Air Quality Research Division

Toronto, Canada

Air Quality Research Division

Toronto, Canada
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Wheeler A.J.,Air Health Science Division | Wheeler A.J.,Edith Cowan University | Gibson M.D.,Dalhousie University | MacNeill M.,Air Health Science Division | And 8 more authors.
Environmental Science and Technology | Year: 2014

Residential wood combustion is an important source of ambient air pollution, accounting for over 25% of fine particulate matter (PM2.5) emissions in Canada. In addition to these ambient contributions, wood smoke pollutants can enter the indoor environment directly when loading or stoking stoves, resulting in a high potential for human exposure. A study of the effectiveness of air cleaners at reducing wood smoke-associated PM2.5 of indoor and outdoor origin was conducted in 31 homes during winter 2009-10. Day 1, the residents' wood burning appliance operated as usual with no air cleaner. Days 2 and 3, the wood burning appliance was not operational and the air cleaner was randomly chosen to operate in "filtration" or "placebo filtration" mode. When the air cleaner was operating, total indoor PM2.5 levels were significantly lower than on placebo filtration days (p = 0.0001) resulting in a median reduction of 52%. There was also a reduction in the median PM2.5 infiltration factor from 0.56 to 0.26 between these 2 days, suggesting the air cleaner was responsible for increased PM2.5 deposition on filtration days. Our findings suggest that the use of an air cleaner reduces exposure to indoor PM2.5 resulting from both indoor and ambient wood smoke sources. © 2014 American Chemical Society.

PubMed | Water and Air Quality Bureau, Air Quality Research Division and Environment Canada
Type: | Journal: Environmental research | Year: 2015

A large landfill fire occurred in Iqaluit, Canada in spring/summer 2014. Air quality data were collected to characterize emissions as well as potential threats to public health. Criteria pollutants were monitored (PM2.5, O3, NO2) along with dioxins/furans, polycyclic aromatic hydrocarbons, and volatile organic compounds. Median daily dioxin/furan concentrations were 66-times higher during active burning (0.2 pg/m(3) Toxic Equivalency Quotient (TEQ)) compared to after the fire was extinguished (0.003 pg/m(3) TEQ). Other pollutants changed less dramatically. Our findings suggest that airborne concentrations of potentially harmful substances may be elevated during landfill fires even when criteria air pollutants remain largely unchanged.

DeMaleki Z.,Carleton University | Lai E.P.C.,Carleton University | Dabek-Zlotorzynska E.,Carleton University | Dabek-Zlotorzynska E.,Air Quality Research Division
Journal of Separation Science | Year: 2010

Molecularly imprinted polymer (MIP) submicron particles were synthesized, using either ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate as a cross-linker, specifically for recognition of 17β-estradiol (E2). HPLC with fluorescence detection (HPLC-FD) results showed that 90(±5)% of E2 bound onto these particles after 2 min of incubation, and 96(±3)% after long equilibrium. The binding capacity was 8(±3) μmol/g for MIP particles prepared using ethylene glycol dimethacrylate, and 33-43(±8) μmol/g for using trimethylolpropane trimethacrylate. CE separation of MIP and non-imprinted polymer particles was successful when 50mM borate buffer (pH 8.5) containing 0.005% w/v EOTrol™ LN in reverse polarity (-30 kV) was used. The electrophoretic mobilities of MIP and non-imprinted polymer particles, together with dynamic light scattering measurement of particle sizes, allowed for an estimation of their surface charges. Automated injection of E2 and particles in mixture set a lower limit of 20(±1) s on incubation time for the study of fast binding kinetics. The presence of E2 and bisphenol A (BPA) together tested the selectivity of MIP particles, when the two compounds competed for available binding cavities or sites. Addition of E2 after BPA confirmed E2 occupation of the specific binding cavities, via displacement of BPA. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Luo Y.,National Research Council Canada | Luo Y.,Air Quality Research Division | Dabek-Zlotorzynska E.,Air Quality Research Division | Celo V.,Air Quality Research Division | And 2 more authors.
Analytical Chemistry | Year: 2010

High precision silver isotope ratios in environmental samples were determined by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Purification of Ag from sample matrixes was performed by a two stage tandem column setup with use of anion and cation exchange resin, sequentially. It was found that 1% HNO3 and 3% HCl was efficient to stabilize Ag in the final purified sample digests prior to MC-ICPMS determination. Pd at 2 μg g-1 was added to both sample and Ag standard solution as a common doping matrix as well as an internal standard for mass bias correction. Mass discrimination and instrument drift were corrected by a combination of internal normalization with Pd and standard-sample-standard bracketing, without assuming identical mass bias for Pd and Ag. NIST SRM 978a (silver isotopic standard reference material) was used for method validation and subjected to column separation and sample preparation processes. A value of -0.003 ± 0.010 % for δ107/109Ag (mean and 2SD, n = 4) was obtained, confirming accurate results can be obtained using the proposed method. To the best of our knowledge, this is the first report on δ107/109Ag variations in environmental samples. Significant differences in Ag isotope ratios were found among NIST SRM 978a standard, sediment CRM PACS-2, domestic sludge SRM 2781, industrial sludge 2782, and the fish liver CRM DOLT-4. The sediment CRM PACS-2 has a very small negative δ107/109Ag value of -0.025 ± 0.012 % (2SD, n = 4). The domestic sludge SRM 2781 has a negative δ107/109Ag value of -0.061 ± 0.010 % (2SD, n = 4), whereas industrial sludge SRM 2782 has a positive δ 107/109Ag value of +0.044 ± 0.014 % (2SD, n = 4), which may indicate the contribution of Ag from different anthropogenic inputs. DOLT-4 has a much larger negative value of -0.284 ± 0.014 % (2SD, n = 4), possibly caused by biological processes. These observations confirm that Ag isotope fractionation may provide a useful tool for fingerprinting sources of Ag in the environment and for studying a wide variety of chemical and biological processes in nature. High precision of better than ±0.015 % (2SD, n = 4) obtained in real sample matrixes makes the present method well suited for monitoring small Ag isotope fractionation in nature. © Published 2010 by the American Chemical Society.

Ervens B.,University of Colorado at Boulder | Ervens B.,National Oceanic and Atmospheric Administration | Wang Y.,Arizona State University | Eagar J.,Arizona State University | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2013

Cloud and fog droplets efficiently scavenge and process water-soluble compounds and, thus, modify the chemical composition of the gas and particle phases. The concentrations of dissolved organic carbon (DOC) in the aqueous phase reach concentrations on the order of ∼10 mgC L-1 which is typically on the same order of magnitude as the sum of inorganic anions. Aldehydes and carboxylic acids typically comprise a large fraction of DOC because of their high solubility. The dissolution of species in the aqueous phase can lead to (i) the removal of species from the gas phase preventing their processing by gas phase reactions (e.g., photolysis of aldehydes) and (ii) the formation of unique products that do not have any efficient gas phase sources (e.g., dicarboxylic acids). We present measurements of DOC and select aldehydes in fog water at high elevation and intercepted clouds at a biogenically-impacted location (Whistler, Canada) and in fog water in a more polluted area (Davis, CA). Concentrations of formaldehyde, glyoxal and methylglyoxal were in the micromolar range and comprised ≤2% each individually of the DOC. Comparison of the DOC and aldehyde concentrations to those at other locations shows good agreement and reveals highest levels for both in anthropogenically impacted regions. Based on this overview, we conclude that the fraction of organic carbon (dissolved and insoluble inclusions) in the aqueous phase of clouds or fogs, respectively, comprises 2-∼40% of total organic carbon. Higher values are observed to be associated with aged air masses where organics are expected to be more highly oxidised and, thus, more soluble. Accordingly, the aqueous/gas partitioning ratio expressed here as an effective Henry's law constant for DOC (KH*DOC) increases by an order of magnitude from 7 × 103 M atm-1 to 7 × 104 M atm -1 during the ageing of air masses. The measurements are accompanied by photochemical box model simulations. These simulations are used to contrast two scenarios, i.e., an anthropogenically vs. a more biogenically impacted one as being representative for Davis and Whistler, respectively. Since the simplicity of the box model prevents a fully quantitative prediction of the observed aldehyde concentrations, we rather use the model results to compare trends in aldehyde partitioning and ratios. They suggest that the scavenging of aldehydes by the aqueous phase can reduce HO2 gas phase levels significantly by two orders of magnitude due to a weaker net source of HO 2 production from aldehyde photolysis in the gas phase. Despite the high solubility of dicarbonyl compounds (glyoxal, methylglyoxal), their impact on the HO2 budget by scavenging is <10% of that of formaldehyde. The overview of DOC and aldehyde measurements presented here reveals that clouds and fogs can be efficient sinks for organics, with increasing importance in aged air masses. Even though aldehydes, specifically formaldehyde, only comprise ∼1% of DOC, their scavenging and processing in the aqueous phase might translate into significant effects in the oxidation capacity of the atmosphere. © Author(s) 2013.

Kelly J.L.,York University | Kelly J.L.,Air Quality Research Division | Michelangeli D.V.,York University | Makar P.A.,York University | And 4 more authors.
Atmospheric Environment | Year: 2010

A kinetically based gas-particle partitioning box model is used to highlight the importance of parameter representation in the prediction of secondary organic aerosol (SOA) formation following the photo-oxidation of toluene. The model is initialized using experimental data from York University's indoor smog chamber and provides a prediction of the total aerosol yield and speciation. A series of model sensitivity experiments were performed to study the aerosol speciation and mass prediction under high NOx conditions (VOC/NOx = 0.2). Sensitivity experiments indicate vapour pressure estimation to be a large area of weakness in predicting aerosol mass, creating an average total error range of 70 μg m-3 (range of 5-145 μg m-3), using two different estimation methods. Aerosol speciation proved relatively insensitive to changes in vapour pressure. One species, 3-methyl-6-nitro-catechol, dominated the aerosol phase regardless of the vapour pressure parameterization used and comprised 73-88% of the aerosol by mass. The dominance is associated with the large concentration of 3-methyl-6-nitro-catechol in the gas-phase. The high NOx initial conditions of this study suggests that the predominance of 3-methyl-6-nitro-catechol likely results from the cresol-forming branch in the Master Chemical Mechanism taking a significant role in secondary organic aerosol formation under high NOx conditions. Further research into the yields and speciation leading to this reaction product is recommended. Crown Copyright © 2009.

Luo Y.,National Research Council Canada | Luo Y.,Air Quality Research Division | Luo Y.,University of New Brunswick | Celo V.,Air Quality Research Division | And 2 more authors.
Journal of Analytical Atomic Spectrometry | Year: 2012

First results on silver isotope fractionation observed in a number of experimental studies that mimic natural environment conditions and/or processes are reported. Precipitation of Ag as AgCl in the presence of a small amount of Cl -1 induced significant isotopic fractionation. A δ 107/109Ag value of -0.17 ± 0.03‰ (1SD, n = 3) (relative to SRM 978a Ag isotopic standard) was obtained at a 96% loss of the original aqueous Ag. Thus, during the precipitation process, the supernatant is enriched in heavy 109Ag whereas AgCl precipitate is enriched in 107Ag. A slightly positive value of 0.052 ± 0.013 (1SD, n = 3) for δ 107/109Ag obtained in lake sediment samples collected from the St. George Lake (Ontario, Canada), wherein no industrial or domestic discharge is present, corroborates with results obtained during Cl -1 precipitation laboratory experiments. This observation suggests that the natural precipitation process in the presence of Cl -1 may be a major mechanism for the observed Ag isotope fractionation in uncontaminated lake sediments. The depletion of aqueous silver and its isotope fractionation during UV photolysis experiments were not significant. Only 12-25% of Ag was lost under test conditions, suggesting that the transport of Ag from the aquatic system to the atmosphere is rather limited in the natural environment. Physical mixing of a dietary Ag supplement, which has distinct isotopic composition, with sediment CRM PACS-2 was performed in order to investigate the possibility of tracking the origin of Ag through the use of its isotope ratio information. Isotope ratios of Ag measured in these mixtures gave a well-defined mixing pattern of these two end members. Results obtained in this study suggest that the Ag isotope ratio measured by MC-ICPMS may be a useful tracer for studying the natural processes and/or tracking the origin of the anthropogenic Ag in the environment. © 2012 The Royal Society of Chemistry.

Stroud C.A.,Air Quality Research Division | Zaganescu C.,Air Quality Modelling and Application Section | Chen J.,Air Quality Modelling and Application Section | McLinden C.A.,Air Quality Research Division | And 2 more authors.
Journal of Atmospheric Chemistry | Year: 2015

A Unified Regional Air-quality Modelling System, AURAMS, was expanded to predict six toxic volatile organic compounds (VOCs) within a continental domain and two nested domains covering eastern and western Canada. The model predictions were evaluated against Environment Canada’s National Air Pollution Surveillance (NAPS) data set to assess the predictive capability of the model at daily and seasonal time scales. The predictions were also evaluated with satellite-derived column total maps for formaldehyde, carbon monoxide, and nitrogen dioxide. In general, the model showed fair to good predictive skill in terms of both correlation (R) and normalized mean bias (NMB) for benzene (R = 0.53 NMB = 26 %), formaldehyde (R = 0.73, NMB = −15 %) and acetaldehyde (R = 0.55, NMB = 29 %). For the other toxics VOCs, the model showed less predictive skill in the order 1,2,4-trimethylbenzene (R = 0.50, NMB = −41 %), 1,3-butadiene (R = 0.26, NMB = 40 %) and acrolein (R = 0.052, NMB = −51 %). The goal of this study was to apply an air quality model to assess the contribution of mobile sources to ambient levels of toxic VOCs at urban locations across Canada. The mobile source contribution varied in a complex manner for each species for different regions. For benzene and 1,2,4-trimethylbenzene, the mobile source contribution was in the range 40–65 % for major Canadian cities. The model predicted considerably lower mobile source contributions for rural locations in the Canadian Prairies, where other area sources dominate, such as the petrochemical industry. Measured concentration trends in toxics are also presented from 2004 to 2010. The primary emitted toxics declined gradually (13–16 % over 6 yr) whereas the toxic aldehydes showed no trend. © 2015 The Author(s)

Li S.-M.,Air Quality Research Division | Liggio J.,Air Quality Research Division | Graham L.,Air Quality Research Division | Graham L.,University of Canterbury | And 6 more authors.
Atmospheric Chemistry and Physics | Year: 2011

This paper presents the results of laboratory studies on the condensational uptake of gaseous organic compounds in the exhaust of a light-duty gasoline engine onto preexisting sulfate and nitrate seed particles. Significant condensation of the gaseous organic compounds in the exhaust occurs onto these inorganic particles on a time scale of 2-5 min. The amount of condensed organic mass (COM) is proportional to the seed particle mass, suggesting that the uptake is due to dissolution determined by the equilibrium partitioning between gas phase and particles, not adsorption. The amount of dissolution in unit seed mass, decreases as a power function with increased dilution of the exhaust, ranging from 0.23 g g-1 at a dilution ratio of 81, to 0.025 g -1 at a dilution ratio of 2230. It increases nonlinearly with increasing concentration of the total hydrocarbons in the gas phase (THC), rising from 0.12 g g-1 to 0.26 g-1 for a CTHC increase of 1 to 18 mg-3, suggesting that more organics are partitioned into the particles at higher gas phase concentrations. In terms of gas-particle partitioning, the condensational uptake of THC gases in gasoline engine exhaust can account for up to 30% of the total gas + particle THC. The organic mass spectrum of COM has the largest fragment at m/z 44, with mass ratios of mass fragments 43/44 and 57/44 at 0.59 and 2.91, much lower than those reported for gasoline engine primary organic aerosols. The mass fragment 44/total organic mass ratio of 0.097 indicates that COM contains large oxygenated components. By incorporating the present findings, regional air quality modelling results suggest that the condensational uptake of THC onto sulfate particles alone can be comparable to the primary particle mass under moderately polluted ambient conditions. These findings are important for modelling and regulating the air quality impacts of gasoline vehicular emissions. © 2011 Author(s).

Yassine M.M.,Air Quality Research Division | Harir M.,Helmholtz Center Munich | Dabek-Zlotorzynska E.,Air Quality Research Division | Schmitt-Kopplin P.,Helmholtz Center Munich | Schmitt-Kopplin P.,TU Munich
Rapid Communications in Mass Spectrometry | Year: 2014

RATIONALE A challenge of atmospheric particulate matter (PM) analysis is the understanding of the sources and chemistry of complex organic aerosols, especially the water-soluble organic compounds (WSOC) fraction, a key component of atmospheric fine PM (PM2.5). The sources of WSOC are not well understood and, thus, the molecular characterization of WSOC is important because it provides insight into aerosol sources and the underlying mechanisms of secondary organic aerosols formation and transformation.METHODS In this study, molecular characterization of WSOC was achieved using Fourier transform ion cyclotron resonance mass spectrometry. The aromaticity equivalent (Xc), a new parameter calculated from the assigned molecular formula, is introduced to improve the identification and characterization of aromatic and condensed aromatic compounds in WSOC. Diesel PM (DPM) and atmospheric PM samples were used to study the applicability of the proposed method.RESULTS Threshold values of Xc ≥2.5000 and Xc ≥2.7143 are proposed as unambiguous minimum criteria for the presence of aromatics and condensed aromatics, respectively. By using these criteria, 36% of precursors were defined as aromatics and condensed aromatics in the DPM. For comparison, 21% of aromatic and condensed aromatic compounds were defined using the Aromaticity Index (AI) classification. The lower estimates by the AI approach are probably due to the failure to recognize aromatics and condensed aromatics with longer alkyl chains. The estimated aromatic and condensed aromatic fractions in the atmospheric aerosol samples collected in an industrial area affected by biomass burning events were 51.2 and 50.0%, respectively.CONCLUSIONS The advantage of employing this parameter is that Xc would have a constant value for each proposed core structure regardless of the degree of alkylation, and thus visual representation and structural interpretations of the spectra become advantageous for characterizing and comparing complex samples. In addition, the proposed parameter complements the AI classification and identification of aromatic and condensed aromatic structures in complex matrices. © 2014 John Wiley & Sons, Ltd.

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