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Articles 61 - 90 of 208
Full-Text Articles in Chemistry
Mls Measurements Of Stratospheric Hydrogen Cyanide During The 2015-2016 El Niño Event, Hugh C. Pumphrey, Norbert Glatthor, Peter F. Bernath, Christopher D. Boone, James W. Hannigan, Ivan Ortega, Nathaniel J. Livesey, William G. Read
Mls Measurements Of Stratospheric Hydrogen Cyanide During The 2015-2016 El Niño Event, Hugh C. Pumphrey, Norbert Glatthor, Peter F. Bernath, Christopher D. Boone, James W. Hannigan, Ivan Ortega, Nathaniel J. Livesey, William G. Read
Chemistry & Biochemistry Faculty Publications
It is known from ground-based measurements made during the 1982-1983 and 1997-1998 El Niño events that atmospheric hydrogen cyanide (HCN) tends to be higher during such years than at other times. The Microwave Limb Sounder (MLS) on the Aura satellite has been measuring HCN mixing ratios since launch in 2004; the measurements are ongoing at the time of writing. The winter of 2015- 2016 saw the largest El Niño event since 1997-1998. We present MLS measurements of HCN in the lower stratosphere for the Aura mission to date, comparing the 2015- 2016 El Niño period to the rest of the …
Thermochemistry Of Fluorinated Aldehydes And Corresponding Radicals;Thermochemistry And Kinetics Of Diethyl Ether And Ethyl Oxirane Relative To Reactions Under Atmospheric And Combustion Conditions, Douglas Lee Purnell Jr.
Thermochemistry Of Fluorinated Aldehydes And Corresponding Radicals;Thermochemistry And Kinetics Of Diethyl Ether And Ethyl Oxirane Relative To Reactions Under Atmospheric And Combustion Conditions, Douglas Lee Purnell Jr.
Dissertations
Fundamental thermochemical properties including enthalpies (ΔH°f 298), entropies (S°(T)), heat capacities (Cp(T)), and bond dissociation energies (BDEs) for several common and complex hydrocarbon fuel species are determined using computational chemical methods. ΔH°f 298 values are calculated using isodesmic reactions with the CBS-APNO, CBS-4M, CBS-QB3, G2, G3, G4, Weizmann-1 (W1U) and M06-2X, ωB97X, B3-LYP with basis set 6-31G+ (d,p) and 6-31G++(d,p) calculation methods. Structures, moments of inertia, vibrational frequencies, and internal rotor potentials are calculated for contributions to entropies and heat capacities. Kinetic rate parameters are calculated for hydrogen abstraction and …
Collaborative Research: Refining And Testing Methods For Identifying And Quantifying Gaseous Oxidized Mercury In Air, Seth Lyman
Funded Research Records
No abstract provided.
Repeat Fuel Specific Emission Measurements On Two California Heavy-Duty Truck Fleets, Molly J. Haugen, Gary A. Bishop
Repeat Fuel Specific Emission Measurements On Two California Heavy-Duty Truck Fleets, Molly J. Haugen, Gary A. Bishop
Fuel Efficiency Automobile Test Publications
The University of Denver repeated its 2013 fuel specific gaseous and particle emission measurements on two California heavy-duty vehicle fleets. In 2015 1,457 measurements at the Port of Los Angeles and 694 measurements at the Cottonwood weigh station in northern California were collected. The Port fleet changed little since 2013, increasing the average age (+1.8 years), accompanied by an increase in particle mass (PM) by +266% (0.03 ± 0.01 to 0.11 ± 0.01 gPM/kg of fuel) and black carbon (BC) by +300% (0.02 ± 0.003 to 0.08 ± 0.01 gBC/kg of fuel). Particle number (PN) also increased (1.5 x 10 …
On-Road Remote Sensing Of Automobile Emissions In The Chicago Area: Fall 2016, Gary A. Bishop, Molly J. Haugen
On-Road Remote Sensing Of Automobile Emissions In The Chicago Area: Fall 2016, Gary A. Bishop, Molly J. Haugen
Fuel Efficiency Automobile Test Publications
No abstract provided.
United States Light And Heavy -Duty Fuel Specific On -Road No And No X Emission Factor Trends And Their Importance In Inventory Calculations (Presentation), Gary A. Bishop
Fuel Efficiency Automobile Test Publications
No abstract provided.
New And Improved Infra-Red Absorption Cross Sections And Ace-Fts Retrievals Of Carbon Tetrachloride (Ccl4), Jeremy J. Harrison, Christopher D. Boone, Peter F. Bernath
New And Improved Infra-Red Absorption Cross Sections And Ace-Fts Retrievals Of Carbon Tetrachloride (Ccl4), Jeremy J. Harrison, Christopher D. Boone, Peter F. Bernath
Chemistry & Biochemistry Faculty Publications
Carbon tetrachloride (CCl4) is one of the species regulated by the Montreal Protocol on account of its ability to deplete stratospheric ozone. As such, the inconsistency between observations of its abundance and estimated sources and sinks is an important problem requiring urgent attention (Carpenter et al., 2014) [5]. Satellite remote-sensing has a role to play, particularly limb sounders which can provide vertical profiles into the stratosphere and therefore validate stratospheric loss rates in atmospheric models. This work is in two parts. The first describes new and improved high-resolution infra-red absorption cross sections of carbon tetrachloride/dry synthetic air over …
The Use Of Stable Isotopes And Particulate Matter In The Investigation Of Local And Regional Atmospheric Chemistry, Tanya Lynn Katzman
The Use Of Stable Isotopes And Particulate Matter In The Investigation Of Local And Regional Atmospheric Chemistry, Tanya Lynn Katzman
Open Access Dissertations
The chemical composition of particulate matter (PM), a known contributor to air pollution, is highly variable, and elemental analysis reveals information about local and regional sources, as well as how air masses and climate influence PM compositions. Seasonal changes in climate, such as temperature, amount of daylight, or meteorological patterns influence source emissions (increased residential heating activities, decreased natural soil emissions) and the relative importance of certain chemical pathways in the atmosphere. Since the magnitude of these seasonal changes are highly dependent on location, each sampling site is unique and the chemical composition of PM provides valuable insight into local …
Multiple New-Particle Growth Pathways Observed At The Us Doe Southern Great Plains Field Site, Anna L. Hodshire, Michael J. Lawler, Jun Zhao, John Ortega, Coty Jen, Taina Yli-Juuti, Jared F. Brewer, Jack K. Kodros, Kelley C. Barsanti, Dave R. Hanson, Peter H. Mcmurry, James N. Smith, Jeffery R. Pierce
Multiple New-Particle Growth Pathways Observed At The Us Doe Southern Great Plains Field Site, Anna L. Hodshire, Michael J. Lawler, Jun Zhao, John Ortega, Coty Jen, Taina Yli-Juuti, Jared F. Brewer, Jack K. Kodros, Kelley C. Barsanti, Dave R. Hanson, Peter H. Mcmurry, James N. Smith, Jeffery R. Pierce
Civil and Environmental Engineering Faculty Publications and Presentations
New-particle formation (NPF) is a significant source of aerosol particles into the atmosphere. However, these particles are initially too small to have climatic importance and must grow, primarily through net uptake of low volatility species, from diameters ∼ 1 to 30–100 nm in order to potentially impact climate. There are currently uncertainties in the physical and chemical processes associated with the growth of these freshly formed particles that lead to uncertainties in aerosol-climate modeling. Four main pathways for new-particle growth have been identified: condensation of sulfuric-acid vapor (and associated bases when available), condensation of organic vapors, uptake of organic acids …
On-Road Remote Sensing Of Automobile Emissions In The Tulsa Area: Fall 2015, Gary A. Bishop, Donald H. Stedman
On-Road Remote Sensing Of Automobile Emissions In The Tulsa Area: Fall 2015, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
Measuring Real-World Emissions From The On-Road Passenger Fleet, Gary A. Bishop, Donald H. Stedman
Measuring Real-World Emissions From The On-Road Passenger Fleet, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
Donald H. Stedman 50 Years Of Air Quality Instrument Inventions And Measurements (Presentation), Gary A. Bishop, Donald H. Stedman
Donald H. Stedman 50 Years Of Air Quality Instrument Inventions And Measurements (Presentation), Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
High-Mileage Light-Duty Fleet Vehicle Emissions: Their Potentially Overlooked Importance, Gary A. Bishop, Donald H. Stedman, Daniel A. Burgard, Oscar Atkinson
High-Mileage Light-Duty Fleet Vehicle Emissions: Their Potentially Overlooked Importance, Gary A. Bishop, Donald H. Stedman, Daniel A. Burgard, Oscar Atkinson
Fuel Efficiency Automobile Test Publications
No abstract provided.
Research For The Advancement Of Green Chemistry Practice: Studies In Atmospheric And Educational Chemistry, Steven Gene Cullipher
Research For The Advancement Of Green Chemistry Practice: Studies In Atmospheric And Educational Chemistry, Steven Gene Cullipher
Graduate Doctoral Dissertations
Green chemistry is a philosophy of chemistry that emphasizes a decreasing dependence on limited non-renewable resources and an increasing focus on preventing pollution byproducts of the chemical industry. In short, it is the discipline of chemistry practiced through the lens of environmental stewardship. In an effort to advance the practice of green chemistry, three studies will be described that have ramifications for the practice. The first study examines the atmospheric oxidation of a hydrofluorinated ether, a third-generation CFC replacement compound with primarily unknown atmospheric degradation products. Determination of these products has the potential to impact decisions on refrigerant usage in …
On-Road Heavy-Duty Vehicle Emissions Monitoring System, Gary A. Bishop, Rachel Hottor-Raguindin, Donald H. Stedman, Peter Mcclintock, Ed Theobald, Jeremy D. Johnson, Doh-Won Lee, Josias Zietsman, Chandan Misra
On-Road Heavy-Duty Vehicle Emissions Monitoring System, Gary A. Bishop, Rachel Hottor-Raguindin, Donald H. Stedman, Peter Mcclintock, Ed Theobald, Jeremy D. Johnson, Doh-Won Lee, Josias Zietsman, Chandan Misra
Fuel Efficiency Automobile Test Publications
The introduction of particulate and oxides of nitrogen (NOx) after-treatment controls on heavy-duty vehicles has spurred the need for fleet emissions data to monitor their reliability and effectiveness. The University of Denver has developed a new method for rapidly measuring heavy-duty vehicles for gaseous and particulate fuel specific emissions. The method was recently used to collect 3,088 measurements at a Port of Los Angeles location and a weigh station on I-5 in northern California. The weigh station NOx emissions for 2014 models are 73% lower than 2010 models (3.8 vs. 13.9 gNOx/kg of fuel) and …
Real ‐ World Vehicle Emissions Measurements (Presentation), Gary A. Bishop
Real ‐ World Vehicle Emissions Measurements (Presentation), Gary A. Bishop
Fuel Efficiency Automobile Test Publications
No abstract provided.
On-Road Remote Sensing Of Automobile Emissions In The Chicago Area: Fall 2014, Gary A. Bishop, Donald H. Stedman
On-Road Remote Sensing Of Automobile Emissions In The Chicago Area: Fall 2014, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
Reactive Nitrogen Species Emission Trends In Three Light-/Medium-Duty United States Fleets, Gary A. Bishop, Donald H. Stedman
Reactive Nitrogen Species Emission Trends In Three Light-/Medium-Duty United States Fleets, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
Repeated, fuel specific, emission measurements in Denver (2005/2013), Los Angeles (2008/2013) and Tulsa (2005/2013) provide long-term trends in on-road reactive nitrogen emissions from three light/medium duty U.S. fleets. Reductions in oxides of nitrogen (NOx) emissions ranged from 21% in Denver (5.6 ± 1.3 to 4.4 ± 0.2 gNOx/kg of fuel) to 43% in Tulsa (4.4 ± 0.3 to 2.5 ± 0.1 gNOx/kg of fuel) since 2005 while decreases in fleet ammonia (NH3) emissions ranged from no change in Denver (0.45 ± 0.09 to 0.44 ± 0.02 gNH3/kg of fuel) since 2005 to …
Comparison Of Upper Tropospheric Carbon Monoxide From Mopitt, Ace-Fts, And Hippo-Qcls, Sara Martínez-Alonzo, Merritt N. Deeter, Helen M. Worden, John C. Gille, Louisa K. Emmons, Laura L. Pan, Mijeong Park, Gloria L. Manney, Peter F. Bernath, Chris D. Boone
Comparison Of Upper Tropospheric Carbon Monoxide From Mopitt, Ace-Fts, And Hippo-Qcls, Sara Martínez-Alonzo, Merritt N. Deeter, Helen M. Worden, John C. Gille, Louisa K. Emmons, Laura L. Pan, Mijeong Park, Gloria L. Manney, Peter F. Bernath, Chris D. Boone
Chemistry & Biochemistry Faculty Publications
Products from the Measurements Of Pollution In The Troposphere (MOPITT) instrument are regularly validated using in situ airborne measurements. However, few of these measurements reach into the upper troposphere, thus hindering MOPITT validation in that region. Here we evaluate upper tropospheric (~500 hPa to the tropopause) MOPITT CO profiles by comparing them to satellite Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) retrievals and to measurements from the High-performance Instrumented Airborne Platform for Environmental Research Pole to Pole Observations (HIPPO) Quantum Cascade Laser Spectrometer (QCLS). Direct comparison of colocated v5 MOPITT thermal infrared-only retrievals, v3.0 ACE-FTS retrievals, and HIPPO-QCLS measurements shows …
Laser Intensity And Ionic Strength Dependence Of The Aqueous Nitrate And Carbonate Ion Raman Spectra, Samuel White
Laser Intensity And Ionic Strength Dependence Of The Aqueous Nitrate And Carbonate Ion Raman Spectra, Samuel White
Mahurin Honors College Capstone Experience/Thesis Projects
The geometry (and hence vibrational modes) of aqueous nitrate ion, NO3-, is known to depend on the solution composition—concentration, counter ions, etc. If a definite relationship between the vibrational spectrum and ionic strength of the solution could be established, it could be a useful monitor of solution composition over time. This would be valuable in studying the reaction rates and mechanisms of reactions involving nitrate in an aqueous environment, such as its photolysis in snow. Previous work in our lab observed a split peak at the symmetric-stretch mode of nitrate, though this mode does not usually show …
Heavy Duty Truck Emissions (Presentation), Donald H. Stedman, Gary A. Bishop
Heavy Duty Truck Emissions (Presentation), Donald H. Stedman, Gary A. Bishop
Fuel Efficiency Automobile Test Publications
No abstract provided.
On-Road Remote Sensing Of Automobile Emissions In The Denver Area: Winter 2013, Gary A. Bishop, Donald H. Stedman
On-Road Remote Sensing Of Automobile Emissions In The Denver Area: Winter 2013, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
The Recession Of 2008 And Its Impact On Light-Duty Vehicle Emissions In Three Western Us Cities, Gary A. Bishop, Donald H. Stedman
The Recession Of 2008 And Its Impact On Light-Duty Vehicle Emissions In Three Western Us Cities, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
The global economic recession of 2008 - 2010 severely depressed light-duty vehicle sales in the United States. On-road fleets observed with a remote vehicle exhaust sensor in 2013 at three historical sampling locations in Denver, Los Angeles and Tulsa showed large reductions in the fleet fractions of 2009 model year vehicles of 40%, 38% and 35% respectively when compared to prerecession 2007 levels with the light-duty truck category suffering the largest percentage declines. The fleet fraction for these ~5 year old vehicles is normally reserved for vehicles more than twice their age. This resulted in a significant increase in the …
On-Road Remote Sensing Of Automobile Emissions In The Tulsa Area: Fall 2013, Gary A. Bishop, Donald H. Stedman
On-Road Remote Sensing Of Automobile Emissions In The Tulsa Area: Fall 2013, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
Rsd Basics (Presentation), Donald H. Stedman, Gary A. Bishop
Rsd Basics (Presentation), Donald H. Stedman, Gary A. Bishop
Fuel Efficiency Automobile Test Publications
No abstract provided.
Colorado Long Term Light-Duty Vehicle On-Road Emission Trends (Presentation), Gary A. Bishop, Donald H. Stedman
Colorado Long Term Light-Duty Vehicle On-Road Emission Trends (Presentation), Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
Spatial And Seasonal Variability Of Cloud Condensation Nuclei Number Concentrations Over The Extended North African Continent And The Mediterranean, Hesham Abdel-Monem Afify Hassan
Spatial And Seasonal Variability Of Cloud Condensation Nuclei Number Concentrations Over The Extended North African Continent And The Mediterranean, Hesham Abdel-Monem Afify Hassan
Legacy Theses & Dissertations (2009 - 2024)
The spatiotemporal variability of cloud condensation nuclei (CCN) number concentration is investigated over the extended domain of the North African continent and Mediterranean which is an essential step for better understanding of aerosol-cloud interactions and associated climate impacts over the region. The study is performed by analyzing the output for the period from 2004 to 2011 from the well-validated global chemistry and aerosol transport model GEOS-Chem-APM. The analysis shows that the dominant aerosol type for CCN number concentration is secondary particles all over the domain. Spatial analysis reveals the existence of four characteristic subdomains of variability: over the Mediterranean and …
Investigation Of Water-Molecule Complexes And Their Catalytic Effect On Important Atmospheric Reactions, Taylor Scott Cline
Investigation Of Water-Molecule Complexes And Their Catalytic Effect On Important Atmospheric Reactions, Taylor Scott Cline
Theses and Dissertations
This dissertation is a collection of works that investigates issues related to environmental chemistry. The first portion of this research explores the role of water vapor on the kinetics of important atmospheric reactions. Work is presented on the self-reaction of β-hydroxyethyl peroxy radical (β-HEP) and the catalytic increase in reaction rate by water vapor. β-HEP serves as a model system for investigating the possible role of water vapor in perturbing the kinetics and product branching ratio of atmospheric reactions of other alkyl peroxy radicals. The self-reaction rate coefficient of β-HEP was investigated between 276-296 K with 1.0 × 10^15 to …
Remote Measurements Of On-Road Emissions From Heavy-Duty Diesel Vehicles In California; Year 5, 2012, Gary A. Bishop, Donald H. Stedman
Remote Measurements Of On-Road Emissions From Heavy-Duty Diesel Vehicles In California; Year 5, 2012, Gary A. Bishop, Donald H. Stedman
Fuel Efficiency Automobile Test Publications
No abstract provided.
Yellowstone Over-Snow Vehicle Emission Tests – 2012, John D. Ray, Gary A. Bishop, Brent G. Schuchmann, Chris Frey, Gurdas Sandhu, Brandon Graver
Yellowstone Over-Snow Vehicle Emission Tests – 2012, John D. Ray, Gary A. Bishop, Brent G. Schuchmann, Chris Frey, Gurdas Sandhu, Brandon Graver
Fuel Efficiency Automobile Test Publications
No abstract provided.