Comparison of Polycyclic Aromatic Compounds in Air Measured by Conventional Passive and Passive Dry Deposition Samplers and Contributions from Petcoke and Oil Sands Ore
Abstract. Conventional passive air samplers (PAS) and passive dry deposition (PAS-DD) samplers were deployed along a 90 km south-north transect at five sites in the Athabasca oil sands region during October to November 2015. The purpose was to compare and characterize the performance of the two passive sampling methods for targeted compounds across a range of site types. Samples were analyzed for polycyclic aromatic compounds (PACs), nitrated polycyclic aromatic hydrocarbons (NPAHs), and oxygenated PAHs (OPAHs). ΣPAC and ΣNPAH concentrations were highest in PAS and PAS-DD samplers at site AMS5, which is the closest sampling site to surface mining and upgrading facilities. The OPAHs were elevated at site AMS6, which is located in the town of Fort McMurray, approximately 30 km south of the main mining area. The PAS-DD was enriched relative to the PAS in particle associated target chemicals, which is consistent with the relatively more open design of the PAS-DD intended to capture particle- (and gas-phase) deposition. Petroleum coke (petcoke) (i.e. the carbonaceous by-product of bitumen upgrading) and oil sands ore (i.e. the material mined in open pit mines from which bitumen is extracted) were assessed for their potential to be a source of PACs to air in the oil sands region. The ore samples contained ~ 8 times and ~ 40 times higher ΣPACs concentrations (dry weight basis) than delayed and fluid petcoke, respectively. The residue analysis of ore and petcoke samples also revealed that the chemical 4-nitrobiphenyl (4-NBP) can be used to track gas-phase emissions to air. A comparison of chemical residues in ore, petcoke and air samples revealed that the ore is likely a major contributor to volatile PACs present in air and that both ore and petcoke are contributing to the particle-associated PACs in air near open pit mining areas. The contribution of petcoke particles in passive air samples was also confirmed qualitatively using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy.