Measurement of fine particulate matter water-soluble inorganic species and precursor gases in the Alberta Oil Sands Region using an improved semicontinuous monitor

A decadal synthesis of atmospheric emissions, ambient air quality, and deposition in the oil sands region

This review is part of a series synthesizing peer-reviewed literature from the past decade on environmental monitoring in the oil sands region (OSR) of northeastern Alberta. It focuses on atmospheric emissions, air quality, and deposition in and downwind of the OSR. Most published monitoring and research activities were concentrated in the surface-mineable region in the Athabasca OSR. Substantial progress has been made in understanding oil sands (OS)-related emission sources using multiple approaches: airborne measurements, satellite measurements, source emission testing, deterministic modeling, and source apportionment modeling. These approaches generally yield consistent results, indicating OS-related sources are regional contributors to nearly all air pollutants. Most pollutants exhibit enhanced air concentrations within ~20 km of surface-mining activities, with some enhanced >100 km downwind. Some pollutants (e.g., sulfur dioxide, nitrogen oxides) undergo transformations as they are transported through the atmosphere. Deposition rates of OS-related substances primarily emitted as fugitive dust are enhanced within ~30 km of surface-mining activities, whereas gaseous and fine particulate emissions have a more diffuse deposition enhancement pattern extending hundreds of kilometers downwind. In general, air quality guidelines are not exceeded, although these single-pollutant thresholds are not comprehensive indicators of air quality. Odor events have occurred in communities near OS industrial activities, although it can be difficult to attribute events to specific pollutants or sources. Nitrogen, sulfur, polycyclic aromatic compounds (PACs), and base cations from OS sources occur in the environment, but explicit and deleterious responses of organisms to these pollutants are not as apparent across all study environments; details of biological monitoring are discussed further in other papers in this special series. However, modeling of critical load exceedances suggests that, at continued emission levels, ecological change may occur in future. Knowledge gaps and recommendations for future work to address these gaps are also presented. Integr Environ Assess Manag 2022;18:333-360. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

High-Resolution Measurements of SO2, HNO3 and HCl at the Urban Environment of Athens, Greece: Levels, Variability and Gas to Particle Partitioning

High-resolution measurements of sulfur dioxide (SO2), nitric acid (HNO3), and hydrochloric acid (HCl) were conducted in Athens, Greece, from 2014 to 2016 via a wet rotating annular denuder system paired with an ion chromatograph. Decreased mean annual levels of SO2 and HNO3 (equal to 3.3 ± 4.8 μg m−3 and 0.7 ± 0.6 μg m−3, respectively) were observed relative to the past, whereas for HCl (mean of 0.4 μg m−3 ) no such comparison was possible as the past measurements are very scarce. Regional and local emission sources regulated the SO2 levels and contributed to both the December and the July maxima of 6.6 μg m−3 and 5.5 μg m−3, respectively. Similarly, the significant enhancement at noon and during the winter nighttime was due to transported SO2 and residential heating, respectively. The oxidation of NO2 by OH radicals and the heterogeneous reactions of HNO3 on sea salt seemed to drive the HNO3 and HCl formation, respectively, whereas nighttime biomass burning affected only the former by almost 50%. During summer, the sulfate anions dominated over the SO2, in contrast to the chloride and nitrate ions that prevailed during the winter and were linked to the aerosol acidity that influences their lifetime as well as their impact on ecosystems.

Spatiotemporal Associations between PM2.5 and SO2 as well as NO2 in China from 2015 to 2018

Given the critical roles of nitrates and sulfates in fine particulate matter (PM_2.5) formation, we examined spatiotemporal associations between PM_2.5 and sulfur dioxide (SO₂) as well as nitrogen dioxide (NO₂) in China by taking advantage of the in situ observations of these three pollutants measured from the China national air quality monitoring network for the period from 2015 to 2018. Maximum covariance analysis (MCA) was applied to explore their possible coupled modes in space and time. The relative contribution of SO₂ and NO₂ to PM_2.5 was then quantified via a statistical modeling scheme. The linear trends derived from the stratified data show that both PM_2.5 and SO₂ decreased significantly in northern China in terms of large values, indicating a fast reduction of high PM_2.5 and SO₂ loadings therein. The statistically significant coupled MCA mode between PM_2.5 and SO₂ indicated a possible spatiotemporal linkage between them in northern China, especially over the Beijing–Tianjin–Hebei region. Further statistical modeling practices revealed that the observed PM_2.5 variations in northern China could be explained largely by SO₂ rather than NO₂ therein, given the estimated relatively high importance of SO₂. In general, the evidence-based results in this study indicate a strong linkage between PM_2.5 and SO₂ in northern China in the past few years, which may help to better investigate the mechanisms behind severe haze pollution events in northern China.

Ground-level air pollution changes during a boreal wildland mega-fire

The 2011 Richardson wildland mega-fire in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada had large effects on air quality. At a receptor site in the center of the AOSR ambient PM_2.5, O₃, NO, NO₂, SO₂, NH₃, HONO, HNO₃, NH₄⁺ and NO₃^- were measured during the April-August 2011 period. Concentrations of NH₃, HNO₃, NO₂, SO₂ and O₃ were also monitored across the AOSR with passive samplers, providing monthly summer and bi-monthly winter average values in 2010, 2011 and 2012. During the fire, hourly PM_2.5 concentrations >450μgm^-3 were measured at the AMS 1 receptor site. The 24-h National Ambient Air Quality Standard (NAAQS) of 35μgm^-3 and the Canada Wide Standard (CWS) of 30μgm^-3 were exceeded on 13days in May and 7days in June. During the fire emission periods, sharp increases in NH₃, HONO, HNO₃, NH₄⁺, NO₃^- and total inorganic reactive N concentrations occurred, all closely correlated with the PM_2.5 changes. There were large differences in the relative contribution of various N compounds to total inorganic N between the no-fire emission and fire emission periods. While in the absence of fires NO and NO₂ dominated, their relative contribution during the fires was ~2 fold smaller, mainly due to increased NH₃, NH₄⁺ and NO₃^-. Concentrations of HONO and HNO₃ also greatly increased during the fires, but their contribution to the total inorganic N pool was relatively small. Elevated NH₃ and HNO₃ concentrations affected large areas of northern Alberta during the Richardson Fire. While NH₃ and HNO₃ concentrations were not at levels considered toxic to plants, these gases contributed significantly to atmospheric N deposition. Generally, no significant changes in O₃ and SO₂ concentrations were detected and their ambient concentrations were below levels harmful to human health or sensitive vegetation.

Atmospheric dry deposition of sulfur and nitrogen in the Athabasca Oil Sands Region, Alberta, Canada

Due to the potential ecological effects on terrestrial and aquatic ecosystems from atmospheric deposition in the Athabasca Oil Sands Region (AOSR), Alberta, Canada, this study was implemented to estimate atmospheric nitrogen (N) and sulfur (S) inputs. Passive samplers were used to measure ambient concentrations of ammonia (NH3), nitrogen dioxide (NO2), nitric acid/nitrous acid (HNO3/HONO), and sulfur dioxide (SO2) in the AOSR. Concentrations of NO2 and SO2 in winter were higher than those in summer, while seasonal differences of NH3 and HNO3/HONO showed an opposite trend, with higher values in summer. Concentrations of NH3, NO2 and SO2 were high close to the emission sources (oil sands operations and urban areas). NH3 concentrations were also elevated in the southern portion of the domain indicating possible agricultural and urban emission sources to the southwest. HNO3, an oxidation endpoint, showed wider ranges of concentrations and a larger spatial extent. Concentrations of NH3, NO2, HNO3/HONO and SO2 from passive measurements and their monthly deposition velocities calculated by a multi-layer inference model (MLM) were used to calculate dry deposition of N and S. NH3 contributed the largest fraction of deposited N across the network, ranging between 0.70-1.25kgNha(-1)yr(-1), HNO3/HONO deposition ranged between 0.30-0.90kgNha(-1)yr(-1), and NO2 deposition between 0.03-0.70kgNha(-1)yr(-1). During the modeled period, average dry deposition of the inorganic gaseous N species ranged between 1.03 and 2.85kgNha(-1)yr(-1) and SO4-S deposition ranged between 0.26 and 2.04kgha(-1)yr(-1). Comparisons with co-measured ion exchange resin throughfall data (8.51kgSha(-1)yr(-1)) indicate that modeled dry deposition combined with measured wet deposition (1.37kgSha(-1)yr(-1)) underestimated S deposition. Gas phase NH3 (71%) and HNO3 plus NO2 (79%) dry deposition fluxes dominated the total deposition of NH4-N and NO3-N, respectively.

Collocated comparisons of continuous and filter-based PM2.5 measurements at Fort McMurray, Alberta, Canada

Collocated comparisons for three PM(2.5) monitors were conducted from June 2011 to May 2013 at an air monitoring station in the residential area of Fort McMurray, Alberta, Canada, a city located in the Athabasca Oil Sands Region. Extremely cold winters (down to approximately -40°C) coupled with low PM(2.5) concentrations present a challenge for continuous measurements. Both the tapered element oscillating microbalance (TEOM), operated at 40°C (i.e., TEOM(40)), and Synchronized Hybrid Ambient Real-time Particulate (SHARP, a Federal Equivalent Method [FEM]), were compared with a Partisol PM(2.5) U.S. Federal Reference Method (FRM) sampler. While hourly TEOM(40) PM(2.5) were consistently ~20-50% lower than that of SHARP, no statistically significant differences were found between the 24-hr averages for FRM and SHARP. Orthogonal regression (OR) equations derived from FRM and TEOM(40) were used to adjust the TEOM(40) (i.e., TEOM(adj)) and improve its agreement with FRM, particularly for the cold season. The 12-year-long hourly TEOM(adj) measurements from 1999 to 2011 based on the OR equations between SHARP and TEOM(40) were derived from the 2-year (2011-2013) collocated measurements. The trend analysis combining both TEOM(adj) and SHARP measurements showed a statistically significant decrease in PM(2.5) concentrations with a seasonal slope of -0.15 μg m(-3) yr(-1) from 1999 to 2014.

IMPLICATIONS

Consistency in PM(2.5) measurements are needed for trend analysis. Collocated comparison among the three PM(2.5) monitors demonstrated the difference between FRM and TEOM, as well as between SHARP and TEOM. The orthogonal regressions equations can be applied to correct historical TEOM data to examine long-term trends within the network.