Oil sands operations as a large source of secondary organic aerosols

Abstract

Worldwide heavy oil and bitumen deposits amount to 9 trillion barrels of oil distributed in over 280 basins around the world, with Canada home to oil sands deposits of 1.7 trillion barrels. The global development of this resource and the increase in oil production from oil sands has caused environmental concerns over the presence of toxic compounds in nearby ecosystems and acid deposition. The contribution of oil sands exploration to secondary organic aerosol formation, an important component of atmospheric particulate matter that affects air quality and climate, remains poorly understood. Here we use data from airborne measurements over the Canadian oil sands, laboratory experiments and a box-model study to provide a quantitative assessment of the magnitude of secondary organic aerosol production from oil sands emissions. We find that the evaporation and atmospheric oxidation of low-volatility organic vapours from the mined oil sands material is directly responsible for the majority of the observed secondary organic aerosol mass. The resultant production rates of 45-84 tonnes per day make the oil sands one of the largest sources of anthropogenic secondary organic aerosols in North America. Heavy oil and bitumen account for over ten per cent of global oil production today, and this figure continues to grow. Our findings suggest that the production of the more viscous crude oils could be a large source of secondary organic aerosols in many production and refining regions worldwide, and that such production should be considered when assessing the environmental impacts of current and planned bitumen and heavy oil extraction projects globally.

Differences between measured and reported volatile organic compound emissions from oil sands facilities in Alberta, Canada

“…These compounds are intermediate and semivolatility organic compounds, with air saturation vapor concentrations in the range of 10 4 -10 7 μg/m 3 . They were proposed as the precursors of secondary organic aerosols measured downwind from the facilities (33). These hydrocarbons cannot be quantified using either of the detection methods used in this study, thus their emission rates were not determined.…”

“…Higher molecular weight compounds beyond those of 73-93 measured VOCs are also known to be emitted, mostly from mine faces and tailings ponds. For example, analytically unresolved hydrocarbons (URHCs), ranging from C 10 to C 16 and higher, are known to be present in oil sands air emissions (33,39). These compounds are intermediate and semivolatility organic compounds, with air saturation vapor concentrations in the range of 10 4 -10 7 μg/m 3 .…”

“…Correction factors for E were estimated using known or modelpredicted oxidation rate constants (ref. 32; https://www.epa.gov/ tsca-screening-tools) (SI Appendix, Table S2), the observed O 3 mixing ratios of 30-40 parts per billion (ppb), and a modeled OH radical concentration range of 1-5 × 10 6 molecules cm −3 (33) during the flights, which is consistent with those typically found in background air (34,35). The correction factors estimated were between 1.01 ± 0.01 and 1.2 ± 0.2 for each of the aromatics and OVOCs, with the overall uncertainties arising mostly from those associated with the transport times and the OH concentration range (Methods).…”

“…For the observed O 3 mixing ratios of 30-40 ppb and an assumed OH radical concentration range of 1-5 × 10 6 molecules cm −3 (33)(34)(35) during the flights and using the observed wind speeds, the correction factor A i ± ΔA i ranged between 1.01 ± 0.01 and 1.2 ± 0.2 for the aromatic hydrocarbons measured with PTRMS, where the uncertainty ΔA i was determined from the variations in the transport times on different days and the range of chosen OH concentrations. The values of these correction factors are listed in SI Appendix, Table S2 for each of four facilities.…”

Understanding the primary emissions and secondary formation of gaseous organic acids in the oil sands region of Alberta, Canada

“…Details regarding the overarching study objectives, aircraft campaign implementation, and technical aspects have been described previously Liggio et al, 2016). During this study, 22 flights were conducted over the oil sands for a total of approximately 84 h. To quantify the total primary emissions for each facility, 13 of the flights were conducted by flying in the shape of a four-or five-sided polygon, at multiple altitudes, resulting in 21 separate virtual boxes around seven oil sands facilities.…”