Geochemical evidence for Alberta Oil Sands contamination in sediments remote to known oil sands deposits in Alberta, Canada

Figures & data

Figure 1. Map of Alberta Oil Sands deposits and surficial sediment sampling locations in relation to surface geology (adapted from Alberta Geological Survey, 2013) and the Alberta Oil Sands deposits (adapted from Auch, 2014).

Table 1. Sample locations and sample types used to characterise Alberta Oil Sands geochemical signatures and identify deposits in surficial sediments.

Sample Name		Sampling Location	Sample Type
Alberta Oil Sands	Amphitheatre Outcrop (A1)	Amphitheatre Outcrop McKay River exposure, Wood Buffalo	Oil sands deposit
	Amphitheatre Outcrop (A2)
	Aurora Mine	Wood Buffalo
	Cold Lake	Cold Lake oil field	Processed bitumen
Surficial Samples	R1	Highway 45, Lamont County	Surficial sediment with visible bitumen
	R2	Highway 14, northwest of Viking, Beaver County	Surficial sediment with no visible bitumen
	R3	Trans-Canada Highway, northwest of Medicine Hat, Cypress County
	M1	Cooking Lake area, Beaver County	Glacial sediment
	M2
	M3
	M4

Table 2. Compounds and parameters used to calculate the diagnostic ratios in Tables 3 and 4.

Diagnostic Ratio	Calculation
Steranes
DiaSt	$C_{27}\beta \alpha (20R+S)/(\mathit{\text{same}}+C_{29}\alpha \alpha \alpha (20R+S)+C_{29}\alpha \beta \beta (20R+S))$
Preg	$(\mathit{\text{diagnane}}+\mathit{\text{pregnane}}+\mathit{\text{methyldiagnane}}+\mathit{\text{methylpregnane}})/$ $(\mathit{\text{same}}+C_{29}\alpha \alpha \alpha (20R+S)+C_{29}\alpha \beta \beta (20R+S))$
St29S/R	$C_{29}(20S)/C_{29}(20R+S)$
St29I/R	$C_{29}\alpha \beta \beta /(C_{29}\alpha \beta \beta +C_{29}\alpha \alpha \alpha )$
Terpanes incl. Hopanes
Gammacerane Index (GI)	$10*\mathit{\text{gammacerane}}/(\mathit{\text{gammacerane}}+C_{30}\mathit{\text{Hopane}})$
35αβ/34αβ	$35\alpha \beta \mathit{\text{Hopane}} (22S+R)/34\alpha \beta \mathit{\text{Hopane}} (22S+R)$
Ts/(Ts + Tm)	$\mathit{\text{trisnorhopane}}/(\mathit{\text{trisnorneohopane}}+\mathit{\text{trisnorhopane}})$
29Ts/C29αβ	$\mathit{\text{norneohopane}}/\mathit{\text{norhopane}}$
Dia/Norm	$\mathit{\text{diahopane}}/\mathit{\text{normoretane}}$
C24 Tetra/C30 Hop	$C_{24}t\mathit{\text{etracyclic terpane}}/C_{30} \mathit{\text{Hopane}}$
Aromatic Steroids
TAS C27/C28 (R)	$C_{27}(20R)\mathit{\text{TAS}}/C_{28}(20R)\mathit{\text{TAS}}$
TAS C26/C28 (S)	$C_{26}(20S)\mathit{\text{TAS}}/C_{28}(20S)\mathit{\text{TAS}}$
TAS/(TAS + MAS)	$\sum \mathit{\text{TAS}}/(\sum \mathit{\text{TAS}}+\sum \mathit{\text{MAS}})$
TAS C28/(TAS C28+MAS C29)	$C_{28}(20R+S)\mathit{\text{TAS}}/{(C}_{28}(20R+S)\mathit{\text{TAS}}+C_{29}5\alpha (20R+S)\mathit{\text{MAS}}+C_{29}5\beta (20R)\mathit{\text{MAS}})$
Polycyclic Aromatic Hydrocarbons
Fla/Pyr	$\mathit{\text{fluoranthene}}/\mathit{\text{pyrene}}$
Mp/P	$\sum 3+2+9+1m\mathit{\text{ethylphenanthrene}}/\mathit{\text{phenanthrene}}$
MPI-2	$3*2-\mathit{\text{methylphenanthrene}}/(\mathit{\text{phenanthrene}}+1-\mathit{\text{methylphenanthrene}}+9-\mathit{\text{methylphenanthrene}})$
%Rc	$0.6*(\mathit{\text{MPI}}-1+0.4)$

Figure 2. m/z 217 and m/z 218 ion chromatograms of the saturated hydrocarbon fractions of the Alberta Oil Sands samples showing sterane distributions. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 3.

Table 3. Extracted Organic Matter (EOM), selected concentrations, and biomarker and non-biomarker diagnostic ratios from the Alberta Oil Sands samples.

Diagnostic Ratio	Cold Lake	Aurora Mine	A1	A2	MEAN (±SD)
EOM (mg/g)	–	34	7.9	3.6	15(13)
Gammacerane Conc (μg/mg)	n/a	0.05	0.05	0.16	0.09(0.05)
28,30-BNH Conc (μg/mg)	n/a	0.09	0.12	0.28	0.16(0.08)
St27Iso (%)	35	n/a	30	38	34(3.3)
St28Iso (%)	26	n/a	29	30	28(1.7)
St29Iso (%)	39	n/a	41	33	38(3.4)
DiaSt	0.11	n/a	0.25	0.40	0.25(0.12)
Preg	0.34	n/a	0.63	0.70	0.56(0.16)
St29S/R	0.70	n/a	0.71	0.68	0.70(0.01)
St29I/R	0.59	n/a	0.69	0.69	0.66(0.05)
GI	0.93	1.1	0.98	1.1	1.0(0.07)
35αβ/34αβ	1.0	1.1	1.1	1.1	1.1(0.04)
Ts/(Ts + Tm)	0.25	0.25	0.26	0.24	0.25(0.01)
29Ts/C29αβ	0.72	0.67	0.59	0.63	0.65(0.05)
Dia/Norm	0.33	0.33	0.32	0.40	0.35(0.03)
C24 Tetra/C30 Hop	0.17	0.22	0.20	0.18	0.19(0.02)
TAS C27/C28 (R)	0.83	0.77	0.79	0.73	0.78(0.04)
TAS C26/C28 (S)	0.41	0.40	0.40	0.37	0.40(0.02)
TAS/(TAS + MAS)	0.87	0.46	0.47	0.44	0.56(0.18)
TAS C28/(TAS C28+MAS C29)	0.87	0.61	0.56	0.60	0.66(0.12)
Fla/Pyr	n/a	n/a	n/a	n/a	–
Mp/P	4.7	n/a	6.5	n/a	5.6(0.9)
MPI-2	0.77	n/a	0.72	n/a	0.75(0.03)
%Rc	0.84	n/a	0.88	n/a	0.86(0.02)

The key diagnostic ratios identified in this study are highlighted in bold.

Figure 3. m/z 191 ion chromatograms of the saturated hydrocarbon fraction of the Alberta Oil Sands samples showing the terpane, including hopane, distributions. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 3.

Figure 4. m/z 253 and m/z 231 ion chromatograms of the aromatic hydrocarbon fractions of the Alberta Oil Sands samples showing the aromatic steroid distributions. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 3.

Figure 5. m/z 178, m/z 192, m/z 202, and m/z 228 ion chromatograms of the polycyclic aromatic hydrocarbons of the Alberta Oil Sands samples. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 3.

Figure 6. m/z 217 and m/z 218 ion chromatograms of the saturated hydrocarbon fractions of the surficial sediment samples showing sterane distributions. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 4.

Figure 7. Ternary and cross-plot diagrams of diagnostic ratios from the sterane series using m/z 217 and 218; (a) Ternary diagram of the C₂₇, C₂₈, and C₂₉ regular steranes abundance from the m/z 218 ion chromatogram. Depositional environment interpretational overlay from Integrated Geochemical Interpretation (p:IGI 3.5) software (modified after Huang and Meinschein, 1979). (b) Cross-plot of the Preg and DiaSt diagnostic ratios from the m/z 217 ion chromatogram. (c) Cross-plot of the St29S/R and St29I/R diagnostic ratios from the m/z 217 ion chromatogram.

Table 4. Extracted Organic Matter (EOM), selected concentrations, and biomarker and non-biomarker diagnostic ratios from the surficial sediment samples.

Diagnostic Ratio	R1	R2	R3	M1	M2	M3	M4
EOM (mg/g)	0.07	0.08	0.08	0.12	0.10	0.04	0.01
Gammacerane Conc (μg/mg)	0.75	0.00	0.05	0.50	0.48	2.3	0.04
28,30-BNH Conc (μg/mg)	0.65	0.00	0.06	0.39	0.36	2.5	0.04
St27Iso (%)	38	24	25	n/a	34	36	38
St28Iso (%)	27	21	28	n/a	30	31	62
St29Iso (%)	34	55	48	n/a	36	33	n/a
DiaSt	0.34	0.05	0.23	0.43	0.28	0.34	0.30
Preg	0.17	0.19	0.20	0.25	0.10	0.10	0.51
St29S/R	0.73	0.38	0.93	1.00	0.80	1.00	1.00
St29I/R	0.74	0.51	0.57	0.93	0.68	0.75	0.68
GI	2.1	n/a	1.6	3.1	2.7	2.2	10
35αβ/34αβ	1.0	n/a	0.00	1.8	1.5	1.0	n/a
Ts/(Ts + Tm)	0.29	n/a	0.54	0.26	0.27	0.27	n/a
29Ts/C29αβ	0.65	n/a	0.68	0.64	0.76	0.68	0.68
Dia/Norm	0.37	n/a	0.29	0.43	0.35	0.38	0.13
C24 Tetra/C30 Hop	0.14	n/a	0.24	0.27	0.17	0.21	n/a
TAS C27/C28 (R)	0.50	n/a	0.51	0.55	0.52	0.58	n/a
TAS C26/C28 (S)	0.21	n/a	0.16	0.25	0.33	0.16	n/a
TAS/(TAS + MAS)	0.70	n/a	0.63	0.54	0.64	0.59	n/a
TAS C28/ (TAS C28+MAS C29)	0.72	n/a	0.70	0.50	0.68	0.62	n/a
Fla/Pyr	0.74	0.68	0.76	0.66	0.93	0.75	1.03
Mp/P	4.0	0.00	3.0	3.2	2.1	2.6	n/a
MPI-2	0.75	0.00	1.0	0.84	0.74	0.74	n/a
%Rc	0.82	0.40	0.87	0.79	0.73	0.74	n/a

The key diagnostic ratio values that fall within the range of Alberta Oil Sands values in Table 3 are highlighted in bold.

Figure 8. m/z 191 ion chromatograms of the saturated hydrocarbon fraction of the surficial sediment samples showing the terpane, including hopane, distributions. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 4.

Figure 9. Cross-plot diagrams of diagnostic ratio results from the terpane series using m/z 191; (a) Cross-plot of the 35αβ/34αβ hopane and Gammacerane Index. (b) Cross-plot of the Ts/(Ts + Tm) and 29Ts/C₂₉αβ diagnostic ratios. (c) Cross-plot of the Dia/Norm and C₂₄Tetra/C₃₀αβ Hopane diagnostic ratios.

Figure 10. m/z 253 and m/z 231 ion chromatograms of the aromatic hydrocarbon fractions of the surficial sediment samples showing aromatic steroid distributions. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 4.

Figure 11. Cross-plot diagrams of diagnostic ratio results from the aromatic steroid series using m/z 253 and 231; (a) Cross-plot of the TAS C₂₇/C₂₈ (20 R) and TAS C₂₆/C₂₈ (20S) diagnostic ratios. (b) Cross-plot of the TAS/(TAS + MAS) and TAS C₂₈/(TAS C₂₈ + MAS C₂₉) diagnostic ratios.

Figure 12. m/z 178, m/z 192, m/z 202, and m/z 228 ion chromatograms of the polycyclic aromatic hydrocarbons of the surficial sediment samples. The grey shading highlights the key compounds used to calculate the diagnostic ratios in Table 4.

Figure 13. Cross-plots of diagnostic ratios of polycyclic aromatic hydrocarbons using m/z 178, 192, 202, and 228; (a) Mp/P and Fla/Pyr ratios with interpretation overlay adapted from Ahmed et al. (2006). (b) MPI-2 and %Rc ratios with overlay from Esegbue et al. (2020).

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Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary materials.