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  • 1
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    New estimates of nitrous oxide emissions from biomass burning (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The recent discovery of an artifact producing increased levels of N2O in combustion gas samples collected and stored in grab bottles before chemical analysis has resulted in the downgrading of fossil-fuel combustion and the questioning of biomass burning as important sources of N2O. As almost all reported analyses of N2O produced from biomass burning have involved essentially the same collection and analysis protocols as used in the fossil-fuel studies, this source of N2O must also be reexamined. Here, measurements of N2O made over a large prescribed fire using a near real-time in situ measurement technique are reported and compared with measurements of N2O from simultaneously collected grab-bottle samples. The results from 27 small laboratory biomass test fires are also used to help clarify the validity of earlier assessments. It is concluded that biomass burning contributes about seven percent of atmospheric N2O, as opposed to earlier estimates of several times this value.
    Keywords: ENVIRONMENT POLLUTION
    Type: Nature (ISSN 0028-0836); 349; 689-691
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  • 2
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    Nitric acid and ammonia emissions from a mid-latitude prescribed wetlands fire (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The first simultaneous measurements of gaseous nitric acid and ammonia in the smoke plume of a wetlands biomass burn were obtained. The measurements were made using tungsten oxide-coated diffusion denuder tubes from a helicopter during a prescribed burn on November 9, 1987, at the Merritt Island National Wildlife Refuge, located at the NASA John F. Kennedy Space Center, Florida. The mean NH3 and HNO3 mixing ratios measured in the smoke plume were 19 ppbv and 14 ppbv, respectively, both significantly higher than background mixing ratios. Nitric acid correlated well with carbon dioxide produced by the combustion. The mean CO2-normalized emission ratio for HNO3 was found to be 0.00012. Ammonia, however, dit not correlate well with CO2, suggesting a more complex relationship between combustion and production/release of NH3.
    Keywords: ENVIRONMENT POLLUTION
    Type: Geophysical Research Letters (ISSN 0094-8276); 15; 792-795
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  • 3
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    Biospheric-atmospheric coupling on the early Earth (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Theoretical calculations performed with a one-dimensional photochemical model have been performed to assess the biospheric-atmospheric transfer of gases. Ozone reached levels to shield the Earth from biologically lethal solar ultraviolet radiation (220-300 nm) when atmospheric oxygen reached about 1/10 of its present atmospheric level. In the present atmosphere, about 90 percent of atmospheric nitrous oxide is destroyed via solar photolysis in the stratosphere with about 10 percent destroyed via reaction with excited oxygen atoms. The reaction between nitrous oxide and excited oxygen atoms leads to the production of nitric oxide in the stratosphere, which is responsible for about 70 percent of the global destruction of oxygen in the stratosphere. In the oxygen/ozone deficient atmosphere, solar photolysis destroyed about 100 percent of the atmospheric nitrous oxide, relegating the production of nitric oxide via reaction with excited oxygen to zero. Our laboratory and field measurements indicate that atmospheric oxygen promotes the biogenic production of N2O and NO via denitrification and the biogenic production of methane by methanogenesis.
    Keywords: ENVIRONMENT POLLUTION
    Type: NASA, Washington, Fourth Symposium on Chemical Evolution and the Origin and Evolution of Life; p 57
    Format: application/pdf
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  • 4
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    The photochemistry of anthropogenic nonmethane hydrocarbons in the troposphere (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A lumped, nonmethane hydrocarbon (NMHC) chemical mechanism is presently applied to a one-dimensional photochemical model of the troposphere. The profiles of OH, HO2, NO(x), and HNO3, showed only slight changes when NMHC chemistry was added. The integrated column of peroxyacetylnitrate (PAN), when NMHC chemistry was included, comprised 17 percent of the odd nitrogen budget. Advection is noted as an important possible mechanism for the removal of PAN at midlatitudes. The inclusion of such intermediate lifetime species as aldehydes and olefins has both provided additional sources of short-lived NMHC radicals, such as the peroxyacetyl radical that is the radical precursor of PAN, and offered a more detailed description of the concentrations of short-lived species and the overall NMHC chemistry.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; Aug. 20
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  • 5
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    Ammonia and the NOx budget of the troposphere (1982)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Liu et al. (1980) suggested that NOx transported from the stratosphere, as opposed to the anthropogenic source of NOx, may be the dominant source that controls the distribution of NOx in the global troposphere. These ideas require a reinvestigation, and, in particular, an assessment of the role of the oxidation of ammonia as a source of NOx. Attention is given to the results of an ammonia measurement program, in which the vertical distribution of ammonia in the troposphere and lower stratosphere could be studied with the aid of the Infrared Heterodyne Radiometer (IHR), a solar-viewing remote sensor. A one-dimensional photochemical model of the troposphere reported by Levine et al. (1980) was employed to study the chemical and physical processes that control the loss of ammonia in the troposphere. The results of the considered investigation suggest that the oxidation of ammonia may indeed be a significant source of NOx in the troposphere.
    Keywords: ENVIRONMENT POLLUTION
    Type: Symposium on the Composition of the Nonurban Troposphere; May 25, 1982 - May 28, 1982; Williamsburg, VA
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  • 6
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    The chlorine budget of the troposphere (1982)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: It has been hypothesized that chlorine compounds in the stratosphere could photodissociate and release atomic chlorine which catalytically destroys ozone. For an accurate assessment of the possibility of stratospheric ozone depletion, it will be necessary to know the chlorine budget of the entire atmosphere, including the troposphere and the stratosphere. Most chlorine species in the atmosphere are emitted at the surface and diffuse upward. Measurements involving chlorine are reviewed and photochemical calculations are discussed. It is found that between 0.1-1.0 ppbv of inorganic chlorine is present at the surface and about 0.02 ppbv (parts per billion by volume) at the tropopause. Most of the inorganic chlorine is believed to be in the form of HCl, and thus natural in origin. For organic chlorine the corresponding numbers are 1.9 ppbv and 1.7 ppbv, respectively. At the surface approximately 32% of the organic chlorine is natural and 68% anthropogenic.
    Keywords: ENVIRONMENT POLLUTION
    Type: Symposium on the Composition of the Nonurban Troposphere; May 25, 1982 - May 28, 1982; Williamsburg, VA
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  • 7
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    PAN and the NOx budget of the troposphere (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The present investigation has the objective to examine the interaction of NOx with the nonmethane hydrocarbons (NMHCs) photochemistry. Attention is given to the influence of temperature, transport, and hydrocarbon radical reactions on the profiles of peroxyacylnitrates (PANs) and NO2. A lumped NMHC chemical reaction scheme was used in a one-dimensional photochemical model of the global troposphere. Model calculations were performed with various temperature profiles and the corresponding solar zenith angles to examine seasonal variations in the profiles of PAN and NOx. A study of the effects of changing temperature and solar zenith angle on the profiles of PAN and NOx showed that the amount of NO2 tied up in PAN increased as temperature decreased.
    Keywords: ENVIRONMENT POLLUTION
    Type: Symposium on the Composition of the Nonurban Troposphere; May 25, 1982 - May 28, 1982; Williamsburg, VA
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