Valbona Celo

Receptor model based identification of PM2.5 sources in Canadian cities

Abstract Source apportionment of 24–hour integrated PM 2.5 chemical speciation data, collected at five Canadian urban sites, Windsor, Toronto, Montreal, Halifax, and Edmonton was performed using the receptor model, Positive Matrix Factorization (PMF). In order to determine the influences of local and regional sources, in–depth wind direction and back trajectory analyses were performed using the conditional probability function (CPF) and the potential source contribution function (PSCF). The highest PM 2.5 levels were observed in Windsor followed by Toronto and Montreal. Secondary sulfate and nitrate were the major factors contributing to the PM 2.5 mass, accounting for 41% – 61% in the five sites. These secondary factors were associated with trans–boundary emissions from Ohio, Pennsylvania, and New York. An elemental carbon (EC)–rich factor was identified in Windsor, Toronto, and Montreal, characterized by distinct EC and organic carbon (OC) profiles. The EC–rich factor accounted for 6% – 19% of the total PM 2.5 mass in summer and also appeared to be related to trans-boundary pollutants. The combined contributions of traffic and road dust ranged from 14% to 19%, with a portion of the nitrate factor also coming from vehicles. In Halifax, sea salt was the second strongest source, contributing 18% of the PM 2.5 . In Edmonton, strong correlation of volatile organic compounds with the major PM 2.5 factors suggested that local industrial sources were significant sources of secondary aerosol. Further, biomass burning contributed 12% of the PM 2.5 mass in Edmonton. Both local and regional sources were found to contribute at all sites. Thus, PM 2.5 can be reduced at all the sites through local controls. However given the significant contribution of trans–boundary contributions to the PM 2.5 mass, a substantial reduction of PM 2.5 in four of the cities will also require agreements to limit the production and transport of trans–boundary pollutants.

Cytotoxic and inflammatory potential of size-fractionated particulate matter collected repeatedly within a small urban area.

BackgroundExposure to coarse, fine, and ultrafine particles is associated with adverse population health impacts. We investigated whether size-fractionated particles collected repeatedly in the vicinity of industrial (steel mills and associated coking operations, wastewater treatment), high traffic, and residential areas display systematic differences in biological potency.MethodsParticulate matter (PM<0.1, PM0.1–0.5, PM0.5–2.5, PM2.5–10, PM>10) samples collected at sites within Windsor, Ontario, were screened for biological potency in human A549 lung epithelial and murine J774A.1 macrophage-like cells using cytotoxicity bioassays (cellular ATP, resazurin reduction, lactate dehydrogenase (LDH) release), cytokine production, and transcript profiles. Potency was determined from the slope of each dose-effect relationship.ResultsCytotoxic potency varied across size fractions and within a fraction across sites and sampling periods, suggesting that particle composition, in addition to size and mass, affected particle toxicity. While ATP and LDH profiles showed some similarity, resazurin reduction (a measure of metabolic activity) exhibited a unique pattern of response, indicating that the cytotoxicity assays were sensitive to distinct particle characteristics. Chemical speciation varied in relation to prevailing winds, consistent with enrichment of source emissions (e.g. higher metal and polycyclic aromatic hydrocarbon content downwind of the industrial site). Notwithstanding this variability, site-dependent differences in particle toxicity were evident, including greater potency of coarse fractions at the industrial site and of ultrafine particles at the traffic site (Site × Size interactions, p < 0.05). Regression of potency against particle constituents revealed correlations between resazurin reduction, induction of metal-responsive genes, and metal content, which were particularly strong for the coarse fraction, and between cytokine release and endotoxin, suggesting that these factors were important drivers of biological effects that explain, at least in part, the contrasting potencies of particles compared on an equivalent mass basis.ConclusionsThe data show that 1) particle potency and composition can exhibit significant temporal variation in relation to source contributions; 2) sources may differentially impact the potency of specific size fractions; and 3) particle constituents, notably metals and endotoxin, may elicit distinct biological responses. Together, the data are consistent with the notion that sources and composition, in addition to size and mass concentration, are relevant to particle toxicity.

Concentration and Source Origin of Trace Metals in PM2.5 Collected at Selected Canadian Sites within the Canadian National Air Pollution Surveillance Program

Airborne particulate matter (PM) is a complex mixture of thousands of organic and inorganic species that emerge from a wide range of natural and anthropogenic sources. Numerous epidemiological studies have confirmed that PM and especially the respirable fraction of PM, the PM2.5 (for particles < 2.5 μm diameter), has adverse effects on human health. Although there is no evidence to pinpoint any single feature or component of PM as the cause for the observed epidemiological effects, it is apparent that metals contribute, at least in part, to the toxic and carcinogenic effects associated with exposure to airborne PM and for this reason have been the object of several epidemiological studies (Goldoni et al. 2006; Kawata et al. 2007; Lippmann et al. 2006). In addition, trace metals are proven to be useful tracers and are extensively used to identify sources of emissions to be targeted by the emission reduction policies (Querol et al. 2001; Lee et al. 2003; Gotschi et al. 2005; Querol et al. 2006; Querol et al. 2007b; Viana et al. 2007; Jeong et al. 2008). Therefore, monitoring of elemental composition of PM has become a crucial part of air quality programs in many countries around the world.

Validation of a Simple Microwave-Assisted Acid Digestion Method Using Microvessels for Analysis of Trace Elements in Atmospheric PM2.5 in Monitoring and Fingerprinting Studies

Two microwave-assisted digestion procedures, followed by inductively coupled plasma mass spectrometry (ICP-MS) analysis, were evaluated for the determination of trace elements in fine atmospheric aerosols (PM2.5) for air monitoring purposes. The first procedure used 40%(v/v) HNO3 and a digestion program with a maximum temperature of 175 o C. The second digestion procedure provided the dissolution of silicate matrix through the use of a mixture of HNO3/HF/H3BO3 at 200 o C. Both digestion procedures employed microvessels (MicroVessel TM ), which significantly reduced the amount of reagents needed, and increased the sample throughput by two-fold. The effectiveness of both digestion procedures was studied through the analysis of NIST standard reference materials (SRM), namely SRM 2783 (PM2.5 Air Particulate Matter deposited on a polycarbonate filter membrane), and SRM 1648 (Urban Particulate Matter). The accuracy was also checked through the analysis of co-located ambient PM2.5 samples collected within the Canadian National Air Pollution Surveillance (NAPS) network. Comparison of analytical results for PM2.5 samples showed that 40% (v/v) HNO3 could dissolve most of the metals of interest to the same degree as the HNO3/HF/H3BO3 mixture. Good agreement was also obtained by comparison with Energy Dispersive X-ray Fluorescence Spectrometry (ED-XRF). The efficiency of the simple microwave digestion procedure (no HF) was not dependent on the origin, mass loading, or elemental composition of the analyzed samples, thus it is quite suitable for monitoring purposes. However, the total dissolution of several trace elements such as Ti, Cr and U in PM2.5, and Ti, Cr, Al, lanthanides, and Sb in coarse fractions of PM (PM10-2.5) would require digestion in the presence of HF.

Accurate and precise determination of silver isotope fractionation in environmental samples by multicollector-ICPMS.

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% HNO(3) and 3% HCl was efficient to stabilize Ag in the final purified sample digests prior to MC-ICPMS determination. Pd at 2 mug 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 per thousand for delta(107/109)Ag (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 delta(107/109)Ag 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 delta(107/109)Ag value of -0.025 +/- 0.012 per thousand (2SD, n = 4). The domestic sludge SRM 2781 has a negative delta(107/109)Ag value of -0.061 +/- 0.010 per thousand (2SD, n = 4), whereas industrial sludge SRM 2782 has a positive delta(107/109)Ag value of +0.044 +/- 0.014 per thousand (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 per thousand (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 per thousand (2SD, n = 4) obtained in real sample matrixes makes the present method well suited for monitoring small Ag isotope fractionation in nature.

Chemical Characterization of Exhaust Emissions from Selected Canadian Marine Vessels: The Case of Trace Metals and Lanthanoids

This paper reports the chemical composition of exhaust emissions from the main engines of five ocean going cargo vessels, as they traveled in Canadian waters. The emission factors (EFs) of PM2.5 and SO2 for vessels tested on various intermediate fuel oils (IFO), ranged from 0.4 to 2.2 g kW(-1) hr(-1) and 4.7 to 10.3 g kW(-1) hr(-1), respectively, and were mainly dependent on the content of sulfur in the fuel. Average NOx, CO, and CO2 EFs for these tests were 12.7, 0.45, and 618 g kW(-1) hr(-1), respectively and were generally below benchmark values commonly used by regulatory agencies. The composition of PM2.5 was dominated by hydrated sulfates, organic carbon and trace metals which accounted for 80-97% of total PM2.5 mass. A substantial decrease of measured emission factors for PM2.5 and SO2 was observed when the fuel was changed from IFO to marine diesel oil (MDO), in one of the tested vessels. The main component of PM2.5 in this case was organic carbon accounting for 65% of PM2.5 mass. In addition to commonly reported pollutants, this study presents EFs of the lanthanoid elements and showed that their distribution patterns in ship-exhaust PM2.5 were very similar to the PM2.5 emitted by oil refining facilities. Hence, using La:Ce:V tertiary diagrams and La/V ratios is necessary to distinguish ship plumes from primary emissions related to accidental and/or routine operation of oil-refining industry.

An improved method for determination of lanthanoids in environmental samples by inductively coupled plasma mass spectrometry with high matrix introduction system.

The capability of ICP-MS equipped with the high matrix introduction system (HMI) for accurate analysis of lanthanoids in environmental samples was investigated. Compared to the conventional operation, the amounts of oxide and hydroxide molecular species formed in the plasma were reduced by up to 5 times. The relative yields of oxides did not exceed 0.02% for BaO(+) species and were as low as 0.3% for lanthanoids with the highest oxide-formation rates (LaO(+), CeO(+), PrO(+) and NdO(+)). Hydroxide formation was less than 0.02% when HMI system was used. In addition, two digestion procedures were evaluated by the analysis of standard reference materials (SRMs) of different matrices. The digestion efficiency and limits of detection (LOD) were improved when samples were digested with a mixture of HNO(3)/H(2)O(2)/HCl/HF, and HF was removed by evaporation in presence of concentrated HCl. Using this procedure and HMI-ICP-MS analysis, LOD ranged from 0.1 μg kg(-1) to 6 μg kg(-1). Recoveries ranged from 85 to 115% for La to Ho and from 75 to 85% for the other lanthanoids. Relative standard deviations for replicate analysis of SRMs were less than 10%.

High precision determination of silver isotope ratios in commercial products by MC-ICP-MS

Silver isotope ratios in several fortified commercial products were determined by multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). Mass discrimination and instrument drift were corrected for by a combination of internal normalization with Pd and standard-sample-standard bracketing, without assuming identical mass bias for Pd and Ag. The certified value of 1.07638 for 107Ag/109Ag in NIST SRM 978a was used for mass bias correction of 106Pd/108Pd in two adjacent solutions of SRM 978a. Their average was then used for mass bias correction to calculate the mass bias corrected Ag isotope ratio in the sample. An approximately 2.5-fold improvement in precision of determination of δ107/109Ag was obtained with the use of the proposed technique compared to data obtained solely with a standard-sample-standard bracketing approach. Internal and external precisions (2SD) of ±0.05‰ (n = 10) and ±0.04‰ (n = 19) for δ107/109Ag were obtained, suitable for the detection of varying Ag isotope abundances in commercial products fortified with Ag. Amongst the commercial products examined, no significant differences were detected in Ag isotopic compositions among NIST 978a standard, Ag high purity metal (Johnson Matthey Plc), Ag Nanopowder (Sigma-Aldrich) and Silversoft socks. Significant differences in Ag isotope ratios were found among NIST SRM 978a standard, a colloidal Ag dietary supplement, decanethiol functionalized Ag nanoparticles and X-static socks. The X-static socks and decanethiol functionalized Ag nanoparticles have negative δ107/109Ag values of −0.08 ± 0.05‰ and −0.15 ± 0.02‰ (2SD, n = 4), respectively, and the colloidal Ag dietary supplement has +0.83 ± 0.06‰ (2SD, n = 4). These observations suggest that such data may provide a useful tool for fingerprinting sources of Ag in the environment.

Air toxics in Canada measured by the National Air Pollution Surveillance (NAPS) program and their relation to ambient air quality guidelines

ABSTRACT This study reports ambient concentrations of 63 air toxics that were measured in Canada by the National Air Pollution Surveillance (NAPS) program over the period 2009–2013. Measured concentrations are compared with ambient air quality guidelines from Canadian jurisdictions, and compounds that exceeded guidelines are identified and discussed. Although this study does not assess risk or cumulative effects, air toxics that approached guidelines are also identified so that their potential contribution to ambient air toxics pollution can be considered. Eleven air toxics exceeded at least one guideline, and an additional 16 approached guidelines during the study period. Four compounds were measured using methods whose detection limits exceeded a guideline value, three of which could not be compared with guidelines, since they were not detected in any samples. The assessment of several metal(loid) concentrations is tentative, since they were measured only in fine particulate matter (PM) but compared with guidelines based on coarse or total PM. Improvements to sampling and analysis techniques for the latter compounds as well as for those whose methods are subject to known uncertainties would improve confidence in reported concentrations and their relation to applicable guidelines. Analysis of sampling strategies for all compounds found to exceed or approach guidelines would contribute to ensuring that their spatiotemporal coverage is adequate. Examination of the air toxics not measured by NAPS but having guidelines in Canadian jurisdictions or being included in other programs such as the U.S. National-Scale Air Toxics Assessment (NATA) would contribute to ensuring that the full suite of pollutants relevant to ambient air quality in Canada is subject to adequate study. The results of this study can be applied to evaluating the effectiveness of toxic substances management in Canada. Implications: Recent measurements of 63 air toxics in Canada by the National Air Pollution Surveillance (NAPS) program showed that 11 compounds exceeded daily or annual ambient air quality guidelines and that an additional 16 compounds approached such guidelines within an order of magnitude. The results of this study can be applied to evaluating the effectiveness of toxic substances management in Canada and to identifying compounds that merit further investigation.

Development of a hydrophilic interaction liquid chromatography–mass spectrometry method for detection and quantification of urea thermal decomposition by-products in emission from diesel engine employing selective catalytic reduction technology

The use of urea based selective catalytic reduction (SCR) technology for the reduction of NOx from the exhaust of diesel-powered vehicles has the potential to emit at least six thermal decomposition by-products, ammonia, and unreacted urea from the tailpipe. These compounds may include: biuret, dicyandiamine, cyanuric acid, ammelide, ammeline and melamine. In the present study, a simple, sensitive and reliable hydrophilic interaction liquid chromatography (HILIC)-electrospray ionization (ESI)/mass spectrometry (MS) method without complex sample pre-treatment was developed for identification and determination of urea decomposition by-products in diesel exhaust. Gradient separation was performed on a SeQuant ZIC-HILIC column with a highly polar zwitterionic stationary phase, and using a mobile phase consisting of acetonitrile (eluent A) and 15 mM ammonium formate (pH 6; eluent B). Detection and quantification were performed using a quadrupole ESI/MS operated simultaneously in negative and positive mode. With 10 μL injection volume, LODs for all target analytes were in the range of 0.2-3 μg/L. The method showed a good inter-day precision of retention time (RSD<0.5%) and peak area (RSD<3%). Satisfactory extraction recoveries from spiked blanks ranged between 96 and 98%. Analyses of samples collected during transient chassis dynamometer tests of a bus engine equipped with a diesel particulate filter (DPF) and urea based SCR technology showed the presence of five target analytes with cyanuric acid and ammelide the most abundant compounds in the exhaust.