Airborne Petcoke Dust is a Major Source of Polycyclic Aromatic Hydrocarbons in the Athabasca Oil Sands Region

Abstract

Oil sands mining has been linked to increasing atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) in the Athabasca oil sands region (AOSR), but known sources cannot explain the quantity of PAHs in environmental samples. PAHs were measured in living Sphagnum moss (24 sites, n = 68), in sectioned peat cores (4 sites, n = 161), and snow (7 sites, n = 19) from ombrotrophic bogs in the AOSR. Prospective source samples were also analyzed, including petroleum coke (petcoke, from both delayed and fluid coking), fine tailings, oil sands ore, and naturally exposed bitumen. Average PAH concentrations in near-field moss (199 ng/g, n = 11) were significantly higher (p = 0.035) than in far-field moss (118 ng/g, n = 13), and increasing temporal trends were detected in three peat cores collected closest to industrial activity. A chemical mass-balance model estimated that delayed petcoke was the major source of PAHs to living moss, and among three peat core the contribution to PAHs from delayed petcoke increased over time, accounting for 45-95% of PAHs in contemporary layers. Petcoke was also estimated to be a major source of vanadium, nickel, and molybdenum. Scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed large petcoke particles (>10 μm) in snow at near-field sites. Petcoke dust has not previously been considered in environmental impact assessments of oil sands upgrading, and improved dust control from growing stockpiles may mitigate future risks.

Advances in science and applications of air pollution monitoring: A case study on oil sands monitoring targeting ecosystem protection

“…The long-term temporal trends of PAC deposition first shown for lakes relatively close to the more-active surface mining areas (Figure 3) have now been studied among a larger number of lakes, including those farther away such as in the PAD . Results from peat cores (Zhang et al 2016) are also available and largely confirm the temporal and spatial patterns seen from the lake sediments: increases in alk-PAHs, DBTs, and alk-DBTs correspond to the period of OS development and expansion. Harner et al (2018) highlighted results of isotopic analysis (Bosch et al 2015) of sediment cores from a small lake in the PAD (Jautzy et al 2015).…”

“…Consistent with the spatial pattern in air concentrations (Schuster et al 2019), deposition occurs on a gradient, with higher deposition near oil sands production activity. Spatial patterns of PAC deposition have been explored using a variety of methods, including snow (Manzano et al 2016), bulk deposition collectors (Bari, Kindzierski, and Cho 2014), lichen (Graney et al 2017;Landis et al 2019), moss sampling (Zhang et al 2016), and a passive dry deposition sampler (Jariyasopit et al 2018). However, quantitative linkage between concentrations in air and/or precipitation and the levels in these different forms of collection media is difficult to assess (Zhang et al 2016).…”

“…Petcoke has been of interest given its open storage at the facilities with on-site upgrading and the toxics it contains. Petcoke has been identified in snow (Zhang et al 2016), passive air samplers (Jariyasopit et al 2018), moss (Zhang et al 2016), and lichen (Landis et al 2019). Quantitative estimates of petcoke's and other sources' contributions to PAHs in moss using chemical mass balance (CMB) have been shown to be feasible (Zhang et al 2016).…”

Emissions databases for polycyclic aromatic compounds in the Canadian Athabasca Oil Sands Region – development using current knowledge and evaluation with passive sampling and air dispersion modelling data

“…This could be due to (1) a lack of emissions estimates from other oil sands sources, such as mine face and facility fugitive emissions (e.g. Zhang et al, 2016), since alkylated PAH and DBT emissions were only estimated from mine fleet, line sources, and tailings ponds; and (2) uncertainties with using monitored concentration ratios (R) between PAHs and alkylated PAHs/DBTs to back-calculate alkylated PAH and DBT emissions (sect. 1.5 in the SI).…”

“…Model simulations considering only direct air emissions underestimated phenanthrene, pyrene and 5 benzo(a)pyrene concentrations in air, water, soil and foliage, whereas simulations including both direct air emissions and tailings pond emissions were more comparable to observations (Parajulee and Wania, 2014). Another source of airborne PAHs that has not been included in the emissions inventory is petroleum coke stockpiles in the mining areas, which can be resuspended by wind and deposited (Zhang et al, 2016). Analysis of wildlife samples near oil sands development indicate moose and wolves have been exposed to alkylated PAHs from petrogenic sources 10 (Lundin et al, 2015).…”