Principal component analysis of summertime ground site measurements in the Athabasca oil sands with a focus on analytically unresolved intermediate-volatility organic compounds

Atmos. Chem. Phys., 18, 17819–17841, 2018 https://doi.org/10.5194/acp-18-17819-2018 © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License. Principal component analysis of summertime ground site measurements in the Athabasca oil sands with a focus on analytically unresolved intermediate-volatility organic compounds Travis W. Tokarek1 , Charles A. Odame-Ankrah1 , Jennifer A. Huo1 , Robert McLaren2 , Alex K. Y. Lee3,4 , Max G. Adam4 , Megan D. Willis5,a , Jonathan P. D. Abbatt5 , Cristian Mihele6 , Andrea Darlington6 , Richard L. Mittermeier6 , Kevin Strawbridge6 , Katherine L. Hayden6 , Jason S. Olfert7 , Elijah G. Schnitzler8 , Duncan K. Brownsey1 , Faisal V. Assad1 , Gregory R. Wentworth5,b , Alex G. Tevlin5 , Douglas E. J. Worthy6 , Shao-Meng Li6 , John Liggio6 , Jeffrey R. Brook6 , and Hans D. Osthoff1 1 Department of Chemistry, University of Calgary, Calgary, Alberta, T2N 1N4, Canada 2 Centre for Atmospheric Chemistry, York University, Toronto, Ontario, M3J 1P3, Canada 3 Department of Civil and Environmental Engineering, National University of Singapore, Singapore 117576, Singapore 4 NUS Environmental Research Institute, National University of Singapore, Singapore 5 Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6, Canada 6 Air Quality Research Division, Environment and Climate Change Canada, Toronto, Ontario, M3H 5T4, Canada 7 Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, T6G 1H9, Canada 8 Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada a now at: Lawrence Berkeley National Lab, Chemical Sciences Division, Berkeley, California 94720, USA b now at: Environmental Monitoring and Science Division, Alberta Environment and Parks, Edmonton, Alberta, T5J 5C6, Canada Correspondence: Hans D. Osthoff () Received: 2 November 2017 – Discussion started: 25 January 2018 Revised: 19 November 2018 – Accepted: 25 November 2018 – Published: 14 December 2018 Abstract. In this paper, measurements of air pollutants made at a ground site near Fort McKay in the Athabasca oil sands region as part of a multi-platform campaign in the summer of 2013 are presented. The observations included measurements of selected volatile organic compounds (VOCs) by a gas chromatograph–ion trap mass spectrometer (GC-ITMS). This instrument observed a large, analytically unresolved hydrocarbon peak (with a retention index between 1100 and 1700) associated with intermediate-volatility organic compounds (IVOCs). However, the activities or processes that contribute to the release of these IVOCs in the oil sands region remain unclear. Principal component analysis (PCA) with varimax rotation was applied to elucidate major source types impacting the sampling site in the summer of 2013. The analysis included 28 variables, including concentrations of total odd nitrogen (NOy ), carbon dioxide (CO2 ), methane (CH4 ), ammonia (NH3 ), carbon monoxide (CO), sulfur dioxide (SO2 ), total reduced-sulfur compounds (TRSs), speciated monoterpenes (including α- and β-pinene and limonene), particle volume calculated from measured size distributions of particles less than 10 and 1 µm in diameter (PM10−1 and PM1 ), particlesurface-bound polycyclic aromatic hydrocarbons (pPAHs), and aerosol mass spectrometer composition measurements, including refractory black carbon (rBC) and organic aerosol components. The PCA was complemented by bivariate polar plots showing the joint wind speed and direction dependence of air pollutant concentrations to illustrate the spatial distribution of sources in the area. Using the 95 % cumulative percentage of variance criterion, 10 components were identified and categorized by source type. These included emissions by wet tailing ponds, vegetation, open pit mining operations, upgrader facilities, and surface dust. Three components correlated with IVOCs, with the largest associated with surface mining and likely caused by the unearthing and processing of raw bitumen. Published by Copernicus Publications on behalf of the European Geosciences Union. 17820 1 Introduction The Athabasca oil sands region of Northern Alberta, Canada, has seen extraordinary expansion of its oil sands production and processing facilities (CAPP, 2016) and associated emissions of air pollutants over the last several decades (Englander et al., 2013; Bari and Kindzierski, 2015). Air emissions from these facilities have been impacting surrounding communities, including the city of Fort McMurray and the community of Fort McKay (WBEA, 2013). To assess the impact of these emissions on human health, visibility, climate, and the ecosystems downwind, it is critical to obtain an understanding of the source types from all activities associated with oil sands operations (ECCC, 2016). Prior to 2013, there had been only a single industryindependent study of trace gas emissions from the Athabasca oil sands mining operations (Simpson et al., 2010; Howell et al., 2014). The data showed elevated concentrations in nalkanes (30 % of the total quantified hydrocarbon emissions), cycloalkanes (49 %), and aromatics (15 %) in plumes from an oil sands surface mining facility intercepted from a single aircraft flight. These compounds are associated with oil and gas developments including mining, upgrading, and transportation of bitumen (Siddique et al., 2006). Specifically, these activities involve the use of naphtha, a complex mixture of aliphatic and aromatic hydrocarbons in the range of C3 to C14 -containing n-alkanes (e.g., n-heptane, n-octane, and n-nonane) and benzene, toluene, ethylbenzene, and xylenes (BTEX). In August 2013, a comprehensive air quality study as a part of the Joint Oil Sands Monitoring (JOSM) plan (JOSM, 2012), referred to here as the 2013 JOSM intensive study, was conducted. This study was performed in northern Alberta at two ground sites in and near Fort McKay in close proximity (as close as 3.5 km) to oil sands mining operations and from a National Research Council of Canada (NRC) Convair 580 research aircraft to characterize oil sands emissions and their downwind physical and chemical transformations (Gordon et al., 2015; Liggio et al., 2016; Li et al., 2017). One ground site, located at Wood Buffalo Environmental Association (WBEA) air monitoring station (AMS) 13 (Fig. 1), was equipped with a comprehensive set of instrumentation to measure concentrations of a wide range of trace gases and aerosols (Table 1), yielding a unique and new data set, parts of which are presented in this paper for the first time. As part of this effort, a gas chromatograph equipped with an ion trap mass spectrometer (GCITMS) was deployed at AMS 13. When air masses passing over regions with industrial activities were observed (as judged from a combination of local wind direction and tracer measurements), the total ion chromatogram showed an analytically unresolved hydrocarbon signal associated with intermediate-volat (...truncated)