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

Abstract

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), particle-surface-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.

Secondary organic aerosol formation from <i>α</i>-pinene, alkanes, and oil-sands-related precursors in a new oxidation flow reactor

“…For some samples with high volatilities (e.g., naphtha and n-heptane), the gas phase was further diluted before being injected into the reactor. The total hydrocarbon (THC) concentration entering the ECCC-OFR was determined by passing the input gas stream (in offline experiments) through a Pt-based catalytic converter maintained at 400 • C and measuring the subsequently evolved CO 2 (LI-COR LI-840A) as described by Veres et al (2010). The evolved CO 2 concentration (ppb) is converted to the total carbon concentration (ppbC; see Table 1).…”

“…S7 and Fig. S2) but has been shown to be equally efficient at lower carbon numbers (Veres et al, 2010). The THC concentration was measured before and after each experiment, resulting in differences of less than 5 %.…”

Validation of MAX-DOAS retrievals of aerosol extinction, SO<sub>2</sub>, and NO<sub>2</sub> through comparison with lidar, sun photometer, active DOAS, and aircraft measurements in the Athabasca oil sands region

“…The absolute value of the O 4 cross section and its dependence on temperature is uncertain. Some studies suggest that the absolute value of the cross section may be overestimated by up to 25 %, requiring the use of a scaling factor (Clémer et al, 2010;Wagner et al, 2002Wagner et al, , 2009Wagner et al, , 2019. However, Frieß et al (2011) found that the best results for measured O 4 dSCDs and the vertical profiles of aerosol extinction retrieved from them were achieved without a scaling factor.…”

A large contribution of anthropogenic organo-nitrates to secondary organic aerosol in the Alberta oil sands

“…The laser-off and laser-on modes of SP-AMS measurements were used for quantifying the non-refractory particulate matter (NR-PM; including SO 2− 4 , NO − 3 , NH + 4 and organics) and refractory black carbon (rBC), respectively (A. K. Y. Onasch et al, 2012), and for performing source-apportionment analysis of ambient organic aerosol via positive matrix factorization (PMF; Ulbrich et al, 2009;Zhang et al, 2011). Single-particle characterization was achieved from 22 to 29 August 2013 by deploying another co-located SP-AMS equipped with a lightscattering module (A. K. Y. in order to assess the mixing state of the NR-PM during the ground-based campaign.…”