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  • 1
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    Possible atmospheric lifetimes and chemical reaction mechanisms for selected HCFCs, HFCs, CH3CCl3, and their degradation products against dissolution and/or degradation in seawater and cloudwater (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: For a wide variety of atmospheric species including CO2, HNO3, and SO2, dissolution in seawater or cloudwater followed by hydrolysis or chemical reaction represents a primary pathway for removal from the atmosphere. In order to determine if this mechanism can also remove significant amounts of atmospheric chlorofluorocarbons (HCFC's), fluorocarbons (HFC's), and their degradation products, an investigation was undertaken as part of the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS). In this investigation, the rates at which CHCl2CF3 (HCFC-123), CCl2FCH3 (HCFC-141b), CClF2CH3 (HCFC-142b), CHClF2 (HCFC-22), CHClFCF3 (HCFC-124) CH2FCF3 (HFC-134a) CHF2CH3 (HFC-152a), CHF2CF3 (HFC-125), and CH3CCl3 can be dissolved in the oceans and in cloudwater were estimated from the species' thermodynamic and chemical properties using simple mathematical formulations to simulate the transfer of gases from the atmosphere to the ocean or cloudwater. The ability of cloudwater and rainwater to remove gas phase degradation products of these compounds was also considered as was the aqueous phase chemistry of the degradation products. The results of this investigation are described.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA, Washington, Scientific Assessment of Stratospheric Ozone: 1989, Volume 2. Appendix: AFEAS Report; p 271-295
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  • 2
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    The chemistry and transport of methane and carbon monoxide in the troposphere (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The present understanding of the physical and chemical behavior of methane, carbon monoxide and the chemical species involved in the conversion of CH4 to CO in the troposphere is reviewed. Following a brief summary of CO and CH4 emission and reactions in urban areas, attention is given to measurements of the spatial and temporal distributions of CO and CH4 in the rural atmosphere, the contribution of the oceans to atmospheric CO and CH4 concentrations, and interactions of CH4 and CO with soils and vegetation. Estimates of the transport of CH4 and CO from the troposphere to the stratosphere are discussed, and photochemical reactions of the constituents are examined. Two- and three-dimensional models for CH4 and CO transport are presented, and possible future variations in atmospheric abundances of the molecules are considered. Finally, present estimates of the global methane and carbon dioxide budgets are summarized, and it is pointed out that, despite the large contribution of anthropogenic sources, the budgets appear to be in balance.
    Keywords: ENVIRONMENT POLLUTION
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  • 3
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    Effects of nonmethane hydrocarbons in the atmosphere (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: An investigation was conducted to determine whether nonmethane hydrocarbons (NMHC) are abundant enough to have a significant impact upon the ambient photochemistry. The vertical distribution of C2H6, C2H2, C3H8, C4H10, and C5H12 in the altitude range from 0 to 40 km was calculated in this connection. A one-dimensional steady state model with coupled photochemistry and vertical transport was employed in the investigation. The calculations imply that measurable quantities of relatively unreactive NMHC, especially C2H6 and C2H2, may be present in the upper troposphere and stratosphere. The results indicate, however, that NMHC are not likely to have a large impact on the background photochemistry of the troposphere, although local effects near source regions are probable. The findings support the current practice of many modelers who neglect NMHC in their calculations.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research; 83; Feb. 20
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  • 4
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    Effect of variable energy input on nitrogen fixation in instantaneous linear discharges (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The reported analysis implies that the number of molecules of NO produced per joule of discharge varies with input energy. The calculations assume a cylindrical symmetry but the results are consistent with equivalent calculations using spherical symmetry. If NO yield does vary with input energy, extrapolation of laboratory experiments using small sparks is not as straightforward as has previously been assumed. Calculated curves for the yield of NO as a function of discharge energy are presented and are compared with experimental values and other theoretical values.
    Keywords: ENVIRONMENT POLLUTION
    Type: Nature; 277; Jan. 11
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  • 5
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    Possible variations in atmospheric methane (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A model coupling photochemistry and vertical transport in the troposphere has been used to investigate the magnitude of possible future perturbations to atmospheric CH4. The response of atmospheric CH4 to an increase in the concentration of CO or to a variation in stratospheric O3 is studied. Both of the above mechanisms, which could be caused by man's activities, arise because a change in the concentration of tropospheric OH will lead to a change in the CH4 abundance. The calculations imply that a perturbation of about 30-40% in atmospheric CH4 could occur if stratospheric O3 were perturbed by 10% or if man-made CO continued to increase. The possible consequences of a CH4 perturbation may entail a perturbation in stratospheric photochemistry or in the thermal balance of the atmosphere.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research; 82; Apr. 20
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  • 6
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    Effect of odd hydrogen on ozone depletion by chlorine reactions (1976)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The present paper discusses how the shape of the ozone layer changes under the influence of injected ClX for several choices of two key HOx reaction rates. The two HOx reactions are: OH + HO2 yields H2O + O2 and O + HO2 yields OH + O2. Results of calculations are presented which show that the two reaction rates determine the stratospheric concentrations of OH and HO2, and that these concentrations regulate the amount by which the stratospheric ozone column can be reduced due to injections of odd chlorine. It is concluded that the amount of ozone reduction by a given mixing ratio of ClX will remain very uncertain until the significance of several possible feedback effects involving HOx in a chlorine-polluted atmosphere are determined and measurements of the reaction rates and HOx concentrations are made at the relevant temperatures.
    Keywords: ENVIRONMENT POLLUTION
    Type: Geophysical Research Letters; 3; Feb. 197
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  • 7
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    Stratospheric ozone - The possible effects of tropospheric-stratospheric feedback (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The existence of tropospheric-stratospheric feedback mechanisms affecting variations in stratospheric ozone indicates the need to model the complete tropospheric-stratospheric system. For instance, a decrease in stratospheric ozone results in increased photolytic destruction of nitrous oxide in the troposphere and thereby reduced production of nitric oxide in the stratosphere. Estimates indicate that this mechanism will result in a recovery in atmospheric ozone of about 6 to 13 percent of the initial perturbation.
    Keywords: ENVIRONMENT POLLUTION
    Type: Science; 190; Dec. 26
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  • 8
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    Sources and sinks of atmospheric N2O and the possible ozone reduction due to industrial fixed nitrogen fertilizers (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The terrestrial and marine nitrogen cycles are examined in an attempt to clarify how the atmospheric content of N2O is controlled. We review available data on the various reservoirs of fixed nitrogen, the transfer rates between the reservoirs, and estimate how the reservoir contents and transfer rates can change under man's influence. It is seen that sources, sinks and lifetime of atmospheric N2O are not understood well. Based on our limited knowledge of the stability of atmospheric N2O we conclude that future growth in the usage of industrial fixed nitrogen fertilizers could cause a 1% to 2% global ozone reduction in the next 50 years. However, centuries from now the ozone layer could be reduced by as much as 10% if soils are the major source of atmospheric N2O.
    Keywords: ENVIRONMENT POLLUTION
    Type: Tellus; 29; June 197
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  • 9
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    Diagnostic studies of the HxOy-NxOy-O3 photochemical system using data from NASA GTE field expeditions (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The research effort supported in part by the subject grant focused on three related topics. Our major effort was concentrated on the analysis of data gathered during GTE field expeditions. Ancillary efforts were directed at: the development and application of a Global Chemical Transport Model for the study of the atmospheric reactive nitrogen budget; the development and application of a one-dimensional, time dependent cloud model for the study of the impact of in-cloud aqueous phase chemistry on the atmospheric sulfur budget; and mechanistic studies of the chemical processes involved in dry deposition of ozone to vegetative surfaces. In the sections below, we briefly summarize the central conclusions of each of these efforts. These discussions are followed by a listing of the papers completed during the granting period and the graduate students supported by funds from the grant. Reprints and preprints of all papers completed with support from the grant are attached as appendices.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA-CR-193672 , NAS 1.26:193672
    Format: application/pdf
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  • 10
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    The effect of anthropogenic carbon monoxide on the methane budget of the troposphere (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Photochemical model calculations indicate that significant perturbations in tropospheric OH, CH4, and related compounds may occur in the coming decades due to increased anthropogenic emissions of CO and NO(x). The magnitude and direction of the perturbation depends on future emission rates of CO and NO(x) and also on the efficiency with which urban NO(x) is transported to the ambient atmosphere. If CO and NO(x) emissions increase at comparable rates, the CO effect on OH will dominate and OH will decrease while CH4 increases. The effects of a variation in tropospheric OH, halocarbons, and other compounds include a perturbation to stratospheric ozone and the atmosphere's thermal equilibrium.
    Keywords: ENVIRONMENT POLLUTION
    Type: In: Joint Conference on Sensing of Environmental Pollutants; Nov 06, 1977 - Nov 11, 1977; New Orleans, LA
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