Download or read book The Production and Characterisation of High Purity Ozone and Experimental and Modelling Studies of Anomalous Oxygen Isotope Effects in the Formation of Carbon Dioxide from Irradiated Mixtures of Carbon Monoxide and Ozone Or Oxygen written by Daniela Simone and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ozone formation reaction O+O2+M→O3+M is a unique example of a chemical reaction that leads to an anomalous isotopic composition of the products, most likely due to symmetry - breaking effects. So far, results on other chemical systems that might show similar effects are spurious, even though such claims concerning reactions other than the formation of ozone have been made repeatedly.This applies in particular to the spin forbidden O+CO+M→CO2+M reaction, where two studies report a mass-independent fractionation of about 8%. Nevertheless, the presence of ozone in these experiments raises questions as to the validity of this assertion. We thus make a new attempt to study the O+CO+M reaction in the photoreactor at CCAR (University of Copenhagen) where reagents and contaminants are monitored on-line by FTIR spectroscopy. This study combined with the analysis of the spectral distribution of the employed lamps and isotope kinetic modeling lead to a complete re-interpretation of previous experiments. We conclude that available measurements are more compatible with the hypothesis that there is no mass-independent isotope fractionation in the O+CO reaction. We propose that all observations can be completely explained by an isotope transfer from ozone, involving photolytic production of O(1D) that in turn leads to OH radicals, which then rapidly form CO2 from reaction with CO. We also present a method to produce pure ozone samples and derive an upper limit on nitrogen oxide contaminations based on mass spectrometer measurements. These values will serve as benchmarks values for future studies of ozone absorption cross sections in the IR and UV.
Download or read book The Non mass dependent Isotopic Composition of Ozone and Its Photochemical Transfer to Stratospheric CO2 written by Aaron Andrew Wiegel and published by . This book was released on 2013 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atypically large and non-mass-dependent kinetic isotope effects (KIEs) in the three-body ozone formation reaction, O(3P) + O2 2!O3* + M 2!O3 + M*, lead to a non-mass-dependent oxygen isotopic composition for O3 observed in both the laboratory and the atmosphere. Theoretical work has suggested that a dynamically-driven, quantum symmetry isotope effect in the lifetime of the excited ozone complex O3* or its collisional stabilization is responsible, although the underlying chemical physics has remained mysterious. Stratospheric CO2 also has a non-mass-dependent oxygen isotopic composition that is thought to be transferred from ozone by photolysis to form O(1D) followed by the O(1D) + CO2 isotope exchange reaction. However, the non-mass-dependent isotopic compositions of CO2 measured either in UV photochemistry experiments or in stratospheric air samples could not easily be explained by isotope effects in ozone formation, leading some to claim that additional anomalous isotope effects must exist in ozone photolysis or in the O(1D) + CO2 isotope exchange reaction. In the research results presented here, I detail several significant advances in the understanding of the non-mass-dependent isotopic composition of ozone and its transfer to stratospheric CO2. I made these advances through new measurements and kinetics modeling of the isotopic composition of O3 and CO2 in photochemistry experiments in which mixtures of O2, CO2, and other bath gases were irradiated with UV light from a mercury lamp as well as comparisons of these results with the latitude, altitude, and seasonal dependence of the isotopic composition of stratospheric CO2. For application to the non-mass-dependent isotopic composition of stratospheric CO2, I show using a kinetics model that the non-mass-dependent isotope effects in ozone formation alone can quantitatively account for the non-mass-dependent isotopic composition of CO2 in laboratory measurements of UV-irradiated mixtures of O2 and CO2 at atmospheric mixing ratios. I then used the kinetics model to provide a conceptual framework for understanding the significant differences in the non-mass-dependent isotopic composition of CO2 between the laboratory experiments and the stratosphere and between different regions of the stratosphere that I discovered in the atmospheric measurements. Based on model sensitivities to the temperature dependence of the ozone KIEs and mass-dependent isotope effects in ozone photolysis, differences in temperature and in the relative rate of ozone photolysis are found to be the likely sources of the differences in the non-mass-dependent isotopic composition of CO2 between the laboratory and the stratosphere and between different regions of the stratosphere. Having accounted for the non-mass-dependent isotopic composition of CO2 at an atmospheric O2/CO2 mixing ratio, I performed additional laboratory measurements of the non-mass-dependent isotopic composition of CO2 as a function of the O2/CO2 mixing ratio to explore the dramatic decrease in the non-mass-dependent 17O and 18O enrichments in CO2 as the O2/CO2 mixing ratio decreases found in previous experiments. Kinetics modeling shows that expected changes in the non-mass-dependent KIEs in ozone formation as O2/CO2 decreases cannot explain the O2/CO2 dependence of the non-mass-dependent enrichments in CO2, so a number of different potential chemical mechanisms with non-mass-dependent isotope effects were tested using the model. Of the mechanisms tested, only inclusion of non-thermal rate coefficients for the reactions of 16O(1D), 17O(1D), and 18O(1D) with O2, CO2, and O3 led to any significant decrease in the non-mass-dependent isotopic composition of CO2 as the O2/CO2 mixing ratio is decreased in the model. These non-thermal rate coefficients were derived from non-thermal kinetic energy distributions for 16O(1D), 17O(1D), and 18O(1D) that were calculated using the hard sphere approximation for collisional energy transfer between O(1D) and O2 and between O(1D) and CO2 and the initial energy distributions from O3 photolysis. While the inclusion of the non-thermal rate coefficients in the model produced an O2/CO2 mixing ratio dependence that is still approximately 5 times smaller than the experimentally observed O2/CO2 mixing ratio dependence (i.e.-5 / instead of -50 / from high to low O2/CO2), that the non-thermal reactions involving 16O(1D), 17O(1D), and 18O(1D) could produce non-mass-dependent isotopic compositions even though the corresponding thermal reactions are mass-dependent is novel and, to our knowledge, has not been explored thoroughly in any previous work. Because of the role that collisional energy plays in the isotope exchange between O(1D) and CO2, I also conducted measurements of the isotopic composition of O3 formed in different bath gases, M, to test how the efficiency of collisional energy transfer between O3* and M in ozone formation affects the non-mass-dependent isotopic composition of the resulting O3. New measurements and kinetics modeling of the isotopic composition of O3 formed in an air-like mixture of O2/N2 show statistically significant differences between the non-mass-dependent isotopic composition of O3 formed in pure O2 and in an air-like mixture of O2 and N2. Using a kinetics model, I explore possible origins for these differences in in these experiments and in experiments involving O3 photolysis or O3 formation in SF6. The combined results comparing the model results with the measurements suggest that mass-dependent KIEs in the O2(1[Sigma]) + O3 reaction can likely be ruled out and that the radical complex mechanism for O3 formation (as opposed to the energy transfer mechanism) may indeed play a role in generating the differences in the isotopic composition of O3 formed in different bath gases.
Download or read book The Non mass dependent Oxygen Isotope Effect in the Formation of Ozone from Molecular Discharge written by John E. Heidenreich and published by . This book was released on 1985 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Anomalous Oxygen Isotopic Composition of Atmospheric CO2 and Applications to the Carbon Cycle and Stratospheric Chemistry and Transport written by Katherine Jean Hoag and published by . This book was released on 2007 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of the Triple Oxygen Isotopic Composition of Ozone and Carbon Dioxide Through Experiments and Photochemical Modeling written by Amanda Susan Cole and published by . This book was released on 2006 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Both O3 and CO2 in the stratosphere have unusual isotopic signatures in that they are more enriched in 17O than is expected based on their enrichments in 18O and the usual "mass-dependent" relationship between 17O and 18O. This 17O isotope anomaly in O3 is due to non-mass-dependent isotope effects in O3 formation, while the 17O isotope anomaly in CO2 is thought to arise, at least in part, from ultraviolet photolysis of anomalously enriched O3, followed by isotope exchange between the resulting O(1D) and CO2. However, efforts to quantify the transfer of the isotopic signature from O3 to CO2 have so far been unsuccessful. Furthermore, previous laboratory experiments have been interpreted to indicate that there may be additional non-mass-dependent isotope effects both in O 3 photolysis and in the CO2+O(1D) isotope exchange reaction. To address these issues, a photochemical kinetics model was developed to simulate all isotope-specific reactions involved in the isotope transfer. Using this model to simulate earlier O3 photolysis experiments revealed that non-mass-dependent isotope effects in O3 photolysis are not required to reproduce the experimental data, nor are recent theoretical calculations inconsistent with the laboratory results as they previously appeared to be. The model was then modified to include CO2 and used to test the sensitivity of the CO2 isotopic composition to isotope effects in underlying reactions. The predictions of this model were tested by performing a series of laboratory photochemistry experiments in which the isotopic composition of CO2 in a mixture with O2 was directly measured after irradiation with UV light. The results show that the reaction scheme in the model successfully describes the chemical origin of the 17O isotope anomaly in CO2, implying that no non-mass-dependent isotope effects exist in CO2+O(1D), O3 photolysis, or any other reaction besides O3 formation. These findings may lead to a deeper understanding of the chemical physics of non-mass-dependent isotope effects in general. In addition, measurements of the anomaly in CO 2 in the atmosphere and in O2 in ice cores can now be more confidently used as tracers of stratospheric ozone chemistry and transport and of biospheric productivity on annual and millennial timescales.
Download or read book Symmetry Specific Study of Ozone Isotopomer Formation written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The unusual isotope effect in the formation of the ozone molecule is not yet understood, even 25 years after its discovery. Furthermore, the experimental database is still unsatisfactory, particularly with regard to application of the heavy oxygen from ozone as an atmospheric tracer. To close a gap in the existing record, a high-resolution diode laser based absorption spectrometer was improved, essentially by the use of a gold-coated astigmatic mirror multipass cell and a calibrated confocal Fabry-Perot etalon. All atmospherically relevant, i.e. the simply 17O or 18O substituted ozone isotopomers could thereby be quantified. Precision in the measurement of the isotope abundance was improved to 0.3%. Systematic errors in earlier investigations were identified and minimized in the present measurements. Relative to the reaction 16O + 16O16O -> 16O16O16O, the rate coefficients of the channels 16O + 16O17O -> 16O16O17O and 16O + 17O16O -> 16O17O16O were determined to be 1.292 " 0.019 and 1.005 " 0.010, and those of the channels 16O + 16O18O -> 16O16O18O and 16O + 18O16O -> 16O18O16O were found to be 1.426 " 0.034 and 1.007 " 0.013. Thus, the direct connection between the rate of ozone formation and the enthalpy of the isotope exchange reaction is confirmed. Contrary to earlier assumptions, the analysis of a sample from a laboratory simulation further shows that the isotope transfer from ozone into carbon dioxide does not exhibit an isotope anomaly, at least under laboratory conditions. This apparently confirms the unique character of the ozone molecule.
Download or read book The chemistry of ozone in irradiated co2 and o2 mixtures written by D. R. Mccracken and published by . This book was released on 1996 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The btf-105 experiment in the blowdown test facility is one of a series of experiments sponsored by the candu owners group (cog) to determine the release, transport and deposition of fission products from nuclear fuel under high-temperature transient conditions. the btf-105 experiment has been broken up into two tests: btf-105a and btf-105b. the btf-105a test is a precursor to the btf-105b test, which will generate fission product release data used to benchmark candu safety analysis codes. the btf-105a test will be used to assess instrumentation and procedures to be used during btf-105b, and to generate correlations between fuel sheath and fuel centreline temperatures. fission product release and transport data will also be obtained from low burnup fuel. the btf-105a test consists of a fuel stringer containing a single unirradiated instrumented zircaloy-clad uo2 fuel element. the assembly will be irradiated at a linear power of 50 kw/m for 10 days to establish an inventory of fission products in the fuel. following the soak irradiation, the stringer will be subjected to a coolant blowdown where the volume average temperature of the uo2 will rise to and be maintained at about 1600-1800 degrees c for about 10 minutes. the fuel element is predicted to fail during the ramp up to this temperature due to complete oxidation of the sheath. fission products released during the transient will be monitored by gamma spectrometers. following the test, the fuel stringer will be removed from the reactor and destructively examined in the crl hot cells. grab samples from inside the test section will also be removed and analyzed for fission products. this report presents an overall plan for the activities to be completed before, during and after the btf-105a blowdown test.
Download or read book Oxide Surfaces written by and published by Elsevier. This book was released on 2001-05-21 with total page 677 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book is a multi-author survey (in 15 chapters) of the current state of knowledge and recent developments in our understanding of oxide surfaces. The author list includes most of the acknowledged world experts in this field. The material covered includes fundamental theory and experimental studies of the geometrical, vibrational and electronic structure of such surfaces, but with a special emphasis on the chemical properties and associated reactivity. The main focus is on metal oxides but coverage extends from 'simple' rocksalt materials such as MgO through to complex transition metal oxides with different valencies.
Download or read book Standard Methods for the Examination of Water and Wastewater written by American Public Health Association and published by . This book was released on 1981 with total page 1254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stratospheric Ozone Depletion and Climate Change written by Rolf Müller (physicien.) and published by Royal Society of Chemistry. This book was released on 2012 with total page 347 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, several new concepts have emerged in the field of stratospheric ozone depletion, creating a need for a concise in-depth publication covering the ozone-climate issue. This monograph fills that void in the literature and gives detailed treatment of recent advances in the field of stratospheric ozone depletion. It puts particular emphasis on the coupling between changes in the ozone layer and atmospheric change caused by a changing climate. The book, written by leading experts in the field, brings the reader the most recent research in this area and fills the gap between advanced textbooks and assessments.
Download or read book Bulletin of the Atomic Scientists written by and published by . This book was released on 1970-12 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Bulletin of the Atomic Scientists is the premier public resource on scientific and technological developments that impact global security. Founded by Manhattan Project Scientists, the Bulletin's iconic "Doomsday Clock" stimulates solutions for a safer world.
Download or read book The Potential Effects of Global Climate Change on the United States written by and published by . This book was released on 1989 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Decade to Century Scale Climate Variability and Change written by National Research Council and published by National Academies Press. This book was released on 1998-12-24 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: Society today may be more vulnerable to global-scale, long-term, climate change than ever before. Even without any human influence, past records show that climate can be expected to continue to undergo considerable change over decades to centuries. Measures for adaption and mitigation will call for policy decisions based on a sound scientific foundation. Better understanding and prediction of climate variations can be achieved most efficiently through a nationally recognized "dec-cen" science plan. This book articulates the scientific issues that must be addressed to advance us efficiently toward that understanding and outlines the data collection and modeling needed.
Download or read book Principles of Environmental Physics written by John Monteith and published by Butterworth-Heinemann. This book was released on 1990-02-15 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thoroughly revised and up-dated edition of a highly successful textbook.
Download or read book Effects of Changes in Stratospheric Ozone and Global Climate written by United Nations Environment Programme and published by . This book was released on 1986 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ceramic Abstracts written by and published by . This book was released on 1969 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Non Thermal Plasma Techniques for Pollution Control written by Bernie M. Penetrante and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acid rain, global warming, ozone depletion, and smog are preeminent environmental problems facing the world today. Non-thermal plasma techniques offer an innovative approach to the solution of some of these problems. There are many types of non-thermal plasma devices that have been developed for environmental applications. The potential of these devices for the destruction of pollutants or toxic molecules has already been demonstrated in many contexts, such as nitrogen oxides (NOX) and sulfur dioxide (SO2) in flue gases, heavy metals and volatile organic compounds (VOCs) in industrial effluents, and chemical agents such as nerve gases. This book contains a comprehensive account of the latest developments in non-thermal plasma devices and their applications to the disposal of a wide variety of gaseous pollutants.
