Abstract
During May 2016 a very large boreal wildfire burned throughout the Athabasca Oil Sands Region (AOSR) in central Canada, and in close proximity to an extensive air quality monitoring network. This study examines speciated 24-h integrated polycyclic aromatic hydrocarbon (PAH) and volatile organic compound (VOC) measurements collected every sixth day at four and seven sites, respectively, from May to August 2016. The sum of PAHs (ΣPAH) was on average 17 times higher in fire-influenced samples (852 ng m−3, n = 8), relative to non-fire influenced samples (50 ng m−3, n = 64). Diagnostic PAH ratios in fire-influenced samples were indicative of a biomass burning source, whereas ratios in June to August samples showed additional influence from petrogenic and fossil fuel combustion. The average increase in the sum of VOCs (ΣVOC) was minor by comparison: 63 ppbv for fire-influenced samples (n = 16) versus 46 ppbv for non-fire samples (n = 90). The samples collected on August 16th and 22nd had large ΣVOC concentrations at all sites (average of 123 ppbv) that were unrelated to wildfire emissions, and composed primarily of acetaldehyde and methanol suggesting a photochemically aged air mass. Normalized excess enhancement ratios (ERs) were calculated for 20 VOCs and 23 PAHs for three fire influenced samples, and the former were generally consistent with previous observations. To our knowledge, this is the first study to report ER measurements for a number of VOCs and PAHs in fresh North American boreal wildfire plumes. During May the aged wildfire plume intercepted the cities of Edmonton (∼380 km south) or Lethbridge (∼790 km south) on four separate occasions. No enhancement in ground-level ozone (O3) was observed in these aged plumes despite an assumed increase in O3 precursors. In the AOSR, the only daily-averaged VOCs which approached or exceeded the hourly Alberta Ambient Air Quality Objectives (AAAQOs) were benzene (during the fire) and acetaldehyde (on August 16th and 22nd). Implications for local and regional air quality as well as suggestions for supplemental air monitoring during future boreal fires, are also discussed.
Highlights
Wildfires are a common occurrence in many regions of the world and can release significant quantities of trace gases and particulate matter to the atmosphere (Andreae and Merlet, 2001)
Integrated polycyclic aromatic hydrocarbon (PAH) and volatile organic compound (VOC) samples, as well as various continuous atmospheric measurements are routinely taken at the following air monitoring stations (AMS) throughout the Athabasca Oil Sands Region (AOSR): Bertha Ganter-Fort McKay (AMS 1; 111.640° W, 57.189° N), Fort McMurray Patricia McInnes (AMS 6; 111.476° W, 56.741° N), Fort McMurray Athabasca Valley (AMS 7; 111.390° W, 56.733° N), Barge Landing (AMS 9; 111.600° W, 57.198° N), Fort McKay South (AMS 13; 111.653° W, 57.149° N), Anzac (AMS 14; 111.037° W, 56.449° N), and CNRL Horizon (AMS 15; 111.740° W, 57.304° N)
This study examined routine measurements from an extensive air quality monitoring network in the AOSR both during and after the 2016 Horse River Wildfire
Summary
Wildfires are a common occurrence in many regions of the world and can release significant quantities of trace gases and particulate matter to the atmosphere (Andreae and Merlet, 2001). Polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) are emitted from wildfires (e.g., Hatch et al, 2017; Jenkins et al, 1996). Numerous studies have observed significant increases in ground-level O3 in aged wildfire plumes due to enhanced VOCs and NOx (Jaffe and Wigder, 2012; and references therein). Despite these potential effects, a review by Reisen and Brown (2006) emphasized that the majority of studies examining health impacts of wildfire smoke have focused on inhalation of fine particulate matter (PM2.5), and generally give less attention to potential effects of PAHs and VOCs
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