Earth and Environmental Sciences

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The Tracing of a Contaminant (Tritium) from Candu Sources: Lake Ontario
(University of Waterloo, 1997) King, Karen June
In any research program we begin with a hypothesis and when our expected results do not concur with the observed results we must try and understand the dynamics behind the changed process. In this study we were trying to understand the flux between regional groundwater systems, surface waters and sedimentation processes in order to predict the fate of contaminants entering one of the larger bodies of water in the world- Lake Ontario. This lake has increased levels of tritium due to anthropogenic inputs. Our first approach to the problem was to look at tritium fluxes within the system . Hydrological balances were constructed and a series of sediment cores were taken longitudinally and laterally across the lake. The second approach was to quantify the sediment accumulation rate (SAR) within the depositional basins and zones of erosion in order to improve the linkage between erosion control (sedimentation) and the water quality program. In the last chapter the movement of tritium, by molecular diffusion, through the clayey-silts of Lake Ontario is quantified in terms of an effective diffusion coefficient. In these sediments effective diffusion equals molecular diffusion. In a laboratory experiment four cores of lake sediment were spiked with tritium . The resulting concentration gradient changes in the sediment porewaters after six weeks could be modeled by an analytical one- dimensional diffusive transport equation. Results calculated the average lab diffusion coefficient to be 2. 7 x 10 - 5cm 2. sec -1 which is twice that determined by Wang et al, 1952 but still reasonable. Short cores (50 cm) from lake Ontario had observed tritium concentrations with depth that reflected a variable diffusive profile. The increases and decreases in tritium with depth could be correlated between cores. Monthly tritium emission data was obtained and correlations between peaks in the tritium profile and emissions were observed. Monthly variations in release emissions corresponded to approximately a one centimeter slice of core. An average calculated diffusion coefficient of theses cores was 1. 0 x 10 -5 cm 2. sec -1 which compares to Wang's coefficient of 1. 39 x 10 -5 cm 2. sec -1. This implies that tritium is moving through the sediment column at a rate equal to diffusion. The results were obtained for smoothed values. It was not possible to model the perturbations of the data with a one dimensional model. The dynamics of the system imply that tritium could be used as a biomonitor for reactor emissions, mixing time and current direction scenarios and that a better understanding of this process could be gained by future coring studies and a new hypothesis.
Physical Hydrogeology and Impact of Urbanization at the Waterloo West Side: A Groundwater Modelling Approach
(University of Waterloo, 2000) Radcliffe, Anthony
In the last few decades protection of the environment has moved to the forefront of earth science research. Sustainable development is becoming more important to rapidly growing communities throughout southern Ontario including the City of Waterloo which has adopted an ecosystem planning approach toward future urban expansion. The City of Waterloo is located in the Regional Municipality of Waterloo which relies mainly on local groundwater resources for its drinking water supply. The Waterloo West Side is a collective name for several new developments occurring at the western limit of the City of Waterloo. Development of the Waterloo West Side is encroaching on a potential regional groundwater recharge area. Recent studies have recommended that some of these developments will require artificial infiltration facilities to augment the reduction in infiltration rates at the post-development stage. For this study, the pre-development groundwater flow system was characterized using a three-dimensional finite element model (WATFLOW). The regional Waterloo Moraine Model (approximately 750 km2) was refined in the study area (approximately 25 km2) so as to include the regional-scale influence on the local-scale groundwater flow. In addition, to approximate the complex groundwater flow system, within the study area, modifications were made to the current conceptual model. Several existing techniques were utilized in the numerical approach including three-dimensional parameterization and automated calibration methods. Simulations were completed to steady-state therefore results are averaged on a yearly basis. The potential impact of urbanization on the groundwater flow system was investigated by modifying the surficial boundary condition to simulate post-development infiltration rates (increased runoff) in areas where development will occur. The impact to local surface water was investigated for each post-development scenario. In addition, the effect on the regional and local groundwater flow systems were compared for each scenario.
Numerical Simulation of Hydrocarbon Fuel Dissolution and Biodegradation in Groundwater
(University of Waterloo, 2000) Molson, John W. H.
The behaviour of hydrocarbon fuels in contaminated groundwater systems is studied using a multicomponent reactive transport model. The simulated processes include residual NAPL dissolution, aerobic and anaerobic biodegradation with daughter-product transport, and transport of a reactive carrier with mixed equilibrium/kinetic sorption. The solution algorithm is based on a three-dimensional Galerkin finite element scheme with deformable brick elements and capacity for a free watertable search. Nonlinearities are handled through Picard iteration. Convergence is rapid for most applications and mass balance errors for all phases are minimal. The model is first applied to simulate a pilot scale diesel fuel dissolution experiment in which humic acid is used as a natural organic carrier to enhance dissolution and to promote biodegradation of the aqueous components. The pilot scale experiment is described by Lesage et al. (1995) and Van Stempvoort et al. (2000). The conceptual model includes 8 unique components dissolving from 500 mL of residual diesel fuel within a 3D saturated domain. Oxygen-limiting competitive aerobic biodegradation with a dynamic microbial population is also included. A mixed 2-site equilibrium/kinetic model for describing sorption of the carrier to the aquifer solids was adopted to reproduce the observed breakthrough of the humic acid and organic components. Most model parameters were obtained independently with minimal calibration. Batch sorption data were found to fit well at the pilot scale, however biodegradation and dissolution rates were not well known and had to be fitted. Simulations confirmed the observed 10-fold increase in effective solubility of trimethylnaphthalene, and increases on the order of 2-5 for methyl- and dimethylnaphthalene. The simulated plumes showed almost complete attenuation after 5 years, in excellent agreement with observed data. A sensitivity analysis showed the importance of carrier concentrations, binding coefficients, dissolution and biodegradation rates. Compared to a dissolution scenario assuming no carrier, the humic acid-enhanced dissolution case decreased the remediation time by a factor of about 5. The second application of the model involves simulating the effect of ethanol on the persistence of benzene in gasoline-impacted groundwater systems. The conceptual model includes a 4-component residual gasoline source which is dissolving at the watertable into a 3D aquifer. Comparisons are made between dissolved plumes from a gasoline spill and those from an otherwise equivalent gasohol spill. Simulations have shown that under some conditions, a 10% ethanol component in gasoline can extend the travel distance of a benzene plume by at least 150% relative to that from an equivalent ethanol-free gasoline spill. The increase is due to preferred consumption of oxygen by ethanol and a corresponding reduction in the biodegradation rate of benzene while the two plumes overlap. Because of differences in retardation however, the ethanol and benzene plumes gradually separate. The impact therefore becomes limited because oxygen rapidly disperses behind the ethanol plume and benzene degradation eventually resumes. A sensitivity analysis for two common spill scenarios showed that background oxygen concentrations, and benzene retardation had the most significant influence on benzene persistence. A continuous gasohol spill over 10 years was found to increase the benzene travel distance by over 120% and a pure ethanol spill into an existing gasoline plume increased benzene travel distance by 150% after 40 years. The results are highly relevant in light of the forthcoming ban of MTBE in California and its likely replacement by ethanol by the end of 2002.
Methodologies for capture zone delineation for the Waterloo Moraine well fields
(University of Waterloo, 2000) Muhammad, Dawood
The Region of Waterloo relies mainly (75 %) on local groundwater resources for its drinking water supply. The water demand is increasing with the growth of the population and there is a need to enhance the present water supplies. The Regional Municipality of Waterloo (RMOW), which is the governing body in charge of providing the drinking water supply, is conducting an extensive program to protect the groundwater resources of the Waterloo Moraine aquifer. The focus of that work is defining the wellhead protection areas of the existing production wells as well as the investigation of potential further water supply. The main goal of the work presented here is to delineate the capture zones for the major well fields of the Region. To achieve that goal, the flow for the expected pumping conditions is simulated using a fully 3D finite element model (WATFLOW) which has been proven to be highly flexible to represent the natural boundaries and the highly irregular stratigraphy by previous researchers and scholars. The modified version of this model which includes a pseudo-unsaturated module is used for the solution of flow equation. For the delineation of capture zones, a new particle tracking code (WATRAC) as well as two advective-dispersive transport models are used by using a probabilistic approach presented by Neupauer and Wilson [1999]. For the probabilistic approach (Wilson's method), two transport models, a conventional time-marching code (WTC) and a time-continuous code (LTG) are usedand their results are compared. The LTG is computationally more efficient than the WTC, but it gives oscillatory results close to the steady state condition. A combined used of LTG and WTC istherefore recommended to obtain the steady state capture zones. The 0. 25 probability contour agrees very well with the particle tracks, except for somewhat greater transverse spreading due tothe dispersion which is not considered by the particle tracking algorithm. Both methods, backward particle tracking and probabilistic advective-dispersive modelling are clearly more informative and give better insight when considered together than each by itself.
Pulse Flow Enhancement in Two-Phase Media
(University of Waterloo, 2001) Zschuppe, Robert
This laboratory project has been done to evaluate pressure pulsing as an Enhanced Oil Recovery (EOR) technique. To perform the study, a consistent laboratory methodology was developed, including the construction of a Consistent Pulsing Source (CPS). Tests compared pulsed and non-pulsed waterfloods in a paraffin or crude oil saturated medium, which also contained connate water (an irreducible water saturation). Results revealed that pulsed tests had maximum flow rates 2. 5--3 times higher, greater oil recovery rates, and final sweep efficiencies that were more than 10% greater than non-pulsed tests. The CPS design has proven very successful, and has since been copied by a major oil corporation. However, there are two limitations, both caused by fluctuating water reservoir levels. Longer pulsed tests (reservoir-depletion tests) were periodically paused to refill the water reservoir, resulting in reservoir depressurization and lower flow rates. The final effect of this was impossible to quantify without correcting the problem. The second CPS limitation was the change in pulse shape with time. However, it is not expected that this had any major effect on the results. The pulse pressure and period studies were limited by early tests, which did not have the necessary time duration. Both increasing pulse pressure and decreasing pulse period were found to increase the final sweep efficiency. Slightly decreasing porosity (0. 4% lower) was found to lower sweep efficiencies. However, the 34. 9% porosity results were not done until reservoir depletion, so it is difficult to quantitatively compare results. An emulsion appeared after water breakthrough when using the CPS on light oils (mineral oil). This may have been the result of isolated oil ganglia being torn apart by the sharp pulses. Although it is difficult to apply laboratory results to the field, this study indicates that pressure pulsing as an EOR technique would be beneficial. Doubled or tripled oil recovery rates and 10% more oil recovery than waterflooding would be significant numbers in a field operation. A valuable application would be in pulsing excitation wells to both pressurize the reservoir and enhance the conformance of the displacing fluid over a long-term period. It would also be valuable for short-term chemical injections, where mixing with the largest volume possible is desirable.
Numerical Simulation of Road Salt Impact at the Greenbrook Well Field, Kitchener, Ontario
(University of Waterloo, 2002) Bester, Michelle
Chloride concentrations at the Greenbrook well field in Kitchener, Ontario, have been steadily increasing over the past several decades and may soon pose a threat to drinking water quality. Drinking water limits at some wells have already been exceeded. The Regional Municipality of Waterloo (RMOW) relies mainly on local groundwater resources for its drinking water supply, and the Greenbrook well field is the oldest of 50 municipal well fields contributing to this supply. Urban growth and the expansion of city limits over the years has surrounded the well field, placing it in a high risk area in need of protection. As such, protection of this water supply is essential until alternative sources can be found. Road salt has been identified as the prime source of the chloride contamination, and various management alternatives and remediation strategies are currently being studied. In order to characterize the behaviour of chloride in the subsurface, an understanding of the mechanisms that control travel of chloride to the water table and through the groundwater system is needed. For the first phase of this work, a 2-D variably-saturated flow and transport model (SWMS-2D) was used to evaluate the effect of seasonal fluctuation in chloride loading to a generic aquifer system. Chloride was applied over the surface of the model in seasonal pulses that correlated with temperature and precipitation. The model showed a dampening of the seasonal response with depth that lead to the conclusion that long-term transport models can neglect seasonal changes in solute loading. For the second phase of this work, a proven 3D finite element transport model (Waterloo Transport Code: WTC) was used to simulate road salt impacts to the well field. Road salt was applied over selected roads throughout the steady-state capture zone via a type 3 (Cauchy) boundary that varies both temporally and spatially with road type and location. After calibrating the model from 1945 to 2002 to chloride concentrations using the weighted average of 5 Greenbrook production wells, the model was run to the year 2041 to assess future implications. Remediation strategies were also investigated via 6 predictive scenarios in which chloride applications were reduced by varying degrees. The results of this phase will be used by the RMOW in cost-benefit analyses of alternative de-icing approaches versus de-chlorination treatment of the well water.
A process-based stable isotope approach to carbon cycling in recently flooded upland boreal forest reservoirs
(University of Waterloo, 2002) Venkiteswaran, Jason James
Reservoirs impound and store large volumes of water and flood land. The water is used for electricity generation, irrigation, industrial and municipal consumption, flood control and to improve navigation. The decomposition of flooded soil and vegetation creates greenhouse gases and thus reservoirs are a source of greenhouse gases. Reservoirs are not well studied for greenhouse gas flux from the water to the atmosphere. The FLooded Upland Dynamics EXperiment (FLUDEX) involves the creation of three experimental reservoirs in the upland boreal forest to study greenhouse gas and mercury dynamics. The balance of biological processes, decomposition, primary production, CH₄ oxidation and the nitrogen cycle in the reservoirs controls the greenhouse gas flux from the reservoir to the atmosphere. Understanding the importance and controlling factors of these processes is vital to understanding the sources and sinks of greenhouse gases within reservoirs. The carbon and oxygen dynamics near the sediment-water interface are very important to the entire reservoir because many processes occur in this area. Light and dark benthic chambers were deployed, side-by-side, to determine the benthic flux of DIC and CH₄ across the sediment-water interface and to determine the role of benthic photoautotrophs in benthic DIC, CH₄ and O₂ cycling. Benthic chambers have shown photoautotrophs use the decomposing soil, rocks and exposed bedrock as a physical substrate to colonize and the CO₂ produced by the decomposing soil as a carbon source since the delta¹³C-DIC value of the DIC added to light chambers is enriched relative to dark chambers and net photosynthesis rates are linked to community respiration. Benthic photoautotrophs consume 15-33% of the potential DIC flux into the water column. CH₄ produced by the decomposition of soils is partially oxidized by methanotrophs that use the photosynthetically produced oxygen. The delta¹³C-CH₄ values of the CH₄ added to light chambers is enriched relative to dark chambers and 15-88% of the potential CH₄ flux into the water column is oxidized. An isotope-mass budget for DIC and CH₄ is presented for each reservoir to identify the importance of processes on areservoir scale. Input of DIC to the reservoirs from overland flow can be important because concentration is greater and delta¹³C-DIC values are depleted relative to inflow from Roddy Lake. Estimates of total reservoir primary production indicate that 3-19% of the total DIC production from decomposition is removed by photoautotrophs. The carbon cycling in biofilm and the importance of periphytic primary production needs to be better understood. Dissolved delta¹³C-CH₄ values of CH₄ in reservoir outflow enriched 45-60permil, indicating that CH₄ oxidation was an important CH₄ sink within the reservoirs. Stable carbon isotope data indicates that the CH₄ in the bubbles is partially oxidized so the site of bubble formation is the upper portion of the flooded soil. The fraction of CH₄ converted to CO₂ in the FLUDEX reservoirs is similar to that of the wetland flooded for the Experimental Lakes Area Reservoir Project (ELARP). Approximately half of the dissolved CH₄ in the FLUDEX reservoirs was removedby CH₄ oxidation. The ebullitive flux of CH₄ from FLUDEX reservoirs is reduced 25-75% by CH₄ oxidation. The CH₄ flux to the atmosphere from peat surface of the ELARP reservoir became less oxidized after flooding: 91% to 85% oxidized. The floating peat islands of the ELARP reservoir were less oxidized than the peat surface. Similar to the CH₄ in the FLUDEX reservoirs, CH₄ in the ELARP peat islands was oxidized 56%. CH₄ oxidation is an important process because it reduces the global warming potential of the greenhouse gas flux since CO₂ is less radiatively active than CH₄.
Stable Isotopes of Sulphur and Oxygen in Forested Catchments: Insight from New Techniques into Sulphur Cycling and Dissolved Organic Matter Alteration
(University of Waterloo, 2003) Humphries, Stefan
Dissolved organic matter (DOM) is present in all forested catchments and can be important in binding metals, absorbing UV, and the transport of nutrients (C, N, S, P). DOM is extremely heterogeneous in time and space, making it difficult to characterize. New techniques have been developed to determine δ34S and δ18O in DOM. These techniques have been applied to samples from Harp and Plastic Lake catchments (45º23'N, 79º 08'W, 45º11'N, 78º 50'W) in order to obtain information about sources and sinks of DOM within forested catchments on the Canadian Shield. In conjunction with sulphate and DOC concentrations, this new data provides valuable insight into sulphur cycling and DOM alteration within these catchments. Data generated for δ34S-DOM and δ18O-DOM appears to be the first data reported in the literature for DOM. The inorganic (δ34S-SO42-) and organic S (δ34S-DOM) differs by environment in both catchments. The range of δ34S-SO42- is between 3. 3‰ and 10. 3‰, and the range of δ34S-DOM is from 3. 4‰ to 8. 7‰. Sulphate in the Harp Lake catchment in most samples is subject to some sort of cycling within the watershed, since δ34S-SO42- differs from precipitation. In the Harp Lake catchment, upland δ34S-SO42- is influenced by historical precipitation. The δ34S-DOM is derived from leaching and microbial activity of DOM from organic horizons in the soil. The δ34S-SO42- and δ34S-DOM of wetland streams is extremely variable, controlled by hydrology. The δ34S-SO42- provides information on oxidation-reduction dynamics in the wetland, and δ34S-DOM provides information about sources of DOS in the wetland. The δ34S-SO42- and δ34S-DOM are possibly related in Harp Lake. Mineralization of DOS as evidenced by δ34S-DOM and DOS concentrations could be a small input of SO42- into Harp Lake. It is possible δ18O-DOM could be an indicator of DOM alteration. The range of δ18O-DOM is between 8. 2‰ and 14. 4‰. The δ18O-DOM in the Harp Lake catchment is highly correlated with relative molecular weight, which has been shown to decrease with increasing alteration. Wetland streams show the largest range in δ18O-DOM, while uplands, groundwater, and Harp Lake are the least varied. The highest δ18O-DOM values are from sources of DOM such as leaf leachates (representative of forest floor litter) and wetlands. The most depleted samples are from groundwater and Harp Lake which typically contain highly altered DOM. The δ34S-DOM and δ18O-DOM can provide valuable information on sources of DOM and DOM alteration within the catchment. The δ18O-DOM could also allow the separation of autochthonous and allochthonous DOM in lakes.
Greenhouse gas flux and budget from an experimentally flooded wetland using stable isotopes and geochemistry
(University of Waterloo, 2003) Saquet, Michelle
A boreal forest wetland (L979) was flooded in 1993 at the Experimental Lakes Area, Ontario to imitate a hydroelectric reservoir and to study the effects of flooding on greenhouse gas production and emission. Flooding initially caused CO₂ and CH4 emission rates to increase and changed the wetland from a small, natural carbon sink to a large source of carbon. The increased production of greenhouse gases in the peatland also caused the majority of the peat to float to the surface creating floating peat islands, within 4 years of flooding. The floating peat islands are a larger source than the central pond of CH4 to the atmosphere due to the high water table and small oxidation zone as compared to the earlier undisturbed peatland. The floating peat islands had an average flux of 202 ± 66 mg C-CH4/m²/day comparable to rates measured in 1995. Methane flux rates are spatially and temporally variable ranging from ?117 to 3430 mg C-CH4/m²/day. The variability is partly due to episodic releases of gas bubbles and changes in overlying pressure from the water table. The development of floating peat islands created an underlying water pocket. The water pocket increased water movement between the central pond and the peatland and led to increased peat temperatures and methane oxidation, and removal of debris from the water pocket. DIC, CH4, and O₂ concentrations, and δ13C-DIC, δ13-CH4, and δ18O-O₂ values in the water pocket were similar to values in the central pond. Before flooding, the δ13C-CH4 values from the peatland ranged between ?36 and ?72? indicating that about 65 to 90% of the methane was oxidized before flooding. After flooding, the median δ13C-CH4 value from the floating peat islands was ?52? indicating that about 30% of the methane was oxidized before it was emitted to the atmosphere. Since the floating islands are now vegetated, photosynthesis and transport via plants allow the movement of oxygen into the peat islands Methane oxidation in the central pond was similar in 2001 and 2002. DIC and CH4 isotope mass budgets from June 3 to September 23, 2002 indicate that inputs were smaller than outputs at L979. Calculated net DIC and CH4 production in the central pond was 8490 and 432 kg C, with δ13C-DIC of -18. 5 ? and δ13C-CH4 of -32. 5?. Decomposition of peat was the source of DIC and CH4. O₂ saturation levels indicate that the pond is always undersaturated and that respiration dominates the system; however, the δ18O-O₂ also indicates that photosynthesis is an important process in the central pond of L979. The peat islands contributed about 90% of the total CH4 flux, whereas the open water areas contributed 10%. This indicates that formation of peat islands in a hydroelectric area can significantly affect the greenhouse gas emissions to the atmosphere. The average flux of CH4 from the entire wetland in 2002 was 202 ± 77 mg C-CH4/m²/day, equivalent to 44 ± 17 g C-CH4/m²/year (year = 220 days). This is higher than preflood values of 0. 5 g C-CH4/m²/year in 1992, and the early post-flood value of 8. 9 g C-CH4/m²/year in 1993/1994. The wetland continues to emit methane after ten years of flooding at higher than preflood rates.
Intermediate and Low Level Nuclear Waste Stabilisation: Carbonation of Cement-based Wasteforms
(University of Waterloo, 2003) Andreou, Sean
Carbonation is a naturally-occurring process whereby Ca-containing cement phases lose their hydration water and are converted to carbonate minerals by reaction with atmospheric CO₂. As these secondary minerals develop in the microstructure of hydrated cement, porosity, pore-size distribution and permeability are decreased. These are all considered desirable properties in a wasteform. The objective of this study was to examine the effect of carbonation and different pozzolans on the leach performance and mechanical strength of ordinary Portland cement (OPC) wasteforms. Two methods of accelerated cement carbonation were used:

A vacuum carbonation method, where wasteforms are placed in an evacuated, sealed cell and subjected to small additions of CO₂ over several days at near vacuum conditions; and
A one-step carbonation method, where CO₂ gas is added to the wasteform paste as it is being mixed.
Thirteen elemental constituents of interest to the safety assessments of long-term management of Ontario Power Generation's radioactive waste (Cl, N, S, Se, 13C, Th, Pb, Co, Ni, Cu, Sr, Ba and Cs) were stabilised/solidified via cement mix water. Wasteforms were produced with only OPC, OPC and fly ash, or OPC and silica fume. Most wasteforms were carbonated using one of the carbonation methods. Some wasteforms were not carbonated and served as controls. Wasteforms were subjected to either standard leach tests or compressive strength tests. The extent of carbonation was found to be about 20% for vacuum carbonation method, substantially higher than that for one-step treatment (up to about 10%). For vacuum carbonated wasteforms, carbonation occurred at the outer selvages of the wasteforms, whereas one-step treatment resulted in homogenous carbonation. Generally, compared to uncarbonated OPC wasteforms, vacuum carbonation increased leaching of elements that are anionic in cementitious conditions (Cl, N, S, Se, 13C, Th), decreased leaching of large metal cations (Sr, Ba, Cs, Pb) and had negligible effect on the leaching of the elements that form hydroxyl complexes (Co, Ni, Cu). 13C was the only anionic element whose leachability was reduced by vacuum carbonation, as it may be precipitated in the form CO32- in the large quantity of secondary carbonate minerals produced during the vacuum carbonation process. One-step carbonation did not result in substantial reductions in leachability, compared to uncarbonated OPC wasteforms. However, it had an interesting inverse effect on large metal cation leachability from fly ash- and silica fume-containing wasteforms. A model is presented that proposes that porewater pH changes can have an effect on waste element leachability because 1) the C-S-H Ca/Si ratio is dependent on the equilibrating porewater pH and 2) the degree of ion sorption on C-S-H is dependent on the C-S-H Ca/Si ratio. This model should be tested experimentally as it has important implications on wasteform design. Because of this inverse behaviour, overall neither pozzolan outperformed the other with respect to leachability. Generally, for uncarbonated wasteforms, OPC retained the elements more effectively than OPC with pozzolans. For pozzolans, the leachability of these elements from OPC with fly ash was lower than that of OPC with silica fume. Leaching of Cs was anomalously low from uncarbonated OPC wasteforms, but follow-up experimentation did not corroborate this anomaly. Further testing of these wasteforms to determine how the mineralogical fate of Cs can differ between wasteforms is recommended. All wasteforms tested were of acceptable strength (<0. 689 MPa). Fly ash, and, to a greater degree, silica fume, improved wasteform strength when compared to OPC wasteforms. Carbonation treatments had little effect on wasteform strength. This study has provided much information about the leaching characteristics of a representative set of waste elements from several cement-based wasteform treatments. Although it has not indicated a wasteform design that is ideal for all elements studied, it does suggest that some treatments may be effective for certain groups of elements. Most notably, vacuum carbonation shows promise in improving the immobilisation of isotopes of large metal cations such as Sr, Ba, Cs and Pb as well as 14C (as suggested by 13C here) in cement-based wasteforms.
In situ Chemical Oxidation of Creosote/Coal Tar Residuals: Experimental and Numerical Investigation
(University of Waterloo, 2004) Forsey, Steven
Coal tar, coal tar creosote and oily wastes are often present as subsurface contaminants that may migrate below the water table, leaving a widely distributed residual source of contaminants leaching to the ground water. In situ chemical oxidation is a potentially viable technology for the remediation of aquifers contaminated with creosote and coal tars. The oxidant of choice would be flushed through the contaminated area to oxidize aqueous contaminants and enhance the mass transfer of contaminants from the oil phase. A series of batch and column experiments were performed to assess the ability of a chemical oxidizing reagent to oxidize creosote compounds and to increase mass transfer rates. Results from the column experiments were then simulated using a reactive transport model that considered 12 different creosote compounds undergoing dissolution, oxidation and advective-dispersive transport. Three strong chemical oxidizing reagents, Fenton's Reagent, potassium persulfate with ferrous ions, and potassium permanganate were tested with batch experiments to determine their reactivity towards creosote compounds. All three reagents successfully decomposed aqueous creosote compounds and were able to reduce the mass of the monitored creosote compounds within the oil phase. However, both the Fenton's and persulfate reagents required large molar ratios of iron and peroxide because the precipitation of iron continually removed the iron catalyst from the aqueous phase. Fenton's and persulfate reagents could be used in systems that are allowed to become acidic to solubilize the iron, but the cost of adjusting the pH, potential impact on aquifer geochemistry and the short lived free radical reaction make these reagents less practical than KMnO4. KMnO4 oxidizes a wide variety of creosote compound, can be used at very high concentrations, and its concentration will not be reduced significantly as it moves through the zone of contamination. The feasibility of using potassium permanganate as an oxidizing reagent for in situ treatment of creosote residuals was investigated using batch column experiments. Column experiments were conducted at a neutral pH in a carbonate rich sand matrix with creosote at 8 % saturation. The columns were treated intermittently with simulated ground water or KMnO4 dissolved in simulated ground water (8 g/L) for 172 days. Under these experimental conditions the KMnO4 decreased the initial mass of the monitored creosote compounds by 36. 5%, whereas in the control column (no oxidizer) only 3. 9% was removed. To remove all of the monitored creosote compounds from the columns it was calculated that the volume needed would be 40 times less for the KMnO4 solution, compared to flushing alone with simulated ground water. To evaluate the potential effectiveness of in situ chemical oxidation at field sites, numerical model simulations need to incorporate relevant chemical oxidation rates to assess system performance and to provide design guidance. In-depth kinetic studies were performed to determine rate constants and to gain insight into the oxidation of creosote compounds with KMnO4. The study examined the kinetics of the oxidative treatment of a selected group of creosote/coal tar compounds in water using excess potassium permanganate and investigated the correlation between reactivity and physical/chemical properties of the organic pollutants. The oxidation of naphthalene, phenanthrene, chrysene, pyrene, 1-methylnapthalene, 2-methylnaphthalene, acenaphthene, fluorene, carbazole, isopropylbenzene, ethylbenzene and methylbenzene closely followed first-order reaction kinetics, enabling calculation of second-order rate constants. Fluoranthene was only partially oxidized by permanganate and the oxidation of anthracene was too fast to be measured. Biphenyl, dibenzofuran, benzene and tert-butylbenzene failed to react in this study. Comprehensive column experiments complemented by numerical modeling revealed an unequal enhancement of the removal of creosote compounds from the oil phase. For the more readily oxidizable compounds such as pyrene and naphthalene, a significant increase in the mass transfer rates was observed in the oxidation columns, compared to the oxidant free column. For non-oxidizable compounds such as biphenyl and dibenzofuran, an increase in the rate of mass removal was also observed in the oxidation columns, even though their aqueous concentrations were not reduced in the column. This was due to the rapid removal of the more readily oxidizable compounds from the oil, which increases the mole fraction of the non-oxidizable compounds. Thus according to Raoult's Law, the concentration in the aqueous phase becomes closer to its pure phase liquid solubility and its aqueous concentration increases. The most significant result of the experiments is the observed increase in the rate of removal of those compounds that have low aqueous solubilities and are readily oxidized, such as pyrene and fluorene. Compounds that have low aqueous solubilities and are not readily oxidizable, such as chrysene, may still take a long period of time to be removed, but the removal time is greatly reduced with oxidation compared to flushing the area with water alone.
Modeling a controlled-sourced, multichemical plume undergoing natural attenuation
(University of Waterloo, 2004) Martin, Caitlin
Sampling of an emplaced creosote source installed below the water table at CFB Borden was conducted over a period of ten years, with over nine thousand samples taken from approximately 250 multilevel samplers. This extensive dataset was used in several attempts to model the multi-chemical plumes emanating from this emplaced source, and to further understand the chemical and biological processes affecting these plumes and their natural attenuation. An aerobic microcosm study of naphthalene, 1-methylnaphthalene and acenaphthene was conducted in order to determine the possibility of interactions between these three chemicals. All three chemicals degraded within the eight days of the study, and the degradation of naphthalene and 1-methylnaphthalene was not affected by the presence of any of the three chemicals studied. Acenaphthene degraded more quickly when naphthalene was present in the microcosm. The programs Visual MODFLOW and RT3D were used to model the transport and degradation of naphthalene at CFB Borden. Both a first order rate reaction module and a multiple electron acceptor reaction module were used, and contaminant mass was introduced to the model through a fence of observed concentrations. Good results were found at early time with the multiple electron acceptor reaction package, however at late time the model did not match to observations. The program BIONAPL/3D was used in a similar attempt to model the transport and degradation of naphthalene. Naphthalene mass was introduced to the model through a fence of observed concentrations, and multiple electron acceptors were used to degrade this chemical. Results were good at early time, but at late time the model did not match observations. BIONAPL was then used to simulate the dissolution of the original source NAPL. Several chemicals of interest were examined: naphthalene, m-xylene, 1-methylnaphthalene and acenaphthene. Naphthalene and m-xylene dissolved from the source at rates similar to observations, however the dissolution of 1-methylnaphthalene and acenaphthene was not as well modeled. As with the Visual MODFLOW model, the BIONAPL model which best matched observations generally worked well at early times, but did not at late times. The models were not able to successfully simulate many processes that occur in the field, such as chemical and biological interactions and NAPL source dissolution. Mismatches between the models and observations are likely due to these reasons. It may be that we do not fully understand these processes, so we are unable to model them.
Fate and Transport of Naphthenic Acids in Glacial Aquifers
(University of Waterloo, 2004) Gervais, Francoise
Naphthenic acids (NAs) are carboxylated alkanes and cycloalkanes concentrated in wastewater during oil sands processing. The general chemical formula is C{n}H{n+Z}O{2}, where n represents the number of carbon atoms and Z specifies a homologous family with 0-6 rings (Z=0 to Z=-12). The wastewater is acutely toxic to surface water organisms and is stored in tailings ponds with over 230 million m³ of fines tailings and free water. The purpose of this thesis was to provide a preliminary evaluation of the potential attenuation of NAs during groundwater flow from the ponds. Laboratory studies were conducted to evaluate possible attenuation mechanisms. Aerobes from aquifer material degraded 60% of the NAs over 20 weeks in laboratory microcosms. The greatest decrease occurred in the low molecular weight bicyclic homologues with 12 to 16 carbons. The microbial activity confirms that aerobic naphthenate-degrading bacteria occur naturally in the glacial aquifer near Suncor's Pond 2/3. These results support the hypothesis that limited aerobic biodegradation of the smaller components of NAs could occur relatively rapidly under field conditions. There was no measurable decrease in NA concentration over six months in anaerobic microcosms, although microbial activity did lead to sulfate-reducing and methanogenic conditions. The theoretical retardation in glacio-fluvial sands was calculated using soil-water partitioning coefficients (K{d}) determined by batch equilibration experiments using a mixture of naturally occurring naphthenic acids as well as the nine surrogates. The retardation (porosity of 0. 3, bulk density of 1. 5 g/mL) ranged from 1. 2 to 2. 6. However, no measurable sorption was seen at the field sites. Detailed characterization allows us to examine how the proportions of homologue, or groups of molecules with the same molecular weight and number of cycloalkane rings, vary. Aerobic biodegradation favoured removal of low molecular weight NAs. A 15% mass loss attributed to sorption caused no changes in the 3D signature. Thus, changes in NA "signature" in groundwater systems were then attributed to aerobic biodegradation. Three plumes were examined for evidence of attenuation of NAs via biodegradation. First, the individual samples were classified as background, possibly process-affected or process-affected using a combination of Piper diagrams, the stable isotopes oxygen-18 and deuterium, dissolved chloride and sodium, as well as the total naphthenic acids concentration. Second, in order to estimate attenuation due to dispersive dilution, a linear correlation line was drawn between various conservative tracers and the naphthenic acids concentration. This allowed the identification of certain samples as possibly having a lower concentration of NAs than could be expected from simple dispersive dilution. Third, the 3D signature of certain samples were examined for the presence of the aerobic biodegradation 3D signature. One site showed good evidence for aerobic biodegradation of naphthenic acids. A second site showed some evidence for biodegradation under methanogenic conditions but the evidence was not definitive. The evidence at the third site was contradictory and no conclusions could be drawn from it. This research suggests some attenuation of NAs by biodegradation may be possible during groundwater flow.
Nitrate sources and cycling at the Turkey Lakes Watershed: A stable isotope approach
(University of Waterloo, 2004) Spoelstra, John
          Stable isotopic analysis of nitrate (¹⁵N/¹⁴N and ¹⁸O/¹⁶O) was used to trace nitrate sources and cycling under undisturbed conditions and following harvest at the Turkey Lakes Watershed (TLW), located near Sault Ste. Marie, Ontario, Canada.
          Bulk precipitation collected biweekly at the TLW from 1995 to 2000 had nitrate isotope values that ranged from +42. 4 to +80. 4‰ for d¹⁸O and -6. 3 to +2. 8‰ for d¹⁵N. An incubation experiment indicated that the isotopic composition of atmospheric nitrate was not compromised by collection methods whereby unfiltered bulk precipitation samples remain in the collector for up to two weeks.
          The first direct measurement of the isotopic composition of microbial nitrate produced in situ was obtained by eliminating precipitation inputs to three forest floor lysimeters and subsequently watering the area with a nitrate-free solution. Microbial nitrate had d¹⁸O values that ranged from +3. 1 to +10. 1‰ with a mean value of +5. 2‰, only slightly higher than values predicted based on the d¹⁸O-H₂O of the watering solution used. d¹⁸O values of soil O₂ (+23. 2 to +24. 1‰) down to a depth of 55cm were not significantly different from atmospheric O₂ (+23. 5‰) and therefore respiratory enrichment of soil O₂ did not affect the d¹⁸O values of microbial nitrate produced at the TLW.
          Nitrate export from two undisturbed first-order stream basins was dominated by microbial nitrate, with the contribution of atmospheric nitrate peaking at about 30% during snowmelt. Clear-cutting of catchment 31 in 1997 resulted in elevated nitrate concentrations, reaching levels that exceeded the drinking water limit of 10 mg N/L. Isotopic analysis indicated that the source of this nitrate was predominantly chemolithoautotrophic nitrification. The d¹⁸O values of microbial nitrate in stream 31 progressively increased during the post-harvest period due to an increase in the proportion of nitrification that occurred in the summer months. Despite drastic alteration of nitrogen cycling in the catchment by the harvest, d¹⁵N-nitrate values in shallow groundwater did not change from the pre-harvest.    Denitrification and plant uptake of nitrate in a small forested swamp in catchment 31 attenuated 65 to 100% of surface water nitrate inputs following harvest, reducing catchment-scale nitrate export by 35 to 80%.
Reservoir screening criteria for deep slurry injection
(University of Waterloo, 2005) Nadeem, Muhammad
Deep slurry injection is a process of solid waste disposal that involves grinding the solid waste to a relatively fine-grained consistency, mixing the ground waste with water and/or other liquids to form slurry, and disposing of the slurry by pumping it down a well at a high enough pressure that fractures are created within the target formation. This thesis describes the site assessment criteria involved in selecting a suitable target reservoir for deep slurry injection. The main goals of this study are the follows:

Identify the geological parameters important for a prospective injection site

Recognize the role of each parameter

Determine the relationships among different parameters

Design and develop a model which can assemble all the parameters into a semi-quantitative evaluation process that could allow site ranking and elimination of sites that are not suitable

Evaluate the model against several real slurry injection cases and several prospective cases where slurry injection may take place in future

The quantitative and qualitative parameters that are recognized as important for making a decision regarding a target reservoir for deep slurry injection operations are permeability, porosity, depth, areal extent, thickness, mechanical strength, and compressibility of a reservoir; thickness and flow properties of the cap rock; geographical distance between an injection well and a waste source or collection centre; and, regional and detailed structural and tectonic setup of an area. Additional factors affecting the security level of a site include the details of the lithostratigraphic column overlying the target reservoir and the presence of overlying fracture blunting horizons. Each parameter is discussed in detail to determine its role in site assessment and also its relationship with other parameters. A geological assessment model is developed and is divided into two components; a decision tree and a numerical calculation system. The decision tree deals with the most critical parameters, those that render a site unsuitable or suitable, but of unspecified quality. The numerical calculation gives a score to a prospective injection site based on the rank numbers and weighting factors for the various parameters. The score for a particular site shows its favourability for the injection operation, and allows a direct comparison with other available sites. Three categories have been defined for this purpose, i. e. average, below average, and above average. A score range of 85 to 99 of 125 places a site in the ?average? category; a site will be unsuitable for injection if it belongs to the ?below average? category, i. e. if the total score is less than 85, and the best sites will generally have scores that are in the ?above average? category, with a score of 100 or higher. One may assume that for sites that fall in the ?average? category there will have to be more detailed tests and assessments. The geological assessment model is evaluated using original geological data from North America and Indonesia for sites that already have undergone deep slurry injection operations and also for some possible prospective sites. The results obtained from the model are satisfactory as they are in agreement with the empirical observations. Areas for future work consist of the writing of a computer program for the geological model, and further evaluation of the model using original data from more areas representing more diverse geology from around the world.
Hydrogeologic Analysis of a Complex Aquifer System and Impacts of Changes in Agricultural Practices on Nitrate Concentrations in a Municipal Well Field: Woodstock, Ontario
(University of Waterloo, 2005) Haslauer, Claus P.
The Thornton Well Field, located in an area of dominantly (~80%) agricultural land-use, produces ~50% of the drinking water for the city of Woodstock. Since the mid 1990?s nitrate concentrations in some of the supply wells are above the Maximum Allowable Concentration (MAC) of 10mg-N/L. The source of the nitrate is believed to be from agricultural fertilizing practices. As response to this problem, the County of Oxford purchased 111 hectares of farmland within the capture zone of the Thornton Well Field. This land is rented back to farmers with restrictions placed on the amount of nitrate fertilizer that can be applied in an attempt to sustainably reduce the nitrate concentrations in the ThorntonWell Field below MAC.

The objective of this thesis is to improve the site conceptual hydrogeologic model, both at a spatial scale suitable for numerical analysis through regional groundwater flow modelling (representative distance ~9km) and at a smaller scale (representative distance ~2km) for nitrate transport modelling in the vicinity of the Thornton Well Field and the purchased land. Field investigations aimed to support the site hydrogeologic model involved drilling, geologic logging, and instrumentation of a 72m deep borehole completed to bedrock in the center of the nitrate plume, at the border of the farmland under consideration. The shallow subsurface features encountered during this initial drilling operation were tracked below the farm fields with geophysical tools and additional drilling and core logging throughout the field site. Transient hydraulic head observations in combination with on-site precipitation measurements were used to indicate where a hydraulic connection between ground surface and deeper layers exists, which allow rapid infiltration to occur into a glaciofluvial outwash channel which was identified as one important pathway for nitrate transport to the Thornton Well Field. One receptor at the end of that pathway, the screen of the supply Well 01, was depth-discrete profiled for water inflow and nitrate concentrations to obtain better characteristics of the receptor.

A method was developed to estimate the nitrate mass stored in the unsaturated zone below Parcel B, permitting an estimation of the time frame required for flushing the nitrate out of this zone, and the anticipated effects on nitrate concentrations in the supply wells. The spatial distribution of nitrate concentrations in the unsaturated zone and in the aquifer units was analyzed. It was found that the nitrate concentration within the unsaturated zone below Parcel B is ~16mg-N/L, resulting in a total nitrogen mass of ~20t within that zone. It was shown that significant reductions (~10%) in nitrate concentrations in the supply wells of the Thornton Well Field can be achieved, assuming zero nitrate mass influx into the domain from Parcel B.

A comprehensive data base was developed to organize, manage, and analyze all site measured data for that purpose, and regional hydrogeologic data from the MOE Water Well Record Database. The contents of this database in conjunction with the MOE Water Well Record Database were used to construct a three-dimensional digital representation of the hydrostratigraphic units at a regional and at a local scale. This three-dimensional hydrostratigraphic unit spatial distribution along with surface watershed information and potentiometric surfaces of the various aquifer units will be used to define a suitable spatial domain and associated boundary conditions for future modelling efforts. This hydrostratigraphic model will serve as basis for predicting the effects of agricultural land-use changes within the capture zone of the Thornton Well Field (Parcel B) on the nitrate concentrations in the supply wells of the Thornton Well Field.
The Structural Geology, Kinematics and Timing of Deformation at the Superior craton margin, Gull Rapids, Manitoba
(University of Waterloo, 2005) Downey, Matthew
The Gull Rapids area, Manitoba, lies on the Superior craton margin and forms part of the Superior Boundary Zone (SBZ), a major collisional zone between the Archean Superior craton and the adjacent Paleoproterozoic Trans-Hudson Orogen. There are two main rock assemblages at Gull Rapids: orthogneisses (of possible Split Lake Block origin) and supracrustal rocks (metavolcanic and metasedimentary). Late, crosscutting felsic and mafic intrusive bodies (mostly dykes and sills) are used to constrain the relative and absolute timing of deformation and metamorphism.

The Gull Rapids area records a complex tectonic history. The area experienced four generations of Neoarchean ductile and brittle deformation (G1 ? G4) and one of Paleoproterozoic ductile-brittle deformation (G5). G1 deformation produced the main foliation in the map area, as well as local isoclinal folding which may be related to an early shearing event. M1a prograde mid-amphibolite facies metamorphism is contemporaneous with the early stages of G1. Widespread, tight to isoclinal sheath folding during G2 was recorded in the supracrustal assemblage, and is the result of southwest-side-up, dextral shearing during the early shearing event. A ca. 2. 68 Ga widespread phase of granitoid intrusion was emplaced late-G1 to early-G2, and is rich in metamorphic minerals that record conditions of M1b upper-amphibolite facies peak metamorphism. M1b metamorphism, late-G1 to early-G2 deformation, and intrusion of this felsic phase are contemporaneous. M2 retrograde metamorphism to mid-amphibolite facies was recorded sometime after M1b. G1 and G2 structures were re-folded during G3, which was then followed by G4 southwest-side-up, dextral and sinistral shearing, contemporaneous with late pegmatite intrusion at ca. 2. 61 Ga. This was followed by mafic dyke emplacement at ca. 2. 10 Ga, and then by G5 sinistral and dextral shearing and M3 greenschist facies metamorphism or hydrothermal alteration at ca. 1. 80 Ga.

Deformation and metamorphism at Gull Rapids post-dates emplacement and deposition of gneissic and supracrustal rocks, respectively. This deformation and metamorphism, except for G5 and M3, is Neoarchean (ca. 2. 68?2. 61 Ga), and represents a significant movement of crustal blocks: km-scale shearing of the supracrustal assemblage and consequent uplift of the Split Lake Block. Late deformation and metamorphism (G5, M3) may be related to the Paleoproterozoic Trans-Hudson orogeny. The Neoarchean and Paleoproterozoic zircon populations in the geochronological data suggest that the Gull Rapids area largely experienced Neoarchean deformation and metamorphism with a weak Paleoproterozoic overprint. All of the evidence presented above suggests that the Gull Rapids area lies in a part of the Superior Boundary Zone, yet does not lie at the exact margin of the Superior craton, and therefore does not mark the Archean-Proterozoic boundary proper in northeastern Manitoba.
NAPL Recovery Using CO₂-Supersaturated Water Injection: Distribution of the CO₂ Gas Phase
(University of Waterloo, 2006) Doughty, Cynthia
Gas inFusion? is a novel remedial technology that dissolves CO₂ into water under pressure for NAPL recovery. As the supersaturated liquid flows through the porous medium gas evolution occurs in situ as the system returns to thermodynamic equilibrium. The evolution of gas bubbles leads to NAPL recovery by two mechanisms: 1) volatilization and 2) mobilization by the NAPL spreading in a film around the rising bubbles. Laboratory experiments by Li demonstrated that injecting the supersaturated water into a porous medium minimized the buoyancy driven flow of gas and the fingering phenomena that limit typical gas sparging. The distribution of carbon dioxide at partial pressures (p_CO2) above the applicable hydrostatic pressure and the evolved gas phase were determined in two field experiments conducted in the relatively homogeneous fine to medium sand at CFB Borden. First, CO₂-supersaturated water was injected into a single point located approximately 4 metres below ground surface. Then this injection was repeated with pumping of two nearby wells to see if the lateral distribution of CO₂ gas could be controlled hydraulically. Groundwater monitoring of p_CO2 above the hydrostatic pressure and geophysical surveys (neutron measurements, surface ground penetrating radar (GPR), and cross-borehole GPR) to find zones of induced gas content were supported by hydraulic monitoring and physical observations of gas bubble distribution at the water table.

Based on the results of these tests, enhanced CO₂ levels above the hydrostatic pressure were observed up to 5. 5-7. 0 m from the injection point and the gas phase up to ~5. 3 m. It was not possible to determine the impact hydraulic control had on the lateral distribution of CO₂ due to problems with the experiment. The distribution of the gas phase was heterogeneous with CO₂ gas pockets forming below low permeability layers, as evidenced by surface GPR, permeameter tests, and grain size analyses. These gas pockets accumulated until sufficient pressure built up to overcome the displacement pressure of these lower permeability layers. At this point there is evidence of CO₂ breakthrough in the cross-borehole GPR data and physical observations of gas bubbles at the water table. These observations are consistent with previous investigations, which indicate that although the Borden aquifer is homogeneous, distinct horizontal layering is present with sufficient variations in permeability/displacement pressure to trap and cause some lateral spreading of a gas phase. The evidence of channeling and the impact of heterogeneities on gas distribution are consistent with air sparging studies.
Seismic Coupling and Hydrological Responses
(University of Waterloo, 2006) Rashid, Shahid
In seismology, the capability of an earthquake to induce other seismic events has been widely accepted for decades. For example, the term aftershock involves a strong relation of such a seismic event with the incidence of a main shock. Moreover, hydrological changes (water level in wells and streams, geyser eruption and remote seismicity) in response to remote earthquakes have been reported for many years. A matter of current debate concerns the spatiotemporal scale of interaction among seismic events. However, there appears to be no clear image of what is the exact method of transmission of the triggering energy for the phenomena listed above. It appears that the P-wave and the S-wave are inadequate in terms of ground strain magnitudes at teleseismic distances, while the amplitude of the surface waves generally decreases exponentially with depth in the Earth and could not be responsible for triggering deeper earthquakes or deep-seated fluid flow fluxes in 3-5 km deep reservoirs. This leaves some other wave as a possible triggering energy sources.

This thesis is based on a diffusion-dynamic theory that predicts a low velocity displacement wave, called a soliton wave, propagating in liquid-saturated porous media with velocity ~100-300 m/s, analogous to a tsunami that travels with the loss of little energy. This is hypothesized to be the mechanism for energy transfer that could be sufficient to promote changes in local pore pressure and therefore to alter the ambient effective stresses. It is also hypothesized that a soliton wave packet is emitted by a primary seismic event and may trigger sympathetic secondary earthquakes at a remote distance, fluid level fluctuation in wells, changes in geyser eruption behaviour, and changes in microseismic frequency, amplitude and patterns in appropriate places (e. g. under water reservoirs, in areas of active hydrothermalism, in tectonically active areas, and so on).

This thesis undertakes a review of some of these phenomena, and finds that the evidence as to what is the triggering mechanism is not clear. Also, it appears that the soliton hypothesis is not at all disproved by the data, and there may be some evidence of its existence.

To reveal the evidence of this kind of wave (soliton) in nature, real sequence and K-Q cases velocity data bases of earthquake interactions in the year of 2003 have been constructed by using information from Incorporated Seismological Research Institute (IRIS). The qualitative and quantitative analysis demonstrates that interactions between seismological and hydrological systems due to soliton waves are a definite possibility. However, the growth of fluid fluxes, geysers eruption and remote seismicity are controlled by both the principal stresses and the pore pressure. Hence, this interaction depends on the hydromechanical properties of rock such as permeability, compressibilities, and viscosities of fluids, saturations, and porosity. Perhaps the strongest argument in favour of a low-velocity soliton trigger is that the other seismic waves seem to be inadequate, and there is no evidence for their actions as a trigger.

The practice of detection and analysis of a soliton is not undertaken in this work. Because current devices are incapable to measure such a wave as they are on the surface and insensitive to liquid-solid coupling, sensitive and precise sensors in the low frequency range must be installed within the liquid saturated zone, preferably under the water table, to advance further work.
Evaluation of Geochemical and Reactivity Changes of Different Iron Materials
(University of Waterloo, 2006) O, Jin suk
Previous studies have suggested that iron PRBs, receiving high concentrations of inorganic constituents in groundwater, may experience passivation because of the accumulation of inorganic precipitates. In an iron PRB containing more highly reactive material, even though the initial contaminant removal rate is faster than for less reactive material, a faster migration of the contaminant removal front may occur due to the greater reactivity loss, caused by faster accumulation of secondary precipitates. In contrast, an iron PRB containing less reactive material may show a slower accumulation of precipitates, and thus will show a slower migration of the contaminant removal front over time. Thus, it is hypothesized that an iron material having moderate initial reactivity may be more advantageous than material having a higher reactivity in terms of long-term performance. The objective of this study was to test this hypothesis by evaluating the changes of the reactivities of different iron materials in the presence of dissolved CaCO₃.

Four different iron materials (Connelly, G-M, Ispat and Peerless) were selected for the column experiments. The changes in reactivities of the iron and formation of secondary precipitates over time were assessed, primarily by the iron corrosion rates, calculated from the hydrogen gas generation rates, by the cis-DCE removal rates and by the alkalinity profiles. The accumulation of precipitates in the four columns caused passivation of the iron. The passivation of the iron in turn resulted in migration of the mineral precipitation fronts as well as profiles of cis-DCE, TCE, VC, alkalinity, Eh, pH, and chloride. Connelly and G-M had longer periods of operation than Ispat and Peerless and thus their performance was the primary test of the hypothesis. G-M iron, which had the higher initial corrosion rate, compared to Connelly, showed a faster accumulation of precipitates near the influent end. The difference in accumulated precipitates resulted in a difference in the leading edge of the organic profiles and a significant difference in the pattern of passivation, indicating a faster passivation in the region near the influent end for G-M.

Model simulations were performed using the same fitting parameters but with different initial corrosion rate constants to further test the hypothesis. The model provided a reasonable representation of changing reactivities of the columns, being consistent with the observed data. In the simulation for long-term prediction, the cases of higher corrosion rates showed earlier breakthroughs and steeper curves than those of lower corrosion rates. Also, the predictions showed greater porosity loss for the case of higher corrosion rate. Thus, long-term predictions support the hypothesis. Accurate determination of model parameters such as cis-DCE degradation rate constants and iron corrosion rates are required for better predictions of long-term performance.

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