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  • 1
    Electronic Resource
    Electronic Resource
    Field study of the emissions of methyl chloride and other halocarbons from biomass burning in Western Africa (1995)
    Springer
    Journal of atmospheric chemistry 22 (1995), S. 67-80 
    Details
    ISSN: 1573-0662
    Keywords: biomass burning ; halocarbons ; hydrocarbons ; methylchloride ; emission ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A field study of trace gas emissions from biomass burning in Equatorial Africa gave methyl chloride emission ratios of 4.3×10−5±0.8×10−5 mol CH3Cl/mol CO2. Based on the global emission rates for CO2 from biomass burning we estimate a range of 226−904×109 g/y as global emission rate with a best estimate of 515×109 g/y. This is somewhat lower than a previous estimate which has been based on laboratory studies. Nevertheless, our emission rate estimates correspond to 10–40% of the global turnover of methyl chloride and thus support the importance of biomass burning as methyl chloride source. The emission ratios for other halocarbons (CH2Cl2, CHCl3, CCl4, CH3CCl3, C2HCl3, C2Cl4, F-113) are lower. In general there seems to be a substantial decrease with increasing complexity of the compounds and number of halogen atoms. For dichloromethane biomass burning still contributes significantly to the total global budget and in the Southern Hemisphere biomass burning is probably the most important source for atmospheric dichloromethane. For the global budgets of other halocarbons biomass burning is of very limited relevance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00708182
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  • 2
    Electronic Resource
    Electronic Resource
    Methane, carbon monoxide and light non-methane hydrocarbon emissions from African savanna burnings during the FOS/DECAFE experiment (1995)
    Springer
    Journal of atmospheric chemistry 22 (1995), S. 149-162 
    Details
    ISSN: 1573-0662
    Keywords: biomass burning ; hydrocarbons ; methane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Atmospheric samples from savanna burnings were collected in the Ivory Coast during two campaigns in January 1989 and January 1991. About 30 nonmethane hydrocarbons from C2 to C6, carbon monoxide, carbon dioxide and methane were measured from the background and also at various distances from the burning. Concentrations in the fire plume reached ppmv levels for C2-C4 hydrocarbons, and 5300, 500 and 93 ppmv for CO2, CO and CH4 respectively. The excess in the mixing ratios of these gases above their background level is used to derive emission factors relative to CO and CO2. For the samples collected immediately in the fire plume, a differentiation between high and low combustion efficiency conditions is made by considering the CO/CO2 ratio. Ethene (C2H4), acetylene (C2H2), ethane (C2H6) and propene (C3H6) are the major NMHC produced in the flaming stage, whereas a different pattern with an increasing contribution of alkanes is observed in samples typical of post flaming processes. A strong correlation between methane and carbon monoxide suggests that these compounds are produced during the same stage of the combustion. In samples collected at a distance from the fire and integrated over a period of 30 minutes, the composition is very similar to that of flaming. ΔNMHC/ΔCO2 is of the order of 0.7%, ΔCH4/ΔCO2 of the order of 0.4% and ΔCO/ΔCO2 of the order of 6.3%. From this study, a global production by African savanna fires is derived: 65 Tg of CO-C, 4.2 Tg of CH4-C and 6.7 Tg of NMHC-C. Whereas acetylene can be used as a conservative tracer of the fire plumes, only ethene, propene and butenes can be considered in terms of their direct photochemical impact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00708186
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  • 3
    Electronic Resource
    Electronic Resource
    Light hydrocarbons in the surface water of the mid-Atlantic (1992)
    Springer
    Journal of atmospheric chemistry 15 (1992), S. 235-251 
    Details
    ISSN: 1573-0662
    Keywords: Hydrocarbons ; sea-water emissions ; hydrocarbon budgets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a cruise of RV Polarstern over the Atlantic in September/October 1988, C2−C4 hydrocarbons were measured in surface sea water. The ship passed through three different ocean regions divided by divergences at 8° N and 3° S. Hydrocarbon concentrations differed considerably in these regions. The highest values were obtained for ethene with mean concentrations of 246 pMol/l between 35° N and 8° N, 165 pMol/l between 8° N and 3° S, and 63 pMol/l between 3° S and 30° S. Low values were found for i- and n-butane and acetylene between 32 pMol/l and 1 pMol/l. The alkene concentrations were in general higher than the concentrations of their saturated homologs. Concentrations decreased with increasing carbon numbers. The various alkenes were well correlated with one another as were the various alkanes. Oceanic emission rates of the light hydrocarbons were calculated from their sea water concentrations using an ocean atmosphere exchange model. The averaged fluxes ranged from about 108 molec cm-2 s-1 for the alkenes and ethane to less than 107 molec cm-2 s-1 for the C4 alkanes. Acetylene emissions were below 3×106 molec cm-2 s-1. Based upon these rates budget estimates of NMHC in the ocean surface layer were made with a simple model considering production and destruction processes in the water. The emissions to the atmosphere appear to be the dominant loss process between 35° N and 8° N, whereas destruction in the water seems to be dominant in the latitude ranges 8° N-3° S and 3° S-30° S.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115396
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  • 4
    Electronic Resource
    Electronic Resource
    The distribution of light nonmethane hydrocarbons over the mid-Atlantic: Results of the Polarstern cruise ANT VII/1 (1992)
    Springer
    Journal of atmospheric chemistry 15 (1992), S. 215-234 
    Details
    ISSN: 1573-0662
    Keywords: Hydrocarbons ; carbon monoxide ; marine atmosphere ; Atlantic ; hydrocarbon budgets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During the cruise ANT VII/1 (September/October 1988) of the German research vessel Polarstern the latitudinal distributions of several nonmethane hydrocarbons were measured over the Atlantic between 45°N and 30°S by in-situ gas chromatography. On the average, the highest mixing ratios of ethane, propane, i- and n-butane, ethene and acetylene were observed in the Northern Hemisphere around 40° N and just north of the intertropical convergence zone, respectively. South of the equator, a bulge in the mixing ratios of ethane and acetylene was observed indicating aged biomass burning emissions. This observation coincided with enhanced tropospheric ozone found in this region at this season. On the average ethane and acetylene mixing ratios were around 500 and 100 ppt, respectively, whereas the levels of the other NMHC were in the range of some ppt up to 100 ppt. compared with the results of the cruise ANT V/5 (March/April, 1987), the ethane mixing ratios in September/October proved to be a factor of 3 lower in the Northern Hemisphere and a factor of 2 higher in the Southern Hemisphere, probably due to seasonal effects. Possible causes are the higher OH radical concentrations in summer, which result in a faster removal of ethane or stronger emission from biomass burning which also peaks in the dry season. The relative pattern of the hydrocarbons just north of the ITCZ was very similar for both measurement series. In this region, the NMHC were advected by long-range transport from the continent, whereas generally the ocean itself acts as a major NMHC source. This is supported by the results of a balance calculation between oceanic emissions and atmospheric removal rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115395
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