Download or read book Instrument Development and Measurements of the Atmospheric Pollutants Sulfur Dioxide Nitrate Radical and Nitrous Acid by Cavity Ring down Spectroscopy and Cavity Enhanced Absorption Spectroscopy written by David Salvador Medina and published by . This book was released on 2011 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sulfur dioxide (SO[subscript 2]), nitrate radical (NO[subscript 3]), and nitrous acid (HONO) play important roles in the atmosphere. SO[subscript 2] is associated with the combustion of fossil fuels and contributes to acidification of the ecosystem, particulate sulfate formation and SO[subscript 2] is an EPA regulated species. NO[subscript 3] is the major oxidation species at night often reacting with biogenic volatile organic hydrocarbons emitted during the nighttime air, which lead to peroxyl radical and nitric acid formation. HONO is a major source of hydroxyl radical (OH) in the early morning. All of these three pollutants exhibit strong absorptions in the UV and visible region and their absorption bands are exploited for measurements using the ultrasensitive absorption spectroscopy techniques, cavity ring-down spectroscopy (CRDS) and broadband cavity enhanced absorption spectroscopy (BBCEAS). SO[subscript 2] is measured by CRDS near 308 nm in the UV region with a limit of detection of 3.5 ppb/10 seconds (S/N = 2) and ambient measurements are attempted. Instruments based on light emitting diode (LED) based BBCEAS are developed for measurements of NO[subscript 3] and HONO. NO[subscript 3] is monitored using the 662 nm absorption feature with a limit of detection of 10 ppt/2 minutes (1[Alpha]) and the technique is demonstrated by sampling from an environmental chamber. HONO is measured in the UV region using the 368 nm absorption with a limit of detection of 10 ppb/2 minutes (1[Alpha]).
Download or read book Nighttime Measurements of Dinitrogen Pentoxide and the Nitrate Radical Via Cavity Ring down Spectroscopy written by Katie C. Perkins and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of effective pollution control strategies for urban areas requires accurate predictive models. The ability of models to correctly characterize the atmospheric chemistry, meteorology, and deposition rely on accurate data measurements, both as input and verification of output. Therefore, the measurement techniques must be sensitive, accurate, and capable of resolving the spatial and temporal variations of key chemical species. The application of a sensitive in situ optical absorption technique, known as cavity ring-down spectroscopy, will be introduced for simultaneously measuring the nitrate radical and dinitrogen pentoxide. The cavity ring-down spectrometer was initially designed and constructed based on the experiments by Steven Brown and Akkihebal Ravishankara at the National Oceanic and Atmospheric Administration. The instrument design has since undergone many revisions before attaining the current instrumentation system. Laboratory observations provide verification of accurate N2O5 and NO3 detection with measurements of the nitrate radical absorption spectrum centered at 662 nm, effective chemical zeroing with nitric oxide, and efficient thermal decomposition of N2O5. Field observations at a local park provided further confirmation of the instruments capability in measuring N2O5 and NO3. However, detection limits were too high to detect ambient NO3. Effective and frequent zeroing can easily improve upon the sensitivity of the instrument. Determination of the source of the polluted air masses detected during these studies was unknown since the typical southerly winds from Houston were not observed. Since deployment in the field, instrumentation modifications and laboratory measurements are underway for preparation of the SOOT campaign in Houston, Texas starting April 15, 2009. Current modifications include automation of the titration with a solenoid valve and an automated filter changer. Wall losses and filter transmission for NO3 and N2O5 will be determined through laboratory measurements in coincidence with and ion-drift chemical ionization mass spectrometer prior to the SOOT project. Potential modifications to improve upon the instrument are suggested for future endeavors.
Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2726 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Application of Cavity Ring down Spectroscopy to Atmospheric and Physical Chemistry written by James McChesney Hargrove and published by . This book was released on 2007 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavity Ringdown Spectroscopy of the Nitrate and Peroxy Radicals written by Kana Takematsu and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development and Deployment of a Broadband Cavity Enhanced Absorption Spectroscopy Instrument for Airborne Measurements of Trace Gases written by Oliver John Kennedy and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavity Ringdown Spectroscopy in Nitrogen oxygen Mixtures in the Presence of Alpha Radiation written by Sidney John Gautrau and published by . This book was released on 2016 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research was part of an effort to experimentally validate computational models under development for radiation-induced atmospheric effects. Cavity Ringdown Spectroscopy (CRDS) was used to measure the concentration of chemical products generated as a result of radiation interactions in a controlled atmosphere. Experiments were conducted in a vacuum chamber interfaced with a gas introduction system that controlled the initial atmospheric composition. A quadrupole mass spectrometer and tunable dye laser were integrated to confirm initial atmospheric composition, and provide wavelength flexibility for detecting a variety of chemical products generated by radiation interactions. CRDS measurements were made for ozone production resulting from alpha radiation interactions in nitrogen-oxygen mixtures while the Polonium 210 alpha sources were cycled between being shielded and exposed. The beginning of this thesis will provide brief reviews of ionizing radiation and ozone formation, along with explanations of Cavity Enhanced Absorption Spectroscopy and CRDS. This is followed by a description of the existing vacuum and optical system, as well as the modifications required to integrate the mass spectrometer and dye laser. Another chapter details the modifications made to the existing software, as well as new software developed for the mass spectrometer and dye laser. Finally, results are presented showing the rapid production of ozone following exposure of the alpha radiation to the controlled atmosphere. Results also show ozone concentrations rapidly decreasing when the source was re-shielded, but when the source was re-exposed, the ozone concentration started at the previous concentration and continued to increase. This indicates the presence of a possible ozone catalyst. --Page ii.
Download or read book Spectroscopic Instrumentation for Atmospheric Pollution Studies written by Martin Stuart Tunstall and published by . This book was released on 1984 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the design and construction of a scanned- -diode-array, ultraviolet absorption spectrophotometer for the study of atmospheric pollutants . m e instrument exploits the recent developments of linear scanned silicon arrays to enhance the performance of mask correlation spectrometers for monitoring atmospheric pollutants, such as sulphur dioxide and nitrogen dioxide through their ultraviolet and visible absorption spectra. This thesis surveys the current status of mask correlation spectroscopy and describes some of its applications , with particular reference to vertical burden measurements from isolated points sources, such as generating stations. The initial development of the ....
Download or read book Cavity Ringdown Spectroscopy Studies of Atmospheric Reactions written by Andrew Keeler Mollner and published by . This book was released on 2007 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavity Ringdown Spectroscopy of Atmospherically Important Radicals written by Andrei Deev and published by . This book was released on 2005 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cavity Ring Down Spectrometer for the Absorption Measurements of Molecular Ions written by and published by . This book was released on 2002 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this project was to develop an ion spectrometer capable of making absorption measurements on ions using cavity ring-down spectroscopy (CRDS). As part of our continuing goal of detecting ion products from ion-molecule reactions, we have successfully used CRDS to measure the vibronic absorption spectra of various small ions and radicals generated by a pulsed discharge nozzle. These spectra give information about the number densities and temperatures of the ions and radicals. Currently, our setup consists of a pulsed discharge nozzle that produces high concentrations of radicals and ions arranged perpendicular to the optical cavity made from two highly reflective mirrors. To date, we have obtained the absorption spectrum of N2(+) and CN as well as several atomic species.
Download or read book Applications of Cavity Ring down Spectroscopy in Environmental Physics written by Yangzhuoran Liu and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of a Cavity Ring down Spectrometer and Subsequent Studies of Nitrogen Dioxide written by Rebecca Cydney Batiste and published by . This book was released on 2005 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of a Near infrared Optical Feedback Cavity Enhanced Absorption Spectrometer OF CEAS for Atmospheric Water Vapor Isotope Ratio 18O 16O 17O 16O and 2H 1H Measurements written by Rosario Quirino Iannone and published by . This book was released on 2009 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Environmental Chamber Study of Atmospheric Chemistry and Secondary Organic Aerosol Formation Using Cavity Enhanced Absorption Spectroscopy written by Yingdi Liu and published by . This book was released on 2011 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is only a part of my research work. For more information about my other work, including cavity ring down spectroscopy studies for peroxy radical, aerosol optical extinction, transparent thin and time of flight mass spectrometry studies for the initial steps of ozone and alkenes reaactions, please refer to my PhD thesis in Chemistry department, UC-Riverside.
Download or read book The Development of Cavity Ringdown Spectroscopy as a Sensitive Continuous Emission Monitor for Metals written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this study is to evaluate cavity ringdown spectroscopy (CRDS) as an ultra-sensitive technique for trace analysis of metals. Potential applications of CRDS meeting the Department of Energy needs include: Mercury Continuous Emission Monitor Multi-Metal Emissions Monitor Radionuclide Detector and Monitor CRDS is based upon the measurement of the rate of light absorption in a closed optical cavity. A laser pulse is injected into a stable optical cavity through one of the cavity mirrors. This light pulse is trapped between the mirror surfaces and decays exponentially over time at a rate determined by the round trip losses within the cavity. When used for trace analysis, the primary loss mechanisms governing the decay time are mirror reflectivity losses, atomic absorption from the sample, and Rayleigh scattering from air in the cavity. The decay time is given by t= d c 1- R ()+ als + bd (1) where d is the cavity length, R is the reflectivity of the cavity mirrors, a is the familiar Beer's Law absorption coefficient of a sample in the cavity, ls is the length of the optical path through the sample (i.e., approximately the graphite furnace length), b is the wavelength-dependent Rayleigh scattering attenuation coefficient, and c is the speed of light. Thus, variations in a caused by changes in the sample concentration are reflected in the ringdown time. As the sample concentration increases (i.e., a increases), the ringdown time decreases yielding an absolute measurement for a. With the use of suitable mirrors, it is possible to achieve thousands of passes through the sample resulting in a significant increase in sensitivity. An additional benefit is that it is not subject to collisional quenching, the branching of fluorescence emission into multiple transitions, and the ability to detect only a fraction of the fluorescence photons that occur in laser-excited atomic fluorescence (LEAFS). One other advantage of the ringdown technique is the ability to use pulsed UV tunable lasers for atomic absorption spectroscopy.
Download or read book The Development of Cavity Ringdown Spectroscopy as a Toxic Metal Continuous Emission Monitor written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Innovative program to explore the viability of using Cavity Ringdown Spectroscopy (CRDS) for trace analysis and monitoring of remediation processes for hazardous and radioactive wastes. Cavity ringdown spectroscopy is a measurement of the rate of absorption of a sample within a closed optical cavity rather than the standard measurement of the avsorved signal strength over a given sample path. It is a technique capable of providing ultra-sensitive absorption measurements in hostile environments using commercially available easy-to-use pulsed lasers. The inherent high sensitivity stems from both the long effective sample pathlengths possible and the relaxed constraints on the accuracy of the measurement of the cavity decay time.
