Digital Commons Network^™

Measurements Of Secondary Organic Aerosol From Oxidation Of Cycloalkenes, Terpenes, And M-Xylene Using An Aerodyne Aerosol Mass Spectrometer, Roya Bahreini, Melita D. Keywood, Nga L. Ng, Varuntida Varutbangkul, Song Gao, Richard C. Flagan, John H. Seinfeld, D. R. Worsnop, J. L. Jimenez

Chemistry and Physics Faculty Articles

The Aerodyne aerosol mass spectrometer (AMS) was used to characterize physical and chemical properties of secondary organic aerosol (SOA) formed during ozonolysis of cycloalkenes and biogenic hydrocarbons and photooxidation of m-xylene. Comparison of mass and volume distributions from the AMS and differential mobility analyzers yielded estimates of “effective” density of the SOA in the range of 0.64−1.45 g/cm³, depending on the particular system. Increased contribution of the fragment at m/z 44, CO₂⁺ ion fragment of oxygenated organics, and higher “Δ” values, based on ion series analysis of the mass spectra, in nucleation experiments …

Synthesis, Structural Studies And Desilylation Reactions Of Some N-2-(Trimethylsilyl)Ethyl-N-Nitrosocarbamates, Arpitha Thakkalapally, Vladimir Benin

Chemistry Faculty Publications

The present report describes the preparation and characterization of several N-2-(trimethylsilyl)ethyl-N-nitrosocarbamates, designed as precursors to thermally unstable secondary N-nitrosocarbamate anions via fluoride-assisted cleavage. X-ray structural studies demonstrate that the core N-nitrosocarbamate moiety has a nearly planar geometry, with an s-E orientation at the N–N bond. DFT calculations (B3LYP/6-31+G(d)) reproduce accurately the structural features of the title compounds and detailed conformational analysis at the same level of theory addresses the long-standing issue of preferred geometries for three classes of related structures: N-nitrosocarbamates, N-nitrosoureas and N-nitrosoamides. Desilylation studies demonstrate that both the …

Aerosol Properties And Chemical Apportionment Of Aerosol Optical Depth At Locations Off The U.S. East Coast In July And August 2001, Brian I. Magi, Peter V. Hobbs, Thomas W. Kirchstetter, Tihomir Novakov, Dean A. Hegg, Song Gao, Jens Redemann, Beat Schmid

Chemistry and Physics Faculty Articles

Airborne in situ measurements of vertical profiles of the aerosol light scattering coefficient, light absorption coefficient, and single scattering albedo (ω₀) are presented for locations off the East Coast of the United States in July–August 2001. The profiles were obtained in relatively clean air, dominated by airflows that had passed over Canada and the Atlantic Ocean. Comparisons of aerosol optical depths (AODs) at 550 nm derived from airborne in situ and sun-photometer measurements agree, on average, to within 0.034 ± 0.021. A frequency distribution of ω₀ measured in the atmospheric boundary layer off the coast yields …

An Investigation Into Palladium-Catalyzed Reduction Of Perchlorate In Water, Eric G. Barney

Theses and Dissertations

In this study, application of a catalytic reactor to facilitate chemical reduction of perchlorate was investigated. Palladium-coated pellets were used as the catalyst, and formic acid was used as the reductant. Reactor performance was evaluated under a variety of operating conditions (influent pH, reductant concentration, residence time). Very little perchlorate reduction was observed under any operating condition. At best, approximately 8% perchlorate reduction was observed. This small reduction efficiency is clearly not sufficient for environmental treatment applications. Perchlorate strongly adsorbed to the catalyst at low pH (3 - 3.3). At higher pH (4 - 10), little adsorption was observed. This …

Optimal Sampling Of A Chemical Hazard Area, Jennifer R. Plourde

Theses and Dissertations

This thesis proposes a methodology for optimally sampling a chemical hazard area subsequent to a chemical weapons attack. The objective is to identify the maximum number of areas that no longer require protective gear for safe operations. We model the area as an undirected graph and employ network analysis techniques to provide a methodological framework for identifying an optimal sampling sequence within a fixed time limit. We propose four models that characterize the secondary vapor concentrations: i) static and deterministic, ii) static and stochastic, iii) dynamic and deterministic, and iv) dynamic and stochastic. Comparisons of the static cases and their …

Impact Of Alteration Phase Formation And Microbial Activity On The Fate And Transport Of The Actinides And Fission Products: Alteration Phase Analysis, James Cizdziel, Klaus J. Stetzenbach, Thomas Williams, Abe Van Luik

Publications (YM)

The study of the behavior and movement of radionuclides in the environment is significant to many projects of interest to Southern Nevada, especially for the proposed Yucca Mountain Repository, as well as to the nation-wide issues of radiological releases from a variety of scenarios. Understanding and predicting the release, transport, and fate of radionuclides, particularly the actinide elements, in the Mojave/Great Basin geology is an extremely challenging, multi-faceted problem. In support of the national program to deepen our understanding of the behavior of radionuclides in the environment and to better predict the performance of a geological repository at Yucca Mountain, …

The Determination Of Environmentally Important Metals In Marine Sediments, Linda Tyrrell

Masters

Surface sediment samples were collected at sites within the Rockall Through at water depth ranges from 700 – 2774 metres. The study area was predefined by the availability of samples. Samples were collected by the British Geological Survey during their gravity core survey undertaken in 1998. Methods were optimised and validated for lead, cadmium, chromium, copper, nickel, zinc, lithium and aluminium using atomic absorption spectroscopy following total digestion, and for mercury, using cold vapour atomic fluorescence spectroscopy following partial digestion. The measured metal concentration were normalised to Li to compensate for the influence of natural variability in the concentration of …

Vehicle Remote Sensing For Nitrogen Dioxide (Presentation), Thomas R. Dalton, Gary A. Bishop, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

On-Road Emissions In Asia Measured By Remote Sensing (Presentation), Donald H. Stedman, Gary A. Bishop

Fuel Efficiency Automobile Test Publications

No abstract provided.

Effect Of Humic Substance Photodegradation On Bacterial Growth And Respiration In Lake Water, Alexandre M. Anesio, William Granéli, George R. Aiken, David J. Kieber, Kenneth Mopper

Chemistry & Biochemistry Faculty Publications

This study addresses how humic substance (HS) chemical composition and photoreactivity affect bacterial growth, respiration, and growth efficiency (BGE) in lake water. Aqueous solutions of HSs from diverse aquatic environments representing different dissolved organic matter sources (autochthonous and allochthonous) were exposed to artificial solar UV radiation. These solutions were added to lake water passed through a 0.7-μm pore-size filter (containing grazer-free lake bacteria) followed by dark incubation for 5, 43, and 65 h. For the 5-h incubation, several irradiated HSs inhibited bacterial carbon production (BCP) and this inhibition was highly correlated with H₂O₂ photoproduction. The H_{2 …}

On-Road Remote Sensing Of Automobile Emissions In The Omaha Area: Year 2, September 2004, Gary A. Bishop, Daniel A. Burgard, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

Portable Emission Measurements Of Snowcoaches And Snowmobiles In Yellowstone National Park (Presentation), John D. Ray, Gary A. Bishop

Fuel Efficiency Automobile Test Publications

No abstract provided.

Determination Of Trifluoroacetate By Ion Chromatography For Snow And Ice Analysis, Jon Hanson

The Journal of Undergraduate Research

Trifluoroacetic acid (TEA) is a product of the atmospheric degradation of hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs). HCFCs and HFCs are widely used substitutes for chlorofluorocarbons (CFCs) that have been found to contribute to the loss of stratospheric ozone. Deposits of TEA with precipitation (rain and snow) can lead to its presence and accumulation in the aquatic and cryosphere environments, with unknown long-term environmental consequences. Investigation on TEA impact and its fate in the environment requires sensitive, accurate, and fast analytical methods. The determination of trace concentrations of TEA using the technique of ion chromatography (IC) is investigated in this study, …

2005- 2008 Unlv Mcnair Journal, Valerie Avery, Shana Bachus, Karmen K. Boehlke, Andrea Flores, Alden Kelly, Erick Lopez, Carol Preussler, Heather Shay, Ava Bookatz, Shaun Elsasser, Veronica Hicks, Shaida A. Jetha, Anthony Quinn, Thurithabhani Seneviratne, Teddy Boado Sim Jr., Liza Ward, Amris Henry-Rodgers, Jacquelynn Kaaa-Logan, Jason Orozco, Juan C. Plata, Bonnie Bartlett, Kathleen Bell, Vacheral M. Carter, Nydia Diaz, Kimberly Hackstock, Julio A. Luna, Charles Mao, Sandra Ramos, Precious Rideout, Benjamin Lee Watrous, Chet R. Whitley

McNair Journal

Journal articles based on research conducted by undergraduate students in the McNair Scholars Program

Table of Contents

Biography of Dr. Ronald E. McNair

Statements:

Dr. Neal J. Smatresk, UNLV President

Dr. Juanita P. Fain, Vice President of Student Affairs

Dr. William W. Sullivan, Associate Vice President for Retention and Outreach

Mr. Keith Rogers, Deputy Executive Director of the Center for Academic Enrichment and Outreach

McNair Scholars Institute Staff

Oceanic Uptake And The Global Atmospheric Acetone Budget, Christa Marandino, Warren J. De Bruyn, Scott Miller, M. J. Prather, Eric S. Saltzman

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

In this study, direct measurements of the air/ sea flux of acetone were made over the North Pacific Ocean. The results demonstrate that the net flux of acetone is into, rather than out of the oceans. The extrapolated global ocean uptake of 48 Tg yr(-1) requires a major revision of the atmospheric acetone budget. This result is consistent with a recent reevaluation of acetone photodissociation quantum yields.