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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Cold plasma processing of local planetary ores for oxygen and metallurgically important metals

The utilization of a cold plasma in chlorination processing is described. Essential equipment and instruments were received, the experimental apparatus assembled and tested, and preliminary experiments conducted. The results of the latter lend support to the original hypothesis: a cold plasma can both significantly enhance and bias chemical reactions. In two separate experiments, a cold plasma was used to reduce TiCl4 vapor and chlorinate ilmenite. The latter, reacted in an argon-chlorine plasma, yielded oxygen. The former experiment reveals that chlorine can be recovered as HCl vapor from metal chlorides in a hydrogen plasma. Furthermore, the success of the hydrogen experiments has lead to an analysis of the feasibility of direct hydrogen reduction of metal oxides in a cold plasma. That process would produce water vapor and numerous metal by-products.

Lynch, D. C.↗
NASA NTRS1991

The Cl-36 in the stratosphere

Initial measurements of the cosmogenic radionuclide, Cl-36, in the lower stratosphere were made by accelerator mass spectrometry. Samples were obtained using the large volume LASL air sampling pods on a NASA WB-57F aircraft. Untreated (for collection of particulates only) and tetrabutyl ammonium hydroxide treated (for collection of particulates and HCl) IPC-1478 filters were flown on three flights in the lower stratosphere. Chlorine (Cl) and Cl compounds are important trace constituents for stratospheric chemistry, in particular with respect to O3 destruction. Stratospheric Cl chemistry has recently received increased attention with the observation of strong O3 depletion in the Antarctic winter vortex and in the weaker and more complex Arctic winter vortices. Cosmogenic (Cl-36) is produced by spallation reactions from Ar mainly in the stratosphere, and has had several applications as a geochemical tracer. The large amounts of Cl-36 introduced by nuclear weapon testing have been removed from the stratosphere by now, and measurements in the stratosphere to obtain cosmogenic production rates and concentration distributions is now possible. The use of cosmogenic Cl-36 as a tracer for stratospheric Cl chemistry and for stratospheric/tropospheric exchange processes is investigated. A first attempt to determine stratospheric and tropospheric production rates, the partitioning of Cl-36 among particulate and gaseous Cl compounds, and the respective inventories and removal rates is being made. Results from a flight at 13.7 km, 30-33 degrees N, 97-107 degrees W, and from a second flight at 17.7 km, 43-45-36 degrees N, 92-94 degrees W, for the untreated and treated filters respectively are presented.

Deck, Bruce↗
NASA NTRS1991

Crystallization kinetics of a lithia-silica glass - Effect of sample characteristics and thermal analysis measurement techniques

DTA and both isothermal and nonisothermal DSC techniques are presently used to investigate the crystallization kinetics of a 40 (mol) percent Li2O-60 percent SiO2 glass as a function of glass powder particle size, the use of either alumina or Pt as the crucible material, the use of N, O, or Ar atmospheres, and surface pretreatments of the glass powder with deionized water, HCl, or HF. Neither the furnace atmosphere nor the crucible material had a significant effect on activation energy, frequency factor, or Avrami exponent. Washings of the glass with the three different fluids decreased the crystallization temperature by 25 to 30 C.

Ray, Chandra S.↗
NASA NTRS1991

In situ measurements of midlatitude ClO in winter

In situ measurements of ClO in the winter lower stratosphere are presented for six flights of the NASA ER-2 aircraft from 38 deg N to 61 deg N. Enhanced abundances, increasing in severity with date, were observed below 20 km, where HCl and ClONO2 dominate the inorganic chlorine budget. The greatest mixing ratios, over 150 pptv, were encountered on February 20 and 21, 1989, as the vortex experienced a major warming. Although the timing of these ClO enhancements and the evidence that vortex air can reach midlatitudes suggest that heterogeneous conversion of chlorine compounds within the vortex influences chemistry at midlatitudes, the enhacements observed early in the winter could have been caused by unknown chemistry occurring outside the vortex. In either case, photochemical loss of ozone due to catalytic reactions involving ClO at these mixing ratios may be responsible in part for the ozone decreases observed at high latitudes in the Northern Hemisphere.

Toohey, D. W.↗
NASA NTRS1991

A 200 MHz surface acoustic wave resonator mass microbalance

The development of a 200 MHz SAW instrument based on an SAW resonator instead of a conventional delay line is reported. The instrument is small, compact, and uses two separate 200 MHz resonataor crystals which operate in the dual difference mode. The difference frequency stability is better than 5 x 10 to the -9th (+ or - 1 Hz) which is comparable to a 10 MHz bulk crystal and at least an order of magnitude better than other commercially available SAW delay lines that operate at comparable frequencies. The mass sensitivity is about 9 x 10 to the 10th Hz sq cm/g. Response to temperature change is found to be about 20 Hz/C from -30 C to 30 C. Response to pressure is found to be linear from 760 to 415 Torr at 3 Hz/Torr. Detection limits for HCl vapors were determined to be in the low ppb range using an SAW resonator coated with triethanolamine.

Bowers, W. D.↗
NASA NTRS1991

Comment on 'The Space Shuttle's impact on the stratosphere' by Michael J. Prather et al

Prather et al. (1990) argued that no local hole in column ozone could occur above the launch site of the Space Shuttle because (1) the HCl in the exhaust would require some time to be converted into more catalytically active forms, (2) the Shuttle trajectory is not vertically aligned, and (3) the corridor of exhaust gases is laterally spread over more than 1000 km in a day. In contradiction to these arguments, it is maintained here that assumption (1) is inconsistent with the empirical evidence, rendering (2) and (3) insufficient to maintain the claim that no local hole in column ozone could occur. In a reply, ozone image data from the TOMS on Nimbus 7 is used to support the argument of Prather et al.

Aftergood, Steven↗
NASA NTRS1991

Condensational growth and trace species scavenging in stratospheric sulfuric acid/water aerosol droplets

Stratospheric aerosols play a significant role in the environment. The composition of aerosols is believed to be a liquid solution of sulfuric acid and water with numerous trace species. Of these trace species, ozone in particular was recognized as being very important in its role of shielding the environment from harmful ultraviolet radiation. Also among the trace species are HCl and ClONO2, the so called chlorine reservoir species and various oxides of nitrogen. The quantity of stratospheric aerosol and its particle size distribution determines, to a large degree, the chemistry present in the stratosphere. Aerosols experience 3 types of growth: nucleation, condensation, and coagulation. The application of condensation investigations to the specific problem of stratospheric aerosols is discussed.

Tompson, Robert V., Jr.↗
NASA NTRS1990

Far infrared balloon-based limb emission measurements of HO(sub x) gases in the middle atmosphere

The aim of the measurements is to obtain vertical mixing of profiles of hydrogen and halogen trace gases and to study the related processes of diurnal change, OH/HO2 ratio, and HO sub x total budget involved in stratospheric ozone. The species to be measured in the first planned 1990 flight of this new series include OH, H2O2, HO2, HOCl, HBr, HCl, HF, H2O, HDO, O3, and isotopic O3. Recent analyses have been completed for the retrieval of the OH concentration profile and the first measurement of the HBr column concentration.

Russell, James M., III↗
NASA NTRS1990

Tunable far infrared studies of molecular parameters in support of stratospheric measurements

The purpose of this research is to make precise, fully line-resolved measurements of molecular parameters that are necessary for the analysis of spectra obtained in far infrared field measurement programs. These measurements make it possible to accurately analyze the data from field measurements to obtain atmospheric concentration profiles of key trace gases involved in the ozone chemistry. The research objectives include: measurements of pressure broadening of molecular lines of OH, O2, O3, HCl, and H2O, their temperature dependence, and, when possible, the pressure-induced frequency shifts of the lines; measurements of line positions of radical species, such as HO2.

Chance, K. V.↗
NASA NTRS1990

Natural chlorine and fluorine in the atmosphere, water and precipitation

The geochemical cycles of chlorine and fluorine are surveyed and summarized as framework for the understanding of the global natural abundances of these species in the atmosphere, water, and precipitation. In the cycles the fluxes into and out of the atmosphere can be balanced within the limits of our knowledge of the natural sources and sinks. Sea salt from the ocean surfaces represent the predominant portion of the source of chlorine. It is also an important source of atmospheric fluorine, but volcanoes are likely to be more important fluorine sources. Dry deposition of sea salt returns about 85 percent of the salt released there. Precipitation removes the remainder. Most of the sea salt materials are considered to be cyclic, moving through sea spray over the oceans and either directly back to the oceans or deposited dry and in precipitation on land, whence it runs off into rivers and streams and returns to the oceans. Most of the natural chlorine in the atmosphere is in the form of particulate chloride ion with lesser amounts as gaseous inorganic chloride and methyl chloride vapor. Fluorine is emitted from volcanoes primarily as HF. It is possible that HF may be released directly form the ocean surface but this has not been confirmed by observation. HCl and most likely HF gases are released into the atmosphere by sea salt aerosols. The mechanism for the release is likely to be the provision of protons from the so-called excess sulfate and HNO3. Sea salt aerosol contains fluorine as F(-), MgF(+), CaF(+), and NaF. The concentrations of the various species of chlorine and fluorine that characterize primarily natural, unpolluted atmospheres are summarized in tables and are discussed in relation to their fluxes through the geochemical cycle.

Friend, James P.↗
NASA NTRS1989

Trends in stratospheric minor constituents

Photochemical models predict that increasing source gas concentrations are also expected to lead to changes in the concentrations of both catalytically active radical species (such as NO2, ClO, and OH) and inactive reservoir species (such as HNO3, HCl, and H2O). For simplicity, we will refer to all these as trace species. Those species that are expected to have increasing concentration levels are investigated. Additionally, the trace species concentration levels are monitored for unexpected changes on the basis of the measure increase in source gases. Carrying out these investigations is difficult due to the limited data base of measurements of stratospheric trace species. In situ measurements are made only infrequently, and there are few satelliteborne measurements, most over a time space insufficient for trend determination. Instead, ground-based measurements of column content must be used for many species, and interpretation is complicated by contributions from the troposphere or mesosphere or both. In this chapter, we examine existing measurements as published or tabulated.

Stolarski, R. S.↗
NASA NTRS1991

Thermodynamic models of the chemistry of lunar volcanic gases

Thermodynamic models and mass-balance arguments are used to constrain the chemistry of lunar volcanic gases. The results predict that lunar gases were dominated by reduced C and S gases such as CO, COS, CS2, S2. The more oxidized gases CO2 and SO2 were also important, but only in limited temperature ranges. Gases such as Cl2, CCl4, and CF4 were more abundant than HF and HCl, which were the two major H compounds in the lunar gases. Chlorides and fluorides were important species for transporting many volatile and ore-forming metals, and the implications for fractionating and concentrating metals into lunar ore-deposits merit further study.

Fegley, Bruce, Jr.↗
NASA NTRS1992

The molecular core in G34.3 + 0.2 - Millimeter interferometric observations of HCO(+), H(C-13)N, H(C-15)N, and SO

This study presents high-resolution observations of the molecular core in the star-forming region G34.3 + 0.2. Maps at 6-arcsec resolution of emission and absorption of the J = 1 - 0 transitions of HCO(+), H (C-13)N, H(C-15)N, and of the 2(2) - 1(1) transition of SO were obtained in addition to a map of the 3.4-mm continuum emission from the compact H II component. The HCL(+) emission toward G34.3 + 0.2 traces a warm molecular core about 0.9 pc in size. Emission from H (C-13)N is detected over about 0.3 pc. The cometary H II region lies near the edge of the molecular core. The blueshift of the radio recombination lines with respect to the molecular emission suggests that gas from the H II region is accelerated in a champagne flow caused by a steep gradient in the ambient gas density.

Carral, Patricia↗
NASA NTRS1992

Photochemical partitioning of the reactive nitrogen and chlorine reservoirs in the high-latitude stratosphere

The correlated set of measurements in the lower stratosphere from polar missions of the NASA ER-2 is used to derive partitioning of the major components of the reactive nitrogen and inorganic chlorine reservoirs. The results provide a consistent method for comparing distributions, and hence the controlling processes, between different areas of the near-polar regions. Clear evidence of the effects of heterogeneous processes in the atmosphere is found. Values for NO2, ClONO2, N2O5, and Cl2O2 are derived in a simplified steady-state model based on in situ NO, ClO, O3, temperature, and pressure measurements, laboratory-measured reaction rates; and modeled photodissociation rates. Values for the reservoir totals are independently derived from measurements of N2O, organic chlorine, and total reactive nitrogen. The relative abundances of the measured and derived species within the reservoirs are calculated, and the longer-lived species HCl and HNO3 are estimated as the residuals of their respective reservoirs.

Kawa, S. R.↗
NASA NTRS1992

Composition measurements of the 1989 Arctic winter stratosphere by airborne infrared solar absorption spectroscopy

The paper reports simultaneous measurements of the stratospheric burdens of H2O, HDO, OCS, CO2, O3, N2O, CO, CH4, CF2Cl2, CFCl3, CHF2Cl, C2H6, HCN, NO, NO2, HNO3, ClNO3, HOCl, HCl, and HF made by the JPL MkIV interferometer on board the NASA DC-8 aircraft during January and early February 1989 as part of the Airborne Arctic Stratosphere Experiment. Data were obtained on 11 flights at altitudes of up to 12 km over a geographic region covering the NE Atlantic Ocean, Iceland, and Greenland. Analyses of the chemically active gases reveal highly perturbed conditions within the vortex. The ClNO3 abundance was chemically enhanced near the edge of the vortex but was then depleted inside. NO2 was severely depleted inside the vortex. In contrast to Antarctica, H2O and HNO3 were both more abundant inside the vortex than outside. It is suggested that although the Arctic vortex did not get cold enough to produce any dehydration, or as vertically extensive denitrification as occurred in Antarctica, nevertheless, enough heterogeneous chemistry occurred to convert over 90 percent of the inorganic chlorine to active forms in the 14- to 27-km altitude range by early February 1989.

Toon, G. C.↗
NASA NTRS1992

Episodic total ozone minima and associated effects on heterogeneous chemistry and lower stratospheric transport

Three-dimensional model simulations are used to describe the January 31, 1989 ozone minihole over Stavanger, Norway. This minihole is typical of many transient events in the lower stratosphere that arise because of cyclonic-scale disturbances in the troposphere. Although the ozone reduction is a short-lived reversible dynamical event, through heterogeneous chemical processes there can be a significant transfer of chlorine from reservoir molecules to active radicals. This chemically perturbed air is defined as processed air, and it is found that a single event can produce enough processed air to reduce the HCl in the entire polar vortex. Chemical processing on clouds associated with transient events is shown to be a major source of processed air in the polar vortex in December before background temperatures are cold enough for more uniform heterogeneous conversion.

Rood, Richard B.↗
NASA NTRS1992

Schroedinger's radial equation - Solution by extrapolation

A high-accuracy numerical method for the solution of a 1D Schroedinger equation that is suitable for a diatomic molecule, obtained by combining a finite-difference method with iterative extrapolation to the limit, is presently shown to have several advantages over more conventional methods. Initial guesses for the term values are obviated, and implementation of the algorithm is straightforward. The method is both less sensitive to round-off error, and faster than conventional methods for equivalent accuracy. These advantages are illustrated through the solution of Schroedinger's equation for a Morse potential function suited for HCl and a numerically derived Rydberg-Klein-Rees potential function for the X 1Sigma(+) state of CO.

Goorvitch, D.↗
NASA NTRS1992

The 1985 chlorine and fluorine inventories in the stratosphere based on ATMOS observations at 30 deg North latitude

Results are presented of an investigation of the Cl and F inventories derived from the concentrations of eleven Cl- and F-bearing organic and inorganic species throughout the atmosphere, based on observations with the Atmospheric Trace Molecule Spectroscopy instrument aboard the Space Shuttle during the Spacelab 3 mission of April 29 to May 6, 1985. It was found that, in April-May 1985, near 30 deg N, the mean total stratospheric concentrations of Cl and F were 2.58 +/-0.10 ppbv and 1.15 +/-0.12 ppbv, respectively. Partitioning among the source, sink, and reservoir species was consistent with the conservation of the F and Cl budgets throughout the stratosphere. It is shown that the budgets of Cl and F above about 45 km altitude can be determined accurately by measuring only HCl, HF, and CF4 and provide a straightforward timely reference point for future inventories and trends evaluations.

Zander, R.↗