Publications

The Canadian Federal Government promulgated new and lower NO₂ Ambient Air Quality Standards (CAAQS) that went into effect in 2020 with additional decreases scheduled for 2025. The new hourly and annual NO₂ CAAQS are 60 and 17 ppb, respectively, and the 2025 hourly and annual CAAQS are 42 and 12 ppb, respectively. The province of Alberta has also promulgated Ambient Air Quality Objectives (AAAQO) for NO₂ currently set to 159 and 24 ppb on an hourly and annual basis, respectively. The Wood Buffalo Environmental Association (WBEA) in northeastern Alberta, Canada monitors NO₂ at 21 community and industrial sites throughout the Athabasca Oil Sands Region (AOSR), for regulatory compliance using Thermo-Environmental (TEI) Model 42i Federal Reference Method (FRM) designated NO-NO₂-NOx analyzers. The 42i measures NO directly via NO-O₃ chemiluminescence, and NOx following the reduction of oxidized nitrogen to NO by a heated internal molybdenum converter. The difference between the NOx and NO channels is reported as NO₂. This study presents the results of a three-year (2018–2021) WBEA comparison of four continuous NO₂ analyzers: TEI 42i FRM; the API Model T500U cavity attenuated phase shift (CAPS) Federal Equivalent Method (FEM); a total reactive odd nitrogen analyzer (TEI Model 42i-Y); and a TEI 42i equipped with an external photolytic converter. The study showed that NO₂ data from all analyzers were highly correlated and in general agreement, with r² values (vs. the CAPS) ranging from 0.990–0.997 and slopes ranging from 0.933–0.992. Mean NO₂ concentrations over the study period ranged from 7.2–7.5 ppb. Differences between the TEI 42i, TEI 42i-Y, and PhoNO, relative to the CAPS were all positive and highly significant (p < 0.0001), based upon nonparametric tests. The potential impact from the selection of different FRM/FEM measurement methods on current and future Canadian 2025 regulatory compliance in the region is evaluated.

Oil sands developments release acidifying compounds (SO₂ and NO₂) with the potential for acidifying deposition and impacts to forest health. This article integrates the findings presented in the Oil Sands Forest Health Special Issue, which reports on the results of 20 years of forest health monitoring, and addresses the key questions asked by WBEA’s Forest Health Monitoring (FHM) Program: 1) is there evidence of deposition affecting the environment?, 2) have there been changes in deposition or effects over time?, 3) do acid deposition levels require management intervention?, 4) what are major sources of deposited substances? and 5) how can the program be improved?

Deposition of sulphur, nitrogen, base cations (BC), polycyclic aromatic compounds and trace elements decline exponentially with distance from sources. There is little evidence for acidification effects on forest soils or on understory plant communities or tree growth, but there is evidence of nitrogen accumulation in jack pine needles and fertilization effects on understory plant communities. Sulphur, BC and trace metal concentrations in lichens increased between 2008 and 2014. Source apportionment studies suggest fugitive dust in proximity to mining is a primary source of BC, trace element and organic compound deposition, and BC deposition may be neutralizing acidifying deposition. Sulphur accumulation in soils and nitrogen effects on vegetation may indicate early stages of acidification. Deposition estimates for sites close to emissions sources exceed proposed regulatory trigger levels, suggesting a detailed assessment of acidification risk close to the emission sources is warranted. However, there is no evidence of widespread acidification as suggested by recent modeling studies, likely due to high BC deposition. FHM Program evolution should include continued integration with modeling approaches, ongoing collection and assessment of monitoring data and testing for change over time, and addition of monitoring sites to fill gaps in regional coverage.

Keywords: Jack pine forest, Acid deposition, Fertilization, Ecological monitoring, Adaptive monitoring

Temporal and spatial atmospheric deposition trends of elements to the boreal forest surrounding bitumen production operations in the Athabasca Oil Sands Region (AOSR), Alberta, Canada were investigated as part of a long-term lichen bioindicator study. The study focused on eight elements (sulfur, nitrogen, aluminum, calcium, iron, nickel, strontium, vanadium) that were previously identified as tracers for the major oil sand production sources. Samples of the in situ epiphytic lichen Hypogymnia physodes were collected in 2002, 2004, 2008, 2011, 2014, and 2017 within a ~150 km radius from the center of surface oil sand production operations in the AOSR. Site-specific time series analysis conducted at eight jack pine upland sites that were repeatedly sampled generally showed significant trends of increasing lichen concentrations for fugitive dust linked elements, particularly at near-field (<25 km from a major oil sands production operation) sample locations. Multiple regional scale geostatistical models were developed and evaluated to characterize broad-scale changes in atmospheric deposition based on changes in H. physodes elemental concentrations between 2008 and 2014. Empirical Bayesian kriging and cokriging lichen element concentrations with oil sands mining, bitumen upgrading, coke materials handling, and limestone quarry/crushing influence variables produced spatial interpolation estimates with the lowest validation errors. Gridded zonal mean lichen element concentrations were calculated for the two comprehensive sampling years (2008, 2014) and evaluated for spatial and temporal change. Lichen sulfur concentrations significantly increased in every grid cell within the domain with the largest increases (44–88%) in the central valley in close proximity to the major surface oil sand production operations, while a minor nitrogen concentration decrease (−20%) in a single grid cell was observed. The areal extent of fugitive dust element deposition generally increased with significantly higher deposition to lichens restricted to the outer grids of the enhanced deposition field, reflecting new and expanding surface mining activity.

Keywords: Lichen biomonitoring, Cokriging, Hypogymnia physodes, Atmospheric deposition, Time series analysis, Wood Buffalo Environmental Association

The oil extraction industry and human activity in north eastern Alberta has been growing steadily since the 1960’s and is a source of air pollution. In the late 1990’s the Wood Buffalo Environmental Association was established to monitor air quality for both public and environmental health. A primary environmental concern was soil acidification caused by sulfur (S) and nitrogen (N) deposition. A network of forest health monitoring (FHM) sites was established in dry jack pine ecosystems to serve as an early indicator of negative impacts. A sampling campaign was executed in 2011 and this study examines soil properties and foliar nutrients in the context of measured and modeled acid deposition. Total N (TN), SO₄²⁻, pH, base cation to aluminum ratio (BC:Al), and base saturation (% BS) are reported for the organic layer (LFH) and 3 depths in the mineral soil, while foliar nutrients were analysed from current annual growth in jack pine needles. Atmospheric deposition of S, N, BC, and potential acid input (PAI) in the study area was recently provided by Edgerton et al. (2020) and soil and foliar chemistry was evaluated based on deposition estimates and measurements. Inverse distance weighting was used to examine spatial patterns and regression analysis was used to quantify relationships between variables. The results indicated that S deposition is spatially correlated with foliar SO₄²⁻ concentration, and LFH SO₄²⁻, but not mineral topsoil (0–5 cm) SO₄²⁻. Nitrogen deposition was spatially correlated with foliar N concentration, but not LFH or topsoil TN indicating potential uptake by the foliage or rapid uptake by roots in the LFH layer. High BC deposition in the same areas with the highest potential acid inputs (PAI) did not correlate significantly with changes in soil pH. However, LFH pH was significantly related to dry NH₃ deposition, which has not been reported previously and requires further investigation.

Keywords: Industrial air pollutants, SO_2, NO_X, Inverse distance weighting, Spatial analysis, Forest health, Fugitive dust, Potential acid input

Atmospheric acid deposition is of major concern in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada, which is home to the third largest oil reserve in the world. After decades of oil sands production in the AOSR, the potential impact of deposition on forest health, including tree growth and understory biodiversity, is still not clear. We evaluated the relationship of modelled/interpolate atmospheric deposition of nitrogen (N), sulphur (S), base cations (BC), and derived potential acid input (PAI) from surface oil sands mining with: (1) the radial growth (i.e. basal area increment; BAI) of jack pine (Pinus banksiana Lamb.) trees using data from two decadal time periods, prior to (1957–1966) and during (2001−2010) active oil sands development in the AOSR; and (2) forest understory vegetation (abundance, diversity, and composition), which is an important component of forest biodiversity. BAI of jack pine trees varied with N, S, and BC deposition between the two time periods, and with the direction of the site relative to main emission sources. Growth was higher in areas close to the oil sands surface mining operations prior to and after oil sands development. BAI was also positively related to atmospheric deposition in the recent period, but these relationships were weaker in the active period versus the non-active period. Understory vegetation – including vascular plant cover, richness, and diversity – increased in relation to modelled atmospheric N and S deposition. There was limited correlation between soil pH or the BC:Al ratio (indicators of soil acidification) and BAI and understory vegetation responses. No evidence was found for detrimental effects of atmospheric emissions (and subsequent deposition) from oil sands production on tree growth or forest understory vegetation. The results, if anything, suggest a fertilization effect due to enhanced atmospheric deposition of nitrogen compounds.

Keywords: Basal area increment, Jack pine, Nitrogen deposition, Nitrogen fertilization, Oil sands development, Soil-mediated acidification, Sulphur deposition, Understory vegetation

The expansion of oil sands resource development in the Athabasca Oil Sands Region in the early 1990’s led to concerns regarding the potential ecological and health effects of increased emissions and deposition of acidic substances. Conditions attached to a 1994 approval for an oil sands facility expansion led to the creation of the Wood Buffalo Environmental Association, and its Terrestrial Environmental Effects Monitoring committee. This multi-stakeholder body was tasked with development and operation of an environmental (forest health) monitoring program for the detection of ecological responses to atmospheric emissions and deposition. Initially focused on acid deposition monitoring, jack pine forest, growing on sandy soils with limited acid buffering capacity, was selected as the receptor system. An initial set of 10 monitoring locations was established using the Canadian Acid Rain Network Early Warning System methodology (since increased to 27, with three lost to development). Ecological monitoring is on a 6-year cycle, with concurrent measures of soil, needle and lichen chemistry, and tree and understory condition, together with ongoing measurements of air quality and atmospheric deposition. Because jack pine forest edges facing the emissions sources were expected to be more exposed to acidic emissions, evaluation of stand edge monitoring locations began in 2008.

A comprehensive filter-based particulate matter polycyclic aromatic hydrocarbon (PAH) source apportionment study was conducted at the Wood Buffalo Environmental Association Bertha Ganter-Fort McKay (BGFM) community monitoring station from 2014 to 2015 to quantify ambient concentrations and identify major sources. The BGFM station is located in close proximity to several surface oil sands production facilities and was previously found to be impacted by their air emissions. 24-hour integrated PM_2.5 and PM_10–2.5 samples were collected on a 1-in-3-day schedule yielding 108 complete organic/inorganic filter sets for source apportionment modeling. During the study period PM_2.5 averaged 8.6 ± 11.8 μg m⁻³ (mean ± standard deviation), and PM_10–2.5 averaged 8.5 ± 9.5 μg m⁻³. Wind regression analysis indicated that the oil sands production facilities were significant sources of PM_2.5 mass and black carbon (BC), and that wildland fires were a significant source of the highest PM_2.5 (>10 μg m⁻³) and BC events. A six-factor positive matrix factorization (PMF) model solution explained 95% of the measured PM_2.5 and 78% of the measured ΣPAH. Five sources significantly contributed to PM_2.5 including: Biomass Combustion (3.57 μg m⁻³; 40%); Fugitive Dust (1.86 μg m⁻³; 28%); Upgrader Stack Emissions (1.44 μg m⁻³; 21%); Petrogenic PAH (1.20 μg m⁻³; 18%); and Transported Aerosol (0.43 μg m⁻³ and 6%). However, the analysis indicated that only the pyrogenic PAH source factor significantly contributed (78%) to the measured ΣPAH. A five-factor PMF model dominated by fugitive dust sources explained 98% of PM_10–2.5 mass and 86% of the ΣPAH. The predominant sources of PM_10–2.5 mass were (i) Haul Road Dust (4.82 μg m⁻³; 53%), (ii) Mixed Fugitive Dust (2.89 μg m⁻³; 32%), (iii) Fugitive Oil Sand (0.88 μg m⁻³; 10%), Mobile Sources (0.23 μg m⁻³; 2%), and Organic Aerosol (0.06 μg m⁻³; 1%). Only the Organic Aerosol source significantly contributed (86%) to the measured ΣPAH.

Keywords: Fugitive dust, Biomass combustion, PM_2.5, PM₁₀ PAHs, PACs

Trace gas, particulate matter and deposition data collected in the Athabasca Oil Sands Region (AOSR) from 2000 to 2017 were evaluated as part of a broad scientific programmatic review. Results showed significant spatial patterns and temporal trends across the region. Concentrations of reactive gases were highest near the center of surface oil sands production operations and decreased towards the edges of the monitoring domain by factors of 8, 20, 4 and 3 for SO₂, NO₂, HNO₃ and NH₃, respectively. 18 of 30 sites showed statistically significant (p < 0.05) negative trends in SO₂ concentrations suggesting an ~40% decrease since 2000. In contrast, only 2 of 30 sites showed statistically significant temporal trends (1 positive, 1 negative) for NO₂. NH₃ data showed (i) intermittent wildfire impacts, and (ii) high seasonality, with low concentrations during winter and significantly higher values during the summer. PM₁₀ measurements were more limited, but also showed significant spatio-temporal variability. Comparison of PM₁₀ and PM_2.5 data showed that >80% of SO₄²⁻ was in the PM_2.5 fraction, while > 60% of Ca²⁺, Mg²⁺, Na⁺ and Cl⁻ were in the PM_10-2.5 fraction. Ion balances of both PM₁₀ and PM_2.5 contained cation excesses at near-field oil sand sites, but PM_2.5 samples at forest health sites >20 km from surface production locations contained anion excesses. Monthly average concentrations of PM₁₀ ions showed peak Ca²⁺ during March-April to November, but peak SO₄²⁻, NH₄⁺ and NO₃⁻ from November-March. Deposition estimates showed rapid declines as a function of distance to oil sand operations. Estimated total N and total S deposition to forest health monitoring sites ranged from 2.0 to 5.7 kg ha⁻¹ a⁻¹ and 2.1–14.0 kg ha⁻¹ a⁻¹, respectively. Potential acid input (PAI) ranged from −0.46 to 0.79 keq ha⁻¹ a⁻¹ and was mostly 0.1–0.2 keq ha⁻¹ a⁻¹ throughout the domain, except for two clusters of sites near oil sand operations.

Keywords: Sulfur, Nitrogen, Base cations, Atmospheric deposition, Nitric acid, Ammonia, Boreal forest, Oil sands

Ambient air particulate matter (PM) was collected at the Wood Buffalo Environmental Association Bertha Ganter Fort McKay monitoring station in the Athabasca Oil Sand Region (AOSR) in Alberta, Canada from February 2010 to July 2011 as part of an air quality source assessment study. Daily 24-hour duration fine (PM_2.5) and coarse (PM_10–2.5) PM was collected using a sequential dichotomous sampler. 100 pairs of PM_2.5 and PM_10–2.5 were selected for lead (Pb) concentration and isotope analysis. Pb isotope and concentration results from 250 epiphytic lichen samples collected as far as 160 km from surface mining operations in 2008, 2011, and 2014 were analyzed to examine longer term spatial variations in Pb source contributions. A key finding was recognition of thorogenic ²⁰⁸Pb from eastern Asia in the springtime in the PM_2.5 in 2010 and 2011. ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb isotope ratios were used in a three-component mixing model to quantify local, regional, and global Pb sources in the PM and lichen data sets. 47 ± 3% of the Pb in the PM_2.5 at AMS-1 was attributed to sources from eastern Asia. Combined results from PM_10–2.5 and PM_2.5 indicate PM_2.5 Pb contributions from eastern Asia (34%) exceed local AOSR sources of PM_2.5 Pb (20%), western Canada sources of PM_2.5 Pb (19%), and PM_10–2.5 Pb from fugitive dust including oil sands (14%), tailings (10%), and haul roads (3%). The lichen analysis indicates regional sources contribute 46% of the Pb, local sources 32%, and global sources 22% over the 2008–2014 timeframe. Local sources dominate atmospheric Pb deposition to lichens at near field sites (0–30 km from mining operations) whereas regional Pb sources are prevalent at distal sites (30–160 km). The Pb isotope methodology successfully quantified trans-Pacific transport of Pb to the AOSR superimposed over the aerosol footprint of the world’s largest concentration of bitumen mining and upgrading facilities.

Keywords: Pb isotopes, Particulate matter, Fugitive dust, Eastern Asian Pb sources, Global transport of aerosols

The sources and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) atmospheric deposition in the boreal forests surrounding bitumen production operations in the Athabasca Oil Sands Region (AOSR), Alberta, Canada were investigated as part of a 2014 passive in-situ bioindicator source apportionment study. Epiphytic lichen species Hypogymnia physodes samples (n = 127) were collected within a 150 km radius of the main surface oil sand production operations and analyzed for total sulfur, total nitrogen, forty-three elements, twenty-two PAHs, ten groups of C1-C2-alkyl PAHs and dibenzothiophenes (polycyclic aromatic compounds; PACs), five C1- and C2-alkyldibenzothiophenes, and retene. The ΣPAH + PAC in H. physodes ranged from 54 to 2778 ng g⁻¹ with a median concentration of 317 ng g⁻¹. Source apportionment modeling found an eight-factor solution that explained 99% of the measured ΣPAH + PAC lichen concentrations from four anthropogenic oil sands production sources (Petroleum Coke, Haul Road Dust, Stack Emissions, Raw Oil Sand), two local/regional sources (Biomass Combustion, Mobile Source), and two lichen biogeochemical factors. Petroleum Coke and Raw Oil Sand dust were identified as the major contributing sources of ΣPAH + PAC in the AOSR. These two sources accounted for 63% (43.2 μg g⁻¹) of ΣPAH + PAC deposition to the entire study domain. Of this overall 43.2 μg g⁻¹ contribution, approximately 90% (39.9 μg g⁻¹) ΣPAH + PAC was deposited within 25 km of the closest oil sand production facility. Regional sources (Biomass Combustion and Mobile Sources) accounted for 19% of ΣPAH + PAC deposition to the entire study domain, of which 46% was deposited near-field to oil sand production operations. Source identification was improved over a prior lichen-based study in the AOSR through incorporation of PAH and PAC analytes in addition to inorganic analytes.

Keywords: Lichen, Hypogymnia physodes, Biomonitor, Polycyclic aromatic compounds, Atmospheric deposition