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Jasper AB
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Evaluation of groundwater flow and salt transport within an undrained tailings sand dam


Author(s): Price, A. C. R.

Year: 2005

Abstract:
Groundwater flow and salt transport in an undrained tailings sand dam is investigated at Syncrude Canada's Mildred Lake Oil Sands mine, in northeast Alberta. Two dimensional groundwater flow and salt transport are characterized using field data from two detailed piezometer transects. Calibrated steady-state groundwater flow and transient salt transport models simulate existing and future flow systems and flushing of process water. Dyke topography creates nested flow patterns, which are modified in some cases by variations in hydraulic conductivity. Greater relief of the backward-sloped bench design compared with forward-sloped benches results in larger local flow systems, a deeper water table, flushing of process water and focused discharge. Under the existing flow conditions captured by the model, salts will flush in decades at the local scale (bench) and centuries at the intermediate scale (perimeter dyke). The future flow regime will depend strongly on recharge rates across the reclaimed dam.

Evaluation of groundwater flow and salt transport within an undrained tailings sand dam


Author(s): Price, A. C. R.

Year: 2005

Abstract:
Groundwater flow and salt transport in an undrained tailings sand dam is investigated at Syncrude Canada's Mildred Lake Oil Sands mine, in northeast Alberta. Two dimensional groundwater flow and salt transport are characterized using field data from two detailed piezometer transects. Calibrated steady-state groundwater flow and transient salt transport models simulate existing and future flow systems and flushing of process water. Dyke topography creates nested flow patterns, which are modified in some cases by variations in hydraulic conductivity. Greater relief of the backward-sloped bench design compared with forward-sloped benches results in larger local flow systems, a deeper water table, flushing of process water and focused discharge. Under the existing flow conditions captured by the model, salts will flush in decades at the local scale (bench) and centuries at the intermediate scale (perimeter dyke). The future flow regime will depend strongly on recharge rates across the reclaimed dam.

Evaluation of the capability of aggregated oil sands mine tailings: Biological indicators


Year: 2003

Abstract:
An experiment was initiated in 1997 in northeast Alberta at the Syncrude Canada Ltd. Mildred Lake site to field test an innovative technique for reclamation of oil sand mine tailings. This technique was used to create an aggregated soil material from oil sand tailings. A plant community was successfully established on the soil material created by this technique. However, whether the site would be capable of supporting a self-sustainable ecosystem for the long-term remained a challenging issue. We evaluated the capability of these aggregated oil sand tailings by using biological indicators of the abundance and diversity of soil microbial biomass. Soil respiration rates and soil microbial biomass measurements were used to assess the abundance and activities of soil microbial communities. The ability of soil microbial biomass to utilize a diverse range of carbon substrates was used to assess the diversity of soil microbial communities. Soil biological activity increased with increasing growth of plant biomass and over time. Increasing the amount of peat moss or muskeg incorporated into the soil during reclamation resulted in higher organic carbon and nitrogen content and caused an increase in abundance and diversity of soil microbial biomass. These results indicate that measurements of soil respiration and substrate utilization by soil microbial communities may be used as biological indicators for assessing the capability of reclaimed soils.

Evaluation of trees and shrubs for oil sands reclamation: Field trial results


Year: 1987

Abstract:
The Alberta Oil Sands Environmental Research Program (AOSERP) Subproject VE 7.1 was initiated to select suitable tree and shrub species for use in revegetating spoils and tailings resulting from oil sands mining operations in northeastern Alberta. As part of this program three field trials were established near the Mildred Lake field camp, approximately 38 km north of Fort McMurray, in 1980 and 1981. The purpose was to test one or more provenances (seed sources) of promising native and exotic woody species. The trial site was prepared to simulate an oil sands reclamation situation. Overburden and peat were hauled to the site from Syncrude Canada Ltd.’s mining lease and incorporated in native sand. The resulting reconstructed soil was alkaline (pH 7.5), non-saline, and low in available N, P, and K. No fertilizers were added. A fine-mesh fence was erected around the trial site to exclude small mammals. All species were outplanted as one- or two-year-old container stock. All seed used to rear the native species was collected from local populations in the oil sands region. In August 1986 the trials were assessed. Survival rates were high for most species. Girdling damage by small mammals was almost non-existent, probably because of the fine-mesh fencing. Populus Northwest and P. Tristis #1 were the tallest and fastest growing species. Among the native species, Pinus banksiana was the tallest and fastest growing. Several other species also performed well and may be suitable for oil sands reclamation: Caragana arborescens, Cornus stolonifera, Elaeagnus commutata, Empetrum nigrum, Picea glauca, Picea mariana, and Populus Brooks #6. Some species gave mediocre or inconsistent performances, including Betula glandulosa, Betula papyrifera, Populus Walker, and Vaccinium vitis-idaea. The remaining species were failures and may not be adapted to the test site environment: Acer negundo, Alnus tenuifolia/crispa, Elaeagnus angustifolia, Fraxinus pennsylvanica, Lonicera tartarica, Populus tremuloides, Rosa woodsii, Salix acutifolia, Salix fragilis var. basfordiana, Salix pentandra, and Ulmus pumila. There were few significant differences among provenances for any of the native species. This suggests that genotypic differences were small among the populations tested.

Evolution of the hydraulic conductivity of reclamation covers over sodic/saline mining overburden


Year: 2011

Abstract:
The evolution of the field saturated hydraulic conductivity of four covers located on a reclaimed saline-sodic shale overburden from oil sands mining is presented. Three covers consisted of a surface layer of peat/glacial topsoil over a mineral, soil. and one cover was a single layer of mixed peat and mineral soil. Measurements of the field saturated hydraulic conductivity of the cover and shale materials were made with a Guelph permeameter between 2000 and 2004. The hydraulic conductivity of the cover materials in the multilayered covers increased by one to two orders of magnitude over the first few monitoring seasons. The hydraulic conductivity of the single-layer cover system, which was placed three years before the multilayered covers, marginally increased from 2000 to 2002 and then remained relatively unchanged. The hydraulic conductivity of the shale underlying all four covers increased approximately one order of magnitude. Soil temper- ature measurements indicated that one freeze/thaw cycle occurred each year within all cover soils and the surficial overburden. This suggests that freeze/thaw effects were the cause of the observed increases in hydraulic conductivity, as previously observed by other researchers working on compacted clays.

Gill and liver histopathological changes in yellow perch (Perca flavescens) and goldfish (Carassius auratus) exposed to oil sands process-affected water


Year: 2006

Abstract:
The extraction of bitumen from the Athabasca oil sands (Alberta, Canada) produces significant volumes of process-affected water containing elevated levels of naphthenic acids (NAs), ions, and polycyclic aromatic hydrocarbons (PAHs). The sublethal response of aquatic organisms exposed to oil sands constituents in experimental aquatic environments that represent possible reclamation options has been studied. In this study, the effects of process-affected waters on gill and liver tissues in yellow perch (Perca flavescens) and caged goldfish (Carassius auratus) held in several reclamation ponds at Syncrude's Mildred Lake site have been assessed. Following a 3-week exposure, significant gill (epithelial cell necrosis, mucous cell proliferation) and liver (hepatocellular degeneration, inflammatory cell infiltration) histopathological changes were noted in fish held in waters containing high levels of oil sands process-affected water. In addition, measurements of gill dimensions (gill morphometrical indices) proved sensitive and provided evidence of a physiological disturbance (gas exchange) with exposure to oil sands materials. Due to the complexity of oil sands process-affected water, the cause of the alterations could not be attributed to specific oil sands constituents. However, the histopathological parameters were strong indicators of exposure to oil sands process-affected water and morphometrical data were sensitive indicators of pathological response, which can be used to identify the interactive effects of ionic content, NAs, and PAHs in future laboratory studies

Growing season energy and water exchange from an oil sands overburden reclamation soil cover Fort McMurray, Alberta, Canada


Author(s): Carey, S. K.

Year: 2008

Abstract:
The oil sands mining industry in Canada is required to return mining areas to a land capability equivalent to that which existed prior to mining. During the reclamation process, ecosystems are created that bear little similarity to boreal forests that existed prior to mining. Quantifying the water balance of reclaimed ecosystems is critical in establishing whether there is sufficient moisture for vegetation growth and in the fate of salts, which can be toxic when drawn to the surface or leached out of the covers. At Syncrude Canada Ltd's Mildred Lake mine north of Fort McMurray, Alberta, the surface energy balance was measured atop a reclaimed saline-sodic overburden pile during three growing seasons using eddy covariance. At the onset of the study, the dominant vegetation was foxtail barley, which changed to sweet clover in 2004, and a low-density species mix in 2005, including some aspen and white spruce seedlings. The 2005 growing season was cooler and wetter than 2003 and 2004, and there were seasonal differences in the delivery of precipitation among years. There were distinct differences in the surface energy balance among the study years related to weather, soil moisture, vegetation and stage of growth. Latent heat was the largest consumer of energy in 2003, and mid-day fluxes of sensible and latent heat were approximately equal. In 2004, sensible heat became the dominant flux, primarily due to prolonged dry periods, whereas the wet 2005 season had the greatest latent heat flux density of any year. Ground heat flux declined throughout the growing season and ranged between 3 and 17% of net radiation. Total evapotranspiration was 246, 224 and 283 mm for 2003, 2004 and 2005, respectively. A total derivative analysis of the Penman-Monteith equation reveals the influence of available energy, vapour pressure deficit and surface conductance in controlling evapotranspiration.

Hydrogeologic characterization of a newly constructed saline-sodic clay overburden hill


Author(s): Chapman, D. E.

Year: 2008

Abstract:
Syncrude Canada Ltd (Syncrude) Mildred Lake operation is the largest producer of crude oil from oil sands mining in Canada. A saline-sodic clay-shale overburden known as the Clearwater Formation (Kc) must be removed in order to access the oil-bearing McMurray Formation (Km). The potential concerns associated with the reclamation of overburden structures include shale weathering and salt release and migration, resulting in salinization of groundwater, surface water, and reclamation soil covers. South Bison Hill (SBH) is one example of a Kc overburden structure located at the Syncrude Mildred Lake Operation. The general objective of this study is to develop a preliminary conceptual/interpretative model of the hydrogeology of the newly reclaimed SBH at the Syncrude mine site. A number of tasks were undertaken to meet this general objective. The first, and most important aspect of this study was to develop a geological model of SBH including pile geometry and depositional history of the hill. Secondly, to gain an understanding of the field conditions, a program was carried out over 2002 and 2003 to obtain pile physical characteristics. The geological model revealed that there are four main geological sections of SBH of different materials using different construction methods. The field data were used to verify the geological model, which illustrated the differences in hydraulic conductivities and geochemical signatures between the different sections. All information was used to develop a simple steady-state numerical seepage model of SBH to be used as a tool to investigate the response of the water levels of SBH to variations in the model parameters. The model illustrated that groundwater flow is largely controlled by a more permeable section on the south side of SBH and an unstructured Kc fill at the base of the pile. A sensitivity analysis was conducted on the model changing the flux into the pile, the permeability of the materials, and most importantly the head value of the tailings facility located on the north side both showing to be influential on the elevation of the water table through SBH.

Hydrological modelling of reconstructed watersheds using system dynamics


Author(s): Elshorbagy, A., & Jutla A.

Year: 2006

Abstract:
The mining of oil sands in the sub-humid region of Northern Alberta, Canada causes large-scale landscape disturbance, which subsequently requires extensive reclamation to re-establish the surface and subsurface hydrology. The reconstructed watersheds examined in this study are located at the Syncrude Canada Limited mine site, 40 km North of Fort McMurray, Alberta, Canada. The three experimental reconstructed watersheds, with nominal soil thicknesses of 1.0 m, 0.50 m and 0.35 m comprised a thin layer of peat (15-20 cm) over varying thicknesses of secondary (till) soil, have been constructed to cover saline sodic overburden and to provide sufficient moisture storage for vegetation while minimizing surface runoff and deep percolation to the underlying shale overburden. In order to replicate the hydrological behavior, assess the sustainability, and trace the evolution over time of the reclaimed watersheds, a suitable modeling tool is needed. In this research, a model is developed using the system dynamics approach to simulate the hydrological processes in the three experimental reconstructed watersheds and to assess their ability to provide the various watershed functions. The model simulates the vertical and lateral water movement, surface runoff and evapotranspiration within each watershed. Actual evapotranspiration, which plays an important role in the hydrology of the Canadian semi-arid regions, is simulated using an indexed soil moisture method. The movement of water within the various soil layers of the cover is based on parametric relationships in conjunction with conceptual infiltration models. The feedback relationships among the various dynamic hydrologic processes in the watershed are captured in the developed System Dynamic Watershed Model (SDWM). Most hydrological models are evaluated using runoff as the determining criterion for model calibration and validation, while accounting for the movement of moisture in the soil as a water loss. Since one of the primary objectives of a reconstructed watershed is to maintain the natural flora and fauna, it is important to recognize that soil moisture plays an important role in assessing the performance of the reconstructed watersheds. In turn, soil moisture becomes an influential factor for quantifying the health of the reconstructed watershed. The developed model has been calibrated and validated with data for two years (2001-2002), upholding the sensitive relationship between soil moisture and runoff. Accurate calibration of the model based on simulations of soil moisture in the various soil layers improves its overall performance. The model was subsequently used to simulate the three sub-watersheds for five years, with changing the calibrated model parameters to use them as indicators of watershed evolution. The simulated results were compared with the observed values. The results of the study illustrate that all three watersheds are still evolving. Failure to identify a unique parameter set for simulating the watershed response supports the hypothesis of watershed evolution. Soil moisture exchange between the till and peat layers changed with time in all of the watersheds. There was also a modest change in the water movement from the till to shale layers in each of the sub-watersheds. Vegetation is increasing in all of watersheds although there is an indication that one of the sub-watersheds may be sustaining deep rooted vegetation. The results demonstrate the successful application of the system dynamics approach and the developed model in simulating the hydrology of reconstructed watersheds and the potential for using this approach in assessing complex hydrologic systems. Degree:

Interim report of soil research related to revegetation of the oil sands area


Year: 1980

Abstract:
Monitoring was continued at instrumented sites which were selected in spring 1976, at Mildred Lake, Supertest Hill, the GCOS dike, and near Richardson Tower. Because of budget limitations, sites at Richardson were only monitored occasionally. However, information was obtained at a number of temporary 'outlying sites', which showed that conditions at the instrumented sites are fairly representative of those under similar vegetation in the surrounding area. Special emphasis in 1977, was placed on obtaining detailed information on moisture tensions using thermocouple psychrometers, and in acquiring accurate information on changes in moisture distribution during spring thaw. Growth of grasses and legumes in tailings sand, and the effect of adding materials such as peat and glacial till to tailings sand, were studied using lysimeters both indoors and in the field, and by establishing small plots, all of which were instrumented for gathering of physical and chemical information. Aspects of nutrient cycling such as nutrient inputs and outputs at forest sites, nitrogen mineralization and immobilization, retention of nitrogen by soil mixes, and decomposition of plant materials, were investigated with 15N and 14C. Laboratory studies were carried out on nitrogen and carbon cycling in tailings sand and two overburden materials. Much interpretation of information gathered over the year is still to be done and will be included in the next report.

Interim report on characterization and utilization of peat in the Athabasca oil sands area


Year: 1979

Abstract:
Two sites have been established for the study of stored peat. These are located at Evansburg ; Alberta and on the Syncrude Canada Ltd. lease at Mildred Lake, Alberta. Fibric and mesic moss peat and fen peat have been investigated in terms of their physical, chemical and microbiological properties. Such material will eventually be stored at mining sites in the AOSERP study area, presumably for later use as an amendment to aid reclamation procedures. The main purpose of this research was to quantify the changes in chemical, physical and microbiological properties that are likely to take place in the peat after a period of prolonged storage. A freeze-dry, air-dry, and thaw experiment was initiated to assess the rate of decomposition in stores peat. This indicated that drying affects most physical properties of peat. Drying affects the microbial activity in peat as measured by enzyme activity and CO2 production. Generally freeze-drying appeared less detrimental than air drying. The stored material at Evansburg was essentially composed of peat, whereas at Mildred Lake the material was a heterogeneous mixture of peat and inorganic material (sand, silt and clay). Both sites were instrumented with fiberglass temperature-moisture cells in order to record the annual variation in temperature and moisture in the stored material. Cellulotytic activity was measured by imbedding filter paper in the stored material at both Evansburg and Mildred Lake. Initial results indicate greater cellulose decomposition in the mixed peat material at Mildred Lake than at Evansburg. A higher rate of CO2 evolution from the Mildred Lake samples indicated greater microbiological activity at this site. This increased activity may be attributed to the presence of the inorganic constituents in the pile and to the application of commercial fertilizer. In the investigation of the Mildred Lake stored material, positive correlations have been established between carbon content, and microbiological activity, enzyme activity, and cation exchange capacity. Those samples containing the greatest amount of peat were highest in microbiological and enzyme activity thus indicating a possible greater rate of decomposition. Unlike the stored material, undisturbed peat near Mildred Lake showed little activity. A similar investigation into the activity in the peat storage pile at Evansburg will be undertaken in 1978.

Issues in process control for the Syncrude extraction plant at their Mildred Lake site


Author(s): Mueller, E.

Year: 1996

Abstract:
This thesis deals with several process control issues related to Syncrude's extraction process. Since startup in 1978, many changes have been made to the extraction control system and numerous new sensors were installed. The potential benefits of these changes and additions have not been fully realized as yet due to a lack of suitable real time models capable of integrating the information from the new sensors into the overall control strategy. The topics discussed here are part of an ongoing effort by Syncrude Research to improve the control strategy for the extraction plant to achieve better reliability and throughput for the process. These include the development of a method for on-line calibration and performance evaluation of composition analyzers applied to the plant feed composition analyzer, spectral analysis of process data and an example for the design and implementation of a suitable filter to improve control loop performance, process time delay estimation and empirical model identification.

Long term prediction of vegetation performance on mined sands


Author(s): Bliss, L. C.

Year: 1977

Abstract:
This project on the \"Long Term Prediction of Vegetation Performance On Mined Sands\" (V.E.6.1) was undertaken to provide management with answers on the predictive ability to maintain different kinds of vegetation on raw sands. The research was designed as an integrated, multi-disciplinary program that would concentrate on the role of water stress in a dynamic soil-plant-atmosphere system of a planted grass cover and a natural Jack pine forest. To date only the latter project has been initiated because of the lack of funding and approval to work on the GCOS dike in 1975. This and the Syncrude dyke represent the worst (driest) environmental situation and therefore revegetation of other sand deposits should be more easily accomplished. The Richardson Fire Tower site was chosen because of the representativeness of its Jack pine - lichen woodland on deep sands, a forest type so characteristic of northeastern Alberta. The results of the first full year show that climatically this southwest-facing sand slope warms more rapidly in spring than do level sites at Mildred Lake and Fort McMurray and that the 1976 summer was above normal for temperature. Precipitation was near normal based upon the 1941 - 1970 period. Of the >60 days of precipitation, over 60% were 4 mm or less and thus little if any water entered the soil due to tree, lichen, and litter interception. Both needle duff and lichens provide a significant barrier to surface evaporation compared with open sand. Resistance to evaporation is 2 to 3 times greater with a lichen cover than with litter. The soils are very porous which is advantageous for water entrance, thus preventing erosion but porosity is a disadvantage in maintaining higher water levels near the soil surface for plant growth. These soils recharge during snowmelt in late March - early April; little runoff occurs and over the summer soil water drawdown takes place. Soil moisture content (volume basis) is generally 8 - 15% near the surface in spring, but by late September is 1 - 3% at all depths. Xylem water potentials, a measure of tree water content, were never very low (mean maximum at dawn -5 to -7 atm. and mean minimum at midday -11 to -14 atm.) which reflect a year of average precipitation with frequent light rains and periodic heavier storms. Transpiration and stomatal closure were controlled largely by vapour pressure deficits. Jack pine avoided spring drought by remaining dormant when air and needle temperatures were above freezing, yet when soils were still frozen. Although Jack pine did not show indications of severe drought in a relatively moist summer, it did develop xylem water potentials of -16 to -18 atm., values which are probably detrimental to many of the species being used in revegetation trials on the dike (Bromus inermis, Phleum pratense, and species of Agropyron). This means that potential species must be drought hardy and tested under laboratory rather than only under field conditions to determine their survival under severe drought conditions that may occur but once in 30 to 50 years. The studies of mycorrhizae show that a large number of species of fungi infect the roots of Jack pine and that the infecting flora from disturbed soils (old burns) is quite different from that of undisturbed forests. Since mycorrhizae are critical for the proper growth and survival of pines, care in innoculating tree seedlings with the proper species is essential. The energy and water balance mathematical model predicts the heat and water status of the Jack pine forest. Examination of the model outputs suggests that late season resistance to water uptake occurs because of increased root resistance in autumn. If this is confirmed with further experimental data, and model runs, it means that fall droughts may be especially critical because of the reduced ability of the trees to absorb water through their roots. A second field season coupled with the laboratory studies to determine lethal and sublethal levels of water stress in Jack pine will provide the added inputs to the models necessary for predicting tree response to severe climatic stress. These data, gathered in a highly integrated manner, will permit the calculation of tree survival on sands, be they dikes or other kinds of mined sand, in terms of soil water content and tree density (including crown extent) in relation to the exceptional dry year that may occur once in 30 to 50 years. Data from field trials of grasses or woody species, without supporting measurements of plant physiological responses to environmental conditions cannot provide this essential predictive tool for management unless the one in 30 to 50 year drought cycle is encountered. It is for this reason that modelling of the data in order to predict plant response to unusual environmental conditions becomes so useful. In summary, this study should be able to provide sufficient data to determine whether or not an open stand of Jack pine or similar conifer is the desired end point in maintaining vegetation at a low maintenance cost on sands, the result of open pit mining of the oil sands.

Mammalian toxicity of naphthenic acids derived from the Athabasca oil sands


Author(s): Rogers, V. V.

Year: 2003

Abstract:
Naphthenic acids are a diverse group of saturated mono- and polycyclic carboxylic acids that are natural constituents of petroleum. These compounds are a major contributor to petroleum's acidic nature and can account for as much as 4% of crude petroleum by weight. At the Athabasca oil sands (AOS) located in northeastern Alberta, Canada, naphthenic acids have received considerable attention. The AOS represent the world's largest, single petroleum deposit, where the petroleum is in the form of bitumen. Extracting bitumen from AOS is a complex process, requiring the mixing of oil sands with hot,alkaline (pH = 8.0) water to separate the bitumen from sand and other waste products. This process produces an immense volume of aqueous tailings, about 7.5 m 3 for each m3 of synthetic crude petroleum produced. Nearly one billion cubic meters of aqueous tailings will have amassed in large holding ponds near the mine sites by 2025, and will be incorporated into the ecosystem under wet and dry landscape reclamation strategies. Another consequence of the extraction process is that naphthenic acids (pKa ≅ 5) become solubilized and concentrated (90--110 mg/L) in aqueous tailings. Numerous studies have investigated the aquatic toxicity of naphthenic acids, demonstrating them to be highly toxic to invertebrates and fish at concentrations well below those found in AOS tailings. In contrast, information about the mammalian toxicity of naphthenic acids is limited, particularly the effects of repeated, oral exposure. In the current research, naphthenic acids were isolated from tailings obtained from Mildred Lake settling basin, the main tailings pond of Syncrude Canada Ltd, and used in mammalian toxicity testing. An acidification/solvent extraction procedure was used, followed by ultrafiltration to isolate the naphthenic acids. These were chemically analysed, revealing a highly heterogenous mixture of acyclic and 1-, 2-, 3-, and 4-ringed compounds. Acute testing using Wistar rats demonstrated significant (P < 0.05) behavioural and histopathological effects in both sexes at a single dosage of 300 mg/kg body weight of napthenic acids. This dosage is 50 times higher than the estimated worst-case, single day environmental exposure through drinking water for small mammals in the wild. Effects included temporary suppression of appetite, and pericholangitis, a biliary inflammatory response. Subchronic dosing, involving administration of naphthenic acids to females over a 90 d period, indicated that 60 mg/kg/d was sufficient to elicit significant (P < 0.05), toxic effects.

Mature fine tailings from oil sands processing harbour diverse methanogenic communities


Author(s): Penner, T. J., & Foght J. M.

Year: 2010

Abstract:
Processing oil sands to extract bitumen produces large volumes of a tailings slurry comprising water, silt, clays, unrecovered bitumen, and residual solvent used in the extraction process. Tailings are deposited into large settling basins, where the solids settle by gravity to become denser mature fine tailings (MFT). A substantial flux of methane, currently estimated at ~40 million L/day, is being emitted from the Mildred Lake Settling Basin. To better understand the biogenesis of this greenhouse gas, the methanogenic consortia in MFT samples from depth profiles in 2 tailings deposits (Mildred Lake Settling Basin and West In-Pit) were analyzed by constructing clone libraries of amplified archaeal and bacterial 16S rRNA genes. The archaeal sequences, whose closest matches were almost exclusively cultivated methanogens, were com- parable within and between basins and were predominantly (87% of clones) affiliated with acetoclastic Methanosaeta spp. In contrast, bacterial clone libraries were unexpectedly diverse, with the majority (~55%) of sequences related to Proteo- bacteria, including some presumptive nitrate-, iron-, or sulfate-reducing, hydrocarbon-degrading genera (e.g., Thauera, Rhodoferax, and Desulfatibacillum). Thus, MFT harbour a diverse community of prokaryotes presumptively responsible for producing methane from substrates indigenous to the MFT. These findings contribute to our understanding of biogenic methane production and densification of MFT in oil sands tailings deposits.

Meteorology and air quality winter field study in the AOSERP study area March 1976


Author(s): Fanaki, F.

Year: 1978

Abstract:
In March 1976, the first in a series of intensive field studies was carried out in the Alberta Oil Sands Environmental Research Program study area in northeastern Alberta to examine the fine structure of the atmosphere and dispersion characteristics under winter conditions. The study comprised several co-ordinated sets of measurements over a two week period. These included: minisonde flights, tethersonde vertical profiles, acoustic sounder and delta-T sonde profiles, correlation spectrometer and ground level sulphur dioxide measurements, plume rise photography and background air and precipitation chemistry. Plume dispersion measurements made by aircraft were co-ordinated with the study and are reported in a separate publication. All measurements, except those for background air chemistry, were made within 20 km of Mildred Lake taking in the present oil sands processing facility of Great Canadian Oil Sands Ltd. and the future production site of Syncrude Canada Ltd. The study was successful in identifying unique features of the winter environment of the area such as diurnal formation and breakup of inversion layers, the effects of the river valley on circulation patterns, plume characteristics, pollutant deposition patterns in the snowpack and background levels of gases and particulates.

Methane emissions from oil sand tailings by microbial metabolism of hydrocarbons


Author(s): Siddique, T., & Foght J.

Year: 2011

Abstract:
Enormous volumes of tailings produced during bitumen extraction from oil sands ores are stored in settling basins/tailings ponds. The current inventory of tailings in northern Alberta, Canada exceeds 850 million m3. Biogenic methane emissions have been observed from the surfaces of tailings ponds and about 40 million L of methane day-1 was estimated from a single tailings pond (Mildred Lake Settling Basin) in 1999. This research project was initiated to investigate the source and mechanism of methane emission from the oil sands tailings ponds. The mature fine tailings (MFT) were collected from Syncrude Canada Ltd. and Shell Albian Sands tailings ponds and investigated for methanogenic biodegradation of solvent hydrocarbons that are used in the bitumen extraction process and the residual fractions of these solvents that are present in the tailings deposited in the tailings ponds. Our laboratory experiments have shown that only short-chain n-alkanes (C6-C10) and certain monoaromatics (BTEX) present in C3-C14 range hydrocarbons entrained in Syncrude tailings are readily biodegraded by the indigenous microorganism in the tailings ponds to produce methane. In contrast, a very long acclimation period has been observed for indigenous microbes to degrade long-chain n-alkanes (C14-18) and branched alkanes such as 2-methylpentane. Experiments are in progress to monitor the degradation of these recalcitrant compounds. The molecular analysis of 16S rRNA genes revealed that different microbial communities are involved in the degradation of different groups of petroleum hydrocarbon in oil sands tailings. Understanding the mechanism(s) of biogenic methane production and predicting emissions from oil sands tailings ponds are important objectives for effective management of tailings and greenhouse gas emissions.

Methanogens and sulfate-reducing bacteria in oil sands fine tailings waste


Year: 2000

Abstract:
In the past decade, the large tailings pond (Mildred Lake Settling Basin) on the Syncrude Canada Ltd. lease near Fort McMurray, Alta., has gone methanogenic. Currently, about 60%–80% of the flux of gas across the surface of the tailings pond is methane. As well as adding to greenhouse gas emissions, the production of methane in the fine tailings zone of this and other settling basins may affect the performance of these settling basins and impact reclama- tion options. Enumeration studies found methanogens (105–106 MPN/g) within the fine tailings zone of various oil sands waste settling basins. SRB were also present (104–105 MPN/g) with elevated numbers when sulfate was avail- able. The methanogenic population was robust, and sample storage up to 9 months at 4°C did not cause the MPN val- ues to change. Nor was the ability of the consortium to produce methane delayed or less efficient after storage. Under laboratory conditions, fine tailings samples released 0.10–0.25 mL CH4 (at STP)/mL fine tailings. The addition of sul- fate inhibited methanogenesis by stimulating bacterial competition.

Microbial S biogeochemistry of oil sands composite tailings


Year: 2014

Abstract:
Oil sands tailings are important, globally relevant, S reservoirs, known to contain active and diverse microbial communities. However, the potential for S bigeochemical cycling occurring within composite tailings (CT), a mixture of fluid fine tailings, post-processed sand and gypsum (flocculant) used in dry reclamation approaches, has not been examined prior to this study. Biogeochemical characterization of CT solid and porewater samples taken from 5 depths over a 40 meter CT deposit (Mildred Lake, Syncrude Ltd, Fort McMurray, AB, CANADA) revealed distinct depth dependent zones of surficial iron reducing and more extensive sulphate reducing microbial activity. Porewater H2S was detected below 6 meters in the deposit ranging in concentration from 14–300 µM, while much lower concentrations, 1-40 µM, of porewater Fe2+ were restricted to surficial CT samples. Metagenomic (454 pyrosequencing) characterization revealed highly diverse CT microbial communities, with 21 different phyla encountered overall. However, consistent with the porewater geochemical profiles, two depth dependent, structurally distinct communities emerged from multivariate statistical analyses of phylogenetic data (UniFrac http://bmf.colorado.edu/unifrac): a surficial CT zone of Fe3+ reduction and an underlying, more extensive zone of SO42- reduction. These microbial zones were linked to DOC, redox and salinity conditions within the CT deposit. Consistent with the notion that accessible organic carbon was limiting IRB and SRB activity, available SO42- and Fe3+ sources were evident and abundant throughout the deposit. Pilot reclamation is currently focusing on capping CT with a freshwater wetland, reflecting the original boreal forest landscape. However a wetland may provide a more labile organic carbon source for underlying CT associated bacteria, which may stimulate greater H2S generation and/or aid sequestration through IRB driven FeS formation. Recent field and laboratory results from the adjacent CT pilot fen reclamation site suggest that stimulation of H2S generation associated with downwelling fen organic carbon inputs is occurring. These results identify the need to consider the potential for microbial biogeochemical transformations of waste materials to hinder the efficacy of proposed reclamation scenarios.

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