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

Priority sources identification and risks assessment of heavy metal(loid)s in agricultural soils of a typical antimony mining watershed

Heavy metal(loid) (HM) pollution in agricultural soils has become an environmental concern in antimony (Sb) mining areas. However, priority pollution sources identification and deep understanding of environmental risks of HMs face great challenges due to multiple and complex pollution sources coexist. Herein, an integrated approach was conducted to distinguish pollution sources and assess human health risk (HHR) and ecological risk (ER) in a typical Sb mining watershed in Southern China. This approach combines absolute principal component score-multiple linear regression (APCS-MLR) and positive matrix factorization (PMF) models with ER and HHR assessments. Four pollution sources were distinguished for both models, and APCS-MLR model was more accurate and plausible. Predominant HM concentration source was natural source (39.1%), followed by industrial and agricultural activities (23.0%), unknown sources (21.5%) and Sb mining and smelting activities (16.4%). Although natural source contributed the most to HM concentrations, it did not pose a significant ER. Industrial and agricultural activities predominantly contributed to ER, and attention should be paid to Cd and Sb. Sb mining and smelting activities were primary anthropogenic sources of HHR, particularly Sb and As contaminations. Considering ER and HHR assessments, Sb mining and smelting, and industrial and agricultural activities are critical sources, causing serious ecological and health threats. This study showed the advantages of multiple receptor model application in obtaining reliable source identification and providing better source-oriented risk assessments. HM pollution management, such as regulating mining and smelting and implementing soil remediation in polluted agricultural soils, is strongly recommended for protecting ecosystems and humans.

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.

Comparison of trace elements in tissue of beaver (Castor canadensis) and local vegetation from a rural region of southern Ontario, Canada

Beavers have been analyzed in several studies examining trace elements (TEs) in wildlife; however, most of these studies were undertaken in areas with known environmental pollutants. To understand and quantify natural enrichments of TEs in beaver tissue, samples of kidney, liver, muscle from 28 animals were compared with bark from 40 species of trees and shrubs, from the same, uncontaminated watershed. Pearson correlation and factor analysis show that conservative, lithophile elements such as Al, Ga, Th, and Y, all surrogates for mineral dust particles, explain 61% of the variation in the bark data. In contrast, Cd, Co, Cu, Mn, Mo, Ni, Rb, Se, Sr, and Tl in bark are independent of Al, and therefore most likely occur in non-mineral forms. Comparing tissue concentrations of beaver and bark, the organs are enriched in micronutrients such as Cu, Fe, Mo, Se, and Zn, but also non-essential, benign elements such as Cs and Rb, and potentially toxic elements such as Cd and Tl. Thus, the elements most enriched in beaver organs are those that apparently occur in biological form in the plant tissue. The elements enriched in these animals, relative to bark, appear to offer the most promise for monitoring environmental contamination by TEs using beavers. The majority of TEs of environmental relevance are most abundant in beaver kidney. However, monitoring studies must consider the variation in TE concentrations in beaver tissue, including those due to sex and age. Also, due consideration must be given to background concentrations of TEs in the vegetation composing the diet of the animals. The natural enrichment in the case of elements such as Cd, in beaver tissue relative to bark, is profound. These data establish critical baseline values for TEs in beavers in an unpolluted environment, thereby allowing for their use as model organisms in tracking how heavy metal pollutants may affect wildlife.

Sources, spatial-distributions and fluxes of PAH-contaminated dusts in the Athabasca oil sands region

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) has increased in northern Alberta, Canada, due to industrial development in the Athabasca oil sands region (AOSR). However, the sources, summertime deposition fluxes and associated spatial patterns are poorly characterized, and the magnitude of contamination has not been directly contrasted with comparable measurements around large Canadian cities. PAHs were measured in Sphagnum moss collected from 30 bogs in the AOSR and compared with reference moss collected from various remote, rural and near-urban sites in Alberta and Ontario. At all 39 locations, strong correlations between depositional fluxes of PAHs and accumulation rates of ash (n = 117, r = 0.877, p < 0.001) implied that the main source of PAHs to moss was atmospheric deposition of particles. Average PAH concentrations at near-field AOSR sites (mean [SD], 62.4 [24.3] ng/g) were significantly higher than at far-field AOSR sites (44.9 [20.8] ng/g; p = 0.038) or the 7 reference sites in Alberta (20.6 [3.5] ng/g; p < 0.001). In fact, average PAH concentrations across the entire AOSR (7,850 km2) were approximately twice as high as in London, Ontario, or near petroleum upgrading and major traffic corridors in Edmonton, Alberta. A chemical mass balance model estimated that both delayed petcoke (33 % of PAHs) and fine tailings (38 % of PAHs) were the major sources of PAHs in the AOSR. Over the 2015 summer growing season, we estimate that 101-110 kg of PAHs (on 14,300-17,300 tonnes of PAH-containing dusts) were deposited to the AOSR within a 50 km radius of surface mining. Given that the highest PAH deposition was to the northern quadrant of the AOSR, which includes the First Nations community of Fort MacKay, further dust control measures should be considered to protect human and environmental health in the region.

Trace elements in the culturally significant plant Sarracenia purpurea in proximity to dust sources in the oil sands region of Alberta, Canada

Accessible populations of plants are critical to the meaningful exercise of Aboriginal and treaty rights in Canada. In the oil sands region of Alberta, populations of culturally significant plant species overlap with extensive oil and gas development. This has led to a host of questions and concerns related to plant health and integrity from both Indigenous communities and western scientists. Here, we assessed trace element concentrations in the northern pitcher-plant (tsala' t'ile; Sarracenia purpurea L.) with a focus on elements associated with fugitive dust and bitumen. Plant leaves were collected using clean methods and washed prior to analyses in an ultra-clean, metal-free laboratory. Pitcher-plant was an excellent model for assessing the impacts of industrial development on a culturally important, vulnerable species. Although concentrations of trace elements in pitcher-plant were low and not indicative of a toxicological concern, we saw clear dust signatures in plant tissues related to road and surface mine proximity. Elements associated with fugitive dust and bitumen extraction declined exponentially with increasing distance from a surface mine, a well-established regional pattern. However, our analyses also captured localized spikes in trace element concentrations within 300 m of unpaved roads. These local patterns are more poorly quantified at the regional scale but are indicative of the burden to Indigenous harvesters wishing to access plant populations that are not impacted by dust. Further work to directly quantify dust loads on culturally significant plants will help to define the amount of harvesting area lost to Indigenous communities due to dust impacts.

Spatial distribution of selenium and other potentially toxic elements surrounding mountaintop coal mines in the Elk Valley, British Columbia, Canada

Despite the extensive use of mountaintop coal mining in the Elk Valley, British Columbia, Canada's largest metallurgical coal-producing region, little is known about the transport and deposition of fugitive dust emissions within its mountain landscape. This study aimed to assess the extent and spatial distribution of selenium and other potentially toxic elements (PTEs) near the town of Sparwood originating from fugitive dust emitted from two mountaintop coal mines. To achieve these objectives concentrations of 47 elements within moss tissues of Hylocomium splendens, Pleurozium schreberi, and Ptilium crista-castrensis were analyzed from 19 locations between May 29 to June 1, 2022. Contamination factors were then calculated to identify areas of contamination, along with generalized additive models to assess the relationship between selenium and the mines. Finally, Pearson correlation coefficients were calculated between selenium and other PTEs to determine which exhibited similar behaviour. This study found that selenium concentrations are a function of proximity to mountaintop mines, and the region's topographic features and prevailing wind patterns play a role in the transport and deposition of fugitive dust. Contamination is highest immediately surrounding mines and decreases at increasing distances, with the region's steep mountain ridges shielding the deposition of some fugitive dust when acting as a geographic barrier between adjacent valleys. Furthermore, silver, germanium, nickel, uranium, vanadium, and zirconium were identified as other PTEs of concern. The implications of this study are significant as it demonstrated the extent and spatial distribution of contaminants originating from fugitive dust emissions surrounding mountaintop mines and some of the controls to its distribution in mountain regions. As Canada and other mining jurisdictions look to expand critical mineral development, it will be important for proper risk assessment and mitigation in mountain regions to limit community and environmental exposure to contaminants within fugitive dust.

Atmospheric deposition mapping of particulate elements in the Canadian Athabasca oil sands region

This study used a deposition modeling framework to generate gridded dry, wet, and total (dry + wet) deposition fluxes of 27 particulate elements over the Canadian Athabasca oil sands region and its surrounding areas for the years 2016-2017. The framework employed the element concentrations from the CALPUFF dispersion model outputs that were bias-corrected against measured concentrations, modeled dry deposition velocities, precipitation analysis data, and literature values of element-specific fine mode fractions and scavenging ratios by rain and snow. The annual total deposition (mg/m²/year) of all elements (EM) across the domain ranged from 4.49 to 5450 and the mean and median deposition were 60.9 and 31.0, respectively. Total EM deposition decreased rapidly within a short distance from the oil sands mining area. Annual mean total deposition (mg/m²/year) of EM was 717 in Zone 1 (within 30 km from a reference point, representing the center of the oil sands mining area), 115 in Zone 2 (30-100 km from the reference point), and 35.4 in Zone 3 (beyond 100 km from the reference point). The deposition of individual elements was primarily governed by their respective concentrations and among all elements the annual mean total deposition (μg/m²/year) over the domain varied five orders of magnitude ranging from 0.758 (Ag) to 20,000 (Si). Annual mean dry and wet deposition (mg/m²/year) of EM over the domain were 15.7 and 45.2, respectively. Aside from S, which has relatively lower precipitation scavenging efficiencies, wet deposition was the dominant deposition type in the region contributing from 51% (Pb) to 86% (Ca) of the respective total deposition. Total EM deposition over the domain in the warm season (66.2 mg/m²/year) was slightly higher than that in the cold season (55.6 mg/m²/year). Deposition of individual elements in Zone 1 were generally lower than their deposition at other sites across North America.

Emissions database development and dispersion model predictions of airborne particulate elements in the Canadian Athabasca oil sands region

This study developed an emission inventory for 29 elements in PM_2.5 and PM_2.5-10 covering an area of approximately 300 by 420 km² in the Athabasca Oil Sands Region in northern Alberta, Canada. Emission sources were aggregated into nine categories, of which the Oil Sands (OS) Sources emitted the most, followed by the Non-OS Dust sources for both fine and coarse elements over the study area. The top six fine particulate elements include Si, Ca, Al, Fe, S, and K (933, 442, 323, 269, 116, and 103 tonnes/year, respectively), the sum of which accounted for 20.5% of the total PM_2.5 emissions. The top five coarse elements include Si, Ca, Al, Fe, and K (3713, 1815, 1198, 1073, and 404 tonnes/year), and their sum accounted for 29% of the total PM_2.5-10 emissions. Using this emission inventory as input, the CALPUFF dispersion model simulated reasonable element concentrations in both PM_2.5 and PM_2.5-10 when compared to measurements collected at three sites during 2016-2017. Modeled PM₁₀ concentrations of all elements were very close to the measurements at an industrial site with the highest ambient concentration, overestimated by 65% at another industrial site with moderate ambient concentration, and underestimated by 27% at a remote site with very low ambient concentration. Model-measurement differences of annual average concentrations were within 20% for Si, Ca, Al, Fe, Ti, Mn, and Cu in PM_2.5, and were 20-50% for K, S, and Zn in PM_2.5 at two sites located within the OS surface mineable area. Model-measurement differences were larger, but still within a factor of two for elements in PM_2.5-10 at these two sites and for elements in both PM_2.5 and PM_2.5-10 at a background site.

The impact of severe pollution from smelter emissions on carbon and metal accumulation in peatlands in Ontario, Canada

Peatlands are unique habitats that function as a carbon (C) sink and an archive of atmospheric metal deposition. Sphagnum mosses are key components of peatlands but can be adversely impacted by air pollution potentially affecting rates of C and metal accumulation in peat. In this study we evaluate how the loss of Sphagnum in peatlands close to a copper (Cu) and nickel (Ni) smelter in Sudbury, Ontario affected C accumulation and metal profiles. The depth of accumulated peat formed during the 100+ year period of smelter activities also increased with distance from the smelter. Concurrently, peat bulk density decreased with distance from the smelter, which resulted in relatively similar average rates of apparent C accumulation (32-46 g/m²/yr). These rates are within the range of published values despite the historically high pollution loadings. Surface peat close to the smelters was greatly enriched in Cu and Ni, and Cu profiles in dated peat cores generally coincide with known pollution histories much better than Ni that increased well before the beginning of smelter activities likely a result of post-deposition mobility in peat cores.

Are bog plant/lichen tissue concentrations of Ca, Mg, K, and P affected by fugitive dust released from oil sands development in the Fort McMurray region of Alberta?

Bogs are ombrotrophic, relying solely on atmospheric deposition for new inputs of elements. Increased element deposition through anthropogenic activities has the potential to alter nutrient availability, and hence ecosystem function, in bogs. Further, because of efficient element retention, bogs may function as effective monitors of element deposition. To assess the potential effects of particulate fugitive dust from oil sands development in Alberta, Canada, we quantified plant/lichen tissue Ca, Mg, K, and P concentrations in 6 bogs ranging from 12 to 77 km from the oil sands industrial center. Deposition of Ca and Mg, but not K or P, quantified using ion exchange resin collectors, to bogs decreased with distance from the oil sands industrial center. Concentrations of Ca and Mg, but not K or P, in tissues of lichens (Cladonia mitis, Evernia mesomorpha) and Sphagnum (S. capillifolium, S. fuscum) decreased with distance from the oil sands industrial center. Tissue Ca concentrations were positively correlated with growing season Ca and Mg deposition in all species except Vaccinium oxycoccos, Rhododendron groenlandicum, and Picea mariana; leaf Mg concentrations were positively correlated with growing season Mg deposition for all species except P. mariana. Tissue concentrations of K and P were not correlated with growing season K and P deposition. For each species, receptor modeling identified two distinct sources, one dominated by Ca and Mg, presumed to represent particulate fugitive dust from oil sands activities, and a second dominated by K and P, which may reflect tight internal cycling and upward translocation of K and P in peat and/or K and P deposition as particulates generated in wildfires. Increasing Ca²⁺ and Mg²⁺ deposition may acidify bog porewaters through cation exchange in peat.

Environmental significance of trace elements in the Athabasca Bituminous Sands: facts and misconceptions

The bituminous sands of Alberta, Canada, represent the second largest reserves of hydrocarbons on earth. Open pit bitumen mining and upgrading of the Athabasca Bituminous Sands (ABS), the largest of the deposits, began in 1967. Concerns about fugitive release of trace elements (TEs) to the environment began with studies of V, as this is the most abundant trace metal in bitumen. Recent studies, however, have extended to Ag, As, Be, Cd, Cr, Cu, Pb, Sb, and Tl, and this has led to considerable confusion about which TEs are relevant to ecosystem health. While V along with Ni, Mo, Se and Re are enriched in bitumen, Ag, As, Be, Cd, Cr, Cu, Pb, Sb and Tl are found almost exclusively in the mineral (i.e. sand) fraction of the ABS, with limited opportunity to become bioaccessible, much less bioavailable. Here, a summary is given of ten misunderstandings that have arisen regarding TEs in the environment of the ABS region. To help illustrate the significance of the misconceptions that have arisen regarding (a) air and (b) water resources, published and unpublished TE data obtained from the metal-free, ultraclean SWAMP lab is presented for: (a) snow, moss, and peat cores from bogs, and (b) the dissolved, particulate, and colloidal fractions of water from the Athabasca River (AR), as well as pristine groundwater. Natural enrichments of Ni in plants such as Rat Root (Acorus calamus) and pine (Pinus banksiana), Tl in fish (Percopsis omiscomaycus) and Cd in cranberries (Vaccinium oxycoccus), Labrador Tea (Rhododendron groenlandicum) and beaver (Castor canadensis), are also presented.

Real-time measurements of mineral dust concentration in coarse particulate matter (PM10-2.5) by employing a novel optical-based technique in Los Angeles

As a primary component of coarse particulate matter (PM), ambient mineral dust has been linked to adverse health effects. Los Angeles, the largest metropolitan urban area of the United States, is impacted by both windblown and localized sources of mineral dust, often internally mixed with black carbon. The estimation of mineral dust concentrations with a high time resolution becomes critical in improving our understanding of its sources and temporal trends. Using Aethalometers combined with a high-volume virtual impactor (VI) to enrich coarse (2.5 <dp < 10 μm) particles, the light absorption and mass concentration of mineral dust were estimated in real-time during summer, fall, and winter over 2020-2021. The concentration-enriched coarse PM was collected on Teflon filters, and its chemical composition in terms of trace elements and metals was chemically quantified. The high time-resolution measurements enabled us to calculate the absorption coefficient of enriched dust particles by subtracting the light absorption of the post-VI coarse PM from that of the PM_2.5 aerosol fraction to reduce the impact of stronger light absorbers in ambient PM. Mineral dust was more prevalent during the fall and winter campaigns (i.e., 19.3 and 11.4 μg/m³, respectively), lower concentrations were observed during the summer campaign (i.e., 8.50 μg/m³). The calculated absorption Ångström exponent (AAE) was 2.18, highlighting the presence of dust particles during the sampling period. The dust mass absorption coefficient was estimated to be 2.7 ± 1.6 Mm^-1 at 370 nm and 0.41 ± 0.16 Mm^-1 at 880 nm wavelengths, respectively. The validation of the proposed approach was investigated by comparing the evaluated mineral dust mass concentrations in this study with the reported coarse PM concentrations by the California Air Resources Board (CARB). The results reported by the optical-based approach with high temporal resolution can provide crucial information on identifying sources of mineral dust in urban areas.

A re-analysis and review of elemental and polycyclic aromatic compound deposition in snow and lake sediments from Canada's Oil Sands Region integrating industrial performance and climatic variables

Much of the research from Canada's oil sands region (OSR) shows contaminants of concern (CoCs) throughout the ambient environment surrounding the industrial facilities. While there are some well-established sources of the CoCs, there is also spatial and temporal variability suggesting activity intensity, changes in technology, types and amounts of fuels combusted at the facilities, and climate may affect the results of deposition studies. This study re-analysed published data on the deposition of elements and polycyclic aromatic compounds (PACs) in snow and the sediments of some lakes by incorporating production data from facilities and climate. Using the Elastic Net (EN) regularized regression, variables describing potential associations between facility-specific activity and climate on the deposition of CoCs were identified. Among the selected variables, the combustion of delayed petroleum coke at the Suncor Basemine was associated with the deposition of CoCs, including elements in snow and in some lakes. Similarly, combustion of petroleum coke at Syncrude Mildred Lake was also identified in some models. In both cases, the effects of petroluem coke combustion are likely associated with the emission and deposition of fly ash. The mass of stored petroleum coke was not selected in snow CoC models, but the speed of the wind was a common driver for PACs. However, the mass of stockpiled petcoke was more closely associated with both elements and PACs in lake sediments. While the potential influence of other variables on the occurrence of CoCs in the OSR was also identified, including the production of crude bitumen and synthetic crude, the use of process and natural gases, temperature, and precipitation, these analyses support much of the earlier work and provides additional nuance. While more work is required, these results suggest facility-specific production and climatic data can be coupled with existing approaches to improve the identification of sources of CoCs in Canada's OSR and practices associated with their release.

A critical review of the ecological status of lakes and rivers from Canada's oil sands region

We synthesize the information available from the peer-reviewed literature on the ecological status of lakes and rivers in the oil sands region (OSR) of Canada. The majority of the research from the OSR has been performed in or near the minable region and examines the concentrations, flux, or enrichment of contaminants of concern (CoCs). Proximity to oil sands facilities and the beginning of commercial activities tend to be associated with greater estimates of CoCs across studies. Research suggests the higher measurements of CoCs are typically associated with wind-blown dust, but other sources also contribute. Exploratory analyses further suggest relationships with facility production and fuel use data. Exceedances of environmental quality guidelines for CoCs are also reported in lake sediments, but there are no indications of toxicity including those within the areas of the greatest atmospheric deposition. Instead, primary production has increased in most lakes over time. Spatial differences are observed in streams, but causal relationships with industrial activity are often confounded by substantial natural influences. Despite this, there may be signals associated with site preparation for new mines, potential persistent differences, and a potential effect of petroleum coke used as fuel on some indices of health in fish captured in the Steepbank River. There is also evidence of improvements in the ecological condition of some rivers. Despite the volume of material available, much of the work remains temporally, spatially, or technically isolated. Overcoming the isolation of studies would enhance the utility of information available for the region, but additional recommendations for improving monitoring can be made, such as a shift to site-specific analyses in streams and further use of industry-reported data. Integr Environ Assess Manag 2022;18:361-387. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Quantitative source identification and environmental assessment of trace elements in the water and sediment of rivers flowing into Laizhou Bay, Bohai Sea

The concentrations, sources, and ecological risks of nine trace elements in nine rivers flowing into Laizhou Bay were investigated. The dissolved element concentrations were 1.85-74.4, 0.01-0.47, 0.15-3.46, 1.54-19.7, 2.92-45.1, 1.72-11.5, 1.02-8.35, 0.10-1.02, and 21.4-185 μg/L for As, Cd, Co, Cr, Cu, Ni, Sc, Pb, and Zn, respectively. Zinc was the most abundant element in the sediments, with an average concentration of 106 mg/kg, followed by Cr (64.5 mg/kg), Cu (25.5 mg/kg), Pb (24.3 mg/kg), Ni (23.4 mg/kg), Co (10.9 mg/kg), Sc (8.14 mg/kg), As (6.75 mg/kg), and Cd (0.16 mg/kg). Elements including Co, Cr, Ni, and Sc were mainly from natural sources and As, Cd, Cu, Pb, and Zn were largely influenced by anthropogenic activities such as agricultural practice, industrial production, river transportation, and urbanization. Overall, the rivers flowing into Laizhou Bay experienced slight pollution and ecological risk. However, the severe element contamination in Jie River deserves continuous attention.

Impact of the 2016 Fort McMurray wildfires on atmospheric deposition of polycyclic aromatic hydrocarbons and trace elements to surrounding ombrotrophic bogs

Fort McMurray and the Athabasca oil sands region (AOSR) experienced major wildfires in 2016, but the impact of these on regional deposition of polycyclic aromatic hydrocarbons (PAHs) and trace elements has not been reported nor compared to industrial sources of these pollutants in the region. Living moss (Sphagnum fuscum) was collected in triplicate from five ombrotrophic bogs in the AOSR after the wildfires, and analyzed for PAHs and trace elements. These post-wildfire data were compared to data from previous years at the same sites, and also to remote reference bogs in Alberta and Ontario. Elevated post-wildfire concentrations and flux of naphthalene and fluorene were observed at all five bogs in the AOSR, but no consistent trend was evident for higher molecular weight PAHs or the sum of priority PAHs (∑₁₃PAH). Trace elements at most AOSR bogs were not elevated post-wildfire, except at one bog in the burned area (MIL), but even here the elements that were increased (1.7-5.6 × ) were likely of bitumen-origin (i.e., V, Ni, Se, Mo and Re). Significant post-wildfire correlations between PAHs and most trace elements suggested a common source, and few significant correlations were observed with retene, suggesting that wildfires were not the dominant source of most contaminants detected. Mass balance receptor models were used to apportion sources, indicating that the major sources of trace elements among five AOSR bogs post-wildfire were oil sands ore (mean 42%), haul road dust (17%), and petcoke (11%), whereas wildfire was always a minor source (3-4%). For PAHs at the most contaminated site (MIL), delayed petcoke (27%) and wildfire (25%) were the major sources, but the contribution of wildfire to PAHs at other sites was less or not discernable. Impacts of the 2016 wildfires on regional atmospheric deposition of major pollutants was less than from ongoing deposition of anthropogenic dust from oil sands activities.

Exploring the Influence of Industrial and Climatic Variables on Communities of Benthic Macroinvertebrates Collected in Streams and Lakes in Canada’s Oil Sands Region

Identifying and tracking the influence of industrial activities on streams and lakes is a priority for monitoring in Canada’s oil sands region (OSR). While differences in indicators are often found in waterbodies adjacent to mining facilities, the confounding influence of natural exposures to bitumen and other stressors can affect the identification of industrial effects. However, recent work suggests metrics of industrial activity at individual facilities, including production and fuel consumption, may be used in site-specific analyses to identify influence of the industry as a whole as well as individual operations. This study further examined the potential relationships between industrial and climatic variables on benthic communities from 13 streams and 4 lakes using publicly available data from the minable region and the Elastic Net (EN) variable selection technique. From the full set of possible industrial and climate variables, the EN commonly identified the negative influence of plant and fuel use of petroleum coke at the Suncor Basemine on benthic communities in streams and lakes. The fuel/plant use of petroleum coke at Suncor likely reflects the emission and regional deposition of delayed coke fly ash. Among the other industrial variables, crude bitumen production at Syncrude Mildred Lake and other facilities, steam injection rates, and petroleum coke stockpiling were also selected for some benthic invertebrate indices at some sites. Land disturbance metrics were also occasionally selected, but the analyses largely support the predominant influence of industrial facilities via (inferred) atmospheric pathways. While climate variables were also commonly selected by EN and follow-up work is needed, this study suggests that integrating industrial performance data into analyses of biota using a site-specific approach may have broad applicability in environmental monitoring in the OSR. More specifically, the approach used here may both resolve the long-standing challenge of natural confounding influences on monitoring the status of streams in the OSR and track the influence of industrial activities in biota below critical effect sizes.

Deposition records of polycyclic aromatic hydrocarbons and black carbon in peat core from Dajiuhu, Shennongjia, Central China: human activity imprint since the industrial revolution

Polycyclic aromatic hydrocarbons (PAHs) are a kind of organic pollutants with carcinogenic, teratogenic, and mutagenic effects. This study aims to assess the effects of changes in China's socio-economic indicators represented by energy consumption and number of motor vehicles, on PAHs and black carbon (BC) deposition. For this, a 50-cm peat core from Dajiuhu peatland, Central China, was collected and divided into 50 subsamples to establish a sedimentary record of about 200 years with radioactive ²¹⁰Pb. The Σ₁₆PAH concentration ranged from 212.67 to 830.10 ng·g^-1, mainly composed of 2- and 3-ring PAHs, and BC ranged from 7.89 to 36.48%. The deposition characteristics of BC first increased and then decreased from the core bottom to the top. The predominant of the carcinogenic PAHs (C-PAHs) was Dibenzo[a,h]anthracene (DBA) before 1949, and then changed to Benzo[b]fluoranthene (BbF). Ratio of Fla/Pyr, (3+4)-ring/(5+6)-ring PAHs, and BaA/(BaA+Chr), IcdP/(IcdP+BghiP) suggested that long-range atmospheric transmission (LRAT) and pyrogenic were the main PAHs sources, but that local PAH emission contribution gradually increased since 1990, and mixed (petroleum and combustion) sources were the dominant since 2000. The high concentration of Phenanthrene (Phe) and Naphthalene (Nap) were likely from plant product. Furthermore, increased concentrations of 4-, 5-, and 6-ring PAHs showed significant correlations with increased coal and petroleum consumption and the number of motor vehicles, respectively, and this influence has strengthened after 2000. These were caused by rapid urbanization and industrialization following the implementation of the reform and opening up policy in 1978, and a new round of urbanization after 2000.

Characterization and source apportionment of airborne particulate elements in the Athabasca oil sands region

The oil sands industries in Alberta, Canada are potential sources of particulate-bound elements in the region. This study explored the ambient concentrations and size distributions, and conducted source apportionment of 48 particulate elements, based on samples collected in 2016-2017 at four air monitoring sites in the Athabasca oil sands region: Fort McKay (AMS1), Buffalo Viewpoint (AMS4), Wapasu Creek (AMS17), and Stoney Mountain (AMS18). Element concentrations in fine and coarse particulate matter (PM_2.5 and PM_2.5-10 respectively) at the four sites were generally lower than their typical concentrations at other urban and industrial sites in North America. Among all elements, S was the most abundant in PM_2.5 with mean concentrations ranging from 189 ng/m³ (AMS18) to 284 ng/m³ (AMS1). Of the trace, toxic elements in PM_2.5, Zn was the most abundant with mean concentrations ranging from 3.43 ng/m³ (AMS18) to 5.37 ng/m³ (AMS4). Positive Matrix Factorization (PMF) modeling of the element concentrations in PM_2.5 was used for source apportionment for Zone1 (including AMS 1, 4, and 17, situated closer to industrial activities) and for Zone2 (including AMS18, a background site). The sources of elements for Zone1, included crustal dust, bitumen processing, haul road dust, and biomass burning that explained ~33%, ~43%, ~15%, and ~9% of the total resolved elemental mass, respectively. The sources of elements for Zone2, included Pb-rich source, biomass burning, fugitive oil sands, crustal dust, and bitumen processing explaining ~8%, ~7%, ~3%, ~22%, and ~60% of the total resolved elemental mass, respectively. Elemental mass concentrations of the bitumen processing source factor at Zone2 was two-thirds of that in Zone1. Overall, mass proportions of the bitumen processing source factor at all four sites were significant, suggesting that the oil sands industries played a key role in ambient element concentration levels in the region.

Testing different methods of estimating edaphic inputs in moss biomonitoring

Although soil is known to contribute to the concentrations of elements in moss, protocols for atmospheric biomonitoring with terrestrial moss do not include recommendations on how to address this factor. As a result, researchers indiscriminately use a wide range of detection/correction methods without considering whether the results are equivalent. In this study, three of these methods were compared: i) use of the enrichment factor (EF) index; ii) calculation of the ratios of different elements in soil and moss, and subtraction of the contribution of soil concentrations from the raw concentrations of elements in mosses (SCS); and iii) positive matrix factorization (PMF), a receptor modelling method for source apportioning based on multivariate analysis techniques. The aim of the comparison was to determine whether the methods produce equivalent results and, if not, which method is the most appropriate for use in moss biomonitoring surveys. The data used corresponded to 146 samples of Pseudoscleropodium purum collected from a regular sampling grid of 15 × 15 km in Galicia (NW Spain). Comparison of the methods revealed that, although they yield relatively similar results, the corresponding interpretations are not equivalent and none of the methods provides a reliable estimate of the soil contribution to the concentrations of elements in moss samples. Independently of the technique applied, use of Ti as a reference element is not recommended, because, at least in this study, it was present at unusually high levels in moss. Given the absence of a reliable correction method and the fact that most elements are present in fairly high amounts in the soil, we recommend using atmospheric biomonitoring with moss only for Cu, Zn and Cd, i.e. for those elements in moss for which the soil contributes very low amounts and corrections are not therefore necessary.

Arsenic release to the environment from hydrocarbon production, storage, transportation, use and waste management

Arsenic (As) is a toxic trace element with many sources, including hydrocarbons such as oil, natural gas, oil sands, and oil- and gas-bearing shales. Arsenic from these hydrocarbon sources can be released to the environment through human activities of hydrocarbon production, storage, transportation and use. In addition, accidental release of hydrocarbons to aquifers with naturally occurring (geogenic) As can induce mobilization of As to groundwater through biogeochemical reactions triggered by hydrocarbon biodegradation. In this paper, we review the occurrence of As in different hydrocarbons and the release of As from these sources into the environment. We also examine the occurrence of As in wastes from hydrocarbon production, including produced water and sludge. Last, we discuss the potential for As release related to waste management, including accidental or intentional releases, and recycling and reuse of these wastes.

Potential Influence of Sewage Phosphorus and Wet and Dry Deposition Detected in Fish Collected in the Athabasca River North of Fort McMurray

The health of fish is a primary indicator of ecosystem response in the Oil Sands Region of northeastern Alberta. However, industrial activity is accompanied by other stressors, such as the discharge of sewage, municipal activity, forest fires, and natural weathering and erosion of bitumen. To combat the spatial confounding influences, we examined white sucker (Catostomus commersonii) captured in the Athabasca River at sites over time (2011–2019) and included covariates to account for the possible sources of influence. The analyses suggest spatially heterogeneous influences of natural factors on fish, such as discharge and air temperature, but also the influence of sewage phosphorus and precipitation. Among the stressors examined here, precipitation may be the most complex and may include a mixture of sources including inputs from tributaries, urban activity, industrial development, and forest fires. Although suggestive, the attribution of variance and detection of changes are affected by sample sizes in some years; these analyses may have missed effects or misspecified important relationships, especially in males. Despite these limitations, the analyses suggest potential differences may be associated with precipitation and highlight the need to integrate robust information on known and suspected stressors in future monitoring of aquatic ecosystems in the oil sands region and beyond.

Identifying sources of dust aerosol using a new framework based on remote sensing and modelling

Dust particles are transported globally. Dust storms can adversely impact both human health and the environment, but they also impact transportation infrastructure, agriculture, and industry, occasionally severely. The identification of the locations that are the primary sources of dust, especially in arid and semi-arid environments, remains a challenge as these sites are often in remote or data-scarce regions. In this study, a new method using state-of-the-art machine-learning algorithms - random forest (RF), support vector machines (SVM), and multivariate adaptive regression splines (MARS) - was evaluated for its ability to spatially model the distribution of dust-source potential in eastern Iran. To accomplish this, empirically identified dust-source locations were determined with the ozone monitoring instrument aerosol index and the Moderate-Resolution Imaging Spectroradiometer (MODIS) Deep Blue aerosol optical thickness methods. The identified areas were divided into training (70%) and validation (30%) sets. Measurements of the conditioning factors (lithology, wind speed, maximum air temperature, land use, slope angle, soil, rainfall, and land cover) were compiled for the study area and predictive models were developed. The area-under-the-receiver operating characteristics curve (AUC) and true-skill statistics (TSS) were used to validate the maps of the models' predictions. The results show that the RF algorithm performed best (AUC = 89.4% and TSS = 0.751), followed by the SVM (AUC = 87.5%, TSS = 0.73) and the MARS algorithm (AUC = 81%, TSS = 0.69). The results of the RF indicated that wind speed and land cover are the most important factors affecting dust generation. The region of highest dust-source potential that was identified by the RF is in the eastern parts of the study region. This model can be applied to other arid and semi-arid environments that experience dust storms to promote management that prevents desertification and reduces dust production.

Trace elements in Labrador Tea (Rhododendron groenlandicum): How predominant sources to the plants impact the chemical composition of hot water extracts

Labrador Tea (Rhododendron groenlandicum) has been an important food and medicinal plant to First Nations communities in North America for millenia, but little is known of its geochemical properties. Using plants from 10 sites in 4 provinces, including pristine and industrial regions, and employing the metal-free, ultraclean SWAMP laboratory facilities and procedures, we provide an estimate of the natural abundance of trace elements in the leaves, and the extent of their release during hot water extraction. Elements decrease in abundance in the order Mn > Al > Fe > Zn > Cu > Ni > V > Pb > La > Mo > Y > La > Tl > Cd > Th > Ag. The greatest concentrations of conservative, lithophile elements such as Al, La, Th and Y, are found in samples collected on lands reclaimed from open pit bitumen mines in northern Alberta, reflecting elevated inputs of atmospheric dusts. In contrast, micronutrients such as Cu and Zn are remarkably uniform which suggests that these are supplied almost exclusively by plant uptake via roots. Deionized, reverse osmosis water is more effective in removing some elements (e.g. Al, La, Y, Fe, Zn, Cd) whereas others are more readily extracted using groundwater (e.g. Cu, Ni, Pb); V behaves independently of water composition. In both types of water, the elements most readily extracted are plant micronutrients (Mn, Ni, Cu, and Zn) whereas those supplied primarily by dust exhibit much lower yields; Al shows behaviour intermediate between these two extremes. While element concentrations in the infusions increase with increasing concentrations in the leaves, the abundance of potentially toxic chalcophile elements such as Cd, Pb, Sb and Tl in the infusions are extremely low (ng/l). Plants from British Columbia, Ontario and Quebec provide evidence of atmospheric Pb contamination, yielding greater ratios of Pb/La compared to the samples from Alberta where crustal values are found. Given that this plant is common and found across the northern half of the continent, it shows great promise as a tool for biomonitoring of air quality. For consumers, Labrador Tea may represent an important dietary source of Mn.

Ambient concentrations and total deposition of inorganic sulfur, inorganic nitrogen and base cations in the Athabasca Oil Sands Region

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 SO₄^2- 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 SO₄^2-, 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.

A novel approach to peatlands as archives of total cumulative spatial pollution loads from atmospheric deposition of airborne elements complementary to EMEP data: priority pollutants (Pb, Cd, Hg)

A novel approach to using peatlands for assessment of cumulative contributions from long-range transport of pollutants (LRTP) - airborne trace elements - to spatial pollution was exemplified in evaluating retrospective atmospheric deposition of priority pollutants (Pb, Cd, Hg) in peat bogs in Norway in areas minor affected by local sources of pollution and in NW Poland located on the way of possible LRTP from Poland to Norway. Peat from the corresponding ¹⁴C-dated layers of five ombrotrophic bogs in each country, was analysed for trace element contents. Pollutant concentrations/load distribution along the peat profiles related to bulk density has given a clear evidence of uneven density-dependent temporal vertical migration of all studied elements that distorts the chronology of their deposition. Much higher loads of Pb, Cd and Hg in southern Norwegian bogs than in bogs located in NW Poland proved transboundary transport from neighbouring highly industrialized European countries to be much more significant contributor to high deposition of the priority pollutants in this area and rather excludes LRTP from Poland as a major source of total land pollution in southernmost Norway. The study showed excellent applicability of peat bogs for the exact assessment of retrospective cumulative pollutant loads from LRTP, but not for the identification of deposition chronology. Combining the use of ombrotrophic peat bogs as tools for retrospective monitoring of cumulative land pollution with airborne elements with current LRTP data within the Cooperative Programme for Monitoring and Evaluation of the Long-Range Transmission of Air Pollutants in Europe (EMEP) may provide a complete reliable picture of the effect of anthropogenic emissions on soil quality and create a foundation of optimum environmental policy and activities in this field.

Forest health effects due to atmospheric deposition: Findings from long-term forest health monitoring in the Athabasca Oil Sands Region

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.

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.

Introduction to the virtual special issue monitoring ecological responses to air quality and atmospheric deposition in the Athabasca Oil Sands region the wood Buffalo environmental Association's Forest health monitoring program

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. Monitoring of a targeted suite of indicators began in 2012 at 25 jack pine stand edge monitoring sites. This special issue presents the results derived from biophysical sampling campaigns (1998 to 2013), coupled with ongoing ambient atmospheric, deposition and epiphytic lichen monitoring (data through 2017) and source apportionment studies, as well as papers contributed by others engaged in regional research and monitoring programs. The Forest Health Monitoring Program provides data supportive of regulatory and stakeholder evaluations of environmental quality, and is adaptive to new needs, extreme environmental events and technological development while providing continuity of monitoring.

Reanalysis of aerial deposition of metals and polycyclic aromatic compounds to snow in the Athabasca Oil Sands Region of Alberta Canada

Oil sands mining and bitumen upgrading activities in the Athabasca Oil Sands Region (AOSR) have been identified as sources of metals and polycyclic aromatic compounds (PAC) being deposited to the regional snowpack. We performed an independent reanalysis of publicly available AOSR snow pack data to: replicate previous results; to provide new insights into the spatial and temporal patterns of metal and PAC deposition; and, to determine whether certain metals or PACs were associated with specific oil sands mining or upgrading activities. Using PAC ratios, we use a K-means clustering approach to classify snowpack data into two combustion-dominated classes, and three classes associated with oil sands mining and bitumen upgrading. Snow samples dominated by "oil sands mine" emissions are consistent with a petrogenic source and exhibited low UNS ratios and high DBT ratios. Snow samples dominated by "petroleum coke" emissions had the highest BaP ratios, high DBT ratios, and were collected nearest the upgrader complexes. Metals data indicate snow samples dominated by oil sands mine emissions are consistent with an Athabasca Sands type composition. Those dominated by emissions from petroleum coke show enrichment of biophile metals V, Ni, and M. We conclude that previous studies have over-estimated environmental loadings of PACs, their spatial extent, and direction of their trend over time. These differences are attributed to the use of arithmetic rather than geometric spatial averaging, use of an arbitrary location (AR6) to determine the extent of metals and PAC deposition, and because previous studies neglected to account for metals and PACs being deposited from non-oil sands sources. Oil sands operators continue to reduce their emissions intensity, however there is an emerging consensus that mitigating fugitive emissions from petroleum coke stockpiles may represent the greatest opportunity to reduce environmental loadings of PACs in the AOSR.

Elemental characterization of general aviation aircraft emissions using moss bags

In light of growing concern and insufficient knowledge on the negative impact of aircraft emissions on environmental health, this study strives to investigate the air burden of major and trace elements caused by general aviation, piston-engine, and turboprop aircraft, within the vicinity of Eskisehir Hasan Polatkan Airport (Eskisehir, Turkey). The levels of 57 elements were investigated, based on moss bag biomonitoring using Sphagnum sp., along with chemical analyses of lubrication oil and aviation gasoline fuel used in the aircraft's operations. Five sampling sites were selected within the vicinity of the airport area to capture spatial changes in the concentration of airborne elements. The study demonstrates that moss bag biomonitoring is a useful tool in the identification of differences in the air burden by major and trace elements that have concentrated downwind of the aircraft emission sources. Moreover, pollutant enrichment in the Sphagnum moss bags and elemental characterization of oil/fuel are in agreement suggesting that Pb, followed by Cd, Cu, Mo, Cr, Ni, Fe, Si, Zn, Na, P, Ca, Mg, and Al are dominant elements that shaped the general aviation aircraft emissions.

Terrestrial Ecosystem Impacts of Sulfide Mining: Scope of Issues for the Boundary Waters Canoe Area Wilderness, Minnesota, USA

Large-scale metal mining operations are planned or underway in many locations across the boreal forest biome in North America, Europe, and Asia. Although many published analyses of mining impacts on water quality in boreal landscapes are available, there is little guidance regarding terrestrial impacts. Scoping of potential impacts of Cu-Ni exploration and mining in sulfide ores are presented for the Boundary Waters Canoe Area Wilderness (BWCAW), Minnesota USA, an area of mostly boreal forest on thin soils and granitic bedrock. Although the primary footprint of the proposed mines would be outside the BWCAW, displacement and fragmentation of forest ecosystems would cause spatial propagation of effects into a secondary footprint within the wilderness. Potential negative impacts include disruption of population dynamics for wildlife species with migration routes, or metapopulations of plant species that span the wilderness boundary, and establishment of invasive species outside the wilderness that could invade the wilderness. Due to linkages between aquatic and terrestrial ecosystems, acid mine drainage can impact lowland forests, which are highly dependent on chemistry of water flowing through them. The expected extremes in precipitation and temperature due to warming climate can also interact with mining impacts to reduce the resilience of forests to disturbance caused by mining.

Anthropogenic and lithogenic fluxes of atmospheric lead deposition over the past 3600 years from a peat bog, Changbai Mountains, China

Ombrotrophic peatlands are widely used to reconstruct atmospheric metal deposition histories. Here, we estimated the long-term atmospheric Pb deposition flux using ombrotrophic peatland data from the Changbai Mountains, northeast China. A peat profile of 320-cm depth was sampled and cut into 164 slices for measurement of Pb and other elements by ICP-MS and ICP-AES and radiometric dating by ²¹⁰Pb, ¹³⁷Cs and ¹⁴C. Pb concentration in the peat ranged from 2.18 to 68.33 mg kg^-1, while the atmospheric Pb deposition flux ranged from 0.12 to 12.49 mg m^-2 a^-1. The Little Ice Age (cold and wet climate) led to low Pb concentration, Pb/Sc ratio, and Pb deposition flux (4.40 ± 0.70 mg kg^-1, 2.04 ± 0.38, and 0.28 ± 0.09 mg m^-2 a^-1, respectively). On the other hand, intense volcanic eruptions resulted in high Pb concentration, Pb/Sc ratio, and P flux (54.48 ± 13.08 mg kg^-1, 7.85 ± 2.09, and 8.15 ± 2.85 mg m^-2 a^-1, respectively). In addition, rapid economic development since the 1980s resulted in a gradual increase of anthropogenic Pb concentration from 1.54 mg kg^-1 to 5.85 mg kg^-1; thus, the anthropogenic Pb deposition flux (0.43 ± 0.21 mg m^-2 a^-1) was high during this period. In general, peat Pb concentration and atmospheric Pb deposition fluxes in this region have been affected by climate change, volcanic eruptions, and human activities. It was further demonstrated that atmospheric Pb emissions and deposition in China decreased since leaded gasoline was phased out in 2001. The results are critical to understand the geochemistry of Pb and to assess the effects of human activities on atmospheric Pb emissions and deposition in China.

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.

Mercury in tundra vegetation of Alaska: Spatial and temporal dynamics and stable isotope patterns

Vegetation uptake of atmospheric mercury (Hg) is an important mechanism enhancing atmospheric Hg deposition via litterfall and senescence. We here report Hg concentrations and pool sizes of different plant functional groups and plant species across nine tundra sites in northern Alaska. Significant spatial differences were observed in bulk vegetation Hg concentrations at Toolik Field station (52 ± 9 μg kg^-1), Eight Mile Lake Observatory (40 ± 0.2 μg kg^-1), and seven sites along a transect from Toolik Field station to the Arctic coast (36 ± 9 μg kg^-1). Hg concentrations in non-vascular vegetation including feather and peat moss (58 ± 6 μg kg^-1 and 34 ± 2 μg kg^-1, respectively) and brown and white lichen (41 ± 2 μg kg^-1 and 34 ± 2 μg kg^-1, respectively), were three to six times those of vascular plant tissues (8 ± 1 μg kg^-1 in dwarf birch leaves and 9 ± 1 μg kg^-1 in tussock grass). A high representation of nonvascular vegetation in aboveground biomass resulted in substantial Hg mass contained in tundra aboveground vegetation (29 μg m^-2), which fell within the range of foliar Hg mass estimated for forests in the United States (15 to 45 μg m^-2) in spite of much shorter growing seasons. Hg stable isotope signatures of different plant species showed that atmospheric Hg(0) was the dominant source of Hg to tundra vegetation. Mass-dependent isotope signatures (δ²⁰²Hg) in vegetation relative to atmospheric Hg(0) showed pronounced shifts towards lower values, consistent with previously reported isotopic fractionation during foliar uptake of Hg(0). Mass-independent isotope signatures (Δ¹⁹⁹Hg) of lichen were more positive relative to atmospheric Hg(0), indicating either photochemical reduction of Hg(II) or contributions of inorganic Hg(II) from atmospheric deposition and/or dust. Δ¹⁹⁹Hg and Δ²⁰⁰Hg values in vascular plant species were similar to atmospheric Hg(0) suggesting that overall photochemical reduction and subsequent re-emission was relatively insignificant in these tundra ecosystems, in agreement with previous Hg(0) ecosystem flux measurements.

Interspecies comparison of three moss species (Hylocomium splendens, Pleurozium schreberi, and Isothecium stoloniferum) as biomonitors of trace element deposition

Biomonitoring with mosses is a common method widely used to assess the spatial and temporal trends of atmospheric deposition in Europe since its introduction in the 1970s. Based on previous investigations, certain moss species provide the most accurate reflection of atmospheric deposition. However, sampling of just one species across large areas can pose a challenge, therefore the ability to use multiple moss species interchangeably is integral to an effective moss biomonitoring survey. In this study, biomonitoring abilities of two common species (Hylocomium splendens [Hs] and Pleurozium schreberi [Ps]) were compared to a potential new biomonitoring species endemic to North America (Isothecium stoloniferum [Is]). Thirteen metal concentrations were analyzed (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, and Pb) in moss tissue from 20 sites with co-located species (Ps/Hs, Is/Hs) Five metals (Al, V, Fe, Ni, and Pb) showed significant and strong correlations (Spearman correlation, r ≥ 0.7 α = 0.05) for all three species, reflecting the established deposition gradient in the region. Furthermore, there was no significant difference in observations (and moderate correlation) for Cr, which suggests that all species exhibited similar uptake abilities for these six metals (Al, V, Cr, Fe, Ni, and Pb). Four metals (Co, As, Se, and Cd) exhibited concentrations below detection at a number of sites, which may have influenced the assessment of interspecies relationships. It is recommended that interspecies calibration be carried out under all surveys that employ multiple moss species.

Bioaccumulation of Tl in otoliths of Trout-perch (Percopsis omiscomaycus) from the Athabasca River, upstream and downstream of bitumen mining and upgrading

It has been suggested that open pit mining and upgrading of bitumen in northern Alberta releases Tl and other potentially toxic elements to the Athabasca River and its watershed. We examined Tl and other trace elements in otoliths of Trout-perch (Percopsis omiscomaycus), a non-migratory fish species, collected along the Athabasca River. Otoliths were analyzed using ICP-QMS, following acid digestion, in the metal-free, ultraclean SWAMP laboratory. Compared to their average abundance in the dissolved (<0.45 μm) fraction of Athabasca River, Tl showed the greatest enrichment in otoliths of any of the trace elements, with enrichments decreasing in the order Tl, Sr, Mn, Zn, Ba, Th, Ni, Rb, Fe, Al, Cr, Ni, Cu, Pb, Co, Li, Y, V, and Mo. Normalizing Tl in the otoliths to the concentrations of lithophile elements such as Li, Rb, Al or Y in the same tissue reveals average enrichments of 177, 22, 19 and 190 times, respectively, relative to the corresponding ratios in the water. None of the element concentrations (Tl, Li, Rb, Al, Y) or ratios were significantly greater downstream of industry compared to upstream. This natural bioaccumulation of Tl most likely reflects the similarity in geochemical and biological properties of Tl⁺ and K⁺. SUMMARY OF MAIN FINDINGS: Thallium is enriched in fish otoliths, relative to the chemical composition of the river, to the same degree both upstream and downstream of industry.

Multi-element composition of soil, mosses and mushrooms and assessment of natural and artificial radioactivity of a pristine temperate rainforest system (Slavonia, Croatia)

This study investigates multi-element composition of soil, mosses and mushrooms from a pristine temperate rainforest (Prašnik, Croatia). Additionally, the activity levels of natural (²³⁸U, ²³⁵U and ²³²Th decay chains, ⁴⁰K and ⁷Be) and anthropogenic (¹³⁷Cs and ¹³⁴Cs) radionuclides in the investigated soil samples, obtained by gamma spectrometry, provide baseline of environmental radioactivity levels in this area. The aim of investigation was to explore the uptake of metal(loid)s by bioindicator species (mosses, mushrooms) growing in a pristine environment characterized by naturally elevated concentration of metals. The calculated enrichment and bioaccumulation factors, correlations between different groups of elements and similar multi-element patterns in mosses, mushrooms and soil samples revealed the prevailing influence of the local substrate geochemistry on element concentrations in mosses and mushrooms. The results suggest atmospheric deposition of Bi, Cd and Pb, while radionuclide activities point to atmospheric fall-out (including global contamination by radiocaesium) and influence of the pedological substrate. The confined area of investigation, with limited variations in soil characteristics and geological composition, allowed clearer insight into the origin of metal(loid)s in mosses and mushrooms. On the other hand, using bioindicator species with different element uptake mechanisms enabled distinction between different sources of elements.

Measuring the distribution of trace elements amongst dissolved colloidal species as a fingerprint for the contribution of tributaries to large boreal rivers

Organic and inorganic colloids play important roles governing the speciation, transport, and bioaccessibility of trace elements in aquatic systems. These carriers are especially important in the boreal zone, where rivers that contain high concentrations of iron and organic matter are prevalent. The distribution of trace elements amongst different colloidal species (or "speciation profile") can therefore be useful as a fingerprint to detect different trace element sources and for tracking colloid transformations, with implications for bioaccessibility. Asymmetrical flow field-flow fractionation coupled to an inductively coupled plasma mass spectrometer was applied to detect the source of trace elements based on their speciation profile along a 125-km stretch of a large river in the Canadian boreal forest. Both the concentration and proportion of bound trace elements were increased by tributary inputs: bound As, Co, Fe, Mn, Pb, U, and Zn increased monotonically from upstream to downstream, increasingly resembling the speciation profile of tributaries. Principal component (PC) analysis also revealed tributary contributions of bound Cu, Ni, Th, V, and Y reflecting their higher concentrations in tributaries, and PC scores also increased monotonically from upstream-downstream. Monotonically decreasing concentrations of mainly ionic and small (i.e. <ca. 300 Da) As, Ba, Mo, and U species were also observed from upstream-downstream.

Authigenic and Detrital Minerals in Peat Environment of Vasyugan Swamp, Western Siberia

Studies of mineral-forming processes in modern peat bogs can shed light on metal concentrations and their cycling in similar environments, especially in geological paleoanalogs. In terms of the mineralogical and geochemical evolution of peat bog environments, the Vasyugan Swamp in Western Siberia is a unique scientific object. Twelve peat samples were collected from the Vasyugan Swamp up to the depth of 275 cm at 25 cm intervals. The studied peat deposit section is represented by oligotrophic (0–100 cm), mesotrophic (100–175 cm), and eutrophic (175–275 cm) peat, and this is underlain by basal sediments (from 275 cm). About 30 minerals were detected using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The observed minerals are divided into detrital, clay, and authigenic phases. The detrital minerals found included quartz, feldspar, ilmenite, rutile, magnetite, zircon, and monazite. When passing from basal to oligotrophic bog sediments, the clay minerals changed from illite-smectite to kaolinite. Authigenic minerals are represented by carbonates (calcite and dolomite), iron (hydro-)oxides, galena, sphalerite, pyrite, chalcopyrite, Zn-Pb-S mineral, barite, baritocelestine, celestine, tetrahedrite, cassiterite, REE phosphate, etc. The regular distribution of mineral inclusions in peat is associated with the (bio)geochemical evolution of the environment. The formation of authigenic Zn, Pb and Sb sulfides is mainly confined to anaerobic conditions that exist in the eutrophic peat and basal sediments. The maximum amount of pyrite is associated with the interval of 225–250 cm, which is the zone of transition from basal sediments to eutrophic peat. The formation of carbonate minerals and the decreasing concentration of clay in the association with local sulfide formation (galena, sphalerite, chalcopyrite, stibnite) begins above this interval. The peak of specific carbonation appears in the 125–150 cm interval of the mesotrophic peat, which is characterized by pH 4.9–4.5 of pore water. Kaolinite is the dominant clay mineral in the oligotrophic peat. Gypsum, galena, chalcopyrite, sphalerite, and relicts of carbonate are noted in association with kaolinite. Changes in oxygen concentrations are reflected in newly formed mineral associations in corresponding intervals of the peat. This can be explained by the activity of microbiological processes such as the anaerobic oxidation of methane (AOM) and bacterial sulfate reduction (BSR), expressed in specific carbonatization (100–225 cm) and sulfidization (175–250 cm), respectively.

Estimating bioaccessibility of trace elements in particles suspended in the Athabasca River using sequential extraction

Employing protocols developed for polar snow and ice, water samples were collected upstream, midstream and downstream of open pit bitumen mines and upgraders along the Lower Athabasca River (AR). The purpose was to: i) estimate the bioaccessibility of trace elements associated with particulate matter in the AR using sequential extraction, and ii) determine whether their forms have been measurably impacted by industrial activities. Of the trace metals known to be enriched in bitumen (V, Ni, Mo and Re), a substantial proportion of V (78-93%) and Ni (35-81%) was found in the residual fraction representing stable minerals. In contrast, Mo and Re were partitioned mainly into more reactive forms (water soluble, acid extractable, reducible and oxidisable). Comparing the non-residual fractions in upstream versus downstream sites, only water soluble Re was significantly (P = 0.005) greater downstream of industry. In respect to the potentially toxic chalcophile elements (Cu, Pb and Tl), no measurable change was observed in Cu and Pb distribution in upstream versus downstream sites. Only residual Tl was found at upstream and midstream sites, whereas a significant proportion of Tl was also present in the reducible fraction in downstream sites. Overall, a greater proportion of trace metals in the residual fraction at midstream sites appears to be due to inputs of atmospheric dust, clearly evident in microscopic images: energy dispersive spectroscopy and x-ray diffraction analyses showed that these particles were predominantly silicates, which are assumed to have limited bioaccessibility.

Methylated arsenic species throughout a 4-m deep core from a free-floating peat island

Arsenic (As) occurs in soils mostly in inorganic forms, whereas the organic forms usually occur only in trace amounts. Peatlands are waterlogged, generally anoxic, organic soils representing the first step in coal formation; the contribution of organic vs. inorganic As species in this environment has received little research attention. Here, 57 peat samples collected throughout a 4-m deep, free-floating mire were analysed for total As and for its organic species, including dimethylarsinic acid (DMA), methylarsonic acid (MA), trimethylarsine oxide (TMAO) and arsenobetaine (AB), by HPLC-ICPMS. Aqueous trifluoroacetic acid was used as extractant, resulting in an average extraction efficiency of almost 80%. Total As concentration throughout the profile ranged between 0.2 and 9.8mg/kg_peat (mean: 1.4±1.2mg/kg_peat). Organic As species (DMA+MA+TMAO+AB) accounted, on average, for 28±10% of total As (range: 6-51%), and for 37±13% of the extracted As (range: 7-64%). The relative abundance of organoarsenicals generally followed the order DMA>TMAO~MA≫AB. A positive correlation (p<0.001) was found among all organic As compounds, whereas their concentrations were negatively correlated with total sulfur content. The submerged zone (bottom 300cm) showed average and maximum concentrations of organoarsenic compounds that were almost twice those found in the top 100cm. This study shows that significant proportions of methylated As species occur even in peat samples characterized by low total As concentration (mostly <2mg/kg). Finally, this work provides the first evidence of organoarsenic species in free-floating mires, i.e., a globally distributed but scarcely investigated ecosystem.

Origin and spatial distribution of metals in moss samples in Albania: A hotspot of heavy metal contamination in Europe

This study presents the spatial distribution of 37 elements in 48 moss samples collected over the whole territory of Albania and provides information on sources and factors controlling the concentrations of elements in the moss. High variations of trace metals indicate that the concentrations of elements are affected by different factors. Relations between the elements in moss, geochemical interpretation of the data, and secondary effects such as redox conditions generated from local soil and/or long distance atmospheric transport of the pollutants are discussed. Zr normalized data, and the ratios of different elements are calculated to assess the origin of elements present in the current moss samples with respect to different geogenic and anthropogenic inputs. Factor analysis (FA) is used to identify the most probable sources of the elements. Four dominant factors are identified, i.e. natural contamination; dust emission from local mining operations; atmospheric transport of contaminants from local and long distance sources; and contributions from air borne marine salts. Mineral particle dust from local emission sources is classified as the most important factor affecting the atmospheric deposition of elements accumulated in the current moss samples. The open slag dumps of mining operation in Albania is probably the main factor contributing to high contents of Cr, Ni, Fe, Ti and Al in the moss. Enrichment factors (EF) were calculated to clarify whether the elements in the present moss samples mainly originate from atmospheric deposition and/or local substrate materials.

Using normal ranges for interpreting results of monitoring and tiering to guide future work: A case study of increasing polycyclic aromatic compounds in lake sediments from the Cold Lake oil sands (Alberta, Canada) described in Korosi et al. (2016)

Since the publishing of the Kelly et al. papers (2009, 2010) describing elevated contaminants in snow near the Alberta oil sands, there has been a significant expansion of monitoring efforts, enhanced by $50M a year contributed by industry to a regional Joint Oil Sands Monitoring (JOSM) program. In parallel to the intensification of research and monitoring efforts, including expansion of measured indicators, techniques for chemical analysis have also become more sensitive. Both factors contribute to the increased sensitivity and power, and improve our capacity to detect any change. The increase in capability requires a counterbalance to account for trivial change. This can be done using an interpretative approach that requires contextualization of differences to meaningfully inform environmental monitoring programs and provide focus for action. Experience obtained through 25 years of involvement with Canada's Environmental Effects Monitoring (EEM) program has shown that a tiered program informed by triggers can provide the context to make decisions about monitoring priorities. Here we provide a potential interpretation framework using a case study around the Korosi et al. (2016) study which found recent increases in alkylated polycyclic aromatic compounds (aPACs) in the Cold Lake in situ oil sands area. Public contaminant profiles from the JOSM studies in the oil sands region are used to evaluate the changes using an interpretation framework based on estimated normal ranges using existing data for site-specific, local and regional (distant) levels that was modelled after the tiered Canadian EEM design.

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.

Is Unpaved Road Dust Near Fairbanks, Alaska a Health Concern? Examination of the Total and Bioaccessible Metal(loid)s

Recent studies highlight the health risks associated with toxic metal(loid)s [e.g., arsenic (As), zinc (Zn), and lead (Pb)] in dust from mining operations, urban settings, and rural roads. To have a deleterious health effect, inhaled or ingested metal(loid)s must dissolve under conditions in the lung or gastrointestinal tract. In this study, we determined total and physiologically-soluble fractions of metal(loid)s in road dust from four sites in east-central interior Alaska. Total As and antimony (Sb) were enriched up to 26.2 and 53.7, respectively in dusts relative to average crustal abundance. Several elements such as nickel (Ni), As, and Sb were highly to moderately soluble in simulated lung fluids (7-80%, 15-51%, and 5-42%, respectively). Nickel and As exceeded the EPA inhalation risk unit, which is an exposure level of minimal risk. Despite several elements being highly soluble in simulated gastric fluids, including Ni, Cu, As, and Pb, only As samples exceeded the oral reference dose for children (based on total elemental concentrations) in some samples. The highest exposure risks identified in this study are inhalation of As and Ni present in road dust and ingestion of As-containing dust, especially by children. Additional studies would be needed to further quantify the health risk posed by road dust in this region.

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.

Trace metals in the dissolved fraction (<0.45μm) of the lower Athabasca River: Analytical challenges and environmental implications

Water samples were collected on the Athabasca River (AR), upstream and downstream from bitumen mines and upgrading facilities, to identify changes in water quality due to industrial activities in this region of northern Alberta, Canada. Starting upstream of Fort McMurray and proceeding downstream ca. 100km, waters were collected in duplicate at 13 locations on the main stem of the river, as well as 5 tributary streams, using ultraclean sampling protocols developed for polar snow and ice. To estimate potential bioaccessibility, trace elements of concern (Ag, Cd, Pb, Sb, Tl) were determined in the dissolved fraction (<0.45μm) along with metals known for their enrichments in bitumen (V, Ni, Mo, Re) and those found mainly in ionic (Li, Sr) or colloidal forms (Al, Co, Cr, Fe, Ga, Mn, Th, Y). Analyses were performed in the metal-free, ultraclean SWAMP lab using quadrupole and sector-field ICP-MS. Concentrations of Ag, Cd, Pb, Sb and Tl were extremely low, not significantly more abundant downstream of industry and probably reflect "background" values. In contrast, V, Ni, Mo and Re concentrations were all significantly (p<0.05) greater downstream of industry. However, chloride also increased downstream, due to natural inputs of saline groundwaters and it is unclear whether the increases in V, Ni, Mo and Re are due to natural or anthropogenic inputs to the river. Although it had been claimed that the industrial development of the Athabasca Bituminous Sands (ABS) is a significant source of Ag, Cd, Pb, Sb and Tl to the river, our study failed to find any evidence to support this. Here we provide a first, robust (accurate and precise) description of baseline values for these trace elements in the AR, and suggest that V, Ni, Mo and Re are more valuable tracers for environmental monitoring and source assessment.

Isotopic evolution of atmospheric Pb from metallurgical processing in Flin Flon, Manitoba: Retrospective analysis using peat cores from bogs

Atmospheric Pb deposition was reconstructed using peat cores from bogs in the vicinity of Flin Flon, Manitoba, Canada, home to a zinc refinery and copper smelter. The Sask Lake (SL4-1) core was collected 85 km NW of Flin Flon and Kotyk Lake (KOL) 30 km NE. The distribution of Sr and U show that both profiles are predominantly minerotrophic (ie groundwater-fed), but the Pb concentration profile shows that Pb was received exclusively from the atmosphere. Graphs of ²⁰⁸Pb/²⁰⁶Pb against ²⁰⁶Pb/²⁰⁷Pb document atmospheric Pb contamination dating from the early to mid-1800's, well before the start of metallurgical processing (in 1930) and attributable to long-range atmospheric transport from other regions of North America. Industrial activities at Flin Flon clearly affected the concentrations, enrichment factor (calculated using Sc), and accumulation rates of Pb, but it is the similarity in isotopic composition, and contrast with crustal values (²⁰⁶Pb/²⁰⁷Pb ca. 1.20 to 1.22) which makes the connection to the Flin Flon ores. The KOL samples dating from 1925-1976 CE have a ²⁰⁶Pb/²⁰⁷Pb of 1.032 ± 0.002 (n = 11) which approach the values for the Flin Flon ores (²⁰⁶Pb/²⁰⁷Pb = 1.008). But even at SL4-1, the peat samples dating from 1925-1976 CE have a ²⁰⁶Pb/²⁰⁷Pb of 1.061 ± 0.022 (n = 18) which is well below the corresponding ratio of Canadian leaded gasoline (²⁰⁶Pb/²⁰⁷Pb = ca. 1.15). The SL4-1 site too, therefore, was clearly impacted by Pb from mining and metallurgy, despite the distance (88 km) from Flin Flon and being predominantly upwind. These two bogs not only provide the chronology of atmospheric Pb deposition for the past decades, but suggest that the extent of contamination may have been underestimated by previous studies.