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Volume 18, issue 4 | Copyright

Special issue: Atmospheric emissions from oil sands development and their...

Atmos. Chem. Phys., 18, 2653-2667, 2018
https://doi.org/10.5194/acp-18-2653-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Feb 2018

Research article | 23 Feb 2018

Size distribution and coating thickness of black carbon from the Canadian oil sands operations

Yuan Cheng1, Shao-Meng Li1, Mark Gordon2, and Peter Liu1 Yuan Cheng et al.
  • 1Air Quality Research Division, Environment and Climate Change Canada, 4905 Dufferin Street, Toronto, Ontario M3H 5T4, Canada
  • 2Department of Earth and Space Science and Engineering, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada

Abstract. Black carbon (BC) plays an important role in the Earth's climate system. However, parameterizations of BC size and mixing state have not been well addressed in aerosol–climate models, introducing substantial uncertainties into the estimation of radiative forcing by BC. In this study, we focused on BC emissions from the oil sands (OS) surface mining activities in northern Alberta, based on an aircraft campaign conducted over the Athabasca OS region in 2013. A total of 14 flights were made over the OS source area, in which the aircraft was typically flown in a four- or five-sided polygon pattern along flight tracks encircling an OS facility. Another 3 flights were performed downwind of the OS source area, each of which involved at least three intercepting locations where the well-mixed OS plume was measured along flight tracks perpendicular to the wind direction. Comparable size distributions were observed for refractory black carbon (rBC) over and downwind of the OS facilities, with rBC mass median diameters (MMDs) between ∼ 135 and 145nm that were characteristic of fresh urban emissions. This MMD range corresponded to rBC number median diameters (NMDs) of ∼ 60–70nm, approximately 100% higher than the NMD settings in some aerosol–climate models. The typical in- and out-of-plume segments of a flight, which had different rBC concentrations and photochemical ages, showed consistent rBC size distributions in terms of MMD, NMD and the corresponding distribution widths. Moreover, rBC size distributions remained unchanged at different downwind distances from the source area, suggesting that atmospheric aging would not necessarily change rBC size distribution. However, aging indeed influenced rBC mixing state. Coating thickness for rBC cores in the diameter range of 130–160nm was nearly doubled (from ∼20 to 40nm) within 3h when the OS plume was transported over a distance of 90km from the source area.

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An aircraft campaign was conducted over the Athabasca oil sands (OS) region to characterize refractory black carbon (rBC) particles as they were emitted from the sources and as they were transported downwind; rBC size distributions were consistent at different downwind distances from the source area whereas coating thicknesses on the rBC cores increased considerably as the OS plumes were transported downwind. These results provide insights into the evolution of BC aerosol in the real atmosphere.
An aircraft campaign was conducted over the Athabasca oil sands (OS) region to characterize...
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