High Oxidative Potential Observed in Secondary Organic Aerosol Derived from Oil Sands Emissions

High Resolution Image Download MS PowerPoint Slide Oil sands operations in Alberta, Canada, are a large source of secondary organic aerosol (SOA) with unknown health impacts. As a first step in closing this knowledge gap, the oxidative potential (OP), an established metric linking particle exposure to toxicological effects, of oil sands-derived SOA was investigated via OH-initiated oxidation. Experiments used a mixture of gas-phase precursors emitted from oil sands ore that is expected to be representative of mine-face emissions and three relevant single precursors ( n -decane, m -xylene, and naphthalene) for comparison. The OP of the formed SOA in all cases was found to increase rapidly at short simulated photochemical ages (<1.5 days), followed by a decrease upon further oxidation (>2.5 days). This was driven by dynamic changes in SOA composition, particularly organic peroxides, quinones, and unsaturated carbonyls. The measured OP of oil sand ore SOA (OP OS ) ranged from 38.0 to 60.3 pmol min –1 μg –1 over photochemical ages of 0.4–4.6 days. This range of OP OS is considerably higher than those reported for other types of aerosol particles typically present in the oil sands region, including the natural background (e.g., α-pinene and isoprene SOA). The results not only provide the first OP measurements of oil sands-derived SOA but also emphasize the importance of accounting for atmospheric aging when evaluating the oxidative potential of SOA.