A5059503542- Atmospheric chemistry and aerosols
- Atmospheric and Environmental Gas Dynamics
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- Air Quality Monitoring and Forecasting
- Air Quality and Health Impacts
- Vehicle emissions and performance
- Stellar, planetary, and galactic studies
- Hydrocarbon exploration and reservoir analysis
- Atmospheric aerosols and clouds
- Astro and Planetary Science
- Spectroscopy and Laser Applications
- Astronomical Observations and Instrumentation
- Advanced Chemical Physics Studies
- Petroleum Processing and Analysis
- Adaptive optics and wavefront sensing
- Planetary Science and Exploration
- Astrophysics and Star Formation Studies
- Maritime Transport Emissions and Efficiency
- Geochemistry and Geologic Mapping
- Photochemistry and Electron Transfer Studies
- Spectroscopy and Quantum Chemical Studies
- Calibration and Measurement Techniques
- Toxic Organic Pollutants Impact
- Water Quality Monitoring and Analysis
York University
2013-2022
University of Hawaii–West Oahu
2018
Environment and Climate Change Canada
2017
NOAA Earth System Research Laboratory
2013
University of Hawaiʻi at Mānoa
1993-2008
University of Regina
2001-2006
ECW Press (Canada)
2006
University of Maryland, College Park
2004
University of Hawaii System
2002
National Academies of Sciences, Engineering, and Medicine
1998
Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one important interactions between anthropogenic emissions related to combustion and natural from biosphere. This interaction has been recognized for more than 3 decades, during which time a large body research emerged laboratory, field, modeling studies. NO3-BVOC reactions influence air quality, climate visibility through regional global budgets reactive nitrogen (particularly nitrates), ozone,...
The uptake of gaseous glyoxal onto particulate matter has been studied in laboratory experiments under conditions relevant to the ambient atmosphere using an aerosol mass spectrometer. growth rates and reactive coefficients, γ, were derived by fitting a model particle experimental data. Organic varied from 1.05 × 10 −11 23.1 μg −1 min presence ∼5 ppb glyoxal. Uptake coefficients (γ) 8.0 −4 7.3 −3 with median γ = 2.9 , observed for (NH 4 ) 2 SO seed aerosols at 55% relative humidity....
Reactive uptake of glyoxal onto particulate matter has been studied in laboratory experiments a 2 m3 Teflon reaction chamber. Inorganic seed particles different composition were utilized, including (NH4)2SO4, (NH4)2SO4/H2SO4, NaNO3, and simulated sea salt, while the relative humidity acid concentration varied. The organic growing was measured situ with an aerosol mass spectrometer, providing particle spectra as means product identification. Aerosol physical characteristics also differential...
Atmospheric emissions of gas and particulate matter from a large ocean-going container vessel were sampled as it slowed switched high-sulfur to low-sulfur fuel transited into regulated coastal waters California. Reduction in emission factors (EFs) sulfur dioxide (SO2), matter, sulfate cloud condensation nuclei substantial (≥90%). EFs for organic decreased by 70%. Black carbon (BC) reduced 41%. When the measured reductions, brought about compliance with California quality regulation...
Reliable characterization of particles freshly emitted from the ocean surface requires a sampling method that is able to isolate those and prevent them interacting with ambient gases particles. Here we report measurements directly using newly developed in situ particle generator (Sea Sweep). The Sea Sweep was deployed alongside R/V Atlantis off coast California during May 2010. Bubbles were generated 0.75 m below stainless steel frits swept into hood/vacuum hose feed suite aerosol...
Significance Validation of volatile organic compound (VOC) emission reports, especially from large industrial facilities, is rarely attempted. Given uncertainties in their evaluation and validation will build confidence inventories. It shown that a top-down approach can provide measurement-based rates for such validation. Comparisons with reports Alberta oil sands surface mining facilities revealed significant differences VOC emissions between reports. Comparison species using currently...
Abstract. The Uintah Basin in northeastern Utah, a region of intense oil and gas extraction, experienced ozone (O3) concentrations above levels harmful to human health for multiple days during the winters 2009–2010 2010–2011. These wintertime O3 pollution episodes occur cold, stable periods when ground is snow-covered, have been linked emissions from extraction process. Winter Ozone Study (UBWOS) was field intensive early 2012, whose goal address current uncertainties chemical physical...
Abstract. Aircraft-based measurements of methane (CH4) and other air pollutants in the Athabasca Oil Sands Region (AOSR) were made during a summer intensive field campaign between 13 August 7 September 2013 support Joint Canada–Alberta Implementation Plan for Monitoring. Chemical signatures used to identify CH4 sources from tailings ponds (BTEX VOCs), open pit surface mines (NOy rBC) elevated plumes bitumen upgrading facilities (SO2 NOy). Emission rates determined five primary mining region...
The oil and gas (O&G) sector represents a large source of greenhouse (GHG) emissions globally. However, estimates O&G rely upon bottom-up approaches, are rarely evaluated through atmospheric measurements. Here, we use aircraft measurements over the Canadian sands (OS) to derive first top-down, measurement-based determination their annual CO2 intensities. results indicate that emission intensities for OS facilities 13-123% larger than those estimated using publically available data. This...
Absolute oscillator strengths in the region of carbon and fluorine K-shell excitation have been derived for ${\mathrm{CH}}_{2}$${\mathrm{CH}}_{2}$, ${\mathrm{CH}}_{2}$CHF, cis-CHFCHF, ${\mathrm{CH}}_{2}$${\mathrm{CF}}_{2}$, ${\mathrm{CHFCF}}_{2}$, ${\mathrm{CF}}_{2}$${\mathrm{CF}}_{2}$, 1,3-${\mathrm{C}}_{4}$${\mathrm{H}}_{6}$, 1,3-${\mathrm{C}}_{4}$${\mathrm{F}}_{6}$ from electron-energy-loss spectra recorded under dipole-dominated conditions. The methods used to derive absolute relative...
Abstract. Emissions factors (EFs) for gas and sub-micron particle-phase species were measured in intercepted plumes as a function of vessel speed from an underway research vessel, the NOAA ship Miller Freeman, operating medium-speed diesel engine on low-sulfur marine oil (fuel sulfur content ~0.1% by weight). The fuel use conforms to MARPOL limit within emission control areas set take effect 2015 California-specific limits 2014. For many species, EFs determined using multiple measurement...
view Abstract Citations (140) References (69) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Distance Moduli and Structure of the Magellanic Clouds from Near-Infrared Photometry Classical Cepheids Welch, Douglas L. ; McLaren, Robert A. Madore, Barry F. McAlary, Christopher W. New JHK photometry has been obtained for Cepheid variables in LMC SMC merged with existing data Laney Stobie (1986a). The total base comprises 494 observations 65 451 94 Cepheids....
view Abstract Citations (69) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere Venus. Betz, A. L. ; Johnson, M. McLaren, R. Sutton, E. C. Strong 10-micron line from (C-12)(O-16)2 upper Venus has been detected by heterodyne techniques. Observations absolute Doppler shift features indicated mean zonal less than 10 m/s near equator. No evidence was found for 100-m/s...
Abstract. Nighttime chemistry in polluted regions is dominated by the nitrate radical (NO3) including its direct reaction with natural and anthropogenic hydrocarbons, NO2 to form N2O5, subsequent reactions of N2O5 HNO3 chlorine containing photolabile species. We report nighttime measurements NO3, NO2, O3, marine boundary layer southwest Vancouver, BC during a three week study summer 2005. The concentration was calculated using well known equilibrium, NO3+NO2↔N2O5. Median overnight mixing...
Abstract. A complete understanding of the formation mechanism nitrous acid (HONO) in ambient atmosphere is complicated by a lack processes occurring when aqueous water present. We report nocturnal measurements HONO, SO2 and NO2 differential optical absorption spectroscopy over ocean surface polluted marine environment. In this environment, we observed reproducible pseudo steady states (PSS) HONO every night, that are fully formed shortly after sunset, much faster than seen urban...
Abstract. Methane emissions in Canada have both anthropogenic and natural sources. Anthropogenic are estimated to be 4.1 Tg a−1 from 2010–2015 the National Inventory Report submitted United Nation's Framework Convention on Climate Change (UNFCCC). Natural emissions, which mostly due boreal wetlands, largest methane source highly uncertain, order of ∼ 20 biosphere process models. Aircraft studies over last several years provided “snapshot” that conflict with inventory estimates. Here we use...
Abstract. The atmospheric lifetimes of pollutants determine their impacts on human health, ecosystems and climate, yet, pollutant due to dry deposition over large regions have not been determined from measurements. Here, a new methodology based aircraft observations is used the oxidized sulfur nitrogen (3-6)×103 km2 boreal forest in Canada. Dry fluxes decreased exponentially with distance Athabasca oil sands sources, located northern Alberta, resulting 2.2–26 h. Fluxes were 2–14 1–18 times...
view Abstract Citations (74) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS JHK observations of classical Cepheids. Welch, D. L. ; Wieland, F. McAlary, C. W. McGonegal, R. Madore, B. McLaren, A. Neugebauer, G. New photometry is presented for 69 galactic Full phase coverage 23 these stars used to determine the relationship between UBV and amplitudes. A procedure recovering mean magnitudes from single-phase known Cepheids outlined. These...
It is proposed that Rydberg and valence σ* conjugate orbitals have separate existences can be seen in the same spectrum if MO disentangled from manifold. Because energy of a consequence σ–σ* split resulting bond formation, spectra molecules having weak bonds should show low-lying transitions to addition bands. Inelastic electron scattering x-ray region (270–730 eV) strengths 20–50 kcal/mol regime clearly well-isolated MOs, some cases simultaneous presence virtual orbitals. The general...
view Abstract Citations (58) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Nonthermal 10 micron CO2 mission lines in the atmospheres of Mars and Venus. Johnson, M. A. ; Betz, L. McLaren, R. Sutton, E. C. Townes, H. Mechanisms are examined for excitation strong 10-micron emission seen on Line absorption near-infrared solar flux directly by or H2O with collisional transfer energy to proposed as likely mechanisms. Altitudes peak estimated be...
Abstract. Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in a rural location of southwestern Ontario during the Border Air Quality and Meteorology Study. Slant column densities (SCDs) NO2 O4 determined using standard DOAS technique. Using radiative transfer model SCDs, aerosol optical depths for clear sky conditions compared to OMI, MODIS, AERONET, local PM2.5 measurements. This information was input calculate air mass factors, which fit...
Absolute oscillator strength spectra in the C 1s (280–340 eV) and F (680–740 regions of perfluoro-n-alkanes from 2 to 6 perfluorocycloalkanes 3 have been determined inner-shell electron energy loss recorded under electric-dipole scattering conditions. The spectral features are interpreted terms spatially localized transitions terminating at orbitals predominantly σ*(C—F) σ*(C—C) character. When compared perfluoro-n-alkanes, both exhibit additional low-lying bands which assigned shifted low...