling port, as well as empirically using the pressure transducer monitoring the headspace pressure. TCE treatment and movement was observed through the glass, particularly within the gravel layer where pore size was larger (see Figure 3.4, which includes screenshots from Video 3.1), with changes occurring on the timescale of seconds during the first several hours following the injection. Gas ebullition and the movement of TCE in the gravel layer associated with gas bubble migration is shown in the first half of Video 3.1, which can be viewed online at http://hdl.handle.net/2429/57042. The ISCO portion of Video 3.1 was filmed approximately 30 minutes after the permanganate injection. During the days immediately following the permanganate injection, small changes were noticeable along the column walls. These included the opening and subsequent collapse of void spaces in the sand (Figure 3.5), and the appearance and disappearance of pink-dyed TCE (Figure 3.6). Within a week of the injection, physical changes became rare to observe.  Additionally, the permanganate solution in the bottom of the column acquired a red-brown tinge, particularly at  42 the interface between the permanganate and the ‘clean’ sand, which persisted throughout the remainder of the experiment (Figure 3.7). This red-brown material (solid manganese oxides) was inspected in more detail during dismantling of the column.  3.1.3.2  Gas production Gas production from the ISCO column is depicted in Figure 3.8, showing the pressure in the headspace of the column, measured by the pressure transducer, as well as the calculated volume of gas produced, as discussed in section 2.3. Also shown on the figure are the days on which sampling events occurred, as well as headspace venting events.  The gas production rate at the beginning of the experiment (first ~6 days) was the highest, occurring at a rate of approximately 110 mL/day. For the following week, the gas production rate decreased significantly to approximately 20 mL/day. This coincided with the point at which physical changes in the column (gas bubbles, de-saturation of sand patches) became rare to observe. The gas production continued to decrease throughout the course of the experiment to a rate of ~1.5 mL/day within 2 months of the experiment commencing, at which point the gas production became insignificant. The gas production rate throughout the course of the experiment is shown in Figure 3.9. The gas production rate is calculated as the average rate of production between each sampling event. The total amount of gas released to the headspace of the ISCO column throughout the duration of the experiment (94 days) based on the pressure transducer calculations is close to a litre of gas (979 mL) (normalized to STP).  The actual total amount of gas produced was slightly higher than what was calculated using the pressure transducer measurements; in addition to the dissolved gas there was also  43 tendency for small volumes of gas to escape during sampling through the ports. An estimate of the gas lost during sampling was calculated based on the pressure measurements in the headspace prior to and following the sampling event, and compared to the expected pressure loss due to gas removal, as shown in section 2.3. The gas loss estimates from sampling events are shown in Table 3.1. The adjusted cumulative gas production based on the gas loss calculations is shown on Figure 3.8 with orange indicators. On average, sampling events resulted in the loss of 13 mL of gas, with a tendency for higher volumes to be lost during the earlier sampling events when headspace pressure was consistently increasing, and less during the later sampling events. The estimated gas lost throughout the course of the experiment was 173 mL, which increases the calculated volume of total gas produced in the ISCO column to 1152 mL. 3.1.3.3  Gas profiles Dissolved gas analyses from select sampling events are shown in Figure 3.10. Argon concentrations have been removed for the sake of clarity, as Ar is a nonreactive gas, and Ar concentrations never exceeded 0.01 atm and thus are not significant at the scale of Figure 3.10.  Initial conditions show gas concentrations in equilibrium with atmospheric concentrations, and generally consistent throughout the entire length of the column. CO2 generated during the permanganate oxidation increased the pCO2 in the column immediately; the first two sampling events indicate rapidly increasing CO2 concentrations throughout the column. At two days following the permanganate oxidation, the pCO2 had increased to ~0.5 atm at the bottom of the column in the treatment zone and up to ~0.3 atm near the top of the column. By day 6,  44 these had increased to ~0.7 atm and ~0.5 atm respectively. This is the period in which the bulk of the CO2 was released into the headspace (~675 mL cumulatively) due to the fast permanganate oxidation reaction rate. Dissolved gas profiles stabilized around those shown for days 16 and 91, with very little variation occurring between. The dissolved gas concentrations throughout the course of the ISCO experiment from ports h = 6.5 cm (in the treatment zone) and h = 33 cm (near the top of the sand column) are shown in Figure 3.11. The two ports show similar trends, with N2 being stripped quickly (earlier at h = 6.5 cm than h = 33 cm), and CO2 building up then leveling off (pCO2 ~ 0.7 atm at h = 6.5 cm, pCO2 ~ 0.6 atm at h = 33 cm) after 6 days. The high solubility of CO2 resulted in significant amounts of CO2 produced during the permanganate reaction being dissolved in the water column, in addition to the CO2 released to the headspace. Based on the partial pressures measured and the volume of water in the column, the amount of CO2 dissolved at the completion of the experiment can be estimated (based on an average pCO2 = 0.7 atm): 𝐶 [𝑚𝑜𝑙𝐿] = 𝑝𝐶𝑂2  ×  𝐾𝐻 [𝑚𝑜𝑙𝐿 ∙ 𝑎𝑡𝑚] = 0.7𝑎𝑡𝑚 ×  3.43 × 10−2  𝑚𝑜𝑙𝐿 ∙ 𝑎𝑡𝑚= 2.4 × 10−2  𝑚𝑜𝑙𝐿    2.4 × 10−2  𝑚𝑜𝑙𝐿 ×  1.58 𝐿 = 3.79 × 10−2 𝑚𝑜𝑙𝑒𝑠 𝐶𝑂2 The calculated amount of dissolved CO2 is significant, representing approximately 45% of the total CO2 produced during TCE treatment (including CO2 released to the headspace and lost during sampling- values are shown in calculation in Section 3.1.3.4).  45 The estimation of dissolved CO2 represents a conservative calculation of the amount of CO2 produced during the TCE treatment, since some of the CO2 will be converted to bicarbonate: CO2 + H2O  HCO3- + H+ The distribution of carbonate species is controlled primarily by pH, with acidic conditions favouring carbonic acid/dissolved CO2 (H2CO3 i.e. CO2(aq)), circum-neutral pH conditions favouring bicarbonate (HCO3-), and high pH conditions favouring carbonate (CO32-). The generation of acidity during the oxidation of TCE (as shown in Section 1.2.2) and the lack of pH-buffering capacity provided by the column sediments indicate there should not be significant bicarbonate (and negligible carbonate), so the calculated amount of dissolved CO2 should not represent a substantial underestimate. The headspace gas composition indicated that CO2 increased significantly from the initial atmospheric conditions, as shown in Figure 3.12. The CO2 increase commenced immediately at the beginning of the experiment, due to the release of gas from the permanganate treatment. The CO2 in the headspace increased rapidly during the period of high gas production and stabilized around 35% by day 16; at this point approximately 0.875 L of CO2 had been released (including vented gas as well as gas lost during prior sampling events). Further increases of CO2 in the headspace were observed throughout the remainder of the experiment but were comparatively small.    46 3.1.3.4  TCE treatment A mass balance was completed to estimate how much TCE was treated by the permanganate oxidation, incorporating the amount of CO2 released to the headspace (HS), dissolved in the water column (D), and lost during sampling (L). Based on this calculation, an estimated 39% of the TCE was oxidized by the permanganate.  𝑚𝑜𝑙𝑒𝑠 𝐶𝑂2  = (0.979 𝐿 × 1 𝑚𝑜𝑙24.056 𝐿)𝐻𝑆+ (3.79 × 10−2 𝑚𝑜𝑙)𝐷 +  (0.173 𝐿 × 1 𝑚𝑜𝑙24.056 𝐿)𝐿 𝑚𝑜𝑙𝑒𝑠 𝐶𝑂2 =   (4.07 × 10−2 + 3.79 × 10−2 + 7.19 × 10−3) = 8.58 × 10−2𝑚𝑜𝑙 1: 2  𝑇𝐶𝐸 ∶  𝐶𝑂2 𝑚𝑜𝑙𝑎𝑟 𝑟𝑎𝑡𝑖𝑜 𝑇𝐶𝐸 𝑡𝑟𝑒𝑎𝑡𝑒𝑑 = (4.23 × 10−2 𝑚𝑜𝑙)  ×  (131.4𝑔𝑚𝑜𝑙) × (𝑚𝐿1.46 𝑔) = 3.9 𝑚𝐿 3.9 𝑚𝐿 𝑇𝐶𝐸 𝑡𝑟𝑒𝑎𝑡𝑒𝑑10 𝑚𝐿 𝑇𝐶𝐸→ 39% 𝑐𝑜𝑚𝑝𝑙𝑒𝑡𝑒    3.1.3.5  TCE in the column TCE concentrations from select sampling events from aqueous samples taken along the length of the column throughout the course of the experiment are shown in Figure 3.13. Prior to the injection of the permanganate solution, TCE concentrations were zero everywhere except the treatment zone. Following the permanganate injection, TCE concentrations were detectable (> 5 mg/L) in the 13 cm and 20 cm sampling ports within 2 days. TCE was detected in the 26.5 cm port within 6 days, and the 33 cm port within 10 days. In subsequent sampling  47 events (10 sampling events from t = 16 days to t = 91 days inclusive), TCE was detected throughout the entire length of the column. During this later time period, TCE concentrations increased minimally in comparison to earlier in the experiment. This apparent stabilization of TCE concentrations corresponds with the observed drop in the rate of gas production (Figure 3.9).  In the treatment zone the concentration of TCE remained high throughout the course of the experiment, ranging from 1066-1165 mg/L, close to the solubility limit of TCE (1280 mg/L). No trends were observed (see Figure 3.14), which was attributed to (1) incomplete oxidation of the TCE resulting in sufficient TCE remaining in the treatment zone to maintain a dissolved concentration near solubility, and (2) spatial heterogeneities in the contamination spread resulting in untreated zones of TCE.  3.1.3.6  TCE in the headspace Headspace concentrations of TCE are shown in Figure 3.15. TCE vapors were detected in the headspace in the first sampling event following the permanganate injection, and continued to increase in concentration for the first six weeks of the experiment. After this point, TCE vapour concentrations remained relatively steady (around 300 ppm) throughout the remainder of the experiment. Figure 3.16 compares the TCE in the headspace with that of the highest aqueous sampling port, after converting the headspace values to equivalent aqueous concentrations for water in equilibrium with the headspace (example shown below for TCE on day 10):  48 𝐶𝑎𝑞𝑢𝑒𝑜𝑢𝑠 𝑒𝑞𝑢𝑖𝑣. [𝑚𝑜𝑙𝑚3] =  𝐶𝑎𝑖𝑟 [𝑚𝑜𝑙𝑚3]𝐾𝐻′  where KH’ is the dimensionless Henry’s constant (for TCE, KH’ = 0.41). 𝐶𝑎𝑖𝑟 [𝑚𝑜𝑙𝑚3] = (𝐶𝑎𝑖𝑟[𝑝𝑝𝑚] ×  𝑚𝑜𝑙𝑒𝑠 𝑎𝑖𝑟 𝑖𝑛 ℎ𝑒𝑎𝑑𝑠𝑝𝑎𝑐𝑒106)𝑉ℎ𝑒𝑎𝑑𝑠𝑝𝑎𝑐𝑒[𝐿] 1000 𝐿𝑚3⁄⁄  where the moles of air in the headspace are calculated using the universal gas law, based on the volume and pressure in the headspace at the time of sampling. Using the values from day 10 (TCEair = 192.7 ppm, Vheadspace = 1.432 L, Pheadspace= 1.230 atm): 𝐶𝑎𝑞𝑢𝑒𝑜𝑢𝑠 𝑒𝑞𝑢𝑖𝑣. [𝑚𝑜𝑙𝑚3]=   ( 192.7 ×  ((1.230 𝑎𝑡𝑚 ×  1.432 𝐿) (0.08206 𝐿 ∙ 𝑎𝑡𝑚𝑚𝑜𝑙 ∙ 𝐾  ×  293.15 𝐾)⁄106)(1.432 𝐿) 1000 𝐿 𝑚3⁄⁄0.41 = 0.0240 𝑚𝑜𝑙 𝑚3⁄  𝐶𝑎𝑞𝑢𝑒𝑜𝑢𝑠 𝑒𝑞𝑢𝑖𝑣. =   0.0240 𝑚𝑜𝑙𝑚3 ×  131.4 𝑔𝑚𝑜𝑙 × 1000 𝑚𝑔𝑔 ×𝑚31000𝐿= 3.16 𝑚𝑔𝐿⁄   TCE concentrations in the headspace were detected slightly before TCE was detected in the highest aqueous sampling port (2 days vs. 6 days). In addition, significant dilution effects  49 were noted, with the equivalent aqueous headspace concentration of TCE consistently lower than the observed aqueous concentration at h = 40 cm. The experiment was terminated after 94 days, after determining the system was no longer undergoing significant remediation or transport of any contaminants.   3.1.4 Enhanced bioremediation experiment 3.1.4.1  Batch reactors The batch reactor gas production results are shown in Figure 3.17 for both the contaminated site sediments ‘sed 1’ and the local anaerobic sludge ‘sed 2’, combined with the three tested substrates (glucose, acetate, and biosolids). The substrates were added to the batch reactors in a variable schedule when gas production appeared to plateau; the substrate addition schedule is indicated on the figures with colour-coded arrows, and described with dates and concentrations in Table 3.2. For the glucose and acetate reactors, the concentration of the second (and third, if applicable) addition of substrate solution increased in comparison to the initial addition by an order of magnitude, in order to observe the effect of increased substrate concentration.  The reactors receiving glucose or acetate substrates had differing response times for gas production, but similar overall trends. For the contaminated site sediments, the acetate solution elicited a faster response than the glucose; the opposite was observed for the local anaerobic sludge. For both glucose and acetate, the higher concentration resulted in higher volume of gas production, but did not significantly increase the rate of gas production. The  50 approximate gas production resulting from each substrate addition is indicated in Table 3.3. Also shown is the maximum theoretical gas production, assuming all added carbon was biologically available. This provides a rough estimate for the efficiency of the sediment and substrate combination. The combination of the contaminated site sediment with the acetate solution produced the highest volume of gas, and also had the highest overall efficiency (80%) with respect to consumption of available carbon. As such, this combination was selected for use in the enhanced bioremediation column. Acetate fermentation to CO2 and CH4 is performed by acetate-oxidizing bacterial species via the carbon monoxide dehydrogenase pathway (Schink, 1997). The step-wise reactions as well as the overall reaction are shown below: CH3COO- + H+ + 2H2O  4H2 + 2CO2 ; 4H2 + CO2  CH4 + 2H2O CH3COO- + H+  CH4 + CO2 3.1.4.2  Column observations Unlike the ISCO column, physical changes were not observed in the bioremediation column near the beginning of the experiment. Some of the dyed TCE was visible in the pore spaces of the gravel layer and near the injection port, and remained stationary throughout the course of the experiment. Approximately 6 weeks after the substrate injection bubbles would occasionally but rarely be observed rising from the top of the sand to the headspace. An example of one such event is shown in Figure 3.18, which includes screen captures from the  51 second half (0.31 s onwards) of Video 3.1 (http://hdl.handle.net/2429/57042). This continued for a period of approximately 2 months.  3.1.4.3  Gas production The gas production from the enhanced bioremedation column is shown in Figure 3.19. This graph shows the pressure in the headspace of the column, measured by the pressure transducer, as well as the calculated volume of gas released to the headspace, as discussed in Chapter 2. Also shown on the figure are the days on which sampling events occurred. No venting occurred for the bioremediation column, as the pressure in the headspace did not approach the transducer’s limit throughout the experiment.  The general sequence of gas production in the bioremediation column can be categorized into 3 main stages. The first stage (‘low gas production stage’) spans from the experiment commencement until ~day 44. In this stage the gas production rate was approximately 0.4 mL/day. The second stage (‘high gas production stage’) is characterized by a steep increase in gas production, and occurred until ~day 105. During this stage, bubbles were occasionally observed in the water layer between the top of the sediments and the headspace, such as the example shown in Figure 3.18. The average rate of gas production in this stage was approximately 2.6 mL/day. In the last stage (‘plateau stage’), the gas production rate decreased gradually to approximately 0.5 mL/day until day 142, at which point it levelled off until the end of the experiment, 175 days. The gas production rate throughout the course of the experiment is shown in Figure 3.20. The gas production rate is calculated as the average rate of production between each sampling event. The total amount of gas produced in the bioremediation column  52 throughout the duration of the experiment (175 days) based on the pressure transducer calculations is shown to be around 195 mL of gas.  As in the case of the ISCO column, the gas lost during sampling events was calculated. However, in most cases the gas loss was below or similar to the accuracy limits of the pressure transducer. The pressure transducers had an accuracy limit of 0.5% of the 0-5 VDC full-scale range, which equates to roughly 2 mL based on the average headspace volume. Table 3.4 shows the sampling events in which gas loss could be estimated. The adjusted cumulative gas production based on the gas loss calculations is shown on Figure 3.19 with orange indicators. The volume of gas lost during sampling is estimated to be ~39 mL, which increases the total volume of gas produced in the bioremediation column to 234 mL. 3.1.4.4  Gas profiles Dissolved gas profiles from along the length of the column are shown in Figure 3.21. Figures from some sampling events are omitted, if the profiles are similar to the immediately prior and subsequent sampling events. Gases shown include N2, O2, CO2, and CH4; Ar is not displayed for the sake of clarity. Headspace gas composition results are not shown due to significant dilution effects obscuring relevant data, and therefore are shown on a separate figure (Figure 3.23).  Based on the gas profiles, dissolved oxygen in the contaminant zone was consumed within 16 days of the acetate injection. Although anaerobic groundwater was collected for use in the experiment, a long storage period combined with the column packing led to initial conditions of water in equilibrium with atmospheric gas concentrations, resulting in an initial  53 oxygen concentration of 8.5 mg/L. CO2 and CH4 production occurred following the contaminant zone’s shift to anaerobic conditions, resulting in the stripping of the nonreactive gases. Concentrations of CO2 and CH4 increased over time in the contamination zone, peaking near 0.25 and 0.65 atm respectively. Maximum concentrations were achieved near day 65 for CH4, and near day 93 for CO2, with both maintaining relatively constant concentrations in the contamination zone thereafter. This process induced N2 stripping and depressed N2 concentrations to ~0.1 atm. The dissolved gas concentrations throughout the course of the bioremediation experiment from ports h = 6.5 cm (in the treatment zone) and h = 33 cm (near the top of the sand column) are depicted in Figure 3.22. The two ports show similar trends, with the higher sampling port experiencing a significant lag and somewhat dampened response in comparison with the treatment zone port. The pO2 in the lower port dropped to 0 atm by day 16; this occurred in the higher port by day 72. The pN2 decreased and stabilized at ~ 0.15 atm in the lower port by day 65; the pN2 in the higher port continually decreased and appears to have approached a stable value around 0.3 atm. Both CO2 and CH4 increased from days ~16-79 in the lower port, and stabilized around 0.3 atm and 0.5 atm respectively. The CO2 and CH4 increase in the upper port did not commence until day 72, and while the CH4 concentration reached a similar value to the lower port, the pCO2 stabilized around 0.15 atm.    Increased CO2 and CH4 concentrations measured at successively higher locations in the column over time, as well as decreased concentrations of N2, indicate the formation and vertical transport of biogenic gas. CH4 concentrations were consistently higher than CO2  54 concentrations, due to the significantly lower solubility of CH4. Increased concentrations of both gases in the headspace are shown in Figure 3.22. The bottom portion of the figure has the N2 and O2 removed to observe the changes in the low concentration gases. The increase in CO2 and CH4 in the headspace begins near day 72, indicating a significant lag time following the start of gas buildup in the headspace (~day 51). The earlier gas buildup may be attributed to the stripping of nonreactive gas (N2), indicated by the decreased dissolved N2 and a slight increase in the headspace, although the dilution in the headspace dampens this observation.  3.1.4.5  TCE treatment The co-metabolism of TCE is indicated by the buildup of daughter products in the treatment zone, as shown in Figure 3.24. Note that the TCE concentration is shown on the secondary axis due to the differing orders of magnitude in concentration. TCE breakdown products did not appear until midway through the high gas production stage. The presence of both cis-DCE and VC indicate incomplete breakdown of TCE. Some trans-DCE was detected during two sampling events, but disappeared thereafter, either converted into VC or ethene, or else transported away from the contamination zone. The VC concentrations built up in the contamination zone; it is difficult for the VC to be converted to ethene in anaerobic conditions (Norris et al., 1993).  Unlike for the ISCO column, the amount of TCE that was treated by the enhanced bioremediation cannot be estimated based solely on the total gas production. The gas production can be used as an indicator of how much acetate solution was consumed; however, the amount of acetate consumed does not necessarily reflect the amount of TCE co- 55 metabolized. The carbon mass balance is therefore more complex for the bioremediation column. Two main sources of carbon are used to calculate the amount of TCE treated. First, the amount of vinyl chloride in the column at the termination of the experiment (175 days) is used, based on the observation that some of the reductive dechlorination of TCE was incomplete. The second source of carbon in the mass balance comes from CO2 dissolved in the water column and in the headspace. To account for this carbon source, CO2 generated by acetate fermentation must be differentiated from CO2 generated by the treatment of TCE. This calculation can be completed based on the molar ratios of CO2 and CH4 produced in the acetate fermentation pathway (described in Section 3.1.4.1). That is, any CO2 in the column in excess of the moles of CH4 can be attributed to the treatment of TCE.  The first part of the mass balance, the calculation for the amount of VC in the column at the end of the experiment, is shown in Figure 3.25. This calculation is performed by dividing the column into six sections, and assuming the concentration on day 175 from each sampling port (located in the centre of each section) is representative of the entire section. The sections extend from halfway between a sampling port and the port directly above and below it. An example calculation (using section 2) is shown below: ℎ𝑒𝑖𝑔ℎ𝑡𝑝𝑜𝑟𝑡 1 = 6.5 𝑐𝑚 ;  ℎ𝑒𝑖𝑔ℎ𝑡𝑝𝑜𝑟𝑡 2 = 13 𝑐𝑚 ;  ℎ𝑒𝑖𝑔ℎ𝑡𝑝𝑜𝑟𝑡 3 = 20 𝑐𝑚  ℎ𝑒𝑖𝑔ℎ𝑡𝑠𝑒𝑐.2 =  (20 𝑐𝑚 + 13 𝑐𝑚)2−  (13 𝑐𝑚 + 6.5 𝑐𝑚)2= 6.75 𝑐𝑚  𝑉𝑠𝑒𝑐.2[𝑐𝑚3] =  𝜋𝑟2ℎ =  𝜋 ×  (5 𝑐𝑚)2  ×  6.75 𝑐𝑚 = 530 𝑐𝑚3 𝑉𝑤𝑎𝑡𝑒𝑟[𝑚𝐿]  =  𝑉𝑠𝑒𝑐𝑡𝑖𝑜𝑛[𝑐𝑚3]  ×  𝜃 = 530 𝑐𝑚3  ×  0.35 = 186 𝑚𝐿  56 𝑚 [𝑚𝑔] = 𝐶 [𝑚𝑔𝐿] ×  𝑉 [𝐿] =  15.7𝑚𝑔𝐿 ×  0.186 𝐿 = 2.9 𝑚𝑔 𝑚𝑜𝑙𝑒𝑠 𝑉𝐶𝑠𝑒𝑐𝑡𝑖𝑜𝑛 2 =  𝑚 [𝑔]𝑀𝑊𝑉𝐶  [𝑔𝑚𝑜𝑙]=  2.9 𝑚𝑔 ×1 𝑔1000 𝑚𝑔62.498𝑔𝑚𝑜𝑙= 4.65 ×  10−5 𝑚𝑜𝑙𝑒𝑠 The total dissolved VC on day 175, based on the amount of VC in each of the six sections, is calculated to be 1.92 × 10-4 moles, which is then combined with the moles of VC in the headspace (9.91 × 10-5 moles), for a total amount of 2.91 × 10-4 moles. The second part of the mass balance requires calculating the total moles of CO2 and CH4 in the column in order to differentiate between CO2 associated with acetate fermentation and CO2 associated with TCE treatment. The dissolved CO2 and CH4 are calculated in the same way as the example shown in Section 3.1.3.3, using average pCO2 and pCH4 values from day 175. The CO2 and CH4 found in the headspace are also included. These calculations are shown in Table 3.5. The total amount of CO2 that can be attributed to TCE treatment is 0.008 moles. Since the molar ratio of carbon in TCE compared to CO2 is 1 : 2, a value of 0.004 moles is used for the calculation of treated TCE.  % 𝑜𝑓 𝑡𝑟𝑒𝑎𝑡𝑒𝑑 𝑇𝐶𝐸 =𝑚𝑜𝑙𝑒𝑠 𝑡𝑟𝑒𝑎𝑡𝑒𝑑𝑚𝑜𝑙𝑒𝑠 𝑖𝑛𝑗𝑒𝑐𝑡𝑒𝑑=  2.91 × 10−4 𝑚𝑜𝑙𝑒𝑠 + 0.004 𝑚𝑜𝑙𝑒𝑠0.11 𝑚𝑜𝑙𝑒𝑠 ×  100 = 4% Based on the carbon balance, only 4% of the injected TCE (10 mL/0.11 mol) was treated.  The estimate of the amount of TCE treated in the bioremediation column is approximate. The calculation is partially based on the products from the microbial fermentation of acetate, which has uncertainties associated with the degradation pathway. In addition, while  57 the overall acetate fermentation reaction suggests CO2 and CH4 will form in equal molar quantities, the fermentation proceeds in a step-wise fashion, suggesting the overall pathway may not go to completion.  Finally, in the case of the ISCO column calculation (Section 3.1.3.3), the CO2 estimate will also be affected by carbon speciation, adding additional uncertainty. However, the overall conclusion remains valid- that is, a very small amount of the TCE was treated in the bioremediation column. 3.1.4.6  VOCs in the column VOCs were transported from the treatment zone; profiles throughout the experiment can be seen in Figures 3.26 and 3.27. In both figures no sampling events are displayed prior to day 44, as no VOCs were measured outside of the treatment zone until day 44. Note that the scale on Figure 3.26 is cut off at 25 ppm, as TCE concentrations in the contamination zone were very high (seen in Figure 3.24). Figure 3.27 displays the full scale (semi-log), in order to include the TCE in the treatment zone. Headspace concentrations are not shown on the profiles, and are shown in Figure 3.29. TCE was found in increasingly higher locations throughout the experiment and in (generally) increasing concentrations. TCE was measured at the highest sampling port by day 86, and remained present at this location throughout the remainder of the experiment. The only daughter product to be transported to the top of the column was VC, which was measured in the highest sampling port by day 121. cis-DCE was measured at a height of 20 cm at day 105, but was not detected any higher in the column, and was not detected in any subsequent sampling events.  58 The VOC concentrations measured from ports h = 13 cm and h = 33 cm throughout the course of the experiment are presented in Figure 3.28. The top panel (h = 13 cm) of Figure 3.28 shows TCE concentrations increased from day 44 onwards, and cis-DCE and VC both appeared after ~ 100 days. While the VC was present throughout the remainder of the experiment, the cis-DCE was no longer detected after day 142, indicating there may have been some degradation occurring outside of the treatment zone. As shown in the bottom panel of Figure 3.28, TCE concentrations were present after 72 days at h = 33 cm, and VC was detected after 121 days. 3.1.4.7  VOCs in the headspace As shown in Figure 3.29, TCE was detected in the headspace on day 79, and VC was detected on day 105. This occurred slightly before they were detected in the highest aqueous sampling port (days 86 and 121 respectively); as was the case for the ISCO column. A comparison between values measured in the headspace and in the uppermost aqueous sampling port after accounting for the dilution is shown in Figure 3.30. The concentrations in the headspace have been converted to equivalent aqueous concentrations for water in equilibrium with the headspace, as shown in the example for the ISCO column in section 3.1.3.6.    59 3.2 Discussion 3.2.1 TCE treatment 3.2.1.1  ISCO column In the ISCO column, an estimated 39% of the TCE was treated by the permanganate solution (see calculation in section 3.1.3.4). The incomplete oxidation of TCE, despite an excess of permanganate, is thought to be the result of insufficient contact between the TCE and the permanganate due to some combination of (1) spatial heterogeneity in the location of the TCE and permanganate, and (2) pore clogging with solid manganese oxides. Evidence of both spatial heterogeneities as well as pore clogging was observed during the dismantling of the column. Figure 3.31 shows photos taken during the deconstruction of the ISCO column. Sediments were removed in layers to observe the distribution of manganese oxides, untreated TCE, and clean sediments at discrete heights. No free-phase TCE was observed above the gravel layer. Below the gravel layer (the bottom of which was located at h = 8 cm) non-uniform distribution of manganese oxides was observed. Some globules of untreated TCE were also observed, apparently prevented from making contact with the main body of permanganate solution due to the manganese oxides (indicated by a red arrow). 3.2.1.2  Bioremediation column In the bioremediation column, TCE treatment occurred via co-metabolism and was thus dependent on microbial activity. Following injection of the acetate substrate, the bioremediation column did not begin producing significant quantities of gas for several weeks.  60 Although the microbial population had been maintained prior to filling the column in the batch reactors, and had been verified to be active, the microbes had not been exposed to high concentrations of TCE since their collection. In addition, atmospheric exposure during column filling and an influx of dissolved gases from the column water resulted in significant environmental changes. Stress on the microbial population, attributed to high TCE concentrations and new environmental conditions, resulted in a lowering of microbial activity at the beginning of the experiment, despite an abundance of substrate. For the first 6 weeks of the bioremediation experiment, very little gas was released to the headspace (cumulatively < 20 mL); most activity was confined to the contaminant zone. As such, no TCE treatment occurred near the beginning of the bioremediation column experiment. The appearance of daughter products 10 weeks after the start of the experiment in the treatment zone indicated some reductive dechlorination was occurring. However, the concentration of TCE remained close to solubility throughout the course of the experiment; the overall treatment of TCE was minimal (~4 % based on the calculation shown in Section 3.1.4.5). The VOC profiles throughout the experiment provide possible evidence for the occurrence of microbial activity outside of the treatment zone in the bioremediation column. cis-DCE was detected in the h = 13 cm and h = 20 cm ports from days 93-142, but was no longer detected in subsequent sampling events; this may be attributed to the reductive dechlorination of c-DCE to VC.    61 3.2.2 Gas transport As shown in the dissolved gas profiles for the ISCO column, N2 was initially present at concentrations in equilibrium with atmospheric conditions; its evolution throughout the experiment can be used as an indicator of gas production. High pCO2 values along the entire length of the column and stripping of the N2 was established early in the experiment due to the CO2 released from the permanganate oxidation. Ebullition was also observed in the form of bubbles visible rising to the headspace in the ~5 cm of sediment-free water immediately below the headspace.  Although less vigorous, the bioremediation column also exhibited gas ebullition. Both CO2 and CH4 were produced, and should have been produced in similar amounts based on the methanogenic degradation of acetate (shown in section 3.1.3.1). However, the greater solubility of CO2 resulted in ebullition tending to favor the transport of CH4 to the headspace, based on the molar ratio of CH4/CO2 in the headspace (~1.5x more CH4 by the end of the experiment). 3.2.3 VOC transport VOC transport was observed in both the ISCO and bioremediation columns, indicated by dissolved concentrations along the length of the columns, and gaseous samples taken from the headspace. In both treatment columns, VOC vapour concentrations in the headspace were out of equilibrium with the aqueous TCE concentrations, when comparing the headspace with the water samples obtained from the uppermost aqueous sampling port. VOC vapors were detected in the headspace prior to being detected in the uppermost sampling port. This may be  62 attributed to the differing detection limits for VOCs in the gaseous and aqueous samples. That is, VOCs may have been present in the aqueous samples at concentrations below 5 mg/L. Alternatively, the earlier arrival of VOCs in the headspace may be indicative of gas ebullition and bubble transport, wherein VOC transport occurs at a rapid rate that does not allow for equilibration with the water column. Indeed, in both columns the early detection of VOCs in the headspace correlates with the period of high gas production.  In addition to the apparent ‘early arrival’ of VOCs to the headspace, for both columns the VOCs have lower concentrations in the headspace than would be expected based on the VOC concentration in the uppermost aqueous port. In the example calculated in Section 3.1.3.6, the expected aqueous TCE concentration at the top of the water column on day 10 in the ISCO column based on the gaseous TCE in the headspace was 3.16 mg/L; the observed concentration was 16 mg/L. The headspace concentrations were consistently low in comparison to the calculated expected concentrations, an issue that appeared greater for TCE than VC in the bioremediation column, and was significantly more pronounced in the ISCO column. There are several possible influencing factors for the apparently low VOC headspace concentrations.  Firstly, significant dilution will occur in the headspace with the initial atmospheric gas. In addition, there may be an impact due to the disparity between the location of the top sampling port and the headspace. As described in the methods section 2.2.3, the highest aqueous sampling port is located at a height of 40 cm, above which is another 3 cm of sediment, then an additional ~5 cm of water (height decreased throughout the experiment due to the removal of water). It is likely that aqueous samples taken from a location closer to the air/water interface  63 would have concentrations closer to those in the headspace. This is also likely the explanation for oxygen being depleted in the water column but remaining in the headspace in the bioremediation column. As O2 is not consumed in the headspace it remains throughout the course of the experiment but will diffuse slowly through the headspace/water interface; the h = 40 cm sampling port was evidently too low to detect any oxygen diffusing from the headspace. Finally, the rate of gas production seems to have an impact. In the ISCO column, which experienced very high rates of gas production in comparison to the bioremediation column (100+ mL/day vs. 5 mL/day respectively), a much greater disparity between headspace and aqueous VOC concentrations was observed.  The differing gas production rates and the differing amounts of TCE treatment observed between the two columns may also be a contributing factor to the final headspace VOC concentrations. The bioremediation column had a final TCE concentration in the headspace which stabilized around 500 ppm, despite less total gas generation, a lower rate of gas production, and less TCE treatment; the ISCO column had a final TCE concentration in the headspace of around 300 ppm. Neither of the remediation treatments in the two columns were successful at removing all of the TCE, however, the bioremediation column was significantly less successful than the ISCO column (4% vs 39%, respectively). The low amount of TCE treatment in the bioremediation column may have resulted in more contaminant being available to transfer into exsolved gases, and the subsequent higher VOC concentration in the headspace.    64 3.2.4 Diffusion TCE was observed in the h = 13 cm sampling port in the control column after 86 days, but was not detected in any higher sampling ports, nor was it found in the headspace. Based on the results from the control column, it can be inferred that diffusion did not have a significant impact on VOC transport in the ISCO column. The bulk of the TCE transport observed in the ISCO column occurred within < 2 months, a time scale over which TCE diffusion in the columns is negligible.  Additionally, the concentrations observed in the control column were orders of magnitude below those observed in the ISCO column.  Conversely, the process of diffusion likely had some impact on the bioremediation column, since the experiment duration was nearly double that of the ISCO column. TCE was detected in the control column’s h = 13 cm port after 86 days; using the calculated effective diffusion coefficient from the control column results, TCE concentrations would reach 5 mg/L (assuming a source concentration at solubility) in the next highest port (h = 20 cm) in ~500 days (see Figure 3.32). As such, diffusion of TCE in the bioremediation column likely impacted the concentrations observed low in the column (h = 13 cm). However, based on the measurements from the control column, diffusion alone could not account for the observed transport of VOCs to higher locations in the column and into the headspace.    65 3.3 Significance of findings 3.3.1 VOC transport The process of gas exsolution and ebullition has been observed and quantified in laboratory studies and field sites (Amos and Mayer, 2006b; DelSontro et al., 2010; Jones et al., 2014); here the impact of these processes on the transport of VOCs in the subsurface was investigated. VOCs are partitioned into the exsolved gas phase (containing CO2 and CH4) when in contact with the dissolved phase (TCE and VC) or free product (TCE). In both columns, VOC concentrations increased and stabilized generally concurrently with gas ebullition. In the ISCO column, TCE was detected in the headspace as well as found dissolved throughout the length of the water column. Despite dilution in the headspace, concentrations reached ~300 ppm in the headspace- a minor impact with respect to total mass in the treatment zone, but significant when considering the inhalation exposure limits of TCE- 10 ppm for 8-hour time weighted average, 25 ppm for short-term exposure limit (WorkSafeBC, 2015), and 0.1 ppm for chronic (continuous average annual) exposure (OEHHA Office of Environmental Health Hazard Assessment, 2014). In the enhanced bioremediation column, TCE and VC were detected in the column headspace. TCE stabilized in the headspace around 500 ppm, and VC concentrations were around 1380 ppm at the end of the experiment. The inhalation exposure limits for vinyl chloride are more stringent than that of TCE- 1 ppm for 8-hour time weighted average (WorkSafeBC, 2015), and 5 ppm for short term (15 minutes) exposure (OSHA, 2012) (no chronic exposure guidelines available for VC). TCE was transported earlier than VC, as TCE daughter products did not accumulate in the contamination zone until TCE co-metabolism was  66 underway. Despite orders of magnitude higher concentrations of TCE than VC in the contamination zone (the highest concentration of VC was 25 mg/L), VC vertical transport with ebullition was dominant due to the differing Henry’s Constants. The dimensionless Henry’s Constants give an indication of how readily dissolved VOCs will partition into the gas phase- at 20°C, KH’(TCE) = 0.41, and KH’(VC) = 1.18 (NIST, 2015).  That is, the VC will partition more readily into the gas phase, resulting in the observed high concentration of VC in the headspace of the bioremediation column.  The process of VOC transport via gas exsolution and ebullition during remediation may be significant with respect to VOC toxicity and exposure. If transported to the vadose zone, there exists the possibility of VOC off-site migration or sub-slab intrusion. The potential for the transport of the daughter product vinyl chloride away from a contaminant treatment zone, as observed in the bioremediation column, results in particular concerns. VC poses a greater health threat in comparison to TCE or DCE, and is also more difficult to treat; removing it untreated from areas equipped for remediation (presence of injection wells, for example) will pose a threat to the success of a remediation project. In addition to health concerns, the migration of VOCs to soil vapour will increase the size of the contaminated area, which will require additional treatment. The installation of a soil vapour extraction (SVE) system on susceptible contaminated sites undergoing remediation may be necessary to contain a vapour plume.    67 3.3.2 Soil vapour intrusion and indoor air concentrations The concentrations measured in the headspace of the columns (TCE ~300 ppm in the ISCO column, TCE ~500 ppm and VC ~1380 ppm in the bioremediation column) indicate that substantial transfer of VOCs to the vadose zone is possible. Zones of reduced pressure under basements result in pressure gradients, which will cause an influx of gas from the vadose zone, i.e. soil vapour intrusion. Potential VOC intrusion to underground structures (i.e. basements) exhibits a human health hazard; low exposure limits for VOCs mean even small quantities of vapour intrusion may result in indoor air concentrations above standards. Indeed, indoor air monitoring in a former industrial site in Oregon overlying an enhanced bioremediation project exhibited indications of unintentional VOC transfer during remediation, which provided the motivation for this study. This site, as well as a second site in Montana, is discussed in further detail in Section 3.4. 3.4 Field sites 3.4.1 Applying experimental findings to a field scenario The findings from the column experiments cannot necessarily be applied completely to a field site undergoing VOC remediation. The column experiments were stagnant, and the impact of advective flow (and thus advective and dispersive transport) could be significant. Advective flow through the DNAPL source zone would create a dissolved plume and affect the transport of VOCs. Additional dissolution of VOCs would occur by bringing unsaturated water in contact with the pure phase TCE. The columns did not contain a vadose zone and were closed to the atmosphere. In a field site, VOCs transported to the vadose zone would experience rapid  68 dissipation of the gas, causing lower concentrations due to dilution, but potentially rapid spreading.   3.4.2 Bozeman Solvent Site The Bozeman Solvent Site (BSS) is a US EPA superfund site in Bozeman, Montana. Historically the site was used as a shopping centre, which had a dry cleaning establishment that began operations in 1960 and operated under a variety of owners until 1993. Tetrachloroethylene (PCE) was detected in a public water supply well in 1989 and traced back to the shopping centre, where it was determined that an abandoned/disconnected septic tank system was the source of the contamination. Dry cleaning operations discharged PCE into the sewer line, which was then released through leaks, defects, and the disconnected tank. Once the site investigation began, it was determined that the PCE contamination had spread to soil, groundwater, and soil vapour (Montana Department of Environmental Quality, 2011b).  The conceptual model developed for the site includes the septic tank and sewer line as primary sources of contamination. A pilot test was conducted in 2008 on site to investigate the suitability of enhanced bioremediation to treat the source zone and dissolved plume of PCE, using a commercial edible oil substrate. During the pilot test, soil vapour concentrations were monitored. The PCE, TCE, DCE, and VC concentrations measured before and after the pilot test are summarized in Table 3.6 (Montana Department of Environmental Quality, 2011a). PCE, TCE, and DCE increased substantially in the soil vapor, although they remain below their inhalation exposure limits. VC, which was previously undetected on site both in soil vapour and in groundwater, increased to 1800 μg/m3 in the pilot test area. Immediately adjacent to the  69 treatment area, VC was detected at a concentration of 4600 μg/m3 in a soil vapour probe, in excess of the 2575 μg/m3 (1 ppm) exposure limit, indicating transport away from the treatment zone. Methane was also generated and detected in the soil vapour during the pilot test, providing a transport mechanism for the VOCs via partitioning into the bubbles (Nicklin Earth & Water Inc., 2011). The pilot test determined the site was a good candidate for enhanced bioremediation, and a site-wide treatment of soybean oil was applied in February 2014.  A soil vapour extraction system was installed to collect methane and VC vapors, and equipped with a granulated activated carbon filter to treat off-gas. Soil vapour monitoring indicated that the soil vapour extraction system was successfully removing VC vapors; soil VC concentrations post-injection did not exceeded 1 ppm (Cardno ATC, 2015). 3.4.3 Oregon site The second site exhibiting likely VOC migration from remediation activities was an industrial site in Oregon. The site detected TCE, DCE, and VC in shallow groundwater in 2002, which was attributed to contamination from a former vapour degreaser operating on site until 1992. The site had both source zone contamination as well as an associated dissolved plume. An enhanced bioremediation project involving the injection of vegetable oil as a primary substrate began in 2005. Two years later, TCE treatment continued in the source zone but was no longer actively treating the plume concentrations. Reductive dechlorination was confirmed to occur, as well as TCE partitioning into the vegetable oil in the source zone. Soil vapour concentrations and indoor air concentrations in the basement of a building overlying the treatment zone were measured, and are summarized in Table 3.7. Soil vapour TCE  70 concentrations did not have a particularly significant increase following the bioremediation, however those for cis-DCE and VC did, indicating VOC transport to the vadose zone and subsequent vapour intrusion to the basement of the overlying building (Landau Associates, 2008; Oregon Department of Environmental Quality, 2008). 3.5 Impacts Results from the column experiments indicated substantial transfer of VOCs to the headspace via gas exsolution and ebullition. The role of diffusion was very small; the transfer of VOCs was observed at rates and concentrations that diffusion alone could not account for. These findings confirm that aggressive remediation methods can lead to gas production and induce vertical transport of VOCs away from the treatment zone via gas exsolution and ebullition. As such, the potential for unintentional contaminant transfer to the vadose zone should be taken into consideration when treating VOCs to avoid release into the atmosphere or into underground structures via soil vapour intrusion, such as the use of soil vapour monitoring system and a contingency plan of installing a soil vapour extraction system if needed. This study also suggests that the suitability of gas-generating remediation techniques in proximity to buildings and in populated areas should be evaluated with care.     71 3.6 Figures  Figure 3.1- TCE concentrations from the h = 13 cm port on the control column.    Figure 3.2- Measured TCE concentrations from the h = 13 cm port on the control column, with simulated diffusion (orange dashed line) using a diffusion coefficient of 2.6 × 10-11 m2/s and a Fickian diffusion model. Grey line indicates instrument’s detection limit for TCE.  05101520250 50 100 150 200TCE Concentration (mg/L) Elapsed time (days) 0510152025300 20 40 60 80 100 120 140 160 180TCE Concentration (mg/L) Elapsed time (days)  72     Figure 3.3- Permanganate pooling in the bottom of the column following injection to the treatment zone of the ISCO column. Top photo- t = 5 minutes, bottom photo- t = 15 minutes. Desaturation of sand due to gas generation indicated with red arrows on bottom photo, as well as bubbling in void space near the sampling port.  73  Figure 3.4- Screenshots from video clip showing TCE treatment and movement following injection of permanganate, approximately 30 minutes after injection. Timescale: a = 0s, b = 12s, c = 21s, d = 29s. Active movement of TCE visible in Video 3.1. a. b. c. d.  74  Figure 3.5- Example of temporary void spaces appearing due to gas bubbles in the ISCO column, located near the 40 cm sampling port. T = 4 days following permanganate injection. Void spaces had closed by the following day.   Figure 3.6- Example of TCE appearance and disappearance in the ISCO column in the gravel layer. T = 1 day (left) and 4 days (right) following permanganate injection. Also note sand desaturation due to gas generation.   75   Figure 3.7- Appearance of the treatment zone in the ISCO column, 44 days following permanganate injection, showing precipitated manganese oxide solids.     76  Figure 3.8- Gas production and headspace overpressure in the ISCO column. Pressure measurements (blue, right axis) were obtained from pressure transducer in the headspace, and cumulative gas released to the headspace (green, left axis) was calculated based on headspace volume and pressure at the time of the reading. The orange markers indicate the adjusted gas release after compensating for gas lost during sampling. Sampling events are indicated in red, and venting is shown in purple.  77  Figure 3.9- Gas production rate, calculated between each sampling event, ISCO column.    0.020.040.060.080.0100.0120.00 20 40 60 80 100Gas production rate (mL/day) Elapsed time (days)  78       Figure 3.10- Dissolved gas concentrations for select sampling events, ISCO column. Argon is not displayed for the sake of clarity; concentrations remain below 1% (0.01 atm). Data from all sampling events are shown in Appendix B. 5152535450 0.5 1Height (cm) Gas pressure (atm) t = 0d 5152535450 0.5 1Height (cm) Gas pressure (atm) t = 2d 5152535450 0.5 1Height (cm) Gas pressure (atm) t = 6d 5152535450 0.5 1Height (cm) Gas pressure (atm) t = 16d 5152535450 0.5 1Height (cm) Gas pressure (atm) t = 91d 512340P tot [atm]N₂ [atm] O₂ [atm] CO₂ [atm]  79    Figure 3.11- Dissolved gas concentrations from h = 6.5 cm (top panel) and h = 33 cm (bottom panel), ISCO column.      00.10.20.30.40.50.60.70.80.90 20 40 60 80 100Gas pressure (atm) Elapsed time (days) N₂ O₂ CO₂ h = 6.5 cm 00.10.20.30.40.50.60.70.80.90 20 40 60 80 100Gas pressure (atm) Elapsed time (days) h = 33 cm  80    Figure 3.12- Compositional gas analysis of the headspace, ISCO column. Upper figure shows the analytes indicated on the legend; the bottom figure displays only Ar and VOCs in order to observe the changes occurring in the low concentration gases.   0.0000.1000.2000.3000.4000.5000.6000.7000.8000.9000 10 20 30 40 50 60 70 80 90 100Gas pressure (atm) N₂ O₂ Ar CO₂ VOCs0.0000.0050.0100.0150.0200 10 20 30 40 50 60 70 80 90 100Gas pressure (atm) Elapsed time (days)  81  Figure 3.13- TCE concentrations from aqueous samples throughout the course of the experiment on select sampling days, ISCO column. Data from all sampling events are shown in Appendix B. 010203040500 30 60 90 120Height (cm) TCE concentration (mg/L) Initial2 days6 days16 days30 days58 days91 daysTreatment Zone: [TCE] > 1000 mg/L  82    Figure 3.14- TCE concentration in treatment zone, ISCO column. 100010501100115012000 20 40 60 80 100Concentration (mg/L) Elapsed time (days)  83  Figure 3.15- TCE concentration in headspace, ISCO column.   Figure 3.16- Comparison of TCE concentrations at the highest aqueous port (h = 40 cm) and in the headspace, after converting headspace concentrations to equivalent aqueous concentrations.   0501001502002503003500 20 40 60 80 100Concentration (ppm) Time (days) 0510152025300 20 40 60 80 100Concentration (mg/L) Elapsed Time (days) TCE in headspace,aqueous equivalentTCE [h = 40 cm] 84  Figure 3.17- Cumulative gas production from the batch reactors. First substrate addition occurred on May 21, subsequent substrate addition schedule is shown with coloured arrows; addition volume and concentration shown in Table 3.2.   85  Figure 3.18- Screenshots from a video showing a bubble emerging from the sediments in the bioremediation column on t = 72 d, with red arrow indicating location of the bubble. Total elapsed time from left frame to right frame = 0.1 s. Video 3.1 may be viewed online.    86  Figure 3.19- Gas production and headspace overpressure in bioremediation column. Pressure measurements (blue, right axis) were obtained from pressure transducer in the headspace, and cumulative gas released to the headspace (green, left axis) was calculated based on headspace volume and pressure at the time of the reading. The orange markers indicate the adjusted gas release after compensating for gas lost during sampling. Sampling events are indicated in red.  87  Figure 3.20- Gas production rate, calculated between each sampling event, bioremediation column.   0.01.02.03.04.05.06.00 50 100 150 200Gas production rate (mL/day) Elapsed time (days)  88             Figure 3.21- Dissolved gas profiles for select sampling events, bioremediation column. Argon is not displayed for the sake of clarity; concentrations remain below 1% (0.01 atm). Data from all sampling events are shown in Appendix C. 5152535450 1Height (cm) t = 0d 5152535450 1t = 24d 5152535450 1t = 37d 5152535450 1t = 51d 5152535450 1Height (cm) t = 58d 5152535450 1t = 65d 5152535450 1t = 72d 5152535450 1t = 93d 5152535450 1Height (cm) Gas Pressure (atm) t = 105d 5152535450 1Gas Pressure (atm) t = 142d 5152535450 1Gas Pressure (atm) t = 175d P tot [atm]N₂ [atm] O₂ [atm] CO₂ [atm] CH₄ [atm]  89   Figure 3.22- Dissolved gas concentrations from h = 6.5 cm (top panel) and h = 33 cm (bottom panel), bioremediation column.     00.10.20.30.40.50.60.70.80.90 50 100 150Gas pressure (atm) Elapsed time (days) N₂ O₂ CO₂ CH₄ h = 6.5 cm 00.10.20.30.40.50.60.70.80.90 50 100 150Gas pressure (atm) Elapsed time (days) N₂ O₂ CO₂ CH₄ h = 33 cm  90     Figure 3.23- Compositional gas analysis of the headspace, bioremediation column. Upper figure shows the six analytes indicated on the legend; the bottom figure displays neither nitrogen nor oxygen in order to observe the changes occurring in the low concentration gasses.  0.0000.1000.2000.3000.4000.5000.6000.7000.8000.9000 20 40 60 80 100 120 140 160 180 200Gas pressure (atm) N₂ O₂ Ar CO₂ CH₄ VOCs0.0000.0050.0100.0150.0200.0250.0300 20 40 60 80 100 120 140 160 180 200Gas pressure (atm) Elapsed time (days)  91    Figure 3.24- VOC concentrations in the contamination zone, bioremediation column. Note that TCE concentrations are shown on the secondary (right) axis, and DCE and VC concentrations are on the primary (left) axis due to their differing orders of magnitude.  020040060080010001200051015202530350 20 40 60 80 100 120 140 160 180Concentration (mg/L)- TCE Concentration (mg/L)- c-DCE, t-DCE, VC Elapsed time (days) c-DCEt-DCEVCTCE (secondary axis) 92   Vsection [cm3] Vwater [mL] CVC [mg/L] mVC [mg] nVC [× 10-5] 766 268 3.3 0.89 1.43 530 186 3.7 0.68 1.09 511 179 6.0 1.07 1.72 530 186 12.0 2.23 3.56 530 186 15.7 2.91 4.65 517 181 23.3 4.22 6.76 Total moles VC = 1.92 × 10-4 Figure 3.25- Column segments used in calculations for TCE treatment estimate in the bioremediation column. Calculations are based on vinyl chloride concentrations throughout the length of the column at the completion of the experiment (day 175).      V6 V5 V4 V3 V2 V1  93                  Figure 3.26- Aqueous VOC concentrations measured in the enhanced bioremediation column throughout the course of the experiment. No VOCs were measured outside of the contamination zone prior to day 44, so early data are not shown. Note that scale is cut off at 25 mg/L; see Figure 3.19 for full scale. Data are shown in Appendix C.  5152535450 20Height (cm) t=44d 5152535450 20t=51d 5152535450 20t=58d 5152535450 20t=65d 5152535450 20Height (cm) t=72d 5152535450 20t=79d 5152535450 20t=86d 5152535450 20t=93d 5152535450 20Height (cm) t=105d 5152535450 20t=114d 5152535450 20t=121d 5152535450 20t=128d 5152535450 20Height (cm) Concentration (mg/L) t=135d 5152535450 20Concentration (mg/L) t=142d 5152535450 20Concentration (mg/L) t=162d 5152535450 20Concentration (mg/L) t=175d TCE c-DCE t-DCE VC 94                  Figure 3.27- Aqueous VOC concentrations measured in the enhanced bioremediation column throughout the course of the experiment. No VOCs were measured outside of the contamination zone prior to day 44, so early data are not shown. Note that y-axis is log-scale.  5152535451 100Height (cm) t=44d 5152535451 100t=51d 5152535451 100t=58d 5152535451 100t=65d 5152535451 100Height (cm) t=72d 5152535451 100t=79d 5152535451 100t=86d 5152535451 100t=93d 5152535451 100Height (cm) t=105d 5152535451 100t=114d 5152535451 100t=121d 5152535451 100t=128d 5152535451 100Height (cm) Concentration (mg/L) t=135d 5152535451 100Concentration (mg/L) t=142d 5152535451 100Concentration (mg/L) t=162d 5152535451 100Concentration (mg/L) t=175d TCE c-DCE t-DCE VC 95   Figure 3.28- VOC concentrations from h = 13 cm (top panel) and h = 33 cm (bottom panel), bioremediation column.     05101520253035400 50 100 150Concentration (mg/L) Elapsed time (days) h = 13 cm 024681012141618200 50 100 150Concentration (mg/L) Elapsed time (days) TCEc-DCEt-DCEVCh = 33 cm  96   Figure 3.29- VOC concentrations in headspace of bioremediation column; no isomers of DCE were detected.    Figure 3.30- Comparison of VOC concentrations at the highest aqueous port (h = 40 cm) and in the headspace, after converting headspace concentrations to equivalent aqueous concentrations.  050010001500200025000 20 40 60 80 100 120 140 160 180 200Concentration (ppm) Elapsed time (days) TCE (ppm)VC (ppm)024681012140 20 40 60 80 100 120 140 160 180 200Concentration (mg/L) Elapsed Time (days) TCE in headspace,aqueous equivalentTCE [h=40cm]VC in headspace,aqueous equivalentVC [h=40cm] 97  Figure 3.31- Photos from the ISCO column deconstruction. Top photos show down-column view with sediments excavated to a height of 8 cm (top left) and 6 cm (top right), indicating non-uniform distribution of permanganate. Bottom left photo was taken during deconstruction through the glass wall of the column, showing untreated TCE (pink) blocked from the permanganate zone by manganese oxides.  Bottom right photo shows sediments from the contaminated zone after removal from the column; distribution of manganese oxides is non-uniform.    98  Figure 3.32- Estimated time for diffusive transport of TCE to the sampling ports from a source concentration at solubility in the treatment zone.   0510152025303540450 200 400 600 800 1000 1200 1400Height (cm) Time (days) 5 mg/L50 mg/L100 mg/L 99 3.7 Tables Table 3.1- Gas loss estimates from sampling events, ISCO column Elapsed days Sample date Pi (psi) Pf (psi) Calculated Pf (psi) % diff Gas loss (L) 2 3/12/15 12:30 PM 2.752 2.714 2.742 -1.02 0.015 6 3/16/15 10:30 AM 2.764 2.724 2.755 -1.12 0.016 10 3/20/15 9:00 AM 3.387 3.34 3.375 -0.91 0.013 16 3/26/15 3:00 PM 1.404 1.377 1.399 -1.63 0.024 23 4/2/15 11:00 AM 1.529 1.499 1.523 -1.60 0.023 30 4/9/15 11:00 AM 1.467 1.446 1.461 -1.07 0.016 37 4/16/15 12:00 PM 1.763 1.729 1.757 -1.62 0.024 44 4/23/15 11:00 AM 1.941 1.910 1.934 -1.23 0.018 51 4/30/15 11:30 AM 2.045 2.035 2.038 -0.13 0.0021 58 5/7/15 2:00 PM 2.156 2.133 2.149 -0.75 0.011 65 5/14/15 10:00 AM 2.248 2.226 2.240 -0.62 0.009 72 5/21/15 11:30 AM 2.264 2.254 2.256 -0.08 0.0011 79 5/28/15 10:30 AM 2.306 2.296 2.298 -0.08 0.0011 91 6/9/15 9:00 AM 2.351 2.338 2.342 -0.19 0.003      Sum. 0.173      Avg. 0.013  Pi is the headspace pressure measured prior to sampling Pf is the headspace pressure measured after sampling 1Below pressure transducer accuracy; not included in sum      100 Table 3.2- Substrate addition schedule for batch reactors Reactor Date Concentration (g/L) Volume (mL)  Sed 1 + Glucose May 21, 2014 2 1.5 June 10, 2014 20 1.5 Aug 11, 2014 20 1.5 Sed 1 + Acetate May 21, 2014 2 1.5 June 16, 2014 20 1.5 Aug 19, 2014 20 1.5 Sed 1 + Biosolids May 21, 2014 1 1.5 Sed 2 + Glucose May 21, 2014 2 1 June 23, 2014 20 1 Aug 11, 2014 20 1 Sed 2 + Acetate May 21, 2014 2 1 June 10, 2014 20 1 July 25, 2014 20 1 Sept 19, 2014 20 1 Sed 2 + Biosolids May 21, 2014 1 1 1Unknown carbon concentration in biosolids    101 Table 3.3- Gas production from batch reactors Reactor Date Added substrate (mg) Produced gas since last substrate addition (mL) Total gas production (mL) Max theoretical gas production (mL) Efficiency (%) Sed 1 + Glucose May 21, 2014 3 0.4 9.2 47.1 19.5 June 10, 2014 30 3.8 Aug 11, 2014 30 4.8 Sed 1 + Acetate May 21, 2014 3 2.9 27.6 34.5 80 June 16, 2014 30 10.2 Aug 19, 2014 30 14.5 Sed 1 + Biosolids May 21, 2014 1 0.8 0.8 1  Sed 2 + Glucose May 21, 2014 2 0.4 17.2 32.1 53.6 June 23, 2014 20 5.8 Aug 11, 2014 20 11 Sed 2 + Acetate May 21, 2014 2 0.7 9.2 22.9 40.2 June 10, 2014 20 2.2 July 25, 2014 20 2.9 Sept 19, 2014 20 3.4 Sed 2 + Biosolids May 21, 2014 1 2.2 2.2 1  1Unknown carbon concentration in biosolids    102 Table 3.4- Gas loss estimates for bioremediation column Elapsed days Sample Date Pi (psi) Pf (psi) Calculated Pf (psi) % diff Gas loss (L) 30 3/26/15 1:30 PM 0.090 0.089 0.090 -0.74 0.011 37 4/2/15 1:00 PM 0.099 0.098 0.099 -0.65 0.009 65 4/30/15 11:00 AM 0.928 0.921 0.924 -0.40 0.006 93 5/28/15 11:00 AM 1.595 1.581 1.589 -0.53 0.008 105 6/9/15 10:30 AM 1.696 1.686 1.691 -0.30 0.005      Sum 0.039 Pi is the headspace pressure measured prior to sampling Pf is the headspace pressure measured after sampling In all other sampling events, gas loss was below pressure transducer accuracy Table 3.5- CO2 and CH4 in column at day 175  CO2 CH4 pavg [atm] 0.18 0.53 KH [mol∙L-1∙atm-1] 3.43 × 10-2 1.38 × 10-3 Moles of dissolved gas  9.75 × 10-3 1.16 × 10-3 Moles of gas in headspace 1.37 × 10-3 1.96 × 10-3 Total moles 1.11 × 10-2 3.11 × 10-3 Excess moles CO2 0.008   Table 3.6- Bozeman Solvent Site highest reported soil vapour concentrations before and after enhanced bioremediation pilot test   Soil Vapour Concentrations [mg/m3]  Pre-pilot test1 Post-pilot test2 PCE 4.1 4800 TCE  0.056 550 cis-1,2-DCE  7.6 × 10-4 150 VC  n/d 1800 1Pre-pilot test soil vapour concentrations obtained from soil vapour probes SV-1, SV-2, SV-3, SV-8, and SV-9, which are the closest (within ~500 ft) measurements to the location of the pilot test (Montana Department of Environmental Quality, 2011a, Fig. 12) 2Pilot test soil vapour concentrations obtains from soil gas probes SG-1 through SG-11 located within the pilot test area, monitored from 2008-2009 (Montana Department of Environmental Quality, 2011a, Table 3)     103 Table 3.7- Oregon industrial site soil vapour and indoor air concentrations before and during enhanced bioremediation treatment  Pre-injection Post-injection  Soil vapour [mg/m3]1` Indoor air [μg/m3]2  Soil vapour [mg/m3]1 Indoor air [μg/m3]3  TCE  1300-2400 2.4 560-3000 13-27 cis-DCE  11-12  350-940 1.1-11 VC  < 4.6  6.2-68 0.17-0.57 1Soil vapour monitoring data from sub-slab soil vapour probes MW-26 and MW-27. Pre-injection measurements from 2005, post-injection measurements from 2006-2007 (Landau Associates, 2008, Table 7) 2Pre-injection indoor air concentrations measured in September 2002 (Oregon Department of Environmental Quality, 2008) 3Post-injection indoor air monitoring performed in basement of building overlying MW-26 and MW-27 from 2006-2007 (Landau Associates, 2008, Table 8) 104 Chapter 4: Conclusions and recommendations 4.1 Conclusions The principal aim of this research was to investigate the potential for mass transfer of volatile compounds into a discontinuous gas phase generated during remediation activities and transport of the volatiles during gas ebullition. Column experiments, including two treatment columns and one control column, were constructed and studied. The first treatment column considered the remediation of TCE via in situ chemical oxidation (ISCO) using sodium permanganate; the second treatment column simulated the enhanced bioremediation of TCE using acetate as a primary substrate. The control column contained TCE in the contamination zone but did not receive any treatment, in order to quantify the effects of diffusion. The data collected during the experiments include gas production rate and volume, collected using pressure transducers, as well as dissolved gas and VOC analysis along the length of the columns, and headspace gas analysis. The following conclusions are highlighted: 1. In both treatment columns, VOCs were transported from the treatment zone at the bottom of the column into the headspace. Despite dilution in the headspace, TCE and VC reached concentrations substantially exceeding guidelines for human inhalation exposure. The transport of the VOCs was associated with gas release from the remediation activities; increasing concentrations in the columns and breakthrough into the headspace occurred concurrently with an increased rate of gas production. VOC transport occurred via gas exsolution and ebullition, with diffusion having only a small role; VOCs were found throughout the length of both of the columns at concentrations  105 orders of magnitude higher than what was accounted for by diffusion in the control column. 2.  Both treatment columns exhibited gas exsolution and ebullition due to the applied remediation techniques. Bubbles were observed in both columns rising to the headspace, and dissolved gas analyses throughout the length of the columns revealed nonreactive gas stripping (pN2 decreasing) with the generation of  gases (CO2  in the ISCO column, CO2 and CH4 in the bioremediation column). The ISCO column, which exhibited a significantly higher rate and volume of gas production than the bioremediation column, had sufficient gas exsolution to lead to periodic de-saturation of the sediments and temporary opening of void spaces.  3. The rate of contaminant treatment and gas production appears to impact VOC transport. The enhanced bioremediation column reached a higher TCE concentration in the headspace and exhibited more complete mass transfer, despite slower gas transfer rates, a significantly smaller volume of gas produced, and a slower rate of contaminant treatment. This may be attributed to the longer residence time associated with the slower gas production and slower destruction of TCE, which allowed for greater contact between exsolved gases and dissolved VOCs. 4. Transport of VOCs in a discontinuous gas phase may occur too rapidly for compounds to reach equilibrium between the gaseous and aqueous phases. This was observed predominantly in the ISCO column. 5. TCE breakdown products generated during the reductive dechlorination of TCE in the enhanced bioremediation column were also transported. Vinyl chloride reached the  106 headspace, while DCE was detected dissolved in the column but was not found in the headspace. At a field site, this would have the potential for serious negative consequences; VC is a ‘worse’ contaminant than TCE with respect to exposure, and also a more difficult contaminant to treat. Transport away from the treatment zone will increase the size of the contaminated area. 6. Based on the greater transfer of TCE to the headspace as well as the transfer of hazardous daughter products in the bioremediation column, with only minimal TCE treatment in comparison to the ISCO column (4% vs. 39%), permanganate treatment may be a safer remediation option with respect to risk of mass transfer, despite higher gas production rates. 7. VOC properties had a strong effect on headspace concentrations. In the bioremediation column, despite dissolved concentrations two orders of magnitude lower in the treatment zone, vinyl chloride reached a higher concentration in the headspace than TCE. Vinyl chloride will partition more readily than TCE from the dissolved phase into the gas phase (KH’(TCE) = 0.41, HH’(VC) = 1.18 at 20°C (NIST, 2015)), resulting in the observed higher VC headspace concentration. 8. The key differences between the column experimental setup and a field scenario include a lack of advective (and dispersive) transport, and a fixed headspace rather than a vadose zone. The impact of a vadose zone on VOCs transported via gas exsolution and ebullition would be significant. If transported to the vadose zone, VOC concentrations would be diluted; however, there also exists the potential for rapid lateral and vertical transport. The tendency for pressure gradients to build up between the vadose zone  107 and underground structures can result in soil vapour intrusion into buildings, and thus increases the potential for exposure to VOCs. 9. The threat to human health via soil vapour intrusion suggests the suitability of gas-generating remediation techniques of volatile contaminants in proximity to buildings and in populated areas should be evaluated with care. 4.2 Recommendations  4.2.1 Experimental work In future experiments involving VOC compartment transfer during remediation activities, the limitations associated with these column experiments could be addressed. This may involve the inclusion of advective flow and the presence of a vadose zone. Other physical processes that may have an impact on VOC transport and thus could be included in future work are a fluctuating water table, and the inclusion of recharge water.  4.2.2 Remediation sites The potential for unintentional contaminant stripping and transport should be taken into consideration when treating VOCs to avoid contaminant release into the atmosphere or into underground structures via soil vapour intrusion. This may be addressed through the use of a soil vapour monitoring system to check whether VOC concentrations rise during remediation activities. In the case that unintentional transfer of VOCs from the saturated zone to the vadose zone is detected, the installation of a soil vapour extraction system may be necessary.     108 Bibliography Agency for Toxic Substances and Disease Registry (2014). Toxicological Profile for Trichloroethylene. Alvarez-Cohen, L., and McCarty, P.L. (1991). Product toxicity and cometabolic competitive inhibition modeling of chloroform and trichloroethylene transformation by methanotrophic resting cells. Appl. Environ. Microbiol. 57, 1031–1037. Amos, R.T., and Mayer, K.U. (2006a). Investigating ebullition in a sand column using dissolved gas analysis and reactive transport modeling. Environ. Sci. Technol. 40, 5361–5367. Amos, R.T., and Mayer, K.U. (2006b). Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling. J. Contam. Hydrol. 87, 123–154. ATSDR (2006). Public Health Statement: Vinyl Chloride. Bagley, D.M., and Gossett, J.M. (1990). Tetrachloroethene transformation to trichloroethene and cis-1,2-dichloroethene by sulfate-reducing enrichment cultures. Appl. Environ. Microbiol. 56, 2511–2516. Blicher-Mathiesen, G., McCarty, G.W., and Nielsen, L.P. (1998). Denitrification and degassing in groundwater estimated from dissolved dinitrogen and argon. J. Hydrol. 208, 16–24. Bohy, M., Dridi, L., Schäfer, G., and Razakarisoa, O. (2006). Transport of a mixture of chlorinated solvent vapors in the vadose zone of a sandy aquifer. Vadose Zone J. 5, 539. Böttcher, J., Strebel, O., Voerkelius, S., and Schmidt, H.-L. (1990). Using isotope fractionation of nitrate-nitrogen and nitrate-oxygen for evaluation of microbial denitrification in a sandy aquifer. J. Hydrol. 114, 413–424. Cardno ATC (2015). Revised Enhanced Bioremediation 100% Design Report, Bozeman Solvent Site (Billings, Montana).  109 Champ, D.R., Gulens, J., and Jackson, R.E. (1979). Oxidation–reduction sequences in ground water flow systems. Can. J. Earth Sci. 16, 12–23. Colt, J. (2002). Dissolved Gas Concentration in Water: Computation as Functions of Temperature, Salinity and Pressure (Elsevier Inc.). DelSontro, T., McGinnis, D.F., Sobek, S., Ostrovsky, I., and Wehrli, B. (2010). Extreme methane emissions from a Swiss hydropower reservoir: Contribution from bubbling sediments. Environ. Sci. Technol. 44, 2419–2425. Doherty, R.E. (2000). A history of the production and use of carbon tetrachloride, tetrachloroethylene, trichloroethylene and 1,1,1-trichloroethane in the United States: Part 1--Historical background; carbon tetrachloride and tetrachloroethylene. Environ. Forensics 1, 69–81. Droste, E.X., Marley, M.C., Parikh, J.M., Lee, A.M., Dinardo, P.M., Woody, B.A., Hoag, G.E., and Chheda, P.V. (2002). Observed enhanced reductive dechlorination after in situ chemical oxidation pilot test. In Remediation of Chlorinated and Recalcitrant Compounds, 2002: Proceedings of the Third International Conference on Remediation of Chlorinated and Recalcitrant Compounds, A.R. Gavaskar, and A.S.C. Chen, eds. (Monterey, California: Battelle Press). Ellis, D.E., Lutz, E.J., Odom, J.M., Buchanan, R.J., Bartlett, C.L., Lee, M.D., Harkness, M.R., and DeWeerd, K.A. (2000). Bioaugmentation for accelerated in situ anaerobic bioremediation. Environ. Sci. Technol. 34, 2254–2260. El Mamouni, R., Jacquet, R., Gerin, P., and Agathos, S.N. (2002). Influence of electron donors and acceptors on the bioremediation of soil contaminated with trichloroethene and nickel: laboratory- and pilot-scale study. Water Sci. Technol. 45, 49–54. EOS Remediation EOS 100 Product Information.  110 Freedman, D.L., and Gossett, J.M. (1989). Biological reductive dechlorination of tetrachloroethylene and trichloroethylene to ethylene under methanogenic conditions. Appl. Environ. Microbiol. 55, 2144–2151. Fries, M.R., Hopkins, G.D., McCarty, P.L., Forney, L.J., and Tiedje, J.M. (1997). Microbial succession during a field evaluation of phenol and toluene as the primary substrates for trichloroethene cometabolism. Appl. Environ. Microbiol. 63, 1515–1522. Frind, E.O., Molson, J.W., Schirmer, M., and Guiguer, N. (1999). Dissolution and mass transfer of multiple organics under field conditions: The Borden emplaced source. Water Resour. Res. 35, 683–694. Garbesi, K., and Sextro, R.G. (1989). Modeling and field evidence of pressure-driven entry of soil gas into a house through permeable below-grade walls. Environ. Sci. Technol. 23, 1481–1487. Griffin, T.W., and Watson, K.W. (2002). A comparison of field techniques for confirming dense nonaqueous phase liquids. Groundw. Monit. Remediat. 48–59. GSI Environmental (2014). Trichloroethylene. Guilbeault, M.A., Parker, B.L., and Cherry, J.A. (2005). Mass and flux distributions from DNAPL zones in sandy aquifers. Groundwater 43, 70–86. Health Canada (2005). Trichloroethylene- Guidelines for Canadian Drinking Water Quality: Supporting Documentation. Health Canada (2015). Conceptual Site Model Builder (Health Canada Contaminated Sites Division). Hoffman, F. (1993). Ground-water remediation using “smart pump and treat.” Ground Water 31, 98–106.  111 Hopkins, G.D., and McCarty, P.L. (1995). Field evaluation of in situ aerobic cometabolism of trichloroethylene and three dichloroethylene isomers using phenol and toluene as the primary substrates. Environ. Sci. Technol. 29, 1628–1637. Hopkins, G.D., Munakata, J., Semprini, L., and McCarty, P.L. (1993). Trichloroethylene concentration effects on pilot field-scale in-situ groundwater bioremediation by phenol-oxidizing microorganisms. Environ. Sci. Technol. 27, 2542–2547. Hunter, W.J. (2002). Bioremediation of chlorate or perchlorate contaminated water using permeable barriers containing vegetable oil. Curr. Microbiol. 45, 287–292. Jackson, P.D., Williams, J.F., Ma, L., Camps, A., Rochelle, C., and Milodowski, A.E. (2008). An Investigation Of The Exponent In Archie’s Equation: Comparing Numerical Modeling With Laboratory Data: Towards Characterising Disturbed Samples From The Cascadia Margin: Expedition 311. In 49th Annual Logging Symposium, (Society of Petrophysicists and Well-Log Analysts). Jellali, S., Benremita, H., Muntzer, P., Razakarisoa, O., and Schäfer, G. (2003). A large-scale experiment on mass transfer of trichloroethylene from the unsaturated zone of a sandy aquifer to its interfaces. J. Contam. Hydrol. 60, 31–53. Jones, D.L., and Healey, J.R. (2010). Organic amendments for remediation: Putting waste to good use. Elements 6, 369–374. Jones, K.L., Lindsay, M.B.J., Kipfer, R., and Mayer, K.U. (2014). Atmospheric noble gases as tracers of biogenic gas dynamics in a shallow unconfined aquifer. Geochim. Cosmochim. Acta 128, 144–157. Kao, C.M., and Prosser, J. (1999). Intrinsic bioremediation of trichloroethylene and chlorobenzene: field and laboratory studies. J. Hazard. Mater. 69, 67–79. Kästner, M. (1991). Reductive dechlorination of Tri-and tetrachloroethylenes depends on transition from aerobic to anaerobic conditions. Appl. Environ. Microbiol. 57, 2039–2046.  112 Landau Associates (2008). 2007 Annual Report Interim Remedial Action Measure and Supplemental Remedial Investigation. Lee, P.K.H., Warnecke, F., Brodie, E.L., Macbeth, T.W., Conrad, M.E., Andersen, G.L., and Alvarez-Cohen, L. (2012). Phylogenetic microarray analysis of a microbial community performing reductive dechlorination at a TCE-Contaminated Site. Environ. Sci. Technol. 46, 1044–1054. Lian, F., Chang, C., Du, Y., Zhu, L., Xing, B., and Liu, C. (2012). Adsorptive removal of hydrophobic organic compounds by carbonaceous adsorbents: A comparative study of waste-polymer-based, coal-based activated carbon, and carbon nanotubes. J. Environ. Sci. 24, 1549–1558. Little, J.C., Daisey, J.M., and Nazaroff, W.W. (1992). Subsurface transport of volatile organic contaminants into buildings. Lawrence Berkeley Laboratory, University of California. Prepared for the U.S. Department of Energy.  Mackay, D.M., and Cherry, J.A. (1989). Groundwater contamination: Pump-and-treat remediation. Environ. Sci. Technol. 23, 630–636. Magnuson, J.K., Stern, R.V., Gossett, J.M., Zinder, S.H., and Burris, D.R. (1998). Reductive dechlorination of tetrachloroethene to ethene by a two-component enzyme pathway. Appl. Environ. Microbiol. 64, 1270–1275. Marley, M.C., Hazebrouck, D.J., and Walsh, M.T. (1992). The application of in situ air sparging as an innovative soils and ground water remediation technology. Groundw. Monit. Remediat. 137–145. McCarty, P.L., Goltz, M.N., Hopkins, G.D., Dolan, M.E., Allan, J.P., Kawakami, B.T., and Carrothers, T.J. (1998). Full-scale evaluation of in situ cometabolic degradation of trichloroethylene in groundwater through toluene injection. Environ. Sci. Technol. 32, 88–100. Michalski, A., Metlitz, M.N., and Whitman, I.L. (1995). A field study of enhanced recovery of DNAPL pooled below the water table. Groundw. Monit. Remediat. 90–100.  113 Miller, G.D. (1982). Uptake and release of lead, chromium, and trace-level volatile organics exposed to synthetic well casings. In Proceedings of the Second National Symposium on Aquifer Restoration and Ground-Water Monitoring, (Dublin, OH), pp. 236–245. Montana Department of Environmental Quality (2011a). Proposed Cleanup Alternative for the Bozeman Solvent Site (Helena, Montana: Montana DEQ, Remediation Division). Montana Department of Environmental Quality (2011b). Bozeman Solvent Site Record of Decision (Helena, Montana). Mu, D.Y., and Scow, K.M. (1994). Effect of trichloroethylene (TCE) and toluene concentrations on TCE and toluene biodegradation and the population density of TCE and toluene degraders in soil. Appl. Environ. Microbiol. 60, 2661–2665. Mumford, K.G., Smith, J.E., and Dickson, S.E. (2008). Mass flux from a non-aqueous phase liquid pool considering spontaneous expansion of a discontinuous gas phase. J. Contam. Hydrol. 98, 85–96. Mumford, K.G., Dickson, S.E., and Smith, J.E. (2009). Slow gas expansion in saturated natural porous media by gas injection and partitioning with non-aqueous phase liquids. Adv. Water Resour. 32, 29–40. National Research Council, Board on Radioactive Waste Management, Water Science and Technology Board, Committee on Intrinsic Remediation, Commission on Geosciences, Environment and Resources, and Division on Earth and Life Studies (2000). Natural Attenuation for Groundwater Remediation (National Academies Press). Nicklin Earth & Water Inc. (2011). Feasibility Study Report: Bozeman Solvent Site (Bozeman, Montana). NIST (2015). Standard Reference Data.  114 Norris, R.D., Hinchee, R.E., Brown, R., McCarty, P.L., Semprini, L., Wilson, J.T., Kampbell, D.H., Reinhard, M., Bouwer, E.J., Borden, R.C., et al. (1993). In-situ bioremediation of ground water and geological material: A review of technologies (Dynamac Corp.). OEHHA Office of Environmental Health Hazard Assessment (2014). All OEHHA Acute, 8-hour and Chronic Reference Exposure Levels (chRELs) as of June 2014 (Air Toxicology and Epidemiology). Oregon Department of Environmental Quality (2008). Vapor Intrusion, PCC Structural Inc. OSHA (2012). Occupational Safety and Health Standards (United States Department of Labor). Pettyjohn, W.A., Dunlap, W.J., Cosby, R., and Keeley, J.W. (1981). Sampling ground water for organic contaminants. Ground Water 19, 180–189. REGENESIS Remediation Solutions Hydrogen Release Compound (HRC®). Rittmann, B.E., and Seagren, E. (1994). In Situ Bioremediation (Park Ridge, New Jersey: Noyes Publications). Roy, J.W., and Smith, J.E. (2007). Multiphase flow and transport caused by spontaneous gas phase growth in the presence of dense non-aqueous phase liquid. J. Contam. Hydrol. 89, 251–269. Sander, R. (1999). Compilation of Henry’s law constants for inorganic and organic species of potential importance in environmental chemistry (Max-Planck Institute of Chemistry, Air Chemistry Department Mainz, Germany). Schink, B. (1997). Energetics of syntrophic cooperation in methanogenic degradation. Microbiol. Mol. Biol. Rev. 61, 262–280. Schnarr, M., Truax, C., Farquar, G., Hood, E., Gonullu, T., and Stickney, B. (1998). Laboratory and controlled field experiments using potassium permanganate to remediate trichloroethylene and perchloroethylene DNAPLs in porous media. J. Contam. Hydrol. 29, 205–224.  115 Schroth, M.H., Oostrom, M., Wiersma, T.W., and Istok, J.D. (2001). In-situ oxidation of trichloroethene by permanganate: effects on porous medium hydraulic properties. J. Contam. Hydrol. 50, 79–98. Schwille, F. (1988). Dense Chlorinated Solvents in Porous and Fractured Media: Model Experiments (Lewis Publishers). Siegrist, R.L., Crimi, M.L., Munakata-Marr, J., Illangasekare, T., Dugan, P., Heiderscheidt, J., Petri, B., and Sahl, J. (2008). Chemical oxidation for cleanup of contaminated groundwater. In Methods and Techniques for Cleaning-up Contaminated Sites, M.D. Annable, M. Teodorescu, and P. Hlacinek, eds. (Springer Science & Business Media). Song, D.L., Conrad, M.E., Sorenson, K.S., and Alvarez-Cohen, L. (2002). Stable carbon isotope fractionation during enhanced in situ bioremediation of trichloroethene. Environ. Sci. Technol. 36, 2262–2268. Tyagi, M., da Fonseca, M.M.R., and de Carvalho, C.C.C.R. (2011). Bioaugmentation and biostimulation strategies to improve the effectiveness of bioremediation processes. Biodegradation 22, 231–241. United States Environmental Protection Agency (1996). Pump and Treat Groundwater Remediation- A Guide for Decision Makers and Practitioners. United States Environmental Protection Agency (2007). Trichloroethylene (TCE). United States Environmental Protection Agency (2015). Superfund Site Browser. US EPA, O. Table of Regulated Drinking Water Contaminants. West, O.R., Cline, S.R., Holden, W.L., Gardner, F.G., Schlosser, B.M., Thate, J.E., Pickering, D.A., and Houk, T.C. (1997). A full-scale demonstration of in situ chemical oxidation through recirculation at the X-701B site (Oak Ridge, Tennessee: Oak Ridge National Laboratory).  116 Wilson, J.T., and Wilson, B.H. (1985). Biotransformation of trichloroethylene in soil. Appl. Environ. Microbiol. 49, 242. WorkSafeBC (2015). Table of exposure limits for chemical and biological substances (Occupational Health and Safety Regulation 5.48). Wymore, R.A., Macbeth, T.W., Rothermel, J.S., Peterson, L.N., Nelson, L.O., Sorenson, K.S., Akladiss, N., and Tasker, I.R. (2006). Enhanced anaerobic bioremediation in a DNAPL residual source zone: Test Area North case study. Remediat. J. 16, 5–22. Yan, Y.E., and Schwartz, F.W. (1999). Oxidative degradation and kinetics of chlorinated ethylenes by potassium permanganate. J. Contam. Hydrol. 37, 343–365. Yin, Y., and Allen, H.E. (1999). In Situ Chemical Treatment (Pittsburgh, PA: Ground-Water Remediation Technologies Analysis Center).  117 Appendices Appendix A: Sample analysis Analysis for fixed gases was performed on a three channel Bruker 450 gas chromatograph equipped with a flame ionization detector (FID) and two thermal conductivity detectors (TCD), a HayeSep A column, and HayeSep Q column, and a Molsieve 13X column. The carrier gas used was helium. The oven was programmed to hold at 50°C for 3 minutes, ramp at 15°C/min to 180°C, and hold at 180°C for 5 minutes. The use of a heated injection port, heated to 250 °C, allowed for the injection of liquid samples. The instrument was operated with Galaxie software.  Analysis of VOCs was performed by GC/MS using an Agilent 6890 N gas chromatograph equipped with an Agilent 5975B mass spectrometer. Gas samples were directly injected using an autosampler. Aqueous samples were analyzed using static headspace extraction, whereby half the aqueous sample (0.5 mL) was extracted from the sample vial and injected into a headspace autosampler vial. The incubation period for headspace extraction was 10 minutes at 75°C. The headspace autosampler was coupled with a split/splitless injection port (250°C). The oven was programmed to hold at 40°C for 5 minutes, ramp at 8°C/min to 180°C, then ramp at 30°C/min to 250°C. The carrier gas used was helium. The mass spectrometer was operated in synchronous SIM (selected ion monitoring)/Scan mode. The instrument was operated with ChemStation software.  118 Appendix B: ISCO data Appendix B is one complete table that is too large to fit on a single page. The page numbers indicated on the graphic below show each segment’s placement in the overall table. Relevant column and row headings are included on each page.  p. 119 p. 120 p. 121 p. 122  119 Date     03/10/2015 03/12/2015 03/16/2015 03/20/2015 03/26/2015 04/02/2015 04/09/2015 04/16/2015 04/23/2015 Elapsed time (days)   0 2 6 10 16 23 30 37 44 Gas generated (mL)     0.0 265.0 674.0 734.0 850.0 862.0 856.0 914.5 932.8 Pressure (atm)   1.000 1.187 1.188 1.230 1.096 1.104 1.100 1.120 1.132 Headspace V (L)     1.414 1.42 1.426 1.432 1.438 1.444 1.45 1.456 1.462     port height (cm)                   Dissolved gases [atm] P(tot) 6.5 0.989 0.996 0.999 0.979 0.978 0.979 0.977 0.988 0.981 13 0.979 1.005 0.993 1.004 0.985 0.990   0.994 0.975 20 0.987 1.005 0.984   0.989 0.998 0.993 0.947   26.5 0.952 0.998 1.001 1.002 0.988 1.058 1.035 0.971 0.990 33 1.003 1.008 0.990 0.968 0.991   1.009 0.981 0.991 40 0.984 1.012 0.994 0.996 1.002 1.035 1.039 1.065 0.976 N₂ 6.5 0.776 0.385 0.168 0.162 0.165 0.158 0.154 0.148 0.143 13 0.765 0.402 0.204 0.199 0.181 0.174  0.168 0.142 20 0.780 0.416 0.263  0.201 0.205 0.198 0.163  26.5 0.745 0.426 0.355 0.305 0.221 0.274 0.274 0.205 0.204 33 0.779 0.533 0.272 0.264 0.241  0.237 0.217 0.226 40 0.776 0.543 0.299 0.259 0.268 0.301 0.297 0.323 0.218 O₂ 6.5 0.203 0.104 0.098 0.102 0.093 0.100 0.101 0.105 0.092 13 0.207 0.108 0.101 0.103 0.101 0.104   0.110 0.112 20 0.198 0.110 0.112   0.105 0.112 0.108 0.113   26.5 0.197 0.126 0.119 0.112 0.113 0.123 0.109 0.113 0.118 33 0.216 0.126 0.132 0.128 0.121   0.126 0.124 0.127 40 0.198 0.135 0.138 0.137 0.129 0.120 0.121 0.120 0.119 Ar 6.5 0.009 0.005 0.004 0.003 0.002 0.001 0.000 0.000 0.000 13 0.007 0.006 0.004 0.004 0.001 0.002  0.000 0.000 20 0.009 0.006 0.006  0.001 0.001 0.000 0.000  26.5 0.009 0.007 0.003 0.002 0.002 0.002 0.000 0.000 0.000 33 0.008 0.007 0.003 0.003 0.001  0.002 0.000 0.001 40 0.009 0.006 0.004 0.003 0.002 0.001 0.002 0.001 0.001 CO₂ 6.5 0.000 0.502 0.729 0.712 0.718 0.720 0.722 0.735 0.746 13 0.000 0.489 0.684 0.698 0.702 0.710   0.716 0.721 20 0.000 0.473 0.603   0.682 0.680 0.687 0.671   26.5 0.000 0.439 0.524 0.583 0.652 0.659 0.652 0.653 0.668 33 0.000 0.342 0.583 0.573 0.628   0.644 0.640 0.637 40 0.000 0.328 0.553 0.597 0.603 0.613 0.619 0.621 0.638    120 Date     03/10/2015 03/12/2015 03/16/2015 03/20/2015 03/26/2015 04/02/2015 04/09/2015 04/16/2015 04/23/2015 Elapsed time (days)   0 2 6 10 16 23 30 37 44     port height (cm)                   Headspace composition [atm] P(tot)   0.994 1.004 0.986 1.002 1.001 0.994 0.998 1.001 0.996 N₂  0.782 0.663 0.558 0.553 0.521 0.512 0.517 0.503 0.497 O₂   0.203 0.175 0.143 0.144 0.139 0.129 0.130 0.126 0.128 Ar   0.009 0.007 0.006 0.006 0.005 0.006 0.006 0.005 0.006 CO₂   0.000 0.159 0.279 0.299 0.336 0.347 0.345 0.367 0.365 Dissolved VOCs (mg/L) TCE 6.5 1066.0 1159.7 1126.7 1165.0 1159.0 1117.3 1162.3 1125.7 1124.7 13 0.0 24.0 57.3 64.3 72.7 77.7 80.3 83.0 85.3 20 0.0 5.2 28.0 31.7 36.0 43.3 55.3 55.0 58.7 26.5 0.0 0.0 17.0 22.0 27.0 29.0 33.7 43.0 46.0 33 0.0 0.0 15.3 15.3 15.3 21.3 25.7 27.7 29.3 40 0.0 0.0 16.0 16.0 15.3 16.3 17.3 18.3 19.3 Headspace VOCs [ppm] TCE   0.0 38.3 154.0 192.7 183.3 214.7 208.7 259.7 291.7    121 Date     4/30/2015 5/7/2015 5/14/2015 5/21/2015 5/28/2015 6/9/2015 Elapsed time (days)   51 58 65 72 79 91 Gas generated (mL)     943.987949 955.946982 966.025033 968.53582 973.750044 979.198977 Pressure (atm)   1.13915436 1.14673204 1.15296853 1.15404147 1.15692501 1.15994267 Headspace V (L)     1.468 1.474 1.48 1.486 1.492 1.498     port height (cm)             Dissolved gases [atm] P(tot) 6.5   0.995 1.000 0.982 0.972 0.989 13 0.980 0.993 0.988 0.985 0.975 0.996 20   0.978 0.980 0.990 0.995 0.997 26.5 1.080 0.981 0.979   0.980 0.968 33 0.800 0.961 0.976 0.979 0.977 0.985 40 1.028 1.000 1.015 0.996 0.976 0.995 N₂ 6.5  0.153 0.138 0.131 0.116 0.122 13 0.145 0.158 0.145 0.151 0.138 0.159 20  0.198 0.186 0.185 0.183 0.187 26.5 0.293 0.204 0.199 0.204 0.199 0.189 33 0.253 0.231 0.208 0.209 0.204 0.203 40 0.284 0.253 0.271 0.256 0.243 0.257 O₂ 6.5   0.106 0.109 0.102 0.110 0.110 13 0.105 0.108 0.112 0.109 0.108 0.101 20   0.105 0.102 0.117 0.112 0.097 26.5 0.117 0.112 0.109   0.104 0.106 33 0.108 0.109 0.117 0.120 0.125 0.128 40 0.119 0.117 0.120 0.118 0.109 0.105 Ar 6.5  0.000 0.000 0.000 0.000 0.000 13 0.000 0.000 0.000 0.000 0.000 0.000 20  0.000 0.000 0.000 0.000 0.000 26.5 0.000 0.000 0.000  0.000 0.000 33 0.000 0.000 0.000 0.000 0.000 0.000 40 0.000 0.000 0.000 0.000 0.000 0.000 CO₂ 6.5   0.736 0.753 0.749 0.746 0.757 13 0.730 0.727 0.731 0.725 0.729 0.736 20   0.675 0.692 0.688 0.700 0.713 26.5 0.670 0.665 0.671   0.677 0.673 33 0.439 0.621 0.651 0.650 0.648 0.654 40 0.625 0.630 0.624 0.622 0.624 0.633    122 Date     4/30/2015 5/7/2015 5/14/2015 5/21/2015 5/28/2015 6/9/2015 Elapsed time (days)   51 58 65 72 79 91     port height (cm)             Headspace composition [atm] P(tot)   0.978 1.009 0.992 0.989 1.002 1.002 N₂  0.495 0.502 0.488 0.483 0.492 0.491 O₂   0.129 0.131 0.129 0.131 0.129 0.128 Ar   0.006 0.005 0.005 0.006 0.006 0.007 CO₂   0.348 0.371 0.370 0.369 0.375 0.376 Dissolved VOCs (mg/L) TCE 6.5 1135.0 1116.3 1150.0 1147.0 1115.7 1146.7 13 87.3 87.0 91.0 90.7 90.7 92.7 20 61.3 62.7 63.0 61.7 62.7 63.0 26.5 47.3 51.0 50.7 48.3 45.7 46.3 33 30.7 31.3 30.7 31.0 30.0 31.0 40 21.3 21.3 20.7 21.0 20.7 22.0 Headspace VOCs [ppm] TCE   301.3 304.3 296.0 307.7 300.0 307.0    123 Appendix C: Enhanced bioremediation column data Appendix C is one complete table that is too large to fit on a single page. The page numbers indicated on the graphic below show each segment’s placement in the overall table. Relevant column and row headings are included on each page. p. 124 p. 126 p. 128 p. 125 p. 127 p. 129  124 Date     2/24/2015 3/3/2015 3/12/2015 3/20/2015 3/26/2015 4/2/2015 4/9/2015 4/16/2015 4/23/2015 Elapsed time (days)   0 7 16 24 30 37 44 51 58 Gas generated (mL)     0.01 0.67 5.30 6.26 13.76 14.66 17.57 27.83 61.97 Pressure (atm)   1.000 1.000 1.003 1.003 1.006 1.007 1.009 1.016 1.039 Headspace V (L)     1.41 1.42 1.42 1.43 1.43 1.44 1.45 1.45 1.46   port height (cm)          Dissolved gases [atm] P(tot) 6.5 0.998 0.979 0.961 0.980 0.990 0.974 0.987 1.001 0.999 13 0.993 0.987 0.988 0.971   1.020 0.971 0.965 0.996 20 0.995 0.984 0.993 0.989 0.966 0.987 0.995 0.985 0.994 26.5 0.971 0.998 0.989 0.971 0.975 0.986 0.985 0.998 0.967 33 0.990 0.980 0.993 0.988 0.975 0.974 0.989 0.985 0.992 40 0.995 0.978 0.994 0.993 0.982 0.983 0.992 0.986 0.990 N₂ 6.5 0.781 0.773 0.716 0.679 0.658 0.618 0.558 0.487 0.212 13 0.775 0.776 0.778 0.775  0.765 0.772 0.628 0.233 20 0.777 0.773 0.779 0.778 0.758 0.776 0.774 0.775 0.459 26.5 0.757 0.786 0.773 0.760 0.774 0.778 0.774 0.778 0.776 33 0.773 0.775 0.776 0.776 0.769 0.771 0.776 0.773 0.775 40 0.778 0.768 0.779 0.781 0.775 0.778 0.778 0.779 0.776 O₂ 6.5 0.208 0.192 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13 0.208 0.201 0.200 0.180   0.153 0.079 0.000 0.000 20 0.208 0.201 0.204 0.202 0.200 0.202 0.204 0.159 0.000 26.5 0.204 0.203 0.206 0.201 0.192 0.199 0.203 0.202 0.083 33 0.208 0.195 0.207 0.203 0.197 0.195 0.204 0.203 0.201 40 0.208 0.200 0.206 0.203 0.199 0.196 0.205 0.198 0.204 Ar 6.5 0.009 0.009 0.009 0.000 0.000 0.000 0.000 0.000 0.000 13 0.009 0.009 0.009 0.009  0.008 0.005 0.001 0.000 20 0.009 0.009 0.009 0.009 0.008 0.009 0.007 0.008 0.000 26.5 0.009 0.009 0.009 0.009 0.009 0.009 0.008 0.008 0.000 33 0.009 0.009 0.009 0.009 0.009 0.008 0.009 0.008 0.008 40 0.009 0.009 0.009 0.009 0.008 0.009 0.009 0.008 0.009 CO₂ 6.5 0.000 0.005 0.104 0.111 0.116 0.103 0.145 0.155 0.209 13 0.000 0.000 0.000 0.006   0.095 0.116 0.141 0.194 20 0.000 0.000 0.000 0.000 0.000 0.000 0.010 0.042 0.192 26.5 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.010 0.109 33 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.008 40 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 0.002 CH₄ 6.5 0.000 0.000 0.132 0.190 0.216 0.252 0.284 0.359 0.578 13 0.000 0.000 0.000 0.000  0.000 0.000 0.195 0.569 20 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.342 26.5 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 33 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 40 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000  125  Date     2/24/2015 3/3/2015 3/12/2015 3/20/2015 3/26/2015 4/2/2015 4/9/2015 4/16/2015 4/23/2015 Elapsed time (days)   0 7 16 24 30 37 44 51 58   port height (cm)          Headspace composition [atm] P(tot)   0.996 0.984 0.990 0.991 0.994 0.987 0.990 0.993 1.005 N₂  0.778 0.774 0.779 0.775 0.780 0.778 0.776 0.779 0.787 O₂   0.209 0.200 0.201 0.206 0.205 0.200 0.204 0.205 0.208 Ar  0.009 0.009 0.009 0.009 0.009 0.009 0.009 0.009 0.009 CO₂   0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.001 CH₄   0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 Dissolved VOCs [mg/L] TCE 6.5 924.7 1067.0 1103.0 1110.7 1128.0 1100.7 1107.3 1046.0 1109.0 13 0.0 0.0 0.0 0.0 0.0 4.0 5.5 10.7 16.3 20           0.0 0.0 0.0 5.2 26.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33                   40 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 c-DCE 6.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20      0.0 0.0 0.0 0.0 26.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33          40 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 t-DCE 6.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20           0.0 0.0 0.0 0.0 26.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33                   40 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 VC 6.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 13 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20      0.0 0.0 0.0 0.0 26.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33          40 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Headspace VOCs [ppm] TCE   0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 c-DCE  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 t-DCE   0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 VC   0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0     126 Date     4/30/2015 5/7/2015 5/14/2015 5/21/2015 5/28/2015 6/9/2015 6/18/2015 6/25/2015 Elapsed time (days)   65 72 79 86 93 105 114 121 Gas generated (mL)     96.96 120.06 137.18 153.84 165.69 176.65 183.12 186.53 Pressure (atm)   1.063 1.079 1.090 1.101 1.109 1.115 1.119 1.121 Headspace V (L)     1.46 1.47 1.48 1.48 1.49 1.49 1.50 1.51   port height (cm)         Dissolved gases [atm] P(tot) 6.5 0.990 1.024 1.007 1.024 0.990 0.984 0.970 0.978 13 0.993 1.000 0.997 0.992 0.989 1.007 1.000 0.997 20 0.993 0.998 0.978 0.977 0.998 0.994 1.008 0.999 26.5 0.994 1.008 0.977 0.964 0.987 0.997   1.003 33 1.005 1.033 1.001 0.998 0.994 0.991 1.024 1.009 40 0.993 0.894 0.990 0.992 0.994 1.004 1.011 1.000 N₂ 6.5 0.160 0.156 0.177 0.171 0.171 0.171 0.165 0.169 13 0.212 0.202 0.209 0.201 0.212 0.198 0.204 0.211 20 0.291 0.210 0.251 0.251 0.248 0.253 0.251 0.248 26.5 0.450 0.346 0.316 0.303 0.298 0.285  0.279 33 0.777 0.447 0.526 0.495 0.449 0.402 0.398 0.357 40 0.778 0.565 0.584 0.579 0.531 0.501 0.412 0.386 O₂ 6.5 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 20 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 26.5 0.000 0.000 0.000 0.000 0.000 0.000   0.000 33 0.151 0.000 0.000 0.000 0.000 0.000 0.000 0.000 40 0.204 0.125 0.000 0.000 0.000 0.000 0.000 0.000 Ar 6.5 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 20 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 26.5 0.000 0.000 0.000 0.000 0.000 0.000  0.000 33 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 40 0.003 0.001 0.001 0.000 0.001 0.001 0.000 0.002 CO₂ 6.5 0.222 0.276 0.274 0.280 0.302 0.294 0.297 0.288 13 0.201 0.284 0.292 0.294 0.292 0.319 0.304 0.284 20 0.192 0.259 0.230 0.231 0.256 0.239 0.248 0.241 26.5 0.195 0.228 0.202 0.201 0.214 0.229   0.231 33 0.077 0.141 0.152 0.105 0.139 0.119 0.152 0.139 40 0.008 0.203 0.103 0.060 0.091 0.103 0.101 0.083 CH₄ 6.5 0.609 0.592 0.556 0.572 0.516 0.519 0.508 0.520 13 0.580 0.514 0.496 0.497 0.485 0.490 0.492 0.502 20 0.510 0.529 0.497 0.495 0.494 0.502 0.509 0.510 26.5 0.349 0.433 0.459 0.459 0.476 0.483  0.492 33 0.000 0.445 0.322 0.398 0.405 0.469 0.474 0.513 40 0.000 0.000 0.302 0.352 0.370 0.399 0.498 0.529  127 Date     4/30/2015 5/7/2015 5/14/2015 5/21/2015 5/28/2015 6/9/2015 6/18/2015 6/25/2015 Elapsed time (days)   65 72 79 86 93 105 114 121   port height (cm)         Headspace composition [atm] P(tot)   1.019 1.038 1.051 1.059 1.071 1.078 1.081 1.078 N₂  0.804 0.813 0.815 0.813 0.814 0.815 0.813 0.812 O₂   0.206 0.212 0.213 0.212 0.214 0.213 0.215 0.212 Ar  0.008 0.010 0.011 0.011 0.012 0.012 0.012 0.011 CO₂   0.001 0.002 0.009 0.013 0.016 0.017 0.016 0.017 CH₄   0.000 0.000 0.002 0.009 0.015 0.021 0.025 0.025 Dissolved VOCs [mg/L] TCE 6.5 1129.7 1105.0 1143.0 1136.0 1101.7 1087.3 1104.7 1102.7 13 19.3 21.7 24.0 26.0 25.3 30.3 30.0 31.0 20 8.0 9.7 15.7 15.0 14.3 15.3 27.7 33.3 26.5 3.7 8.7 10.3 13.0 13.3 11.7 13.7 11.7 33 0.0 5.8 6.2 10.7 11.0 11.3 5.7 14.3 40 0.0 0.0 0.0 7.0 9.7 9.7 10.7 11.7 c-DCE 6.5 0.0 4.5 9.0 8.3 11.3 13.3 13.7 10.0 13 0.0 0.0 0.0 0.0 6.3 10.0 13.3 12.0 20 0.0 0.0 0.0 0.0 0.0 6.3 5.0 6.3 26.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 40 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 t-DCE 6.5 0.0 0.0 0.0 0.0 4.7 6.0 0.0 0.0 13 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 20 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 26.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 33 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 40 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 VC 6.5 0.0 12.0 13.7 16.7 18.7 21.3 22.0 24.7 13 0.0 0.0 0.0 0.0 0.0 14.3 18.7 17.3 20 0.0 0.0 0.0 0.0 0.0 15.7 15.0 20.0 26.5 0.0 0.0 0.0 0.0 0.0 0.0 7.3 15.3 33 0.0 0.0 0.0 0.0 0.0 0.0 0.0 11.7 40 0.0 0.0 0.0 0.0 0.0 0.0 0.0 5.3 Headspace VOCs [ppm] TCE   0.0 0.0 90.7 191.3 418.7 467.0 532.3 543.3 c-DCE  0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 t-DCE   0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 VC   0.0 0.0 0.0 0.0 0.0 44.3 320.7 1485.3     128 Date     7/2/2015 7/9/2015 7/16/2015 8/5/2015 8/18/2015 Elapsed time (days)   128 135 142 162 175 Gas generated (mL)     189.06 191.81 193.56 193.90 195.56 Pressure (atm)   1.122 1.124 1.124 1.124 1.125 Headspace V (L)     1.51 1.52 1.52 1.53 1.54   port height (cm)      Dissolved gases [atm] P(tot) 6.5 0.985   0.997 1.003 0.988 13 1.013 1.036 0.999 1.016 1.001 20 1.017   0.984 1.106 1.000 26.5   1.012 0.993 0.982 0.985 33 1.003 1.004 0.997 0.925 0.987 40 1.054 1.047 0.990   0.999 N₂ 6.5 0.154  0.139 0.148 0.135 13 0.206 0.211 0.191 0.204 0.189 20 0.256  0.268 0.233 0.258 26.5  0.277 0.271 0.267 0.264 33 0.351 0.348 0.318 0.299 0.309 40 0.397 0.402 0.405  0.397 O₂ 6.5 0.000   0.000 0.000 0.000 13 0.000 0.000 0.000 0.000 0.000 20 0.000   0.000 0.000 0.000 26.5   0.000 0.000 0.000 0.000 33 0.000 0.000 0.000 0.000 0.000 40 0.000 0.000 0.000   0.000 Ar 6.5 0.000  0.000 0.000 0.000 13 0.000 0.000 0.000 0.000 0.000 20 0.000  0.000 0.000 0.000 26.5  0.000 0.000 0.000 0.000 33 0.000 0.000 0.000 0.000 0.000 40 0.000 0.000 0.001  0.001 CO₂ 6.5 0.305   0.319 0.308 0.303 13 0.289 0.297 0.294 0.289 0.273 20 0.254   0.243 0.355 0.239 26.5   0.204 0.193 0.203 0.183 33 0.108 0.118 0.119 0.118 0.148 40 0.105 0.107 0.100   0.082 CH₄ 6.5 0.526  0.538 0.547 0.550 13 0.518 0.528 0.514 0.523 0.539 20 0.507  0.473 0.518 0.503 26.5  0.531 0.529 0.512 0.539 33 0.544 0.538 0.559 0.508 0.529 40 0.552 0.538 0.484   0.519  129 Date     7/2/2015 7/9/2015 7/16/2015 8/5/2015 8/18/2015 Elapsed time (days)   128 135 142 162 175   port height (cm)      Headspace composition [atm] P(tot)   1.089 1.080 1.084 1.099 1.084 N₂  0.818 0.809 0.814 0.815 0.813 O₂   0.219 0.214 0.213 0.219 0.213 Ar  0.012 0.011 0.011 0.014 0.011 CO₂   0.013 0.016 0.019 0.020 0.019 CH₄   0.027 0.030 0.027 0.031 0.027 Dissolved VOCs [mg/L] TCE 6.5 1145.3 1121.3 1125.7 1054.7 1125.7 13 32.3 31.3 32.3 27.7 36.3 20 14.7 17.3 16.3 16.7 19.0 26.5 14.0 13.7 15.0 13.3 14.0 33 13.3 13.0 12.3 11.3 13.0 40 10.0 13.3 10.3 13.0 12.7 c-DCE 6.5 11.3 8.3 6.7 6.3 5.7 13 10.3 7.7 8.3 0.0 0.0 20 2.7 0.0 1.0 0.0 0.0 26.5 0.0 0.0 0.0 0.0 0.0 33 0.0 0.0 0.0 0.0 0.0 40 0.0 0.0 0.0 0.0 0.0 t-DCE 6.5 0.0 0.0 0.0 0.0 0.0 13 0.0 0.0 0.0 0.0 0.0 20 0.0 0.0 0.0 0.0 0.0 26.5 0.0 0.0 0.0 0.0 0.0 33 0.0 0.0 0.0 0.0 0.0 40 0.0 0.0 0.0 0.0 0.0 VC 6.5 18.3 22.7 24.7 21.7 23.3 13 20.7 18.3 16.3 15.3 15.7 20 14.7 14.0 13.7 10.3 12.0 26.5 11.7 10.7 7.3 5.7 6.0 33 6.7 4.7 5.3 5.0 3.7 40 8.7 2.7 2.3 3.7 3.3 Headspace VOCs [ppm] TCE   572.7 566.7 564.7 568.3 574.7 c-DCE  0.0 0.0 0.0 0.0 0.0 t-DCE   0.0 0.0 0.0 0.0 0.0 VC   2240.3 1091.7 992.0 1365.7 1382.3   

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