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

Abstract

Abstract. The oil sands industry in Alberta, Canada, represents a large anthropogenic source of secondary organic aerosol (SOA). Atmospheric emissions from oil sands operations are a complex mixture of gaseous and particulate pollutants. Their interaction can affect the formation and characteristics of SOA during plume dispersion, but their chemical evolution remains poorly understood. Oxidative processing of organic vapours in the presence of NOx can lead to particulate organo-nitrate (pON) formation, with important impacts on the SOA budgets, the nitrogen cycle and human health. We provide the first direct field evidence, from ground- and aircraft-based real-time aerosol mass spectrometry, that anthropogenic pON contributed up to half of SOA mass that was freshly produced within the emission plumes of oil sands facilities. Using a top-down emission-rate retrieval algorithm constrained by aircraft measurements, we estimate the production rate of pON in the oil sands region to be ∼15.5 t d−1. We demonstrate that pON formation occurs via photo-oxidation of intermediate-volatility organic compounds (IVOCs) in high-NOx environments, providing observational constraints to improve current SOA modelling frameworks. Our ambient observations are supported by laboratory photo-oxidation experiments of IVOCs from bitumen vapours under high-NOx conditions, which demonstrate that pON can account for 30 %–55 % of the observed SOA mass depending on the degree of photochemical ageing. The large contribution of pON to freshly formed anthropogenic SOA illustrates the central role of pON in SOA production from the oil and gas industry, with relevance for other urban and industrial regions with significant anthropogenic IVOC and NOx emissions.

Estimation of particulate organic nitrates from thermodenuder-aerosol mass spectrometer measurements in North China Plain

“…NO 3,org with POA was found in winter in NCP (R 2 =0.49-0.52), suggesting that primary emissions can be an important source of pON in winter in NCP, which may be related to NO 3 oxidation of AVOC emitted from anthropogenic activities (Li et al, 2019;Lee et al, 2019). Our results are consistent with the considerable contributions of alkanes (a typical AVOC) to pON production in previous field (Lee et al, 2015), model (Jordan et al, 2008) and chamber studies (Lim and Ziemann, 2009).…”

“…In fact, there is a growing consensus about the importance of AVOC (e.g. styrene (Yu et al, 2019), toluene (Ramasamy et al, 2019) and long-chain aliphatics (Matsunaga and Ziemann, 2010)) in pON formation under high NO x condition (Lee et al, 2015;Li et al, 2019;Lee et al, 2019).…”

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

“…Ground-level particle composition was measured using an Aerodyne high-resolution soot particle aerosol mass spectrometer (SP-AMS) (Lee et al, 2019). Particle size distributions were measured using Scanning Mobility Particle Sizer (SMPS) ("dry" line mode) and Aerodynamic Particle Sizer (APS) instruments (see supplementary information in Tokarek et al, 2018, for more details).…”

“…Our aerosol retrieval used an iterative algorithm based on the Levenberg-Marquart method (Levenberg, 1944;Marquardt, 1963). For aerosol retrievals, the weighting function K is calculated using the a priori x a and the measurement vector y.…”

Evidence of Nighttime Production of Organic Nitrates During SEAC4RS, FRAPPÉ, and KORUS‐AQ

“…Moreover, NO 3 oxidation has been shown to be a significant source of organic aerosol in the Central Valley of California (Rollins et al, 2012), the Southeastern United States (Ayres et al, 2015; Fisher et al, 2016; Lee et al, 2016; Pye et al, 2015; Xu, Guo et al 2015; Xu, Suresh et al 2015), in a forested region of Colorado (Fry et al, 2013), in rural Southwestern Germany (Huang et al, 2019), throughout Europe (Kiendler‐Scharr et al, 2016), and in the Alberta oil sands (Lee et al, 2019).…”