Browsing by Author "Tokarek, T. W."
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Item Open Access Biogenic Emissions and Nocturnal Ozone Depletion Events at the Amphitrite Point Observatory on Vancouver Island(Taylor and Francis, 2017-04-11) Tokarek, T. W.; Brownsey, D. K.; Jordan, N.; Garner, N. M.; Ye, C. Z.; Assad, F. V.; Peace, A.; Schiller, C. L.; Mason, R. H.; Vingarzan, R.; Osthoff, H. D.Routine monitoring stations on the west coast of North America serve to monitor baseline levels of criteria pollutants such as ozone (O3) arriving from the Pacific Ocean. In Canada, the Amphitrite Point Observatory (APO) on Vancouver Island has been added to this network to provide regional baseline measurements. In 2014, McKendry, I. G., Christensen, E., Schiller, C., Vingarzan, R., Macdonald, A. M., & Li, Y. (2014) reported frequent nocturnal O3 depletion events (ODEs) at APO that generally correlated with alongshore winds, elevated concentrations of carbon dioxide (CO2), and stable boundary layer conditions but the cause (causes) for this remains (remain) unclear. This manuscript presents results from the Ozone-depleting Reactions in a Coastal Atmosphere (ORCA) campaign, which took place in July 2015 to further investigate ODEs at APO. In addition to the long-term measurements at the site (e.g., CO2 and O3 mixing ratios), abundances of biogenic volatile organic compounds (BVOC) and aerosol size distributions were quantified. On the majority of measurement nights, ODEs were observed and characterized by a simultaneous increase in CO2 and BVOC abundances, in particular of limonene, a terpene 2.5 times more reactive with respect to oxidation by O3 than other monoterpenes. Back trajectory calculations showed that ODEs occurred mainly in air masses originating from the west-northwest where the air would have travelled parallel to the coastline and above kelp forests. Head-space analyses of seaweed samples showed that bull kelp is a source of gas-phase limonene, consistent with its high relative abundance in air masses from the west-northwest sector. However, the enhanced terpene and CO2 content showed that the air likely also came in contact with terrestrial vegetation via mesoscale transport phenomena (such as slope flows and land–sea breeze circulations) that were generally poorly captured by the back trajectories. The absence of aerosol growth during ODEs indicates that dry deposition is likely the primary O3 loss mechanism.Item Open Access Biogenic emissions and nocturnal ozone depletion events at the Amphitrite Point Observatory on Vancouver Island(Taylor & Francis, 2017-04-11) Tokarek, T. W.; Brownsey, D. K.; Jordan, N.; Garner, N. M.; Ye, C. Z.; Assad, F. V.; Peace, A.; Schiller, C. L.; Mason, R. H.; Vingarzan, R.; Osthoff, H. D.Routine monitoring stations on the west coast of North America serve to monitor baseline levels of criteria pollutants such as ozone (O3) arriving from the Pacific Ocean. In Canada, the Amphitrite Point Observatory (APO) on Vancouver Island has been added to this network to provide regional baseline measurements. In 2014, McKendry and co-workers reported frequent nocturnal O3 depletion events (ODEs) at APO that generally correlated with alongshore winds, elevated concentrations of carbon dioxide (CO2) and stable boundary layer conditions, but whose cause (or causes) has (have) remained unclear. This manuscript presents results from the Ozone-depleting Reactions in a Coastal Atmosphere (ORCA) campaign, which took place in July, 2015 to further investigate ODEs at APO. In addition to the long-term measurements at the site (e.g., of CO2 and O3 mixing ratios), abundances of biogenic volatile organic compounds (BVOC) and aerosol size distributions were quantified. ODEs were observed on the majority of measurement nights and were characterized by a simultaneous increase of CO2 and BVOC abundances, in particular of limonene, a terpene 2.5 more reactive with respect to oxidation of O3 than other monoterpenes. Back trajectory calculations showed that ODEs occurred mainly in air masses that originated from the WNW where the air would have travelled parallel to the coastline and above kelp forests. Head space analyses of sea weed samples showed that bull kelp is a source of gas-phase limonene, consistent with its high relative abundance in air masses from the WNW sector. However, the enhanced terpene and CO2 content showed that the air likely also came in contact with terrestrial vegetation via mesoscale transport phenomena (such as slope flows and land-sea breeze circulations) that were generally poorly captured by the back trajectories. This absence of aerosol growth during ODEs indicates that dry deposition is likely the primary O3 loss mechanism.Item Open Access Efficient photochemical generation of peroxycarboxylic nitric anhydrides with ultraviolet light-emitting diodes(European Geosciences Union, 2015-07-08) Rider, N. D.; Taha, Y. M.; Odame-Ankrah, C. A.; Huo, J. A.; Tokarek, T. W.; Cairns, E.; Moussa, S. G.; Liggio, J.; Osthoff, H. D.Photochemical sources of peroxycarboxylic nitric anhydrides (PANs) are utilized in many atmospheric measurement techniques for calibration or to deliver an internal standard. Conventionally, such sources rely on phosphor-coated low-pressure mercury (Hg) lamps to generate the UV light necessary to photo-dissociate a dialkyl ketone (usually acetone) in the presence of a calibrated amount of nitric oxide (NO) and oxygen (O2). In this manuscript, a photochemical PAN source in which the Hg lamp has been replaced by arrays of ultraviolet light-emitting diodes (UV-LEDs) is described. The output of the UV-LED source was analyzed by gas chromatography (PAN-GC) and thermal dissociation cavity ring-down spectroscopy (TD-CRDS). Using acetone, diethyl ketone (DIEK), diisopropyl ketone (DIPK), or di-n-propyl ketone (DNPK), respectively, the source produces peroxyacetic (PAN), peroxypropionic (PPN), peroxyisobutanoic (PiBN), or peroxy-n-butanoic nitric anhydride (PnBN) from NO in high yield (> 90 %). Box model simulations with a subset of the Master Chemical Mechanism (MCM) were carried out to rationalize product yields and to identify side products. The present work demonstrates that UV-LED arrays are a viable alternative to current Hg lamp setups.Item Open Access A gas chromatograph for quantification of peroxycarboxylic nitric anhydrides calibrated by thermal dissociation cavity ring-down spectroscopy(European Geosciences Union, 2014-10-01) Tokarek, T. W.; Huo, J. A.; Odame-Ankrah, C. A.; Hammoud, D.; Taha, Y. M.; Osthoff, H. D.The peroxycarboxylic nitric anhydrides (PANs, molecular formula: RC(O)O2NO2) can readily be observed by gas chromatography (PAN-GC) coupled to electron capture detection. Calibration of a PAN-GC remains a challenge, because the response factors differ for each of the PANs, and because their synthesis in sufficiently high purity is non-trivial, in particular for PANs containing unsaturated side chains. In this manuscript, a PAN-GC and its calibration using diffusion standards, whose output was quantified by blue diode laser thermal dissociation cavity ring-down spectroscopy (TD-CRDS), are described. The PAN-GC peak areas correlated linearly with total peroxy nitrate (ΣPN) mixing ratios measured by TD-CRDS (r > 0.96). Accurate determination of response factors required the concentrations of PAN impurities in the synthetic standards to be subtracted from ΣPN. The PAN-GC and its TD-CRDS calibration method were deployed during ambient air measurement campaigns in Abbotsford, BC, from 20 July to 5 August 2012, and during the Fort McMurray Oil Sands Strategic Investigation of Local Sources (FOSSILS) campaign at the AMS13 ground site in Fort McKay, AB, from 10 August to 5 September 2013. The PAN-GC limits of detection for PAN, PPN, and MPAN during FOSSILS were 1, 2, and 3 pptv, respectively. For the Abbotsford data set, the PAN-GC mixing ratios were compared, and agreed with those determined in parallel by thermal dissociation chemical ionization mass spectrometry (TD-CIMS). Advantages and disadvantages of the PAN measurement techniques used in this work and the utility of TD-CRDS as a PAN-GC calibration method are discussed.Item Open Access A gas chromatograph for quantification of peroxycarboxylic nitric anhydrides calibrated by thermal dissociation cavity ring-down spectroscopy(Copernicus, 2014-06-13) Tokarek, T. W.; Huo, J. A.; Odame-Ankrah, C. A.; Hammoud, D.; Taha, Y. M.; Osthoff, Hans D.