Athabasca Bituminous Sands Region Research Articles

Spatio-temporal variations in dissolved trace elements in peat bog porewaters impacted by dust inputs from open-pit mining activities in the Athabasca Bituminous Sands (ABS) region

Considerable volumes of dust are generated from open-pit bitumen mining operations in northern Alberta, Canada. The reactive mineral phases of these dust particles can potentially dissolve in acidic (pH < 4) bog waters. Their dissolution could release trace elements (TEs), which could eventually alter these bog ecosystems. The impact of dust dissolution on the abundance of TEs in the dissolved (<0.45 μm) fraction of porewaters from excavated pits (30–40 cm deep) in the ombrogenic zone of five peatlands was evaluated. Porewaters were collected from four bogs situated within 70 km of mines and upgraders in the Athabasca Bituminous Sands (ABS) region, Alberta, Canada, and from a reference bog situated 264 km away. Over two consecutive years, the dissolved concentrations of some conservative (Al, Th, Y) and mobile lithophile elements (Fe, Li, Mn, Sr), as well as the metals enriched in bitumen (V, Ni, Mo), all increased with proximity to the mining area, in the ABS region. These trends reflect the observed increase in dust deposition with proximity to the mining area from independent studies of snow, lichens, and Sphagnum moss. Contrarily, the impact of dust dissolution on the concentration of potentially toxic TEs (As, Cd, Pb, Sb, and Tl) was negligible. Thus, the elements which are more abundant in the porewaters near industry are either ecologically benign (e.g. Li and Sr) or essential micronutrients (e.g. Fe, Mn, Ni, and Mo). Manganese was the only element which was enriched by more than 10x at all sites near the mining area, compared to its concentration at the reference site. The enrichments of all other elements were <10x, indicating that anthropogenic dust emissions from mining areas have had only a modest effect on the TEs abundance in peat porewaters.

Spatial variation and chemical reactivity of dusts from open-pit bitumen mining using trace elements in snow

The chemical reactivity of trace elements (TEs) in dusts from bitumen mining, upgrading and related industrial activities in the Athabasca Bituminous Sands region (ABS), Alberta, Canada, was evaluated using the acid-soluble fraction of snow. Samples were collected at 14 sites along the Athabasca River (AR) and its tributaries, and at 3 remote locations. Following metal-free, ultra-clean procedures for processing and analysis, samples were leached with nitric acid (pH < 1), filtered (<0.45 μm), and analyzed using ICP-MS. Insoluble particles (>0.45 μm) were examined using SEM-EDS. Along the river, acid-soluble concentrations of TEs varied by 6 orders of magnitude, from 1 mg/L (Al) to less than 1 ng/L (Tl). Conservative (Al, Y, La, Th) and mobile (Li, Be, Cs, Sr) lithophile elements, those enriched in bitumen (V, Ni, Mo), and potentially toxic chalcophile elements (As, Cd, Pb, Sb, Tl) showed considerable spatial variation. Normalizing the concentrations of TEs in samples collected near industry to the corresponding concentrations in snow from the reference site (UTK), resulted in enrichments of V and most of the lithophile elements. Dust reactivity, quantified as the ratio of acid-soluble to total concentrations, was less than 50% suggesting limited bioaccessibility. The large differences in behaviour between Cd and Pb versus Ni and V could be due to the occurrence of the former pair in carbonate or sulfide minerals, versus acid-insoluble petcoke particles for the latter couple. Spatial variations in the reactivity of TEs most likely reflect the range in diversity and chemical stability of dust particles, and variations in their abundance in primary source areas. The leaching conditions employed here are extreme (pH < 1) and intended to identify an upper limit of chemical reactivity, with far less dust dissolution expected when these dusts encounter natural waters of the area which range in pH from 4 to 8.

Size-fractionation of trace elements in dusty snow from open pit bitumen mines and upgraders: collection, handling, preparation and analysis of samples from the Athabasca bituminous sands region of Alberta, Canada

A robust sample handling, processing and analytical method was developed for reliable determination of 40 TEs in dusty snow. The “dissolved” TEs in snow from the ABS region were extremely low, and TEs were almost exclusively found in the particulate fraction.

Contemporary and Historical Atmospheric Deposition of Arsenic and Selenium in the Athabasca Bituminous Sands Region.

Selenium (Se) is one of the trace elements that is enriched in bitumen. To assess the importance of atmospheric Se deposition from mining and upgrading of bituminous sands in northern Alberta, Canada, Sphagnum moss was obtained from 25 bogs near industrial operations. The average Se concentration in moss near industries (58 ± 13 μg/kg; n = 75) was greater than in remote sites in Alberta (29-50 μg/kg), but comparable to bogs in central regions of the province and lower than bogs in southern Ontario (121-244 μg/kg) or the west and east coasts (230-285 μg/kg). In bog vegetation and peat, arsenic (As) concentrations and accumulation rates are 10 times greater at the industrial site (MIL) compared to the control site (UTK), but this is proportional to the differences in scandium (a surrogate for mineral matter concentrations), which points to dust as the predominant As source. An age-dated peat core collected near industries revealed that both Se and As deposition have declined in recent years. A peat core from UTK provided a record of atmospheric deposition dating back over 2700 years, indicating that As and Se deposition in northern Alberta increased considerably in the early 19th century and then went into decline during ∼1950-1970.

Atmospheric Hg accumulation rates determined using Sphagnum moss from ombrotrophic (rain-fed) bogs in the Athabasca Bituminous Sands region of northern Alberta, Canada

Abstract Sphagnum moss was collected from 22 ombrotrophic (rain-fed) bogs near open pit mines and upgraders within the Athabasca Bituminous Sands (ABS) region of Alberta (AB). Mercury was quantified using two approaches: sector-field ICP-MS of acid digests, and a Direct Mercury Analyser (DMA) for solid samples. Using ICP-MS, the mean Hg concentration in moss from the ABS region (34.7 ± 1.5 µg/kg, n = 75) was significantly greater than the control site, Utikuma (26.7 ± 4.0 µg/kg, n = 3). Using DMA, the mean Hg concentration in moss from the ABS region (26.2 ± 0.9 µg/kg, n = 71) was significantly lower than the control site (28.5 ± 1.3 µg/kg, n = 6). These contradictory findings illustrate the challenges associated with comparing the results of two analytical methods, especially given the similarity in Hg concentrations between industrial and background sites, Similar Hg concentrations were also found in Sphagnum moss from two other bogs in AB which are far removed from the ABS region. The Hg concentrations in Sphagnum from the ABS bogs are well below the range found in bog vegetation collected earlier in eastern Canada, and comparable to the lowest values (5th percentile) reported for forest moss collected in 2015 from Norway and Sphagnum moss sampled in 2008 from northern Sweden. Given the rates of Sphagnum accumulation in the ABS region (ca. 215 g/m2/yr), Hg accumulation rates there were 5.8–7.5 µg/m2/yr versus 5.7–6.1 µg/m2/yr at the control site (UTK); these are at the upper limit of the range in pre-anthropogenic rates of Hg accumulation for peat from European bogs. Sphagnum moss is abundant in Canada and found in bogs from coast to coast, offering an opportunity to obtain quantitative information on atmospheric Hg deposition to terrestrial ecosystems from natural as well as anthropogenic sources.

Trace elements in berries collected near upgraders and open pit mines in the Athabasca Bituminous Sands Region (ABSR): Distinguishing atmospheric dust deposition from plant uptake

There are ongoing concerns regarding environmental emissions of trace elements (TEs) from bitumen mining and upgrading in the Athabasca Bituminous Sands Region (ABSR). Depending on their physical and chemical forms, elevated concentrations of potentially toxic TEs in berries could pose a health risk to local indigenous communities because native fruits are an important part of their traditional diet. The objective of this study was to distinguish between aerial deposition of TEs versus plant uptake, in cranberries, lingonberries, and blueberries growing in the ABSR. The concentrations of TEs were determined using ICP-MS in the metal-free, ultraclean SWAMP lab at the University of Alberta. The spatial variation in abundance of conservative, lithophile elements such as Y in berries resembles the published map of dust deposition rates obtained using Sphagnum moss. The presence of dust particles on the surface of the berries near open pit mines and upgraders was confirmed using SEM. Elements which show strong, positive correlation with Y include Al, Cr, Pb, U, and V; these are supplied mainly by dust. Elements which are largely independent of Y concentrations include Ba, Cd, Cu, Mn, Mo, Ni, Rb, Sr, and Zn; these are obtained primarily by plant uptake from soil. The concentrations of elements associated with dust were considerably reduced after washing with water, but the elements independent of dust inputs were unaffected. Elements which are supplied almost exclusively by dust (e.g. Y) are more abundant in berries from the ABS region (2 to 24 times), compared to berries from remote locations.

Testate amoeba records indicate regional 20th-century lowering of water tables in ombrotrophic peatlands in central-northern Alberta, Canada.

Testate amoebae are abundant in the surface layers of northern peatlands. Analysis of their fossilized shell (test) assemblages allows for reconstructions of local water-table depths (WTD). We have reconstructed WTD dynamics for five peat cores from peatlands ranging in distance from the Athabasca bituminous sands (ABS) region in western Canada. Amoeba assemblages were combined with plant macrofossil records, acid-insoluble ash (AIA) fluxes and instrumental climate data to identify drivers for environmental change. Two functional traits of testate amoebae, mixotrophy and the tendency to integrate xenogenic mineral matter in test construction, were quantified to infer possible effects of AIA flux on testate amoeba presence. Age-depth models showed the cores each covered at least the last ~315years, with some spanning the last millennium. Testate amoeba assemblages were likely affected by permafrost development in two of the peatlands, yet the most important shift in assemblages was detected after 1960 CE. This shift represents a significant apparent lowering of water tables in four out of five cores, with a mean drop of ~15cm. Over the last 50years, assemblages shifted towards more xerophilous taxa, a trend which was best explained by increasing Sphagnum s. Acutifolia and, to a lesser extent, mean summer temperature. This trend was most evident in the two cores from the sites located farthest away from the ABS region. AIA flux variations did not show a clear effect on mineral-agglutinating taxa, nor on S.s.Acutifolia presence. We therefore suggest the drying trend was forced by the establishment of S.s.Acutifolia, driven by enhanced productivity following regional warming. Such recent apparent drying of peatlands, which may only be reconstructed by appropriate indicators combined with high chronological control, may affect vulnerability to future burning and promote emissions of CO2 .

Selenium and sulphur in Athabasca bituminous sands mineral and bitumen fractions

There is increasing environmental concern regarding the emission of selenium (Se) from mining and upgrading of bitumen extracted from the Athabasca bituminous sands (ABS) in northern Alberta, Canada. However, there remains a lack of high quality analytical data for Se in this massive hydrocarbon reserve. Accurate analytical determinations of Se in bitumen from ABS are an important first step toward understanding its potential to be emitted to the environment. This has been a challenge due to the low abundance of Se combined with the preponderance of entrained mineral material (sand, clay) and the generally inadequate sensitivity of analytical methods used in the past. To overcome these issues, samples of ABS ores (McMurray Formation) underwent a toluene extraction procedure under ultra-clean lab conditions to separate bitumen from mineral particles. Separated bitumen, residual mineral material, and bulk ores were then subjected to acid-digestion and analysis using inductively coupled plasma sector-field mass spectrometry (ICP-SFMS) as well as hydride generation atomic fluorescence spectroscopy (HG-AFS). Unlike many other potentially toxic trace elements (Ag, As, Be, Cd, Cu, Pb, Sb, Tl and Zn) which exist almost exclusively in the mineral fraction, Se was found primarily (ca. 80%) in the organic (bitumen) fraction. Sulphur was determined in the same acid digests using both ICP-SFMS and inductively coupled plasma-optical emission spectroscopy (ICP-OES) and it too, was found almost exclusively in the bitumen fraction. Despite the limited number of samples available to our study, the positive, linear correlation between Se and S concentrations in bitumen suggests that S concentrations can be used as a guide to estimate their Se content. Given that Se is found mainly in the organic fraction of the ABS, there is considerable potential for mobilization of this element during upgrading and refining. The analytical methods successfully employed here have sufficient sensitivity to support studies of Se contamination of environmental media in the ABS region.

Reconstructing Past Rates of Atmospheric Dust Deposition in the Athabasca Bituminous Sands Region Using Peat Cores from Bogs

AbstractOpen‐pit mining of the Athabasca Bituminous Sands generates considerable quantities of mineral dusts, but there is no published record of the amount of material deposited in the surrounding environment via the atmosphere since the industry began in 1967. Contemporary and past rates of atmospheric dust deposition were reconstructed using age‐dated peat cores (210Pb and 14C) collected from five bogs in the vicinity of mines and upgraders and from two bogs far removed from industrial activities. The main objective of this study was to quantify the impact of industry on dust emissions, and to do this, the variation in natural “background” rates of mineral matter accumulation also had to be determined. A second objective was to characterize the size, mineralogical composition, and morphology of the particulate matter emitted to better understand potential environmental consequences of dust emissions.The concentrations of acid insoluble ash and Th (a surrogate for insoluble mineral matter) were determined to calculate dust accumulation rates. Scanning electron microscopy with energy‐dispersive X‐ray analysis failed to reveal much variation in mineralogical composition, but near industry, the size of the particles was more variable. The abundance of fly ash particles increased with depth, which suggests that emissions from upgrader stacks may have declined over time. A comparison of acid‐insoluble ash inventories with the pH of the porewaters suggests that the acid‐soluble ash fraction of the dusts deposited may have impacted the chemical composition of the bog waters. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Sphagnum Moss as an Indicator of Contemporary Rates of Atmospheric Dust Deposition in the Athabasca Bituminous Sands Region.

Sphagnum moss was collected from ombrotrophic (rain-fed) peat bogs to quantify dust emissions from the open-pit mining and upgrading of Athabasca bituminous sands (ABS). A total of 30 bogs were sampled in the ABS region, and 5 were sampled in central Alberta. Ash was separated into the acid-insoluble ash (AIA) and acid-soluble ash (ASA) fractions using HCl. The AIA concentrations increase toward industry from 0.4 ± 0.5% to 4.7 ± 2.0% over a distance of 30 km; the control site at the Utikuma Region Study Area (URSA) yielded 0.29 ± 0.07% (n = 30). Mass accumulations rates showed similar spatial variation. The morphology and mineralogy of the AIA particles were studied using scanning electron microscopy and energy-dispersive X-ray analysis and the particle size distributions using optical methods. Particle size was more variable in moss closer to industry. Major ions in the ASA fraction showed elevated accumulation rates of Ca, K, Fe, Mg, P, and S, with P being up to 5 times greater in samples nearest industry compared to those in distal locations. Given that P has been regarded as the growth-limiting nutrient in bogs, fertilization of nutrient-poor ecosystems, such as these from fugitive emissions of dusts from open-pit mining, may have long-term ecological ramifications.

Peat Bogs Document Decades of Declining Atmospheric Contamination by Trace Metals in the Athabasca Bituminous Sands Region.

Peat cores were collected from five bogs in the vicinity of open pit mines and upgraders of the Athabasca Bituminous Sands, the largest reservoir of bitumen in the world. Frozen cores were sectioned into 1 cm slices, and trace metals determined in the ultraclean SWAMP lab using ICP-QMS. The uppermost sections of the cores were age-dated with 210Pb using ultralow background gamma spectrometry, and selected plant macrofossils dated using 14C. At each site, trace metal concentrations as well as enrichment factors (calculated relative to the corresponding element/Th ratio of the Upper Continental Crust) reveal maximum values 10 to 40 cm below the surface which shows that the zenith of atmospheric contamination occurred in the past. The age-depth relationships show that atmospheric contamination by trace metals (Ag, Cd, Sb, Tl, but also V, Ni, and Mo which are enriched in bitumen) has been declining in northern Alberta for decades. In fact, the greatest contemporary enrichments of Ag, Cd, Sb, and Tl (in the top layers of the peat cores) are found at the control site (Utikuma) which is 264 km SW, suggesting that long-range atmospheric transport from other sources must be duly considered in any source assessment.

Size-resolved Pb distribution in the Athabasca River shows snowmelt in the bituminous sands region an insignificant source of dissolved Pb

Lead (Pb) is a metal of special importance because of its long history of commercial and industrial use, global atmospheric contamination accelerated by the use of gasoline additives, and health effects, with children being especially vulnerable. Global atmospheric Pb pollution reached its zenith in the 1970’s, but subsequent impacts on freshwater aquatic systems are poorly understood. Employing metal-free sampling and handling protocols, we show that snowmelt from the Athabasca bituminous sands region is an insignificant source of dissolved Pb to the Athabasca River (AR). Total Pb in the AR is low, and almost entirely in particulate form. Lead in the suspended solids in the AR exactly follows thorium (Th), a conservative lithophile element, and a linear regression of Pb against Th (Pb = 1.6 × Th + 0.0; R2 = 0.99) yields a slope identical to the Pb/Th ratio in the Upper Continental Crust. In the “dissolved” fraction, the Pb/Th ratio is equivalent to that of deep, open ocean seawater; and dominated by colloidal forms. Taken together, these results show that the efforts of recent decades to reduce anthropogenic Pb to the environment have been successful: Pb loading to the river can now be explained predominantly by natural processes, namely erosion plus chemical weathering.

Dust is the dominant source of “heavy metals” to peat moss (Sphagnum fuscum) in the bogs of the Athabasca Bituminous Sands region of northern Alberta

Sphagnum fuscum was collected from twenty-five ombrotrophic (rain-fed) peat bogs surrounding open pit mines and upgrading facilities of Athabasca Bituminous Sands (ABS) in northern Alberta (AB) in order to assess the extent of atmospheric contamination by trace elements. As a control, this moss species was also collected at a bog near Utikuma (UTK) in an undeveloped part of AB and 264km SW of the ABS region. For comparison, this moss was also collected in central AB, in the vicinity of the City of Edmonton which is approximately 500km to the south of the ABS region, from the Wagner Wetland which is 22km W of the City, from Seba Beach (ca. 90km W) and from Elk Island National Park (ca. 45km E). All of the moss samples were digested and trace elements concentrations determined using ICP-SMS at a commercial laboratory, with selected samples also analyzed using instrumental neutron activation analysis at the University of Alberta.The mosses from the ABS region yielded lower concentrations of Ag, As, Bi, Cd, Cu, Pb, Sb, Tl, and Zn compared to the moss from the Edmonton area. Concentrations of Ni and Mo in the mosses were comparable in these two regions, but V was more abundant in the ABS samples. Compared with the surface vegetation of eight peat cores collected in recent years from British Columbia, Ontario, Quebec and New Brunswick, the mean concentrations of Ag, As, Bi, Cd, Cu, Mo, Ni, Pb, Sb, Tl and Zn in the mosses from the ABS region are generally much lower. In fact, the concentrations of these trace elements in the samples from the ABS region are comparable to the corresponding values in forest moss from remote regions of central and northern Norway.Lithophile element concentrations (Ba, Be, Ga, Ge, Li, Sc, Th, Ti, Zr) explain most of the variation in trace metal concentrations in the moss samples. The mean concentrations of Th and Zr are greatest in the moss samples from the ABS region, reflecting dust inputs to the bogs from open pit mines, aggregate quarries, and gravel roads. Linear regressions of V, Ni, and Mo (elements enriched in bitumen) versus Sc (a conservative, lithophile element) show excellent correlations in the mosses from the ABS region, but this is true also of Ag, Pb, Sb and Tl: thus, most of the variation in the trace metal concentrations can be explained simply by the abundance of dust particles on the plants of this region. Unlike the moss samples from the ABS region and from UTK where Pb/Sc ratios resemble those of crustal rocks, the moss samples from the other regions studied yielded much greater Pb/Sc ratios implying significant anthropogenic Pb contributions at these other sites.

Sphagnum mosses from 21 ombrotrophic bogs in the athabasca bituminous sands region show no significant atmospheric contamination of "heavy metals".

Sphagnum moss was collected from 21 ombrotrophic (rain-fed) peat bogs surrounding open pit mines and upgrading facilities of Athabasca bituminous sands in Alberta (AB). In comparison to contemporary Sphagnum moss from four bogs in rural locations of southern Germany (DE), the AB mosses yielded lower concentrations of Ag, Cd, Ni, Pb, Sb, and Tl, similar concentrations of Mo, but greater concentrations of Ba, Th, and V. Except for V, in comparison to the "cleanest", ancient peat samples ever tested from the northern hemisphere (ca. 6000-9000 years old), the concentrations of each of these metals in the AB mosses are within a factor of 3 of "natural, background" values. The concentrations of "heavy metals" in the mosses, however, are proportional to the concentration of Th (a conservative, lithophile element) and, therefore, contributed to the plants primarily in the form of mineral dust particles. Vanadium, the single most abundant trace metal in bitumen, is the only anomaly: in the AB mosses, V exceeds that of ancient peat by a factor of 6; it is therefore enriched in the mosses, relative to Th, by a factor of 2. In comparison to the surface layer of peat cores collected in recent years from across Canada, from British Columbia to New Brunswick, the Pb concentrations in the mosses from AB are far lower.

Toxicity beyond the Lung: Connecting PM 2.5 , Inflammation, and Diabetes

Exposure to fine particulate matter (PM2.5) has been associated with increased risk of heart disease,1 insulin resistance (IR),2 and diabetes,3 all conditions that are characterized by inflammation.4 Experimental data suggest a high-fat diet2 may exacerbate the health effects of inhaled PM2.5; obese people also appear to be at increased risk.1 In this issue of EHP, investigators tease out some of the complex cellular mechanisms that could explain how PM2.5 may work with a high-fat diet to cause IR.5 Some of the authors previously reported that mice breathing PM2.5 and eating a high-fat diet developed IR, systemic inflammation, and increased abdominal fat, compared with mice eating the same diet but breathing filtered air.2 For the current study, the investigators focused on CCR2, a protein that recruits innate immune cells to insulin-sensitive tissues such as visceral fat and the liver, where it induces the inflammation characteristically seen in animal models of obesity and type 2 diabetes.6 They compared wild-type mice that produce CCR2 with “knockout” (CCR2–/–) mice that don’t. All the mice were fed a high-fat diet and then for 17 weeks were exposed to either filtered air or air containing 117 µg/m3 of PM2.5. Among the key findings, PM2.5 exposure was associated with increased IR and increased levels of liver lipids in the wild-type mice. The elevated liver lipids resulted from a rise in SREBP-1c activity5; this protein helps regulate fatty acid synthesis.7 In contrast, liver lipid levels and SREBP-1c activity in CCR2–/– mice were equivalent whether the mice were exposed to PM2.5 or breathing filtered air.5 IR is also characterized by abnormal insulin signaling through the AKT pathway. Reduced phosphorylation of this enzyme is associated with inflammation.8 The researchers found that phosphorylation of AKT was reduced in wild-type mice exposed to PM2.5 but unchanged in CCR2–/– mice. PM2.5 exposure also was associated with higher levels of inflammatory F4/80 macrophages in visceral fat stores, but only in wild-type mice.5 The important message in all these findings is that PM2.5 recruits inflammatory cells via CCR2-dependent mechanisms. “This mechanism directly ties a known inflammatory mechanism in the pathogenesis of type 2 diabetes to exposure to environmental air pollution,” says study leader Sanjay Rajagopalan, division head for cardiology at the University of Maryland Medical Center. The protein CCR2 is involved in the inflammation that characterizes animal models of obesity and type 2 diabetes. Rajagopalan says the inflammatory damage likely creates a vicious cycle that can also contribute to cardiovascular disease and obesity. “We should look more closely at these kinds of associations in human epidemiological studies,” he says. PM2.5 is generated by vehicle exhaust, burning wood and coal, and industrial processes.9 Annual PM2.5 levels in cities in China, India, and Latin America can average 100–150 µg/m3, comparable to the PM2.5 exposure in this study.2 “It’s long been suspected that the immune system played a major role in ‘carrying’ the toxicity of air pollutants beyond the lung,” says Matthew Campen, an associate professor at the University of New Mexico College of Pharmacy, who was not involved in the study. The results by Rajagopalan’s team strongly support the role of the innate immune system in mediating PM2.5 toxicity in tissues far from the lung. The results, Campen says, also suggest that PM2.5 pollution could worsen cardiometabolic syndromes brought on by an unhealthy diet and lifestyle. “This public health burden may be offset by anti-inflammatory drugs or healthy diets,” he says. Alternatively, Rajagopalan proposes, “A practical solution would be to lower levels of PM2.5.” As Campen wryly points out, “These differing approaches may reflect the backgrounds of an environmental health scientist who understands the challenges entailed in further reductions in air pollution levels, compared with a cardiologist who understands how difficult it is to change human behavior.”