Isotopic Evidence for Oil Sands Petroleum Coke in the Peace

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Isotopic evidence for oil sands petroleum coke in the Peace-Athabasca Delta Josué Jules Jautzy, Jason M.E. Ahad, Charles Gobeil, Anna Smirnoff, Benjamin D Barst, and Martine M. Savard Environ. Sci. Technol., Just Accepted Manuscript • Publication Date (Web): 24 Sep 2015 Downloaded from http://pubs.acs.org on September 26, 2015

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Environmental Science & Technology

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Isotopic evidence for oil sands petroleum coke in the

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Peace-Athabasca Delta

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Josué J. Jautzy1, Jason M. E. Ahad2*, Charles Gobeil1, Anna Smirnoff2, Benjamin D. Barst1,

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Martine M. Savard2

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INRS Eau Terre Environnement, Québec, QC, G1K 9A9, Canada

Geological Survey of Canada, Natural Resources Canada, Québec, QC, G1K 9A9, Canada, Email: [email protected] (*corresponding author)

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Revised version submitted to Environmental Science & Technology

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16 September 2015

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ABSTRACT: The continued growth of mining and upgrading activities in Canada’s Athabasca

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oil sands (AOS) region has led to concerns about emissions of contaminants such as polycyclic

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aromatic hydrocarbons (PAHs). Whereas a recent increase in PAH emissions has been

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demonstrated within around 50 km of the main center of surface mining and upgrading

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operations, the exact nature of the predominant source and the geographical extent of the

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deposition are still under debate. Here, we report a century-long source apportionment of PAHs 1 ACS Paragon Plus Environment


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using dual (δ2H, δ13C) compound-specific isotope analysis on phenanthrene deposited in a lake

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from the Athabasca sector of the Peace-Athabasca Delta situated ~150 km downstream (north) of

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the main center of mining operations. The isotopic signatures in the core were compared to those

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of the main potential sources in this region (i.e., unprocessed AOS bitumen, upgrader residual

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coke, forest fires, coal, gasoline and diesel soot). A significant concurrent increase (~ 55.0‰) in

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δ2H and decrease (~ 1.5‰) in δ13C of phenanthrene over the last three decades pointed to an

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increasingly greater component of petcoke-derived PAHs. This study is the first to quantify long-

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range (i.e., > 100 km) transport of a previously under-considered anthropogenic PAH source in

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the AOS region.

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INTRODUCTION

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Studies carried out over the past decade have demonstrated that industrial activities

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associated with the surficial mining and processing of Athabasca oil sands (AOS) bitumen have

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led to increased loadings of organic contaminants such as polycyclic aromatic hydrocarbons

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(PAHs) to the surrounding environment.1-4 PAHs, which are found at naturally high levels in

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petrogenic sources such as AOS bitumen,5 are also produced pyrogenically during the

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incomplete combustion of organic matter (OM) and biologically during early sediment

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diagenesis. Understanding the impact of oil sands mining activities on the surrounding

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environment thus requires techniques which can discriminate between these disparate sources.

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“Classical” source apportionment studies of PAHs are carried out using molecular

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concentration patterns and ratios (i.e., the ratio of a pyrogenic over a petrogenic PAH).6 Using

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these techniques, the main sources of mining-related PAH deposition in the AOS region have

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been attributed thus far to fugitive dust from open pit mining activities and/or emissions from 2 ACS Paragon Plus Environment

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bitumen upgrading facilities.1-2,

7-8

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however, source discrimination using PAH diagnostic ratios can be problematic. For instance,

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petrogenic PAH diagnostic ratios characteristic of AOS bitumen may resemble pyrogenic ratios

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associated with boreal forest wildfires.9 In addition, while the observation of relatively high

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proportions of dibenzothiophenes (DBTs) and alkylated PAHs in AOS bitumen5 has been used

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as an indicator of mining-related inputs,1-2 these compounds can also originate from other

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sources such as biomass burning.10-11

Due to the potential similarity in end-member signatures,

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To overcome the limitations of “classical” PAH source apportionment approaches,

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additional environmental forensics tools need to be used. One such technique that has shown

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promise in evaluating sources of PAHs is stable carbon (δ13C) compound-specific isotope

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analysis (CSIA).12-16 Recent applications of this technique in the AOS region have provided

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evidence for a fugitive dust source for PAHs deposited in a headwater lake situated 55 km

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southeast of the main area of mining operations3 and also for a predominantly wildfire

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contribution to PAH loading to northwest Saskatchewan lakes located ~100 to 220 km east-

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northeast of the main area of mining operations.9 Despite the potential for δ13C-CSIA to

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discriminate sources within binary mixing systems, further research is needed in order to refine

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the quantitative attribution of PAHs to the different mining and non-mining related inputs in the

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AOS region and assess the geographic extent of these emissions.4, 8, 17-22

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The characterization of both stable carbon and hydrogen (δ2H) isotopic ratios on the same

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molecule (i.e., dual-CSIA) is one approach that, by incorporating an additional parameter in the

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mixing system, could greatly improve source discrimination of PAHs in the AOS region. Sun et

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al.23 demonstrated the ability of dual-CSIA of PAHs to distinguish between closely related

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emission sources, and Wang et al.24 revealed that this approach could shed valuable insight into 3 ACS Paragon Plus Environment


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the understanding of complex mixtures of PAHs dissolved in surface water. Given the potential

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for highly complex mixtures in lake sediments in the AOS region, the application of both δ13C-

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CSIA and δ2H-CSIA could allow for a greater separation and possible quantification of the

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various natural and mining-related PAH inputs, provided that the signatures of the main end-

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members are known.

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In this study, we report a detailed historical analysis of PAH sources and deposition in a

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lake located in the Peace-Athabasca Delta (PAD), an ecologically important landscape composed

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of a system of interconnected channels and lakes. The PAD lies outside of the previously

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identified zone of mining-related PAH atmospheric deposition.1-2 A variety of parameters were

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used to characterize OM (i.e., percentage and δ13C of total organic carbon, C/N ratio and

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radiocarbon abundances of the solvent-extractable fraction containing bitumen) and PAHs (i.e.,

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composition and dual-CSIA of phenanthrene) in a dated, amalgamated sediment core in order to

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provide a refined understanding of the source variability over the last century. With the help of a

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Bayesian isotopic mixing model, our unprecedented isotopic data measured in lake sediments

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revealed their efficiency to quantitatively decipher between different mining-related sources of

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PAHs in the AOS region.

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EXPERIMENTAL SECTION

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Study site and sampling. The study site (58.391°N, -111.445°W) is a small (800 m long and

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250 to 450 m wide), shallow (maximum depth of 1.7 m) perched lake located in the Athabasca

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sector of the PAD unofficially named PAD23.25 This lake is situated 5 km southeast of the

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Athabasca River and ~ 150 km northeast and downstream of the main operations center.1-3

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PAD23 is known to have recorded sediment material deposition from the Athabasca River 4 ACS Paragon Plus Environment

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watershed through periodical flooding prior to a meander “cut off” on the river in 1972 (Text S1,

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Fig. 1b).26-27 Following this event, a drastic reduction of these flood-induced fluvial inputs was

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observed.26-27 The prevailing annual winds along the Athabasca River from the heart of main

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mining operation to the PAD (Fig.1) are from the southwest and southeast (i.e., over 50% of the

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time for all the seasons of the year) (http://windatlas.ca/en/maps.php), potentially bringing

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material from the heart of the main mining operations to the PAD. The prevailing wind

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directions are also supported by the air parcel transport analysis model results reported by Cho et

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al.8 showing that air parcels generally travel further from the main mining operations center on a

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N-S direction rather than on a W-E direction.

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Sampling was carried out on a single day in September 2010 using a custom-built raft

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transported by helicopter. Gravity cores were collected from the sides of the raft at a spacing of

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~1 m and following a grid pattern in the deepest parts of the lake. Seven sediment cores were

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collected and sub-sampled at 1 cm intervals and all layers from the same depth intervals were

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pooled together resulting in an amalgamated core of 30 cm length. Combining layers from seven

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cores was necessary in order to obtain a sufficient amount of material required for compound-

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specific δ13C and δ2H analyses. The logistics of collecting replicate amalgamated cores to carry

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out additional CSIA measurements would have required a significantly greater amount of

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sediment material than the sampling strategy could support. Future work will examine alternative

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approaches to collecting large numbers of sediment cores needed for dual-CSIA in remote areas

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such as the PAD.

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Analysis of PAHs. Approximately 10 g of freeze-dried sediment from each sediment interval

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were spiked with m-terphenyl and 9,10-dihydrophenanthrene (Sigma-Aldrich, Oakville, ON, 5 ACS Paragon Plus Environment


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Canada) as surrogate standards and extracted using a Microwave Accelerated Reaction System

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(MARS, CEM Corporation, Matthews, NC, USA). The extracts were then filtered using pre-

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combusted (450oC for 4 h) glass fibre filters and elemental sulfur was removed by addition of

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activated copper. The samples were then saponified, liquid/liquid extracted using hexane, and

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separated into three fractions (F1, hexane; F2, hexane:dichloromethane, 1:1; F3, methanol) by

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silica gel chromatography. The aromatic fraction containing PAHs (F2) was evaporated down to

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1 mL and spiked with o-terphenyl prior to concentration determination using a gas

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chromatograph mass spectrometer (GC-MS) system (MSD 5975C and GC 7890A; Agilent

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Technologies, Santa Clara, CA, USA) equipped with an Agilent J&W DB-5 column (30 m ×

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0.25 mm × 0.25 µm). The following GC temperature program was used for analysis: 70 °C (hold

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2 min), increase to 290 °C at a rate of 8 °C/min (hold 8 min), and increase to 310 °C at a rate of

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10 °C/min (hold 10 min). PAHs were analyzed in selected ion monitoring (SIM) mode, and

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concentrations were determined using external standards (Text S2). Concentrations of alkylated

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PAHs (Table S1) were determined using the closest external standard available and identified

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with at least two different ions. The sum of the alkylated PAH groups (C1−C4

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phenanthrene/anthracene, C1−C4 fluoranthene/pyrene, C1−C4 dibenzothiophene, C1−C4 fluorene,

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C1−C4 chrysene) are reported as ΣPAHalkyl, and the sum of the parent PAH groups (16 EPA

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PAHs minus naphthalene, plus dibenzothiophene) as ΣPAHparent. Retene, although an alkylated

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PAH (1-methyl-7-isopropyl phenanthrene), is not reported as part of the ΣPAHalkyl group. Further

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information on PAH analysis is found in the Supporting Information (Text S2, Table S1)

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Compound specific carbon and hydrogen analysis. Compound-specific stable carbon isotope

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analysis was carried out using a PRISM-III isotope ratio mass spectrometer (IRMS) system 6 ACS Paragon Plus Environment

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(Fisons Instruments, Middlewich, United Kingdom) equipped with a GC (HP 5890 Series II,

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Hewlett-Packard, Palo Alto, CA, USA) and a TG-5MS column (30 m × 0.32 mm × 0.25 µm;

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Thermo Fisher Scientific, Waltham, MA, USA). The combustion reactor was packed with

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Cu/Ni/Pt wires and kept at 940°C. The same GC oven temperature program previously described

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for GC-MS analysis was used for δ13C analyses. δ13C values were analyzed using CO2 calibrated

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against international carbonate standards (NBS 18, NBS 19 and LSVEC).

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Compound-specific stable hydrogen isotope analysis was performed using a Deltaplus XL

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IRMS system (Thermo-Finnigan, Bremen, Germany) equipped with an Agilent GC 6890 and a

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TG-5MS column (60 m × 0.32 mm × 0.25 µm). The pyrolysis reactor was an empty ceramic tube

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kept at 1450°C. Since a 60 m GC column was used for δ2H analyses, a slightly different

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temperature program was applied to optimize the chromatographic separation of compounds: 70

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°C (hold 2 min), increase to 250 °C at a rate of 10 °C/min, increase to 290 °C at a rate of 6

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°C/min (hold 10 min) and increase to 310 °C at a rate of 10 °C/min (hold 10 min). δ2H values

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were analyzed using commercial H2 isotopic reference gas (Oztech Trading Corporation,

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Safford, AZ, USA) calibrated against international standards (VSMOW). Prior to δ2H analysis,

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black carbon conditioning was necessary to inactivate the ceramic tube in order to avoid

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hydrogen exchange with the ceramic inner wall. This conditioning was performed by passing

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pure methane in back flush for 5 sec followed by a standby period of 30 min. Further information

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on CSIA calibration and post-analysis data processing is provided in the Supporting Information

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(Text S3).

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University of Georgia’s Center of Applied Isotope Studies in order to characterize the relative

C analysis. The radiocarbon contents of solvent-extractable OM (SEOM) were measured at the

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amount of AOS bitumen in the sediment. Approximately 2 g of sediment from seven different 1

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cm sediment intervals spanning the entire length of the core were extracted twice (1st extraction:

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hexane:acetone 1:1, 2nd extraction dichloromethane:methanol 9:1) using the MARS system

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described above. The SEOM extracts were then filtered using pre-combusted (450oC for 4 h)

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glass fibre filters and elemental sulfur was removed by addition of activated copper. The SEOM

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extracts dissolved in dichloromethane were transferred to quartz combustion tubes, evaporated

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under a flow of ultra-pure N2 at room temperature, evacuated, sealed off and combusted at 900°C

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in the presence of CuO. Following combustion, the resulting carbon dioxide was cryogenically

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purified from the other reaction products and catalytically converted to graphite following the

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procedure of Vogel et al.28 Graphite

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accelerator mass spectrometer (National Electrostatics Corporation, Middleton, WI, USA). The

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sample ratios were compared to the ratio of Oxalic Acid I (NBS SRM 4990) and reported in

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∆14C notation normalized to δ13C following international convention.29 The associated

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uncertainty (accuracy and precision) for ∆14C measurements was ± 10‰.

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C/13C ratios were measured using the CAIS 0.5 MeV

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TOC, δ13C-TOC, and C/N ratios. The percentages of total organic carbon (TOC) and δ13C-

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TOC in homogenized sediment samples decarbonated with H2SO3 were determined using an

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elemental analyzer (Carlo Erba NC 2500, CE Instruments, Milan, Italy) coupled to a PRISM-III

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IRMS. The total nitrogen contents in homogenized sediment samples were determined using an

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elemental analyzer (Costech 4010, Costech Analytical Technologies, Valencia, CA, USA)

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coupled to a Delta V IRMS (Thermo-Electron Corporation, Bremen, Germany). Atomic C/N

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ratios were determined by dividing the % TOC by % total nitrogen and multiplying this value by


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the ratio of the atomic weight of nitrogen on carbon. Further information on % TOC, % total

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nitrogen and δ13C-TOC calibration is provided in the Supporting Information (Text S4).

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Sediment dating. Measurements of 210Pb, 137Cs and 226Ra were carried out on subsamples taken

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from the amalgamated core for sediment dating purposes. The activity of

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the depth in the sediment and becomes undistinguishable from the low and nearly invariant

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activity of

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Results revealed that the sedimentation rate (ω) ranges between 201 and 317 g m-2 yr-1 and that

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the sediment age increases almost linearly with cumulative dry mass (Fig. S1b). The peak of

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137

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the time period where the atmospheric fallout of

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discrepancy is likely due to the post-deposition mobility of

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lake sediments.30-34 Further information on sediment dating is provided in the Supporting

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Information (Text S5).

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210

Pb decreases with

Ra at a cumulative sediment mass of 3.32 g cm-2 at 29.5 cm depth (Fig. S1a).

Cs activity corresponds to a 210Pb age of circa 1982 rather than in sediments deposited during 137

Cs reached a maximum (1963). Such a 137

Cs as has often been observed in

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RESULTS AND DISCUSSION

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Organic matter parameters. The carbon isotope profiles of OM (Fig. 2a) showed relatively

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depleted and stable values from 26.5 to 9.5 cm for δ13C-TOC (-27.9 ±0.2) and between 26.5 to

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17.5 cm for ∆14C-SEOM (-156 ±26‰), followed by subsequent increases to the top of the core

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(i.e., -25.7‰ and -38‰ for δ13C-TOC and ∆14C-SEOM, respectively, at the sediment surface).

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These OM isotopic records suggest a change in the principal OM sources between the bottom

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and the top of the core. Although more susceptible to interpretation bias induced by potential

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modification by sediment biogeochemical processes post-deposition, the TOC and C/N ratios 9 ACS Paragon Plus Environment


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showed a similar source change with lower TOC and more variable C/N ratio at the bottom of

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the core and higher TOC and slightly decreasing C/N ratio at the top of the core (Fig. 2b). The

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shifts in OM sources deciphered from these proxies are in agreement with the hydrodynamic

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changes reported for PAD23 and occurring in 1972 due to the “Athabasca River cut-off” (Fig.

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1b).26-27 Before 1972, PAD23 was periodically flooded by the Athabasca River, whose waters

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transported sediments containing low TOC but relatively high levels of eroded bitumen.26 The

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lower TOC, δ13C-TOC (i.e., δ13C ~ -30‰ for AOS bulk bitumen and aromatic fractions)3, 35 and

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∆14C-SEOM values closer to the radiocarbon dead value of -1000‰ for AOS bitumen which is

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millions of years old at the bottom part of the core can thus be explained by these flooding

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episodes. Following the 1972 meander “cut-off”, a less flood-susceptible period is confirmed by

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the observation of an increase in internal productivity illustrated by a ~3‰ enrichment in δ13C-

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TOC, a decrease in C/N ratio, an increase in TOC, and a decrease in fossil OM of fluvial origin

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as reflected by an enrichment in ∆14C-SEOM. Although all the described OM parameters’

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profiles are not synchronous with regards to their point of inflexion depth, they illustrate a

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hydrodynamic change between the bottom and the top of the sediment record. Thus, the effect of

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the 1972 “cut-off” on PAD23 hydrodynamics history is recorded in our sediment core,

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confirming a transition to a lake receiving a relatively lower proportion of fluvial inputs over the

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past ~40 years as already described by Wolfe et al.27 using biogenic proxies.

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PAH concentrations and diagnostic ratios. Concentrations of parent (∑PAHparent) and

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alkylated (∑PAHalkyl) PAHs ranged between 97 and 217 ng g-1 and 88 and 195 ng g-1 (Fig. 2c),

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respectively, and were similar to those previously reported by Hall et al.26 at the same site. The

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levels of PAHs did not exceed the Canadian Council of Ministers of the Environment (CCME)


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sediment quality guidelines36 (Table S2) and were comparable to those reported for headwater

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lakes situated within around 50 km of the main area of AOS mining operations.2-3

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Retene (1-methyl-7-isopropyl phenanthrene) is an alkylated PAH that is often used as an

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indicator for softwood combustion.37 Concentrations of retene in PAD23 were relatively high

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(Fig. 2d) and co-varied with those of unsubstituted PAHs as observed in both total (Fig. 2c) and

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individual PAH profiles (e.g., phenanthrene; Fig. 2d), suggesting a forest fire component to

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parent PAHs over the past 100 years. Several peaks in the diagnostic ratio retene to phenanthrene

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(Fig. 2e) coincided with peaks in retene and phenanthrene concentrations (i.e., recorded between

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14.5 and 6.5 cm; Fig. 2d) following the “cut-off”, pointing to a higher relative contribution of

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forest fire-derived PAHs between the early 1970s and the late 1990s. Although both

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phenanthrene and retene concentrations increased slightly from 4.5 cm to the top of the core (Fig

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2d), the marked decrease in retene to phenanthrene ratios (Fig. 2e) over the same sediment

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interval suggests that a proportion of the recent phenanthrene input to the lake is related to a

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source other than wildfires. Other diagnostic ratios (i.e., fluoranthene/(fluoranthene+pyrene) and

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indeno[1,2,3-cd]pyrene/(indeno[1,2,3-cd]pyrene+benzo[ghi]perylene),6 Fig. S2) confirmed the

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importance of forest fire inputs as a source of PAHs by showing excursions towards pyrogenic

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values over the last three decades of the 20th century and also pointed to a change in PAH source

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distributions toward the top of the core (Text S6).

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Dual-CSIA. Carbon and hydrogen isotope values of phenanthrene (δ13C-phe and δ2H-phe)

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ranged between -31.6 to -28.2‰ and -154.8 to -96.9‰, respectively (Fig. 2f), and are all lower

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than the values reported for specific fossil fuel sources.23 Both δ13C-phe and δ2H-phe values vary

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as a function of depth in the sediments (Fig. 2f). Values of δ13C-phe progressively increased 11 ACS Paragon Plus Environment


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from -30.5 ±0.2‰ at the bottom of the core to -28.2 ±0.4‰ at 13 cm depth, and then

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subsequently decreased toward the sediment surface to -31.6 ±0.4‰. In contrast, the values of

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δ2H-phe increased more or less regularly from -154.8 ±3.7‰ at the bottom of the core to -96.9

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±1.0‰ at the sediment surface.

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It is not likely that in situ biodegradation or photodegradation have modified carbon and

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hydrogen isotope ratios of phenanthrene at our sampling site. For biodegradation, significant

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isotope fractionation of PAHs resulting in a progressive 13C-enrichment in the residual substrate

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has thus far not been detected for δ13C values38 or has only been reported for 2-ringed

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naphthalene in controlled laboratory experiments for both carbon and hydrogen isotopes.39-40

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Furthermore, the efficiency of PAH biodegradation in sediments has been found to be inversely

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correlated with OM content, likely due to a strong sequestration of the PAHs by the OM.41-42 The

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high TOC contents (i.e., 16 to 28%) measured in PAD23, in conjunction with the lack of

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significant correlations between both δ13C-phe or δ2H-phe values and phenanthrene

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concentrations (Fig. S3) suggest that the OM content has inhibited their biodegradation within

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the sediment. As for photochemical degradation, although a significant

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approximately 2‰ has been observed in three-ringed anthracene,43 no information exists about

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hydrogen isotopic fractionation in PAHs during this process. However, the depletion rather than

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enrichment in

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between δ2H-phe and phenanthrene concentrations (Fig. S3), indicate that photodegradation (if

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occurring) did not significantly fractionate the carbon and hydrogen isotopes of phenanthrene in

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PAD23. The variation in δ13C-phe and δ2H-phe values observed across the core is therefore

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interpreted as due to source changes rather than microbial or photochemical fractionation

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occurring during degradation.

13

13

C enrichment of

C observed at the top of the core (Fig. 2f), in conjunction with no correlation


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Various potential sources (i.e., AOS bitumen, AOS petroleum coke dust, forest fire

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emissions, gasoline soot, diesel soot and coal particulates; Table 1) were considered for the

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phenanthrene deposited in this particular environmental system (Fig. 2d). While results from a

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multimedia fate model suggested that evaporative emissions from tailings ponds may also be a

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significant source of PAHs in the AOS region,4 field observations thus far point to a minor role

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for this process.17,

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considered as a potential source for PAHs to PAD23.

44

Consequently, evaporative emissions from tailings ponds were not

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The dual isotopic signature of the aromatic fraction of AOS bitumen was analyzed in two

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different samples and pooled with the values reported in the literature.45 The dual isotopic

281

signature of phenanthrene was analyzed in two samples of industrial AOS petcoke from two

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different locations. Carbon9 and hydrogen (this study) isotope signatures for phenanthrene

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determined in sedimentary intervals considerably pre-dating the large scale development of the

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oil sands in several headwater lakes in northwest Saskatchewan are representative of regional

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forest fire emissions. The isotopic signatures of phenanthrene for coal, gasoline and diesel soot

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were taken from the literature.13, 23, 46-49

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Comparison of the δ13C-phe and δ2H-phe values measured in the sediment samples to the

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isotopic signatures of the potential main environmental sources in this region (Table 1) reveals a

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logical association with the hydrodynamic historical reconstruction for PAD23. Because PAD23

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was flood-susceptible prior to the “Athabasca River cut-off” (1972), a dual isotopic signature

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close to that of AOS bitumen was recorded below 14.5 cm depth, illustrating the predominance

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of a single source input (i.e., bitumen) transported and deposited via flooding events. Following

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the “cut-off”, a significant decrease in flooding events resulted in a lower proportion of bitumen

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input, leading to a dual isotopic signature reflecting a more complex mixture of sources (i.e., 13 ACS Paragon Plus Environment


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AOS bitumen and forest fires) recorded between 14.5 and 9.5 cm depth. In the top 9 cm

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corresponding to the last 30 years, δ2H-phe values became heavier than the signature for AOS

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bitumen, and increased towards the signature of forest fires (Table 1). However, as the δ13C-phe

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value for forest fires (-26.7 ±0.3‰) is enriched compared to the mean of the top 5 cm (-30.6

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±0.8‰), a third source needs to be taken into account to explain this recent shift in both δ13C-phe

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and δ2H-phe.

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Gasoline and diesel combustion particulates originating from the Fort McMurray

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urbanized area and the heavy haulers used on mining sites can be ruled out since the up-core

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shift in δ13C–phe towards more depleted values is inconsistent with the relatively enriched values

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reported for these sources (i.e., -26.5‰ and -25.3, respectively, Table 1).13, 23, 46 Based on a

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global range in δ13C values between -22.6 and -28.3‰,47-49 coal can also be ruled out as a

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potential source for the more depleted phenanthrene signatures found at the top of the core.

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Petcoke emissions are produced by the AOS upgrading process and its subsequent

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handling.50 Petcoke fine particles (average diameter 3.3 ±1.9 µm) derived from delayed coking

309

technology can contain

310

Environmental Protection Agency.51 A phenanthrene concentration of approximately 2 µg g-1 in

311

the two samples analyzed in this study confirmed that high levels of PAHs are also present in

312

AOS petcoke. This upgrading by-product is used as a capping material over tailings areas,

313

stockpiled, or reused as a fuel and catalyst for the coking process.52 Under mechanical stress

314

conditions (e.g., meteorological erosion, weathering and erosion by the heavy haulers), petcoke

315

dust particulates smaller than 2.5 µm in diameter (i.e., PM2.5) could potentially undergo long-

316

range atmospheric transport.53 The petcoke isotopic signatures (δ13C-phe = -32.6 ±0.3‰ and

317

δ2H-phe = -48.5 ±3.8‰; Table 1) are significantly different from AOS bitumen due to the

up to ~ 80 µg g-1 of the 16 priority PAHs listed by the U.S.


Page 15 of 29


318

fractionation involved during the upgrading process. The heavier δ2H-phe in petcoke can be

319

explained by the mechanisms of PAH formation involving dehydration induced by

320

dehydrocyclization reactions, during which lighter hydrogen isotopes are preferentially removed

321

from the newly formed PAH ring structures.23 The slightly depleted petcoke δ13C-phe signature

322

compared to AOS bitumen is attributed to a kinetic isotope effect associated with carbon-carbon

323

bond formation, cyclization and/or ring fusion during the production of PAHs from primary

324

volatiles within the coking units.54 As the dual isotopic signature of AOS petcoke fits with the

325

concurrent depletion in δ13C-phe and enrichment in δ2H-phe recorded in the upper sediment

326

samples (Fig. 2f), petcoke was selected as the most likely third source of our mixing system

327

responsible for the up-core shift observed over the last two decades.

328

329

Isotopic mixing modeling. To quantitatively estimate the contribution of the three most

330

probable sources of phenanthrene (i.e., AOS bitumen, AOS petcoke and forest fires) at our study

331

site, we applied a Bayesian isotopic mixing model, SIAR.55 Unlike regular multivariate linear

332

mixing models, Bayesian-based mixing models allow the propagation of the intra-source

333

variability specific to each isotopic ratio through the model. This variability in turn allows a

334

refined estimation of the sources’ contributions associated with credibility intervals (CI), which

335

avoid over- or underestimation by reporting only the possible solutions with tolerance intervals.

336

In a first step, as recommended by Phillips et al.,56 we simulated all the possible mixing polygons

337

according to the isotopic distributions of the selected sources (Fig. 3a)57 which validated the

338

subsequent application of the Bayesian isotopic mixing model (Text S7). This simulation allows

339

us to test the ability of each mixing polygon to establish a mass balance. In a second step, SIAR

340

was applied with 200,000 iterations on the three sources’ isotopic distributions (i.e., including 15 ACS Paragon Plus Environment


Page 16 of 29

341

standard deviation encompassing both analytical precision, accuracy and intra-source isotopic

342

variability, Fig. 2, Table 1). Using the modeled contributions of each of the phenanthrene sources

343

(p) determined for every sample analyzed, the phenanthrene concentration and the 210Pb derived

344

sedimentation rates (ω), the source-specific deposition fluxes of phenanthrene (Jphe; Fig. 3b, c, d)

345

at a given date were calculated with the following equation :

346

J phe = ω × p × [ phe]

347

The model was able to explain the evolution of the sources’ contributions with relatively

348

narrow 95% CIs, lending confidence to the sources selection for this particular environmental

349

system (Fig. 3). Forest fire-derived phenanthrene fluxes were below 1.5 µg m-2 yr-1 (i.e., upper

350

limit of the 95% CI) from the early 1930s to the mid-1960s, increased up to 5.4 µg m-2 yr-1

351

during the 1970s to the 1990s, and then decreased to values lower than 0.9 µg m-2 yr-1 in ~2010.

352

These trends support the interpretation of the retene and retene/phenanthrene profiles shown in

353

Figures 2d and 2e. AOS petcoke-derived phenanthrene fluxes were below 0.09 µg m-2 yr-1 from

354

the early 1930s to the late 1970s, then increased to values between 4.1 and 5.7 µg m-2 yr-1

355

(CI=95%) in ~2010. The increase in the fluxes of petcoke-derived phenanthrene coincides with

356

the growth in Alberta’s petcoke inventory during this period,52 providing qualitative support for

357

the modeled source contributions (Fig. 3b). The calculated fluxes of AOS bitumen-derived

358

phenanthrene ranged between 5.6 and 11.0 µg m-2 yr-1 from the 1930s to the 1990s and then

359

decreased by about 25% in the last two decades.

360

We acknowledge that the sole sample analyzed for the forest fire source δ2H-phe

361

signature may under-represent the intra-source isotopic variability; therefore, after simulating the

362

associated mixing region (Fig S4a), we also ran the model by increasing the range of variability 16 ACS Paragon Plus Environment

Page 17 of 29


363

in the forest fire δ2H-phe signature by ± 20‰ (Fig. S4). Although the credibility intervals were

364

slightly broader, the trends were conserved and the up-core increase in the petcoke contribution

365

to PAD23 (i.e., up to 4.1-5.8 µg m-2 yr-1 in 2010; CI 95%) was still observed (Fig. S4c).

366

The model output of Isosource,58 a non-Bayesian mixing model, showed similar source

367

contribution trends (Fig. S5) and gave solutions that were all within the credibility intervals

368

resolved by SIAR. Further information on the model parameterization and output is provided in

369

Text S8. The close agreement between both models, in conjunction with the hydrodynamic

370

history of this lake, bring further confidence in the ranges of source-specific fluxes reported here

371

and strengthens the argument for an increasing input of petcoke particulates to this lake to a

372

minimum estimate of 4.1 µg m-2 yr-1 of phenanthrene in ~2010.

373

Although PAD23 now receives less fluvial inputs,26-27 the occurrence of AOS bitumen-

374

derived phenanthrene post “cut-off” (Fig. 3) suggests that intermittent flooding episodes may

375

still deliver fluvial material to this lake. It is therefore possible that petcoke particles, following

376

localized deposition to the snowpack near AOS mining operations, for instance,8 are also carried

377

to the PAD via the Athabasca River. On the other hand, AOS bitumen-derived phenanthrene in

378

PAD23 post “cut-off” sediments may also be attributed to fugitive dust associated with open pit

379

mining activities.2-3, 7 Whatever the dominant transport mechanism(s), the isotopic evidence for

380

petcoke at our study site implies a long-range transport (i.e., > 100 km) of anthropogenic,

381

mining-related PAHs to the PAD.

382 383

An under-considered source of AOS mining-related PAHs: petcoke. We provide here the

384

first historical reconstruction of a quantitative PAH source apportionment using dual-CSIA. With

385

the use of only δ13C signatures, it was previously hypothesized that AOS fugitive dust was the 17 ACS Paragon Plus Environment


Page 18 of 29

386

principal source for mining-related PAHs to lakes located ~50 km south-east of the main center

387

of oil sands mining activities.3 The application of dual-CSIA in this study allowed us to refine

388

the source apportionment by identifying petcoke dust as a likely vehicle for the long-range

389

transport (i.e., > 100 km) of oil sands mining-related PAHs. Although the relatively low PAH

390

concentrations in PAD23 indicate that this input remains small, the continued development and

391

expansion of AOS mining activities may lead to future increases in fluxes of petcoke-derived

392

contaminants. In addition, a recent review by Caruso et al.59 has highlighted exposure to fugitive

393

petcoke dust as a potential environmental concern, and suggested that more research is needed to

394

quantify fugitive emissions from storage piles. As demonstrated here, dual-CSIA provides a

395

powerful tool to identify and quantify petcoke and other potential sources of anthropogenic

396

PAHs in the AOS region. This information, in turn, is essential for developing successful

397

environmental management strategies and practices.

398 399

ASSOCIATED CONTENT

400

Supporting Information

401

Further details on methodology, concentration data for individual PAHs, sediment dating,

402

sediment quality guidelines, PAH diagnostic ratios and isotopic modeling. This material is

403

available free of charge via the Internet at http://pubs.acs.org/.

404 405

AUTHOR INFORMATION

406

Corresponding Author

407

*Tel: 418-654-3721; fax: 418-654-2615; e-mail: [email protected].

408 18 ACS Paragon Plus Environment

Page 19 of 29


409

Notes

410

The authors declare no competing financial interest.

411 412

ACKNOWLEDGMENTS

413

This research was funded by the Earth Sciences Sector of Natural Resources Canada (CORES

414

Project - Coal & Oil sands Resources Environmental Sustainability) under the framework of the

415

Environmental Geosciences Program. We thank Paul Gammon and Lisa Neville for help with

416

fieldwork, Roland Hall, Johan Wiklund and Brent Wolfe for help with site selection and

417

radiometric analyses, Marie-Christine Simard, Hooshang Pakdel and Marc Luzincourt for

418

laboratory assistance, Hussein Wazneh for statistical support, and Alberta Environment and

419

Sustainable Resource Development, McMurray Aviation and Parks Canada for help with

420

fieldwork logistics. Special thanks to our helicopter pilot Don Cleveland (Lakeshore

421

Helicopters). This is Earth Sciences Sector contribution #20140458.

422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439

REFERENCES 1. Kelly, E. N.; Short, J. W.; Schindler, D. W.; Hodson, P. V.; Ma, M.; Kwan, A. K.; Fortin, B. L., Oil sands development contributes polycyclic aromatic compounds to the Athabasca River and its tributaries. Proc. Natl. Acad. Sci. USA 2009, 106 (52), 22346-22351. 2. Kurek, J.; Kirk, J. L.; Muir, D. C. G.; Wang, X.; Evans, M. S.; Smol, J. P., Legacy of a half century of Athabasca oil sands development recorded by lake ecosystems. Proc. Natl. Acad. Sci. USA 2013, 110 (5), 1761-1766. 3. Jautzy, J.; Ahad, J. M. E.; Gobeil, C.; Savard, M. M., Century-long source apportionment of PAHs in Athabasca oil sands region lakes using diagnostic ratios and compound-specific carbon isotope signatures. Environ. Sci. Technol. 2013, 47 (12), 6155-6163. 4. Parajulee, A.; Wania, F., Evaluating officially reported polycyclic aromatic hydrocarbon emissions in the Athabasca oil sands region with a multimedia fate model. Proc. Natl. Acad. Sci. USA 2014, 111 (9), 3344–3349. 5. Yang, C.; Wang, Z.; Yang, Z.; Hollebone, B.; Brown, C. E.; Landriault, M.; Fieldhouse, B., Chemical fingerprints of Alberta oil sands and related petroleum products. Environ. Forensics 2011, 12 (2), 173-188.



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6. Yunker, M. B.; Macdonald, R. W.; Vingarzan, R.; Mitchell, R. H.; Goyette, D.; Sylvestre, S., PAHs in the Fraser River basin: a critical appraisal of PAH ratios as indicators of PAH source and composition. Org. Geochem. 2002, 33 (4), 489-515. 7. Studabaker, W. B.; Krupa, S.; Jayanty, R. K. M.; Raymer, J. H., Measurement of Polynuclear Aromatic Hydrocarbons (PAHs) in Epiphytic Lichens for Receptor Modeling in the Athabasca Oil Sands Region (AOSR): A Pilot Study. In Alberta Oil Sands : Energy, Industry and the Environment, Kevin, E. P., Ed. Elsevier: 2012; Vol. 11, pp 391-425. 8. Cho, S.; Sharma, K.; Brassard, B. W.; Hazewinkel, R., Polycyclic aromatic hydrocarbon deposition in the snowpack of the Athabasca oil sands region of Alberta, Canada. Water Air Soil Pollut. 2014, 225 (5), 1-16. 9. Ahad, J. M. E.; Jautzy, J.; Cumming, B. F.; Das, B.; Kingsbury, M.; Laird, K. R.; Sanei, H., Sources of polycyclic aromatic hydrocarbons (PAHs) to northwestern Saskatchewan lakes east of the Athabasca oil sands. Org. Geochem. 2015, (80), 35-45. 10. Keiluweit, M.; Kleber, M.; Sparrow, M. A.; Simoneit, B. R. T.; Prahl, F. G., Solvent-extractable polycyclic aromatic hydrocarbons in biochar: Influence of pyrolysis temperature and feedstock. Environ. Sci. Technol. 2012, 46 (17), 9333-9341. 11. Bates, T. S.; Carpenter, R., Organo-sulfur compounds in sediments of the Puget Sound basin. Geochim. Cosmochim. Ac. 1979, 43 (8), 1209-1221. 12. Sun, C.; Snape, C. E.; McRae, C.; Fallick, A. E., Resolving coal and petroleum-derived polycyclic aromatic hydrocarbons (PAHs) in some contaminated land samples using compound-specific stable carbon isotope ratio measurements in conjunction with molecular fingerprints. Fuel 2003, 82 (1517), 2017-2023. 13. McRae, C.; Love, G. D.; Murray, I. P.; Snape, C. E.; Fallick, A. E., Potential of gas chromatography isotope ratio mass spectrometry to source polycyclic aromatic hydrocarbon emissions. Anal. Commun. 1996, 33 (9), 331-333. 14. Ballentine, D. C.; Macko, S. A.; Turekian, V. C.; Gilhooly, W. P.; Martincigh, B., Compound specific isotope analysis of fatty acids and polycyclic aromatic hydrocarbons in aerosols: Implications for biomass burning. Org. Geochem. 1996, 25 (1-2), 97-104. 15. Kim, M.; Kennicutt II, M. C.; Qian, Y., Source characterization using compound composition and stable carbon isotope ratio of PAHs in sediments from lakes, harbor, and shipping waterway. Sci. Total Environ. 2008, 389 (2-3), 367-377. 16. Smirnov, A.; Abrajano Jr, T. A.; Stark, A., Distribution and sources of polycyclic aromatic hydrocarbons in the sediments of Lake Erie, Part 1. Spatial distribution, transport, and deposition. Org. Geochem. 1998, 29 (5-7), 1813-1828. 17. Ahad, J. M. E.; Gammon, P. R.; Gobeil, C.; Jautzy, J.; Krupa, S.; Savard, M. M.; Studabaker, W. B., Evaporative emissions from tailings ponds are not likely an important source of airborne PAHs in the Athabasca oil sands region. Proc. Natl. Acad. Sci. USA 2014, 111 (24), E2439. 18. Parajulee, A.; Wania, F., Reply to Ahad et al.: Source apportionment of polycyclic aromatic hydrocarbons in the Athabasca oil sands region is still a work in progress. Proc. Natl. Acad. Sci. USA 2014, 111 (24), E2440. 19. Wang, Z.; Yang, C.; Parrott, J. L.; Frank, R. A.; Yang, Z.; Brown, C. E.; Hollebone, B. P.; Landriault, M.; Fieldhouse, B.; Liu, Y.; Zhang, G.; Hewitt, L. M., Forensic source differentiation of petrogenic, pyrogenic, and biogenic hydrocarbons in Canadian oil sands environmental samples. J. Hazard. Mater. 2014, 271 (0), 166-177. 20. Schindler, D. W., Geoscience of Climate and Energy 12. Water Quality Issues in the Oil Sands Region of the Lower Athabasca River, Alberta. 2013 2013. 21. Galarneau, E.; Hollebone, B. P.; Yang, Z.; Schuster, J., Preliminary measurement-based estimates of PAH emissions from oil sands tailings ponds. Atmos. Environ. 2014, 97 (0), 332-335. 22. Jautzy, J. J.; Ahad, J. M. E.; Hall, R. I.; Wiklund, J. A.; Wolfe, B. B.; Gobeil, C.; Savard, M. M., Source apportionment of background PAHs in the Peace-Athabasca Delta (Alberta, Canada) using molecular level radiocarbon analysis. Environ. Sci. Technol. 2015, 49 (15), 9056-9063. 20 ACS Paragon Plus Environment

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23. Sun, C.; Cooper, M.; Snape, C. E., Use of compound-specific δ13C and δD stable isotope measurements as an aid in the source apportionment of polyaromatic hydrocarbons. Rapid Commun. Mass Sp. 2003, 17 (23), 2611-2613. 24. Wang, Y.; Huang, Y.; Huckins, J. N.; Petty, J. D., Compound-specific carbon and hydrogen isotope analysis of sub-parts per billion level waterborne petroleum hydrocarbons. Environ. Sci. Technol. 2004, 38 (13), 3689-3697. 25. Wolfe, B. B.; Hall, R. I.; Edwards, T. W. D.; Johnston, J. W., Developing temporal hydroecological perspectives to inform stewardship of a northern floodplain landscape subject to multiple stressors: Paleolimnological investigations of the Peace-Athabasca Delta. Environ. Rev. 2012, 20 (3), 191-210. 26. Hall, R. I.; Wolfe, B. B.; Wiklund, J. A.; Edwards, T. W. D.; Farwell, A. J.; Dixon, D. G., Has Alberta oil sands development altered delivery of polycyclic aromatic compounds to the Peace-Athabasca Delta? PLoS ONE 2012, 7 (9), e46089. 27. Wolfe, B. B.; Hall, R. I.; Edwards, T. W. D.; Vardy, S. R.; Falcone, M. D.; Sjunneskog, C.; Sylvestre, F.; McGowan, S.; Leavitt, P. R.; van Driel, P., Hydroecological responses of the Athabasca Delta, Canada, to changes in river flow and climate during the 20th century. Ecohydrology 2008, 1 (2), 131-148. 28. Vogel, J. S.; Southon, J. R.; Nelson, D. E.; Brown, T. A., Performance of catalytically condensed carbon for use in accelerator mass spectrometry. Nucl. Instrum. Meth. B 1984, 5 (2), 289-293. 29. Stuiver, M.; Polach, H. A., Discussion: Reporting of 14C data. Radiocarbon 1977, 19 (3), 355. 30. Smith, J. N.; Ellis, K. M.; Nelson, D. M., Time-dependent modeling of fallout radionuclide transport in a drainage basin: Significance of "slow" erosional and "fast" hydrological components. Chem. Geol. 1987, 63 (1-2), 157-180. 31. Smith, J. T.; Comans, R. N. J.; Ireland, D. G.; Nolan, L.; Hilton, J., Experimental and in situ study of radiocaesium transfer across the sediment-water interface and mobility in lake sediments. Appl. Geochem. 2000, 15 (6), 833-848. 32. Davis, R. B.; Hess, C. T.; Norton, S. A.; Hanson, D. W.; Hoagland, K. D.; Anderson, D. S., 137Cs 210 and Pb dating of sediments from soft-water lakes in New England (U.S.A.) and Scandinavia, a failure of 137Cs dating. Chem. Geol. 1984, 44 (1-3), 151-185. 33. Comans, R. N. J.; Middelburg, J. J.; Zonderhuis, J.; Woittiez, J. R. W.; De Lange, G. J.; Das, H. A.; Van Der Weijden, C. H., Mobilization of radiocaesium in pore water of lake sediments. Nature 1989, 339 (6223), 367-369. 34. Klaminder, J.; Appleby, P.; Crook, P.; Renberg, I., Post-deposition diffusion of 137Cs in lake sediment: Implications for radiocaesium dating. Sedimentology 2012, 59 (7), 2259-2267. 35. Farwell, A. J.; Nero, V.; Ganshorn, K.; Leonhardt, C.; Ciborowski, J.; MacKinnon, M.; Dixon, D. G., The use of stable isotopes (13C/12C and 15N/14N) to trace exposure to oil sands processed material in the Alberta oil sands region. J. Toxicol. Environ. Health - Part A: Current Issues 2009, 72 (6), 385-396. 36. Canadian Council of Ministers of the Environment (CCME) Sediment Quality Guidelines, Environment Canada, 2002. http://st-ts.ccme.ca/?chems=all&chapters=3 (accessed September 25, 2014). 37. Ramdahl, T., Retene - a molecular marker of wood combustion in ambient air. Nature 1983, 306 (5943), 580-582. 38. Mazeas, L.; Budzinski, H.; Raymond, N., Absence of stable carbon isotope fractionation of saturated and polycyclic aromatic hydrocarbons during aerobic bacterial biodegradation. Org. Geochem. 2002, 33 (11), 1259-1272. 39. Bergmann, F. D.; Abu Laban, N. M. F. H.; Meyer, A. H.; Elsner, M.; Meckenstock, R. U., Dual (C, H) isotope fractionation in anaerobic low molecular weight (poly)aromatic hydrocarbon (PAH) degradation: Potential for field studies and mechanistic implications. Environ. Sci. Technol. 2011, 45 (16), 6947-6953. 40. Morasch, B.; Richnow, H. H.; Schink, B.; Vieth, A.; Meckenstock, R. U., Carbon and hydrogen stable isotope fractionation during aerobic bacterial degradation of aromatic hydrocarbons. Appl. Environ. Microbiol. 2002, 68 (10), 5191-5194. 21 ACS Paragon Plus Environment


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41. Hinga, K. R., Degradation rates of low molecular weight PAH correlate with sediment TOC in marine subtidal sediments. Mar. Pollut. Bull. 2003, 46 (4), 466-474. 42. Wang, Z.; Liu, Z.; Xu, K.; Mayer, L. M.; Zhang, Z.; Kolker, A. S.; Wu, W., Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico. Geochem. Trans. 2014, 15 (1), 2. 43. O'Malley, V. P.; Abrajano Jr, T. A.; Hellou, J., Determination of the 13C/12C ratios of individual PAH from environmental samples: can PAH sources be apportioned? Org. Geochem. 1994, 21 (6-7), 809822. 44. Hsu, Y.-M.; Harner, T.; Li, H.; Fellin, P., PAH measurements in air in the Athabasca oil sands region. Environ. Sci. Technol. 2015, 49 (9), 5584-5592. 45. Balliache, N. I. M. Isotopic and molecular studies of biodegraded oils and the development of chemical proxies for monitoring in situ upgrading of bitumen. Ph.D. Dissertation, University of Calgary, Calgary, AB, 2011. 46. Okuda, T.; Takada, H.; Naraoka, H., Thermodynamic behavior of stable carbon isotopic compositions of individual polycyclic aromatic hydrocarbons derived from automobiles. Polycycl. Aromat. Compd. 2003, 23 (2), 219-236. 47. Singh, P. K.; Singh, M. P.; Prachiti, P. K.; Kalpana, M. S.; Manikyamba, C.; Lakshminarayana, G.; Singh, A. K.; Naik, A. S., Petrographic characteristics and carbon isotopic composition of Permian coal: Implications on depositional environment of Sattupalli coalfield, Godavari Valley, India. Int. J. Coal Geol. 2012, 90-91, 34-42. 48. Kotarba, M. J.; Clayton, J. L., A stable carbon isotope and biological marker study of Polish bituminous coals and carbonaceous shales. Int. J. Coal Geol. 2003, 55 (2–4), 73-94. 49. Bechtel, A.; Gruber, W.; Sachsenhofer, R. F.; Gratzer, R.; Püttmann, W., Organic geochemical and stable carbon isotopic investigation of coals formed in low-lying and raised mires within the Eastern Alps (Austria). Org. Geochem. 2001, 32 (11), 1289-1310. 50. Jang, H.; Etsell, T. H., Mineralogy and phase transition of oil sands coke ash. Fuel 2006, 85 (1011), 1526-1534. 51. The American Petroleum Institute, Petroleum coke category analysis and hazard characterization., US Environmental Protection Agency. 2007. 52. ERCB Alberta’s Energy Reserves 2012 and Supply/Demand Outlook 2013-2022. http://www.aer.ca/documents/sts/ST98/ST98-2013.pdf (accessed November 18, 2014). 53. Perry, K. D.; Cahill, T. A.; Eldred, R. A.; Dutcher, D. D.; Gill, T. E., Long-range transport of North African dust to the eastern United States. J. Geophys Res-Atmos 1997, 102 (10), 11225-11238. 54. McRae, C.; Snape, C. E.; Fallick, A. E., Variations in the stable isotope ratios of specific aromatic and aliphatic hydrocarbons from coal conversion processes. Analyst 1998, 123 (7), 1519-1523. 55. Parnell, A. C.; Inger, R.; Bearhop, S.; Jackson, A. L., Source partitioning using stable isotopes: coping with too much variation. PLoS ONE 2010, 5 (3), e9672. 56. Phillips, D. L.; Inger, R.; Bearhop, S.; Jackson, A. L.; Moore, J. W.; Parnell, A. C.; Semmens, B. X.; Ward, E. J., Best practices for use of stable isotope mixing models in food-web studies. Can. J. Zool. 2014, 92 (10), 823-835. 57. Smith, J. A.; Mazumder, D.; Suthers, I. M.; Taylor, M. D., To fit or not to fit: Evaluating stable isotope mixing models using simulated mixing polygons. Methods Ecol. Evol. 2013, 4 (7), 612-618. 58. Phillips, D. L.; Gregg, J. W., Source partitioning using stable isotopes: coping with too many sources. Oecologia 2003, 136 (2), 261-9. 59. Caruso, J. A.; Zhang, K.; Schroeck, N. J.; McCoy, B.; McElmurry, S. P., Petroleum coke in the urban unvironment: a review of potential health effects. Int. J. Environ. Res. Public Health 2015, 12 (6), 6218-6231.

589 590 22 ACS Paragon Plus Environment

Page 23 of 29


591

List of Tables

592 593 594

Table 1. δ13C and δ2H signatures for different potential PAH sources in the PAD.

Source

δ13C (‰) (x̅ ±σ)

δ2H (‰) (x̅ ±σ)

Reference

AOS bitumen†

-30.2 ±0.3‰

4 samples, n=21

-138.5 ±2.5‰

2 samples, n=13

This study & 45

AOS petcoke*

-32.6 ±0.5‰

2 samples, n=5

-48.5 ±3.8‰

2 samples, n=10

This study

Forest fire*

-26.7 ±0.3‰

4 samples, n=10

-96.2 ±1.1‰

1 sample, n=3

This study & 9

Gasoline soot*

-26.5 ±0.5‰

n.a., n≥2

-61.5 ±3.0‰

n.a., n≥2

23

Diesel soot* Coal‡

-25.3 ±2.3‰

2 samples, n≥7

n.a.

n.a.

13, 46

-22.6 to -28.3 ±1.6‰

3 samples, n=43

n.a.

n.a.

47-49

595 596 597 598 599 600

*phenanthrene-specific isotopic signature, †isotopic signature of the aromatic fraction, ‡isotopic signature of the bulk sample. For forest fires, AOS bitumen, AOS petcoke, diesel soot and coal, the number of samples analyzed for each isotope and the number of measurements (i.e., n) are shown. No indication for the number of gasoline soot samples analyzed was provided, and δ2H signatures for diesel soot and coal were not reported (i.e., n.a. = not available).

601

602

603

604

605

606

607

608

609

610 23 ACS Paragon Plus Environment


611

Page 24 of 29

List of Figures

612

613

Figure 1. a) Map of the study area (Northern Alberta, Canada) showing the location of PAD23

614

(red square, 58.39°N, -111.44°W). The gray shapes show the current surficial mining areas; the

615

orange hatched zones illustrate the local urban centers and the star, the heart of the main mining

616

operations.1-3 b) Aerial photograph taken in 1974 of PAD23 showing the 1972 “Athabasca River

617

cut-off”.

618

619

Figure 2. Vertical profiles in the sediments of a) ∆14C-SEOM (filled black circles) and δ13C-

620

TOC (open red circles), b) TOC (filled black circles) and C/N ratio (open red circles), c) the sum

621

of alkylated PAHs minus C1-C4 naphthalene (filled black circles) and the sum of parent PAHs

622

minus naphthalene (open red circles), d) phenanthrene (filled black circles) and retene (open red

623

circles) concentrations, e) retene to phenanthrene diagnostic ratio (filled black circles) and f)

624

δ13C (filled green circles) and δ2H values of phenanthrene (open blue circles), with the error bars

625

integrating both accuracy and precision of the analysis (Text S3). Dates derived from

626

geochronology with the year 1972 corresponding to the “Athabasca River cut-off”.

210

Pb

627

628

Figure 3. a) Simulated isotopic mixing region with the sources’ average isotopic values

629

represented by the white crosses. The numbers indicate the sediment depths of the individual

630

samples. The dashed line represents the 5% probability contour. The colored heat map represents

631

the probabilities of all dual-isotopic signatures that can be explained with the given sources’


Page 25 of 29


632

isotopic distributions. b), c) and d) SIAR-derived historical records of deposition flux of

633

phenanthrene from forest fires, AOS petcoke, and AOS bitumen, respectively. The red, orange

634

and yellow boxes represent the 25, 75 and 95% credibility intervals (CI), respectively. The

635

dotted vertical line represents the date (i.e., 1972) of the “Athabasca River cut-off”. The filled

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black circles in c) show the chronological evolution of the petcoke stock inventory in the AOS

637

region.52



Cover Art 83x47mm (300 x 300 DPI)

ACS Paragon Plus Environment

Page 26 of 29

Page 27 of 29


Figure 1 85x112mm (300 x 300 DPI)



Figure 2 177x84mm (300 x 300 DPI)


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Page 29 of 29


Figure 3 114x46mm (300 x 300 DPI)


Isotopic Evidence for Oil Sands Petroleum Coke in the Peace

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