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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-627
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
17 Oct 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Contributions of natural and anthropogenic sources to ambient ammonia in the Athabasca Oil Sands and north-western Canada
Cynthia Whaley1, Paul A. Makar1, Mark W. Shephard1, Leiming Zhang1, Junhua Zhang1, Qiong Zheng1, Ayodeji Akingunola1, Gregory R. Wentworth2,3, Jennifer G. Murphy2, Shailesh K. Kharol1, and Karen E. Cady-Pereira4 1Air Quality Research Division, Environment and Climate Change Canada, 4905 Dufferin Street, Toronto, Ontario, Canada
2Dept of Chemistry, University of Toronto, 80 St George Street, Toronto, Ontario, Canada
3Environmental Monitoring and Science Division, Alberta Environment and Parks, 9888 Jasper Ave NW, Edmonton, Alberta, Canada
4Atmospheric and Environmental Research (AER), Lexington, Massachusetts, USA
Abstract. Atmospheric ammonia (NH3) is a short-lived pollutant that plays an important role in aerosol chemistry and nitrogen deposition. Dominant NH3 emissions are from agriculture and forest fires, both of which are increasing globally. The Alberta Oil Sands region has relatively low ambient NH3 concentrations because of its remote location in northern Canada; however, a previous attempt to model NH3 in the region showed a substantial negative bias compared to satellite column and aircraft observations. Known missing sources of NH3 in the model were re-emission of NH3 from plants and soils (bidirectional flux), and forest fire emissions, but the relative impact of these sources on NH3 concentrations and column totals was unknown. Here we have used a research version of the high-resolution air quality forecasting model, GEM-MACH, to quantify the relative impacts of natural (bidirectional flux of NH3 and forest fire emissions) and anthropogenic (Oil Sands operations, combustion of fossil fuels, and agriculture) sources on ammonia concentrations, both at the surface and aloft, with a focus on the Athabasca Oil Sands region, during a measurement-intensive campaign in the summer of 2013. The addition of fires and bidirectional flux has improved the model bias, slope and correlation coefficients relative to ground, aircraft, and satellite measurements significantly. By running the GEM-MACH model in three configurations and calculating their differences, we find that averaged over Alberta and Saskatchewan during this time period; an average of 23.1 % of surface NH3 came from direct anthropogenic sources, 56.6 % (or 1.24 ppbv) from bidirectional flux (reemission from plants and soils), and 20.3 % (or 0.42 ppbv) from forest fires. In the NH3 total column, an average of 19.5 % came from direct anthropogenic sources, 50.0 % from bidirectional flux, and 30.5 % from forest fires. The addition of bidirectional flux and fire emissions caused the overall average net flux of NH3 across the domain to be positive (upward). It also increased the NH+4 wet deposition by nearly a factor of three during the period simulated. Note that forest fires are very episodic and their contributions will vary significantly for different time periods and regions.

Citation: Whaley, C., Makar, P. A., Shephard, M. W., Zhang, L., Zhang, J., Zheng, Q., Akingunola, A., Wentworth, G. R., Murphy, J. G., Kharol, S. K., and Cady-Pereira, K. E.: Contributions of natural and anthropogenic sources to ambient ammonia in the Athabasca Oil Sands and north-western Canada, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-627, in review, 2017.
Cynthia Whaley et al.
Cynthia Whaley et al.
Cynthia Whaley et al.

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Short summary
Using a modified air quality forecasting model, we have found that a significant fraction (> 50 %) of ambient ammonia comes from re-emission from plants and soils in the broader Athabasca Oil Sands Region and much of Alberta and Saskatchewan. We also found that about 20 % of ambient ammonia in Alberta and Saskatchewan came from forest fires in the summer of 2013. The addition of these two processes improved modelled ammonia, which was a motivating factor in undertaking this research.
Using a modified air quality forecasting model, we have found that a significant fraction...
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