AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Rapid Formation of Secondary Organic Aerosols from Alberta Oil Sands Emissions
Max Adam, ALEX LEE, Megan Willis, Jonathan Abbatt, Charles Odame-Ankrah, Jennifer Huo, Travis Tokarek, Hans Osthoff, Jeff Brook, Shao-Meng Li, National University of Singapore
Abstract Number: 161 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Oil sands operations contribute significantly to organic aerosol (OA) formation, particularly secondary OA (SOA), which can have detrimental impacts on air quality. To better understand formation and characteristics of OA related to oil sands emissions, real-time measurements of refractory black carbon (rBC) and non-refractory particulate matter (NR-PM, including organic, sulfate, nitrate, ammonium and chloride) in PM1 were made in the Alberta oil sands region using an Aerodyne Soot-Particle Aerosol Mass Spectrometer (SP-AMS) from 11 August to 10 September 2013. Positive matrix factorization (PMF) of SP-AMS measurement was performed to identify sources of OA components. With supporting co-located gas-phase measurements (SO2, NOx and O3) and meteorological data, four types of OA were identified at the measurement site. Hydrocarbon-like OA (HOA) from combustion emissions showed significant correlations to rBC and NOx. Two oxygenated OA (OOA) factors with relatively low O/C ratios, referred to as sulfate-OOA and Oil Sands-OOA (OS-OOA), were secondary in nature. They were primarily transported from the southeast, indicating two strong anthropogenic emission sources in that direction. While sulfate-OOA was associated with acidic sulfate and SO2 plumes, OS-OOA strongly correlated to particle-phase nitrate. Lastly, an aged-OOA factor with relatively high O/C ratio was not wind direction dependent, suggesting that the aged-OOA was more evenly distributed in the oil sands region. Using -log(NOx/NOy) as a photochemical clock, we observed a higher overall Org-to-BC ratio with atmospheric aging and OS-OOA contributed up to ~45% of total OA mass in fresh air masses, indicating rapid formation of SOA from oil sands emissions. Results from single particle characterization of the particles from the SP-AMS validate the separation of sulfate-OOA and OS-OOA factors in PMF results.