This air synthesis review presents the current state of knowledge on the sources, fates, and effects for polycyclic aromatic compounds (PACs) and related chemicals released to air in the oil sands ...region (OSR) in Alberta, Canada. Through the implementation of the Joint Canada–Alberta Oil Sands Monitoring Program in 2012 a vast amount of new information on PACs has been acquired through directed monitoring and research projects and reported to the scientific community and public. This new knowledge addresses questions related to cumulative effects and informs the sustainable management of the oil sands resource while helping to identify gaps in understanding and priorities for future work. As a result of this air synthesis review on PACs, the following topics have been identified as new science priorities: (i) improving emissions reporting to better account for fugitive mining emissions of PACs that includes a broader range of PACs beyond the conventional polycyclic aromatic hydrocarbons (PAHs) including, inter alia, alkylated-PAHs (alk-PAHs), dibenzothiophene (DBT), alk-DBTs, nitro-PAHs, oxy-PAHs including quinones and thia- and aza-arenes; (ii) improving information on the ambient concentrations, long-range transport, and atmospheric deposition of these broader classes of PACs and their release (with co-contaminants) from different types of mining activities; (iii) further optimizing electricity-free and cost-effective approaches for assessing PAC deposition (e.g., snow sampling, lichens, passive ambient sampling) spatially across the OSR and downwind regions; (iv) designing projects that integrate monitoring efforts with source attribution models and ecosystem health studies to improve understanding of sources, receptors, and effects; (v) further optimizing natural deposition archives (e.g., sediment, peat, tree rings) and advanced forensic techniques (e.g., isotope analysis, marker compounds) to provide better understanding of sources of PACs in the OSR over space and time; (vi) conducting process research to improve model capabilities for simulating atmospheric chemistry of PACs and assessing exposure to wildlife and humans; and (vii) developing tools and integrated strategies for assessing cumulative risk to wildlife and humans by accounting for the toxicity of the mixture of chemicals in air rather than on a single compound basis.
Cette revue de synthèse sur l’air présente l’état actuel des connaissances sur les sources, le devenir et les effets des composés aromatiques polycycliques (CAP) et des produits chimiques voisins rejetés dans l’air dans la région des sables bitumineux (RSB) en Alberta, Canada. Par la mise en oeuvre du Programme de surveillance des sables bitumineux Alberta-Canada (PSSBAC) en 2012, une quantité énorme de nouvelles informations sur les CAP a été acquise grâce à la surveillance sur demande et à des projets de recherche et a été signalée à la communauté scientifique et au public. Cette nouvelle connaissance touche les questions liées aux effets cumulatifs et renseigne sur la gestion durable de la ressource des sables bitumineux tout en aidant à signaler les écarts dans la compréhension et à établir les priorités pour les recherches futures. Grâce à cette revue de synthèse sur l’air axée sur les CAP, les sujets suivants ont été relevés comme étant les nouvelles priorités scientifiques : (i) améliorer les rapports sur les émissions afin de mieux rendre compte des émissions fugitives minières de CAP pour ainsi inclure une gamme plus large de CAP au-delà des hydrocarbures aromatiques polycycliques (HAP) conventionnels, y compris, entre autres, les HAP alkylés, le dibenzothiophène (DBT), les DBT alkylés, les HAP nitrés, les hydroxy HAP incluant les quinones, les thia-et aza-arènes; (ii) améliorer les informations sur les concentrations ambiantes, le transport à grande distance et le dépôt atmosphérique de ces classes plus larges de CAP et leur rejet (avec co-contaminants) provenant des différents types d’activités minières; (iii) optimiser davantage les approches sans électricité et rentables pour évaluer les dépôts de CAP (p. ex., l’échantillonnage de neige, les lichens, l’échantillonnage passif en milieu ambiant) dans l’espace à travers la RSB et les régions en aval; (iv) concevoir des projets qui intègrent les efforts de surveillance avec des modèles d’attribution des sources et des études de santé d’écosystème pour mieux comprendre les sources, les récepteurs et les effets; (v) optimiser davantage les archives naturelles de dépôts (p. ex., les sédiments, la tourbe, les anneaux de croissance d’arbre) et les techniques médico-légales avancées (p. ex., l’analyse isotopique, les composés marqueurs) pour offrir une meilleure compréhension des sources de CAP dans la RSB dans l’espace et le temps; (vi) mener des recherches de processus pour améliorer les capacités des modèles à simuler la chimie atmosphérique des CAP et à évaluer l’exposition de la faune et des humains; et (vii) développer des outils et des stratégies intégrées pour évaluer le risque cumulé à la faune et aux humains en prenant en compte la toxicité du mélange de produits chimiques dans l’air plutôt que sur une base d’un composé seul.
The Cleveland airshed comprises a complex mixture of industrial source emissions that contribute to periods of non-attainment for fine particulate matter (PM2.5) and are associated with increased ...adverse health outcomes in the exposed population. Specific PM sources responsible for health effects however are not fully understood. Size-fractionated PM (coarse, fine, and ultrafine) samples were collected using a ChemVol sampler at an urban site (G.T. Craig (GTC)) and rural site (Chippewa Lake (CLM)) from July 2009 to June 2010, and then chemically analyzed. The resulting speciated PM data were apportioned by EPA positive matrix factorization to identify emission sources for each size fraction and location. For comparisons with the ChemVol results, PM samples were also collected with sequential dichotomous and passive samplers, and evaluated for source contributions to each sampling site. The ChemVol results showed that annual average concentrations of PM, elemental carbon, and inorganic elements in the coarse fraction at GTC were ∼2, ∼7, and ∼3 times higher than those at CLM, respectively, while the smaller size fractions at both sites showed similar annual average concentrations. Seasonal variations of secondary aerosols (e.g., high NO3− level in winter and high SO42− level in summer) were observed at both sites. Source apportionment results demonstrated that the PM samples at GTC and CLM were enriched with local industrial sources (e.g., steel plant and coal-fired power plant) but their contributions were influenced by meteorological conditions and the emission source's operation conditions. Taken together the year-long PM collection and data analysis provides valuable insights into the characteristics and sources of PM impacting the Cleveland airshed in both the urban center and the rural upwind background locations. These data will be used to classify the PM samples for toxicology studies to determine which PM sources, species, and size fractions are of greatest health concern.
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•PM sources in the Cleveland airshed varied across regions and with seasons.•Local industrial source impacts in the urban site were higher than the rural site.•Local industrial sources were mostly emitted from steel and coal-fired power plants.•Local industrial source impacts were associated with meteorological conditions.
The Cleveland airshed was enriched with local industrial sources but their contributions were influenced by meteorological conditions and emission source operation conditions.
A technique that couples lead (Pb) isotopes and multi-element concentrations with meteorological analysis was used to assess source contributions to precipitation samples at the Bondville, Illinois ...USA National Trends Network (NTN) site. Precipitation samples collected over a 16month period (July 1994–October 1995) at Bondville were parsed into six unique meteorological flow regimes using a minimum variance clustering technique on back trajectory endpoints. Pb isotope ratios and multi-element concentrations were measured using high resolution inductively coupled plasma‐sector field mass spectrometry (ICP-SFMS) on the archived precipitation samples. Bondville is located in central Illinois, ~250km downwind from smelters in southeast Missouri. The Mississippi Valley Type ore deposits in Missouri provided a unique multi-element and Pb isotope fingerprint for smelter emissions which could be contrasted to industrial emissions from the Chicago and Indianapolis urban areas (~125km north and east, of Bondville respectively) and regional emissions from electric utility facilities. Differences in Pb isotopes and element concentrations in precipitation corresponded to flow regime. Industrial sources from urban areas, and thorogenic Pb from coal use, could be differentiated from smelter emissions from Missouri by coupling Pb isotopes with variations in element ratios and relative mass factors. Using a three endmember mixing model based on Pb isotope ratio differences, industrial processes in urban airsheds contributed 56±19%, smelters in southeast Missouri 26±13%, and coal combustion 18±7%, of the Pb in precipitation collected in Bondville in the mid-1990s.
► Differences in Pb isotope ratios and multi-element concentrations quantified in event precipitation samples from Illinois ► High precision Pb isotope ratios directly measured on the archived precipitation samples using sector field ICP-MS ► Utilized unique isotopic fingerprint of Pb of smelter emissions from southeast Missouri for source attribution ► Pb isotope ratio and concentration results coupled with meteorological based cluster analysis ► Contributions from smelter derived Pb versus urban airsheds and fossil fuel sources assessed.
Cairpol and Aeroqual air quality sensors measuring CO, CO
, NO
, and other species were tested in fresh biomass burning plumes in field and laboratory environments. We evaluated sensors by comparing ...1-minute sensor measurements to collocated reference instrument measurements. Sensors were evaluated based on the coefficient of determination (
) between the sensor and reference measurements, by the accuracy, collocated precision, root mean square error (RMSE), and other metrics. In general, CO and CO
sensors performed well (in terms of accuracy and
values) compared to NO
sensors. Cairpol CO and NO
sensors had better sensor-versus-sensor agreement (e.g., collocated precision) than Aeroqual CO and NO
sensors of the same species. Tests of other sensors (e.g., NH
, H
S, VOC, NMHC) provided more inconsistent results and need further study. Aeroqual NO
sensors had an apparent O
interference that was not observed in the Cairpol NO
sensors. Although the sensor accuracy lags that of reference-level monitors, with location-specific calibrations they have the potential to provide useful data about community air quality and personal exposure to smoke impacts.
Mercury (Hg) emissions from biomass burning (BB) are an important source of atmospheric Hg and a major factor driving the interannual variation of Hg concentrations in the troposphere. The greatest ...fraction of Hg from BB is released in the form of elemental
. However, little is known about the fraction of Hg bound to particulate matter (Hg
) released from BB, and the factors controlling this fraction are also uncertain. In light of the aims of the Minamata Convention to reduce intentional Hg use and emissions from anthropogenic activities, the relative importance of Hg emissions from BB will have an increasing impact on Hg deposition fluxes. Hg speciation is one of the most important factors determining the redistribution of Hg in the atmosphere and the geographical distribution of Hg deposition. Using the latest version of the Global Fire Emissions Database (GFEDv4.1s) and the global Hg chemistry transport model, ECHMERIT, the impact of Hg speciation in BB emissions, and the factors which influence speciation, on Hg deposition have been investigated for the year 2013. The role of other uncertainties related to physical and chemical atmospheric processes involving Hg and the influence of model parametrisations were also investigated, since their interactions with Hg speciation are complex. The comparison with atmospheric Hg
concentrations observed at two remote sites, Amsterdam Island (AMD) and Manaus (MAN), in the Amazon showed a significant improvement when considering a fraction of Hg
from BB. The set of sensitivity runs also showed how the quantity and geographical distribution of Hg
emitted from BB has a limited impact on a global scale, although the inclusion of increasing fractions Hg
does limit
availability to the global atmospheric pool. This reduces the fraction of Hg from BB which deposits to the world's oceans from 71 to 62 %. The impact locally is, however, significant on northern boreal and tropical forests, where fires are frequent, uncontrolled and lead to notable Hg inputs to local ecosystems. In the light of ongoing climatic changes this effect could be potentially be exacerbated in the future.
Wildland fires are a major source of gases and aerosols, and the production, dispersion, and transformation of fire emissions have significant ambient air quality impacts and climate interactions. ...The increase in wildfire area burned and severity across the United States and Canada in recent decades has led to increased interest in expanding the use of prescribed fires as a forest management tool. While the primary goal of prescribed fire use is to limit the loss of life and property and ecosystem damage by constraining the growth and severity of future wildfires, a potential additional benefit of prescribed fire - reduction in the adverse impacts of smoke production and greenhouse gas (GHG) emissions - has recently gained the interest of land management agencies and policy makers in the United States and other nations. The evaluation of prescribed fire/wildfire scenarios and the potential mitigation of adverse impacts on air quality and GHGs requires fuel layer specific pollutant emission factors (EFs) for fire prone forest ecosystems. Our study addresses this need with laboratory experiments measuring EFs for carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), ethyne (C2H2), formaldehyde (H2CO), formic acid (CH2O2), hydrogen cyanide (HCN), fine particulate matter (PM2.5), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), and total reduced sulfur (TRS) for the burning of individual fuel components from three forest ecosystems which account for a large share of wildfire burned area and emissions in the western United States and Canada - Douglas fir, ponderosa pine, and black spruce/jack pine.
•Emission factors (EF) from burning of fuel components of three forest ecosystems.•EF for EPA criteria pollutants PM2.5, CO, NOX, and SO2.•EF for O3 precursors C2H2 and H2CO.•EF for GHGs CO2 and CH4.•Data to evaluate land management strategies addressing increased fire activity.
Event-based precipitation samples were collected at a downtown industrial and a predominantly upwind rural location in the Cleveland, Ohio metropolitan area from July 2009 through December 2010 to ...investigate the potential local total mercury (Hg) wet deposition enhancement in a region with a high concentration of coal combustion sources. Total Hg wet deposition for the 18-month period was 6.8 μg m−2 (n = 81) at the rural site and 10.7 μg m−2 (n = 98) at the urban site demonstrating a significant (p = 0.046) 37% enhancement in deposition between the two sites. Large deposition events (>0.2 μg m−2) occurred predominantly from May through October (n = 16 (urban), n = 10 (rural)) and represented from 2 to 8% of total 18-month deposition per event. At the downtown urban site, the average Hg precipitation concentration was 53% higher for these large deposition events. Concurrently measured precipitation events delivered in aggregate 2.4 times more total Hg wet deposition to the urban site compared to the rural site. Hg rainfall concentrations for concurrent events with similar precipitation depth were 2–4 times higher at the urban site and suggest scavenging of local Hg emissions. Further evaluation of these events revealed 83% more total Hg deposition at the urban site from January to December 2010 compared to July to December 2009, while there was 26% more at the rural site during these same time periods. The larger increase in deposition at the urban site in 2010 may be evidence of increased local emissions from sources that were known to be offline during this study period because of an economic recession.
•Total Hg event wet deposition was sampled at a rural and urban site in Cleveland, OH.•In the 18-month period the urban site received 37% more Total Hg wet deposition.•Concurrent events delivered 2.4 times more Total Hg wet deposition to the urban site.•The increased 2010 urban site deposition may reflect local post-recession emissions.
Extensive exploration of event precipitation data in the Ohio River Valley indicates that coal combustion emissions play an important role in mercury (Hg) wet deposition. During July−September 2006, ...an intensive study was undertaken to discern the degree of local source influence. Source−receptor relationships were explored by establishing a set of wet deposition sites in and around Steubenville, Ohio. For the three month period of study, volume-weighted mean Hg concentrations observed at the eight sites ranged from 10.2 to 22.3 ng L−1, but this range increased drastically on an event basis with a maximum concentration of 89.4 ng L−1 and a minimum concentration of 4.1 ng L−1. A subset of events was explored in depth, and the degree of variability in Hg concentrations between sites was linked to the degree of local source enhancement. Samples collected at sites less than 1 km from coal-fired utility stacks (near-field) exhibited up to 72% enhancement in Hg concentrations over regionally representative samples on an event basis. Air mass transport and precipitating cell histories were traced in order to evaluate relationships between local point sources and receptor sites. It was found that the interaction of several dynamic atmospheric parameters combined to favor local Hg concentration enhancement over the more regional contribution. When significant meteorological factors (wind speed at time of maximum rain rate, wind speed 24 h prior to precipitation, mixing height, and observed ceiling) were explored, it was estimated that during summertime precipitation, 42% of Hg concentration in near-field samples could be attributed to the adjacent coal-fired utility source.
We describe the development of a model for transport and photochemistry of atmospheric mercury at the regional scale, along with an application to the eastern United States and adjacent Atlantic ...Ocean and Gulf of Mexico, and comparison with aircraft‐based measurements in Florida. The model is the Community Multiscale Air Quality model (CMAQ) with modifications to include an integrated solution for gas phase and aqueous photochemistry. The expanded chemistry includes O3, NOx, organics, sulfur, halogens and mercury. Divalent reactive gaseous mercury (RGM) is formed slowly through gas phase reactions and removed rapidly by aqueous reactions in cloud water. Model results show that elevated RGM (up to 260 pg m−3) forms intermittently over the Atlantic Ocean in air masses that have a cloud‐free history. Aircraft measurements in Florida show RGM varying between 10 and 250 pg m−3 and increasing with altitude, a pattern that is consistent with model results. Ambient RGM would increase by 50% if aqueous reduction reactions were omitted. The model predicts that ambient elemental mercury and RGM anticorrelate in regions where RGM is produced photochemically and correlate in regions dominated by direct emissions. Model results also suggest positive correlations between RGM and SO2, reactive nitrogen and H2O2, which may be used to identify photochemically produced versus directly emitted RGM. RGM in the model is strongly correlated with O3 during pollution events, and ozone formation from anthropogenic precursors is predicted to cause a significant increase in RGM.
A field study was conducted to evaluate the performance of a Semi-continuous Elements in Aerosol Sampler-III (SEAS-III), designed to collect ambient PM
2.5 aerosol samples at a time resolution of 30
...min for elemental concentration measurements. Two identical but modified SEAS-III samplers were operated for four continuous weeks in Dearborn, MI, during July–August 2007. A total of 2308 samples were collected from the two samplers. Sampling completeness from the primary and duplicate samplers was 90% and 84%, respectively. All of the collected samples were analyzed for dilute acid-extractable trace metal concentrations using HR-ICPMS.
A total of 878 collection time-matched sample pairs were available to evaluate whole-system uncertainty from collocated concentration measurements. The collocated precision for the 27 studied elements (Al, As, Ba, Ca, Cd, Ce, Cs, Cu, Fe, Ge, K, La, Mg, Mn, Mo, Na, P, Pb, Rb, S, Sb, Se, Sn, Sr, Ti, V, and Zn) varied between 9% and 40%. Twenty elements showed precision better than 25%. Uncertainty estimates from propagation of errors compared well with the whole-system uncertainty values for all minor aerosol elements studied. SEAS-III measurements of As, Cd, Ge, K, La, Mn, Mo, Na, Rb, Se, Sb, Sr, Ti, V, and Zn correlated well (
r
>
0.8) with a FRM equivalent PM
2.5 integrated filter sampling method. Based on these measurements, collection efficiency of SEAS-III was estimated to be 87
±
16%. Solubility of particles in the collection medium (water) was identified as a possible reason for low recovery of Al, Fe, Pb, Sb, and Sn.
► SEAS-III offers trace element concentrations at sub-hourly resolution. ► Two modified SEAS-III were collocated and results compared against FRM data. ► Most elements in primary particle emissions compared well. ► Precision and accuracy of elements from SEAS-III are reported for the first time. ► Collection efficiency of SEAS-III was estimated to be 87
±
16%.
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