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Browsing Science Research & Publications by Department "Analytical"

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    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.
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    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.
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    Ubiquity of ClNO2 in the urban boundary layer of Calgary, AB, Canada
    (NRC Research Press (Canadian Science Publishing), 2015-12-17) Mielke, Levi H.; Furgeson, Amanda; Odame-Ankrah, Charles A.; Osthoff, Hans D.
    The role of nitryl chloride (ClNO2) as a nocturnal nitrogen oxide reservoir species and chlorine atom precursor is well established for polluted coastal areas, but its role at mid-continental locations is less clear. In this manuscript, intermittent measurements over the course of several seasons of ClNO2 mixing ratios by iodide ion chemical ionization mass spectrometry (CIMS) in Calgary, AB, Canada, are presented. Mixing ratios were highly variable between nights and seasons and depended on the abundances of precursors and meteorological conditions. The lowest ClNO2 mixing ratios (nocturnal maximum of 30 parts-per-trillion by volume, pptv) were observed in the summer, rationalized by losses of the nitrate radical (NO3) that were more efficient than in the other months. Higher ClNO2 mixing ratios (up to 330 pptv) were observed in the winter and spring months, but varied between nights. In the fall, ClNO2 mixing ratios increased from night to night following the application of salt to roads. The ClNO2 yield relative to the amount of NO3 produced from oxidation of NO2 by O3 ranged from 0.1% to 4.5% (10th and 90th percentiles; median 1.0%). The ClNO2 yield relative to consumed N2O5 consumed by heterogeneous reactions was estimated using a time-integrated box model and ranged from 0.5% to 12.1% (10th and 90th percentiles; median 3.4%). The ubiquity of ClNO2 implies that the Cl atom needs to be considered as an oxidant in high-latitude urban environments in winter.