Chemistry Commons^™

Spectroscopy Of Atmospheres, Randika Dodangodage

Physics Theses & Dissertations

Spectroscopic methods are used to study planetary and stellar atmospheres. The information obtained from spectroscopic studies provides insight into atmospheric compositions and dynamics, which can be used to model and characterize atmospheres and climates. Laboratory-recorded absorption cross-sections are needed to interpret the recorded spectra of planets and stars. High resolution ethane, neopentane, propene, and n-butane spectra have been recorded, and absorption cross-sections have been provided for different temperatures and total pressures with different broadening gases, including hydrogen, helium, and nitrogen. The Atmospheric Chemistry Experiment (ACE) satellite orbits Earth and records spectra through solar occultation limb observations. HOCl is a chlorine …

Lipid Biomarkers Of Bering And Chukchi Sea Euphausiids And Their Application To Diet History, Rachel L. Pleuthner

OES Theses and Dissertations

In the eastern Bering Sea, Thysanoessa raschii are the most abundant krill species and a keystone trophic member that serve as both an important grazer and link to upper level consumers. In this system krill experience large annual variation in food resources, especially during ice advance and retreat; multiple lipid classes are used to temper the effects of those fluctuations, as well as to fuel reproduction and growth. Two shipboard feeding experiments that occurred during late spring and early summer of 2010, respectively, monitored the lipid retention in adult T. raschii and examined the fluctuation of specific lipid biomarkers under …

Advances In Amino Acid Analysis For Marine Related Matrices And Its Application To Coastal Shelf Settings In The Canadian Arctic, Rachel M. Mcmahon

OES Theses and Dissertations

Amino acids comprise up to 50% of organic matter in cellular material and are a major fraction of oceanic organic carbon. Amino acids are also considered highly labile during organic matter recycling, making them useful proxies for organic carbon cycling. Nevertheless, analysis of individual amino acids has been burdened by lengthy derivatization and complex analysis since the 1950s. In this thesis, I describe the modification of advanced analytical techniques, developed in the biomedical field, for analysis of marine matrices which allow the determination of at least 40 amino acids without the need for lengthy sample preparation and derivatization, twice the …

Biogeochemical Cycling Of Selenium In The Arctic Ocean, Kyle M. Mcquiggan

OES Theses and Dissertations

Changes in the global climate may have a pronounced effect on the biogeochemical cycling of trace elements like selenium (Se) in the Arctic Ocean. This study described the first quantitative examination of the biogeochemical cycle of selenium in the Amerasian Basin, providing the baseline from which future changes can be identified. Aerosol, dissolved and particulate water samples were collected for Se determinations during the U.S. GEOTRACES GN01 Arctic expedition that sampled the two parts of the Amerasian Basin in 2015: The Makarov Basin on the way to the North Pole and the Canada Basin on the return trip to Dutch …

Selenium Distribution And Cycling In The Eastern Equatorial Pacific Ocean, Zoe Wambaugh

OES Theses and Dissertations

Oxygen minimum zones in oceanic waters have become increasingly important to the marine environment and society. Low oxygen waters affect not only the distribution and abundance of marine organisms, but also impact the solubility and transport of trace elements that are of biological importance, with the chemical speciation and solubility depending on the actual redox poise of the waters. One redox sensitive trace element of interest is selenium, which can be both toxic and essential for organisms, depending on its chemical speciation. In 2013, the US GEOTRACES program completed the GP16 transect from Peru to Tahiti, going through the oxygen …

Observations Of Greenhouse Gas Isotopologues With Ace-Fts And Waccm, Eric Michael Buzan

Chemistry & Biochemistry Theses & Dissertations

Increases in greenhouse gas concentrations in the atmosphere are the major driver of climate change. Quantifying the sources and sinks of these gases is a major focus of research. Measuring isotopologues, or molecules that differ in isotopic composition, is one useful way of constraining the budget of a molecule as they are highly sensitive to different sources and sinks. However, measurements above the surface have been restricted to a few locations and have only reached the lower stratosphere. Satellite-based remote sensing can achieve nearly global measurement coverage, but so far no satellites have measured isotopologues.

Presented here are measurements of …

High Resolution Spectra Of Carbon Monoxide, Propane And Ammonia For Atmospheric Remote Sensing, Christopher Andrew Beale

OES Theses and Dissertations

Spectroscopy is a critical tool for analyzing atmospheric data. Identification of atmospheric parameters such as temperature, pressure and the existence and concentrations of constituent gases via remote sensing techniques are only possible with spectroscopic data. These form the basis of model atmospheres which may be compared to observations to determine such parameters. To this end, this dissertation explores the spectroscopy of three molecules: ammonia, propane and carbon monoxide.

Infrared spectra have been recorded for ammonia in the region 2400-9000 cm^-1. These spectra were recorded at elevated temperatures (from 293-973 K) using a Fourier Transform Spectrometer (FTS). Comparison between …

The Marine Cyanate Cycle, Brittany Widner

OES Theses and Dissertations

Cyanate (OCN-) is a reduced nitrogen compound with the potential to serve as a nitrogen and carbon source for marine microbes. Evidence from genomes and culture studies indicated that several marine cyanobacterial groups, including representatives of the globally important genera Synechococcus and Prochlorococcus, might be capable of cyanate assimilation. However, prior to this study, the distribution, bioavailability, and production pathways of cyanate were unknown in natural systems due to the absence of a sensitive cyanate assay; and the ability of organisms to assimilate cyanate on relevant timescales was unknown because we lacked a suitable tracer for measuring uptake. I developed …

Source-Specific Molecular Signatures For Light-Absorbing Organic Aerosols, Amanda Susan Willoughby

Chemistry & Biochemistry Theses & Dissertations

Organic aerosols (OA) are universally regarded as an important component of the atmosphere based on quantitative significance as well as the far-reaching impact they have on global climate forcing and human health. Despite the acknowledged importance, OA amounts and impacts remain the largest uncertainties regarding radiative forcing estimates. Incomplete chemical characterization of aerosol organic matter (OM) and a lack of concrete source apportionment is a major source of this uncertainty. The primary focus of this study is to provide much needed molecular details regarding ambient OA from key emission sources, and establish links between molecular and optical properties.

Complete chemical …

Molecular Characterization And Photochemical Transformation Of Dissolved Organic Matter From Land To Ocean, Hongmei Chen

Chemistry & Biochemistry Theses & Dissertations

Molecular characterization and photochemical transformation of dissolved organic matter (DOM) in both rivers and the ocean is the main research focus of this dissertation. Chemical characterization of DOM is hampered by the limited application of advanced techniques to desalt, concentrate, isolate and then molecularly characterize DOM. An affordable, commercially available mini-electrodialysis (mini-ED) system has been evaluated and recommended for the efficient desalting of small volume samples of seawater prior to analysis by electrospray Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR-MS).

A high-recovery technique of DOM isolation – reverse osmosis coupled with electrodialysis (RO/ED) – was used to isolate …

Spectroscopic Characterization Of Dissolved Organic Matter: Insights Into Composition, Photochemical Transformation And Carbon Cycling, John Robert Helms

Chemistry & Biochemistry Theses & Dissertations

This dissertation explores processes affecting the composition of dissolved organic matter (DOM) and how DOM composition changes in sunlit surface waters and in the dark interior ocean. Simulated solar irradiations were used to investigate the impact of photochemistry on terrestrial waters and deep ocean DOM. The photochemically mediated processes observed in Dismal Swamp samples included (i) light induced flocculation of up to 12% of the organic matter and 84% of the dissolved iron originally present; (ii) 74-88% mineralization of dissolved organic carbon (DOC) and 95-99% bleaching of chromophoric DOM (CDOM) during 110 days of irradiation; and (iii) nearly complete loss …

Oxygen Isotopes As A Tracer Of Dom Processes In River-Estuary Systems, Joy Ashley Matthews

OES Theses and Dissertations

In the biogeochemical study of dissolved organic matter (DOM) in natural waters, stable isotopes are used to provide insight into both the sources of DOM and the processes affecting its alteration. Through the research presented here, oxygen isotopes are incorporated into the study of DOM through the adaptation of a pyrolysis elemental analysis isotope ratio mass spectrometer method, and sample preparation using two-stage ultrafiltration.

The application of oxygen isotopes to the study of DOM is demonstrated in two studies. First, natural abundance of δ¹⁸O in DOM is explored in the Delaware estuary. Using a two end-member mixing model, …

Export Of Terrestrial Dissolved Organic Matter Along A River To Ocean Transect Of The Lower Chesapeake Bay Investigated By Advanced Analytical Techniques, Rachel Leigh Sleighter

Chemistry & Biochemistry Theses & Dissertations

Ultrahigh resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) has proved essential for the complete separation of the thousands of peaks present in natural organic matter (NOM), a complex assemblage of organic molecules present in water, soils, and sediments. An improved understanding of its composition is crucial to understand how pollutants interact with NOM and how NOM cycles through global carbon cycles.

Optimizing the acquisition and handling of the FTICR mass spectra is the first step to obtaining high quality data. A simple method to internally calibrate the peaks in the complex spectra, using naturally present fatty …

Measurement Of Proton Transfer Reaction Rates In A Microwave Cavity Discharge Flowing Afterglow, George M. Brooke Iv

Physics Theses & Dissertations

The reaction rate coefficients between the hydronium ion and the molecules ethene (C₂H₄), propene (C₃H₆), 1-butene (C₄H₈) and hydrogen sulfide (H₂S) were measured at 296 K. The measured reaction rates were compared to collision rates calculated using average dipole orientation (ADO) theory. Reaction efficiency depends primarily upon the proton affinity of the molecules. All the measurements were obtained using the newly developed microwave cavity discharge flowing afterglow (MCD-FA) apparatus. This device uses an Asmussen-type microwave cavity discharge ion source that is …

Copper Complexation And Speciation In The Western South And Equatorial Atlantic Ocean, John A. Consolvo

Chemistry & Biochemistry Theses & Dissertations

Presented here are the first data on copper complexation and speciation in the South Atlantic Ocean. Samples were collected at six vertical profile stations and along the surface (1m) transect during the 1996 IOC Baseline Contaminant Survey. Copper complexation measurements were made for the surface transect (1m) samples and three of the six vertical profile stations (1m - ~500m) using differential pulse anodic stripping voltammetry (DPASV) with a thin mercury film, rotating glassy carbon disk electrode (TMFRGCDE).

A strong organic copper complexing ligand (L₁; log K' _cuL1/cu2+ > 11. 8 ± 0 .4) was detected in 57% of all …

A Diffuse Reflectance Infrared Fourier Transform Spectroscopic Investigation Of The Oxidation Of Co On Platinum/Tin(Iv) Oxide-Based Catalysts, Julie Christi Stiltner Patrick

Chemistry & Biochemistry Theses & Dissertations

Platinum/tin(IV) oxide-based catalysts have been developed for the oxidation of carbon monoxide at 55 °C and 1 atmosphere pressure. A diffuse reflectance infrared fourier transform spectroscopic (DRIFTS) investigation of this oxidation has been performed. Four catalyst samples have been subjected to a 5% carbon monoxide pretreatment at 125 °C, helium exposure at 55 °C, bottled air (20% oxygen) exposure at 55 °c, and exposure to a 2:1 stoichiometric mixture of carbon monoxide and oxygen at 55 °C. During the course of these exposures, evidence for the development of two different surface carbon monoxide configurations has been found: one that is …

Identification And Quantitation Of Volatile Amines In Chesapeake Bay Sediments, Neeraja Y. Krishna

Chemistry & Biochemistry Theses & Dissertations

Sediments from different parts of the Chesapeake Bay were analyzed to determine the presence of volatile amines. A HF-HCl extraction method was used to extract both exchangeable and fixed amines from the sediments and a purge-and-trap technique was used to concentrate the amines. Following derivatization with heptafluorobutyric anhydride (HFBA), the HFBA-amines were analyzed by gas chromatography with electron capture detection and with mass spectrometric detection. One primary amine, i-amylamine with a concentration ranging from 0. 78 nmoles/g dry weight to < 0.05 nmoles/g dry weight was found in a total of twenty seven samples collected on three different dates in 1993. Another primary amine, 2-methylbutylamine with a concentration ranging from 0.18 nmoles/g dry weight to < 0.05 nmoles/g dry weight was found in a total of twenty three samples collected on three different dates in 1993. A secondary amine, diethylamine was detected but could not be quantified in a total of seven samples collected in September 1993. The concentrations of these amines varied with location in the Bay, depth in the sediment, and time of year the sediments were collected. The origin of i-amylamine and 2-methylbutylamine might be from the biological decarboxylation of amino acids leucine and isoleucine, respectively. The origin of diethylamine is unknown.

Optimization Of The Tungstic Acid Denuder Technique For The Measurement Of Atmospheric Ammonia, Patricia Diane Roberts

Chemistry & Biochemistry Theses & Dissertations

Measurement of - atmospheric ammonia with the tungstic acid denuder technique is discussed. Characterization of denuder tubes for manual sampling in terms of, repeatability, reliability and the development of ammonia blank signals was determined. Field testing of the manual sampling apparatus was performed at ground test sites and in a biomass burn smoke plume. Ammonia emissions from biomass burning are discussed.

The Temporal And Spatial Distribution Of Hydrocarbons In Atmospheric Deposition From Stations Surrounding Lower Chesapeake Bay, David Benjamin Webber

OES Theses and Dissertations

Hydrocarbon concentrations were determined in bulk, wet, and dry deposition samples from urban and non-urban locations surrounding lower Chesapeake Bay. Mean hydrocarbon concentrations in bulk deposition samples were over three times greater at the urban station indicating a localized source. The major hydrocarbons present were n-alkanes, polycyclic aromatic hydrocarbons (PAH), and the unresolved complex mixture (UCM). The PAH and the UCM were an indication of significant anthropogenic inputs while the odd/even distribution of the n-alkanes was an indication of biogenic sources. These findings indicated seasonal trends of highest biogenic hydrocarbon inputs in the spring and summer months and highest anthropogenic …