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Ahad J.M.E.,Geological Survey of Canada | Jautzy J.J.,INRS Eau Terre Environnement | Cumming B.F.,Queen's University | Das B.,Environment Canada | And 2 more authors.
Organic Geochemistry | Year: 2015

The past several decades have witnessed a significant expansion of mining activities in the Athabasca oil sands region, raising concerns about their impact on the surrounding boreal forest ecosystem. To better understand the extent to which distal sites are impacted by oil sands-derived airborne contaminants, we examine sources of polycyclic aromatic hydrocarbons (PAHs) in surface sediments and dated sediment cores from Saskatchewan lakes situated ~100-220km east-northeast of the main area of bitumen mining activities. The concentrations and fluxes of both parent and alkylated PAHs are low and show considerable variability over the past 70-100years. Small yet discernible increases in PAH concentrations and fluxes occurred over the past 30years, a trend which coincides with the rapid growth in bitumen production. However, several lines of evidence point to wildfires as the principal source of PAHs to these lakes: (1) the significant co-variations in most cores between retene (1-methyl-7-isopropyl phenanthrene) and other groups of parent and alkylated PAHs, (2) the similarity in compound specific δ13C signatures of the parent PAHs phenanthrene and pyrene in recently deposited surficial sediments and those corresponding to time intervals considerably pre-dating the large scale development of the oil sands and (3) the discernible up-core increases in the proportion of refractory carbon (i.e., char) in Rock-Eval 6 data. The collective evidence points to softwood combustion from boreal forest fires as the principal source of retene in sediments and the general increase in forest fire activity in this region over the past several decades as the source of refractory carbon. Mining activities associated with the Athabasca oil sands are thus not considered a major source of PAHs to these lakes. © 2015.


Ahad J.M.E.,Geological Survey of Canada | Pakdel H.,INRS Eau Terre Environnement | Savard M.M.,Geological Survey of Canada | Calderhead A.I.,INRS Eau Terre Environnement | And 4 more authors.
Environmental Science and Technology | Year: 2013

The high levels of acid extractable organics (AEOs) containing naphthenic acids (NAs) found in oil sands process-affected waters (OSPW) are a growing concern in monitoring studies of aquatic ecosystems in the Athabasca oil sands region. The complexity of these compounds has substantially hindered their accurate analysis and quantification. Using a recently developed technique which determines the intramolecular carbon isotope signature of AEOs generated by online pyrolysis (δ13Cpyr), natural abundance radiocarbon, and high resolution Orbitrap mass spectrometry analyses, we evaluated the sources of AEOs along a groundwater flow path from a major oil sands tailings pond to the Athabasca River. OSPW was characterized by a δ13Cpyr value of approximately -21‰ and relatively high proportions of O2 and O2S species classes. In contrast, AEO samples located furthest down-gradient from the tailings pond and from the Athabasca River were characterized by a δ13C pyr value of around -29‰, a greater proportion of highly oxygenated and N-containing compound classes, and a significant component of nonfossil and, hence, non-bitumen-derived carbon. The groundwater concentrations of mining-related AEOs determined using a two end-member isotopic mass balance were between 1.6 and 9.3 mg/L lower than total AEO concentrations, implying that a less discriminating approach to quantification would have overestimated subsurface levels of OSPW. This research highlights the need for accurate characterization of "naphthenic acids" in order to quantify potential seepage from tailings ponds. © 2013 American Chemical Society.


Gardet C.,French Institute of Petroleum | Le Ravalec M.,French Institute of Petroleum | Gloaguen E.,INRS Eau Terre Environnement
Stochastic Environmental Research and Risk Assessment | Year: 2016

Mass transport is known to depend on heterogeneity in geological formations. This entails geological bodies with complex geometries. The major interest of multiple-point simulation is its ability to reproduce such geological features through the use of a training image. The idea behind the training image is to describe a geological concept with the expected geological architecture. Its structural content is then used to infer multiple-point statistics. This yields a database with a variety of possible patterns or events. In this paper, we present a hybrid algorithm combining geostatistical multiplepoint and texture synthesis techniques for simulating geological reservoir models constrained to hard data. The proposed algorithm is a two steps process, involving first analysis with the building of an organized database from the training image content, and second synthesis with the simulation of a realization. Various tests are performed to investigate the potential of the algorithm in terms of computation time and ability to properly reproduce the shapes and connectivity features of the objects represented in the training image. We also propose a few improvements to make the algorithm more efficient. Last, six examples are presented based upon different kinds of training images depicting large-scale channelized and fractured media as well as fine-scale porous media. © 2016 Springer-Verlag Berlin Heidelberg


Gardet C.,French Institute of Petroleum | Le Ravalec M.,French Institute of Petroleum | Gloaguen E.,INRS Eau Terre Environnement
Mathematical Geosciences | Year: 2014

The prediction of fluid flows within hydrocarbon reservoirs requires the characterization of petrophysical properties. Such characterization is performed on the basis of geostatistics and history-matching; in short, a reservoir model is first randomly drawn, and then sequentially adjusted until it reproduces the available dynamic data. Two main concerns typical of the problem under consideration are the heterogeneity of rocks occurring at all scales and the use of data of distinct resolution levels. Therefore, referring to sequential Gaussian simulation, this paper proposes a new stochastic simulation method able to handle several scales for both continuous or discrete random fields. This method adds flexibility to history-matching as it boils down to the multiscale parameterization of reservoir models. In other words, reservoir models can be updated at either coarse or fine scales, or both. Parameterization adapts to the available data; the coarser the scale targeted, the smaller the number of unknown parameters, and the more efficient the history-matching process. This paper focuses on the use of variational optimization techniques driven by the gradual deformation method to vary reservoir models. Other data assimilation methods and perturbation processes could have been envisioned as well. Last, a numerical application case is presented in order to highlight the advantages of the proposed method for conditioning permeability models to dynamic data. For simplicity, we focus on two-scale processes. The coarse scale describes the variations in the trend while the fine scale characterizes local variations around the trend. The relationships between data resolution and parameterization are investigated. © 2013 International Association for Mathematical Geosciences.


PubMed | Geological Survey of Canada, Wilfrid Laurier University, INRS Eau Terre Environnement and University of Waterloo
Type: Journal Article | Journal: Environmental science & technology | Year: 2015

The downstream accumulation of polycyclic aromatic hydrocarbons (PAHs) in the Peace-Athabasca Delta (PAD), an ecologically important landscape, is a key issue of concern given the rapid development of the oil sands industry in Northern Alberta, Canada. In addition to PAHs derived from industrial activity (i.e., oil sands mining) within the Athabasca watershed, however, forest fires and erosion of fossil fuel deposits within both the Athabasca and Peace watersheds are two potentially important natural sources of PAHs delivered to the PAD. Consequently, evaluating the environmental impact of mining activities requires a quantitative understanding of natural, background PAHs. Here, we utilize molecular-level natural-abundance radiocarbon measurements on an amalgamated sediment record from a Peace River flood-susceptible oxbow lake in the northern Peace sector of the PAD to quantitatively discriminate sources of naturally occurring alkylated PAHs (fossil and modern biomass). A radiocarbon mass balance quantified a predominantly natural petrogenic source (93% petrogenic, 7% forest fire) for alkylated PAHs during the past 50 years. Additionally, a significant petrogenic component determined for retene, a compound usually considered a biomarker for softwood combustion, suggests that its use as a unique forest fire indicator may not be suitable in PAD sediments receiving Peace watershed-derived fluvial inputs.


Ahad J.M.E.,Geological Survey of Canada | Pakdel H.,INRS Eau Terre Environnement
Environmental Science and Technology | Year: 2013

Compound-specific stable (δ13C) and radiocarbon (Δ14C) isotopes of phospholipid fatty acids (PLFAs) were used to evaluate carbon sources utilized by the active microbial populations in surface sediments from Athabasca oil sands tailings ponds. Algal-specific PLFAs were absent at three of the four sites investigated, and δ 13CPLFA values were generally within ∼3‰ of that reported for oil sands bitumen (∼-30‰), suggesting that the microbial communities growing on petroleum constituents were dominated by aerobic heterotrophs. Δ14CPLFA values ranged from -906 to -586‰ and pointed to significant uptake of fossil carbon, particularly in PLFAs (e.g., cy17:0 and cy19:0) often associated with petroleum hydrocarbon degrading bacteria. The comparatively heavier Δ14C values found in other, less specific PLFAs (e.g., 16:0) indicated the preferential uptake of younger organic matter by the general microbial population. Since the main carbon pools in tailings sediment were essentially "radiocarbon dead" (i.e., Δ14C ∼ -1000‰), the principal source for this relatively modern carbon is considered to be the Athabasca River, which provides the bulk of the water used in the bitumen extraction process. The preferential utilization of the minor amount of younger and presumably more labile material present in systems otherwise dominated by petroleum carbon has important implications for remediation strategies, since it implies that organic contaminants may persist long after reclamation has begun. Alternatively, this young organic matter could play a vital and necessary role in supporting the microbial utilization of fossil carbon via cometabolism or priming processes. © 2013 American Chemical Society.


Jautzy J.,INRS Eau Terre Environnement | Ahad J.M.E.,Geological Survey of Canada | Gobeil C.,INRS Eau Terre Environnement | Savard M.M.,Geological Survey of Canada
Environmental Science and Technology | Year: 2013

Evaluating the impact that airborne contamination associated with Athabasca oil sands (AOS) mining operations has on the surrounding boreal forest ecosystem requires a rigorous approach to source discrimination. This study presents a century-long historical record of source apportionment of polycyclic aromatic hydrocarbons (PAHs) in dated sediments from two headwater lakes located approximately 40 and 55 km east from the main area of open pit mining activities. Concentrations of the 16 Environmental Protection Agency (EPA) priority PAHs in addition to retene, dibenzothiophene (DBT), and six alkylated groups were measured, and both PAH molecular diagnostic ratios and carbon isotopic signatures (δ13C) of individual PAHs were used to differentiate natural from anthropogenic inputs. Although concentrations of PAHs in these lakes were low and below the Canadian Council of Ministers of the Environment (CCME) guidelines, diagnostic ratios pointed to an increasingly larger input of petroleum-derived (i.e., petrogenic) PAHs over the past 30 years concomitant with δ13C values progressively shifting to the value of unprocessed AOS bitumen. This petrogenic source is attributed to the deposition of bitumen in dust particles associated with wind erosion from open pit mines. © 2013 American Chemical Society.


Jautzy J.J.,INRS EAU Terre Environnement | Ahad J.M.E.,Geological Survey of Canada | Gobeil C.,INRS EAU Terre Environnement | Smirnoff A.,Geological Survey of Canada | And 2 more authors.
Environmental Science and Technology | Year: 2015

The continued growth of mining and upgrading activities in Canadas Athabasca oil sands (AOS) region has led to concerns about emissions of contaminants such as polycyclic aromatic hydrocarbons (PAHs). Whereas a recent increase in PAH emissions has been demonstrated within around 50 km of the main center of surface mining and upgrading operations, the exact nature of the predominant source(s) and the geographical extent of the deposition are still under debate. Here, we report a century-long source apportionment of PAHs using dual (δ2H, δ13C) compound-specific isotope analysis on phenanthrene deposited in a lake from the Athabasca sector of the Peace-Athabasca Delta situated ∼150 km downstream (north) of the main center of mining operations. The isotopic signatures in the core were compared to those of the main potential sources in this region (i.e., unprocessed AOS bitumen, upgrader residual coke, forest fires, coal, gasoline and diesel soot). A significant concurrent increase (∼55.0‰) in δ2H and decrease (∼1.5‰) in δ13C of phenanthrene over the last three decades pointed to an increasingly greater component of petcoke-derived PAHs. This study is the first to quantify long-range (i.e., >100 km) transport of a previously under-considered anthropogenic PAH source in the AOS region. © 2015 American Chemical Society.


Ahad J.M.E.,Geological Survey of Canada | Pakdel H.,INRS Eau Terre Environnement | Savard M.M.,Geological Survey of Canada | Simard M.-C.,Geological Survey of Canada | Smirnoff A.,Geological Survey of Canada
Analytical Chemistry | Year: 2012

Here we report a novel approach to extract, isolate, and characterize high molecular weight organic acids found in the Athabasca oil sands region using preparative capillary gas chromatography (PCGC) followed by thermal conversion/elemental analysis-isotope ratio mass spectrometry (TC/EA-IRMS). A number of different "naphthenic acids" surrogate standards were analyzed as were samples from the bitumen-rich unprocessed McMurray Formation, oil sands process water, groundwater from monitoring wells, and surface water from the Athabasca River. The intramolecular carbon isotope signature generated by online pyrolysis (δ13Cpyr) showed little variation (±0.6°) within any given sample across a large range of mass fractions separated by PCGC. Oil sand, tailings ponds, and deep McMurray Formation groundwater were significantly heavier (up to ∼9°) compared to surface water and shallow groundwater samples, demonstrating the potential use of this technique in source apportionment studies. © 2012 American Chemical Society.


PubMed | Geological Survey of Canada and INRS Eau Terre Environnement
Type: Journal Article | Journal: Environmental science & technology | Year: 2015

The continued growth of mining and upgrading activities in Canadas Athabasca oil sands (AOS) region has led to concerns about emissions of contaminants such as polycyclic aromatic hydrocarbons (PAHs). Whereas a recent increase in PAH emissions has been demonstrated within around 50 km of the main center of surface mining and upgrading operations, the exact nature of the predominant source(s) and the geographical extent of the deposition are still under debate. Here, we report a century-long source apportionment of PAHs using dual ((2)H, (13)C) compound-specific isotope analysis on phenanthrene deposited in a lake from the Athabasca sector of the Peace-Athabasca Delta situated 150 km downstream (north) of the main center of mining operations. The isotopic signatures in the core were compared to those of the main potential sources in this region (i.e., unprocessed AOS bitumen, upgrader residual coke, forest fires, coal, gasoline and diesel soot). A significant concurrent increase (55.0) in (2)H and decrease (1.5) in (13)C of phenanthrene over the last three decades pointed to an increasingly greater component of petcoke-derived PAHs. This study is the first to quantify long-range (i.e., >100 km) transport of a previously under-considered anthropogenic PAH source in the AOS region.

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